JP4339669B2 - Colored surface treatment aluminum plate - Google Patents

Description

The present invention relates to solder resistance and comprising a surface treatment film having excellent color thermal radioactive is formed on the plated aluminum sheet stained surface-treated aluminum plate.

  In recent years, in surface-treated metal plates applied to applications such as metal containers, home appliance chassis, cabinets, electronic component substrates, steel plates as substrates, black, white, gray and other achromatic colors, red, blue, A colored surface-treated steel sheet is used in which a surface-treated film colored in a color such as yellow, green, brown, pink is formed on a steel sheet. The surface-treated steel sheet used for these applications may be subjected to soldering for bonding with other parts or members where it needs to be bonded after being molded into a predetermined shape. In the treated steel sheet, the soldered wettability of the colored colored surface treatment film was poor, and it could not be applied to applications requiring soldering.

  In particular, in the use of electronic component boards, it is necessary to suppress the temperature rise of components loaded in a narrow housing or with almost no gap as electronic devices are miniaturized and densified. In a printed circuit board, a board to which a heat sink for heat dissipation is attached is used in order to suppress the temperature rise of components. For example, as shown in FIG. 1, the heat sink is provided in close contact with at least one surface of a large heating element 1 such as a printed circuit board. The larger the contact area, the greater the heat conduction and the greater the amount of heat dissipation. As a material used for the heat sink, it is preferable to use a material having excellent thermal conductivity so that heat can be rapidly absorbed from the heating element. Further, as shown in FIG. 1, it is preferable that the heat sink 2 is provided so as to extend away from the heating element 1 because heat is radiated from the extended portion, so that the heat radiation of the surface of the heat sink 2 is excellent. In FIG. 1, arrow 3 indicates the direction of heat conduction, and arrow 4 indicates the direction of heat radiation.

  As a conventional technology for steel sheets with excellent solder wettability, tin plating is applied to the steel sheet, and then the plating mainly containing at least one of zinc, nickel, and cobalt is applied to the tin plating, or zinc, nickel, cobalt Two-layer plated steel sheet for solder, in which any one or more of tin, iron, lead, or copper is plated with civilian plating showing a lower potential than the standard electrode potential of tin Is known (see, for example, Patent Document 1). Since this plated steel sheet does not have a protective coating layer with excellent corrosion resistance like a chromate-treated film, the corrosion resistance is not sufficient, and the formation of a corrosion product film may also deteriorate the solder wettability. .

  In addition, an Sn—Zn alloy layer is formed on a surface-treated steel sheet in which a Sn—Zn alloy layer is formed on the steel plate, or a surface treatment layer made of either Ni plating or Fe—Ni diffusion layer is formed on the surface. A surface-treated steel sheet for an environmentally friendly electronic component in which an inorganic film mainly composed of magnesium phosphate is formed on a Sn—Zn alloy layer is known (for example, see Patent Document 2). This inorganic film mainly composed of magnesium phosphate can give high corrosion resistance to the Sn—Zn alloy, but due to its stability, particularly when a weakly active or inactive flux containing no chlorine is used. It has a drawback of poor solderability.

  Furthermore, since these two-layer plated steel sheets for solder and surface-treated steel sheets for electronic components use steel sheets as substrates for forming surface-treated films, the steel is exposed at the cut surface, so that red rust is likely to occur. Have.

  In the case of the heat sink using the steel plate-based material as described above, it can be joined by soldering directly to the printed circuit board. However, when heat dissipation is further required, a material based on an aluminum plate is preferable. However, since it is difficult to perform soldering directly on a printed circuit board based on an aluminum plate, a pin dedicated to soldering is generally used for a heat sink. And soldered to the printed circuit board through the pins. The following trials have been made as a surface-treated steel sheet using an aluminum plate having good solder wettability and thermal conductivity as a substrate.

  For example, a surface-treated metal plate in which a tin plating layer is formed on a plate made of an aluminum plate or an aluminum-based alloy via a nickel plating layer is provided (for example, see Patent Document 3). In this surface-treated metal plate, a nickel plating layer is formed on a base material such as a hot-dip aluminum-plated steel plate using a vacuum deposition method, and then tin plating is performed. In this method, nickel plating and tin plating require a large plating apparatus such as a vacuum apparatus, the film forming speed is low, the productivity is poor, and it is difficult to manufacture at a low cost.

