JPH0373962B2 - - 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. Generally Ag or Ag alloys, e.g. Ag-In, Ag-
Alloys such as Pd and Ag-Au are corrosion-resistant, good conductors, and have excellent solderability and electrical connection.
or Cu alloys, such as Cu-Zn, Cu-Sn, Cu-
Substrates made of alloys such as Be, Cu-Ti, Cu-Fe, etc., whose surfaces are partially or completely coated, are used as materials for electronic components. Electronic components such as switches, contacts such as connectors, substrates such as semiconductors and integrated circuits, and lead materials are all assembled by soldering or brazing, and are themselves attached to printed circuits etc. by soldering. Solderability has become an essential condition for electronic component materials. 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. Cu and
It is known that activated flux can be used to solder Cu alloys, but residual flux causes fatal corrosion damage, requires careful cleaning, and cannot be applied to electronic components. 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 as electronic component materials is to take advantage of the characteristics of Ag or Ag alloys and obtain good solderability in high-temperature environments.Another reason is to avoid the formation of an oxide film on the surface. However, the electrical connectivity required for contacts etc. is good. This effect of Ag can also be obtained with noble metals such as Au and Pt, but these
It is industrially uneconomical because it is twice as expensive or more expensive, and it is usually coated with Ag or an Ag alloy to a thickness of 2 to 3 μm or more. With the recent rapid development of electronic devices, it is desired to save Ag not only from an economic standpoint but also from the standpoint of resource conservation. However, when the Ag coating thickness is reduced, the following defects occur. (1) Depending on the manufacturing method and conditions, the Ag layer becomes porous, and the base material Cu or Cu alloy is exposed through so-called pinholes. (2) Base metal components of the base material reach the surface and accumulate due to solid phase reaction, degrading the above-mentioned properties of Ag. 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.
Products with an intermediate layer have been put into practical use, and in order to substantially reduce the above-mentioned defects, the intermediate layer is usually provided with a thickness of 1 to 2 μm or more, and on top of that, a layer with a thickness of 0.2 μm is applied depending on the application. A material coated with ~several microns of Au by plating or the like is used for contacts, etc. Ag-coated products with a Ni intermediate layer between the substrate and the Ag layer have been put into practical use in semiconductor lead frames, various contacts, terminals, etc., and are usually 0.5 to 3μ thick with a Ni intermediate layer and pinholes. This not only prevents corrosion and keeps the Ag surface clean, but also prevents high-temperature diffusion of base metals from the base. However, it has been reported that solderability deteriorates in high-temperature environments, and in some cases, the Ag layer peels off. In view of this, the present inventors conducted various studies and found that this phenomenon is unique to Ag coatings and cannot occur at all with Au coatings. In other words, from a temperature of around 180°C, atmospheric oxygen easily permeates through the Ag layer, and perhaps because the permeating oxygen is atomic, it is particularly active and oxidizes the Ni surface under the Ag layer, causing the interface between the Ag and Ni layers to oxidize. It breaks the metal bonds and drastically reduces the adhesion. Moreover, the Ag layer dissolves rapidly in the solder bath, and under practical conditions, a thickness of 2 to 3 μm is dissolved in one second. Therefore, during soldering, the thin Ag layer dissolves, exposing a hard Ni oxide surface that is completely unwettable with solder, which significantly impairs solderability. Furthermore, in the case where a Ni intermediate layer is provided, during mechanical deformation, external force concentrates on the Ni layer, which is harder than Ag or Cu, and minute cracks are likely to occur starting from the Ni layer and reaching the surface of the Ag layer. Since electronic device parts are manufactured through precision machining, minute cracks may occur during bending and drawing processes.
This not only becomes an exposed part of the substrate and causes corrosion, but also the crack expands due to the volumetric expansion of the corroding material, resulting in a serious defect. The present invention is based on such knowledge, and as a result of various studies to solve this problem, we have developed an economical Ag-coated Cu-based electronic component material that can satisfy the various properties required as a component material. In materials where at least part 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 Pd or Ru with a thickness of ~0.25μ. That is, the present invention provides wires, rods, and wires made of Cu or Cu alloy.
