JPS6123788A - Method for plating stainless steel with noble metal - Google Patents

Abstract

PURPOSE:To plate stainless steel with a noble metal maintaining high quality for a long period by carrying out electrolysis using the steel as a cathode in an aqueous soln. contg. Ni and free hydrochloric acid each at a specified concn., electroplating the steel with Ni to a specified thickness in a weakly acidic bath, and plating the pretreated steel. CONSTITUTION:Electrolysis is carried out using a stainless steel material to be plated as a cathode and stainless steel or an Fe-1-50% Ni alloy as an anode in an aqueous soln. contg. >=0.1g/l Ni and >=30g/l free hydrochloric acid at about 1- 100A/dm<2> current density for about 1-180sec. The steel material is washed and electroplated with Ni or an Ni alloy to 0.05-0.5mum thickness in a weakly acidic plating bath such as an NiSO4 bath of about 2-4pH. The pretreated steel material is plated with a noble metal. Noble metallic plating of high quality suitable for a precision machine or an electronic machine can be formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of plating stainless steel (hereinafter abbreviated as SUS) with a precious metal, and in particular, to a method for plating high quality precious metal suitable for use in precision equipment and electronic equipment. belongs to. [Prior art] In general, SUS includes austenitic, ferrite, martenzite, and precipitation hardening types, which have excellent mechanical strength and other physical properties, and have a hard surface. Because it forms a passivation film and has excellent corrosion resistance, it is used for various purposes.However, the formation of a passivation film only hinders the bonding properties of soldering, etc. In order to make electrical connections difficult, dissimilar metals, especially A11.Ag, P
It is plated with noble metals such as t, Pd, and Ir. These precious metals have excellent corrosion resistance, are suitable for soldering and electrical connections, and are widely used in electrical contacts, semiconductors, and the like.

The formation of a passivation film is a major hindrance in plating operations, and in order to obtain stable adhesion plating, it is necessary to remove the passivation film and activate the surface. Ni strike plating is known as a method suitable for this purpose, and noble metal plating is usually performed after Ni strike plating. Ni strike plating means, for example, Ni
012 240g/12, HCI 80~120sh/bu aqueous solution, SUS grain to be plated 20A/12
Cathode treatment is performed for 2 to 4 minutes at a current density of dn+2, the passivation film is electrolytically reduced, and Ni is plated to a thickness of 0.4 to 1μ at f''iJ to protect the 808 surface. .

(Problems to be solved by the invention) SU plated with negative metal after Ni strike plating
When S is used in precision equipment or electronic equipment, the following problems arise. In other words, in order to be used as spring contacts in switches, connectors, etc., they have small and complex shapes, and the contact part is housed within the structure, so it is possible to press-form them as contact parts and then plate them. It is often rotational. In addition, from the viewpoint of productivity, pre-plated SUS
It is desired to mold the material. However, the molding process of contact parts often involves bending, overhanging, drawing, etc., and these processes tend to cause minute racks.
This causes a decrease in mechanical strength and deterioration of electrical contact resistance over time. This is because a large amount of Hz is generated in Ni strike plating, so excessive N2 is included in the N1 plating layer, making the Ni plating layer brittle, and causing -UN during molding.
Clutter is generated in the i-plated layer. This is because these cracks rise to the noble metal plating layer and further advance into the SUS substrate.

In order to prevent this, attempts have been made to activate the SUS material to be plated by cathodic electrolytic treatment in an aqueous solution of -HCf or N2804 and then plate it. Because of the re-passivation, the reliability of the Ni strike plating is poor.

Furthermore, a method of directly plating Au after activation by cathodic electrolytic treatment in an aqueous N2SO4 solution or N2SO4 aqueous solution has also been attempted. This method can be used, for example, in an Au C,e3 aqueous solution containing l-I CJ following activation.
□A to desired thickness after applying AL + strike plating
It is U-plated. Furthermore, attempts are being made to utilize the acidic electrolytic activity of special compositions.

These methods greatly reduce the occurrence of cracks compared to the above-mentioned Ni strike plating; There is a drawback that the AL+ plating layer peels off from the edges of the molded parts.

