JP4360867B2 - Thermal analysis method - Google Patents

Description

  The present invention relates to a thermal analysis method for finding a heating condition for heating an object to be heated along a temperature profile that conforms to a predetermined requirement, and a program for determining a procedure for executing the thermal analysis method. More specifically, the present invention heats a circuit board on which electronic components are mounted on applied cream solder, melts the solder, and finds suitable heating conditions for soldering the electronic components to the circuit board. The present invention relates to an analysis method, a program for executing the thermal analysis method, and a computer-readable recording medium on which the program is recorded. The present invention further relates to a heating control device that performs the thermal analysis method, and a heating device including the heating control device.

  When heating an object to be heated using a heating device, the object to be heated is maintained at a predetermined heating temperature for a predetermined time, and the heat resistance limit temperature of the object to be heated is not exceeded. It must be managed appropriately. In addition to maintaining the heated object at a constant temperature, careful heating analysis and heating control are required to heat the heated object according to the temperature profile that meets the requirements including preheating, heating and cooling. Has been.

  As an example, there is reflow heating in which a component such as an electronic component or an optical component is mounted on a circuit formed body such as an electronic circuit substrate (hereinafter referred to as “circuit substrate”) and soldered. Here, generally, solder paste is printed by printing cream solder on a circuit board on which surface-mounted components are mounted, mounting the components on the cream solder, and then transporting them to a reflow heating device to melt the solder. ing. In this reflow heating, preheating is first performed in order to avoid thermal damage of components and circuit boards due to rapid heating. This preheating also has an effect of activating the flux contained in the cream solder such as an antioxidant and improving the quality of the solder joint. Thereafter, the solder is maintained at a temperature equal to or higher than the melting point for a certain time, and after the solder is completely melted, it is solidified and reflow heating is performed to obtain a reliable solder joint.

  Responding to recent environmental protection demands, tin-silver-copper system that does not contain harmful lead, tin-zinc-bismuth system, etc. Lead-free solder tends to be used. However, the lead-free solder generally has a melting point as high as about 220 ° C. as compared with lead-based solder, which has a relatively low melting point of about 190 ° C., and this must be heated to a higher temperature than before when reflowing. Don't be. On the other hand, in order to prevent thermal destruction of electronic parts and the like mounted on the circuit board, it is required that the heat resistance limit temperature (heat resistance guarantee temperature) of each of these parts is not exceeded during reflow heating. For example, in an aluminum electrolytic capacitor, this heat-resistant limit temperature is about 240 ° C. If the heating temperature is too low, soldering of the parts cannot be guaranteed, and conversely if the temperature is too high, thermal destruction of the parts will occur. Therefore, in order to perform highly reliable solder bonding with a reflow device, the solder is heated to a temperature higher than the melting point, and at the same time, the circuit board and the component to be heated do not strictly exceed their respective heat resistance limit temperatures. Temperature management is required. For this reason, the reflow heating conditions including the temperature conditions of the heating source such as hot air and the panel heater, the conveyance speed of the circuit board passing through the heating device, and the like must be appropriately set according to the required degree of the object to be heated. .

  As a heating method used in the heating device, there are a convection type in which hot air from a heat source generated by combustion of electricity or gas or petroleum is blown to the object to be heated, and a radiation type in which far infrared rays are irradiated on the object to be heated. In each heating apparatus such as a heat treatment apparatus, a sintering apparatus, a baking apparatus, a melting apparatus, and an incineration apparatus, an appropriate heating method is adopted according to each application. In particular, when strict temperature control is required for a solder reflow apparatus or the like for the purpose of solder bonding described above, convection heating with relatively easy temperature control tends to be used.

  Conventionally, when setting the reflow conditions, a thermocouple for temperature measurement is attached to at least one location on the circuit board, and the temperature change during heating at this measurement point is measured. And verification was repeated while changing the heating condition of the reflow device successively until a temperature measurement result along a desired temperature profile was obtained at each measurement point, and appropriate reflow conditions were set. When the reflow conditions are changed, a waiting time is required until the temperature of the heating device is stabilized, and this temperature measurement is generally repeated at least about 10 times until an appropriate heating condition is found. For this reason, it takes a long time to set the temperature condition, and the intuition and experience of a skilled worker are required to correct the heating condition based on one measurement result. As a result of this trial and error, even if the heating condition was obtained, it could not be determined whether this was the optimum condition of the heating apparatus, that is, the heating condition that cleared the required condition with a margin.

  Several measures for improving the reflow condition setting process that require such a long man-hour and rely on the intuition and experience of the experienced person have been proposed in the prior art. As an example, a test member with a clear physical property value is heated in a heating device and its temperature change is measured, and the temperature change is calculated using a differential equation with the heating characteristic of the heating device as a parameter. There has been disclosed a method for determining an optimum heating characteristic by repeatedly calculating a value indicating a heating characteristic of a heating device so that a deviation from the value is minimized (see, for example, Patent Document 1).

  As another example, the heating conditions are set for a plurality of heating sources, the object to be heated is heated to detect the temperatures at a plurality of detection points of the object to be heated, and the amount of change in the heating conditions in one heating source The relationship between the detected temperature change at each detection point of the heated object is calculated for each heating source, and the heating source is controlled by calculating the heating conditions for setting the temperature of the object to be heated to the target temperature based on this result. Is disclosed (for example, see Patent Document 2).

  However, in any of the above methods, the physical property value of the object to be heated (or the test member) is required to determine the optimum heating condition and control the heating source. There is a need to. In particular, in recent years, there are many cases where about 100 electronic components are mounted on one printed circuit board. Under such a situation that the switching of the board and the component type is severe, such physical property value input is individually performed for each measurement target of the object to be heated. The time-consuming method requires a great amount of man-hours and is difficult to implement at the site. In addition, when the object to be heated is a mixture or a combination part, it may be difficult to obtain the physical property value itself.

  Further, in the prior art, in a heating apparatus having a plurality of heating zones, the boundary condition temperature and hot air temperature for each heating zone are measured, and the boundary condition temperature is changed by the smallest difference among the differences between the two. A method for adjusting the boundary condition temperature is disclosed (for example, see Patent Document 3). However, according to this method, only the temperature profile is translated and adjusted based on one factor at the boundary of each heating zone, and in particular, a temperature profile or a complex curve in which the peak temperature does not exist at the boundary. It is difficult to obtain a highly accurate heating simulation at each position of the drawn temperature profile. Moreover, since the whole heating apparatus is performed by one temperature control, there exists a problem that the heating condition for every several measurement point is not considered.

  By the way, many types of components mounted on one circuit board have different shapes according to their specifications. In particular, a tall component passes through a position closer to the heating source during transportation, and therefore, the temperature rise is relatively severe at the upper end portion. On the other hand, since the short components are far from the heating source, the temperature rise is somewhat slow, and for example, the part to be soldered on the circuit board is located away from the heating source, so the temperature rise Relatively late. If the heating temperature is raised in order to ensure solder melting, this leads to a risk that the tip portion of the component located at a position higher than the solder joint will be heated first, causing thermal destruction at this portion.

For this reason, in the prior art, a heating source is provided on both the front and back sides of the circuit board, and the circuit board conveyed between them is heated using the heating sources on both the front and back sides, and in particular, the back side where the solder joint is closer. Set the temperature of the heating source on the side (lower side) higher than the temperature of the heating source on the front side (upper side) to accelerate the heating of the solder joints and, in addition, prevent thermal destruction of the tip part of the component A method is known (see, for example, Patent Document 4). If there is a difference in the heating temperature between the front and back surfaces in this way, the reflow condition setting process becomes more complicated, so there is generally no known simulation method for performing this in general. However, it is necessary to input the physical property value of the object to be heated, and the reliability is not always satisfactory.
Japanese Patent Laid-Open No. 2002-45961 JP-A-4-109695 US Pat. No. 6,283,379 JP-A-4-109695

  Therefore, in view of the above-mentioned conventional problems, the present invention does not use the physical property value of the object to be heated, and repeats heating and measurement of the object to be heated by trial and error between the front and back sides of the object to be heated. It is an object of the present invention to provide a thermal analysis method capable of efficiently finding out the heating conditions of the heating device including the case where a temperature difference is provided, a heating device that implements the thermal analysis method, and a heating control device.

  The present invention further includes a computer-readable recording medium capable of implementing the above-described thermal analysis method, a program recorded on the recording medium, a heating control device capable of performing the thermal analysis method, and a heating device. It is intended to provide.

  The present invention calculates the heating characteristics for each measurement position and each measurement point from the data of the heating temperature and heating time including the front and back temperature difference at any measurement position of the heating device, and the temperature of the arbitrary measurement point of the object to be heated. The above-mentioned problem is solved by obtaining a numerical result as one constant, and specifically includes the following contents.

  That is, according to one aspect of the present invention, a heating device including a heating source that heats an object to be heated from the front and back, at least one arbitrary measurement position at different measurement temperatures, a heating time at the measurement position, and a heating target Based on the temperature measurement result at at least one arbitrary measurement point of the object, the heating characteristics including the physical characteristics of the object to be heated and the heating device are numerical values as one constant for each measurement position and each measurement point. The present invention relates to a thermal analysis method characterized by: By using the numerical result, it is possible to simulate a temperature profile of an object to be heated that is heated by the heating device according to heating conditions including different heating temperatures, or conversely, to the heating device. It is possible to find a heating condition including different heating temperatures of the heating device for heating the carried object to be heated along a temperature profile adapted to predetermined requirements. The heating device may be composed of a plurality of heating zones. In addition, if the numerical result is used, the most suitable heating source on the front and back sides for satisfying the requirement including the allowable temperature variation between the plurality of measurement points of the heated object that is carried into the heating device and heated is used. Different heating temperatures can also be found by simulation.

で表されるｍ値とすることができる。前記ｍ値を利用して、
Ｔｓ＝Ｔａ−（Ｔａ−Ｔｉｎｔ）ｅ^−ｍｔ （但し、ｅは自然対数の底）
で表される加熱基本式を基に、与えられた被加熱物の温度Ｔｓを満たすための加熱装置の前記加熱温度Ｔａと加熱時間ｔとを求めること、もしくは与えられた加熱装置の前記加熱温度Ｔａと加熱時間ｔとを用いて被加熱物の到達温度Ｔｓを求めることができる。 When the heating temperature of the heating source serving as the reference of either the front or back at the measurement position is Ta, the initial temperature of the measurement point at the measurement position is Tint, the ultimate temperature is Ts, and the heating time at the measurement position is t The numerical result is

It can be set as m value represented by these. Using the m value,
^{Ts = Ta- (Ta-Tint)} e -mt ( However, e is the base of the natural logarithm)
The heating temperature Ta and the heating time t of the heating device for satisfying the given temperature Ts of the object to be heated are obtained based on the heating basic formula represented by: or the heating temperature of the given heating device The ultimate temperature Ts of the object to be heated can be obtained using Ta and the heating time t.

で表される。 In order to find the most suitable heating temperatures different from each other in order to satisfy the requirements including the allowable temperature variation between the plurality of measurement points of the object to be heated, the heating device is close to the measurement points by the different heating temperatures of the front and back surfaces. The local heating temperature to be formed and the temperature difference coefficient that is an index of the degree of influence of the both heating temperatures on the local heating temperature are calculated using the m value. When the local heating temperature is Tx, the heating temperatures of the front and back heating sources are Ta, Tb (Ta <Tb), and the temperature difference coefficients corresponding to the heating sources are Ra, Rb, the local heating temperature Tx, each temperature The difference coefficients Ra and Rb are respectively:

It is represented by

Another aspect of the present invention is carried into a heating apparatus comprising a plurality of heating zones including at least a first heating stage and a second heating stage, which includes a heating source for heating an object to be heated from the front and back sides. A thermal analysis method for finding a heating condition for heating an object to be heated along a temperature profile that conforms to a predetermined requirement,
Specify the sample to be heated and the heating conditions for each heating stage without providing a heating temperature difference between the front and back sides.
Set the requirements for the object to be heated,
Heating the sample to be heated under the heating condition to measure the temperature at a plurality of measurement points of the sample to be heated at at least one arbitrary measurement position for each heating section of the heating device;
When the variation in temperature at the plurality of measurement points is smaller than any threshold value predetermined for each heating stage, the heating temperature and the heating time at each measurement position and the measurement temperature at each measurement point are used. To determine the heating characteristic value for each measurement position and each measurement point,
When the variation in temperature at the plurality of measurement points is greater than a predetermined threshold value for each heating stage in any one or more of the heating stages, the heating temperature between the front and back sides in the heating stage is predetermined. Re-specify the heating conditions with different temperature differences,
Reheating the object sample to be heated under the re-specified heating conditions, and measuring temperatures of a plurality of measurement points of the object sample to be heated at at least one arbitrary measurement position of the heating device;
Obtain the heating characteristic value for each measurement position and each measurement point based on the heating temperature and the heating time as a reference of either front or back at each measurement position, and the measurement temperature at each measurement point,
Set a new heating condition in which either or both of the heating temperature and the heating time are changed while maintaining the heating temperature difference (including 0) between the front and back surfaces,
Utilizing the heating characteristic value, using the heating basic equation representing the relationship between the heating temperature and the temperature of the object to be heated, calculate the temperature for each measurement position and each measurement point in the new heating condition,
If the calculated temperature profile satisfies the requirements for each heating stage, determine the heating conditions based on the new heating temperature and heating time,
When the calculated temperature profile of the result does not satisfy any one or more of the required conditions of each heating stage, the heating condition in the heating stage is expressed as the heating temperature difference (including 0) between the front and back sides. The present invention relates to a thermal analysis method characterized in that the heating condition is found by re-setting in a maintained state and repeating the above procedure.

  The object to be heated is a circuit board having a plurality of components mounted on a printed cream solder, the first heating stage is a preheating stage, the second heating stage is a reflow stage, and thermal analysis for finding the heating conditions is as follows: Appropriate reflow heating conditions for joining the component to the circuit board by heating and melting the cream solder can be found. In this case, the predetermined threshold is about 5 ° C. in the preheating stage, about 8 ° C. in the reflow stage, and the predetermined temperature difference is about 10 ° C. in the preheating stage and about 20 ° C. in the reflow stage. be able to. The heating characteristic value and the heating basic formula are the same as those described above.