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 covered with an intermediate layer (hereinafter referred to as Pd , Ru intermediate layer) is formed, and an Ag or Ag alloy layer (hereinafter abbreviated as Ag layer) is formed thereon. Pd or Ru is difficult to undergo a diffusion reaction with the Cu-based substrate and has excellent oxidation resistance, and effectively prevents the defects (1) and (2) described above due to Ag or Ag alloy coating. Since Au, which is also a noble metal, easily reacts with the substrate and the Ag layer, the above-mentioned diffusion prevention effect cannot be expected. Also, Pt and Ir
Like Pd and Ru, it has oxidation resistance and is effective in preventing diffusion, but it is 10 to 100 times more expensive than Pd and Ru, and it is difficult to practically form a thin intermediate layer by electroplating etc. It's impractical. In comparison, Pd or Ru is about 5 to 10 times as expensive as Ag, making it the cheapest precious metal after Ag.
This is practical in combination with the fact that the thickness of the Ag layer as an intermediate layer can be reduced by 1μ or more. However, it is desirable to form the Pd and Ru intermediate layers as thinly as possible for the economic reasons mentioned above.
In practice, it is set to 0.01 to 0.25μ. Such a thin intermediate layer allows trace amounts of Cu-based base components such as Cu, Zn, and Sn to pass through and diffuse into the Ag, improving sulfidation resistance and wear resistance without actually impairing solderability. ,
Furthermore, it is possible to suppress the fatal defect that occurs when Ag is used in a DC circuit, which electrolytically transfers from the + side to the - side and causes a short circuit, which is becoming more important as the density of electronic devices increases. However, Pd and Ru
It is a harder metal than Cu or Ag, and in particular, electroplated Pd easily absorbs H ₂ during plating and has a strong tendency to hard embrittlement. Excessive thickness exceeding 0.25μ inhibits workability. It causes minute cracks on the surface, exposing the Cu-based substrate and causing oxidation. If the thickness is less than 0.01μ, the Cu-based base component diffuses into the Ag layer excessively, accumulates on the surface of the Ag layer, and deteriorates solderability. The electronic component material of the present invention has the above-mentioned structure and is manufactured by electroplating, ion plating, sputtering, vacuum evaporation, mechanical cladding, or a combination thereof. In particular, the electroplating method can quickly plate a coating of an accurate thickness on any desired part using simple equipment. That is, after cleaning the Cu-based substrate by a conventional method, Pd or
Electroplated in Ru plating bath, then Ag or
Produced by electroplating in an Ag alloy plating bath.
As a Pd plating bath, Pd(NH ₃ ) ₂ (NO ₂ ) ₂ or Pd
There are neutral to alkaline baths containing (NH ₃ ) ₄ Cl ₂ as a main component, strong sulfuric acid baths containing sulfite complexes, and commercially available baths containing various additives can also be used. Ru plating baths include nitrosylsulfamic acid baths and nitroso chloride baths. Examples of Ag plating baths include cyanide baths, thiocyanate baths, pyrophosphoric acid baths, and iodide baths. The present invention will be described in detail below with reference to examples. Example 1 A brass plate (35% Zn) having a thickness of 0.42 mm was degreased and pickled by a conventional method, and then the following plating bath was used to produce the Ag plating lead frame material for diodes shown in Table 1. Pd plating bath (Tanaka Kikinzoku Paradikku MS) Pd 10g/PH 8.5 Bath temperature 55℃ Current density 3.0A/dm ² Ru plating bath (Tanaka Kikinzoku Lutenex) Ru 10g/PH 1.5 Bath temperature 60℃ Current density 3.0A/dm ² Ni plating bath 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 bath AgCN 3g/ KCN 30g/ Bath temperature 20℃ Current density 3A/dm ² Ag plating bath AgCN 30g/ KCN 40g/ K ₂ CO ₃ 20g/ Bath temperature 20℃ Current density 1.5A/dm ² Ag plating lead frame material for diodes is usually in the form of a strip (width 5.0 mm, length , 0.5mm), bent at right angles (R = 0.5mm), soldered a Si chip to one end (95%Pb-5%Sn, temperature 320℃, 1 minute), and then sealed with resin and cured ( Temperature 180℃, 5 hours,
(in the atmosphere) and then soldered to a printed circuit board. In this soldering, the wetted area when immersed for 5 seconds in a eutectic solder bath at a temperature of 235℃
90% or more is required. 100℃ to guarantee the above Ag lead frame material will not deteriorate due to storage and bending process.
After heating for 24 hours at a temperature of
One end was dipped in 5% Sn (temperature: 320°C) for 5 seconds and the wetted area was measured. Next, this was heated in the air at a temperature of 180°C for 5 hours, and the other end was dipped in a eutectic solder bath at a temperature of 235°C for 5 seconds to measure the wetted area. After bending the frame material, the end faces were sealed with a lacquer and a 5% salt water spray test was conducted for 24 hours in accordance with JIS-Z-2371 to examine the occurrence of blue copper corrosion at the bent portions. Furthermore, two pieces of this were placed opposite each other at a spacing of 4.0 mm on qualitative filter paper, and the temperature was 60°C.
