JPH11251735A - Method and equipment for reflow soldering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to apply appropriate quantity of heat to each substrate even if the temperature in a furnace changes, by setting the reflow time appropriate for each stage for each substrate when a reflow-soldered substrate reaches a reflow section, and then reflow-soldering the substrate for the set reflow time. SOLUTION: When a substrate 1 is put on a conveyor line, the substrate 1 is detected by a substrate detecting sensor 2 located at the entrance of the main body of the equipment. For continuous production, succeeding substrates 1 are put on the conveyor line one after another and the placing interval between the substrates 1 is recognized by the detection of the substrates 1 by the substrate detecting sensor 2. A control unit 3 classifies the substrate placing intervals into several stages according to a predetermined criterion. When the reflow-soldered substrates 1 reach a reflow section 5, the control unit 3 changes the setting of reflow time to the one appropriate to each stage for each substrate 1 and then each substrate 1 is reflow-soldered for the set reflow time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflow soldering method and apparatus for soldering electronic components mounted on a board.

[0002]

2. Description of the Related Art In order to solder an electronic component mounted on a board using a conventional reflow soldering apparatus, the size, shape, thickness, mounting state, and type of mounted electronic component of the board to be produced are required. For example, the setting value of the reflow device for each substrate, that is, the temperature of the heater for blowing the hot air to the substrate, the speed of the conveyor for transporting the substrate, the wind speed of the hot air blown to the substrate, and the like, are considered, means,
A method is used to perform soldering.

[0003] For example, the temperature of a required portion on a substrate is measured, and the heat-resistant temperature of an electronic component or a substrate that is vulnerable to heat is examined. The set value of the reflow condition of the reflow soldering apparatus is determined in consideration of the soldering temperature from the melting point of the solder and the solder wettability. During normal board production, the reflow conditions determined here basically remain fixed as long as the production model is the same. The temperature of each heating means such as an infrared heater is adjusted to stabilize the furnace temperature.

[0004]

However, in the above-described conventional reflow soldering method, the temperature in the furnace or the temperature of the heater actually changes during production, and the substrate cannot be moved in the furnace in a state where these temperature adjustments are insufficiently followed. When the temperature inside the furnace or the heater temperature rises to reach the reflow heating for the same time as the normal case, the temperature reaches a higher temperature than the reflow peak temperature in the normal temperature profile, and the In some cases, the electronic component or the substrate may have a performance defect that exceeds the heat resistance temperature or the heat resistance temperature of the substrate.

On the other hand, when the furnace temperature or the heater temperature decreases, the temperature rises only to a temperature lower than the reflow peak temperature in the normal temperature profile, and reaches the required temperature of the solder joint. In some cases, poor soldering such as unmelted solder or poor wetting may occur.

In both hot air heating and infrared heating, a certain amount of time is required for temperature adjustment when the furnace temperature or the heater temperature changes, and the furnace temperature or the heater temperature is always stable. Sometimes good, but poor response when not stable.

Therefore, when setting the conditions of the above-mentioned conventional reflow soldering apparatus, usually, when measuring the temperature on the substrate, a single measurement substrate having a thermocouple for temperature measurement attached to a measurement location is conveyed. , And the temperature of each part in the furnace at that time is determined by checking the temperature rising state. According to this, the substrate is not in a state in which the substrate is flowing continuously as in the case of normal substrate production, and thus may differ from the actual temperature condition. In other words, when the substrate flows continuously, the surface temperature of the heater rises due to the secondary radiant heat from the substrate or the heat residue between the heater and the substrate, and the temperature adjustment of the heater also follows because the surface temperature changes. However, there is a problem that an excessive amount of heat may be applied to a subsequent substrate.

The present invention solves the above-mentioned problem, and applies an appropriate amount of heat to each substrate in response to a change in a furnace temperature such as a heater temperature or a hot air temperature during production. It is an object of the present invention to provide a reflow soldering method and apparatus which can perform the reflow soldering.

[0009]

In order to achieve the above-mentioned object, a reflow soldering method according to a first aspect of the present invention grasps in advance an interval of loading substrates into a reflow furnace and classifies the interval into a plurality of stages. Then, when the target substrate arrives at the reflow section, a reflow time corresponding to each stage is set for each substrate and reflow soldering is performed.

In the reflow soldering method according to the second invention of the present application, the temperature of a predetermined location near the heating source of the reflow portion is constantly monitored, and the reflow time for each substrate is determined at the time when the substrate is reflowed. And reflow soldering is set.

