WO2020250876A1

WO2020250876A1 - Temperature prediction device and temperature prediction method

Info

Publication number: WO2020250876A1
Application number: PCT/JP2020/022642
Authority: WO
Inventors: 真次朝山; 信二福
Original assignee: 三菱電機株式会社
Priority date: 2019-06-13
Filing date: 2020-06-09
Publication date: 2020-12-17
Also published as: JP7329973B2; CN113906835A; JP2020201204A

Abstract

In the present invention, any decrease in the accuracy of temperature prediction in a heating device is minimized while the interior of the heating device can be modeled in a simpler manner. A relational expression is used that defines, using a heat transfer coefficient, the relationship between: the difference between the temperature of an article being heated at a measurement site and the temperature of the air surrounding the measurement site; and the temperature difference of the article being heated at the measurement site over time. The relational expression is used to determine the heat transfer coefficient so that there is no difference between the temperature of air at the position of the measurement site at a specific time (ts), and the temperature of air corresponding to the position of the measurement site at the specific time (ts) in a set temperature distribution (12) of the heating device. Using a measurement temperature profile (13) and the relational expression, a temperature distribution (14) of air in the transport process is predicted.

Description

Temperature prediction device and temperature prediction method

The present disclosure relates to a temperature prediction device and a temperature prediction method for predicting the temperature of a part to be heated moving in the heating device.

Conventionally, a temperature prediction device and a temperature prediction method for predicting the temperature of a part to be heated moving in the heating device are known. For example, Japanese Patent No. 4226855 (Patent Document 1) describes the heating temperature and the measurement temperature of the object to be heated at the measurement position where the object to be heated passes in the transport direction of the substrate (object to be heated) moving in the heating device. A temperature prediction method for calculating a heating characteristic value for each measurement position is disclosed using and. In the temperature prediction method, the temperature profile of the object to be heated is predicted when the heating conditions of the heating device are changed by using the heating characteristic value for each measurement position. According to the temperature prediction method, it is possible to efficiently find the heating conditions of the heating device for heating the object to be heated according to the temperature profile suitable for the predetermined required conditions.

Japanese Patent No. 4226855

Inside the heating device, in addition to heat transfer between the object to be heated and air due to hot air circulation, multiple thermodynamic phenomena such as radiant heat from the inner wall of the heating device and heat conduction in the object to be heated are superimposed. Is occurring. Since it is difficult to accurately model the inside of the heating device, it is necessary to simplify the modeling of the inside of the heating device to some extent in the temperature prediction inside the heating device. However, according to the simplified model, the accuracy of temperature prediction in the heating device can be reduced.

The present disclosure has been made to solve the above-mentioned problems, and an object thereof is to suppress a decrease in accuracy of temperature prediction in a heating device while simplifying modeling of the inside of the heating device. Is.

The temperature predictor according to one aspect of the present disclosure predicts the temperature inside the heating device that heats the object to be heated. The heating device transfers air having a set temperature corresponding to the position according to the first set temperature distribution showing the relationship between each of the plurality of positions in the transfer process in which the object to be heated moves and the temperature of the air at the position. Blow towards. The temperature prediction device includes a control unit and a storage unit. In the storage unit, a first measurement temperature profile showing the relationship between the measurement temperature and the measurement time of the measurement site of the object to be heated moving in the heating device is stored. The control unit uses the heat transfer coefficient to define the relationship between the temperature of the object to be heated at the measurement site and the temperature of the air around the measurement site, and the temperature difference of the object to be heated at the measurement site over time. The heat transfer coefficient is set so that there is no difference between the temperature of the air at the position of the measurement site at the specific time and the temperature of the air corresponding to the position of the measurement site at the specific time in the first set temperature distribution. decide. The control unit predicts the temperature distribution of air in the transport process using the first measurement temperature profile and the relational expression.

The temperature prediction method according to another aspect of the present disclosure predicts the temperature inside the heating device that heats the object to be heated. The heating device transfers air having a set temperature corresponding to the position according to the first set temperature distribution showing the relationship between each of the plurality of positions in the transfer process in which the object to be heated moves and the temperature of the air at the position. Blow towards. The temperature prediction method includes a step of generating a first measurement temperature profile showing the relationship between the measurement temperature and the measurement time of the measurement site of the object to be heated moving in the heating device. The temperature prediction method uses the heat transfer coefficient to determine the relationship between the temperature of the object to be heated at the measurement site and the temperature of the air around the measurement site, and the temperature difference of the object to be heated at the measurement site over time. Using the defined relational expression, the heat transfer coefficient so that there is no difference between the temperature of the air at the position of the measurement site at the specific time and the temperature of the air corresponding to the position of the measurement site at the specific time in the first set temperature distribution. Includes steps to determine. The temperature prediction method includes a step of predicting the temperature distribution of air in the transport process using the first measurement temperature profile and the relational expression.

The temperature prediction device and the temperature prediction method according to the present disclosure relate the difference between the temperature of the object to be heated at the measurement site and the temperature of the air around the measurement site, and the temperature difference of the object to be heated at the measurement site over time. With the relational expression defined using the heat transfer coefficient, the temperature of the air at the position of the measurement site at a specific time and the temperature of the air corresponding to the position of the measurement site at the specific time in the first set temperature distribution. By determining the heat transfer coefficient so that there is no difference, it is possible to suppress a decrease in the accuracy of temperature prediction in the heating device while simplifying the modeling inside the heating device.