[Means for solving problems]

In view of this, as a result of various studies, the present invention has developed a precious metal plating method for SUS that eliminates the deficiencies of the conventional methods and can perform high quality precious metal plating suitable for use in precision equipment and electronic equipment. , SUS precious metal plating odor (NiO, 1g/J on the SUS plate to be plated)
! As mentioned above, c′ in an aqueous solution containing 30 g/J or more of free hydrochloric acid,
The anode was subjected to cathode electrolytic treatment using SUS or Fe-1~50%Ni alloy, and then a weakly acidic bath was used to
．． This method is characterized in that N1 or N1 alloy is electroplated to a thickness of 0.05 to 0.5 μm, and noble metal plating is performed on top of the electroplating.

That is, the present invention, prior to precious metal plating,
The next process is tMit. Note that before this treatment, degreasing and descaling treatments are performed as necessary.

In the first treatment, C is a plating SUS material with Ni 0.
Cathode electrolytic treatment using SUS or Fe-1~50%Ni alloy for the anode in an aqueous solution containing 1g/l or more and free hydrochloric acid 30g/l or more, cathode current density 1~100Δ/6m2, treatment. Time 1~180se
Adjust within the range of c in relation to the liquid composition. As the second treatment, the SUS material to be plated that has been subjected to the first treatment is washed with water, and then coated in a weakly acidic plating bath to a thickness of 0.05~
0.5 μ of N1 or Ni alloys, e.g. Ni-Go (
-C.

-5 to 20%), Ni-Zn, Ni-Fe,
Plate N1 to P (P=1 to 5%), etc. As these weakly acidic plating baths, baths with a pH of 2 to 4, such as a NiSO4 bath, a sulfamic acid bath, and a poufutate bath, are used.

[For production]

Through the first treatment, the surface of the SUS material to be plated is activated, and at the same time a trace amount of metal containing Ni is precipitated, protecting the surface of the SUS material to such an extent that it is difficult to passivate again. However, ゛C free hydrochloric acid is 309/f! If it is less than that, not only will sufficient activation not be obtained, but excessive Ni precipitation will occur.
This is inconvenient in practice, and if the Ni content is less than 0.1 g/e, the prevention of re-passivation will be insufficient, and stable adhesion of the Ni-plated thighs will not be achieved.
Spelled as e or more, N i5g/, e or more. In addition, in this process, the C anode is made of SUS or l:e-1~50%N1.
When using an alloy, 1= is to prevent the generation of highly poisonous C (7 gas). If an insoluble anode such as 1 carbon or PT is used, Cfz gas will be generated, but SUS or Fe-1~50%
Ni alloy is soluble and does not generate C(2) gas.In addition, not only can Ni be replenished, but F, which is eluted at the same time, can be replenished.
e and Cr have unexpected effects. That is, HC (and Ni
Depending on the Ni concentration and current density time, a single bath composition with C and ez can produce hard Ni, similar to conventional Ni strike plating.
For example, when the Ni concentration is 20g/, the layer is thickly precipitated.
According to Osin spectroscopic analysis, N1 is 10-60% and 300-3000 in SUS and N1-Fe alloy solution
A human Ni-rich layer is formed. Although the reason for this is not clear, it is thought that excessive precipitation of Ni is suppressed by the precipitation of the Ni-Fe alloy.

The Ni-rich layer also prevents re-passivation and
This process enables Ni or N1 alloy plating with excellent C adhesion.

The second treatment is to plate Ni or Ni alloy that does not cause cracks by press molding, etc., and to prevent the plated precious metal from peeling off during long-term use. The Ni or Ni alloy plating layer in the treatment has a hardness of +-IV) 200~
300, and the hardness of conventional Ni strike plating with a large amount of hydrogen inclusion.
! ″″′″′1″″′1) Furthermore, when using the conventional precious metal plated products for a long period of time, the precious metal layer peels off.This is considered to be a kind of electrolytic corrosion effect.In contrast, this The intermediate layer made of Ni or N1 alloy in the present invention is located between the large potential difference between the active SUS and the 1IIK layer, and is thought to greatly suppress the electrolytic corrosion reaction at the interface. The thickness of the Ni or Ni alloy layer should be Okawakami 0.05μ or more. On the other hand, if it exceeds 0.5μ, it will promote the occurrence of cracks, so it is preferably 0.05μ or more.
07 to 0.25μ.

In this way, the present invention performs two stages of pretreatment prior to precious metal plating, thereby activating and temporarily protecting the 808 surface, then plating with soft N1 or Ni alloy, and then plating the 808 surface with a soft N1 or Ni alloy. By plating with precious metals,
It can withstand complicated molding processes using a press, maintains high quality even during long-term use, and eliminates the disadvantages of conventional noble metal plating on SUS.

〔Example〕

Using 5US301 with a thickness of 0.12 mm, it was degreased with acetone, subjected to various treatments shown in Table 1, and then plated with a noble metal of 1.0 μm in thickness. These were tested for workability and long-term adhesion. The results are shown in Table 2.

For workability, a press mold was used to form a circular shape with a diameter of 8# and a height of o.
, 3mm and o, 6mm.

Next, some of these were subjected to salt spray test LJISZ2371.
) was carried out for 4 intercostal intervals, and the presence or absence of red rust in the processed area was visually inspected. The other part was kept in a humidifying chamber at a temperature of 80°C and a humidity of 95% for 1000 hours, and then
A load of g'c is pressed onto the AU plate, and a current of 100 m and A
(Direct current) was applied to measure the contact resistance.

Adhesion was also determined by using a cutter knife to make cuts at 1 mm intervals from the surface to the SUS substrate, and then using a pressure cutter to cut the substrate at a temperature of 120°C and a humidity of 90%.
JISD02 before and after holding for 2000 hours.
According to the 02 method, a peel test with cellophane tape was carried out,
The peeling status of the plated portion was visually inspected.

Bath A (sulfamic acid bath) Ni (80ヰNH2)2 5007/
lN1Ca2 25g, QH
380330'j/12 PH3,0 Bath temperature 55℃ Current density 5A/dII
12B bath (Ni -10% CO bath) Ni 804 250! ? /
lNi CJ! z 30
'J/ICo 804 2
0J/J2H3BO330'j/l PH2,9 Bath temperature: 35℃ Current density 3A/dn+
2C bath (Ni SO ÷ bath) Ni 804 250g/l
Ni CJ! z 30s
? /J2H3BO330S1/l PH3,2 Bath temperature 50℃ Current density 2,5A/dIl
12 The following plating bath was used for plating Au, Ao, and Pd.

Au plating bath N-40 bath (manufactured by Nippon Engelhard) Bath temperature
55℃ Current density 0.25 A/dm
2A (l plating bath A () CN 6o9/
, eKCN 60g/
iK2 CO325SJ/l Bath temperature 30℃ Current density 2A/dm2
-P (l plating bath PNP-80 bath (manufactured by Nichika Sei Co., Ltd.) bath temperature
25℃ Single current melon 0.5A/d
m2 Table 2 As is clear from Tables 1 and 2, the conventional method No. 13'C- using N1 strike plating is inferior in processing f1, so J and reflux occur during press processing, resulting in salt water generation. In contrast, inventive methods No. 1 to 7 have good workability, no salt water rusting, low contact resistance, and the precious metal layer remains intact even after long-term use. It can be seen that no peeling was observed.

On the other hand, comparative method No. 1 performs Ni plating after activation.
8. Comparative method No. 9, in which the Ni content in the cathode treatment is less than 0.1 g/f, and Comparative method Nα11, in which the Ni plating thickness after the cathode treatment is less than 0.05 μ,
Comparative method No. 10, in which the content of free m hydrochloric acid in cathode treatment was less than 30 Sil/f, and cathode treatment L!, caused peeling of the noble metal layer during long-term use. l! 19
Comparative method N012 where the thickness of N1 plating exceeds 0.5μ
It is clear that the workability is poor.

[Effects of the Invention] As described above, according to the present invention, a noble metal plated SUS material with excellent workability and good adhesion can be manufactured.
It is used in precision equipment, electronic equipment, etc., and has significant industrial effects, such as solving problems in quality and performance that were previously considered problems.

Claims (1)

[Claims] When plating stainless steel with precious metals, the stainless steel material to be plated must contain 0.1 g/l or more of Ni and 30 g/l of free hydrochloric acid.
In an aqueous solution containing more than g/l, cathode electrolysis treatment is performed using stainless steel or Fe-1~50%Ni alloy for the anode, and then 0.05~0.5μ using a weak acid bath.
A method for plating stainless steel with a precious metal, which comprises electroplating Ni or a Ni alloy to a thickness of 100 ml, and plating the precious metal on top of the electroplating.