JPH0665651A - Device for removing impurity in solder - Google Patents

Abstract

PURPOSE:To efficiently and simply remove the impurities mixed in a solder in the manufacture of a printed wiring board. CONSTITUTION:A pipe assembly 10 having self-cooling function and self-heating function is dipped into the solder, and after heating the solder up to the m.p. or higher, the slow cooling is executed with the pipe assembly 10 and the impurities containing copper compounds are precipitated in the pipe assembly 10. The pipe assembly 10 is pulled out from the solder and inserted into a slag vessel 5 and the stuck impurities are melted by self-heating and dropped in the slag vessel 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for removing impurities from solder in a solder bath used in various processes for manufacturing printed wiring boards.

[0002]

2. Description of the Related Art In the manufacture of printed wiring boards, a solder bath is used in various processes such as a solder leveling process for attaching solder to a pad portion on an insulating substrate and a soldering process for mounting electronic components. In each of these steps,
Immerse the printed wiring board in the solder in the solder bath.During this immersion, copper is dissolved from the copper pattern parts such as pads and lands that are not covered with solder resist, and the copper-tin compound is soldered. In addition to being mixed inside, the flux and oil carbide adhering to the printed wiring board also mix. These are impurities of solder,
If the amount of the mixture increases, the state becomes unfavorable. In particular, when the content of copper is 0.3% or more, not only the solder wettability at the time of mounting a component is lowered, but also the melting point of the solder is increased and the use temperature of the solder is increased. This results in a vicious circle in which the dissolution of
Therefore, the copper contamination rate of 0.3% is used as a guideline for the contamination limit, and
If the content exceeds%, impurities are removed from the solder.

To remove such impurities, conventionally, the temperature of the solder is heated to 250 ° C. which is higher than the melting point and stirred, and after this stirring, the solder is cooled to about 190 to 230 ° C. to precipitate the impurities inside the solder. An operator scoops out the deposited impurities or replaces 1/2, 1/3 or all of the solder amount in the solder bath with new solder.

[0004]

However, in the method of scooping out impurities by the worker, there is a problem in safety and the workability is poor and it takes a long time to remove the impurities.
In addition, the method of partially replacing the solder cannot be reused, resulting in a waste of resources.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solder impurity removing apparatus which is simple, efficient, and safe, and which does not require solder replacement.

[0006]

In order to achieve the above object, the present invention provides a pipe composition having a self-cooling function and a self-heating function, a first tank in which solder is stored, and impurities. A second tank for storing, wherein the pipe composition is gradually cooled in a state where the pipe composition is immersed in the solder in the first tank, and impurities are deposited on the outer surface of the pipe composition,
The pipe is self-heated in the second tank to drop impurities into the second tank.

In the above structure, when the pipe composition is gradually cooled in the state of being immersed in solder, the impurities mainly composed of the copper-tin compound adhere to the outer surface of the pipe composition. Therefore, the impurities can be removed by extracting the pipe composition from the solder. On the other hand, the pipe composition to which the impurities are attached is heated by its self-heating function to melt and remove the impurities, and the pipe composition can be reused.

[0008]

The present invention will be described below with reference to the illustrated embodiments. FIG. 1 shows a system configuration of an embodiment of the present invention, and 1 is a solder bath used in a solder leveling process or a soldering process of printed wiring board manufacturing,
Impurities such as copper, flux, and oil carbide are mixed in the solder 2 due to repeated immersion of the printed wiring board. 3 is an impurity removing tank, which is a solder tank 1
This is the first tank to which the solder from is properly supplied.
In this removing tank 3, impurities are removed as will be described later. Reference numeral 4 is a storage tank for storing clean solder from which impurities have been removed by the removal tank 3, 5 is a slug tank, and a second tank for storing impurities 6.

In such a system, as shown by a solid arrow, the solder 2 containing a predetermined amount of impurities is transferred to the removal tank 3, the impurities are removed in the removal tank 3, and the solder from which the impurities are removed is stored in the storage tank 4 To the solder bath 1 to carry out the circulating action, and the removed impurities 6 are taken out to the slag bath 5. Not limited to this,
After removing the impurities in the removal tank 3, the solder may be back-transferred from the removal tank 3 to the solder tank 1 as shown by a dashed arrow, or the impurities may be directly removed in the solder tank 1. In the case of, since the number of tanks is reduced, the system configuration becomes simple. A pump or a gravity difference may be used to transfer the solder between the baths.

2 and 3 show a pipe composition 10 used to remove impurities. This pipe composition body 10 has a cage structure in which long pipe bodies 11 are assembled on the bottom surface and four side surfaces excluding the top surface in a zigzag manner. As shown in FIG. 3, the pipe body 11 has a double pipe structure including an inner pipe 12 and an outer pipe 13. A cooling medium such as glycerin or water is supplied into the inner pipe 12, and the pipe body 11 is cooled by the supply of the cooling medium. As a result, the entire pipe composition 10 is self-cooled. 14
Is a heating wire wound around the outer surface of the inner pipe 12, and is provided so as to also contact the inner surface of the outer pipe 13. By supplying power to the heating wire 14, the heating wire 14 generates heat, so that the pipe body 11 is heated. As a result, the entire pipe composition 10 is self-heated. In such a pipe composition 10, the impurities mixed in the solder are deposited on the outer surface by self-cooling, and the deposited impurities are dissolved and removed by the self-heating. Further, in the self heating, it is also possible to heat the solder in the solder bath 1 or the removal bath 3. In the illustrated pipe composition body 10, the pipe body 11 is assembled in a zigzag shape, but the pipe composition body 10 is not limited to this and may be assembled in a mesh shape, a spiral shape, or another shape.