A voltage of 100 V was applied in a humidifying tank with a humidity of 95%, and the insulation resistance was measured after 48 hours. These results are shown in Table 1.

[Table] As is clear from Table 1, the present invention materials No. 3 to No. 6 in which the thickness of the Pd or Ru intermediate layer is 0.01 to 0.25μ
It can be seen that both have excellent solderability, no blue copper corrosion, and good insulation resistance. In contrast, comparative materials No. 1 and No. 1, which do not form an intermediate layer.
Comparative material No. 10 and Pd intermediate layer thickness of 0.005μ.
In No. 2, the eutectic solderability after heating in the air was significantly reduced, and in comparison material No. 7, the Pd or Ru intermediate layer was thicker.
~ 8 and comparative material No. 9 with a Ni intermediate layer, the eutectic solderability decreased after heating in the air, and blue copper corrosion was generated in the bending part, and in particular, the performance was comparable to that of the inventive material. It can be seen that in order to obtain this, it is necessary to add Ag to a thickness of 4μ or more without providing a Ni intermediate layer. Furthermore, comparative materials No. 7 to 8 with a Pd or Ru intermediate layer thickened to 0.5μ, comparative materials No. 9 and 12 with a Ni intermediate layer,
Comparative material No. 11, in which Ag was thickened by 4μ or more without providing an intermediate layer, had a lower insulation resistance and a higher risk of short circuit. In this way, the material of the present invention has excellent solderability, corrosion resistance,
It highly satisfies properties such as workability and migration, and by forming a thin intermediate layer of Pd or Ru with a thickness of 0.01 to 0.25μ, it is possible to save Ag with a thickness of 3μ or more, which is economically advantageous. It is. Example 2 Using a phosphor bronze strip with a thickness of 0.25 mm, it was degreased and pickled using a conventional method, and then treated with Pd or Pd in the same manner as in Example 1.
Ru plating was performed, and then Ag plating with a thickness of 1.5 μm was applied thereon to produce the Ag plating contact materials for connectors shown in Table 2. This contact material is usually press-formed and then connected to the electric wire by soldering the end, and the contact part is connected to the circuit pin on the printed circuit board with a load of about 100g, and the contact resistance is 10mΩ over long-term use. The condition is that it does not exceed. Like normal contacts, the contact part is protruded into a convex shape to stabilize contact with the other party. To prevent this contact material from deteriorating during storage and molding processing, it was kept under humidified conditions at a temperature of 60°C and humidity of 95% for 1000 hours, and then immersed in a eutectic solder bath at a temperature of 235°C for 5 seconds to wet the solder. I looked into gender. In addition, after holding the above humidifying conditions for 1000 hours, heating it to a temperature of 250℃ for 10 minutes, and then holding it in the air at a temperature of 120℃ for 200 hours, a 100g Ag rod with a hemisphere with a radius of 4.0mm at the tip was heated. Press with load, current 100
Contact resistance was measured in mA. 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 2.

[Table] As is clear from Table 2, the present invention materials No. 15 to 16 exhibit good properties in both solderability and contact resistance. On the other hand, with comparative materials No. 17 to 18 in which an excessively thick Pd or Ru intermediate layer was formed, no deterioration in solderability was observed, but the connector contact resistance increased significantly, and compared with Material No.13, 19, 20
It can be seen from this that the thickness of the Ag layer needs to be 4.5μ or more. In this way, according to the present invention, by making the Pd or Ru intermediate layer thinner than conventional wisdom, it is possible to create a unique and useful combination of Cu or Cu alloy as a base and Ag or Ag alloy as a covering material. It has been shown to be effective and its properties have been significantly improved. In particular, it is resistant to high temperatures, has greatly improved workability, is suitable as a material for electronic parts that require precision and a variety of functions, and is economically superior, resulting in significant industrial effects.

Claims (1)

[Claims] 1. Ag or
In materials coated with Ag alloy, the substrate and Ag or
Ag coating characterized by providing an intermediate layer made of Pd or Ru with a thickness of 0.01 to 0.25μ between Ag alloy layers
Cu-based electronic component materials. 2. The Ag-coated Cu-based electronic component material according to claim 1, wherein the coating thickness of the Ag or Ag alloy layer is 0.2 to 2μ.