JPH0314546B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a vapor reflow soldering device, and particularly relates to a so-called flat pack IC, which has electrode terminals extending flat in four directions.
This invention relates to a soldering device suitable for high-density mounting using surface-mounted chip components such as resistors and capacitors.

[Conventional technology]

In recent years, the high-density mounting of electronic components on printed wiring boards has become more and more advanced, but since the soldering process for bonding electronic components such as semiconductors and chip parts to printed wiring boards is the final process of the line, it is important to know whether the soldering is good or not. Since it affects the performance of parts,
Soldering technology has come to be seen as the most important technology on the line. 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 density 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 tank called a vapor reflow tank, which performs soldering by passing the soldering process through the vapor reflow tank.

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

In FIG. 7, the apparatus includes a steam generation tank 4, a carry-in side conveyance path 5, a carry-out side conveyance path 6, a heating heater 7, a carry-in side upper and lower coolers 8 and 10, an output side upper and lower coolers 9 and 11, Carrying-in side exhaust port 12, discharge side exhaust port 1
a reflow chamber 1 consisting of 3, a preheating chamber 2 consisting of a preheating heater 16, 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, an output roller 23, etc., and a recovery device 25. , a heat medium recovery system including a hydroxyl remover 26.

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

The saturated steam 15 of the heat medium 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 of the steam generation tank 4 and is separated from the soldering member 18 to which the solder is attached. The material to be processed is heated, and a portion of the material is condensed and liquefied, falls, and accumulates at the bottom of the steam generation tank 4. The saturated steam 15 flowing out from the steam generation tank 4 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 coolers 8 and 10 and the discharge side upper and lower coolers 9 and 11. , returns to the bottom of the steam generation tank 4 through the return pipe 19. The slight amount of steam remaining is removed from the exhaust port 1 on the carry-in side.
2 and the discharge side exhaust port 13 through the pipe 24 into the recovery device 25, and is recovered by the cooling coil 26 and the demister 27. Hydroxy acid is removed from the recovered heat medium by a hydric acid remover 28, and the heat medium is returned to the bottom of the steam generation tank 4 by a pump 29.

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

As mentioned above, the height of the saturated steam 15 in the conventional steam generation tank 4 is controlled by a power controller such that the height of the saturated steam 15 in the conventional steam generation tank 4 is adjusted to a predetermined temperature by the temperature sensor 30 and the temperature controller 31 that are immovably provided in the steam generation tank 4. 32 to the heater 7, or by providing a cooler above the steam generating tank 4, the power is controlled so as not to exceed a certain level.

[Problem that the invention seeks to solve]

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

1. Even though the heat load on the soldering parts varies depending on the thickness and size of the board and the number and size of components to be mounted, the height of the saturated steam 15 is constant and sufficient to match the soldering parts with a large heat load. There is a lot of leeway. Therefore, in the case of soldering parts with a small heat load, the electric power of the heater 7 becomes excessive, but the amount of cooling water to the cooling coil is constant, and the amount of heat medium recovered by the recovery device 25 increases. This also increases dissipation into the atmosphere, reducing economic efficiency.

2 The height of the saturated steam 15 in the steam generation tank 4 is matched to the soldering parts with a large heat load, so when the soldering parts with a small heat load are brought into the area of the saturated steam 15, the saturated steam 15
Since the latent heat taken away from the solder is small, the decrease in the height of the saturated steam 15 is small. Therefore, the reflow time (generally the time during which the soldering member 18 passes through a temperature region higher than the melting temperature of the solder) The heating time is too long for the attachment member 18, and the heating time for the mounted electronic components whose heating time should be shortened as much as possible becomes long.

3 Conventionally, the conveyor speed was increased to shorten the reflow time of solder for soldering parts with a small heat load, but this also shortened the cooling time after reflow, resulting in insufficient cooling of the solder. , the solder becomes structurally rough and its strength decreases. In addition, even if the temperature rise is suppressed by increasing the conveyor speed and shortening the heating time of the soldering member 18 and the solder, the cooling time also becomes shorter and the temperature is not sufficiently cooled, so the time at which the solder is at a temperature higher than the melting temperature of the solder increases. is not shortened.