Still another embodiment according to the present invention is such that the heated object that is conveyed and heated in the heating device configured by a plurality of heating zones provided with a heating source for heating the heated object from the front and back is the first heating. A heating condition including a heating temperature difference between the front and back surfaces of each of the plurality of heating zones so as to be heated along a temperature profile that meets a predetermined requirement for each of the stage and the second heating stage; A program that defines the procedure for finding out
A heating temperature and a heating time including a heating temperature difference between the front and back surfaces in at least one arbitrary measurement position of each of the plurality of heating zones, and temperature measurement results at a plurality of measurement points obtained by heating the object to be heated. Obtaining a heating characteristic value for each measurement position and each measurement point calculated based on
Of the at least one measurement point, the measurement point that showed the maximum temperature in the first heating stage during the heating is extracted, and it is confirmed whether the measurement point has exceeded the required temperature of the first heating stage Confirmation procedure A to
In the confirmation procedure A, when the measurement point exceeds the required temperature of the first heating stage, the heating temperature of the first heating stage is determined in advance while maintaining the heating temperature difference between the front and back sides. After adding the correction of the heating condition to be lowered by the standard, the temperature of each measurement point is calculated again using the heating characteristic value, and the procedure so far is repeated;
In the confirmation procedure A, when the measurement point does not exceed the required temperature for the first heating stage, a confirmation procedure for confirming whether the measurement point clears the required heating time for the first heating stage. B and
In the confirmation procedure B, when the measurement point does not reach the required heating time of the first heating stage, the heating temperature of the first heating stage is determined in advance while maintaining the heating temperature difference between the front and back sides. A procedure for repeating the above procedure by calculating the temperature at each measurement point again using the heating characteristic value after adding the correction of the heating condition to increase the heating time by a predetermined reference or to increase the heating time by a predetermined reference. When,
In the confirmation procedure B, when the measurement point exceeds the required heating time of the first heating stage, the heating temperature of the first heating stage is determined in advance while maintaining the heating temperature difference between the front and back sides. Add the correction of the heating condition to lower by the specified standard or shorten the heating time by the predetermined standard, calculate the temperature at each measurement point again using the heating characteristic value, and repeat the procedure so far Procedure and
In the confirmation procedure B, when the measurement point has cleared the required heating time of the first heating stage, all the measurement points including other measurement points satisfy the required conditions of the first heating stage. Confirmation procedure C to confirm whether it has been cleared,
When a measurement point that does not satisfy the requirements of the first heating stage is found in the confirmation procedure C, the heating temperature of the first heating stage is determined in advance while maintaining the heating temperature difference between the front and back sides. After correcting the heating conditions to increase the heating time by a predetermined standard or to increase the heating time by a predetermined standard, calculate the temperature of each measurement point again using the heating characteristic value and repeat the procedure so far Procedure and
After confirming that all the measurement points have cleared the requirements for the first heating stage in the confirmation procedure C, the minimum temperature is indicated in the second heating stage during the heating. A procedure for extracting reference measurement points that are measured points;
Among the requirements for the extracted reference measurement point in the second heating stage, both the required temperature that the maximum temperature of the object to be heated must reach and the heat-resistant limit temperature that is the limit that the object to be heated can withstand A procedure for searching for a heating condition for clearing with a predetermined algorithm using the respective heating characteristic values for the heating zone in the second heating stage,
Confirmation procedure for confirming whether the heating condition obtained as a result of the search clears the heating holding temperature for maintaining the object to be heated at a predetermined temperature for a predetermined time and the required condition at the same time. D,
In the confirmation procedure D, when any heating condition obtained as a result of the search does not satisfy the heating holding temperature and the time requirement for the same time, the heating condition is corrected to increase the heating time by a predetermined reference. In addition, the procedure of repeating the previous procedure by calculating the temperature of each measurement point again using the heating characteristic value,
In the confirmation procedure D, if there is a heating condition obtained as a result of the search that satisfies the heating holding temperature and the time condition at the same time, an object to be heated whose other requirements are preliminarily Confirmation procedure E for confirming whether the heat-resistant upper limit temperature that can withstand a predetermined time at a predetermined temperature and the requirements for the same time are cleared, and
In the confirmation procedure E, when none of the heating conditions have cleared the heat-resistant condition temperature and the time condition of the time, the heating characteristic value is added after correcting the heating condition to shorten the heating time by a predetermined reference. Calculate the temperature of each measurement point again using and repeat the previous procedure,
In the confirmation procedure E, when the heating condition clears the heat-resistant upper limit temperature and the simultaneous time condition, the heating holding temperature and the simultaneous time condition among the heating conditions are cleared in the shortest time. To temporarily set the heating conditions of the temperature profile as appropriate heating conditions,
Based on the temporarily set heating condition, the temperature of other measurement points is calculated using the heating characteristic value, and it is confirmed that all measurement points have cleared all the requirements of the second heating stage. Confirmation procedure F,
In the confirmation procedure F, when another measurement point that does not satisfy the requirement of the second heating stage is found, the heating condition is corrected by shortening the heating time with a predetermined reference, and then the heating is performed. Calculate the temperature of each measurement point using the characteristic value and repeat the previous procedure again,
In the confirmation procedure F, when all the measurement points have cleared the requirements for the second heating stage, the procedure for determining that the temporarily set heating conditions are appropriate heating conditions is executed. Relates to a program characterized by The first and second heating steps may be performed only in one of them, or a third and subsequent further heating steps may be added.

Still another embodiment according to the present invention is such that the object to be heated is conveyed and heated in a heating device comprising a first heating stage and a second heating stage having a heating source for heating the object to be heated from the front and back. Appropriate between the front and back of each of the first and second heating stages so that the heated object is heated in conformity with predetermined requirements for each of the first and second heating stages. A program that defines the procedure for finding the heating temperature difference.
The temperature of a plurality of measurement points of the sample to be heated heated under the heating condition including the heating time including the heating time at the at least one measurement position of each heating stage without any heating temperature difference is measured, and this Heating conditions, and a procedure for obtaining heating characteristic values for each measurement position and each measurement point calculated from the measurement results;
The object to be heated is heated again under the heating condition in which a temperature difference determined in advance is individually set for the front and back heating sources of the first and second heating stages, and the measurement position and the measurement point are A procedure for measuring a temperature and calculating a local heating temperature in the vicinity of each measurement point at each measurement position using the heating characteristic value;
From the heating temperature of any one of the heating sources on the front and back sides and the calculated local heating temperature, an index of the degree of influence on the local heating temperature of the reference heating source A procedure for obtaining a temperature difference coefficient;
The temperature of both heating stages in which the heating temperature difference of each heating stage is changed for each predetermined step within the range of the temperature difference determined in advance in the first and second heating stages. A procedure to set simulation heating conditions for any combination of differences;
The local heating temperature at the time of heating under the simulation heating conditions is calculated based on the temperature difference coefficient, and the temperature at each measurement position and measurement point is calculated based on the calculated local heating temperature as the heating characteristic value. The procedure of calculating each by using simulation,
From the simulation results, a procedure for finding a combination of temperature differences between the front and back surfaces of the first and second heating stages, which is optimal for the predetermined requirements for each of the first and second heating stages. The present invention relates to a program characterized by being executed. The heating characteristic value and the heating basic formula in both programs are the same as those described above.

  Still another embodiment of the present invention is a computer-readable recording medium that records a program for finding a heating condition for heating an object to be heated along a temperature profile that meets a predetermined requirement, The present invention relates to a computer-readable recording medium, wherein the program is any one of the programs described above. Still another embodiment of the present invention relates to a heating control device that controls the heating device by reading the recording medium, and a heating device that uses the heating control device. Examples of the heating device include a reflow device, a heat treatment device, a sintering device, a baking device, an incineration device, and a melting device.

  According to the thermal analysis method according to the present invention, it is not necessary to repeatedly find a heating condition including a heating temperature difference between the front and back sides of a heating apparatus that requires temperature control of an object to be heated by repeated trial and error that requires a long time. It can be easily found by performing a simulation at the same time, and it is possible to reduce the number of man-hours required for thermal analysis, improve the operating rate of equipment and improve the production quality during production.

  Further, when compared with a conventionally proposed simulation method, the trouble of inputting the physical property value of the object to be heated each time is omitted, and more efficient heating condition setting or thermal analysis becomes possible. In particular, it is advantageous because thermal analysis is possible even when the physical property value of the object to be heated cannot be obtained for some reason. Since the heating characteristic value (m value) according to the present invention based on each physical characteristic of the heating device and the object to be heated is used, the heating characteristic specific to each measurement position of the heating apparatus and each measurement point of the object to be heated It is possible to carry out a highly accurate simulation reflecting the above.

  Furthermore, according to the recording medium on which the program according to the present invention or the computer-readable program is recorded, when correcting the heating condition based on the simulation result, the computer itself corrects the heating condition with a high probability of clearing the required condition. It can be set, and appropriate heating correction conditions can be found in a short time without relying on the intuition and experience of skilled workers. In addition, the most suitable temperature difference between the front and back heating sources for heating to meet the required conditions can be found by simulation.

  According to the heating control device provided with the recording medium or the heating device according to the present invention provided with the heating control device, the temperature difference between the front and back heating sources that should heat the object to be heated under a predetermined requirement is included. Heating conditions can be found easily in a short time, the operating rate of equipment can be increased, and the yield rate of products can be improved.

  Hereinafter, a thermal analysis method according to a first embodiment of the present invention will be described with reference to the drawings. In the following description, a reflow apparatus intended for solder bonding is targeted, but application of the present invention is not limited to this. FIG. 1 shows one example of a reflow apparatus (upper) and a temperature profile (lower) of an object to be heated heated by the reflow apparatus. The circuit board 1 to be heated is carried into the reflow device 10 from the right side of the drawing by the transfer device 8, and after the reflow device 10 is transferred in the left direction of the drawing indicated by the arrow 2, it is moved out of the reflow device 10 from the left side. It is carried out. In the example of the reflow apparatus shown in FIG. 1, the inside of the apparatus is divided into seven sections from the heating sections I to VII, and hot air whose temperature is controlled from the heating sources 7 a and 7 b respectively provided for the respective heating sections I to VII. As shown by arrows 5 on both the front and back surfaces of the object to be heated, spray is applied from above and below, thereby heating the circuit board 1 as the object to be heated to an appropriate temperature.

  The graph shown on the lower side of FIG. 1 shows a temperature change, that is, a temperature profile of the circuit board 1 heated in the reflow apparatus 10. The circuit board 1 carried into the reflow apparatus at room temperature Tr from the right side of the figure gradually increases in temperature by heating in the heating zones I and II, reaches the preheating temperature T0 in the heating zone III, and between the heating zones IV and V. Thus, the preheating temperature T0 is maintained for a time t0.

  Thereafter, the circuit board 1 reaches the heating zone VI and is heated to the heating holding temperature T2 necessary for melting the solder, and the temperature is maintained for at least time t2 in the heating zone VII to surely melt the solder, and then to the outside of the heating zone. When the circuit board 1 is unloaded, the circuit board 1 gradually decreases in temperature and reaches room temperature. The molten solder solidifies during this temperature drop, and the electronic component is soldered to the circuit board 1. In order to accelerate the temperature drop after leaving the heating zone VII, a cooling device 11 that blows air or cold air may be used. The illustrated temperature profile is merely an example, and other temperature profiles can be obtained by changing the heating conditions of the heating zones I to VII.

Here, in order to surely perform solder joining while avoiding thermal destruction of electronic components, the following requirements a to g, which are generally shown in FIG. It is preferable to satisfy. The following is based on the premise of solder reflow, and if the heating purpose is different, other requirements may occur.
a. Heating holding temperature and the same time (T2, t2): The object to be heated is maintained at a predetermined temperature for a predetermined time for a certain purpose. In solder reflow, the temperature and time to keep the solder at a temperature above the melting point.
b. Necessary temperature (Treq): Temperature at which the maximum temperature of the object to be heated is to be reached. In solder reflow, the ultimate temperature required to bring the solder into a complete liquid phase.
c. Heat-resistant limit temperature (Tmax): The limit temperature that an object to be heated can withstand. In solder reflow, the allowable temperature limit for heat of electronic parts.
d. Heat-resistant upper limit temperature and the same time (T1, t1): The time that the object to be heated can withstand at a predetermined temperature. In solder reflow, the time limit when an object to be heated such as an electronic component is exposed to a predetermined temperature or higher.
e. Preheating temperature and same time (T0, t0): Required temperature and time when the object to be heated is maintained at a predetermined temperature for a predetermined time before the final target heating. In solder reflow, the temperature and time suitable for flux activation of cream solder.
f. Reflow temperature variation (ΔTmax): Limit of variation in peak temperature between a plurality of measurement points of an object to be heated. In solder reflow, local heating deviations between electronic components are eliminated. Since FIG. 1 shows only the temperature profile of one measurement point, ΔTmax which is a variation between a plurality of measurement points is not shown.
g. Preheating temperature variation (ΔT0): Variation in temperature reached between measurement points in the preheating stage. Similarly, it is not displayed in FIG.

  While the circuit board 1 to be heated is transported while being heated in the reflow apparatus 10, all the above-mentioned requirements are satisfied at one or more measurement points provided on the circuit board 1. It is necessary to set the heating conditions of the heating sources 7a and 7b in each of the heating zones I to VII.

Here, in general, a temperature change equation representing the relationship between the two when the object to be heated is heated by a heat source is introduced. FIG. 2 shows a measurement target (in this case, an electronic component) serving as a measurement point on the object to be heated 1 and a heat quantity Q applied to the measurement target. It is assumed that the heating method at this time is convection heating by hot air. The measurement object is a surface area S, a thickness D, and a volume V. The physical property value of the measurement object is density ρ, specific heat C, heat transfer coefficient h of convection heating, the temperature of hot air for heating is Ta, and the temperature of the measurement object Is Ts, the heat quantity Q is
Q = h (Ta-Ts) S
It is expressed.

