JPH0241588B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an aluminum composite material having a plating layer of an easily solderable metal such as copper. More specifically, the present invention relates to an aluminum composite material in which a plating layer of an easily solderable metal is provided with a primer layer interposed therebetween. [Prior Art] Aluminum has the disadvantage of being difficult to solder, but aluminum composite materials with a plating layer of easily solderable metals such as copper have the advantages of aluminum, such as good thermal and electrical conductivity, light weight, and low cost. Since it can be used as is, it is industrially useful as a variety of structural materials or as a component material for electrical and electronic equipment. By the way, since it is not possible to form a copper plating layer with good adhesion even if copper is directly plated on the surface of an aluminum material, a layer of zinc is formed by zincating the surface of the aluminum material prior to copper plating. Conventionally, however, copper plating is then applied on the zinc layer. Furthermore, due to the problem that the resulting copper plating layer tends to peel off at high temperatures when using conventional zincate treatment solutions containing zinc compounds as the main component, recently heat-resistant materials such as iron and nickel are being used. Various zincate treatment solutions and zincate treatment methods containing compounds of metal elements have been developed, and as a result, JIS H
8504-1974, the formation of a copper plating layer having excellent high temperature peeling resistance that passes the heat resistance test specified in Section 13.1 has been realized. However, due to the recent trend of miniaturization of electric and electronic devices and higher density of electric circuits,
The requirements regarding the high-temperature peeling resistance of the copper plating layer are becoming increasingly severe, and therefore even the copper plating-aluminum composite material, which has been sold in the market as a heat-resistant grade, is no longer said to have sufficient heat resistance. For example, when the above composite material is used in the control circuit of a robot that uses high temperatures, it may be exposed to temperatures of 100℃ for a long period of several weeks or months under normal pressure or high pressure.
However, due to this long-term heating, the adhesion of the copper plating layer gradually decreases, causing the problem that the electrical resistance at the interface between the copper plating layer and the aluminum material increases over time. be. This increase in interfacial resistance may cause robot malfunctions depending on where the composite material is used. In other applications, the plating layer-aluminum composite material is used under conditions where it is repeatedly and rapidly heated and cooled between extremely low temperatures of around -50°C and high temperatures of over 100°C. However, in conventional heat-resistant grade products, the copper plating layer may peel off due to such repeated thermal shocks. Furthermore, in many cases, parts of other electronic devices are soldered onto the copper plating layer of this composite material, but the adhesion of the copper plating layer decreases due to localized heating during soldering. However, the copper plating layer may also peel off. When forming a copper plating layer on an aluminum material, usually the surface is cleaned by pre-treatment to remove oil and fat and aluminum oxide layer adhering to the surface of the aluminum material, and then zincate treatment is performed to clean the surface. A zinc layer is formed and then copper is applied on the zinc primer layer by electroplating or electroless plating. By the way, the inventors' research has shown that if the above pretreatment is insufficient, trace amounts of gas and moisture remain on the surface of the aluminum, the interface between the aluminum material and the zinc layer, etc., and these expand at high temperatures. It was found that the adhesion between the copper plating layer and the aluminum surface gradually decreased. In addition, as mentioned above, even with commercially available heat-resistant grade products that have passed the JIS heat resistance test and have been evaluated as void-free, if evaluated using the void detection method newly established by the present inventors, it is possible to detect voids. There was a large variation in the amount of voids developed, and those with the amount of voids above a certain value showed clearly low heat resistance. In addition, various zincate treatment solutions and treatment methods have been proposed and put into practice, but the treatment solutions,
If the treatment method is selected incorrectly, pinholes may occur in the zinc primer layer formed by the treatment.
Alternatively, since zinc is precipitated in the form of coarse particles, there is a problem in that the surface of the zinc primer layer becomes rough and has large irregularities. These pinholes tend to cause voids to remain, and large, rough irregularities on the surface generally have a smaller surface area than surfaces with small, fine irregularities, and therefore the bonding area with the copper plating layer applied thereon. It is disadvantageous in terms of bonding strength because of its small size, and the bonding strength between the two gradually decreases due to the peeling force caused by the action of the residual expandable substance and high temperature, and in some cases, it may lead to peeling. . [Problems to be Solved by the Invention] In order to meet the severe demands of today, the present invention provides a plating made of easily solderable metal that exhibits high peeling resistance even after long periods of high temperature and thermal shock. The purpose is to provide an aluminum composite material having layers. [Means for Solving the Problems] The present invention is an aluminum composite material having a plating layer of an easily solderable metal on an aluminum material via a primer layer, wherein the primer layer is made of zinc and a heat-resistant metal. The present invention relates to an aluminum composite material in which the number of voids found on the plating layer is 5/10 cm ² or less in a void detection test at 400°C. [Function] First, the aluminum composite material of the present invention must contain a heat-resistant metal in addition to zinc in the primer layer. Due to the presence of such a heat-resistant metal, the zinc precipitated from the zincate treatment solution becomes fine, and as a result, a zinc primer layer is formed that is free from pinholes and has a fine and many uneven surface. For this reason, the bonding force with the easily solderable metal plating layer formed thereon also becomes stronger. Furthermore, in the present invention, the number of voids that appear on the plating layer of the aluminum composite material in a void detection test at 400° C. described below must be 5 or less/10 cm ² . This void detection test makes it possible to detect trace amounts of residual expandable substances that have been overlooked in the past, and also allows the number of voids developed by this test to be 5 or less/10 cm ² , preferably 2.
