JPH0245948B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a vapor reflow soldering device, and relates to a printed wiring board, particularly a so-called flat pack element and resistor in which electrode terminals are taken out in a flat manner in four directions. The present invention relates to a vapor reflow soldering apparatus suitable for soldering high-density mounted printed wiring boards using semiconductor chip components such as capacitors.

[Conventional technology]

In recent years, high-density mounting of electronic components onto printed wiring boards has progressed more and more, but since the soldering process for bonding electronic components such as semiconductor chips to printed wiring boards is the final process on the line, the quality of the soldering depends on the quality of the soldering. Soldering technology has come to be seen as the most important technology on the line, as it affects the performance of the product. Recently, due to the need to improve the uniformity of temperature distribution in the furnace where soldering work is carried out and to avoid harmful overheating of electronic components, steam with a high specific gravity relative to air has been used as a heat medium and its latent heat of condensation has been utilized. Vapor reflow soldering equipment, which heats the workpiece using a vapor reflow method, is attracting attention. This device, as described in JP-A-60-106502, for example, mounts electronic components on the solder pattern of a printed wiring board, and as described above, the printed wiring board is heated using saturated steam of a heat medium having a high specific gravity relative to air. This is a soldering device equipped with a vapor generating tank called a vapor reflow tank, which heats and melts solder by passing it through the solder and solders electronic components onto printed wiring.

First, a typical conventional vapor reflow soldering apparatus using a belt conveyor will be described with reference to FIG.

In FIG. 9, the apparatus includes a steam generation tank 4, a carry-in side conveyance path 5, a carry-out side conveyance path 6, a heater 7, upper and lower cooling coils 8 and 10 on the carry-in side, upper and lower cooling coils 9 and 11 on the carry-out side, A reflow chamber 1 consisting of a transfer side exhaust port 12 and a carry-out side exhaust port 13, and a preheating heater 1
6, a cooling chamber 3 consisting of a cooling jacket 20, a drive system including a conveyor 17, a drive roller 21, an input roller 22, a conveyance roller 23, etc., a recovery device 25, and a hydroxyl remover 29. It consists of a media recovery system.

The operation of the vapor reflow soldering apparatus configured as described above will be explained.

The saturated steam 15 of the heat medium that is boiled and evaporated by the heater 7 immersed in the heat medium 14 accumulated at the bottom of the steam generation tank 4 rises to the top, and the soldering member 1
8 is heated, a part of it condenses and falls, and accumulates at the bottom of the steam generation tank 4. The saturated steam 15 flowing into the carry-in side conveyance path 5 and the carry-out side conveyance path 6 is cooled and liquefied by the carry-in side upper and lower cooling coils 8 and 10 and the carry-out side upper and lower cooling coils 9 and 11,
It returns to the bottom of the steam generation tank 4 through the return pipe 19. The little remaining steam flows from the carry-in side exhaust port 12 and the carry-out side exhaust port 13 through the piping 24 to the recovery device 25, and is then passed through the cooling coil 26 and the demister 2.
Recovered by 7. Hydroxy acid is removed from the recovered heat medium 28 by a hydric acid remover 29, and the heat medium 28 is returned to the bottom of the steam generation tank 4 by a pump 30.

On the other hand, the soldering parts 18 heated by the preheating heater 16 and carried from the preheating chamber 2 to the reflow chamber 1 by the conveyor 17 are heated by contact with the saturated steam 15, and in the steam generation tank 4, due to the latent heat of condensation of the saturated steam 15. The solder is heated and melted, and the components are soldered together. The soldering member 18 is cooled as soon as it enters the discharge-side conveyance path 6, enters the cooling chamber 3, is further cooled by the cooling jacket 20, and is discharged from the apparatus.

[Problem to be solved by the invention]

In the vapor reflow soldering apparatus as described above, the following problems occur.

1 In the recovery device 25, the heat medium that has been condensed and liquefied by the cooling coil 26 or captured by the demister is further removed with hydroxyl by a hydroxyl remover, and then
It is intermittently sent to the steam generation tank by a pump.
At this time, the temperature of the heating medium is 30 to 40°C, which is close to room temperature, so if a heating medium close to room temperature is mixed into the steam generating tank that is boiling and evaporating at a temperature of 215 to 220°C, the capacity of the heater will decrease. If there is not a large margin, the temperature of the heat medium at the bottom of the steam generation tank will drop temporarily. Therefore, the amount of saturated steam decreases, and in some cases, if the amount of saturated steam necessary for soldering is insufficient, soldering may not be possible locally, reducing the productivity and reliability of the device. .

2. The viscosity of the heat medium at room temperature is 10 to 15 times higher than that of water, so the fluid resistance of piping, valves, etc. is large, and it takes a long time to respond to a drop in the liquid level in the steam generation tank.

Therefore, the capacity of the steam generation tank must be increased to provide a large margin for the limit value of the liquid level, and a large amount of expensive heat medium is always stored at the bottom of the steam generation tank, which is not economical.

3. If the capacity of the steam generation tank is to be made as small as possible for economical reasons, it is sufficient to send a small amount of heat medium frequently to prevent a temporary drop in the temperature of the heat medium at the bottom of the steam generation tank. This increases the number of times the pump starts and stops, shortens the life of the pump and electromagnetic switch, and reduces reliability.

4 When a heat medium at near room temperature is placed at the bottom of the steam generation tank, the amount of saturated steam is temporarily reduced and the liquid temperature is
Requires sensible heat up to 215℃. From liquid temperature 40℃
Since the sensible heat up to 215°C is 2.7 times the latent heat, the amount of heat required for sensible heat cannot be ignored, and economic efficiency decreases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vapor reflow soldering device that improves reliability and achieves good economic efficiency by preventing fluctuations that would reduce the amount of steam generated. It is in.

[Means to solve the problem]

The above purpose is achieved by providing heat exchange means for preheating the room temperature heat medium by exchanging heat between the room temperature heat medium and the high temperature heat medium vapor, or by providing a heat exchange means in the cooler chamber or on the inner wall side of the conveyance path or on the conveyance path; This is achieved by providing a heat exchange means between the cooler chamber and the hydroxyl remover for exchanging heat between the heat medium and the high temperature heat medium to preheat the room temperature heat medium.

[Effect]

On the way from the hydrochloric acid remover to the bottom of the steam generation tank,
The heating medium at room temperature is heated to near its boiling point by preheating through heat exchange with high-temperature saturated steam or high-temperature heating medium, so the temperature of the heating medium at the bottom of the steam generation tank decreases little, and the energy required for heating is small. can also be reduced.

〔Example〕

Hereinafter, specific embodiments of the present invention will be described in detail using FIGS. 1 to 8.

FIG. 1 shows an embodiment of the present invention in which a heat exchange means consisting of a preheating chamber, a reflow chamber, and a cooling chamber is provided in the lower cooler of the conveyance path on the discharge side. Figure 2 is A-A of Figure 1.
It is a line arrow view.

The device includes a steam generation tank 4, a conveyance path 5 on the carry-in side, a conveyance path 6 on the carry-out side, a heater 7, upper and lower cooling coils 8 and 10 on the carry-in side, and upper and lower cooling coils 9 and 1 on the carry-out side.
1. A reflow chamber 1 consisting of a carry-in side exhaust port 12 and a carry-out side exhaust port 13, a preheating chamber 2 consisting of a preheating heater 16, a cooling chamber 3 consisting of a cooling jacket 20, a conveyor 17, a drive roller 21, and carry-in and carry-out side rollers 22. , 23, a heat medium recovery system including a recovery device 25, a hydroxyl remover 29, and a pump 30.

The operation of the vapor reflow soldering apparatus of this embodiment configured as described above will be explained.

The saturated steam 15 as a heating medium is condensed and liquefied or captured in a recovery device 25, separated from the atmosphere in a demister 27, and then removed with hydroxyl in a hydroxyl remover 29. When a certain amount has accumulated, it is removed to a level. The switch senses this and starts the pump 30. The heat medium is sent by the pump 30 to a tubular heating coil 32 provided in the cooler chamber 11', and after preheating, the heat medium is transferred to the cooler chamber 11'.
is extruded. On the other hand, a part of the saturated steam 15 that has entered the conveyance path enters the cooler chamber 11', heats the heat medium in the heating coil 32, and is then condensed and liquefied by the lower cooling coil 11. In the cooler room 11',
The heat medium preheated by the heating coil 32 and the heat medium condensed and liquefied by the lower cooling coil 11 are mixed and returned to the bottom of the steam generation tank 4 through the return pipe 19. When the level of the heat medium reaches a predetermined value, the level switch senses this and stops the pump 30, ending the series of cycles.

In addition, in FIG. 1, the heating coil 32 is placed on the unloading side.
Although an example has been shown in which the heat medium recovery system is provided at the bottom, it is similar to provide the heating coil on the carry-in side and the heat medium recovery system at the top, which is a design problem.

FIG. 3 shows an embodiment of the present invention in which a heating coil 32 is provided on the side wall side of the conveyance path on the discharge side. Figure 4 is the third
It is a BB line arrow view of a figure.

Since the structure and operation of the device are almost the same as those shown in FIGS. 1 and 2, detailed explanation will be omitted.

FIG. 5 shows an embodiment of the present invention in which a heating coil 32 is provided at the upper part of the conveyance path on the discharge side. FIG. 6 is a view taken along the line C--C in FIG. 5.

Since the structure and operation of the device are almost the same as those shown in FIGS. 1 and 2, detailed explanation will be omitted here.

FIG. 7 shows an embodiment of the present invention in which the heat medium sent by the pump 30 is heated by the liquefied heat medium generated by the soldering member 18. FIG. 8 is a view taken along the line D--D in FIG. 7.

The apparatus is constructed by adding a saucer 33 for collecting the condensed and liquefied heat medium containing flux in the steam generating tank 4 described above, and a pipe 34 leading to the heating coil 32.

The saturated steam 15 that has heated the soldering member 18 in the reflow chamber 1 liquefies and condenses on the soldering member 18 and falls into the steam generation tank 4 together with flux. These liquefied heat carriers 14 are collected and captured on a saucer 33, enter a heating coil 32, heat the supply liquid at room temperature, and then flow into a filtering device (not shown). The action and condition of the heat medium for liquid supply are the same as in the previous embodiment.