Furthermore, as the speed of the conveyor increases, the amount of saturated steam 15 taken out to the conveyance path on the discharge side increases, and the amount that is not condensed and recovered in the upper and lower coolers 9 and 11 on the discharge side also increases, and the amount is transferred from the discharge side exhaust port 13 to the recovery device. Not only does the amount of recovered steam to be recovered increase, but the amount of steam that is not recovered and dissipates into the atmosphere also increases, reducing economic efficiency.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vapor reflow soldering device that improves the reliability and economy of soldering and prevents mounted components from heating.

[Means for solving problems]

The above purpose is to provide a temperature sensor that can be supported at a desired height according to the heat load of the soldering member and a position detector that generates a control signal according to the support height of the temperature sensor in the steam generation tank. This is achieved by controlling the heater, cooler, and recovery device using signals from the temperature sensor and position detector so as not to affect the reflow time of the soldered parts.

[Effect]

A temperature sensor installed in the steam generation tank is supported at a desired height depending on the heat load of the soldering parts, and the power of the heater, the amount of cooling water flowing to the lower cooler on the conveyor path, and the amount of cooling water are adjusted accordingly. By making it possible to control the distance through which the heat medium is flowed and the exhaust volume of the heat medium recovery device,
The solder reflow time can be kept almost constant by saving the amount of power and cooling water and reducing the amount of heat medium dissipated, and the reliability of soldering between the soldering member and the mounted component can be improved.

〔Example〕

Hereinafter, specific embodiments of the present invention will be described in detail using FIGS. 1 to 7.

In FIG. 1, the soldering member 18 is conveyed horizontally,
Consisting of a preheating chamber 2, a reflow chamber 1, and a cooling chamber 3, there is a temperature sensor 30 that can be supported at any height above the steam generation tank 4, and a power regulator that adjusts the power of the heater according to the temperature detected by the temperature sensor. 32 and
An embodiment of the present invention is shown in which a position detector 34 that generates a signal according to the support height of the temperature sensor and flow control valves 35 and 36 controlled by the position detector 34 are provided.

The equipment includes a steam generation tank 4, a carry-in side conveyance path 5, a carry-out side conveyance path 6, a heating heater 7, a carry-in side upper and lower coolers 8 and 10, an carry-out side upper and lower coolers 9 and 11, and a carry-in side exhaust port 12. , a reflow chamber 1 consisting of a discharge port 13, a preheating chamber 2 consisting of a preheating heater 16, a cooling chamber 3 consisting of a cooling jacket 20, and a conveyor 1.
7, drive roller 21, loading/unloading side roller 22,
23, etc., a recovery device 25, a hydric acid remover 28, a heat medium recovery system including a pump 29, a temperature sensor 30, a temperature regulator 31, a power regulator 32,
It is composed of a control system including a temperature sensor support device 33, a position detector 34, flow control valves 35 and 36, and the like.

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

It is heated to a predetermined temperature in the preheating chamber 2 and transferred to the conveyor 1.
Soldering member 1 carried into reflow chamber 1 at 7
8 is heated by contact with saturated steam 15, and in the steam generating tank 4, the solder of the soldering member 18 is melted by the latent heat of condensation of the saturated steam 15, and the members 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.

In this embodiment, the support device 33 of the screw and nut fastening type is
When you change the height of the temperature sensor 30 by operating
The temperature controller 3 is activated by the detection signal of the temperature sensor 30.
1 adjusts the power of the heater 7 via the power regulator 32 so that the steam reaches a desired height. The amount of cooling water in the upper and lower coolers 9 and 11 on the discharge side can be adjusted to prevent excessive cooling, thereby saving cooling water. Furthermore, since the discharge-side upper cooler 9 or the discharge-side lower cooler 11 is not excessively cooled, moisture in the atmosphere present in the reflow chamber 1 does not condense. The support device 33 does not have to be of a screw and nut type.

