JPH02307673A - Method and device for automatic soldering - Google Patents

Abstract

PURPOSE:To uniformly melt cream solder and to allow the execution of high- performance soldering without fluctuations by heating a transporting device which is imposed with circuit boards and transports the circuit boards, conducting heat from the transporting device the circuit boards, thereby uniformly heating the circuit boards. CONSTITUTION:The transporting device 2 transports the circuit boards 5 to a preheating chamber 15 and a soldering chamber 16. The front surfaces 5a and electronic parts 4 of the circuit boards 5 are heated by the IR rays radiated from upper heaters 13. A transporting member 12 is heated by heaters 13 dis posed below the transporting device 2 to a high temp. and, therefore, the rear surfaces 5b of the wait boards are heated. The circuit boards are heated from the top and bottom and the cream solder is melted uniformly in all parts of the circuit board 5. The front surface 12a of the transporting member 12 is formed flat in order to maintain tight contact with the circuit boards 5 and is formed with many fins 12d, 12e, 12f in order to improve the heat conduction. The high-performance soldering is executed without fluctuations.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an automatic soldering method and apparatus, and in particular to a method and apparatus for automatic soldering, in which the upper surface of a conveying device is formed into a planar shape, and substrates are loaded and conveyed by making the upper surface of the conveying device in close contact with the upper surface. At the same time, the automatic soldering method improves soldering performance by actively heating the conveying device to conduct heat from the conveying device to the board, heating the board evenly and uniformly. and related to equipment.

BACKGROUND OF THE INVENTION Conventional substrate heating methods and devices for reflow soldering, for example, directly heat the substrate using heaters disposed above and below a net conveyor for conveying the substrate. However, according to the conventional method and apparatus, when heating the board from above, the part of the board without electronic components is heated relatively quickly, but the part of the board in the shadow of the electronic parts is not heated easily, resulting in a temperature difference. In addition, when heating the board from below, the net conveyor becomes an obstacle and the heat conduction efficiency is poor. Also, there is a temperature difference between the part that is in the shadow of the net and the part that is not. The solder paste had the disadvantage that the cream solder applied to the area would not dissolve uniformly, making it impossible to obtain sufficient soldering performance. In addition, if the temperature of the heater is increased to increase the temperature of the board in the shadow area of the electronic component or the net, there is a drawback that the board may crack due to heat shock or the electrical characteristics of the electronic component may change. Furthermore, since the thermal conditions between the upper and lower surfaces of the substrate are different, a temperature difference also occurs between the upper and lower surfaces of the substrate, resulting in the substrate being warped.

The above-mentioned measures for improving the heat conduction efficiency from the bottom surface of the substrate have already been published by the present applicant (Japanese Patent Application Laid-Open No. 1983-68265), but there is still room for improvement in preventing local temperature differences on the substrate. was there.

In addition, as another conventional example of preventing temperature differences, there is a hot air circulation method in which heated air or special steam is circulated within a heating chamber and the substrate is heated through the air or special steam. In this method, it is necessary to provide a special blower device and circulation passage for circulating heated air or special steam, which results in a large-sized device and a large amount of noise.
Another problem was that the production cost was high. In addition, in equipment that uses special steam, the special steam is toxic and a considerable amount evaporates and escapes from the equipment after one use, and it is impossible to recover the vapor that escapes. The disadvantage of this method was that it was expensive.

Purpose The present invention has been made in order to eliminate the drawbacks of the above-mentioned prior art, and its purpose is to form the top surface of a transfer device into a flat shape and to stack substrates by making the top surface of the transfer device adhere to the top surface. At the same time, by actively heating the conveying device, heat is conducted from the conveying device to the board, and the entire surface of the board is uniformly heated without unevenness. The purpose is to uniformly melt the solder in all parts of the board, so that high-performance soldering can be achieved without any variation in soldering performance.
This also improves the reliability of the finished board. Another purpose is to prevent the board from cracking due to heat shock by uniformly and gradually heating the board, and to prevent changes in the electrical characteristics of electronic components to be soldered. The purpose is to prevent the substrate from warping by eliminating the temperature difference between the surface and the surface. Another purpose is to achieve high performance soldering with inexpensive and compact equipment without requiring any special equipment or materials as a heat medium, such as a hot air circulation method; This is to reduce soldering costs.

Configuration In short, the method of the present invention (claim 1) includes loading and transporting a board on which electronic components are mounted in close contact with the upper surface of a transporting device whose upper surface is formed into a flat shape, and heating the transporting device. The present invention is characterized in that heat is conducted from the transfer device to the substrate to uniformly heat the substrate.

The apparatus of the present invention (Claim 2) also includes a transporting device that loads and transports a board on which electronic components are mounted in close contact with an upper surface formed in a planar shape; The present invention is characterized in that it includes a heating device for heating.