Also, tin or tin excellent in solderability, in which a tin layer or tin alloy layer is coated on an aluminum base material and a tin concentration gradient layer is formed at the interface between the aluminum base material and the tin layer or tin alloy layer. An alloy-coated aluminum plate is provided (see, for example, Patent Document 4). In this tin or tin alloy-coated aluminum plate, the aluminum base plate and the tin layer or tin alloy layer are formed by electroplating tin on the aluminum plate and then heating, or by passing the aluminum plate through molten tin or tin alloy. A tin concentration gradient layer is formed at the interface of the metal and tin is plated. However, the adhesion between the aluminum substrate and the tin layer or tin alloy layer is poor, and the tin plating film is formed on the aluminum substrate particularly when bending is applied. It has a defect that it is easy to peel off.
JP-A 63-277786 Japanese Patent Laid-Open No. 2002-249885 JP 05-345969 A JP 09-291394 A

Therefore, the present invention does not require a large-scale plating apparatus such as a vacuum apparatus, can be manufactured at low cost with excellent productivity, has excellent plating adhesion, and has excellent solder wettability and excellent heat radiation. The object is to provide an aluminum plate .

Colored surface-treated aluminum plate of the present invention for solving the above-mentioned problems, on a substrate made of an aluminum plate, galvanized 0.005 to 0.5 / ^{m 2} from the substrate side, of 0.2 to 50 g / ^{m 2} nickel Plating, 1 to 50 g / m ² tin plating is formed, and 0.05 to 10 μm aqueous urethane resin containing 1 to 50% by weight of coloring pigment or 1 to 50% by weight of coloring pigment is contained thereon A film made of a water-based acrylic resin containing rosin of 0.05 to 10 μm is formed.

In the colored surface-treated aluminum plate, the colored pigment is preferably a black pigment.

  In the present invention, an aluminum plate having rust resistance is used as a substrate, and a plated aluminum plate having excellent adhesion to the substrate and having a plating layer having solder wettability is applied to a water-based urethane resin or water-soluble resin having excellent solder wettability. Since a colored surface treatment film is formed by further adding an achromatic or chromatic coloring pigment to a water-based acrylic resin containing a modified rosin and drying it, the solder wettability by the meniscograph method is less than 10 seconds. Excellent solder wettability, excellent thermal radiation with a thermal emissivity of 0.1-0.9, and excellent thermal conductivity of 40 W / m · K or more. ing. Therefore, it can be suitably applied as an electronic device casing, an electronic component substrate, and a heat sink that require excellent solderability and thermal radiation. According to the method for producing a colored surface-treated aluminum plate of the present invention, a large plating apparatus such as a vacuum apparatus is not required, the productivity is excellent and the production can be inexpensively performed, the plating adhesion is excellent, and the excellent solder wetting is achieved. And a colored surface-treated aluminum plate having excellent heat radiation properties can be obtained.

Hereinafter, the present invention will be described in detail. As an aluminum plate used as a plating substrate, a pure aluminum plate of phoanain or higher, and any of JIS standard 1000 series, 2000 series, 3000 series, 5000 series, 6000 series, and 7000 series aluminum alloy sheets can be used. These aluminum plates are degreased and then acid etched, and then the smut is removed, followed by displacement plating with zinc. Zinc displacement plating is performed through the steps of nitric acid immersion treatment, first zinc substitution treatment, zinc nitrate stripping treatment, and second zinc substitution treatment. In this case, the water washing process is implemented after the process of each process. Since zinc formed by the first zinc substitution treatment and the second zinc substitution treatment is slightly dissolved when nickel plating is performed after the substitution treatment, the coating amount of zinc is 0.005 in the state after nickel plating. It is preferably 0.5 g / m ² . The coating amount is adjusted by appropriately selecting the zinc ion concentration in the treatment liquid and the immersion time in the treatment liquid in the second zinc replacement treatment. When the coating amount is less than 0.005 g / m ² , the adhesion with the nickel plating formed on the zinc is poor, and the plating is easily peeled off when bending is performed. On the other hand, if it exceeds 0.5 g / m ² , the nickel plating becomes non-uniform and the solder strength decreases.

Subsequently, a nickel plating is formed on the substituted zinc. The nickel plating can be formed by using any plating method such as an electrolytic plating method or an electroless plating method. The thickness of the nickel plating is preferably 0.2 to 50 g / m ² in terms of the coating amount. If it is less than 0.2 g / m ² , sufficient solder strength cannot be obtained. On the other hand, if the coating amount exceeds 50 g / m ² , the effect of improving the solder wettability and the solder strength is saturated, which is not advantageous in terms of cost.