In this embodiment, an example is shown in which the amount of cooling water in the carry-out side cooler is adjusted, but the present invention can be similarly applied to the carry-in side cooler.

Figure 2 shows the temperature changes at the soldering point while passing through the preheating chamber 2, reflow chamber 1, and cooling chamber 3. Figure 7 shows the conventional vapor reflow soldering device in which the height of the steam is constant. The dotted line shows the case where a soldering member with a small heat load is reflowed, and the reflow time is longer than the case where the heat load is large, which is shown with a solid line.

Figure 3 shows the temperature change when the steam height is lowered to suit soldering components with a small heat load.As shown by the dotted line, the reflow time can be shortened by lowering the steam height. can.

In FIGS. 2 and 3, line A indicates the solder melting temperature, t ₁ indicates the reflow time with a large heat load, and t ₂ indicates the reflow time with a small heat load.

In FIG. 4, two temperature sensors 30 and 37 with different support heights are fixedly provided in the steam generation tank 4, which is composed of a preheating chamber 2, a reflow chamber 1, and a cooling chamber 3. , 37 is selected and switched, and the flow control valve 3 is switched by the signal from the position detector 34.
5 and 36 are shown to show an embodiment of the present invention in which the amount of cooling water in the discharge side cooler is changed in stages by controlling the flow rate. This embodiment is the same as FIG. 4 except that it uses two selectable temperature sensors, and the steam height can be adjusted by switching a selection switch.

In FIG. 5, two temperature sensors 30 and 37 with different support heights are provided in the steam generation tank 4, which is composed of a preheating chamber 2, a reflow chamber 1, and a cooling chamber 3, and the height of the selected temperature sensor 30 or 37 is An embodiment of the present invention is shown in which not only the amount of cooling water in the discharge side cooler but also the exhaust amount of the recovery device is changed stepwise by the exhaust amount control valve 38 according to the amount of cooling water in the discharge side cooler.

In this embodiment, an exhaust amount control valve 38 is added to the embodiment shown in FIG. By adjusting the amount of cooling water in the cooler and the amount of exhaust gas in the recovery device, overcooling of the conveyance paths 5 and 6 can be prevented, and condensation of moisture in the recovery device and dissipation of the heat medium can be reduced.

As shown in FIG. 6, temperature sensors 30 and 37 with different support heights are fixedly provided in the steam generation tank 4, and are selectively switched according to the heat load. Opening and closing the cooling water flow valves 35 and 36 to change the flow length of the cooling water to change the flow length of the cooling water to save the cooling water and prevent excessive cooling, as well as to reduce the atmosphere existing in the reflow chamber 1. can prevent condensation of moisture contained in

In this embodiment, the water flow valves 35 and 36 are used to adjust the flow rate in the latter half of the cooling pipe of the discharge side cooler, and the length of the cooling pipe can be selected in stages. The distribution of steam is mountain-like as shown in Figure 1, so the same effect can be obtained by changing the position of the temperature sensor in the direction of transport and controlling it by the amount of movement to detect the height of the steam. play.

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

1 When reflowing soldering parts with different heat loads (especially when the heat load is small), changing the steam height according to the heat load will keep the reflow time constant and improve the reliability of soldering. This eliminates the problem of overheating the mounted electronic components.

2. When transporting soldering parts in a horizontal state, the present invention heats the entire soldering part, but achieves a short reflow time comparable to laser methods and hot blowing methods that locally heat only the soldering parts. can.

3. Electric power is saved because the amount of power supplied to the heater is determined according to the heat load of the soldering parts, and cooling water is also saved because the amount of cooling water in the lower cooler on the conveyor path or the length of the cooling water flowing is changed. This also improves economic efficiency.

