JPS585276B2 - Electrical contact surface treatment method for copper-coated aluminum busbar - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for plating the electrical connection surface of a copper-coated aluminum busbar, which is constructed by using aluminum as a base and coating the periphery with copper.

Copper-coated aluminum busbar (hereinafter abbreviated as copper-coated aluminum busbar).

) is 1. The use of copper, which is unstable in terms of resources, supply, price, etc., is extremely reduced, and a large amount of aluminum, which is excellent in terms of resource abundance and low cost, is used in large quantities, and the production of copper and aluminum is compensated and shortened. It is a composite material developed as a material.

However, even though the busbar has such features, when connecting the busbars to each other or connecting them to terminals, etc., to obtain the necessary electrical connection surface, the end surface cut along the surface and the connection bolt through hole are required. However, there was a problem with the plating process in the surface treatment.

Figures 1 and 2 show the end of a copper-coated aluminum busbar, in which a cut end face 1 and a hole 2 for connecting bolts are formed. A composite cross section of the base surface 3A and the copper coating layer 3B is exposed.

Conventionally, Ni and Sn are particularly practical plating methods for copper-covered aluminum busbars that expose the aluminum surface 3A.
, it was attempted to cover it with Ag plating metal, and as experience was gained, the following methods were used.

That is, first, the exposed aluminum surface is masked, and Ni and Sn are applied only to the copper on the steel surface.

A suitable type of Ag plating is applied, and if necessary, the masking of the aluminum surface is removed.

If you want to completely plate the exposed aluminum surface,
Next, the steel parts on the surface are masked, and the aluminum base is surface-treated by selecting an appropriate plating method among the plating methods applied only to aluminum alone, and then the masking of the steel parts is removed.

(The opposite method is also available.) However, with this method, the plating applied to the steel part and the plating applied to the aluminum part are separate processes, which has the major disadvantage of complicating the process and high processing cost. simplification was desired.

Conventionally, such simplified plating processes have been considered.

For example, when plating aluminum, it has been proposed to use the zinc substitution method, but this has the disadvantage of discoloring the copper and making it difficult for the plating to adhere to the steel parts. I was thinking of applying this plating to the entire steel and aluminum parts, but (1) the aluminum would be seriously damaged by the plating solution;
2) Aluminum has a negative effect on plated plates, and (3) The plating on aluminum peels off.The idea and customs were taken too seriously, and the application was not given any value.

The present invention places importance on that last idea, and as a result of much research and development, it has been developed to create an electrically conductive copper-covered aluminum busbar with high practical value that does not require separate processes such as conventional plating and masking. A contact surface treatment method was obtained.

That is, in the method of the present invention, Ni, Sn, A, etc.
When applying any type of electroplating in g, the cut section and perforation section are left as they are, and the entire surface of the rough connection part is electroplated only on copper at a low pH.
It is characterized by being subjected to short-time degreasing and acid treatment.

In the above method, Ni, Sn, and Ag plating is degreased by washing with an alkaline solvent such as trichlene during the plating process, but degreasing at particularly high pH and for a long time will cause the aluminum to dissolve, which will destroy the aluminum substrate and remove the plating solution. affect.

However, if the pH for 1 hour is set to an appropriate value, the aluminum will not be degraded that much and the plating solution will not be affected much.

In addition, the copper strike treatment that has been carried out together with such degreasing treatment is carried out in an alkaline environment like the aforementioned degreasing treatment.
Moreover, even if this treatment was excluded, there was almost no problem with the actual plating.

The method of implementing the present invention into a copper-covered aluminum busbar, which was made against this background, is summarized as follows.

(1) After degreasing and pickling (e.g. 5% sulfuric acid aqueous solution) the plated part of the copper-coated busbar with a low pH short-time solvent (e.g. trichloride) and pickling (e.g. 5% sulfuric acid aqueous solution), the plated part of the copper-coated busbar is degreased using a nickel sulfate or nickel chloride aqueous solution. To be electroplated.

(2) Sn plating The part to be plated of the copper-coated aluminum busbar is degreased and pickled for a short time at low pH, and then electroplated using an aqueous solution of tin sulfate or an aqueous solution of sodium stannate.

(3) Ag plating After short-time degreasing and pickling at low pH, electroplating is performed using an aqueous solution of silver cyanide or acid silver.

The results of confirming the effects of the method of the present invention using actual examples will be explained below.

(1) Ni plating (a) 200g/l of NiSO4.7H2O.