Further, solder wettability can be further improved by further forming tin plating on the nickel plating. The tin plating is preferably performed by an electrolytic plating method using a ferrostan bath or a halogen bath. The thickness of the tin plating is preferably 1 to 50 g / m ² in terms of the coating amount. If it is less than 1 g / m ² , the effect of improving the solder wettability is insufficient. On the other hand, when the coating amount exceeds 50 g / m ² , the effect of improving the solder wettability is saturated, which is not advantageous in terms of cost.

  In this way, a plated aluminum plate excellent in solderability can be obtained by forming nickel plating or nickel plating and tin plating on the aluminum plate through zinc substitution plating.

  The plated aluminum plate obtained as described above is also excellent in thermal conductivity, and when used as a heat sink, it can efficiently absorb and dissipate heat from the heating element. Heat dissipation can be further improved by forming a film that improves thermal radiation on the surface. Although the thermal emissivity of the plated aluminum plate is about 0.05 to 0.1, it can be improved to about 0.2 to 0.9 by forming a colored surface treatment film that improves thermal radiation. it can. The colored surface treatment film that improves thermal radiation is formed on the plated aluminum plate as follows.

  As the resin constituting the film, it is preferable to use a water-based urethane resin or a water-based acrylic resin containing rosin. The concentration of these aqueous resins is preferably in the range of 100 to 900 g / L. The rosin contained in the water-based acrylic resin is a rosin soap obtained by neutralizing the carboxylic acid group in the abietic acid molecule, which is the main component of the rosin, with an amine salt, etc. In order to improve the property, it is contained in a water-based urethane resin or a water-based acrylic resin. It is preferable to add to these aqueous resin liquids in the range of 50 to 600 g / L. If it is less than 50 g / L, the solder wettability after aging is insufficient, and if it exceeds 600 g / L, the viscosity becomes high and gelation tends to be difficult.

  Both organic and inorganic pigments can be applied, and one or more pigments of achromatic colors such as black and white, red, blue and yellow can be added to develop the desired color. Let When importance is attached to thermal radiation, it is preferable to use a black pigment. The amount added to the resin is preferably 1 to 50% by weight based on the solid content of the resin. If the content is less than 1% by weight, the vividness of the color tone is poor depending on the color, and if it exceeds 50% by weight, the solderability becomes poor. A more preferable addition amount is 3 to 30% by weight. Further, a colored ceramic powder may be used instead of the pigment. As the colored ceramic powder, it is preferable to use titanium carbide, titanium nitride, titanium boride, tungsten carbide, molybdenum nitride, and a mixed powder obtained by mixing two or more of these ceramic powders.

Add water-based urethane resin containing the above colored pigment or water-based acrylic resin containing rosin to further contain silica and rust preventive agent to improve the corrosion resistance of the plated aluminum plate, and also contain antioxidants etc. By making it, solder wettability can be improved. Silica is preferably added with 10 to 400 g / L of water-dispersible silica in the resin liquid having the above concentration. If it is less than 10 g / L, there is no effect in improving the corrosion resistance. If it exceeds 400 g / L, solder wettability is remarkably lowered, and thermal conductivity becomes poor. When importance is attached to solder wettability, the silicon amount adhering to the plated aluminum plate is preferably in the range of 10 to 400 mg / m ² . As the water-dispersible silica, a silica surface coated with aluminum has a dispersing action and is particularly preferable. The particle diameter of silica is 100 nm or less, preferably 60 nm or less from the viewpoint of dispersibility.

  As the rust preventive agent, an organic amine soap used alone or in combination is used. Organic amine soaps include dodecylamine, oleoyl imidazoline, aminopropyl tallow amine, rosin amine and the like, and the amine can be used after salt formation with carboxylic acid or the like. The styrene / maleic anhydride copolymer is preferably a maleic anhydride copolymerized alkyl ester / ammonium salt. The amount added to the resin solution having the above-mentioned concentration is preferably 10 to 100 g / L. If it is less than 10 g / L, the effect of improving the corrosion resistance is not recognized, and if it exceeds 100 g / L, the solderability is lowered and the thermal conductivity becomes poor.