It is external perspective view of the control device of the reflow furnace which is an example of the heating device which concerns on Embodiment 1, and the reflow furnace which is an example of a temperature prediction device. It is a functional block diagram which shows the structure of the control device of FIG. It is a figure which shows the internal structure of the reflow furnace of FIG. It is a flowchart which shows an example of the process of temperature prediction performed by the control device of FIG. It is a figure which shows the state that the data logger is connected to the printed circuit board of FIG. 3 via a thermocouple. It is a time chart for explaining the smoothing process of a measurement temperature profile. It is a figure which shows the set temperature distribution, the smoothed measurement temperature profile, and the temperature distribution in a furnace together. It is a figure which also shows the set temperature distribution of FIG. 7, the temperature distribution in a furnace, and the corrected set temperature distribution. It is a figure which shows the simulation result of temperature prediction. It is a flowchart which shows an example of the process of temperature prediction performed by the temperature prediction apparatus which concerns on Embodiment 2. FIG. It is a flowchart which shows another example of the process of temperature prediction performed by the temperature prediction apparatus which concerns on Embodiment 2. FIG.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In principle, the same or corresponding parts in the drawings are designated by the same reference numerals and the description is not repeated.

Embodiment 1.
FIG. 1 is an external perspective view of a reflow furnace 100 which is an example of a heating device according to the first embodiment and a control device 30 of a reflow furnace 100 which is an example of a temperature prediction device. In FIG. 1, the X-axis, Y-axis, and Z-axis are orthogonal to each other. The same applies to FIGS. 3 and 5 described later.

As shown in FIG. 1, the reflow furnace 100 is provided with an inlet portion 110 and an outlet portion 120. The reflow furnace 100 is a heating device having a tunnel-type transfer process. The object to be heated is charged into the conveyor inside the reflow furnace 100 from the inlet 110. Inside the reflow furnace 100, the object to be heated moving on the conveyor is heated.

The control device 30 controls, for example, the temperature inside the reflow furnace 100, the amount of air blown by the heating mechanism, and the transfer speed of the transfer conveyor. The object to be heated is, for example, a printed circuit board in which a plurality of mounting components are arranged by solder paste. The solder paste is a paste obtained by adding flux to solder powder to have an appropriate viscosity, and is also called cream solder. Examples of the mounting components soldered on the printed circuit board include passive element components such as ceramic capacitors, semiconductor chips on which active elements such as transistors are formed, and integrated circuits in which these are integrated. it can.

FIG. 2 is a functional block diagram showing the configuration of the control device 30 of FIG. As shown in FIG. 2, the control device 30 includes a processing circuit 31 (control unit), a memory 32 (storage unit), an input / output unit 33, and a display unit 34. The processing circuit 31 includes a low-pass filter 310. The processing circuit 31 may include dedicated hardware, or may include a CPU (Central Processing Unit) that executes a program stored in the memory 32. When the processing circuit 31 includes dedicated hardware, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Applicatomy Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), Alternatively, a combination of these corresponds to the processing circuit 31. When the processing circuit 31 includes a CPU, the function of the control device 30 is realized by software, firmware, or a combination of software and firmware. The CPU is also called a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, or a DSP (Digital Signal Processor).

Software or firmware is described as a program and stored in the memory 32. The memory 32 stores a program of control software and a program of temperature prediction software for controlling the temperature in the reflow furnace 100, the blower control, and the drive speed control of the conveyor. The processing circuit 31 executes the program stored in the memory 32. The memory 32 includes a non-volatile or volatile semiconductor memory (for example, RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), or EEPROM (Electrically Erasable Programmable Read Only Memory). )), And magnetic discs, flexible discs, optical discs, compact discs, mini discs, or DVDs (Digital Versatile Disc) are included.

FIG. 3 is a diagram showing the internal configuration of the reflow furnace 100 of FIG. As shown in FIG. 3, the reflow furnace 100 includes a transfer conveyor 2, heating mechanisms 41 to 47, 51 to 57, temperature sensors Sa1 to Sa7, Sb1 to Sb7, and

cooling mechanisms

61 and 62.

The heating mechanisms 41 to 47 and the cooling mechanism 61 are arranged at intervals in this order from the inlet portion 110 to the outlet portion 120. The heating mechanisms 51 to 57 and the cooling mechanism 62 are arranged at intervals in this order from the inlet portion 110 to the outlet portion 120. The heating mechanisms 41 to 47 face the heating mechanisms 51 to 57 in the Z-axis direction, respectively. The cooling

mechanisms

61 and 62 face each other in the Z-axis direction.

The transfer conveyor 2 is arranged between the heating mechanisms 41 to 47 and the heating mechanisms 51 to 57 along a transfer process extending from the inlet portion 110 to the outlet portion 120. The transfer direction of the transfer conveyor 2 is the direction indicated by the arrow 3. Each of the heating mechanisms 41 to 47 and 51 to 57 heats the air to the temperature set by the control device 30 and blows the air toward the conveyor 2. Each of the cooling

mechanisms

61 and 62 cools the air to the temperature set by the control device 30 and blows the air toward the conveyor 2. The temperatures of the air blown from the heating mechanisms 41 to 47 and 51 to 57 are measured by the temperature sensors Sa1 to Sa7 and Sb1 to Sb7, respectively, and output to the control device 30.