と表され、右辺の{ }をはずして変形すると、

となる。ここで右辺の後半部分は輻射加熱による要因を示しており、αは被加熱物の放射線吸収率、εは被加熱物の放射線放射率、Ｆは熱放射の加熱源と被加熱物との形状係数、Ｔｈは輻射加熱の加熱源温度（表面温度）をそれぞれ表わしている。 The amount of temperature change ΔT of the surface temperature Ts of the measurement target in Δt seconds is generally

And remove the {} on the right side and transform it,

It becomes. Here, the latter half of the right side shows the factor due to radiation heating, α is the radiation absorption rate of the object to be heated, ε is the radiation emissivity of the object to be heated, and F is the shape of the heat radiation source and the object to be heated. The coefficient, Th, represents the heating source temperature (surface temperature) for radiation heating.

で概略表わすことができる。 In convection heating, since the factor due to radiant heating can be almost ignored, if the latter half of the right side of Equation 3 is omitted, the relational expression in convection heating is

Can be schematically represented by

とおき、式４を書き換えると、

となる。初期値ｔ＝０での表面温度ＴｓをＴｉｎｔとして式６を書き換えると、
Ｔｓ＝Ｔａ−（Ｔａ−Ｔｉｎｔ）ｅ^−ｍｔ ・・・・・・・・式７
となる。ここで、ＴｓとＴｉｎｔはいずれも被加熱物の表面温度で、Ｔｉｎｔが加熱開始時の初期温度、Ｔｓが加熱後の到達温度を示している。また、ｅは自然対数の底である。本明細書においてはこの加熱源の加熱温度Ｔａと被加熱物の表面到達温度Ｔｓとの関係を示す式７を「加熱基本式」と呼ぶものとする。 here,

And rewriting equation 4,

It becomes. Rewriting Equation 6 with the surface temperature Ts at the initial value t = 0 as Tint,
^{Ts = Ta- (Ta-Tint)} e -mt ········ formula 7
It becomes. Here, Ts and Tint are both surface temperatures of the object to be heated, Tint is the initial temperature at the start of heating, and Ts is the temperature reached after heating. E is the base of the natural logarithm. In this specification, Equation 7 indicating the relationship between the heating temperature Ta of the heating source and the surface temperature Ts of the object to be heated is referred to as a “heating basic equation”.

と表わすことができる。ｌｎは自然対数である。この式８のうち、右辺の加熱時間ｔ、加熱温度Ｔａ、初期温度Ｔｉｎｔ、到達温度Ｔｓはいずれも測定可能であり、これらの測定結果を用いればｍの値が算出可能となる。すなわち、被加熱物を一旦加熱してこれらの値を測定すれば、式５に示すような密度ρ、比熱物性値Ｃ、熱伝達率ｈなどの物性値を使用することなく式８を用いてｍの値を算出可能であることが分かる。本明細書において、このｍの値を「ｍ値」と呼ぶものとする。式８を用いて求められるｍ値は、実際に加熱装置によって被加熱物を測定した結果に基く値であり、加熱装置と被加熱物上の測定対象との両物理的特性を反映した加熱特性を１つの定数として数値化した値となる。 When m is calculated backward using Equation 7,

Can be expressed as In is a natural logarithm. In Equation 8, the heating time t, the heating temperature Ta, the initial temperature Tint, and the ultimate temperature Ts on the right side can be measured, and the value of m can be calculated using these measurement results. That is, once the object to be heated is heated and these values are measured, Equation 8 is used without using physical properties such as density ρ, specific heat property C, and heat transfer coefficient h as shown in Equation 5. It can be seen that the value of m can be calculated. In this specification, the value of m is referred to as “m value”. The m value obtained using Equation 8 is a value based on the result of actually measuring the object to be heated by the heating device, and the heating characteristics reflecting both physical characteristics of the heating device and the object to be measured on the object to be heated. Is a numerical value as a constant.

The following may be contained as an example of the physical characteristic which concerns on the heating apparatus at the time of heating mentioned above, and a to-be-heated material.
Heating device: heating device structure, heating device volume, type of heating source, number and arrangement of heating zones, responsiveness of heating source, thermal interference, disturbance, etc.
Object to be heated: physical property values (surface area S, thickness D, density ρ, specific heat C, heat transfer coefficient h,...), Shape, initial temperature, surface condition, etc. Especially for circuit boards, mounting density, mounting position, board Circuit layout on the surface.
In this specification, both the heating device related to the heating and the physical characteristics of the object to be heated are referred to as “heating characteristics”, and the m value is the “heating characteristics” obtained by quantifying these heating characteristics. Value.

  When heating an object to be heated with a heating device, the situation of being heated depending on the place is usually different due to the heating characteristics. In the conventional thermal analysis that uses only the physical property value of the object to be heated, these heating characteristics other than the property value between the object to be heated and the heating device are ignored, resulting in variations in simulation results. It can be a cause. In the present invention, it is possible to determine the m value in consideration of the influence factors due to these heating characteristics for each measurement point. In other words, by using this m value, it is possible to obtain a highly accurate result that is more suitable for the actual heating condition than in the case of simulating simply by using the physical property value of the object to be heated.

  FIG. 3 shows an outline of a heated object sample 1 (hereinafter referred to as “sample substrate 1”) that is heated to obtain the m value. A plurality of electronic components 3 are mounted on the sample substrate 1, and among these electronic components 3a, 3b, and 3c to be measured, thermocouples 4 for temperature measurement are respectively attached. The thermocouple 4 is connected to an external recording device 6 for recording the measurement result. This measurement result can be connected from the recording device 6 to a computer or a heating control device via an A / D converter (not shown). In FIG. 3, only three measurement points of the electronic components 3a, 3b, and 3c are to be measured, but this number can be arbitrarily set. In general, list the requirements for heating the components mounted on the circuit board, extract multiple components close to the upper and lower limit temperature conditions from them, and select them as the object to be measured. It is preferable to select, as a measurement target, a large component that tends to have a low reached temperature during heating. In addition, a plurality of measurement objects (for example, the upper and lower joints of a tall component) can be provided for one component.

  FIG. 4 actually carries the sample substrate 1 according to the above-described configuration into the reflow apparatus 10 and heats it, and calculates the m value in one heating area in the reflow apparatus 10, in the illustrated example, the heating area I in FIG. Each temperature measurement position is shown. In the figure, the vertical axis indicates the temperature at the measurement point, and the horizontal axis indicates time. In this specification, the location on the heated object to be measured, which is the target for measuring the temperature, is the “measurement point”, and the location in the heating apparatus for measuring the temperature (that is, the m value is set for each measurement point). The place to be calculated) is called “measurement position” to distinguish between the two. Although the horizontal axis in the figure is represented by time, it can be seen that the heated object to be transported passes through the measurement position every time t. In the example shown in the figure, there are n measurement positions equally distributed in the heating area I, and the object to be heated is heated at each measurement position by time t, and the temperature is sequentially raised by this heating. The distribution of the measurement positions is not limited to the uniform distribution and can be arbitrarily determined.

  The sample substrate carried in at room temperature Tr is heated at each measurement position in the heating zone I by hot air at a temperature Ta for a time t, and the measurement target component at each measurement position (ie, measurement) at a stage where the temperature gradually rises from Tr. Point) By measuring the surface temperatures Ts of 3a, 3b, and 3c, respectively, a total of n m values (m1, m2, m3,. In Equations 7 and 8, the initial temperature Tint at one measurement position is the ultimate temperature Ts at the immediately previous measurement position.

  Although FIG. 4 shows only the m value for the electronic component 3c, n m values are obtained for the other electronic components 3a and 3b based on the temperature measurement results. In an experiment conducted by the inventors of the present application, n = 100, that is, 100 measurement positions are determined for each measurement point in one heating zone, and 100 m values are obtained. In this way, a large number of m values are obtained because of variations in hot air temperature and wind speed distribution even in the same heating zone, and influences by outside air and heating near the entrance / exit of the reflow device 10 and the boundary of the heating zone. Since thermal interference between the areas is considered, the measurement position is subdivided more finely to obtain the heating characteristic value, and the accuracy of the subsequent simulation is increased. On the contrary, if it is only for grasping | ascertaining the general | schematic characteristic of a heating apparatus, even if it is calculating | requiring only one m value for every heating area, it is one about the most critical location in the whole heating apparatus. Only the m value may be obtained.

  Although FIG. 4 shows the heating area I, the measurement positions are similarly subdivided for the other heating areas II to VII, the surface temperature at each position is measured, and the m value at each measurement position is obtained. Assuming that each heating zone is similarly divided into 100, a total of 100 segments × 7 heating zones × 3 measuring points = 2100 m values are obtained for three measurement points, and these values are obtained by a computer or a heating control device. Entered.

  By the way, as shown in FIG. 3, the measurement points (measurement target parts) 3a, 3b, 3c have different shapes and heights depending on the types of parts. In particular, in the case of a tall part as shown at the measurement point 3c in FIG. 3, since the upper end portion approaches the heating source 7a at the time of heating, the temperature rise at the distal end portion becomes relatively intense. In order to avoid the thermal destruction of the component due to such a temperature rise and to obtain a reliable solder joint with the circuit board, as described above, the heating sources 7a and 7b provided in the vertical direction shown in FIG. In general, the heating temperature of the heating source 7b on the lower side (the back side of the circuit board) is set to be higher than that of the upper (the same side) heating source 7a, and heating is performed with a temperature difference. ing.

  Thus, when the sample substrate 1 is heated by providing a temperature difference between the heating sources 7a and 7b on the front and back of the object to be heated, the m value obtained by the above equation 8 also includes the temperature difference between the front and back. Calculated as the included heating characteristic value. According to the experiments conducted by the inventors of the present application, if the temperature difference between the heating temperatures of both the heating sources 7a and 7b is within a certain limit (for example, within about 20 ° C.), As will be described later, it has been found that even if the heating temperature Ta is represented by the heating temperature of either one of the front and back heating sources, no large error occurs. Further, it was found that when the heating temperature was changed while the temperature difference between the heating temperatures of both the heating sources 7a and 7b was maintained at the same value, a highly accurate simulation could be performed using the m value. Therefore, in this embodiment, even when there is a difference in the heating temperature between the front and back sides for heating the object to be heated, the heating temperature Ta in the definition of the m value is the heating of the heating source 7a on the front side unless otherwise specified. It shall refer to temperature. If the heating temperature of the back side heating source 7b is Tb (Ta <Tb) and the temperature difference between the front and back sides is D, the back side heating temperature Tb is expressed by Tb = Ta + D. Of course, the heating temperature Tb on the back side can be defined as a reference heating temperature Ta.

  Next, a method for simulating the temperature profile of the object to be heated when the heating conditions of the reflow apparatus 10 are changed using the m values for each measurement position and measurement point obtained as described above will be described. . As described above, in the present embodiment, the heating characteristic value is based on the heating and actual measurement of the sample substrate without using physical properties such as the thermal conductivity h, the density ρ, and the specific heat C as shown in Equation 5. m value is calculated. Since the m value calculated in this way is a value reflecting the heating characteristics peculiar to each heating measurement position and each measurement point, the temperature profile after the change of the heating condition can be obtained by using the m value. The simulation can be performed efficiently and with high accuracy without being verified by heating the sample substrate as in the technology.

FIGS. 5A to 5E show the experimental result 1 of the simulation according to the present embodiment using the reflow apparatus. FIG. 5A shows the heating temperature in each heating zone when the sample substrate 1 is carried into the reflow apparatus 10 and heated to measure the temperature. The requirements for aiming at this time were as follows.
a. Heating holding temperature and the same time (T2, t2): 220 ° C., 20 seconds or more b. Required temperature (Treq): 230 ° C
c. Heat-resistant limit temperature (Tmax): 240 degreeC
d. Heat-resistant upper limit temperature and the same time (T1, t1): 200 ° C., 40 seconds or less e. Preheating temperature and same time (T0, t0): 160 ° C. to 190 ° C., 60 seconds to 120 seconds f. Reflow temperature variation (ΔTmax): within 8 ° C. g. Preheating temperature variation (ΔT0): Within 5 ° C

  The sample substrate 1 is carried in from the heating zone I shown on the right side of FIG. 5A, and is subsequently carried out of the reflow apparatus 10 through the heating zones II to VII in order. Of these, the first heating stage from the heating zones I to V is the preheating stage, and the second heating stage from the heating zones VI and VII is the reflow stage. In the heating example shown in FIG. 5 (a), there is no temperature difference between the heating temperatures Ta and Tb by the front and back heating sources 7a and 7b provided in the heating device, and the upper limit value of the preheating temperature is 190 ° C. In the reflow region, the heat resistant limit temperature is 240 ° C. Further, the transfer speed v of the transfer device for transferring the sample substrate 1 at this time was 1.25 m / min. In addition, when a to-be-heated material is conveyed with a conveying apparatus, it can also manage using the conveyance speed v instead of the heating time t in this way. That is, if the length of the corresponding measurement position is 1, it can be replaced with v = 1 / t.

  The sample substrate 1 is carried into the reflow apparatus 10 set to the heating condition and heated, and the surface temperature Ts at each measurement position of the reflow apparatus 10 is measured for each measurement point of the sample substrate 1. Based on the temperature measurement result, first, it is checked whether or not the reflow temperature variation ΔTmax and the preheating temperature variation ΔT0 shown in f and g are satisfied among the required conditions. Here, it is assumed that all temperature variations satisfy the conditions indicated by f and g, and the process proceeds to the following simulation steps. Satisfying the conditions of f and g means that the temperature variation between the measurement points is small, and therefore it is not necessary to provide a temperature difference between the heating sources 7a and 7b. . That is, the following simulation is performed with Ta = Tb. The m value at this time is calculated using Equation 8 from the heating temperature Ta of the heating device and the heating time t (here, the conveyance speed v).

  FIG. 5 (b) shows the heating conditions when the simulation is performed by changing the temperatures of the heating zones I, II, and VI while keeping the transport speed v of the transport device the same (1.25 m / min). Yes. As described above, no temperature difference is provided between the front and back heating temperatures Ta and Tb. FIG. 5C shows the result of a simulation performed based on this changed heating condition. This simulation is obtained by calculating the surface temperature Ts at each measurement point of the object to be heated by the heating basic equation of Equation 7 using the m value of each measurement point obtained at each measurement position.

