JPH048883B2 - - Google Patents

Description

[Detailed description of the invention]

In the present invention, Ag is applied to part or all of the surface of a Cu-based substrate.
Or, it relates to an electronic component material coated with an Ag alloy, and in particular provides an economical material that satisfies various properties required for component materials. In general, Ag or Ag alloys such as Ag-In, Ag-Pd, and Ag-Au have good conductivity and excellent solderability and corrosion resistance.
Substrates made of Cu alloys such as Cu-Be, Cu-Ti, and Cu-Fe, whose surfaces are partially or completely coated, are used as materials for electronic components. For example, contact parts such as switches and connectors, base materials or lead materials of semiconductors, integrated circuits, various parts, etc. are all made of Ag or
Since they are assembled by soldering or brazing using the properties of Ag alloys, and are themselves attached to printed circuit boards by soldering, solderability is an essential condition. Cu and Cu alloys form a strong oxide film even when stored at room temperature, and thick oxide scales are formed in high-temperature environments such as resin molding, curing, soldering, and aging for performance adjustment in the assembly process of electronic parts. It significantly impairs the adhesion. It is also known to use activated flux for soldering, but residual flux causes fatal corrosion damage, requires careful cleaning, and cannot be applied to electronic parts. It is also conceivable to assemble the parts in a reducing atmosphere with the atmosphere shut off, but this method is not practical in terms of equipment or economy. The reason why Ag-coated Cu-based materials are used for electronic components is to obtain good solderability in high-temperature environments.Another reason is that oxide films are difficult to form on the surface, and the electrical connectivity required at the time of contact is good. That's true. This effect of Ag is due to Au, Pd,
It can also be obtained from precious metals such as Pt, but both
It is 10 to 100 times more expensive than Ag,
It is industrially uneconomical and is usually coated with Ag or an Ag alloy to a thickness of 2 to 3 microns or more.
However, with the dramatic development of the electronics industry, there is a strong desire to save Ag as much as possible not only from an economic standpoint but also from the standpoint of resource conservation. However, when the coating thickness of Ag is reduced, the following defects occur. (1) Depending on the manufacturing method and conditions, the Ag layer becomes porous, creating so-called pinholes and exposing the base material. (2) Base metal components of the base material reach the surface and accumulate due to solid phase reaction. In particular, the progress of this reaction is related to an exponential function of temperature, and becomes more pronounced under high temperature conditions. Exactly the same problem occurs with products coated with expensive Au, and to prevent this, Ni is added between the substrate and the Au layer.
In order to substantially reduce the above-mentioned defects, an intermediate layer consisting of
Provide an intermediate layer with a thickness of 2 μ or more, or
Depending on the application, the material is coated with Ag with a thickness of 0.2 to several microns by plating or the like, and is used for contacts such as connectors. Even with Ag coating, there is an intermediate layer made of Ni between the substrate and the Ag layer.
Practical in semiconductor lead frames, various contacts, terminals, etc., with an intermediate layer usually 0.5 to 3μ thick to prevent pinhole corrosion and keep the Ag surface clean, as well as to prevent high-temperature diffusion of base metals from the base. It is prevented. However, in high-temperature environments, it has been reported that the solderability deteriorates and sometimes the Ag layer peels off. In view of this, the present inventors have conducted various studies and found that Au
It was discovered that this phenomenon is unique to Ag coatings and cannot occur at all with coatings. In other words, Ag from a temperature of around 180℃
Oxygen in the atmosphere easily permeates through the layer, and the permeating oxygen is particularly active, perhaps because it is atomic, and oxidizes the Ni under the Ag layer. Oxidation of Ni breaks the metallic bond at the interface between the Ag layer and the Ni layer, drastically reducing the adhesion. In addition, Ag dissolves quickly in the solder bath, and under practical conditions, it dissolves in a thickness of 2 mm per second.
Dissolution of ~3μ occurs. Therefore, during soldering, the thin Ag layer dissolves, leaving a hard NiO layer that does not wet the solder at all.
The surface is exposed and inhibits solderability. Also Ni
If no layer is provided, the substrate surface will be thickly oxidized and similar results will occur. Furthermore, in Ag-coated Cu-based materials with a Ni layer, when mechanically deformed, external force concentrates on the Ni layer, which is harder than Ag or Cu, and small cracks are generated that start from the Ni layer and reach the surface of the Ag layer. Easy to do. Electronic components are manufactured through precision machining, so if a minute crack occurs during bending or drawing, not only will this become an exposed part of the base and cause corrosion, but the crack will also expand due to the volume expansion of the corrosive material. This is a serious defect. Based on this knowledge, and as a result of various studies to solve this problem, the present invention has developed an economical silver-coated copper-based electronic component material that can satisfy the various properties required as a component material. In materials where at least a portion of the surface of the substrate is coated with Ag or Ag alloy, there is a thickness of 0.01 between the substrate and the Ag or Ag alloy layer.