A reflow soldering apparatus according to a first aspect of the present invention includes a board detection sensor for detecting insertion of a board and a board insertion interval detected by the board detection sensor, and classifies the insertion interval into a plurality of stages. A control unit for controlling a reflow soldering time, and a reflow section for reflow soldering a substrate which has been lifted and stopped by a lifting unit from a transport line for a predetermined time controlled by the control unit. And

A reflow soldering apparatus according to a second aspect of the present invention includes a mask having a plurality of hot air jets for jetting hot air from a heater in a reflow section onto a substrate, such as a thermocouple for monitoring the surface temperature of the mask. A temperature sensor is provided, and a reflow time is set for each substrate according to the surface temperature of the mask at the time when the substrate reaches the reflow portion, and the substrate that has been raised and stopped by the elevating unit from the transport line is set. It is characterized in that reflow soldering is performed only for a time.

[0013] According to the reflow soldering method and apparatus of the first invention, the input intervals of the substrates are grasped in advance, and the intervals are classified into a plurality of stages. Since the reflow time corresponding to the above is set for each board and reflow soldering is performed,
The reflow time can be set according to the expected changes in the temperature of the reflow section, etc., thereby minimizing the fluctuation of the reflow peak temperature, and the performance of the electronic parts and the board and the good soldering. Sex can be maintained.

According to the reflow soldering method and apparatus of the second invention, the temperature of a predetermined portion near the heating source of the reflow portion such as the mask surface is constantly monitored, and each substrate is re-flowed at the time when the substrate is reflowed. Since the reflow time is set for each and the reflow soldering is performed, the reflow time can be set according to the temperature of the reflow section, whereby fluctuations in the reflow peak temperature can be minimized, and electronic components and The performance of the substrate and good solderability can be maintained.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a reflow soldering method and apparatus according to an embodiment of the present invention.

FIG. 1 is a schematic front view showing the structure of the reflow soldering apparatus according to the first embodiment, and FIG. 2 is an enlarged schematic longitudinal sectional view of a reflow portion.

The reflow soldering apparatus according to the first embodiment comprises:
As shown in FIG. 1, a board detection sensor 2 for detecting the insertion of the board 1 and an insertion interval of the board 1 based on the detection of the board detection sensor 2 are determined, the insertion interval is classified into a plurality of stages, and the reflow soldering time is reduced. A control unit 3 for controlling, and a reflow section 5 for reflow soldering the substrate 1 which has been lifted and stopped by the lifting unit 6 from the transport rail 7 constituting the transport line for a predetermined time controlled by the control unit 3
And a preheating unit 4 disposed on the side of the reflow unit 5 in the transfer rail 7 that forms the transfer line.

Further, as shown in FIG. 2, an infrared heater 10 as a heat source, an infrared heater 10
And a mask 9 held in the hot air blowing chamber 8 and having a plurality of hot air outlets 9a. In FIG. 2, reference numeral 11 denotes cream solder for soldering terminal portions of the electronic component 20, and reference numeral 12 denotes a hot air blowing chamber 8.
And a nozzle for blowing hot air into the hot air blowing chamber 8.

Next, a reflow soldering method using the reflow soldering apparatus of the first embodiment having the above-described structure will be described.

When the substrate 1 is put into the transfer line,
The substrate 1 is detected by the substrate detection sensor 2 disposed at the entrance of the apparatus main body.

During continuous production, the subsequent substrates 1 are successively loaded, and the loading intervals of these substrates 1 are recognized by the detection of the substrates 1 by the substrate detection sensor 2.

The control unit 3 classifies the recognized loading intervals of the substrates 1 into several stages according to a predetermined criterion, and when the target substrate 1 arrives at the reflow unit 5, The setting of the substrate 1 is changed to the reflow time corresponding to each stage, and the reflow soldering is performed for the reflow time.

This is input into the entrance of the apparatus main body, detected by the substrate detection sensor 2, and recognizes the input interval, and the control unit 3 judges the substrate 1 that has been classified into several stages and passes through the preheating unit 4. When the substrate 1 arrives at the reflow unit 5, the substrate 1 is raised by the reflow elevating unit 6, and is heated for a predetermined reflow time. In this case, the time during which the substrate 1 is stopped and heated at the position where the elevating unit 6 has risen is controlled as the reflow time.

Here, the necessity of changing the reflow time will be described. FIG. 2 shows the reflow unit 5 in which the substrate 1 arrives at the reflow unit 5 and the reflow elevating unit 6
Shows a state in which the substrate 1 is raised and stopped to perform heating.