  In the illustrated example, there are three measurement points (measurement points 3a, 3b, 3c) and f. Target temperature variation (ΔTmax), c. Heat-resistant limit temperature (Tmax, here "peak (maximum) temperature" at each measurement point), a. Heating holding temperature and the same time (t2, here “time of 220 ° C. or more”), d. It represents four items of the heat-resistant upper limit temperature and the same time (t1, here, “time of 200 ° C. or more”). In the simulation, all surface temperatures Ts at 700 measurement positions at which m values are measured at one measurement point of the object to be heated are calculated, and therefore it is of course possible to obtain data other than the items shown in the figure. For example, in the illustrated example, only the data of the reflow stage is displayed, but data of the preheating stage (for example, the median value in the heating zone III) can be obtained as necessary.

  FIG. 5D shows the measurement results when the sample substrate 1 is actually heated for verification purposes with respect to the same items at the same measurement points and measurement positions as those shown in FIG. FIG. 5E shows a difference between the simulation result of FIG. 5C and the actual measurement result of FIG. 5D. As can be seen from the result of FIG. 5 (e), the maximum temperature difference between the simulation and the actual measurement is 2.4 ° C. (228.1 ° C.-225.7 ° C.) at the measurement point 3b, and the maximum time difference is the measurement. A slight difference of 2.4 seconds (28.0 seconds to 25.6 seconds) at the point 3a is recognized. Considering that there are variations in the reflow device and the measurement device itself, this difference is extremely small, indicating the high accuracy of the simulation according to the present embodiment.

  Note that the peak (maximum) temperature at the measurement point 3b marked with a circle in FIGS. 5 (c) and 5 (d) is the required ultimate temperature (Treq), that is, necessary for making the solder into a complete liquid phase. This indicates that the temperature (230 ° C.) condition is not cleared, and therefore it is necessary to consider further increasing the reflow temperature or reducing the conveyance speed.

  FIG. 6 shows a temperature profile based on the simulation result using the m value obtained by the present embodiment at the measurement point 3a shown in FIGS. 5C and 5D, and the sample substrate 1 under the same conditions. The temperature profile obtained by actually heating with the reflow apparatus 10 is compared. The vertical axis is temperature and the horizontal axis is time (from right to left). In the simulation, the temperature at the measurement point is calculated using m values obtained at 100 measurement positions (total of 700 positions) for each heating zone. Then, this is plotted to create a temperature profile. As is apparent from the figure, it is understood that a nearly accurate temperature profile can be obtained by performing a temperature simulation at a total of 700 locations.

  Next, FIGS. 7A to 7E show another experimental result 2 of the simulation according to the present embodiment. In the example shown in FIGS. 5A to 5E, there was no temperature difference between the front and back heating temperatures Ta and Tb. Here, since the reflow temperature variation ΔTmax did not satisfy the required condition of 8 ° C. or less in the initial heating of the sample substrate 1, as shown in FIG. A temperature difference of 20 ° C. is provided in the sample substrate 1 and the sample substrate 1 is heated again. The sample substrate 1 is heated under the heating conditions shown in FIG. 7A to measure the temperature at each measurement position and each measurement point, and each m value is calculated based on the result.

  Next, FIG.7 (b) has shown the heating conditions in the case of performing a simulation. As shown in the figure, the heating temperatures Ta and Tb on the front and back sides of the heating zones VI and VII in the reflow stage are increased by 20 ° C., respectively, and the heating temperature on the front and back sides of the heating zone V in the preheating stage is increased by 10 ° C. . As described above, what is important here is that the temperature difference between the heating temperatures Ta and Tb of the heating sources 7a and 7b on the front and back is the temperature difference when the m value is calculated (0 in the preheating stage, 20 ° C. in the reflow stage) ). That is, the m value calculated by providing a temperature difference between the front and back is used, and the simulation is performed using the heating characteristic based on the temperature difference as it is.

  FIG. 7C shows the result obtained by the above-described simulation, and FIG. 7D shows the result obtained by actually heating the circuit board 1 under the same heating conditions for the purpose of verification. FIG. 7E shows the difference between the two. In the experimental result 2, the number of measurement points is 5 from 3a to 3e. As is apparent from FIG. 7 (e), the difference between the simulation and the actual measurement is 1.2 ° C. at maximum (234.8 ° C.-233.6 ° C.) and 2.0 seconds at maximum (32. 0 seconds-30.0 seconds) and the difference shown in FIG. 5 (e) is not inferior, and even if a temperature difference is provided between the heating sources 7a and 7b, the temperature difference is maintained. It is shown that an extremely accurate simulation result can be obtained by using the m value based on the temperature difference as it is.

  According to experiments conducted by the present inventors, when the temperature variation ΔTmax in the reflow stage is about 8 ° C. or more, a temperature difference is provided between the heating temperatures Ta and Tb of the heating sources 7a and 7b on the front and back sides. In many cases, it was difficult to find an appropriate heating condition when the heating condition was changed. Conversely, when ΔTmax exceeds about 8 ° C, appropriate heating conditions can be easily found by providing a temperature difference of about 20 ° C between the heating temperatures Ta and Tb on the front and back sides, and also when changing the heating temperature. It has been found that by making this temperature difference (about 20 ° C.) unchanged, a highly accurate simulation can be performed using the m value as it is.

  The temperature variation ΔTmax is set to about 8 ° C. when severe temperature restrictions using lead-free solder are provided. For example, when temperature restrictions such as using conventional lead solder are moderate, ΔTmax is Even when the temperature is 10 ° C. or higher, it may not be necessary to provide a difference between the heating temperatures Ta and Tb on the front and back sides of the article to be heated. In addition, the temperature difference between the front and back surfaces can be further increased when the temperature constraint is moderate. However, even when changing the heating conditions of the simulation, it is preferable to keep the temperature difference between the front and back surfaces as it is.

  Although not shown, in other experiments conducted by the inventors of the present application, when the temperature variation ΔT0 in the preheating stage exceeds about 5 ° C., the heating temperatures Ta and Tb between the front and back sides in the preheating stage are also included. It is preferable to provide a temperature difference, and the temperature difference at that time is preferably about 10 ° C. Even in this case, a simulation is performed using the m value calculated by heating the sample substrate 1 with the temperature difference of about 10 ° C., and this temperature difference (10 ° C.) is set when setting the heating conditions for the simulation. It is preferable to keep the value as it is. Further, when the temperature restriction such as the use of lead solder is gentle, the temperature variation ΔT0 can be set to 8 ° C. or higher.

  The thermal analysis method for performing the above simulation will be described again with reference to the flowchart of FIG. This thermal analysis method can be applied to a method of setting production conditions of a heating device in a production process such as reflow heating. First, in step # 1, conditions for the sample / heating device are set. This includes the setting of the heating temperature conditions of each of the heating zones I to VII, the heating time (conveyance speed), the temperature measurement point of the sample substrate, and the measurement position in each heating zone. In Step # 1, no temperature difference is provided between the heating temperatures Ta and Tb of the front and back heating sources 7a and 7b. Next, in step # 2, a required condition is input. Here, it is preferable that T0, T1, T2, Tmax, Treq, ΔTmax, ΔT0, t0, t1, and t2 in each of the above-described requirement conditions a to g are included. May be.

  Based on the above condition settings, the sample substrate 1 is actually carried into the reflow apparatus 10 in step # 3 and heated under the heating conditions in step # 1, and the surface temperature Ts (including the initial temperature Tint) at each measurement point of the sample substrate 1 is measured. ) Using a temperature measuring device. In step # 4, it is checked whether the measurement result and the temperature variation between the measurement points satisfy the required conditions. In the above example, it is checked whether the temperature variation ΔT0 in the preheating stage is within 5 ° C. or the variation Tmax in the reflow heating stage is within 8 ° C. If these variations are not within the allowable range, in step # 5, a temperature difference D is provided between the heating temperatures Ta and Tb of the heating sources 7a and 7b on the front and back sides. For example, when the temperature variation ΔT0 in the preheating stage is outside the allowable range, the heating temperature Tb on the back side in the preheating stage is raised by 10 ° C. with respect to the temperature set in step # 1. Similarly, when the variation ΔTmax in the reflow stage is outside the allowable range, the heating temperature Tb on the back side in the reflow stage is raised by 20 ° C. with respect to the temperature set in step # 1. Under such heating conditions in which a temperature difference is provided between the front and back surfaces, the process returns to step # 3 again to heat the sample substrate 1 and measure the temperature at each measurement point. The temperature difference of 10 ° C. in the preheating stage and the temperature difference of 20 ° C. in the reflow stage are examples, and other temperature differences can be set in advance according to the heating purpose.

  If any temperature variation in the preheating stage and the reflow stage is within the allowable range in step # 4, in step # 6, the heating characteristic value for each measurement point and each measurement position from the heating condition and the measurement result at that time. M value which is is calculated. The calculation method for calculating the m value is the same as the contents described so far shown in Expression 8. However, the heating temperature Ta in Formula 8 when there is a temperature difference between the front and back heating sources 7a and 7b is determined based on one of the front and back heating sources 7a and 7b. Here, the description will be made assuming that the heating temperature Ta of the heating source 7a on the front side is set as a reference, but the heating temperature Tb on the back side may be set as a reference. Again, it is not necessary to input the physical property value of the object to be heated in order to calculate the m value of the present embodiment. In addition, the obtained m value is a heating characteristic value including the physical characteristics of the heating device and the object to be heated. If there is a temperature difference between the heating sources on the front and back, the heating characteristic including the temperature difference is also included. Value.

  Next, the process proceeds to the simulation stage, and simulation conditions are set in step # 7. Here, the heating temperature and heating time (conveying speed) for each heating zone can be set arbitrarily. However, when a temperature difference is provided between the heating sources on the front and back surfaces in step 5, the heating temperatures Ta and Tb that are translated while maintaining the same temperature difference are set. As will be described later, when the heating is a convection type, it is also possible to set the speed change amount of the hot air. In step # 8, the m value calculated in step # 6 is used, and a temperature profile is created based on the result of simulation based on the simulation conditions. Although the simulation profile shown in FIG. 6 shows the result of only one measurement point, a similar temperature profile is obtained for all the measurement points. Based on all the profiles, it is first checked in step # 9 whether the required conditions are cleared in the first heating stage. The first heating stage corresponds to the preheating stage in the example of reflow heating. Here, it is checked whether or not the temperatures at all measurement points satisfy the required conditions T0 and t0 (150 to 190 ° C. and 60 to 120 seconds in the previous example).

  If this requirement is not satisfied at all measurement points, the process returns to step # 7 to set simulation conditions again, such as changing the heating temperature. As described above, if the heating conditions in the first heating stage are set to the same temperature as the upper limit of the required conditions (190 ° C. in the previous example) in the initial simulation conditions, the object to be heated is usually higher than this. Therefore, if the required condition cannot be cleared here, it means that the temperature is lower than the required temperature. Therefore, in the simulation condition setting again when the requirements for the first heating stage are not cleared, correction is performed to increase the heating temperature or lengthen the heating time (decrease the conveyance speed). In general, the first heating stage for the purpose of preheating or the like has milder requirements than the second heating stage, which is the final objective. If there is a temperature difference between the front and back heating temperatures Ta and Tb, the temperature difference is kept the same here.

  Next, in step # 10, it is checked whether the requirements in the second heating stage are cleared. In the example of reflow heating, the most stringent temperature control is required throughout the entire heating process so that the heating in the reflow stage, which is usually the second heating stage, reliably solders the electronic components without destroying them at high temperatures. In the illustrated example, the first and second heating stages are shown in steps # 9 and # 10. However, there may be third and fourth and subsequent heating stages in which required conditions are separately determined. . Further, when the required condition is set to only one heating stage, the heating stage of either step # 9 or # 10 may be omitted.

  As a result of the check in step # 10, if the set required condition is not satisfied, the process returns to step 7 to set the simulation condition again. For example, if the simulation result is as shown in FIG. 5C, the required temperature (Treq) at the measurement point 3b surrounded by a circle in the same figure does not clear the required temperature of 230 ° C. In such a case, in order to clear the required conditions, in step # 7, the heating conditions such as increasing the heating temperature in the reflow stage or increasing the heating time (decreasing the conveying speed) are changed. . When a temperature difference is provided between the front and back heating temperatures Ta and Tb, the temperature difference is maintained as before. As is clear from the diagram on the lower side of FIG. 1, various requirements are complicated in this reflow stage, and many factors need to be taken into consideration in setting appropriate simulation conditions.

  In the prior art, the sample substrate was actually heated, and based on the measurement results, the skilled worker re-sets the next heating condition, repeated the sample heating, and repeated measurement. However, in the present embodiment, a simulation can be performed on a desk using the m value calculated once. Even when a heating temperature difference is provided between the front and back heating sources, a highly accurate simulation can be performed efficiently by setting the heating conditions while maintaining this temperature difference. For this reason, even if it confirms repeatedly on the conditions set arbitrarily to some extent, this can be performed in a short time. As an example, in order to verify the heating result by changing the heating conditions 10 times according to the conventional technique by actual measurement, it usually took about 5 hours including the waiting time until the above-described heating device is stabilized. If the simulation according to the present embodiment is used, this can be completed in about one hour. It is clear that the operation of finding the appropriate heating condition can be performed more efficiently by a computer, but this will be described in a later embodiment.

  If all the required conditions in the reflow region are cleared in step # 10, the setting of the heating condition based on the simulation result is completed in step # 13 according to the arrow indicated by the broken line. In steps # 11 and # 12, based on the conditions set in step # 10, verification heating is actually performed using a sample substrate to verify whether the required conditions are cleared. Steps # 11 and # 12 are optional and can be omitted if it is proved that the accuracy of the simulation is high. If the required conditions are not satisfied by the verification heating using the sample substrates in steps # 11 and # 12, the process returns to step # 6 and the m value is calculated using the measurement data during the verification heating. Correct and perform the simulation again. By repeating the simulation in which such heating conditions are changed, a more accurate temperature prediction can be obtained.