The control device 30 controls the temperature (set temperature) of the air blown by the heating mechanisms 41 to 47, 51 to 57 and the amount of air blown per unit time. The control device 30 controls the transfer speed of the transfer conveyor 2. The control device 30 sets the set temperatures of the two heating mechanisms facing each other in the Z-axis direction to the same temperature. The control device 30 sets the set temperatures of the cooling

mechanisms

61 and 62 to the same temperature.

The inside of the reflow furnace 100 is divided into a plurality of sections Sc1 to Sc9 along the conveyor 2. The section Sc1 is a section through which the printed circuit board 1 (first object to be heated) inserted into the inlet 110 first passes. In the sections Sc1 to Sc8 (plurality of heating sections), heating mechanisms 41 to 47 are arranged and heating mechanisms 51 to 57 are arranged, respectively.

Cooling mechanisms

61 and 62 are arranged in the section Sc9.

The printed circuit board 1 moves from the inlet portion 110 to the outlet portion 120 at the transfer speed of the transfer conveyor 2. The printed circuit board 1 is soldered by being heated in the transport process. At the point to be soldered, it is necessary to raise the temperature above the melting temperature of the solder. In addition, the mounting components that make up the circuit have an allowable heat resistant temperature. Therefore, if the temperature rises beyond the heat-resistant temperature of the mounted component, there is a risk that the mounted component may malfunction. That is, the temperature inside the reflow furnace 100 must satisfy the condition that the temperature is equal to or higher than the melting temperature of the solder and lower than the heat resistant temperature.

For example, when the melting temperature of the solder is 217 ° C and the heat resistant temperature of the mounted component is 240 ° C, the condition is satisfied if the entire printed circuit board 1 is uniformly heated to 230 ° C. However, since the mounting components made of various materials are unevenly arranged on the printed circuit board 1, the rate of temperature increase differs between the portion where the temperature rises easily and the portion where the temperature rise is difficult. It is required to predict the temperature of the printed circuit board 1 in the transfer process in the reflow furnace 100 with high accuracy in advance so that the condition is satisfied in the actual manufacturing process.

Inside the reflow furnace 100, in addition to heat transfer between the object to be heated and air by hot air circulation, a plurality of thermodynamic phenomena such as radiant heat from the inner wall of the reflow furnace 100 and heat conduction in the object to be heated are present. Are superimposed. Since it is difficult to accurately model the inside of the reflow furnace 100, it is necessary to simplify the modeling of the inside of the reflow furnace 100 to some extent in the temperature prediction inside the reflow furnace 100. However, according to the simplified model, the accuracy of temperature prediction in the reflow furnace 100 can be reduced.

Therefore, in the reflow furnace 100, the temperature profile of the printed circuit board 1 moving in the transfer process is measured in advance. The control device 30 calculates the temperature distribution of the air in the reflow furnace 100 from the temperature profile using a relatively simple physical law such as Newton's law of cooling, and the printed circuit board 1 at a certain sampling time. The heat transfer coefficient of the measurement site is determined so that the temperature of the air at the position of the measurement site approaches the set temperature of the heating mechanisms 41 to 47, 51 to 57 corresponding to the position. The control device 30 predicts the temperature of the printed circuit board 1 using the heat transfer coefficient. According to the control device 30, it is possible to suppress a decrease in the accuracy of temperature prediction in the reflow furnace 100 while simplifying the modeling of the inside of the reflow furnace 100.

FIG. 4 is a flowchart showing an example of the temperature prediction process performed by the control device 30 of FIG. As shown in FIG. 4, the temperature prediction process proceeds in the order of S101 to S107. The temperature of the object to be heated is measured in S101. The temperature profile (measurement data) measured in S101 is stored in the memory 32 of the control device 30. In S102, the measurement data is read into the temperature prediction software. In S103, the set temperature distribution of the heating mechanisms 41 to 47, 51 to 57 when the temperature profile was measured in S101 (relationship between each of the plurality of positions in the transfer process and the temperature of the air at that position) and the transfer conveyor 2 The transport speed of is input to the control device 30. In S103, the set temperature distribution and the transfer speed input to the operation unit of the reflow furnace 100 may be referred to when performing S101. In S104, the temperature distribution in the reflow furnace 100 (temperature distribution in the furnace) is predicted. In S105, the heat transfer coefficient for each measurement site of the object to be heated is calculated. The set temperature distribution is corrected in S106. In S107, the temperature profile of the measurement site of the object to be heated is predicted (simulated) when the set temperature distribution corrected in S106 is changed. Hereinafter, the processing contents of S101 to S107 will be described in detail.

In the reflow furnace 100, how the temperature of the object to be heated changes in the transport process in a state where the heating mechanisms 41 to 47, 51 to 57 blow air according to a certain set temperature distribution (first set temperature distribution). Measured in advance. The set temperature distribution in the reflow furnace 100 indicates the correspondence between the plurality of heating mechanisms and the plurality of set temperatures. For example, in a certain set temperature distribution, the set temperatures of the heating mechanisms 41 to 47 are set to T1 to T7, respectively, and the set temperatures of the heating mechanisms 51 to 57 are set to T1 to T7, respectively. As the set temperature distribution used in the temperature measurement of the object to be heated, the set temperature distribution used when another object to be heated having a shape similar to the shape of the object to be heated is heated in the past should be used. Can be done. In the temperature measurement of the object to be heated, it is not necessary to use the optimum set temperature distribution for the object to be heated.