If it is less than 1 piece/ ^10cm2 , especially less than 1 piece/ ^10cm2 ,
In cases where the zinc layer contains a heat-resistant metal,
Shows excellent heat resistance. The 400°C void detection test in the present invention is a test method newly established by the present inventors to evaluate the high-temperature adhesion of aluminum composite materials, and is conducted under the following procedure and conditions. 400℃ void detection test: A 10mm square sample is placed in an oven set at 400℃ and kept for 10 minutes, then placed in water at room temperature to rapidly cool it, causing a bulge in the easily solderable metal plating layer. Of the large and small bulges that occur, the major axis is 0.2
Items larger than mm are determined to be voids and the number is calculated as a coefficient. [More Specific and Detailed Description of the Invention] In the present invention, it is preferable that the primer layer is denser, and that its surface is as fine as possible and has as many granular protrusions as possible. In particular, the number of granular protrusions (this is a granular precipitate precipitated during zincate treatment) observed when observed with a scanning electron microscope at a magnification of 3000 times is at least 1 × 10 ⁶ pieces/mm ² , especially when at least 3 x ¹⁰⁶
The number of particles/mm ² is preferable. In addition, when observed at the above-mentioned microscope magnification, there are cases where the granular protrusions are so uniformly ultra-fine that they appear to be observed as a smooth surface, and this state is particularly preferable. The primer layer consists of zinc and a heat-resistant metal. The heat-resistant metal plays an important role in making the primer layer have a dense structure without pinholes and achieving the above-mentioned surface condition. Heat-resistant metals with melting points of approximately 800°C or higher, preferably 1000°C or higher, particularly 1200°C or higher, are used, such as iron (Fe), nickel (Ni), cobalt (Co), copper (Cu), etc. ), chromium (Cr)
and manganese (Mn). Preferred combinations include, for example, Zn-Fe-Ni and Zn-Fe-Co.
Examples include Zn-Fe-Ni-Co, Zn-Fe-Ni-Co, etc., but other types can also be used as appropriate depending on the application, required heat resistance, etc. The total amount of the heat-resistant metal is 0.1 to 50% (by weight, hereinafter the same), preferably 3 to 30%. If it is less than 0.1%, the effect of densifying the primer layer cannot be obtained. When it exceeds 50%, the affinity between the primer layer and the aluminum material decreases, and good adhesion cannot be obtained. Note that the composition (weight %) of zinc and heat-resistant metal in the primer layer can be measured using, for example, an X-ray microanalyzer (EPMA). The composition of zinc and each heat-resistant metal differs depending on the application, the required heat resistance, the material of the base aluminum, etc., and can be selected through experiments as appropriate according to each requirement. , the preferred amount of Fe used is 0.5 to 30%, preferably 1 to 15%,
Ni is 0.5-40%, preferably 1-30%, Co is 0.5-40%
30%, preferably 1-20%, Cu 0.05-20%, preferably 0.1-15%, Cr 0.05-20%, preferably 0.1-15%, Mn 0.01-20%, preferably 0.1-15%.
It is 15%. As aluminum materials, various types of aluminum,
For example, soft or hard materials such as pure aluminum, recast aluminum, or aluminum alloys may be used. For example, aluminum alloys include
2014, 3003, 5052, 6063, 6101, etc. are preferred. The shape of the aluminum material is not particularly limited as long as it can form a primer layer and an easily solderable metal plating layer, and it can be shaped into a plate, wire, rod, foil, coil, or block by punching, cutting, or die-casting. It may be processed into various shapes such as a box shape by a method or the like. Therefore, the thickness of the aluminum material is not particularly limited. The constituent metals of the metal plating layer formed on the primer layer include noble metals such as copper, silver, gold, and platinum group elements, soft waxes such as common solder, chinsmith solder, and plumber solder, or nickel and tin. , other easily solderable metals such as lead. The thickness of the primer layer and plating layer may be appropriately selected depending on the application, but the thickness of the primer layer is usually 0.005 to 2 μm, preferably 0.01 to 2 μm.
