JPH0365630B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention is applicable to Sn or
This invention relates to improvements in connectors made of phosphor bronze coated with a Sn alloy. <Prior Art> Recently, in order to simplify the assembly and repair of electric and electronic devices, circuits have been formed into blocks and these blocks have been combined and connected to each other. Connectors made of spring copper alloy plated with precious metals such as Au and Rh are used to connect these blocks to each other. However, these connectors use expensive precious metals, which increases costs, especially Au.
It is known that plated wires cause sulfide creep from the edges, causing contact failure. On the other hand, inexpensive Sn and Su alloys, such as solder, have stable connectivity over a long period of time and are highly reliable. (hereinafter wt% is abbreviated as %), a connector base material consisting of 3 to 8% Sn and the balance Cu plated with Sn or Sn alloy is widely used in consumer devices. <Problems to be Solved by the Invention> Connectors may become hot during use due to conductor resistance or contact resistance, and connectors made of phosphor bronze plated with Sn or Sn alloy may suffer from plating when exposed to high temperatures. The Sn of the layer and the base material
A diffusion reaction occurs with Cu, creating a P-enriched brittle alloy phase near the base material between the plating layer and the base metal, which has the disadvantage that the plating layer peels off during use, resulting in poor contact. . To prevent this, a method is known in which a Cu plating layer is interposed between the base material and the Sn or Sn alloy plating layer, but in order to effectively prevent this, it is necessary to form the Cu plating layer to a thickness of several μm or more. This is a factor that increases the manufacturing process and costs. In addition, attempts have been made to prevent the above diffusion by applying Ni plating instead of Cu plating, but hard Ni such as Ni plating may cause cracks during processing deformation or cause subtle changes in spring characteristics. There are harmful effects such as <Means for Solving the Problems> In view of this, the present invention has found, as a result of various studies, that the above enrichment of P can be reduced by limiting the P content of phosphor bronze, and as a result of further studies. , Cu
We have developed a connector that does not require base plating and exhibits stable contact resistance over a long period of time.
It is characterized in that Sn or a Sn alloy is directly coated on at least the contact portion of a connector base material consisting of 0.01 to 0.08% P, 3 to 8% Sn, and the balance Cu and inevitable impurities. <Function> In the present invention, the P content of the phosphor bronze, which is the connector base material, is limited to 0.01 to 0.08%.If the content is less than 0.01%, the strength and spring characteristics of the connector will be insufficient. Exceeding this will not only reduce the adhesion of Sn or Sn alloy plating, but also
The enrichment of P at high temperatures during use cannot be ignored,
This is because there is a risk that the Sn or Sn alloy plating layer will peel off during use, so it is desirable to use phosphor bronze with a P content of 0.03 to 0.08%. In addition, the Sn content was limited to 3-8% in order to obtain sufficient strength and spring properties as in the past. If the Sn content is less than 3%, the strength and spring properties will be insufficient, and if it exceeds 8%, the δ phase This is because the processability deteriorates significantly. Example 1 Phosphor bronze having the composition shown in Table 1 was melted and cast, the ingot was faced, annealed and rolled repeatedly, and the final processing rate was 60.
Finished in strips with a thickness of 0.45mm. After cathodic degreasing and pickling, this was plated with Sn to a thickness of 2 μm and molded to obtain the connector of the present invention. For comparison, phosphor bronze with a composition with a high P content shown in Table 1 was similarly finished into strips with a thickness of 0.45 mm, which were cathodically degreased and pickled, and some of the strips were coated with Cu before Sn plating. The base plating is applied,
This was molded to obtain a connector for comparison. Each plating condition is as follows. (1) Cathode degreasing JMF cleaner #160 60g / Bath temperature 60℃ Current density/processing time 2.5A/dm ² × 1〓 (2) Pickling (immersion) H ₂ SO ₄ 100g / H ₂ O ₂ 30g / Addition Agent 1vol% Bath temperature 20℃ (3) Sn plating H ₂ SO ₄ 100g/ SnSO ₄ 40g/ Additive Ishihara Pharmaceutical UTB 514H 10c.c./ No2 10c.c./ No3 0.5cc/ Formalin 2c.c./ Bath temperature 20℃ Current density 5A/dm ² (4) Cu plating H ₂ SO ₄ 60g/ CuSO ₄ 240g/ Additive Caparaside manufactured by Nippon Schering Co., Ltd.
MK 5c.c./ 〃 A 0.5cc/ NaCl 200mg/ Bath temperature 50℃ Current density 3.0A/dm ² Form an 8-core connector using the above connector, insert it into the Sn-plated terminal on a printed board, and conduct a deterioration test. (Holded at a temperature of 110°C in the air for 1000 hours without any load), the contact resistance and peeling of the Sn plating layer were observed. The results are also listed in Table 1.

【table】

[Table] As is clear from Table 1, the connector of the present invention is
It can be seen that the Sn plating layer does not peel off and stable characteristics are obtained, similar to the case with the thick Cu base plating. On the other hand, in comparison connector No. 6, which has a high P content and is not plated with Cu, the Sn plating layer peels off and the contact resistance increases significantly. Example 2 An 8-core connector similar to Example 1 was formed using connectors No. 1, 3, and 4 of the present invention and comparative connectors No. 6, 7, 9, and 10 in Table 1, and the Sn of the printed board was After inserting it into a plating terminal and carrying out a 1,000-hour current test at room temperature with a load of 5A of alternating current applied to each core, the contact resistance and peeling of the Sn plating layer were observed. The results are shown in Table 2.

[Table] As is clear from Table 2, the connector of the present invention did not peel off the Sn plating layer, and stable characteristics were obtained in the actual conduction test, similar to those with a thick Cu base plating. I understand. On the other hand, in comparative connector No. 6, which has a high P content and is not plated with Cu, the Sn plating layer peels off and the characteristics deteriorate significantly. Although tin plating was used in the above embodiments, the present invention is not limited to this, and it is clear that reflow tin plating or tin alloy plating such as solder can also exhibit similar effects. <Effects of the Invention> As described above, according to the present invention, even if Sn plating is directly applied without applying underlying Cu plating, stable contact resistance is exhibited over a long period of time, and the manufacturing process is simplified, making it possible to reduce costs. It has remarkable industrial effects.

Claims (1)

[Claims] 1. A connector characterized in that Sn or a Sn alloy is directly coated on at least the joint of a connector base material consisting of 0.01 to 0.08 wt% P, 3 to 8 wt% Sn, and the remainder Cu and inevitable impurities.