FIG. 5 is a diagram showing how the data logger 8 is connected to the printed circuit board 1 of FIG. 3 via

thermocouples

71 and 72. In S101 of FIG. 4, the printed circuit board 1 and the data logger 8 move in the transfer process of the reflow furnace 100 in the state shown in FIG. As shown in FIG. 5, mounting components 81 to 83 are arranged on the printed circuit board 1. One end of each of the

thermocouples

71 and 72 is connected to the data logger 8. The other end of the thermocouple 71 is connected to the measurement site P1 of the mounting component 81. The other end of the thermocouple 72 is connected to the measurement site P2 of the printed circuit board 1. In the data logger 8, the sampling time (measurement time) and the measurement temperature of each of the measurement sites P1 and P2 are stored in association with each other for each sampling time. The data logger 8 creates a measurement temperature profile of the measurement site P1 (first measurement temperature profile) and a measurement temperature profile of the measurement site P2 (first measurement temperature profile).

It is desirable to select a part of the printed circuit board 1 that requires precise temperature control as the measurement part. Examples of the portion include a part having the lowest heat resistant temperature and easy to heat, or a soldered portion having the least heat resistance. An appropriate location as a measurement site can be selected from the material of the mounting component or the arrangement of the wiring pattern of the printed circuit board 1. When it is difficult to limit the number of measurement sites to one, it is desirable to select a plurality of measurement sites (for example, 5 to 6 points). For example, the body heat temperature of a resin connector or the heat-resistant temperature of an aluminum electrolytic capacitor is often relatively low, so a thermocouple is attached to the body of these parts, and the temperature reached by heating is below the heat-resistant temperature. It is desirable to confirm. Alternatively, the soldered portion of the component relatively close to the conveyor 2 may receive insufficient heat from the heating mechanism, and a thermocouple is attached to the soldered portion to obtain the melting temperature required for soldering and the melting temperature. It is desirable to confirm that the melting time has been reached. The measurement site is not limited to the above-mentioned location, and any site of the printed circuit board 1 can be used as the measurement site. Further, it is not necessary to have a plurality of measurement sites, and one of the most characteristic points of the object to be heated may be selected as the measurement site.

The measured temperature profile measured by the data logger 8 is stored in the memory 32 of the control device 30 of FIG. Further, the set temperature distribution when the measurement temperature profile is created and the transfer speed of the transfer conveyor 2 are input to the control device 30. The processing circuit 31 smoothes the measurement temperature profile.

Generally, in the data logger 8, the measured temperature is converted into a discrete value for each sampling time according to the resolution of the temperature measurement and recorded in the measured temperature profile (discrete temperature profile). The sampling time interval is preferably a value of 0.1 s to 1 s. Further, the resolution of the measurement temperature is preferably a value of 0.1 ° C. to 1 ° C. Further, in the main body of a general reflow furnace, the outlets of the heating mechanism are provided at equal intervals, and the air volume to the printed circuit board changes intermittently. Therefore, the temperature deviation for each unit time is large, and the temperature change rate of the adjacent measurement temperatures fluctuates greatly for each hour. When the measured temperature is a discrete value and the heating capacity of the heating mechanism fluctuates, the deviation of the temperature inside the main body of the reflow furnace calculated from the measured temperature profile tends to be amplified. Therefore, in the reflow furnace 100, smoothing is performed on the measured temperature profile prior to the calculation of the temperature of the reflow furnace 100. Specifically, the processing circuit 31 uses a low-pass filter 310 to smooth the temperature change rates of two measurement temperatures having adjacent sampling times in the measurement temperature profile.

FIG. 6 is a time chart for explaining the smoothing process of the measurement temperature profile. In FIG. 6, graph 9 represents the actual temperature profile of the measurement site. Graph 10 represents the measured discrete temperature profile. Graph 11 represents a smoothed measurement temperature profile. Times st1 to st14 represent sampling times. Further, in FIG. 6, the correspondence between the sampling value for each sampling time and the filter processing value by the low-pass filter 310 is shown. For convenience of explanation, the resolution of the temperature measurement in FIG. 6 is set to 10 ° C. That is, in FIG. 6, the measured temperature is a multiple of 10.

As shown in FIG. 6, the temperature of the actual temperature profile 9 for each sampling time is measured as a multiple of 10 closest to the temperature. For example, the actual temperature of the measurement site at the sampling time st3 is around 22 ° C., but the measurement temperature is measured as 20 ° C. The processing circuit 31 generates the measured temperature profile 11 by smoothing the discrete temperature profile 10 with a low-pass filter.

In the measurement temperature profile, the temperature difference ΔT between two consecutive sampling times is the temperature difference between the temperature Ta (temperature in the reflow furnace 100) of the air around the measurement site and the temperature Tb of the measurement site, and the heat transfer of the measurement site. Using the coefficient α, it is expressed as the following relational expression (1) (Newton's law of cooling). In equation (1), C is a constant. When the measurement site contains a plurality of materials, it is considered that the measurement site is composed of a virtual substance having a homogenized density of the plurality of materials. Hereinafter, the heat transfer coefficient of the virtual substance is also referred to as a virtual heat transfer coefficient.