The present invention will be explained below based on embodiments shown in the drawings. An automatic soldering device 1 according to the present invention includes a conveying device 2 and a heating device 3 in FIGS. 1 and 2. The conveyance device 2 carries a board 5 on which electronic components 4 are mounted, also referring to FIG.
are loaded on a board loading section 20 and transported while conducting heat to the board.The automatic soldering shown in FIG. A plurality of pairs of pole bearings 8 (second
A shaft 9 is rotatably mounted on each of the shafts (FIG.), and a pair of sprockets 10 are fixed to the shafts at a predetermined distance. An endless chain 11 is wound around one set and the other set of the pair of sprockets 10, respectively, and is guided by the sprockets 10 as indicated by the arrows A and 10.
One end 12 of a large number of flat conveying members 12 configured to circulate in the direction and further having a flat upper surface 12a.
b is fixed to one chain 11, the other end 12C is fixed to the other chain 11, and a drive device (not shown) is connected to the shaft 9.
When rotated, it circulates in the directions of arrows A and B together with the chain 11. and conveyance member 12
In order to carry in the substrates 5 stacked in close contact with the upper surface 12a (substrate loading section 20) from the substrate loading port 6a (in the direction of arrow A),
After being heated and soldered by the heating device 3 and carried out from the carry-out port 6b, the moving direction is changed to the direction of arrow B and the plate is returned to the carry-out port 6a again.

Here, the conveyance member 12 conducts the heat heated by the heating device 3 to the substrate 5 as described later, and conveys it in the direction of arrow A while increasing the temperature of the substrate to the temperature for soldering (approximately 230° C.). It is made of, for example, aluminum, ceramics, or titanium alloy and is set to have a heat capacity suitable for being cooled down to room temperature during the return process of movement in direction B.

Referring also to FIG. 5, the upper surface 12a of the conveying member 12 is formed into a flat shape so that the substrates 5 can be stacked closely together in order to improve the heat conduction efficiency.
A large number of fins 1 are provided on the lower surface 12d and the side surface 12e so that the temperature is high by rapidly receiving heat from the fins, and the heat is rapidly released during the return process of the movement in the direction of arrow B.
2f can also be formed.

The heating device 3 heats the substrate 5 to a soldering temperature by heating the conveying member 12 and transmitting heat to the substrate 5 stacked in close contact with the conveying member. Heaters 3 (for example, sheathed heaters) are fixed in pairs at positions 50 to 80 m above and 5 to 10 m below, and a plurality of pairs are arranged along the conveyance direction of the substrate 5.

The plurality of pairs of heaters 3 are each partitioned by a partition wall 14 to form a preheating chamber 15 and a soldering chamber 16 independently. Here, the reason why the heater 3 disposed above the transfer device 2 is 50 to 80++n away from the transfer device is that the heat radiated from the heater 3 directly heats the substrate 5. This is to prevent cracking and warping of the board 5 and changes in the electrical characteristics of the electronic components 4 due to heat shock caused by heating the board more rapidly than necessary. ~10 Tsuru is disposed in close proximity to the substrate 5 by heating the conveying member 12 with the heater 3 instead of directly heating the substrate 5, and indirectly heating the substrate 5 by heat conduction from the conveying member. This is because uniform heating increases the efficiency of heat conduction from below and eliminates the temperature difference between the upper surface 5a and lower surface 5b of the substrate 5.

Furthermore, the amount of electric power supplied to the heater 3 is controlled by a control device (not shown), and the amount of electricity supplied to the heater 3 is controlled by a preheating chamber 15.
The board 5 is gradually preheated to a preheating temperature, for example, about 150° C., and soldering is carried out in chamber 16 at a temperature of, for example, 23° C.
It is configured to heat up to 0°C all at once to melt the cream solder and perform soldering.

Further, a cooling fan 18 that blows cold air to cool the board 5 being transported after soldering and a cooling fan 19 that cools the transport member 12 are disposed above and below the transport device 2, respectively, and the machine frame 6 An exhaust pipe 6C is disposed above the board 5 to exhaust smoke, gas, etc. generated when the board 5 is heated and soldered.

The method of the present invention (claim 1) includes loading and transporting the board 5 on which the electronic components 4 are mounted in close contact with the upper surface 12a of the transporting device 2 whose upper surface 12a is formed into a planar shape, and heating the transporting device 2. In this method, the heat of the substrate 5 is conducted from the transport device 2 to uniformly heat the substrate 5.

Function The present invention is constructed as described above, and its function will be explained below. In FIG. 1, sprocket 10
The board 5 coated with cream solder is stacked in close contact with the upper surface 12a of the transport member 12 of the transport device 2, which is wound around the board and driven in the direction of the arrow. Referring also to FIGS. 2 to 4, the substrate 5 is transferred into the preheating chamber 15 by the transfer device 2, and the upper surface 5a of the substrate 5 and the electronic components 4 are heated by infrared rays emitted from the heater 13 above. At the same time, a heater 13 disposed below the conveying device 2
2 to a high temperature, the lower surface 5b of the substrate 5 is heated by the heat conducted from the conveying member, but the distance between the upper surface 5a of the substrate 5 and the heater 13 above is 50 to 801 m.
Since the board 5 is set to However, the temperature tends to be low and temperature unevenness tends to occur.