  Solder wettability is improved by adding an antioxidant to the water-based urethane resin containing the color pigment as described above, and further containing the silica and rust preventive agent or the water-based acrylic resin further containing rosin. Can be made. Antioxidants include sulfur-based antioxidants, but phenol-based antioxidants or phosphate-based antioxidants are preferred, and both may be used in combination. The amount to be added is preferably 0.5 to 100 g / L.

  On the other hand, in applications that do not place great importance on corrosion resistance and in particular those that do not require good solder wettability, and in applications that place particular importance on thermal conductivity, silica, rust preventives, antioxidants are not included, and only pigments are included. It is preferable to use an aqueous urethane resin or an aqueous acrylic resin containing a pigment and rosin.

  One of the resin liquids obtained as described above is applied to one side or both sides of the plated aluminum plate. In this case, the coating film thickness may be changed on the front and back surfaces. As a coating method, a known method such as a dipping method, a roll coating method, a curtain flow coating method, or a spray coating method can be used. However, when performing double-sided coating, taking advantage of the fact that this treatment liquid is water-based, a method of performing coating by dipping and drawing in the subsequent step of the continuous plating step is easy and economical. After applying using any one of these application methods, it is dried to form a colored surface-treated film on the plated aluminum plate to obtain a colored surface-treated aluminum plate. The film thickness after drying is preferably 0.05 to 10 μm. If the thickness of the film is less than 0.05 μm, sufficient solder wettability cannot be obtained. In addition, fingerprints are easily attached when touched with fingers. When it exceeds 10 μm, the effect of improving these characteristics is saturated and the cost merit is lost.

  The colored surface-treated aluminum plate of the present invention thus obtained preferably has a solder wettability of less than 10 seconds according to the meniscograph method (MIL-STD-883B) shown below. When the solder wettability by the meniscograph method exceeds 10 seconds, the heated and melted solder does not sufficiently spread on the surface of the colored surface-treated metal plate, and sufficient adhesive strength with the mating material to be soldered cannot be obtained. The measurement of solder wettability by the meniscograph method is performed as follows. That is, using a SOLDERCHECKER (MODEL SAT-5000, manufactured by RHESCA), a 7 mm wide sample cut out from the above-described colored surface-treated metal plate was immersed in a weakly active flux containing no chlorine, and then maintained at 250 ° C. A sample obtained by applying the above flux to (JIS Z 3282: H60A) is immersed for 2 mm at an immersion speed of 2 mm / second, and a zero cross time until the solder gets wet is measured to obtain solder wettability (seconds).

  In addition, by forming a colored surface-treated aluminum plate by forming a colored surface-treated film on the plated aluminum plate, the thermal emissivity is improved to 0.1 to 0.9, and the thermal conductivity is 40 W / m · K or more. can do.

(Create test plate)
[Plating aluminum plate]
An aluminum alloy plate (JIS 5052 H19, plate thickness 0.5 mm) was used as a plating substrate, degreased with an alkaline solution, then etched in sulfuric acid, then desmutted in nitric acid, and then sodium hydroxide: 150 g / L, Rochelle salt: 50 g / L, zinc oxide: 25 g / L, immersed in a processing solution containing 1.5 g / L of ferrous chloride to perform the first zinc substitution treatment, and then 400 g / L After removing the zinc deposited by substitution by dipping in an aqueous nitric acid solution, the second zinc substitution treatment was performed by dipping in the same treatment solution used in the first zinc substitution treatment. Next, nickel plating was performed on the displacement zinc plating using a Watt bath under the following conditions to obtain a nickel-plated aluminum plate. Part of the nickel-plated aluminum plate thus obtained was further subjected to tin plating under the following conditions using a ferrostan bath to obtain a nickel / tin-plated aluminum plate.

<Nickel plating>
Bath composition Nickel sulfate 300g / L
Nickel chloride 45g / L
Boric acid 45g / L
Bath temperature 55 ° C
pH 3.0
Current density 5A / dm ²

<Tin plating>
Bath composition Stannous sulfate 30g / L
Phenolsulfonic acid 30g / L
Ethoxylated-α-naphthol 2g / L
Bath temperature 40 ℃
pH 2.0
Current density 5A / dm ²

As described above, plated aluminum shown in Table 1 plating numbers A to E was prepared.

Yellow, black with the contents shown in Table 2 in the water-based acrylic resin containing the water-based resin shown in Table 2 and the water-based urethane resin or water-soluble rosin in the water-based resin shown in Table 2 on the plated aluminum plates having the plating numbers A to E. Or a resin liquid containing a red coloring pigment or titanium carbide is applied by dipping / squeezing and then dried at a temperature of 90 ° C. to prepare samples Nos. 1 to 10 and have the following characteristics: Evaluation was performed. Table 4 shows the evaluation results.