From the formula (1), the temperature Ta in the reflow furnace 100 is expressed as the following formula (2).

From the transfer speed of the printed circuit board 1 (the speed of the transfer conveyor 2), the position of the measurement site in the transfer process at the sampling time can be obtained. Therefore, by using the measurement temperature profile 11 and the formula (2), the temperature distribution in the furnace showing the relationship between the position of the measurement site in the transport process and the temperature of the air at the position can be obtained.

FIG. 7 is a diagram showing the set temperature distribution 12, the smoothed measurement temperature profile 13, and the temperature distribution in the furnace 14. Since the transport speed of the printed circuit board 1 is known, the time corresponds to the position in the transport process of the measurement site at that time. With reference to FIG. 3, the time zone up to the time tm1 corresponds to the section Sc1 in FIG. The time zone from time tm1 to tm2 corresponds to the section Sc2. The time zone from time tm2 to tm3 corresponds to the section Sc3. The time zone from time tm3 to tm4 corresponds to the section Sc4. The time zone from time tm4 to tm5 corresponds to the section Sc5. The time zone from time tm5 to tm6 corresponds to the section Sc6. The time zone from time tm6 to tm7 corresponds to the section Sc7. The time zone from time tm7 to tm8 corresponds to the section Sc8. The time zone after the time tm8 corresponds to the section Sc9. That is, the dotted lines corresponding to each of the times tm1 to tm8 represent the time when the object to be heated passes through the boundary of the adjacent section. The time ts (specific time) is a time when the temperature of the set temperature distribution 12 becomes maximum and a time when the temperature distribution 14 in the furnace becomes maximum, and is included in the time zone of times tm6 to tm7.

In the actual reflow furnace 100, in addition to heat transfer between the air and the measurement site, physical phenomena such as heat radiation from the inner wall of the reflow furnace 100 and heat conduction in the printed circuit board 1 also occur. However, the effect of other physical phenomena on the temperature Ta is smaller than that of heat transfer between the air and the measurement site. Therefore, by appropriately setting the heat transfer coefficient α in the equation (2), sufficient accuracy can be obtained for the prediction of the temperature Ta.

The heat transfer coefficient α is determined so that the difference between the temperature corresponding to the time ts in the furnace temperature distribution 14 and the temperature corresponding to the time ts in the set temperature distribution 12 disappears (or falls within an allowable range). In FIG. 7, at time ts, the temperature of the temperature distribution 14 in the furnace and the temperature of the set temperature distribution 12 are substantially the same. As the specific time, it is desirable that the time is included in the time zone (interval) in which the solder is melted and the temperature of the temperature distribution 14 in the furnace becomes maximum, such as time ts. However, the temperature of the section closest to the outlet portion 120 is easily affected by the section on the outlet portion 120 side, and there is a possibility that the temperature in the width direction of the transfer process in the reflow furnace 100 varies greatly in the section. When such an interval includes the maximum temperature, it is desirable to avoid the time in the time zone corresponding to the interval. Therefore, the specific time is not limited to the time when the temperature of the temperature distribution 14 in the furnace becomes maximum. For each measurement site, the temperature distribution in the furnace is generated for the measurement temperature profile of each measurement site, and the temperature of the temperature distribution in the furnace at a specific time almost matches the temperature of the set temperature distribution at the specific time. The virtual heat transfer coefficient is determined.

The set temperature distribution 12 can be expressed as a profile in which the temperature is constant in the time zone corresponding to each section. It is desirable that the temperature distribution 14 in the furnace changes according to the set temperature distribution 12. That is, it is desirable that the temperature is maintained at the temperature set in each section (time zone) of the set temperature distribution 12 in each section of the furnace temperature distribution 14. However, in the actual reflow furnace 100, the temperature of each section is not constant, and the temperature varies due to the influence of the sections adjacent to each section. The larger the difference between the set temperatures in the adjacent sections, the larger the difference between the set temperature and the actual temperature in the reflow furnace 100 can be. In particular, at the inlet 110 and the outlet 120, the warm air in the reflow furnace 100 flows out along the transfer process, so that the difference between the set temperature and the actual temperature in the reflow furnace 100 can be significantly large.

If there is a difference between the set temperature distribution 12 and the temperature distribution 14 in the furnace regardless of the difference in the measurement site, it is considered that the difference is due to the basic structure of the reflow furnace 100 or the temperature control method of the heating mechanism. be able to. If there is a difference in the temperature distribution 14 in the furnace calculated for each measurement site, the difference due to the temperature variation in the reflow furnace 100 depending on the position of the measurement site in the direction perpendicular to the transport direction and the object to be heated It can be inferred that the difference due to the difference in thermal characteristics such as thermal conductivity for each measurement site is combined.