According to the above configuration, the following effects are achieved.

1. Assuming that the amount recovered by the recovery device is 50% of the amount of liquid supplied, this corresponds to 5 to 10% of the heat medium in the steam generation tank. Sensible heat from room temperature (30℃) to 215℃ is 2.8 times the latent heat, so using the conventional method,
If the recovered liquid is directly returned to the steam generation tank, the amount of steam generated must be increased by 14 to 28%. According to the present invention, the required steam generation tank is about 5 to 10%, and usually there is a margin of this degree, so it is possible to almost avoid insufficient soldering due to insufficient steam.

2 The viscosity of the heat medium at room temperature (30℃) and 200℃ is approximately 20
Therefore, according to the present invention, the fluid resistance of piping, valves, etc. is reduced to 1/20, and the response time is also faster. Therefore, the limit value of the liquid level can be reduced, the amount of expensive heat medium can be reduced, and the economical efficiency can be improved.

3. According to the present invention, as described above, the power required for heating, which corresponds to 9 to 18% of the amount of steam generated, can be reduced, resulting in high economic efficiency.

4. Since a simple tube is sufficient for the heating coil according to the present invention, the increase in the cost of the device is minimal, the device is also extremely simple, and is highly economical.

5. Since the heating coils are installed where the saturated steam of the heat medium that is no longer needed is to be cooled, the cooling water can be saved by the amount of heat that should be used to heat the recovered liquid, making it highly economical.

〔Effect of the invention〕

According to the device of the present invention, since the heat medium is configured to exchange heat, the temperature of the heat medium in the steam generation tank is not lowered, and the necessary amount of steam is obtained for the soldering parts, so that soldering can be performed. Reliability is improved because it is done well.

In addition, since less energy is required for heating, it is highly economical.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the configuration of a vapor reflow soldering apparatus according to an embodiment of the present invention, and FIG.
The figure is a sectional view taken along the line A-A in FIG. 1, FIG. 3 is a sectional view showing another embodiment of the device of the present invention, and FIG.
5 is a sectional view showing another embodiment of the device of the present invention, and FIG. 6 is a sectional view taken along the line C--B in FIG.
7 is a sectional view showing another embodiment of the device of the present invention, FIG. 8 is a sectional view taken along the line D-D in FIG. 7, and FIG. 9 is a conventional vapor reflow type. FIG. 2 is a cross-sectional view showing the configuration of a soldering device. 1...Reflow room, 2...Preheating room, 3...Cooling room, 4...Steam generation tank, 5...Carry-in side conveyance path, 6
...Export side conveyance path, 14...Heat medium, 15...Saturated steam, 17...Conveyor, 18...Soldering member.

Claims (1)

[Scope of Claims] 1. A steam generation tank that performs soldering by bringing saturated steam as a heating medium into contact with a workpiece being conveyed by a conveyor to heat and melt the solder of the workpiece, and an inlet of the steam generation tank. a preheating chamber provided on the side, a cooling chamber provided on the outlet side of the steam generation tank, a transport path for the processed material provided on each of the inlet side and the exit side of the steam generation tank, and the transport path A heat medium recovery device including a cooler chamber having a cooling coil provided at each of the lower portions of the saturated steam and having a cooling coil for condensing the saturated steam, and a hydroxide remover for recovering the vapor of the heat medium from an outlet provided in each of the conveyance paths. In vapor reflow soldering equipment equipped with
A tubular heat exchange means is provided in the cooler chamber to preheat the heat medium that has been cooled to near room temperature in the heat medium recovery system by heat exchange with high-temperature heat medium vapor and to supply the preheated heat medium to the cooler chamber. A vapor reflow soldering device characterized by being installed in. 2. The vapor reflow soldering apparatus according to claim 1, wherein the heat exchange means is provided on the inner wall side of the conveyance path. 3. The vapor reflow soldering apparatus according to claim 1, wherein the heat exchange means is provided above the conveyance path. 4. A steam generation tank that performs soldering by bringing saturated steam of a heat medium into contact with the workpiece being transported by a conveyor to heat and melt the solder of the workpiece, and collecting the heat medium condensed and liquefied in the steam generation tank. a saucer, a preheating chamber provided at the inlet side of the steam generation tank, a cooling chamber provided at the outlet side of the steam generation tank, and the to-be-treated object provided at each of the inlet side and outlet side of the steam generation tank. The vapor of the heat medium is recovered from a conveyance path for the object, a cooler chamber provided at the lower part of the conveyance path and having a cooling coil for condensing the saturated steam, and a discharge port provided in each of the conveyance paths. In a vapor reflow soldering apparatus equipped with a heat medium recovery system including a hydroxyl remover, the heat medium that has been cooled to room temperature by the heat medium recovery system is heated with the high temperature heat medium collected in the saucer. A vapor reflow soldering apparatus characterized in that a heat exchange means of a tubular body that is preheated by exchange and supplied to the cooler chamber is provided between the cooler chamber and the hydroxyl remover.