During the heating, since the substrate 1 is close to the mask 9, the surface temperature of the mask 9, which is a direct heating element for the substrate 1 by receiving radiation from the infrared heater 10, The temperature rises from the initial state due to secondary radiation and thermal debris between the substrate 1 and the mask 9. At this time,
After the reflow of the substrate 1 is completed, the subsequent substrate 1 is similarly subjected to reflow heating. However, if the subsequent substrate 1 arrives at the reflow unit 5 before the temperature of the mask 9 returns to the initial state and stabilizes, Since the subsequent substrate 1 starts to be heated while the surface temperature of the mask 9 is high, if the reflow time is the same, the peak temperature of the temperature profile increases, and the surface temperature of the mask 9 also increases.

As shown in FIG. 3, when the surface temperature of the mask 9 is measured, as shown in FIG. 3, when the substrate 1 is loaded with a tact time of about 30 seconds, the temperature is gradually increased from the initial state of about 325 ° C. 3
After the temperature reaches about 52 ° C., the temperature is stabilized while the substrate 1 is loaded with the same tact. At this time, the temperature profiles of the produced substrates 1 are all different for each substrate 1 until the temperature of the mask 9 is stabilized on the high temperature side.

Accordingly, it is necessary to adjust the reflow time in order to minimize the variation in the peak temperature of the temperature profile.

Next, the classification of the loading interval of the substrate 1 in the first embodiment will be described.

In the first embodiment, when the substrate 1 is loaded, the loading interval of the substrate 1 recognized by the substrate detection sensor 2 is divided into three stages, and the loading interval is 50 seconds or less.
50 seconds to 120 seconds, 120 seconds or more. For these classifications, conditions for changing the reflow time according to the loading interval of the three substrates 1 loaded continuously are set in advance as follows.

Reflow time setting conditions (1) First sheet: Normal reflow time = 22 seconds (2) Second sheet: Normal reflow time = 22 seconds (3) Third sheet: Shorter reflow time if inserted in 50 seconds or less = 19 seconds Returning to (2) if inserted in 50 seconds to 120 seconds.

Returning to (1) if the charging is performed for 120 seconds or more.

(In this case, the classification of (3) is performed again) That is, the first substrate 1 and the second substrate 1 at the start of the production of the substrate 1 are described in (1) above. , (2), and thereafter, for the third and subsequent sheets, the reflow time is sequentially determined by repeating the classification in (3).

At this time, the reason for returning to the initial state when the interval of loading the substrate 1 is 120 seconds or more will be described.

FIG. 4 shows the mask when the loading of the substrate 1 is stopped from the state of 360 ° C. which is the peak temperature of the mask 9 in the high temperature stable state when the substrate 1 is continuously reflow soldered. 9 shows the change over time of the temperature of No. 9.

It can be seen from FIG. 4 that the temperature of the mask 9 drops to the initial state 120 seconds after the loading of the substrate 1 is stopped and is stable. Therefore, in the first embodiment, the initialization time can be set to 120 seconds between loading of the substrate 1.

FIG. 5 shows several examples of reflow time setting charts. As shown in Examples 1 to 3 in FIG. 5, each substrate 1 is determined not only based on the interval between the substrates 1 but also from the previous substrate 1 but from the state of going back one more.

The control parameters for executing the above-described determination in the reflow soldering apparatus of the first embodiment include: a counter section; a continuous carry-in judgment number (sheets); a continuous carry-in reset (initialization) number (sheets). Timer section Continuous loading judgment time (sec) Shortened reflow time (sec) Reduced loading tact (sec) Reflow time initialization decision time (sec)
Counter unit 3rd sheet: Decision of continuous loading is the shortened reflow time when three sheets are continuously loaded.

First sheet: When the carry-in interval exceeds the continuous carry-in judgment time and is within the reflow time initialization judgment time, it is regarded as a state after the first sheet has passed.

Timer section 50 seconds: If the next substrate 1 is carried in within 50 seconds, it is regarded as continuous carrying in. 18 seconds: Reflow time when judging as shortened reflow time 28 seconds: Board 1 which is judged as shortened reflow time Next, the loading interval of the substrate 1 is 120 seconds: If the loading interval exceeds 120 seconds, the determination of the continuous loading is initialized. FIG. 6 shows the results of temperature measurement of each portion of the substrate surface in the first embodiment described above.

Referring to FIG. 6, the peak temperature of each part of the temperature profile of the first sheet (reflow time: 22 seconds) is 236 ° C. for the lead of the electronic component and 190 ° C. for the substrate 1. ing. After that, looking at the temperature profiles of the respective portions of the fourth substrate surface when four substrates 1 were continuously loaded, the substrate 1 reflowed with the reflow time kept in the initial state (22 seconds) The temperature of the leads of the electronic component is 243 ° C., and the temperature of the substrate 1 is 196 ° C., which is approximately 6 ° C. to 7 ° C. higher. On the other hand, when the setting of the reflow time is shortened (19 seconds), the temperature of the lead of the electronic component is 234 ° C., the temperature of the substrate 1 is 190 ° C., and the maximum is about 2 ° C. It is in the fluctuation.