What compensates for this is the lower heater 13, which is disposed close to 5 to 10 m1 from the conveying member 12.
Although the conveying member 12 is rapidly heated to a high temperature, the conveying member 12
Since the heat capacity of is much larger than that of the net (not shown) which is the conveying member 12 of the conventional device, the entire conveying member is uniformly heated without any temperature unevenness, and all parts have approximately the same temperature.

Since the substrate 5 is stacked closely on the top surface 12a of the uniformly heated carrier member 12 in order to improve heat conduction efficiency, heat is conducted from the carrier member 12 to the substrate 5 and the electronic components on the substrate 5 are stacked. 4 is also heated uniformly from the lower surface 5b of the substrate 5, and the entire surface of the substrate 5 is heated to approximately the same temperature.

The electric power supplied to each of the heaters 13 disposed in the three preheating chambers 15 shown in FIG. It is controlled by a control device (not shown) to supply increasing power as it goes downstream in the transport direction (direction of arrow A) so that the temperature reaches .degree.

The substrates 5 heated evenly to the preheating temperature in the three preheating chambers 15 are transferred to the soldering chamber 16 by the transfer device 2 . During the soldering process, since the heater 13 in the chamber is supplied with a higher power than the heater 13 in the preheating chamber 15 by the control device, the upper surface 5a is soldered directly and the lower surface 5b is soldered in the same manner as described above. The entire surface of the board 5 is uniformly heated to a temperature of 230° C. to 250° C., for example, via the conveying member 12 heated to a high temperature.

As a result, the cream solder applied to the necessary soldering points (not shown) on the board 5 is melted and soldered at almost the same time, so there is no solder melting failure caused by temperature unevenness, and the board 5 The electronic components 4 on the entire surface are soldered under the same good conditions.

The soldered board 5 is further transported in the direction of arrow A, and is cooled by cold air discharged from the cooling fan 18. On the other hand, the conveying member 12 is also cooled by the cold air discharged from the cooling fan 19, and then guided by the sprocket 10 to change the conveying direction to the direction of arrow B, and then gradually releases the remaining heat into the air at room temperature. Return to the original position, 1
The general feeding direction is changed to the incoming direction again to prepare for the next substrate 5 to be transferred.

In addition, in the above embodiment, the automatic soldering apparatus 1 was explained as a reflow soldering apparatus, but the automatic soldering apparatus 1 is not limited to a reflow soldering apparatus, and the flow soldering apparatus is a reflow soldering apparatus. It may be.

Effects As described above, the present invention forms the top surface of a transfer device into a flat shape, loads and transfers substrates by bringing them into close contact with the top surface, and actively heats the transfer device to transfer heat from the transfer device to the substrates. Since the entire surface of the board is heated uniformly by conduction, the cream solder is melted uniformly on all parts of the board, allowing high-performance soldering with no variation in performance. It has the effect of This also has the effect of increasing the reliability of the completed board. Furthermore, since the substrate is heated uniformly and gradually, it is possible to prevent the substrate from cracking or warping due to heat shock, and it is also possible to prevent changes in the electrical characteristics of electronic components. Furthermore, since no special equipment or material is used as a heat medium, the equipment can be made smaller and high-performance soldering can be performed at low cost.

[BRIEF DESCRIPTION OF THE DRAWINGS] The drawings relate to embodiments of the present invention, and FIG. 1 is a longitudinal sectional view showing the entire automatic soldering device, and FIG. 2 is a longitudinal sectional view taken along the line nn in FIG. 1. , FIG. 3 is an enlarged perspective view of the main parts showing the conveying device and the heater, FIG. 4 is an enlarged longitudinal cross-sectional view of the main parts, and FIG. 5 is a longitudinal cross-sectional view showing another embodiment of the transport member. 1 is an automatic soldering device, 2 is a conveyance device, 3 is a heating device,
4 is an electronic component, 5 is a substrate, 12 is a conveyance member, 12a is an upper surface, 12d is a lower surface, 12e is a side surface, 12f is a fin, 2
0 is a substrate loading section.

Claims (1)

[Scope of Claims] 1. A board on which electronic components are mounted is loaded and transported in close contact with the upper surface of a transporting device whose upper surface is formed into a flat shape, and the electronic components are removed from the transporting device by heating the transporting device. An automatic soldering method characterized by uniformly heating the board by conducting heat to the board. 2. A transport device that loads and transports substrates on which electronic components are mounted in close contact with a planar upper surface, and a heating device that is disposed below the transport device and heats the transport device. Features automatic soldering equipment. 3. The automatic soldering apparatus according to claim 2, wherein the substrate loading section of the transport device is composed of a large number of flat transport members arranged adjacent to each other. 4. The substrate loading section of the transfer device is configured by arranging a large number of transfer members adjacent to each other, each of which has a planar upper surface and has fins formed on its lower and both side surfaces for good heat conduction. The automatic soldering device according to claim 2, characterized in that: 5. The automatic soldering apparatus according to claim 3 or 4, wherein the conveying member is made of one of aluminum, ceramics, and titanium alloy.