It is characterized by providing an intermediate layer made of Ni, Co, or alloys thereof (excluding Ni-Zn alloys) with a thickness of ~0.1μ. That is, the present invention provides wires, rods,
The base is a strip, plate, etc., or a part or all of it is processed into a part shape, and a part or the whole of the surface is coated with Ni, Co, or an alloy thereof with a thickness of 0.01 to 0.1μ (however, Ni -Excluding Zn alloy) (hereinafter abbreviated as Ni, Co intermediate layer), and on top of that,
It is coated with Ag or Ag alloy layer (hereinafter abbreviated as Ag layer), and is used as a Ni, Co intermediate layer in addition to Ni and Co.
Ni-Co, Ni-P, Ni-B, Co-P, Co-Sn,
Using alloys other than Ni-Zn such as Ni-Sn and Ni-Fe,
In particular, its thickness is 0.01~0.1μ, preferably 0.02~
By setting the thickness to 0.08μ, various defects caused by the conventional Ni layer have been improved.In order for the conventional Ni layer to act as a diffusion barrier, it is said that it is necessary to increase the thickness by 1 to 2μ or more. On the other hand, in the present invention, by making the Ni, Co intermediate layer thinner, the object was achieved through a unique action that could be called a kind of filter. Conventional Ni layers do not diffuse with Ag and reactions with Cu are unlikely to occur under practical conditions, whereas the Ni, Co intermediate layer has a thickness of 0.01 to 0.1μ, so it does not diffuse with Ag and reacts with Cu. Some component elements such as Cu, Zn, Sn,
A small amount of In, Cd, etc. permeate and diffuse into the Ag layer, suppressing the permeation of atmospheric oxygen through the Ag layer and preventing surface oxidation of the Ni, Co intermediate layer.
Cu, Zn, Sn, In, Cd, etc. are all elements that form a solid solution in Ag and form an alloy, and have a strong affinity for oxygen. prevent it from reaching. But Ni,
If the thickness of the Co intermediate layer is less than 0.01μ, the above elements will pass through excessively, causing the same defects as when no conventional Ni layer is used. Similarly, the surface oxidation of the Ni and Co intermediate layer occurs due to its function as a barrier, which causes defects. Also Ni,
This thinning of the Co interlayer significantly improves processability and results in high quality parts.
That is, since it is thin, the concentration of external force during processing is reduced, making it less likely to break, and even if it does break, it will be so small that it will not reach the Ag layer. Ni is most effective as the Ni, Co intermediate layer. That is, Ni is the softest of the Ni and Co intermediate layers, has high diffusion permeability, and can be formed most efficiently during manufacturing. In addition, the base material is a Cu-Zn alloy,
So-called brass (Zn 20-40%) is the most effective. That is, this alloy is the cheapest and has excellent electrical and mechanical properties, and Zn has a lower melting point and higher diffusion rate than Cu, is more easily dissolved in Ag, and has a significantly greater affinity for oxygen. Furthermore, the Ag layer conventionally requires a thickness of 2 to 3μ or more, but according to the present invention,
A thickness of about 0.2 to 2μ is sufficient, and the thickness of the Ag layer is
If it is less than 0.2 μm, the quality will be insufficient even in the present invention, and if it is thicker than 2 μm, no increase in effectiveness can be expected and it is uneconomical. The material of the present invention has the above structure and can be produced by any method such as mechanical cladding, vapor deposition, sputtering, etc., but electroplating is the most practical method. That is, Ni, CCo, Ag, etc. belong to the class of metals that are most easily plated, and can be easily coated on desired positions, and can be coated continuously. Ni
The current efficiency of or Co is almost 100%, and by controlling the amount of current according to Faraday's law, it is possible to precisely plate the desired thickness. Ni, Co
Alloy plating is also possible by using a sulfate bath, a sulfamic acid bath, a borofluoride bath, etc., and adding alloy components as necessary. For Ag plating, cyanide bath, thiocyanide bath, pyrophosphoric acid bath, iodide bath, etc. are used, and alloy plating is also possible. The present invention will be described in detail below with reference to examples. Example (1) A brass plate (35% Zn) with a thickness of 0.42 mm was degreased and pickled using the usual method, and then Ni plating and Ag plating were performed using the plating bath shown below to the thickness shown in Table 1. Manufactured lead frame materials for diodes. Ni plating Ni (SO ₃ NH ₂ ) ₂ 500g / NiCl 30g / H ₃ BO ₃ 30g / PH 2.5 Bath temperature 50℃ Current density 2.5A/dm ² Ag strike plating AgCN 3g / KCN 30g / Bath temperature 20℃ Current density 3A/dm ² Agmetsuki AgCN 30g/ KCN 40g/ K ₂ CO ₃ 20g/ Bath temperature 20℃ Current density 1.5A/dm ² Lead frame material for diodes is usually punched into strips (width 5.0mm, length 0.5mm) , bend it at a right angle (R = 0.5 mm), and solder a Si chip to one end (95
%Pb-5%Sn, temperature 320℃, 1 minute), then sealed with resin and cured (temperature 180℃, 5 hours in air)
and then soldered to a printed circuit board. In this soldering, the wetted area is 90% when dipped for 5 seconds in a eutectic solder bath at a temperature of 235℃.
The above is required. To ensure that the above frame material does not deteriorate due to storage and bending, it is heated at a temperature of 100℃ for 24 hours, and then heated in a solder bath (95%Pb-5%Sn, temperature 320℃).
Measure the wetted area by dipping one end for 5 seconds in a eutectic solder bath at 235°C for 5 seconds, then heating it in air at 180°C for 5 hours, then dipping the other end in a eutectic solder bath at 235°C for 5 seconds was measured. These results are also listed in Table 1.