Next, a procedure for removing impurities from solder according to this embodiment will be described. By repeating the immersion of the printed wiring board in the solder bath 1, when the copper content in the solder 2 becomes 0.3% or more, all of the solder 2 in the solder bath 1 is transferred to the removal bath 3. In this case, the copper content is measured by atomic absorption analysis. In the removing tank 3, the soldering temperature (for example, 245
10 ° C to 15 ° C higher than (° C) (eg 260
The solder is heated with a heater so that the temperature becomes ℃). At this time,
As shown in FIG. 4, the pipe composition 10 is immersed in the solder in the removing tank 3. At this time, the heating wire 14 of the pipe composition 10
You may make heat generate and assist heating. Pipe composition 10
The solder may be heated alone.

After the solder in the removing tank 3 reaches a predetermined temperature, the heating is stopped and a cooling medium (for example, glycerin at 25 ° C.) is supplied into the inner pipe 12 of the pipe composition 10 to form a pipe composition. By circulating the inside of 10, the solder in the removing tank 3 is gradually cooled. This gradual cooling is performed until the solder in the removal tank 3 reaches, for example, about 200 ° C., and by this gradual cooling, needle crystals of the copper-tin compound are deposited and adhere to the outer surface of the pipe composition 10. In addition, following the precipitation of the copper-tin compound, oil carbide and flux are also simultaneously collected in the pipe composition 1.
It adheres to the outer surface of 0. As a result, impurities are removed from the solder in the removing tank 3.

The pipe composition 10 with the impurities thus adhered is extracted from the removal tank 3, conveyed to the slug tank 5, and introduced into the slug tank 5 as shown in FIG. Then, the pipe composition 10 is heated to, for example, about 200 ° C. by supplying power to the heating wire 14 to generate heat. By this heating, the copper-tin compound adhering to the outer surface of the pipe composition 10 is melted to form droplets 20 and drop into the slag tank 5, along with which oil carbide and flux also drop into the slag tank 5. On the other hand, the solder that has been cleaned by removing the copper compound is transferred from the removal tank 3 to the storage tank 4,
After being heated to a predetermined temperature in the storage tank 4, it is transferred back to the solder tank 1 and circulated and used for manufacturing a printed wiring board. Incidentally, the copper content of the solder transferred back to the solder bath 1 is 0.3 when the copper content in the initial solder bath 1 is 0.32%.
It is 04%, and can be recycled and used in a clean state of 1/8 or less.

In this embodiment as described above, impurities adhere to the pipe composition to efficiently remove the impurities from the solder, the removal work is simple and safe, and the solder can be circulated.

The present invention is not limited to the above embodiment, but various modifications can be made. For example, the impurities may be removed by the pipe composition 10 directly in the solder bath 1.
The pipe composition 10 may be self-heated by supplying a heating fluid, and the pipe composition 10 has a single-tube structure.
The cooling fluid and the heating fluid may be switched and supplied to self-cool and self-heat. Moreover,
The operation of removing impurities may be repeated a plurality of times.

[0016]

As described above, according to the impurity removing apparatus of the present invention, the impurities are removed from the solder by precipitating the impurities on the outer surface of the pipe composition by the self-cooling of the pipe composition, and the self-heating of the pipe composition. Since the impurities are melted and removed by, the impurities can be removed from the solder efficiently and easily, and at the same time, the solder can be circulated and reused.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an embodiment of the present invention.

FIG. 2 is a perspective view of a pipe composition.

FIG. 3 is a partially cutaway perspective view showing the internal structure of the pipe composition.

FIG. 4 is a cross-sectional view showing an operation in a removal tank.

FIG. 5 is a sectional view showing an operation in a slug tank.

[Explanation of symbols]

 1 Solder Tank 2 Solder 3 Removal Tank 4 Storage Tank 5 Slug Tank 6 Impurity 10 Pipe Composition 11 Pipe Body

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Isamu Kubo 1106 Fujikubo Fujikubo, Miyoshi-cho, Iruma-gun, Saitama Japan CMK Corporation (72) Ryoichi Sugano 1106 Fujikubo Miyoshi-cho, Iruma-gun, Saitama Japan CMK Corporation

Claims (1)

[Claims] 1. A solder in the first tank, comprising a pipe composition having a self-cooling function and a self-heating function, a first tank in which solder is stored, and a second tank in which impurities are stored. The pipe composition is gradually cooled in a state where the pipe composition is soaked to deposit impurities on the outer surface of the pipe composition, and the pipe is self-heated in the second tank to drop the impurities into the second tank. An apparatus for removing impurities from solder, characterized by: