JPS6082692A - Pretreatment for reflowing after tinning - Google Patents

Abstract

PURPOSE:To stabilize the quality of a tinned bar without leaving particles of treating chemicals on the surface of the bar by using an ammonium chloride- ammonia buffer soln. as a pretreating bath for reflowing after tinning. CONSTITUTION:An ammonium chloride-ammonia buffer soln. at ordinary temp. is prepd. as a pretreating soln. for reflowing. A copper alloy bar tinned in an acidic bath is pretreated by immersion in the soln., and the tin film on the surface of the pretreated bar is continuously melted by heating. By this method the tinned surface is stabilized without leaving particles of treating chemicals on the surface of the bar.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a pretreatment method for continuous reflow treatment or flow tin plating of copper alloy strips that have been tin-plated in an acidic tin plating bath. It is something.

[Prior art]

As a reflow tin plating method in which tin-plated strips are continuously subjected to reflow treatment, there is a method in which the steps of tin plating, water rinsing, flow pretreatment, water rinsing, drying, heating, cooling, and drying are performed. In this method, strips that have been subjected to plating pre-treatments such as degreasing and pickling, and base plating are tin-plated in an acid bath in the tin plating process, and after passing through a water washing process,
Reflow pretreatment is performed in the reflow pretreatment step. Subsequently, after a water washing process and a drying process, the tin plating film on the surface is heated and melted by an appropriate heating device in a heating process, and the molten tin is solidified again by a cooling process, which is used in the cooling process. After going through this process, it becomes a product. The role of the reflow pretreatment step in this series of culms is to stabilize the subsequent glue flow treatment, and if the reflow pretreatment is omitted, the gloss of the flow tin plating will deteriorate.

Conventionally, in the reflow treatment of a copper alloy strip plated in an acidic tin plating bath, there have been the methods shown in Table 1 as reflow pretreatment methods. Table 1 Trisodium phosphate (Na3 7.121120), which is a chemical used in the pretreatment method for glue flow tin plating, is a white crystal with a relatively low solubility in water, 5%
It appears as a white suspension in an aqueous solution.

Table 1 According to the pretreatment method for conventional glue flow tin plating shown in Table 1, strips tin-plated in an acid bath are
After passing through the water washing process, it enters the reflow pre-treatment tank and
Reflow pretreatment is performed by immersing it in a treatment bath of 5% sodium phosphate aqueous solution heated to 0°C. On this occasion,
The thin layer of acidic components adhering to the surface of the strip is removed and replaced with trisodium phosphate, thereby stabilizing the bright plating surface and stabilizing the reflow process.

However, in such a pre-treatment method for conventional adhesive flow tin plating, the trisodium phosphate suspended particles in the treatment solution strongly adhere to the surface of the strip material and cannot be completely removed by washing with water, so reflow treatment cannot be used. The disadvantage is that the heated and melted liquid tin incorporates trisodium phosphate particles, causing white spots to form in those areas, which impairs the appearance.

[Summary of the invention]

This invention was made with the aim of eliminating such drawbacks in the pretreatment method of the conventional adhesive flow tin plating method. By using an ammonium chloride-ammonia buffer solution as a reflow pretreatment bath, treating chemical particles are applied to the surface of the strip material. The present invention provides a pretreatment method for reflow tin plating that leaves no residue.

[Embodiments of the invention]

Hereinafter, a pretreatment method for reflow tin plating according to an embodiment of the present invention will be described. Details of the pretreatment method for reflow tin plating according to an embodiment of the present invention are shown in Table 2. The chemicals used in this example, ammonium chloride (NH4C1) and ammonia (NH,011), both have high solubility in water, and by changing the bath composition, any p+ ((8°0 to 11.0) You can also store buffer solutions.

Table 2 In the pre-treatment method for glue flow tin plating in this example, the copper alloy strip that has been tin-plated in an acidic bath is put into a reflow pre-treatment tank after passing through a water washing process, and is heated to a pH of 9 at room temperature. 2
The sample is immersed in a treatment bath containing an ammonium chloride-ammonia buffer solution to undergo reflow pretreatment. At this time, the thin layer of acidic components adhering to the surface of the strip is neutralized and removed, and replaced with a thin layer containing ammonium chloride-ammonia, thereby stabilizing the tin-plated surface. Ammonium chloride-ammonia adhering to the tin-plated surface is easily removed by washing with water. As a result, the drawback of white spots caused by suspended particles (attached to the tin plating surface) caused by the pretreatment method of the conventional adhesive flow tin plating method can be improved, and the reflow process is further stabilized. . In addition, in the glue flow tin plating pretreatment method of this example, since the treatment bath is a buffer solution, a constant pH value can be maintained for a long time even when other chemicals or water are mixed in. It can be stabilized or flow pre-treated. For this reason, according to the pretreatment method of the reflow tin plating method described above, ammonium chloride-AmmoF 11m is added to the treatment bath.
By using a solution, it is possible to carry out flow treatment of acidic tin plating paste with stable quality without causing adhesion of suspended particles during reflow pretreatment.

In addition, in the above example, the reflow pretreatment bath composition was set to 3.6.
g/Q ammonium chloride and 1.2 g/Q ammonia aqueous solution, but the composition is not limited to this, and depending on the Ijll of the tin plating bath, acid concentration, and water washing conditions after tin plating, ammonium chloride By changing the composition of ammonia and ammonia, it is possible to create a treatment bath with a pH value different from that in the above embodiments, and by changing the concentration, it can be stabilized and flow pretreatment can be performed. Furthermore, although the girder flow pretreatment bath was kept at room temperature in Example -1-, it may be heated or cooled if necessary.

〔Effect of the invention〕

As explained above, according to the present invention, ammonium chloride-ammonia buffer solution is used as a pretreatment bath for reflow tin plating, so no treatment chemical particles are left on the surface of the strip, and this makes it easier to use the equipment. Quality can be stabilized and flow treatment can be performed without the need for modification.

Agent Masao Oiwa

Claims (2)

[Claims] (1) A pretreatment method for the reflow tin plating method in which a tin-plated copper alloy strip is continuously heated and melted in an acidic bath, characterized by using an ammonium chloride-ammonia buffer solution as the reflow pretreatment bath. A pretreatment method for the flow tin plating method. (2) A pretreatment method for glue flow tin plating according to claim 1, characterized in that the temperature of the reflow pretreatment bath is room temperature.