[Table] As is clear from Table 1, both solderability is excellent when the Ag thickness is 1.2μ and the Ni thickness is 0.02 to 0.10μ. On the other hand, the eutectic solderability after heating in the atmosphere is significantly reduced in the case where Ni is applied too thickly, and the case where Ni is not used has an Ag thickness of 2.5 μm.
However, it is insufficient and requires 4.0μ or more, and it can be seen that even an Ag thickness of 4.0μ is insufficient for a Ni thickness of 1.0μ. Next, after bending the above frame material, the end faces were sealed with a lacquer and a 5% salt spray test was conducted for 24 hours based on JIS-Z-2371 to investigate the occurrence of blue copper corrosive substances in the bent parts. . As a result, no abnormalities were observed in the inventive member, but in comparison material No.
In No. 7 to 9, the occurrence of blue copper corrosion was observed in the bent part, and in No. 9, it was particularly noticeable compared to the comparative material that did not use Ni.
In No. 1, patina appeared on the entire surface. Example (2) In Example (1), the following plating baths were used instead of Ni plating of the invention material No. 4, and Ni-7 and Ni-7 were used, respectively.
%P alloy and Ni-10%Co alloy were plated and lead frame materials for diodes were produced in the same manner. Ni-7% alloy plating NiSO ₄ 200g / NiCl 15g / H ₃ PO ₃ 25g / H ₃ BO ₃ 30g / Bath temperature 35℃ Current density 3.0A/dm ² Ni-10% Co alloy plating NiSO ₄ 240g / CoSO ₄ 15g / NiCl ₂ 30g / H ₃ BO ₃ 30g / Bath temperature 45°C Current density 4A/dm ² The same tests as in Example (1) were conducted on these. As a result, for the plated with Ni-7%P alloy, the wetted area was 97% in the 95%Pb-5%Sn bath, 98% in the eutectic solder bath, and 98% in the case of the plated with Ni-10%Co alloy. They were 93% and 97%. Also 5
% salt water spray test, no abnormalities were observed. Example (3) In Example (1), copper and copper alloys shown in Table 2 were used instead of brass, which is the base of the invention material No. 4,
A lead frame material for a diode was produced in the same manner. The same tests as in Example (1) were conducted on these and the wetted areas were measured. The results are also listed in Table 2.