In the reflow furnace 100, a complicated thermodynamic phenomenon in the reflow furnace 100 including the thermal effect of the reflow furnace 100 on the object to be heated and the temperature variation in the reflow furnace 100 is simplified by using Newton's law of cooling. The temperature distribution in the furnace 14 can be calculated by modeling in. The physical law used to simply model the thermodynamic phenomenon inside the reflow furnace 100 is not limited to Newton's law of cooling. The physical law describes the relationship between the temperature at the measurement site of the object to be heated and the temperature of the air around the measurement site, and the temperature difference of the object to be heated at the measurement site over time. Any physical law may be used as long as it is a physical law that derives the relational expression defined by using it.

FIG. 8 is a diagram showing the set temperature distribution 12 of FIG. 7, the temperature distribution in the furnace 14, and the corrected set temperature distribution 15. As shown in FIG. 8, in the sections Sc4 to Sc8 where the difference between the set temperature distribution 12 and the furnace temperature distribution 14 is relatively small, the set temperature distribution 12 is regarded as the furnace temperature distribution, and the following equation ( 3) can be used to predict the temperature profile of the measurement site. As the temperature Ta at a certain position in the reflow furnace 100, the temperature corresponding to the position in the set temperature distribution 12 is used.

However, since the set temperature distribution 12 and the temperature distribution in the furnace 14 may deviate from each other depending on the section, for example, in the sections Sc1 to Sc3, if the set temperature distribution 12 is used as it is for the temperature prediction, the accuracy of the temperature prediction is lowered. obtain. Therefore, the set temperature distribution 12 is corrected for each section so that the set temperature distribution 12 approaches the temperature distribution 14 in the furnace. The correction value may be set as a constant for each section, or may be set to a value proportional to the set temperature for each section. In FIG. 8, the set temperature distribution 12 actually used in the temperature measurement of the object to be heated is corrected, and the set temperature distribution 15 (second set temperature distribution) is obtained. The set temperature distribution 15 is a temperature distribution closer to the furnace temperature distribution 14 than the set temperature distribution 12. The set temperature distribution 15 is a set temperature distribution that approximates the temperature distribution 14 in the furnace, and is used in the simulation of temperature prediction.

The actual set temperature distribution 12 deviates from the set temperature distribution 15 used in the temperature prediction simulation by the amount of the correction value. The result of the temperature prediction simulation is reproduced in the actual reflow furnace 100 by actually using the set temperature distribution obtained by adding the correction value obtained by reversing the sign to the set temperature distribution used in the temperature prediction simulation. can do.

FIG. 9 is a diagram showing the simulation result of temperature prediction. In FIG. 9, the set temperature distribution 15 is the same as the corrected set temperature distribution 15 in FIG. The set temperature distribution 16 is a set temperature distribution in which the set temperature distribution 15 is changed. The temperature profiles 17 and 18 of the measurement site are simulation results based on the

set temperature distributions

15 and 16, respectively. As shown in FIG. 9, the temperature profile 18 changes with respect to the temperature profile 17 in response to the change of the set temperature distribution 16 with respect to the set temperature distribution 15. The temperature profile 18 can be reproduced in the actual reflow furnace 100 by actually using the set temperature distribution obtained by adding the value obtained by reversing the sign of the correction value of the set temperature distribution 15 to the set temperature distribution 16. it can.

By setting a virtual section for each of the inlet portion 110 and the outlet portion 120 and adding the section to the set temperature distribution, it is possible to correct the set temperature of the inlet portion 110 and the outlet portion 120. Further, for two adjacent sections (first section and second section), the first section includes the first temperature region set to the first temperature, and the second section is set to the second temperature. When a region is included, a temperature transition region in which the temperature of the air changes from the first temperature to the second temperature may be set between the first section and the second section. By setting the temperature transition region, the set temperature distribution 12 can be made into a shape closer to the temperature distribution 14 in the furnace. The set temperature distribution 12 can be expressed by a combination of straight lines on a graph having a time axis and a temperature axis. Further, the set temperature distribution 12 can be brought closer to the furnace temperature distribution 14 by the smoothing process.

With reference to FIG. 8 again, the correction value for each section is set so that the absolute value of the difference between the set temperature distribution 12 and the furnace temperature distribution 14 is equal to or less than the reference value (for example, 5 ° C.), and the corrected setting By using the temperature distribution 15, the accuracy of temperature prediction can be improved. Individual correction values may be set for each measurement site of the object to be heated. For simple use, or when the difference in the temperature distribution 14 in the furnace calculated at each measurement site is relatively small, the same correction value may be used for each measurement site. Further, the set temperature distribution can be expressed as the time for passing through each section becomes shorter when the transfer speed of the transfer conveyor 2 is changed to a higher speed. When the transport speed is changed to a slower speed, it can be expressed as a longer time to pass through each section. Even when the transport speed is changed, the temperature can be predicted by using the corrected set temperature distribution and the virtual heat transfer coefficient without measuring the temperature of the object to be heated again.

In the first embodiment, a reflow furnace having a tunnel-type transfer process has been described. The heating device according to the embodiment may be a programmed heating furnace capable of changing the set temperature stepwise. Further, in the first embodiment, a case where both the temperature measurement of the object to be heated and the temperature prediction of the object to be heated are performed in the control device of the heating device has been described. The temperature measurement of the object to be heated and the temperature prediction of the object to be heated need not be performed in the same device. For example, the temperature of the object to be heated may be predicted by a device separate from the device that measures the temperature of the object to be heated, such as a general-purpose PC (Personal Computer).

As described above, according to the temperature prediction device according to the first embodiment, it is possible to suppress a decrease in the accuracy of the temperature prediction in the heating device while simplifying the modeling inside the heating device.

Embodiment 2.
In the second embodiment, by registering the correction value for the set temperature distribution in the database, it is possible to predict the temperature of the object to be heated without calculating the correction value by comparing the temperature distribution in the furnace and the set temperature distribution. The configuration will be described.

In the database referred to in the second embodiment, the information of the object to be heated (first object to be heated) such as the material of the measurement site and the setting corrected based on the temperature measurement of the object to be heated performed in the past. Information such as the temperature distribution, the length of each section based on the arrangement of the heating mechanism, the length of the temperature transition region, and the correction value corresponding to each section is registered in association with the identification information of the heating device. In the following, the information associated with the identification information of the heating device in the database is simply referred to as the information of the heating device. Information on the heating device can be searched using the identification information of the heating device as a search key in the database. The database may be formed in the memory 32 of FIG. 2 or may be formed in an external server. By referring to the database, it is possible to specify the correction value corresponding to the structure based on the structure of the object to be heated (for example, the material of the measurement site on the printed circuit board) used this time.

FIG. 10 is a flowchart showing an example of the temperature prediction process performed by the temperature prediction device according to the second embodiment. The flowchart shown in FIG. 10 is a flowchart in which S104 to S106 of the flowchart shown in FIG. 4 is replaced with S204 to S206. As shown in FIG. 10, in the second embodiment, the temperature prediction process proceeds in the order of S101 to S103, S204 to S206, and S107. After S101 to S103 are performed in the same manner as in the first embodiment, in S204, the information of the heating device is searched in the database using the identification information of the heating device used in S101. In S205, the set temperature distribution in S101 is corrected using the information searched in S204, and the temperature profile is predicted based on the corrected set temperature distribution. In S206, the heat transfer coefficient used in S205 is modified so that the temperature profile generated in S205 approaches the measured temperature profile measured in S101. In S107, the temperature of the measurement site is predicted using the changed set temperature distribution and the modified heat transfer coefficient.

In the second embodiment, the corrected set temperature distribution is generated from the information registered in the database. Using the set temperature distribution, the temperature is predicted for the object to be heated (second object to be heated) for which the temperature has been measured. The virtual heat transfer coefficient of the measurement site used in the temperature prediction is modified so that the predicted temperature profile approaches the measured temperature profile.

As a method of modifying the heat transfer coefficient, for example, the measurement site used in the temperature prediction so that the difference between the maximum temperature of the measurement temperature profile and the maximum temperature of the predicted temperature profile disappears (or falls within the allowable range). A method of modifying the heat transfer coefficient of By focusing on the maximum temperature of the temperature profile, it is not necessary to input all the measurement data of the object to be heated into the temperature prediction software because the measurement data other than the maximum temperature is unnecessary. For example, by transmitting the maximum temperature of the temperature profile measured at one location to another location and inputting the maximum temperature into the temperature prediction software, the maximum temperature of the predicted temperature profile was transmitted from a remote location. The heat transfer coefficient can be calculated to match the maximum temperature. According to this method, it is possible to predict the temperature of the object to be heated by transmitting the maximum temperature of the measured temperature profile between remote locations, for example, by telephone communication.

FIG. 11 is a flowchart showing another example of the temperature prediction process performed by the temperature prediction device according to the second embodiment. The flowchart shown in FIG. 11 is a flowchart in which S102 is removed from the flowchart shown in FIG. 10, S215 is added after S205, and S206 is replaced with S216. The temperature prediction process shown in FIG. 11 proceeds in the order of S101, S103, S204, S205, S215, S216, S107. After S101, S103, S204, and S205 are performed, in S215, the maximum temperature of the measurement temperature profile generated in S101 is input to the temperature prediction software. In S216, the heat transfer coefficient used in S205 is modified so that there is no difference between the maximum temperature input in S215 and the maximum temperature in the temperature profile predicted in S205. In S107, the temperature of the measurement site is predicted based on the changed set temperature distribution.

The database referred to in the second embodiment can often be shared between heating devices having the same structure. Even if data such as correction values based on the measurement data of the object to be heated by a certain heating device is not registered in the database, if the data of the heating device having the same structure as the heating device is registered in the database, By using the data, it is possible to predict the temperature. Further, by aggregating the information of the heating devices arranged in a plurality of locations in one database, it is possible to centrally manage the conditions such as the set temperature distribution and the transfer speed of the plurality of heating devices.

The temperature profile in the furnace may be registered in the database. By comparing the furnace temperature profiles created for each different heating device, the characteristics of each heating device can be easily confirmed from the shape of the furnace temperature profile. In addition, by generating a furnace temperature profile in a certain heating device on a regular basis (for example, every month) and comparing the current furnace temperature profile with the previously generated furnace temperature profile, the said The health of the heating device can be checked. Similarly, by comparing the temperature profiles in the furnace calculated from the measurement data of multiple measurement sites of the object to be heated, the temperature variation in the heating device or a part of the air passage in the heating device is blocked. It is possible to detect such local defects.

As described above, according to the temperature prediction device according to the second embodiment, it is possible to suppress a decrease in the accuracy of the temperature prediction in the heating device while simplifying the modeling inside the heating device.

It is also planned that the embodiments disclosed this time will be appropriately combined and implemented within a consistent range. It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present disclosure is indicated by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope of the claims.

1 Printed circuit board, 2 Conveyance conveyor, 8 Data logger, 30 Control device, 31 Processing circuit, 32 Memory, 33 Input / output section, 34 Display section, 41-47, 51-57 Heating mechanism, 61, 62 Cooling mechanism, 71 , 72 Thermocouples, 81-83 mounting parts, 100 reflow furnaces, 110 inlets, 120 outlets, 310 low-pass filters, Sa1-Sa7, Sb1-Sb7 temperature sensors.

Claims

A temperature predictor that predicts the temperature inside a heating device that heats the first object to be heated.
The heating device has a set temperature of air corresponding to the position according to a first set temperature distribution indicating the relationship between each of a plurality of positions in the transport process in which the first object to be heated moves and the temperature of the air at the position. Is blown toward the transport process,
The temperature predictor is
Control unit and
It is provided with a storage unit for storing a first measurement temperature profile showing the relationship between the measurement temperature and the measurement time of the measurement site of the first object to be heated moving in the heating device.
The control unit
Heat transfer of the relationship between the temperature of the first object to be heated at the measurement site and the temperature of the air around the measurement site, and the temperature difference of the first object to be heated at the measurement site over time. Using a relational expression defined using a coefficient, the temperature of the air at the position of the measurement site at a specific time and the temperature of the air corresponding to the position of the measurement site at the specific time in the first set temperature distribution. Determine the heat transfer coefficient so that there is no difference,
A temperature prediction device that predicts the temperature distribution of air in the transfer process using the first measurement temperature profile and the relational expression.
The temperature prediction device according to claim 1, wherein the temperature of the air at the position of the measurement site at the specific time is the maximum in the temperature distribution of the air in the transport process.
The control unit
The first set temperature distribution is corrected so as to approach the temperature distribution of air in the transport process, and the second set temperature distribution is generated.
A third set temperature distribution is generated by changing the temperature corresponding to each of the plurality of positions in the second set temperature distribution.
The temperature prediction device according to claim 1 or 2, wherein the temperature profile of the measurement site is predicted by using the third set temperature distribution and the relational expression.
Claim that the absolute value of the difference between the temperature corresponding to each of the plurality of positions in the second set temperature distribution and the temperature corresponding to the position in the temperature distribution of air in the transport process is smaller than the reference value. 3. The temperature predictor according to 3.
The heating device includes a plurality of heating mechanisms that realize the first set temperature distribution.
The plurality of heating mechanisms are arranged along the transfer process.
The heating mechanism is divided into a plurality of heating sections along the transport direction of the first object to be heated.
The plurality of heating mechanisms are respectively arranged in the plurality of heating sections.
The temperature prediction device further includes a display unit.
The control unit claims that a straight line indicating the time when the first object to be heated passes through the boundary between adjacent sections in the plurality of heating sections is superimposed on the temperature profile of the measurement site and displayed on the display unit. The temperature prediction device according to any one of 1 to 4.
The control unit generates the second set temperature distribution by referring to the database in which the correction values used for the correction of the first set temperature distribution and the first set temperature distribution are registered.
In the storage unit, a second measurement temperature profile showing the relationship between the measurement temperature and the measurement time of the measurement site of the second object to be heated moving in the heating device is further stored.
The control unit predicts the second temperature profile of the measurement site of the second object to be heated by using the second set temperature distribution and the relational expression, and the maximum temperature of the second temperature profile and the second measurement temperature. The temperature predictor according to claim 3 or 4, wherein the heat transfer coefficient is modified so that there is no difference from the maximum temperature of the profile.
In the first set temperature distribution, the first temperature region in which the air temperature is set to the first temperature, the temperature transition region in which the air temperature changes from the first temperature to the second temperature, and the air temperature are the first. The temperature prediction device according to any one of claims 1 to 6, wherein temperature regions are set in the order of a second temperature region set to two temperatures.
The control unit performs the first measurement temperature profile by smoothing the discrete temperature profile indicating the relationship between the temperature of the measurement site measured at each sampling time and the sampling time with a low-pass filter. The temperature predictor according to any one of claims 1 to 7, which is generated.
It is a temperature prediction method that predicts the temperature inside the heating device that heats the object to be heated.
The heating device uses the air having a set temperature corresponding to the position according to the first set temperature distribution showing the relationship between each of the plurality of positions in the transport process in which the object to be heated moves and the temperature of the air at the position. Blow toward the transport process,
The temperature prediction method is
A step of generating a first measurement temperature profile showing the relationship between the measurement temperature and the measurement time of the measurement site of the object to be heated moving in the heating device, and
The relationship between the temperature of the object to be heated at the measurement site and the temperature of the air around the measurement site and the temperature difference of the object to be heated at the measurement site with the passage of time is determined by using the heat transfer coefficient. Using the defined relational expression, the difference between the temperature of the air at the position of the measurement site at the specific time and the temperature of the air corresponding to the position of the measurement site at the specific time in the first set temperature distribution is eliminated. In the step of determining the heat transfer coefficient,
A temperature prediction method including a step of predicting the temperature distribution of air in the transport process using the first measurement temperature profile and the relational expression.