  Further, as a result of heating or simulation of the sample substrate 1, for example, the object to be heated exceeds the heat-resistant limit temperature (Tmax) 240 ° C. at one of the measurement points, and the required ultimate temperature (Treq) 230 ° C. at one of the other measurement points. There may be an extreme situation (large temperature variation) that does not lead to. In such a case, for example, there may be cases where repair can be made by changing the transport speed v (or heating time t) of the transport device, but it may be difficult to set a new correction condition because the set condition is already limited. In the present invention, even in such a case, several simulations are performed in a short time, and as a result, if the clearing of the predetermined condition cannot be expected, it is possible to determine early that the condition cannot be set. In trial and error in the prior art, the search for conditions is repeated even in such a case, and a time loss is generated.

  As described above, the thermal analysis method according to the present embodiment has been described. However, the above-described thermal analysis method can be used by further expanding the application range. One example is a simulation based on a change in the speed of hot air in the heating zone. In the above-described embodiment, the wind speed of the hot air is constant (for example, 5 m / second). On the other hand, it is known that even when hot air having the same temperature is blown, if the wind speed changes, heat transfer to the object is affected. The relationship between the wind speed and heat transfer of the hot air can generally be obtained by experiments, and statistical data is available in some cases.

As an example, FIG. 9 shows the relationship between the velocity of hot air during heating and the m value that is a heating characteristic value obtained by the inventors of the present application through experiments. In the figure, the horizontal axis represents the hot air velocity (m / sec), and the vertical axis represents the m value. From the experimental results, if the vertical m value is y and the horizontal wind speed is x, the relationship between the two is
y = 0.006x ² −0.0009x + 0.0377 Equation 9
It is expressed by the approximate expression of By obtaining such a relationship in advance, even if the velocity of the hot air is changed when setting the simulation conditions, the change in m value due to this is corrected by Equation 9, and the rest is exactly the same as described above. The simulation can be performed using the m value after correction according to the procedure.

で表される。右辺の前半部分は対流による要素を示し、後半部分は輻射による要素を示している。対流による加熱をベースとした式４では、輻射加熱による影響をほぼ無視できるとして右辺の輻射加熱要素の後半部分を省略している。これと同様に、輻射による加熱の場合には、右辺の対流加熱要素の前半部分を省略して

と表すことができる。この式１０を前記式４に置き換えて輻射による加熱をベースとした場合の加熱特性値を求め、あとは先の実施の形態で説明した内容と同じ手順により、この加熱特性値をもとにして輻射加熱の場合における各種のシミュレーションを行うことが可能である。 In addition, as an example of other application of the heating characteristic value (m value) according to the present invention, the above-described embodiment is premised on convection heating in which hot air is blown onto an object to be heated. Application to heating by radiated light. As shown in Equation 3, the temperature change ΔT of the heated object heated in Δt time is generally

It is represented by The first half of the right side shows elements due to convection, and the latter half shows elements due to radiation. In Equation 4 based on convection heating, the latter half of the radiant heating element on the right side is omitted because the influence of radiant heating can be almost ignored. Similarly, in the case of heating by radiation, the first half of the convective heating element on the right side is omitted.

It can be expressed as. The formula 10 is replaced with the formula 4 to obtain a heating characteristic value based on heating by radiation, and the rest is based on the heating characteristic value by the same procedure as described in the previous embodiment. Various simulations in the case of radiant heating can be performed.

  As a further application of the heating characteristic value, that is, the m value according to the present invention, there is an application to cooling an object. In the heating apparatus shown in FIG. 1, the cooling apparatus 11 described above is shown on the apparatus outlet side. When it is necessary to avoid leaving a circuit board or the like to be heated for a long time at a high temperature, cooling can be promoted by blowing air or cold air onto the heated object. Also in this cooling device, the temperature of air to be blown or cold air and the cooling time are determined in the same manner, the temperature at the measurement point of the object to be heated (cooled object) is measured to obtain the m value, and the m The value can be used to perform a temperature simulation.

  In FIG. 1, the heating device is of a type in which the object to be heated is conveyed by the conveying device in the heating device. The present invention is also applicable to a heating apparatus that performs heating according to a predetermined temperature profile by changing the heating temperature of the heating apparatus for each heating section for a certain time without moving. Accordingly, the heating zones shown in FIG. 1 do not necessarily mean different zones that are physically separated, and the heating sections at regular intervals should be interpreted as corresponding to the heating zones shown in the drawing.

  In the above-described embodiment, a simulation is described in which an appropriate heating condition for obtaining a given temperature profile (required condition) is set. Conversely, a heating condition is given and this heating condition is set. Of course, a simulation for obtaining a temperature profile of an object to be heated heated by the above is also possible. This is obtained by inputting the heating temperature Ta and the heating time t corresponding to each measurement position into the heating basic formula (Formula 7), and this is calculated for each of a plurality of measurement positions (total of 700 in the previous example). Thus, for example, a simulation result of a temperature profile as shown in FIG. 6 can be obtained. Even when a temperature difference is provided between the front and back heating sources 7a and 7b, the heating conditions corresponding to the heating temperature (the heating temperature Ta on the front side in the above example) serving as a reference when the m value is obtained are set. A similar temperature profile can be simulated by using the m value while maintaining this temperature difference.

  Next, a thermal analysis method according to a second embodiment of the present invention will be described with reference to the drawings. In the previous embodiment, when the temperature variations ΔT0 and ΔTmax exceed the allowable range, a predetermined temperature difference between the front and back heating sources (for example, 10 ° C. in the preheating stage and 20 ° C. in the reflow stage). The thermal analysis is performed by changing the heating temperature while maintaining the predetermined temperature difference. In the present embodiment, this is corrected, and an appropriate temperature difference D to be provided between the front and back heating temperatures Ta and Tb is obtained by simulation. The heating apparatus to be used may be the same as that shown in FIG. 1, and the heating requirement conditions of the object to be heated are the same as those shown in the previous embodiment. In the following description, reflow heating using lead-free solder is taken as an example, but the present invention can be similarly applied to other thermal analysis.

  FIG. 10 is a flowchart showing the procedure of the thermal analysis method according to the present embodiment. In the figure, step # 1 to step # 3 are the same as in the previous embodiment shown in FIG. That is, the sample substrate 1 is heated under a heating condition in which there is no temperature difference between the heating temperatures Ta and Tb of both the heating sources 7a and 7b, and the m value at that time is calculated in step # 4.

  In step # 5, a temperature difference D is provided between the heating temperatures Ta and Tb of the heating sources on the front and back sides. For example, a predetermined temperature difference D (Dp, Dr) such as 10 ° C. for the temperature difference Dp between the heating temperatures Ta and Tb in the preheating stage and 20 ° C. for the temperature difference Dr between the heating temperatures Ta and Tb in the reflow stage. ). More specifically, the front side heating temperature Ta = 180 ° C. in the preheating stage, the back side heating temperature Tb = 190 ° C., the front side heating temperature Ta = 240 ° C. in the reflow stage, and the lower side heating temperature Tb = 260 ° C. And These temperature differences are examples of reflow heating of lead-free solder and can be other temperature differences. Next, in step # 6, the sample substrate 1 is heated again under the heating conditions with this temperature difference. When the sample substrate 1 is heated, the initial temperature Tint and the reached temperature Ts are measured for each measurement point 3 of the sample substrate 1 and each measurement position of the heating device. As an example, it is assumed that the initial temperature Tint at one measurement point 3 at the measurement position with the reflow stage is measured at 232 ° C. and the ultimate temperature Ts is measured at 238 ° C.

となる。この式１１に、上述したＴｓ＝２３８℃、Ｔｉｎｔ＝２３２℃、またｍにはステップ＃４で算出したｍ値をそれぞれ代入すると、例えばＴａ＝２４８℃と算出される。 Next, based on the above measurement result, the local heating temperature Tx in the vicinity of the measurement point 3 is obtained in Step # 7. The local heating temperature Tx is a local virtual heating temperature formed in the vicinity of the measurement point 3 necessary for setting the temperature Ts at the measurement point 3 to 238 ° C. described above. More specifically, Formula 7 which is a heating basic formula:
^{Ts = Ta- (Ta-Tint)} e -mt
Is transformed into an equation for obtaining the heating temperature Ta from the attainment Ts (238 ° C.).

It becomes. If the above-described Ts = 238 ° C., Tint = 232 ° C., and m value calculated in step # 4 are substituted for m, for example, Ta = 248 ° C. is calculated.

  The temperature calculated in this way is Ta = 248 ° C., and the measurement point depends on the heating temperature Ta = 240 ° C. on the front side and the heating temperature Tb = 260 ° C. on the front side and the different heating temperatures from the heating sources on both sides. It can be said that this is a locally assumed heating temperature formed in the vicinity of 3. This is defined as the local heating temperature Tx.

また、裏側の加熱温度Ｔｂに対応する温度差係数Ｒｂは：

で表される。上述した例における具体的な数値を入れれば、
Ｒａ＝（２４８−２４０）／（２６０−２４０）＝０．４
Ｒｂ＝（２６０−２４８）／（２６０−２４０）＝０．６
となる。すなわち、当該測定点３において、局部的加熱温度に及ぼす影響度の指標は、表側の加熱源７ａが０．４、裏側の加熱源７ｂが０．６（双方の合計で１．０）と想定される。このような温度差係数Ｒをそれぞれの測定点３及び測定位置において算出する。 Next, in step # 8, a temperature difference coefficient R that is an index of the degree of influence of the heating temperatures Ta and Tb (Ta <Tb) on the front and back sides on the local heating temperature Tx is obtained. Specifically, the temperature difference coefficient Ra corresponding to the heating temperature Ta on the front side is:

Further, the temperature difference coefficient Rb corresponding to the heating temperature Tb on the back side is:

It is represented by If we put the specific numerical values in the above example,
Ra = (248−240) / (260−240) = 0.4
Rb = (260-248) / (260-240) = 0.6
It becomes. That is, at the measurement point 3, the index of the degree of influence on the local heating temperature is assumed to be 0.4 for the front-side heating source 7a and 0.6 for the back-side heating source 7b (1.0 in total for both). Is done. Such a temperature difference coefficient R is calculated at each measurement point 3 and measurement position.

Next, in step # 9, based on the temperature difference coefficient R obtained above, a simulation is performed to obtain appropriate temperature differences Dp, Dr of the heating sources 7a, 7b between the front and back sides in the preheating stage and the reflow stage. . Here, the case where the maximum temperature difference Dp in the preheating stage is 10 ° C., the maximum temperature difference Dr in the reflow stage is 20 ° C., and the simulation is performed at the steps separated by 10 ° C. will be described. At this time, there are the following six combinations of the temperature differences Dp and Dr.
a. Preheating stage temperature difference Dp = 0; Reflow stage temperature difference Dr = 0
b. Preheating stage temperature difference Dp = 0; Reflow stage temperature difference Dr = 10 ° C.
c. Preheating stage temperature difference Dp = 0; Reflow stage temperature difference Dr = 20 ° C.
d. Preheating stage temperature difference Dp = 10 ° C .; Reflow stage temperature difference Dr = 0
e. Temperature difference Dp = 10 ° C. in preheating stage; Temperature difference Dr = 10 ° C. in reflow stage
f. Preheating stage temperature difference Dp = 10 ° C .; Reflow stage temperature difference Dr = 20 ° C.

When the local heating temperature Tx in each of the above combinations is obtained, the following results are obtained. Here, the heating temperature Ta on the front side is used as the reference temperature. Specifically, the preheating stage is Ta = 190 ° C., and the reflow stage is Ta = 240 ° C. Again, it is equally possible to use the backside heating temperature Tb as the reference temperature.
<Preheating stage: Tx = Ta + Dp × Ra>
a. Tx = 190 + 0 × 0.4 = 190 ° C.
b. Tx = 190 + 0 × 0.4 = 190 ° C.
c. Tx = 190 + 0 × 0.4 = 190 ° C.
d. Tx = 190 + 10 × 0.4 = 194 ° C.
e. Tx = 190 + 10 × 0.4 = 194 ° C.
f. Tx = 190 + 10 × 0.4 = 194 ° C.
<Reflow stage: Ta + Dr × Ra>
a. Tx = 240 + 0 × 0.4 = 240 ° C.
b. Tx = 240 + 10 × 0.4 = 244 ° C.
c. Tx = 240 + 20 × 0.4 = 248 ° C.
d. Tx = 240 + 0 × 0.4 = 240 ° C.
e. Tx = 240 + 10 × 0.4 = 244 ° C.
f. Tx = 240 + 20 × 0.4 = 248 ° C.

The ultimate temperature Ts at the measurement point 3 when the heating temperature Tx is set is Ts = Tx− (Tx−Tint) e ^{−mt in} Equation 7, which is a basic heating equation.
Is obtained by substituting the values of Tx and Tint for. The initial temperature Tint is obtained from the temperature reached at the immediately previous measurement position. Similarly, by obtaining the respective temperatures Ts at all measurement points and measurement positions, the temperature profile of each measurement point 3 can be created in step # 9.

  In the case of reflow heating, since the combination of temperature differences that minimizes the variation in peak temperature at each measurement point is the optimal heating condition, each of the above-mentioned local heating conditions a to f is selected in step # 10. By selecting the one having the smallest temperature difference between the peak temperatures of the measurement points, the optimum heating temperature difference Dp, Dr between the front and back sides in the preheating stage and the reflow stage can be specified. In step # 9, temperature profiles at all measurement points can be obtained, so in addition to the conditions that minimize ΔTmax, a combination of temperature differences that best suits the required conditions according to the heating purpose is arbitrarily selected from the simulation results. can do.

  In the above-described example, the temperature difference coefficient Ra between the preheating stage and the reflow stage is assumed to be the same, but if different, it can be similarly calculated by using each temperature difference coefficient. Further, in the above example, the combination of temperature differences is set at every step of 10 ° C., but the simulation can be similarly performed at any step such as 5 ° C. and 2 ° C .. By making the breaks finer, naturally more calculation processing is required, but more detailed thermal analysis is possible.

  In FIG. 10, if the optimum temperature difference Dp, Dr that minimizes the temperature variation ΔTmax is obtained in step # 10, the following is necessary by advancing the flow shown in step # 7 and subsequent steps of the flowchart shown in FIG. A simulation for obtaining the heating conditions can be performed. That is, the heating temperature difference D between the front and back that minimizes the temperature variation at the measurement point 3 is found by simulation according to the flow shown in FIG. 10 described below, and the following is the optimum that satisfies the requirements as in the previous embodiment. Suitable heating conditions can be found.