Therefore, according to the reflow soldering method using the reflow soldering apparatus of the first embodiment described above, the insertion intervals of the substrate 1 are grasped in advance, and the intervals are classified into a plurality of stages to determine When the substrate 1 reaches the reflow unit 5, the reflow time corresponding to each stage is set for each substrate 1 and reflow soldering is performed, so that the amount of heat generated by the hot air blown to each substrate 1 and the infrared rays is substantially constant. Thus, substantially uniform reflow soldering can be performed on each substrate 1.

FIG. 7 shows the structure of the reflow portion of the reflow soldering apparatus according to the second embodiment.

The reflow soldering apparatus according to the second embodiment has a mask 9 having a plurality of hot air outlets 9a for blowing hot air from a heater 10 of a reflow section 5 to a substrate 1.
Further, a thermocouple (temperature sensor) 13 for monitoring the surface temperature of the mask 9 is provided.

Then, the set time of the reflow time is changed for each substrate 1 according to the surface temperature of the mask 9 at the time when the substrate 1 reaches the reflow section 5, and the substrate 1 is lifted up from the transport line by the elevating unit 6 and stopped. The reflow soldering is performed for the set substrate 1 for a set time.

Therefore, the amount of heat generated by the hot air and infrared rays blown onto each substrate 1 can be made substantially constant, and substantially uniform reflow soldering can be performed on each substrate 1.

When the reflow soldering is performed by the reflow soldering apparatus of the first embodiment and the second embodiment, the reflow time is controlled by time rather than by keeping the reflow time constant as in the related art. The fluctuation of the peak temperature of the reflow temperature can be suppressed to a small value.
Since the loading tact of the substrate 1 can be reduced, the production tact can be reduced.

[0047]

According to the present invention, the change in the reflow peak temperature can be minimized by changing the reflow time according to the situation such as the temperature of the reflow section.
The performance and good solderability of electronic components and boards can be maintained.

[Brief description of the drawings]

FIG. 1 is a schematic front view showing a reflow soldering apparatus according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a reflow section of the reflow soldering apparatus according to the first embodiment.

FIG. 3 is a graph showing a temporal change of a surface temperature of a mask when a substrate is continuously supplied in the reflow soldering apparatus of the first embodiment.

FIG. 4 is a graph showing a state in which the temperature of the mask, which has been raised by continuous loading of the substrate in the reflow soldering apparatus of the first embodiment, is lowered by stopping loading of the substrate.

FIG. 5 is a diagram showing a model example of several patterns showing how the reflow time is set for each substrate in the reflow soldering apparatus according to the first embodiment in accordance with the setting conditions of the board insertion interval and the reflow time.

FIG. 6 shows the reflow conditions for the fourth sheet when four sheets are continuously inserted with respect to the temperature of each position on the substrate in the initial state in the reflow soldering apparatus of the first embodiment, 5 is a graph showing a temperature profile at each point on a substrate when reflow is performed under two conditions of a state and a reflow time reduction.

FIG. 7 is a longitudinal sectional view showing a reflow portion of a reflow soldering apparatus according to a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Substrate detection sensor 3 Control unit 5 Reflow part 6 Elevating unit 7 Transport rail 9 Mask 10 Infrared heater 13 Thermocouple

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Shinichi Ouchi 1006 Kazuma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. An interval between loading of substrates into a reflow furnace is grasped in advance, the intervals are classified into a plurality of stages, and when a target substrate arrives at a reflow section, a reflow time corresponding to each stage is determined. A reflow soldering method, wherein the method is set on a substrate and reflow soldered. 2. The method according to claim 1, wherein the temperature of a predetermined location near the heating source of the reflow section is constantly monitored, and the reflow time is set for each substrate based on the temperature at the time when the substrate is reflowed. Reflow soldering method. 3. A board detection sensor for detecting board insertion, a control unit for judging a board insertion interval based on detection of the board detection sensor, classifying the boarding interval into a plurality of stages, and controlling a reflow soldering time. A reflow soldering device for reflow soldering a substrate that has been lifted and stopped by a lifting unit from a transport line for a predetermined time controlled by the control unit. 4. A mask having a plurality of hot air jets for jetting hot air from a heater in a reflow section to a substrate is provided with a temperature sensor for monitoring a surface temperature of the mask, and the substrate reaches the reflow section. The reflow time is set for each substrate according to the surface temperature of the mask at the time, and the substrate that has been lifted and stopped by the elevating unit from the transport line is subjected to the reflow soldering for the set time. Features reflow soldering equipment.