Using an aqueous solution (pH: 6.0) containing 20 g/l of NH4Cl and 15 g/l of H2BO3, at a liquid temperature of 20°C and a current density of 1 A/dm2, a terminal having a cut cross section and a perforated cross section of a copper-covered aluminum busbar was prepared. Ni was electroplated for 3 minutes.

Figure 3 shows the situation, and the cut section 1 before plating.
, after plating, the perforated cross section 2 has an aluminum base 3A and a steel part 3B.
Both were coated with Ni4 approximately 2μ thick.

The plated member 4 was heated at 150°C for 10 minutes to confirm its performance.
Although it was heated for a long time, it did not swell and fall off, and it also passed the salt spray test based on JIS Z 2371 (5% NaC
The Ni plating layer showed a sufficient anticorrosion effect on both Cu and Al without generating black rust when spraying with an aqueous solution (temperature: 35° C., humidity: 96%) for one week.

(b) 330g/l of NiSO4.7H2O, NiCl
Using a pH 3.0 aqueous solution containing 45 g/l of 2.6H2 and 30 g/l of H3BO3, the liquid temperature was 50°C and the current density was 6 A.
As a result of electroplating Ni (approximately 3μ coating) at /dm2 for 1 minute in the same manner as in (a), both the Al and Cu portions were coated, and the same performance as above was exhibited.

(2) Sn plating (a) 60g/l SnSO4, 90g/l H2SO
Using an aqueous solution containing 4,0,7 g/l of gelatin and 100 g/l of cresol sulfonate, Sn was electroplated (approximately 4 μ) at a temperature of 35° C. and a current density of 4 A/dm 2 for 3 minutes.

As a result, the same plating condition performance as (1) was obtained.

(b) 80g/l Na25nO3.33H2O112
/1 Electroplating of Sn using an aqueous solution containing NaOH at a temperature of 70°C and a current density of 2A/dm2 for 3 minutes (approximately 2μ coating)
did.

The result is the same as (a). (3) Ag plating (a) 60g/l AgCN, 70g/l NaCN,
25g/l Na2CO3, 25g/l free NaCN
Using an aqueous solution containing
Electroplating Ag at dm2 (approximately 3μ/3 minutes) (b) 200g/l AgNO3・33H2O16
Electroplating Ag using an aqueous solution containing 0/1HNO3 at a temperature of 40℃ and a current density of 2A/dm2 (approximately 2μ/1 minute) * (A) and (B) are the same as described in (A) for Ni plating. It was coated with Ag and showed sufficient performance.

As is clear from the above examples, the treatment method of the present invention is as follows:
Ni, Sn, and Ag plating are basically the same as the plating methods for each metal on copper, but because these were originally developed for copper, and in the past, this type of copper plating was Aluminum bus bars do not universally exist, so Al, Cu
Since there was no need for simultaneous plating under the coexistence, the state of plating for Al was not tested.

However, the present inventors discovered that Al containing Cu as a main component,
Faced with the need for simultaneous Cu plating, we tried applying these conventional plating methods, and as mentioned above, we confirmed that Cu was hot and that the A1 area was also covered with a plating layer and had the required performance. That's what I came to do.

This is presumed to be due to the fact that the plating solution removed the oxide film on the surface of Al and had the effect of cleaning and activating it appropriately.

As explained above, according to the method of the present invention, the plating process for the electrical connection surface of the copper-coated aluminum busbar, which has a cut cross section and a perforated cross section in which the bare aluminum surface is exposed with the copper, can be easily performed in a single process. Moreover, the plating on the aluminum part can be physically firmly adhered without peeling, etc., and is extremely effective in expanding the application of this type of copper-covered aluminum bus bar.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the end of the copper-coated aluminum bus bar where the electrical contact surface is set, Fig. 2 is a longitudinal sectional view of one end of the same bus bar, and Fig. 3 is a longitudinal sectional view of one end of the same bus bar after plating treatment. shows.

Claims (1)

[Claims] 1. A cut cross section of a copper-coated aluminum busbar. Ni and Sn are applied to the electrical connection surface including the perforated cross section. When electroplating any type of Ag, the aluminum bare surface exposed on the cut cross section and perforation cross section is left as is, and the electroplating only on copper is applied to the entire surface of the connecting phase at a low pH for a short period of time. A method for treating an electrical contact surface of a copper-coated aluminum busbar, characterized by performing degreasing and pickling treatment.