0.1μm is adopted, and the thickness of the plating layer is 1~
40 μm, preferably 3 to 20 μm is adopted. Further, if desired, a plating layer made of an easily solderable metal different from the metal of the plating layer may be further provided on the plating layer. The thickness of the primer layer can be measured, for example, by the electrolytic method described below. Next, the method for manufacturing the aluminum composite material of the present invention will be described. The preferred manufacturing method of the present invention will be described later, but the aluminum composite material of the present invention
Basically, it can be manufactured by using any of the previously known pre-treatment methods for the surface of aluminum materials, zincate treatment solutions and treatment methods containing salts of heat-resistant metals, and easy-to-solder metal plating methods. can. However, it is fundamentally different from the production of conventional heat-resistant grade products, and the following points should be noted:
Each process, especially the pretreatment process, must be carried out faithfully and carefully. Incidentally, although conventional heat-resistant aluminum composite materials are manufactured using the above-mentioned known pretreatment methods, zincate treatment methods, and metal plating methods, they do not have the heat resistance targeted by the present invention. The reason is thought to be that conventional recognition regarding heat resistance evaluation criteria was insufficient. This is because, from the standpoint of pursuing economic efficiency, manufacturers of aluminum composite materials maintain an attitude of maximizing process simplification as long as it passes the evaluation criteria. As a result, for example, surface cleaning of aluminum materials subjected to zincate treatment is often kept to the minimum necessary, and even after cleaning, trace amounts of oil, fat, aluminum oxide, etc. may remain, and these residuals can cause voids. It causes As mentioned above, various aluminum materials can be used to manufacture the aluminum composite material of the present invention, but those with many scratches and stains on the surface, or those with uneven oxide films, etc. It is preferable to avoid using it, or to polish it smooth before using it, as it tends to cause voids. The aluminum material is then washed with an aqueous solution of caustic alkali, such as caustic soda or caustic potash.
By this cleaning, dust and oil adhering to the surface of the aluminum material are removed at the same time as the aluminum oxide layer on the surface is dissolved. Slightly higher concentration, e.g. 10 to more reliably remove the aluminum oxide layer
It is preferable to use ~70g/aqueous caustic alkali solution at room temperature to 90°C. Furthermore, a small amount of surfactant in the caustic aqueous solution,
For example, by adding a nonionic surfactant, it is possible to effectively clean the inside of minute recesses on the surface of the aluminum material. After that washing,
The caustic alkaline cleaning solution adhering to the surface of the aluminum material is washed with an aqueous nitric acid solution, and then the aqueous nitric acid solution is removed by washing with water. The surface-cleaned aluminum material is then subjected to zincate treatment. The zincate treatment solution basically consists of a water-soluble zinc compound, a water-soluble compound of a heat-resistant metal, caustic alkali, and water. Water-soluble zinc compounds and water-soluble compounds of refractory metals are the sources of the metal components of the primer layer. Examples of water-soluble zinc compounds include zinc sulfate, zinc oxide, zinc nitrate, zinc carbonate, and zinc chloride. There are various water-soluble compounds of heat-resistant metals, but for supplying iron components, examples include ferrous chloride, ferric chloride, iron sulfate, iron nitrate, and ferrous oxide.
For supplying nickel components such as iron and ferric oxide, examples include nickel sulfate, nickel hydroxide, nickel oxide, nickel nitrate, and nickel chloride.For supplying chromium components, examples include chromium sulfate, chromium oxide, chromium nitrate, and chromium chloride. For supplying cobalt components, for example, cobalt sulfate, cobalt oxide, cobalt nitrate, cobalt hydroxide, cobalt chloride, etc. For supplying copper components, for example, copper sulfate, copper oxide, copper chloride, copper carbonate, copper cyanide, hydroxide, etc. Copper, copper nitrate, and other materials for supplying manganese components include manganese oxide, manganese sulfate, manganese carbonate, manganese chloride, manganese hydroxide, manganese nitrate, and the like. The blending ratio of the water-soluble zinc compound and the water-soluble heat-resistant metal compound and the blending ratio of the water-soluble heat-resistant metal compounds are selected depending on the intended composition of the primer layer. Normally water soluble zinc compound 2
It is preferable that the amount of the water-soluble compound of the heat-resistant metal be 0.05 to 100 g/in total. In addition to the above ingredients, caustic alkali is usually added. Caustic alkali is a component that is blended to dissolve the thin oxide film formed on the surface of the aluminum material after the surface cleaning treatment described above, and to form a stable primer layer on the surface of the aluminum material. Examples include NaOH or KOH.