In addition, if the heat load on the soldering parts is small, the surface temperature of the cooling coil of the cooler will become too low, and the moisture in the atmosphere in the reflow chamber 1 will condense, producing hydric acid and It can prevent water from entering and water vapor from entering electronic components during reflow, improving reliability.

4. By setting the steam height according to the heat load on the soldering parts, we have prevented excessive cooling by the cooler, and we have also changed the exhaust volume of the recovery device, so that less steam is dissipated from the recovery device into the atmosphere. The cost of expensive heat medium can be reduced, improving the economic efficiency of the device.

〔Effect of the invention〕

According to the present invention, it is possible to control the height of steam, the water amount or cooling length of the cooler, and even the exhaust of the recovery device according to the heat load on the soldering parts, so the reflow time does not change depending on the heat load. This improves soldering reliability and prevents overheating of the components mounted on the soldering member.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the overall configuration of a vapor reflow soldering device that can control the heater and cooler water volume according to an embodiment of the present invention, and Figs. 2 and 3 show the soldering portion of the soldering member. Figure 4 shows an example in which two temperature sensors are selectively fixed and the heater and cooler water volume can be controlled, and Figure 5 shows two temperature sensors. Fig. 6 shows an embodiment in which two temperature sensors are selectively fixed and installed to control the heater, cooler water volume, and recovery device exhaust volume. 7 shows an embodiment in which the flow length of the cooling water of the heater and the cooler can be controlled, and FIG. 7 is a diagram of a typical conventional vapor reflow soldering apparatus. 1...Reflow room, 2...Preheating room, 3...Cooling room, 4...Steam generation tank, 5...Carry-in side conveyance path, 6
...Export side conveyance path, 7...Heater, 14...
Heat medium, 15... Saturated steam, 17... Conveyor,
18...Soldering member, 25...Recovery device, 2
8... Hydroxy acid remover, 30... Temperature sensor, 31
...Temperature controller, 34...Position detector.

Claims (1)

[Scope of Claims] 1. A steam generation tank that performs soldering by bringing saturated steam of a heat medium into contact with a workpiece conveyed by a conveyor, chain, etc. to heat and melt the solder of the workpiece, and the steam In a vapor reflow soldering apparatus, the workpiece conveyance path has a cooler that cools and liquefies surplus saturated vapor from a generation tank, and a heat medium recovery device that prevents the saturated vapor from escaping into the atmosphere. , in the steam generation tank, a temperature sensor for detecting the temperature of the saturated steam supported at a desired height corresponding to the workpieces having different heat loads; and a temperature sensor corresponding to the detected temperature of the temperature sensor. a temperature regulator that generates a signal, a power regulator that is controlled by the signal from the temperature regulator, a position detector that detects the support height of the temperature sensor, and a power regulator that is controlled by the signal from the position detector. A vapor reflow soldering apparatus characterized in that a vapor reflow soldering apparatus is provided with a cooling water flow valve for the cooler. 2. A steam generation tank for soldering by heating and melting the solder of the workpiece by bringing saturated steam of a heating medium into contact with the workpiece being transported by a conveyor, chain, etc., and In the vapor reflow soldering apparatus, the vapor reflow soldering apparatus includes the workpiece conveyance path having a cooler that cools and liquefies the saturated steam, and a heat medium recovery device that prevents the saturated steam from escaping into the atmosphere. a temperature sensor for detecting the temperature of the saturated steam supported at a desired height corresponding to the workpiece having a different heat load; and a temperature sensor for generating a signal in response to the detected temperature value of the temperature sensor. a temperature regulator; a power regulator controlled by a signal from the temperature regulator; a position detector for detecting the support height of the temperature sensor; and a power regulator controlled by a signal from the position detector. A vapor reflow soldering apparatus, characterized in that it is provided with a cooling water flow valve and a displacement control valve for the heat medium recovery device, which is controlled by a signal from the position detector.