[Table] As is clear from Table 2, both types have excellent solderability, especially nickel silver containing Zn (Cu-
It can be seen that the 23% Zn-12% Ni alloy) is the most excellent. Example (4) Using a phosphor bronze strip with a thickness of 0.25 mm, degrease and pickle it in the usual manner, and then perform Ni plating or Co plating with the thickness shown in Table 3 using the plating method shown below.
Thereon, Ag plating with a thickness of 1.2 μm was performed in the same manner as in Example (1) to produce a contact material for a connector. Ni-plated NiSO ₄ 250g / NiCl ₂ 25g / H ₃ BO ₃ 30g / P H 2.5 Bath temperature 45℃ Current density 1.5A/dm ² Co-plated CoSO ₄ 450g / NaCl 30g / H ₃ BO ₃ 45g / Bath temperature 50℃ Current Density: 1.0A/dm ² The contact material for the connector is usually press-molded and the end is soldered to the electric wire to connect it, and the contact part weighs approximately 100g.
It is attached to a pin of a circuit on a printed circuit board under a load of 100 Ω, and the condition is that the contact resistance does not exceed 10 mΩ over long-term use. Like normal contacts, the contact part is protruded into a convex shape to stabilize contact with the other party. In order to ensure that the contact material does not deteriorate during storage and molding processing, it is kept under constant temperature and humidified conditions at a temperature of 60℃ and humidity of 95% for 1000 hours, and then immersed in a eutectic solder bath at a temperature of 235℃ for 5 seconds to wet the solder. I looked into gender. After being kept under constant temperature and humid conditions for 1000 hours, heated to 250℃ for 10 minutes, and then kept in the air at 120℃ for 2000 hours, a hemispherical Ag rod with a tip radius of 4.0mm was loaded with 100g. Press with, current 100mA
The contact resistance was measured. Furthermore, a connector was molded and subjected to the same treatment, and an Ag-plated pin material (0.62 mm square) was inserted into it and the contact resistance was measured in the same manner. These results are also listed in Table 3.

[Table] As is clear from Table 3, the materials of the present invention exhibit good properties in both solderability and contact resistance. On the other hand, with the comparative material with an excessively thick Ni layer, no deterioration in solderability was observed because there was no heat treatment, but the contact resistance increased significantly, and the comparative material with no Ni layer It can be seen that the layer thickness needs to be 4.5μ or more. Example (5) Using a phosphor bronze strip having a thickness of 0.06 mm, Ni plating and Ag plating were performed in the same manner as in Example (1) to produce disc spring materials for keyboard switches shown in Table 4. The surface hardness of the phosphor bronze strip is set to MHV (200g) 210 because the disc spring material emphasizes reliable electrical connection as well as subtle fingertip sensation (click feeling) when operating keys.
~230 managed. This disc spring material was kept under constant temperature and humidified conditions of 60℃ and 95% humidity for 1000 hours, and
For those kept at a temperature of 150℃ for 1000 hours,
Contact resistance was measured in the same manner as in Example (4). Also, a keyboard switch was assembled by molding a disc spring with a diameter of 8 mm from this material, and the click feeling was tested. These results are also listed in Table 4.

[Table] As is clear from Table 4, all of the materials of the present invention exhibit good contact resistance and click feeling, while Ni
In the comparison material with an excessive number of layers, no deterioration in contact resistance was observed because the heat treatment was performed at a relatively low temperature, but the springiness slightly changed and the click feeling became poor. Also
It can be seen that in the case where the Ni layer is not used, although the click feeling is good, the contact resistance is significantly deteriorated. As described above, according to the present invention, by making the intermediate layer made of Ni, Co or an alloy thereof thinner, contrary to conventional wisdom, a combination of Cu and Cu alloy as the base and Ag and Ag alloy as the coating layer can be achieved. It was able to exhibit a unique and useful action and significantly improve its performance. In particular, it can withstand high temperatures and greatly improves workability, making it suitable as a material for electronic parts that require precision and a variety of functions, and being economically superior, resulting in remarkable industrial effects.

Claims (1)

[Claims] 1. In a material in which at least a part of the surface of a Cu-based substrate is coated with Ag or Ag alloy, there is a layer of Ni, Co or its alloy (Ni, Co or its alloy) with a thickness of 0.01 to 0.1μ between the substrate and the Ag or Ag alloy layer. A silver-coated copper-based electronic component material characterized by having an intermediate layer made of (excluding Ni-Zn alloy). 2. The silver-coated copper-based electronic component material according to claim 1, wherein the intermediate layer made of Ni, Co or an alloy thereof (excluding Ni-Zn alloy) has a thickness of 0.02 to 0.08μ. 3. The silver-coated copper-based electronic component material according to claim 1 or 2, wherein the coating thickness of Ag or Ag alloy is 0.02 to 2μ. 4. A silver-coated copper-based electronic component material according to claim 1, 2, or 3, in which the surface of the Cu-based substrate is made of a Cu-Zn alloy.