The blending ratio is usually preferably 30 to 500 g/. In order to promote densification of the primer layer, it is preferable to further add a densification promoter such as a complex compound forming agent or an alkali metal cyanide salt. The complex compound forming agent has the effect of complex ionizing metal components to prevent precipitation of heat-resistant metals, and also forming a dense primer layer on the surface of the aluminum material through the synergistic effect of the formed complex ions and other components. This is a possible ingredient. Examples of densification accelerators include tartaric acid, lactic acid,
Oxycarboxylic acids such as citric acid, or alkali metal salts thereof; polycarboxylic acids such as nitrilotriacetic acid, iminodiacetic acid, EDTA, or alkali metal salts thereof; amines such as monoethanolamine, ethylenediamine, triethanolamine; KCN, Alkali metal cyanides such as NaCN; D-erythro-2-ketopentose, D-threo-2-ketopentose, L-erythro-2-
Ketopentose, D-fructose, D-tagatose, L-fructose, D-psicose, L-
Monosaccharides such as pisicose, D-erythrose, D-threose, L-glucose, D-galactose, oxidation products of monosaccharides such as D-gluconic acid and sugar acids, reduction products of monosaccharides such as sorbitol, etc. Metal salts of hydrocarbons include, for example, alkali metal salts. The blending ratio of the densification accelerator is usually preferably 1 to 150g/. The primer layer is formed by immersing the aluminum material in the treatment liquid. The temperature of the treatment liquid is 0 to 0 when using a densification accelerator.
66℃, preferably 10-40℃, soaking time is 10
The time period is from seconds to 5 minutes, preferably from 30 seconds to 1 minute. If a densification promoter such as a complex compound forming agent is not added, the temperature is relatively low, usually 5 to 30°C,
Preferably it is carried out at 10-20°C. In addition to the above methods, the primer layer may be formed by a method such as a vapor deposition method, a sputtering method, or an electroplating method. The aluminum composite material of the present invention is obtained by forming a plating layer of an easily solderable metal on a primer layer.
As a plating method for easily solderable metals, usual plating conditions for each easily solderable metal can be adopted. Next, the aluminum composite material of the present invention will be explained based on Examples, but the present invention is not limited to these Examples. Examples 1 to 16 and Comparative Examples 1 to 8 An aluminum plate measuring 50 cm long, 20 cm wide, and 1.5 mm thick was placed in an alkaline bath (NaOH: 16 g/, Na ₂ CO ₃ : 27
g/) under the conditions shown in Table 1, washed with running water under the conditions shown in Table 1, and then pickled with a 40% nitric acid aqueous solution under the conditions shown in Table 1. Pretreatment was performed by washing under running water under the conditions shown. The pretreated aluminum plate was immersed in a zincate treatment solution (30° C.) having the composition shown in Table 2 for 1 minute to form a primer layer having the composition, thickness, and number of granular protrusions shown in Table 3. The composition of the primer layer was determined by measuring using an X-ray microanalyzer (JXA-50A manufactured by JEOL Ltd.) under the following conditions and comparing it with a standard sample. Acceleration voltage: 25KV Absorption current: 10 ^-8 A Spectroscopic crystal: LiF Counter: GFPC (Gas flow proportional counter) Applied voltage of GFPC: 1.6KV JXA-50A) at 3000x magnification to 1 mm ²
The number of granular projections per area was counted. The primer layer in the present invention has a dense and flat surface. For example, the surface condition of the primer layer formed in Example 10 is shown in FIG. FIG. 1 is a scanning electron micrograph (3000x magnification), which shows that each component constituting the primer has a dense alloy-like structure. On the other hand, as shown in FIG. 2, the conventional primer layer is only in a state in which a large number of particles are connected, and in such a state, frequent occurrence of voids at high temperatures is unavoidable. Furthermore, Figure 2 is a scanning electron micrograph (magnification: 3000) of the surface of the primer layer formed in Comparative Example 3.