  Further, in the description so far, the heating temperature difference between the front and back in the preheating stage is 10 ° C., the temperature difference in the reflow stage is 20 ° C., and these are relatively simple simulation conditions in which these are combined in steps separated by 10 ° C. However, for example, the two heating zones VI and VII in the reflow stage are individually fluctuated in steps of 10 ° C. up to 20 ° C., and this is combined with three heating conditions including a heating temperature difference of 10 ° C. in the preheating stage. It is also possible to perform a more complicated simulation such as a simulation.

  In addition, only an example in which the heating temperature Tb on the back side is higher than the heating temperature Ta on the front side has been shown so far, but the heating temperature Ta on the front side may be higher depending on the heating purpose. The logic described above can also be applied in the same manner.

  Next, a third embodiment according to the present invention will be described. The present embodiment relates to a program for executing the thermal analysis described in the first and second embodiments by a computer, and a computer-readable storage medium storing the program.

The program and the storage medium basically include a procedure for implementing the thermal analysis method described in the previous two embodiments. That is, the first aspect of the program is
The temperature of the measurement points is measured by heating the sample to be heated under a certain heating condition and heating time without providing a heating temperature difference between the front and back surfaces, and the magnitude of temperature variation between the measurement points. A procedure for comparing to a predetermined threshold;
When the temperature variation is smaller than a predetermined threshold value, the procedure for obtaining the m value that is the heating characteristic value shown in Equation 8 from the heating condition and the measurement result at this time, or m similarly obtained The procedure to get the value,
When the temperature variation is larger than a predetermined threshold value, the temperature difference between the plurality of measurement points is reheated by providing a predetermined temperature difference between the front and back heating temperatures for heating the object to be heated. A procedure to confirm that the size falls within a predetermined threshold;
After the confirmation, from the heating conditions at this time and the measurement result, a procedure for obtaining the m value that is the heating characteristic value shown in Equation 8, or a procedure for obtaining the m value obtained in the same manner,
A procedure for setting a simulation heating condition of an object to be heated such as a circuit board and a heating device while maintaining a heating temperature difference (including 0) between the front and back sides;
A procedure for simulating a temperature profile by calculating a temperature for each measurement point of the circuit board from each of the set heating conditions and each of the obtained m values;
A procedure for confirming whether the simulation condition is a heating condition capable of clearing the required condition by comparing the simulation result with the required condition;
If the required conditions cannot be cleared, a procedure for repeating the simulation again by setting the next appropriate heating condition based on the confirmation result while maintaining the heating temperature difference (including 0) between the front and back sides;
If the required conditions can be cleared, a procedure for determining the result as a heating condition;
Even if heating is performed by providing a predetermined temperature difference between the heating temperatures of the front and back sides, the magnitude of temperature variation between a plurality of measurement points does not fall within the predetermined threshold, or as an option, the simulation If the number of repetitions exceeds a certain number of times, a procedure for outputting that it is impossible to set appropriate heating conditions;
Is configured to be implemented by a computer.

  The procedure described above is basically the same as that described in the first embodiment. Here, for example, in the case of reflow heating of lead-free solder, the predetermined temperature difference provided for the front and back heating temperatures is about 10 ° C. in the preheating stage and about 20 ° C. in the reflow stage. Set higher than the upper heating temperature. Further, the threshold value to be compared with the magnitude of temperature variation between the plurality of measurement points can be set to about 5 ° C. in the preheating stage and about 8 ° C. in the reflow stage in the case of reflow heating of lead-free solder, for example.

  This program can include an algorithm for the computer itself to select and set an appropriate simulation heating condition. The algorithm will be described in detail below. In the following procedure, reflow heating including a first heating stage (hereinafter referred to as a preheating stage) and a second heating stage (hereinafter referred to as a reflow stage) is described as an example. It is possible to apply the same algorithm to other thermal analysis.

For reference, the requirements for the object to be heated at this time are the same as those shown in the first embodiment below. References are indicated in parentheses in the description as necessary. To do.
a. Heating holding temperature and the same time (T2, t2): 220 ° C., 20 seconds or more.
b. Required temperature (Treq): 230 ° C
c. Heat-resistant limit temperature (Tmax): 240 degreeC
d. Heat-resistant upper limit temperature and the same time (T1, t1): 200 ° C., 40 seconds or less.
e. Preheating temperature and the same time (T0, t0): 160 ° C. to 190 ° C., 60 seconds to 120 seconds.

  It should be noted that other requirements are f. Reflow temperature variation (ΔTmax) and g. The preheating temperature variation (ΔT0) is excluded from the requirement for convenience in the following description. As described in the previous embodiment, sample heating is performed in a state where there is no temperature difference between the front and back heating sources, and it is checked whether the temperature variations ΔTmax and ΔT0 are within an allowable range. When one of them is not within the allowable range, a temperature difference is provided between the front and back heating sources, and the m value is calculated by performing sample heating again based on this heating condition. Acquisition of m value mentioned above means acquiring m value after calculating in this way.

  In step # 3 of the flowchart shown in FIG. 8, after heating the sample substrate and calculating the m value from the temperature measurement result in step # 6, the heating conditions for simulation are set in step # 7. By performing this, it is assumed that this heating condition clears the requirement for heating the object to be heated. In this flow, FIG. 11 shows a program procedure including an algorithm for the computer itself to find an appropriate heating condition for simulation.

  In FIG. 11, first, a heating characteristic value (m value) is obtained in step # 21. This is obtained in step # 1 to step # 6 shown in FIG. 8, and is obtained for a plurality of measurement points and a plurality of measurement positions. When there is a temperature difference in the heating source between the front and back, the m value obtained in a state where the temperature difference is provided is acquired. Next, from the measurement result at the time of sample heating or the calculation result by the simulation, the measurement point (this is based on the example shown in FIG. 4) at which the highest measurement temperature is obtained in the preheating stage which is the first heating stage in Step # 22. 3c). In step # 23, it is first confirmed at the highest measurement point 3c whether or not overheating exceeding the allowable upper limit of the temperature condition is caused by heating in the preheating stage (confirmation procedure A). If overshooting occurs here, it means that the heating temperature in the preheating stage exceeds the upper limit temperature (190 ° C.) for the preheating. In this case, correction of the heating condition for lowering the heating temperature is added in step # 24, a simulation is performed again in step # 25, and the process returns to step # 22 again to repeat the procedure so far. In addition, when the temperature difference is previously provided in the heating source between front and back, when the heating temperature is lowered, the temperature difference is maintained as it is. The same applies to all operations for raising and lowering the heating temperature described below. Further, hereinafter, unless otherwise specified, the heating temperature refers to a reference heating temperature on the front side (heating temperature by the upper heating source 7a in FIG. 1) Ta.

  One of the predetermined criteria for lowering the heating temperature in the preheating stage is to lower the heating temperature to an allowable upper limit temperature (190 ° C.) in the preheating stage. As other criteria, the temperature difference between the temperature based on the measurement result or the calculation result and the allowable upper limit temperature (190 ° C.) is calculated, and the temperature difference is multiplied by a certain ratio (including 1). It is to lower the heating temperature so far. By setting such a reference in advance, in step # 24, the computer itself can correct the heating temperature.

  Although not shown in the figure, if the measurement point having the highest measurement temperature extracted in step # 22 has not reached the lower limit temperature (160 ° C.) allowed for heating in the preheating stage, the step is reversed. In # 24, it is necessary to correct the heating condition for raising the heating temperature based on a predetermined standard. After that, simulation is performed again in step # 25, and the process returns to step # 22 again to repeat the procedure so far. In general, since the temperature of the object to be heated is the same as or lower than the heating temperature, it is generally difficult to set a heating temperature condition equal to or lower than the allowable lower limit temperature. Therefore, this is an emergency remedy. The predetermined standard for raising the heating temperature can be based on the standard for lowering the heating temperature described above.

  If the measurement point 3c does not exceed the preheating upper limit temperature in step # 23, it is confirmed in step # 26 that the preheating time t0 (60 seconds or more) has been reached (confirmation procedure B). If this is not cleared, a correction for increasing the heating temperature based on a reference determined in advance in step # 27 so that the object to be heated carried into the heating device can be raised to the preheating temperature (190 ° C.) earlier, or Correction for increasing the heating time (decreasing the conveyance speed) is performed according to a predetermined standard.

  FIG. 12 shows an example of a predetermined reference for increasing the heating temperature in step # 27. The figure shows the temperature profile of the object to be heated, with the vertical axis representing temperature and the horizontal axis representing time (from right to left). Time is shown in the course of heating zones I-VII. The objects to be heated carried into the heating device at the temperature Tr are sequentially heated in the first heating (preheating) stage of the heating zones I to V, and in the illustrated example, the preheating temperature T0 (160 to 160) is halfway through the heating zone III. 190 ° C.) and then held at this preheating temperature for time t. When the holding time t does not satisfy the required condition t0 (60 seconds) (t <t0), the heating zone before the heating zone (III in the illustrated example) that has reached the preheating temperature T0 is used as the reference. The heating conditions for increasing the heating temperature (I, II) by 1 ° C., for example, are corrected. The simulation is performed again based on the correction of the heating temperature, and if the holding time t does not yet satisfy t0 as a result, the temperature is again raised by 1 ° C. by the same operation, and this is repeated until t0 can be cleared. Note that the temperature range of 1 ° C. to be raised is arbitrary, and may be larger or smaller than this.

  As an example of a predetermined reference for increasing the heating time in step # 27, similarly, in FIG. 12, the ratio of the calculated time t to the required time t0 (t / t0, <1) is conveyed so far. It can be used as a criterion such as multiplying the speed or dividing the heating time so far by this ratio. It can be arbitrarily selected whether the heating condition or the heating time is used to correct the heating condition or both.

  Although not shown in FIGS. 11 and 12, when the preheating temperature holding time is over the required condition t0 (> 120 seconds), the heating temperature T0 (190 ° C.) is contrary to the above. By adding a correction to lower the heating temperature of each heating area before the heating area that has reached) by a predetermined standard, or by correcting to shorten the heating time in the preheating stage by a predetermined standard Can respond as well. The predetermined correction standard for lowering the heating temperature or shortening the heating time at this time can be based on the standard for increasing the heating temperature or increasing the heating time. . The time condition of the preheating stage is moderate, and it is usually unnecessary to perform correction in such a direction.

  If the highest temperature measurement point 3c can clear the preheating stage requirements in step # 26, then it is checked in step # 28 whether all other preheating temperatures and the same time have been cleared for the other measurement points. (Confirmation procedure C). Since the maximum temperature measurement point 3c has cleared the same condition, if there is a measurement point that has not been cleared, it means that the heating is insufficient. In this case, a correction is made to increase the heating time (decrease the conveying speed) or increase the heating temperature based on the reference determined in advance in step # 29, and return to step # 25 according to the new conditions after correction. Repeat the previous steps. As a predetermined reference in the correction in step # 29, for example, within the ratio (t / t0, <1) of the calculated time t to the required time t0 (60 seconds) of the measurement point that has not reached the time. A standard such as multiplying the previous conveyance speed by the value closest to 1 or dividing the previous heating time by the value closest to 1 is set in advance. Alternatively, when the heating temperature is increased, the temperature difference between the temperature of the measurement result or calculation result that does not satisfy the required lower limit temperature (160 ° C.) and the allowable lower limit temperature is calculated, and the maximum temperature difference is constant. A standard such as raising the heating temperature so far by a temperature obtained by multiplying the ratio (including 1) is determined in advance. As described above, when there is a temperature difference between the front and back surfaces, the temperature difference is maintained as it is.

  After it is confirmed that the requirements for the preheating stage, which is the first heating stage, are satisfied, the reflow process for the second heating stage, which requires stricter temperature control, is then performed. It is assumed that the heating conditions in the preheating stage up to step # 28 are determined, and the simulation result in the reflow stage performed based on the result is as shown in FIG. For simplification, only three measurement points 3a to 3c are used here. In the next step # 30, a measurement point indicating the minimum temperature is extracted from the measurement result or simulation result in the reflow stage. In the reflow process for the purpose of soldering, it is necessary to heat the solder to the required temperature (230 ° C) at which it becomes a complete liquid phase, and this requirement should be cleared even at the lowest temperature measurement point. Therefore, attention is first paid to the measurement point indicating the minimum temperature. In the example shown in FIG. 5 (c), the measurement point 3b (peak (maximum) temperature: 228.1 ° C.) corresponds to this (hereinafter referred to as “first reference measurement point 3b”). It shows that the first reference measurement point 3b does not satisfy the required ultimate temperature Treq (230 ° C.) which is one of the required conditions.

  As described above, when the first reference measurement point 3b does not clear the necessary temperature condition, it is necessary to cope with the direction of increasing the temperature. However, this means that the temperature of the profile indicating the highest temperature (measurement point 3c in the example shown in FIG. 5C) also rises, and this does not exceed the heat resistant limit temperature Tmax (240 ° C.). You have to keep that in mind. For this reason, when the temperature rise is corrected, the measurement point at the highest temperature in the simulation result in the reflow stage (hereinafter referred to as “second reference measurement point 3c”) is focused next. The profile of measurement points other than the first and second reference measurement points (measurement point 3a in the example shown in the figure) is the highest temperature result and the lowest temperature when the heating temperature condition correction operation described below is performed. Assume that it is sandwiched between both reference measurement points 3b and 3c showing the results.

  In step # 31 of FIG. 11, first, at least one heating condition is searched by simulation so that the first reference measurement point 3b having the lowest temperature satisfies the requirements for the reflow stage, which is the second heating stage. . As an example of the search method, the following algorithm using the heat-resistant limit temperature Tmax (240 ° C.) and the required ultimate temperature Treq (230 ° C.) among the required conditions can be used. FIG. 13A shows the outline, in which the vertical axis represents temperature and the horizontal axis represents time. Here, a case where a heating apparatus having two heating zones VI and VII is used in the reflow stage as shown in FIG. 1 is shown, and the object to be heated moves from the right to the left of the drawing in both heating zones as time passes. , VI, and VII.