times). Next, the aluminum plate on which the primer layer was formed was subjected to copper plating, nickel plating, common salter plating, or tin plating under the following conditions to form a plating layer having the thickness shown in Table 3 on the primer layer. Copper plating Plating bath: CuCN (60 g/) and NaCN (60 g/) Temperature: 80°C Current density: 3 A/dm ² Current application time: 8 minutes Common solder plating Plating bath: 47% aqueous solution of Sn (BH ₄ ) ₂ (200
g/), 50% aqueous solution of Pb(BH ₄ ) ₂ (50 g/) and 42% aqueous solution of HBH ₄ (100 g/) Temperature: 25°C Current density: 2 A/dm ² Current application time: 10 minutes Nickel plating Plating bath: NiSO ₄ (240g/) and NiCl ₂ (45
g/) and H ₂ BO ₃ (30 g/) Temperature: 50°C Current density: 3 A/4 m ² Current application time: 10 minutes Sparrow plating Plating bath: Na ₂ SnO ₃ (150 g/) and NaOH
(20 g/) Temperature: 60° C. Current density: 2 A/dm ² Current application time: 21 minutes Next, the following two void detection tests were conducted on each aluminum composite material. The results are shown in Table 3. (1) JIS method The method described in JIS H8504-1984, Section 13.1 (carried out at 250°C). (2) This is the void detection test at 400°C developed by the present inventors, and the conditions are as described above.

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【table】

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[Table] The following tests were conducted on the aluminum composite materials obtained in Examples 1 to 16 and Comparative Examples 1 to 8. The results are shown in Table 4. (PCT test) The test piece was heated in steam at 2 atm and 121°C for 2000 hours, then dried, and the contact resistance (Ω) was measured using the 4-terminal method at room temperature, and evaluated by the rate of change (%) from the initial value. did. (High temperature storage test) The test piece was heated in air at 150℃ for 1000 hours,
The contact resistance was evaluated by the rate of change (%) from the initial value in the same manner as the PCT test. (Thermal Shock Test) The thermal shock test was conducted in accordance with EIAJ, SD-121-1979. However, on the low temperature side -40
℃ alcohol bath, high temperature side 100℃ water bath,
A cycle of heating and cooling was performed 1000 times in which the time required for moving between both baths was within 5 seconds. Evaluation is the rate of change (%) from the initial value of contact resistance, similar to the PCT test.
I did it at (Soldering test) Soldering was performed 50 times according to the soldering test in JIS H8504-1984, Section 15.2, and the degree of peeling (defective) of the plating layer was evaluated (%).

[Table] [Effects of the Invention] The present invention provides an aluminum composite material that exhibits excellent peeling resistance and stable contact resistance even when exposed to high temperatures for long periods of time or is subjected to thermal shock, and is easy to solder. can be provided. Moreover, since it can be applied to aluminum materials of various shapes, it is possible to produce long ones or irregularly shaped ones according to needs.

[Brief explanation of drawings]

Figures 1 and 2 are scanning electron micrographs (3000x magnification) of the surfaces of the alloy-like structures of the primer layers formed in Example 10 and Comparative Example 3, respectively.
It is.

Claims (1)

[Scope of Claims] 1. An aluminum composite material having a plating layer of an easily solderable metal on an aluminum material via a primer layer, wherein the primer layer is composed of zinc and a heat-resistant metal, and the following: An aluminum composite material in which the number of voids that appear on the plating layer in a void detection test at 400°C is 5 or less/10 cm ² . Note: A 10 mm square sample was placed in an oven set at 400°C and kept for 10 minutes, then placed in water at room temperature and rapidly cooled to create a bulge in the easily solderable metal plating layer. Of which, the major diameter is 0.2mm
The above items are determined to be voids and the number is calculated as a coefficient. 2. The composite material according to claim 1, wherein the primer layer has a thickness of 0.005 to 2 μm. 3 Claims in which the surface of the primer layer to which the plating layer of easily solderable metal is applied has a number of granular projections of at least 1×10 ⁶ /mm ² when observed with a scanning electron microscope at a magnification of 3000 times. Composite material according to item 1. 4. The composite material according to claim 1, 2, or 3, wherein the heat-resistant metal element is at least one selected from the group consisting of Fe, Ni, Co, Cu, Cr, and Mn. 5. The composite material according to claim 4, wherein the total content of heat-resistant metal elements is 0.1 to 50% by weight. 6. The composite material according to claim 1, wherein the easily solderable metal is one selected from the group consisting of Cu, Ni, Sn, and soft wax. 7. The composite material according to claim 1, 2 or 3, wherein the primer layer is Zn-Fe-Co based. 8. The composite material according to claim 1, 2 or 3, wherein the primer layer is Zn-Fe-Ni based. 9. The composite material according to claim 1, 2 or 3, wherein the primer layer is Zn-Fe-Ni-Co based.