  In FIG. 13A, while the first reference measurement point 3b heated to the preheating temperature T0 in the heating zones I to V in the preheating stage enters the preceding reflow heating zone VI and passes through the heating zones VI and VII. The target temperature range at the time of heating is indicated by a hatched region X. In this region X, the measurement point 3b carried into the start point H of the heating zone VI at the temperature T0 is moved to the point E along the temperature gradient line where the measurement point 3b is heated to the heat-resistant limit temperature Tmax before the end of the heating zone VI. Until the point G reaches the point G in the heating zone VII, and the measurement point 3b that has entered the starting point H of the heating zone VI at the preheating temperature T0 is required to reach the end of the heating zone VII. The region is surrounded by the lower limit reaching the point F along the temperature gradient line heated to the temperature Treq.

  If the temperature profile is included in this region X, the first reference measurement point 3b does not exceed at least the heat-resistant limit temperature Tmax and is heated to the necessary temperature Treq. It will be clear. In the example shown in the figure, the temperature gradient lines are formed by connecting the points H and E and the points H and F with straight lines, but these lines are curves that are convex upward or downward. Or any other combination of curves / straight lines as long as it does not exceed Tmax between point E and point F.

  The heating conditions of the heating zones VI and VII are determined by simulation using the m value so that the first reference measurement point 3b falls within such a region X. Specifically, in both heating zones VI and VII, the heating temperature can be varied from the preheating temperature (190 ° C.) to the equipment allowable temperature (eg 300 ° C.). The temperature profile of the measurement point 3b in all combinations when the heating temperature of each heating zone VI and VII is changed for each step is obtained by simulation using m values. And it searches for only the combination of the heating conditions which enter into field X from the simulation result. The step of 2 ° C. is optional, and may be a finer step or a coarser step.

  For example, when a temperature difference of 20 ° C. is provided between the heating temperatures of the front and back surfaces, the above-described variation in the heating temperature is such that the heating temperature of the front heating source is 170 ° C. to 280 ° C., for example, every 2 ° C. Corresponding to this, it is assumed that the variation is in steps of 2 ° C. from 190 ° C. to 300 ° C., respectively. The ultimate temperature Ts of the object to be heated at this time is obtained by first obtaining the local heating temperature Tx using the temperature difference coefficient R described in the second embodiment, and then, the local heating temperature Tx is heated by the equation 7 It can be calculated by substituting for Ta in the basic formula.

  Depending on the heating device, in the second heating stage, there may be only one heating zone VI or three or more heating zones VI, VII, VIII,. FIGS. 13B and 13C show setting examples of the region X in such a case. When there is one heating zone, the search for the heating conditions that fall within the region X shown in FIG. 13B is simulated in the heatable temperature range of the heating zone, for example, in 2 ° C. steps. When the number of heating zones is three (or more than three), for example, as shown in FIG. 13C, the upper limit of reaching the heat-resistant limit temperature Tmax at the end of the preceding heating zone VI and the end of the final heating zone VIII A region X surrounded by a lower limit that reaches the necessary reaching temperature Treq at a point is set, and the simulation is performed with all combinations of the heatable temperature ranges of the respective heating zones. However, the setting of the area X shown in FIGS. 13A to 13C is an example, and other area settings can be set as a matter of course. Also, the lines connecting the points H and E and the points H and F in the figure may not be straight lines, as described above.

  FIG. 14 shows a simulation result of each temperature profile of the first reference measurement point 3b with respect to the combination of heating temperatures searched in this way. In the figure, the temperature profile of only the reflow stage is shown. The figure shows a case where six heating conditions satisfying the region X are found from all combinations of heating temperatures with respect to the first reference measurement point 3b. Each profile already satisfies the requirements that the maximum temperature is Tmax or less and Treq or more, and the heating temperature in heating zones VI and VII, the heating temperature difference between the front and back, and the heating time are unambiguous for each profile. It has been determined in response to.

  Returning to FIG. 11, next, in step # 32, the profile of the found first reference measurement point 3b is one of the requirements of the other reflow stage, that is, the heating holding temperature and the same time T2, It is first confirmed whether t2 (220 ° C., 20 seconds or more) has been cleared (confirmation procedure D). If there is nothing to clear this condition, it means that the heating is insufficient. In this case, the heating condition is lengthened in accordance with the standard determined in advance in step # 33 (correcting the heating speed). And return to step # 25 to repeat the previous procedure.

  As an example of a predetermined reference when performing the correction to increase the heating time in Step # 33, the measurement result or calculation result corresponding to the heating holding temperature and the time requirement t2 (20 seconds) at the same time This is done by multiplying the time ratio (t / t2, <1) by the previous conveyance speed or by setting a standard such as dividing the previous heating time by this ratio.

  If there is one in which the profile of the first reference measurement point 3b has cleared the above condition in step # 32, then in step # 34, the other heat treatment upper limit temperature and the time between them are the other requirements of the reflow stage. It is confirmed whether the condition t1 (40 seconds or less) is cleared (confirmation procedure E). If there is nothing that satisfies this condition, it means that the heating is over. In this case, the heating time is shortened based on the reference determined in advance in step # 35 (the conveyance speed is increased). The heating condition is corrected, and the process returns to step # 25 to repeat the procedure so far. The predetermined standard in this case is, for example, the ratio (t / t1,> 1) of the time ratio (t / t1,> 1) corresponding to this in the heating condition that is not cleared with respect to the heat-resistant upper limit temperature and the time requirement t1 between the same. A value close to 1 is multiplied by the original transport speed, or the original heating time is divided by the value closest to 1 in advance.

  If there is one in which the profile of the first reference measurement point 3b clears the above condition in step # 34, the heating holding temperature and the time condition t2 (20 seconds or more) between them are the shortest among those cleared. The profile A (see FIG. 14) of the first reference measurement point 3b that is cleared in time is extracted. The first reference measurement point 3b is the lowest temperature when the sample is heated, and the heating conditions corresponding to the extracted profile A satisfy all the requirements of the reference measurement point 3b. The other measurement points 3a and 3c are assumed to be on the higher temperature side (upper side, that is, the side where the heat resistant upper limit temperature and the same time are longer) than the profile A. Therefore, the profile A on the lowest temperature side (that is, cleared in the shortest time) is extracted for the measurement point 3b, and the heating conditions in the heating zones VI and VII corresponding to this profile A are reflowed in step # 36. Temporarily set as heating conditions.

  Next, in step # 37, a simulation is performed using each m value for the temperature profile when all other measurement points are heated according to the temporarily set heating condition. In step # 38, based on the simulation result, it is confirmed whether or not each of the other measurement points satisfies the reflow stage requirements (confirmation procedure F). In this case, it is first checked whether the second reference measurement point 3c, which has shown the maximum temperature in the sample heating described above, has cleared all other required conditions such as the heat-resistant limit temperature Tmax. This is because, if the second reference measurement point 3c does not clear this, it can be determined that the temperature condition cannot be applied without confirming other measurement points.

  If it is confirmed by simulation that the second reference measurement point 3c satisfies the above conditions, the other measurement points are located between the temperature profiles of the first and second reference measurement points 3b and 3c. As such, they can also be assumed to clear the reflow stage requirements. However, regarding these other measurement points, it is preferable to perform a simulation in the same manner as necessary to confirm that the required conditions are satisfied.

  In this way, it is checked whether all the required conditions have been cleared for all the measurement points. If this clear can be confirmed, the heating conditions are determined in step # 39. On the other hand, if at least one measurement point that cannot satisfy the required conditions is found as a result of simulation for other measurement points in step # 38, the heating conditions need to be corrected again. At this time, since the first reference measurement point 3b having the lowest temperature in the sample measurement satisfies the required condition, it means that the measurement point that cannot be cleared is overheating. Therefore, in step # 35, correction is performed to shorten the heating time of the object to be heated on the basis of a predetermined reference (increase the conveyance speed), and the process returns to step # 25 to repeat the previous procedure again by setting new conditions.

  When performing the correction to shorten the heating time in Step # 35, the ratio of the simulation result corresponding to the heating holding temperature and the measurement point not cleared to the same time t2 (20 seconds) (t / t2, > 1), the ratio of the measurement point not cleared with respect to the heat-resistant upper limit temperature and the same time t1 (40 seconds) to the simulation result time corresponding to this (t / t1,> 1), or this This can be done by predetermining a criterion such as multiplying the ratio of the two ratios closest to 1 by the previous conveyance speed or dividing the heating time so far by the ratio closest to 1.

  As a result of the above procedure, if it is confirmed that the required condition in step # 38 is cleared, the final heating condition can be determined in step # 39. When the object to be heated is heated under this determined heating condition, it has been confirmed at least in the simulation that the requirements of both the first and second heating stages can be cleared at all measurement points. Although not described in the flow of FIG. 11, the sample to be heated is actually verified and heated under the same heating conditions, and each measurement point is measured to verify that the heating conditions are appropriate. You may do it.

  In addition, in step # 50 added to each confirmation procedure of FIG. 11, when the heating condition is corrected and the simulation is repeated without being able to meet the required condition, the number n of simulation repetitions in the same loop is counted. To do. If n exceeds a predetermined number of times, it is output in step # 51 that heating conditions cannot be set. This is an optional procedure that makes it possible to conclude in a short time that no heating conditions can be found that meet the given requirements. In the procedure for heating and verifying the sample to be heated according to the conventional technique, it is difficult to make such a determination in a short time. In the output of step # 51, it is preferable to output a calculation result including which required condition is not satisfied with respect to the required temperature in analyzing subsequent countermeasures.

  However, depending on the situation, it may not be concluded that the heating condition cannot be set, and even if the required condition is not satisfied, it may be desired to find an approximate heating condition. An algorithm as a countermeasure in such a case can be set as follows. FIGS. 15A to 15C show the heating and holding temperature (T2) and time in time (t2), the heat-resistant upper limit temperature (T1) and time in time obtained in the process of repeating the simulation according to the procedure shown in FIG. The calculation result of each measurement point 3a-3b corresponding to (t1) is shown. In the stage shown in FIG. 15A, the second reference measurement point 3c indicated by a circle does not satisfy the required condition of t1 (40 seconds or less), and step # 38 in FIG. 11 is not cleared. For this reason, it progresses to step # 35 and the simulation is repeated again after the heating condition correction | amendment which shortens heating time.

  FIG. 15B shows the result of the same content obtained by this second simulation. Looking at this result, although the heating time was corrected to be short, the previous second reference measurement point 3c cleared t1 (40 seconds), but this time the first reference measurement point 3b was t2 (20 seconds or more). The condition is no longer met. If the step of FIG. 11 is followed, step # 32 will not be cleared, but this time it will progress to step # 33, the condition correction | amendment which lengthens heating time will be added, and a simulation will be repeated again. However, according to this procedure, it is clear that the second reference measurement point 3c cannot clear the requirement of t1 (40 seconds or less) again by increasing the heating time. It will be repeated.

  FIG. 16 shows an approximate solution setting procedure in such a case. Although FIG. 16 shows only the second heating (reflow) stage of FIG. 11 for convenience, the first heating (preheating) stage may be added as in FIG. In the procedure shown in FIG. 16, steps # 52 to # 54 are added to the procedure of FIG. In FIG. 16, when the result of FIG. 15B is reached, since step # 32 is not cleared as described above, the process proceeds to step # 52, where the second reference measurement point 3c is the heat resistant upper limit temperature and the time between them. It is checked whether it is at the limit of t1 (within 40 seconds). The limit here means that the time requirement of t1 is 40 seconds, or it has already exceeded 40 seconds. If the second reference measurement point 3c is within the upper limit of the heat-resistant upper limit temperature and the time condition t1 during the same period, the process proceeds to step # 33 and correction is made to increase the heating time. It is clear that the above condition cannot be cleared. Here, advance to Step # 38 in advance, the second reference measurement point 3c cannot clear the heat resistant upper limit temperature and the time condition (t1) at the same time, and the correction to shorten the heating time in Step # 35 is performed. If step # 32 cannot be cleared when step # 25 and subsequent steps are repeated after the addition, it can be said that the second reference measurement point 3c is already at the limit in step # 52.

  In this case, the process proceeds to step # 53, and it is checked whether other required conditions are cleared except for the first reference measurement point 3b. This corresponds to step # 38 of the previous procedure. However, since the second reference measurement point 3c having the highest measurement temperature is at the limit, the other measurement points are assumed to be between the first and second reference measurement points 3b and 3c. Therefore, this step # 53 may be skipped as indicated by the broken line in the figure.

  If step # 53 is cleared, the process proceeds to step # 54 so that the first reference measurement point 3b can clear the condition of t2, and a correction for increasing the heating time by a predetermined reference is added. It is assumed that the final solution for setting the heating condition is determined in step # 39 with the heating condition. FIG. 15C shows a simulation result under this determined heating condition. By extending the heating time, the first reference measurement point 3b clears t2 (20 seconds or more). However, this time, the second reference measurement point 3c does not clear t1 (within 40 seconds). Particularly in the case of reflow heating, since the main purpose is to surely melt the solder, it is the result that the highest priority is to clear all measurement points at t2. If the purpose is different, for example, another algorithm that prioritizes t1 can be used. As a reference for the predetermined correction for increasing the heating time in step # 54, for example, the ratio of the required time of t2 and the calculation time of the measurement point 3b (t / t2, <1, in the example shown in FIG. 15B) , 18/20) is multiplied by the conventional conveying speed, or the heating time so far is divided by this ratio.

  When other measurement points do not clear the required conditions in step # 53, it is determined in step # 51 that the heating condition cannot be set for the first time. However, this is a matter of judgment. If an approximate solution is required in any form, the process proceeds to steps # 54 and # 39 without adding the check procedure of step # 53 as shown by the previous broken line. You may make it ask for a final solution.

  In the description so far with reference to FIG. 11, the program including the thermal analysis in the first heating stage and the second heating stage is targeted as the heating requirement, but in other cases, the program Application is possible. For example, in the heating in which only the required conditions of one heating stage are given, the heating conditions may be determined by performing either the first heating stage or the second heating stage shown in FIG. In addition, in heating in which different requirements are given to three or more heating stages, either one or both of the first and second heating stages are selectively repeated, and heating is performed. Conditions may be fixed.

  In the flow shown in FIG. 11, the required conditions cannot be cleared in the second heating stage, and if the heating conditions are changed in step # 33 or step # 35, the subsequent process returns to step # 25 and returns to the first. The simulation from the heating stage is repeated. On the other hand, for example, a heating device of a type in which the heating conditions including the heating time (or the conveyance speed of the object to be heated) can be independently controlled between the first heating stage and the second heating stage is used. Then, as shown by the broken line in FIG. 11, without returning the flow to step # 25 of the first heating stage, a simulation is performed in which only the heating conditions in the second heating stage are changed in step # 41, It is possible to repeat only the flow of the second heating stage after step # 30.

  In the procedure described so far, only one required condition of the object to be heated, such as the heat-resistant limit temperature Tmax, the heat-resistant upper limit temperature and the same time T1, t1, is set for the entire circuit board as the object to be heated. I am going to do it. This means that when multiple electronic components are subject to temperature control, if the most severe thermal requirements of the electronic components are the minimum conditions that the circuit board should clear, It is based on the premise that it will not cause a problem. On the other hand, individual requirement conditions can be input separately for each measurement point, and this can be used as an auxiliary criterion. When the heating conditions are very severe thermally, the heat-resistant limit temperature (for example, 240 ° C.) set for the circuit board is exceeded (for example, 245 ° C.) at one of the measurement points (that is, the electronic component). Even if it becomes, if the said electronic component is provided with the heat-resistant allowable temperature (for example, 250 degreeC) exceeding this, it can also be judged that the said heating conditions are permissible. In particular, when a heating condition that satisfies the required conditions cannot be found, setting such a relief logic is advantageous in setting the heating condition.

  In the above description, reflow heating is taken as an example, and here, the object to be heated is transported by the transport device of the heating device, so that long and short heating times are interchangeably expressed as fast and slow transport speeds. is doing. For example, in a heating apparatus that does not have a transport apparatus such as a batch processing apparatus, the transport speed is not relevant. Therefore, in this case, the heating time while being held at a predetermined temperature in the heating apparatus is subject to heating conditions.

Next, a second aspect according to the present embodiment relates to a program including a logic for finding an appropriate heating temperature difference between the front and back sides by simulation. This program
Heating the sample to be heated under a certain heating condition that does not provide a heating temperature difference between the front and back and heating time, and measuring each temperature at the multiple measurement points. A procedure for obtaining the m value which is the heating characteristic value shown in FIG. 8, or a procedure for obtaining the m value obtained in the same manner;
Next, a predetermined temperature difference is provided between the front and back of each of the first heating stage and the second heating stage, and the sample to be heated is heated again under the heating conditions including the temperature difference, and a plurality of samples are heated. Measuring each temperature at each measurement point, and calculating the local heating temperature in the vicinity of each measurement point using the revised heating basic formula (formula 11);
Between the heating temperature of any one of the front and back heating sources and the calculated local heating temperature, an index of the degree of heating influence on the local heating temperature of the reference heating source A procedure for obtaining a temperature difference coefficient;
The simulation heating condition concerning the arbitrary combination which changed the temperature difference of the 1st heating stage (preheating stage) and the temperature difference of the 2nd heating stage (reflow stage) for every predetermined fixed temperature step Steps to set,
A procedure for performing a simulation to find a temperature profile of each measurement point using the heating basic equation (Equation 7) from the simulation heating conditions and the local heating temperature calculated based on the temperature difference coefficient,
From the simulation results, a procedure for finding the most suitable heating temperature for the heating purpose,
Is configured to be implemented by a computer.

  The above contents are basically the same as those described in the second embodiment. Here, for example, in the case of reflow heating of lead-free solder, a predetermined value provided between the front and back surfaces is determined. The temperature difference can be about 10 ° C. in the preheating stage and about 20 ° C. in the reflow stage. Further, the calculation formulas for obtaining the local heating temperature and the temperature difference coefficient are the same as the formulas 11, 12, and 13 shown in the second embodiment. In addition, it is sufficient that the predetermined temperature difference with respect to the temperature difference for setting the simulation heating condition is about 10 ° C. units, or about 5 ° C. units at most.

By performing a simulation based on the above logic, for example, the optimum temperature difference between the front and back sides can be found in order to minimize the temperature variation (ΔTmax) between the measurement points. By changing the heating temperature while keeping the temperature difference between the heating sources constant, the procedure shown in step # 22 and subsequent steps in FIG. 11 can be similarly performed.
In the above-described procedure, the heating temperature difference that minimizes the temperature variation ΔTmax between the measurement points is obtained, but this is applied in the case of reflow heating, and the heating purpose is different. It is also possible to select other desired heating temperature differences from the results obtained by simulation. For example, even if the purpose of the simulation is to find a heating temperature difference that minimizes the temperature variation ΔT0 in the preheating stage, or extremely, to find a heating temperature difference that maximizes the temperature variation ΔTmax, these requirements are satisfied. The most suitable heating temperature difference between front and back can be selected.

  The program of each aspect according to the present embodiment has been described above. The storage medium described at the beginning is a computer-readable storage medium storing the above-described programs for executing the procedures described so far. Say.

  Next, a fourth embodiment according to the present invention will be described. In the present embodiment, the temperature of the heating apparatus using the thermal analysis apparatus that performs the thermal analysis method described in the first and second embodiments and the program or recording medium described in the third embodiment is used. The present invention relates to a heating control device that performs control, and a heating device that uses the heating control device. FIG. 1 is also an example of a heating device according to the present embodiment. In the figure, the heating device 10 includes a plurality of superheating zones I to VII, and each heating zone includes heating sources 7a and 7b capable of individually controlling the heating temperatures on the front and back sides. The article to be heated 1 is carried into the heating device 10 by the transport device 8 and heated along a temperature profile that meets predetermined requirements while passing through the heating zones I to VII.

  A heating control device 20 is connected to or integrally formed with the heating device 10, and the heating control device 20 can control the heating temperature for each heating zone I to VII and the conveyance speed of the object to be heated. . The heating control device 20 can calculate the m value that is the heating characteristic value described in the previous embodiment, based on the measured temperature obtained by heating the sample substrate 1. Further, based on the calculated m value, a heating condition suitable for the input required condition can be calculated, and the heating condition of the heating apparatus 10 can be controlled according to the calculation result. At this time, the heating control device 20 can use the recording medium 30 on which the program exemplified in the third embodiment is recorded.

  FIG. 17 is a schematic block diagram of the heating control device 20 according to such a configuration. The heating control apparatus 20 includes an input unit 28, to which heating conditions including a heating temperature 21 and a heating time 22 as well as a required condition 27 of an object to be heated can be input. Apart from this, when calculating the heating characteristic value (m value), the measurement temperature result 23 when the sample substrate 1 is heated by the heating device 10 is inputted. The heating control device 20 includes a memory unit 24. In the memory unit 24, a heating basic equation (Equation 7) for calculating the temperature of the object to be heated, an m value calculation equation (Equation 8) that is a heating characteristic value, and the like are stored in advance. Can be remembered. Furthermore, the calculation means 25 can calculate the m value based on these pieces of information, and can further simulate the temperature corresponding to the corrected heating condition by using the calculated m value. . In addition, when a temperature difference is provided between the heating sources on the front and back sides, the calculation unit 25 uses the local heating described in the second embodiment based on the heating temperature 21 and the measurement temperature 23 including the temperature difference. Calculation of temperature and temperature difference coefficient is also possible.

  The heating control device 20 is further provided with a recording medium reading means 29, and using the algorithm of the program recorded on the recording medium 30, finds the heating condition suitable for the required condition based on the simulation result, and outputs it to the output means 26. The heating device 10 can be controlled by outputting from. As the recording medium 30 in this case, the recording medium described in the second embodiment can be used. Further, when a temperature difference is provided between the front and back heating sources, the program logic recorded on the recording medium 30 is used based on the data regarding the sample substrate obtained by heating the temperature difference. A simulation can be performed to determine the optimum heating temperature difference between the front and back surfaces that satisfies the allowable temperature variation at the measurement points.

  FIG. 17 is provided with the function of controlling the heating device 10 by the output means 26 as described above, but does not include such an output means 26 for control purposes, and the input from the input means 28 and the memory means. 24. A thermal analysis device that calculates a heating characteristic value based on the information recorded in 24, and simulates the temperature of the object to be heated corresponding to the input heating condition using the calculated heating characteristic value It can also be used as Furthermore, it is possible to provide a thermal analysis apparatus that includes a recording medium reading unit 29 as necessary, and that also performs a temperature simulation according to a predetermined algorithm by reading the recording medium described in the second embodiment. it can.

  The present invention is useful for efficiently finding out appropriate heating conditions for performing solder reflow heating in a short time, particularly in the technical field of component mounting, and in addition, other heating conditions that satisfy a required temperature profile are also provided. This is useful for thermal analysis such as when obtaining by simulation or when obtaining a temperature profile of an object to be heated obtained by given heating conditions. More specifically as examples other than reflow heating, heat treatment devices used for heat treatment of steel materials, sintering devices used for heating sintered alloys, firing devices used for firing ceramic materials, etc., melting various materials It is required to heat an object to be heated along a predetermined temperature profile for various heating devices that require temperature control and management, such as a melting device used for incineration or an incineration device used for incineration of waste materials. It can be widely applied in certain industrial fields.

It is explanatory drawing which shows the typical temperature profile heated with the reflow apparatus which can apply the thermal analysis method concerning embodiment of this invention, and the said reflow apparatus. It is explanatory drawing which shows the relationship of the heat transfer between a heating apparatus and a to-be-heated material. It is a perspective view which shows the to-be-heated material sample and the condition of the temperature measurement in each measurement point. It is explanatory drawing which shows the measurement position of the heating characteristic value (m value) in 1 heating area of a heating apparatus. It is a table | surface which shows the experimental result 1 of the simulation by the thermal-analysis method concerning embodiment of this invention. It is a graph which shows the other temperature profile calculated | required as a result of the simulation by the thermal analysis method concerning embodiment of this invention. It is a graph which shows the temperature profile calculated | required as a result of the simulation by the thermal analysis method concerning embodiment of this invention. It is a flowchart which shows the procedure of the thermal analysis method concerning embodiment of this invention. It is the experimental result which calculated | required the relationship between the hot air speed in a convection heating, and a heating characteristic value. It is a flowchart which shows the procedure of the thermal analysis method concerning other embodiment of this invention. It is a flowchart which shows the implementation procedure of the program which concerns on further another embodiment of this invention. It is explanatory drawing which shows the reference example of the heating condition correction | amendment in the 1st heating step of the program shown in FIG. It is explanatory drawing which shows the algorithm which finds the heating conditions in the 2nd heating step of the program shown in FIG. FIG. 12 is another explanatory diagram showing an algorithm for finding the heating condition in the second heating stage of the program shown in FIG. 11. It is a table | surface which shows the example of the calculation result obtained by the thermal analysis which concerns on this invention. It is a flowchart which shows the alternative procedure of the 2nd heating step of the program shown in FIG. It is a schematic block diagram of the heating control apparatus and thermal analysis apparatus which concern on other embodiment of this invention.

Explanation of symbols

1. 2. object to be heated (circuit board); 3. Parts (measurement points) 5. Temperature measuring device (thermocouple) Recording device, 7a, 7b. Heating source, 8. 10. transport device; 10. heating device (reflow device); Cooling device, 20. 30. heating control device; recoding media.

Claims (9)

A heating device having a heating source for heating the object to be heated from the front and back, at least one arbitrary measurement position at different measurement temperatures, a heating time at the measurement position, and a temperature at at least one arbitrary measurement point of the object to be heated measurement results and based on the heating characteristics including physical properties of the object to be heated and the heating device, wherein at each measurement position and thermal analysis how to quantify as a constant for each measurement point,
When the heating temperature of the heating source serving as the reference of either the front or back at the measurement position is Ta, the initial temperature of the measurement point at the measurement position is Tint, the ultimate temperature is Ts, and the heating time at the measurement position is t , The quantified result is

The thermal analysis method characterized by being m value represented by these.   2. The heat according to claim 1, wherein the numerical result is used to simulate a temperature profile of an object to be heated that is heated by the heating device according to heating conditions including different heating temperatures. analysis method.   Using the numerical results, heating conditions including different heating temperatures of the heating device for heating an object to be heated carried in the heating device along a temperature profile that conforms to predetermined requirements. The thermal analysis method according to claim 1, wherein the thermal analysis method is found.   The heating device is composed of a plurality of heating zones, and includes heating with different heating temperatures for heating an object to be heated that passes through the plurality of heating zones along a temperature profile that meets a predetermined requirement. The thermal analysis method according to claim 3, wherein a condition is found for each heating area using the results digitized for at least one measurement position in each heating area.   Using the numerical results, the most suitable heating source on the front and back sides to satisfy the requirements including allowable temperature variations between a plurality of measurement points of an object to be heated that is carried into the heating device and heated The thermal analysis method according to claim 1, wherein the heating temperature is found by simulation. Using the m value,
Ts = Ta- (Ta-Tint) e ^-Mt   (However, e is the base of natural logarithm)
The heating temperature Ta and the heating time t of the heating device for satisfying the given temperature Ts of the object to be heated are obtained based on the heating basic formula represented by: or the heating temperature of the given heating device The thermal analysis method according to claim 1, wherein an ultimate temperature Ts of an object to be heated is obtained using Ta and a heating time t. In order to find the most suitable heating temperatures different from each other in order to satisfy the requirements including the allowable temperature variation between the plurality of measurement points of the object to be heated, the heating device is close to the measurement points by the different heating temperatures of the front and back surfaces. The local heating temperature to be formed and a temperature difference coefficient that is an index of the degree of influence of the both heating temperatures on the local heating temperature are calculated using the m value. Thermal analysis method. When the local heating temperature is Tx, the heating temperatures of the front and back heating sources are Ta, Tb (Ta <Tb), and the temperature difference coefficients corresponding to the heating sources are Ra, Rb, the local heating temperature Tx, each temperature The difference coefficients Ra and Rb are respectively:

The thermal analysis method according to claim 7, wherein The m value is corrected based on the relationship between the hot air blowing speed obtained in advance and the m value when the hot air blowing speed of the heating device is changed. The thermal analysis method according to any one of the above.

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