[Characteristic evaluation]
<Solder wettability>
Evaluation was performed by a meniscograph method (MIL-STD-883B) using SOLDERCHECKER (MODEL SAT-5000, manufactured by RHESCA). That is, a specimen having a width of 7 mm was cut out from the samples of Sample Nos. 1 to 10, and immersed in a weakly active flux not containing chlorine as shown in Table 3 (Rapics RMA, manufactured by Nippon Solder Industries), and then kept at 250 ° C. Specimens coated with the above flux in a solder bath (JIS Z 3282: H60A) are immersed 2 mm at an immersion speed of 2 mm / second, the time until the solder gets wet is measured, and the zero cross time is measured. evaluated. The shorter the wetting time, the better the solderability. Note that the test was performed in two ways, immediately after sample preparation and at a constant temperature and humidity (60 ° C., 95% RH) for 500 hours. Except for ×, the acceptable range.
◎: Less than 5 seconds ○: Less than 5-7 seconds △: Less than 7-10 seconds ×: More than 10 seconds

<Solder strength>
Two specimens cut out from the samples of sample numbers 1 to 10 with a width of 7 mm and a length of 50 mm and bent into an L-shape are stacked so that the evaluation surfaces face each other in a T-shape. A test piece was prepared in which a 0.5 mm thick steel plate was sandwiched between the portions, and a 0.5 mm gap was formed below the T-shaped vertical bar. After applying the same flux as that used for the evaluation of the solder wettability to the void portion of the specimen, a solder bath (JIS Z, JIS Z) was used, using a solder checker (SAT-5000, manufactured by Resca). 3282: H60A), the void portion of the specimen was dipped to a depth of 10 mm, held for 5 seconds, filled with solder in the void portion, and taken out to obtain a T peel specimen. Next, using Tensilon, the T-shaped horizontal bar part of the T-peel test piece is sandwiched and pulled, and the solder filling part of the T-shaped vertical bar part is peeled off to measure the solder strength. The strength was evaluated.
◎: 4 kgf / 7 mm or more ○: Less than 3-4 kgf / 7 mm △: Less than 1-3 kgf / 7 mm ×: Less than 1 kgf / 7 mm

<Plating adhesion>
A specimen having a width of 7 mm and a length of 50 mm was cut out from the samples of sample numbers 1 to 10 and bent at 90 °. A scotch tape was applied to the bent portion (outside), and then peeled off. The plating adhesion was evaluated based on the following criteria.
○: No peeling is observed.
X: Peeling is recognized.

<Thermal emissivity>
A specimen of 100 mm × 100 mm was cut out from the samples of sample numbers 1 to 10, and the thermal emissivity was measured using an emissivity meter (Dand S AERD emissivity meter, manufactured by Kyoto Denshi Kogyo Co., Ltd.) and evaluated according to the following criteria.
A: Thermal emissivity 0.5 to 0.9
○: Thermal emissivity 0.1 to less than 0.5 Δ: Thermal emissivity 0.05 to less than 0.1 ×: Thermal emissivity less than 0.05

<Thermal conductivity>
A specimen having a width of 5 mm and a length of 10 mm was cut out from the samples of sample numbers 1 to 10, and the thermal conductivity was measured using an optical AC thermal constant measuring device (PIT-R2 type, manufactured by Vacuum Riko). evaluated.
○: Thermal conductivity of 40 W / m · K or more Δ: Thermal conductivity of 30 W / m · K or more and less than 40 W / m · K ×: Thermal conductivity of less than 30 W / mK

<Color clarity>
Using the spectrocolorimeter (MODEL: CM-3500d, manufactured by Minolta Co., Ltd.) for the samples Nos. 1 to 10, the L value, the a value, and the b value were measured. Those within the range of the values are indicated by ○ as acceptance criteria. A value that deviated from the acceptance criteria was shown as x for failure.

これらの特性評価結果を表４に示す。

These characteristic evaluation results are shown in Table 4.

As shown in Table 4, the colored surface-treated aluminum plate of the present invention is excellent in solder wettability, has high solder strength, and has high heat emissivity and thermal conductivity and excellent heat dissipation. Moreover, it is excellent also in color clarity as a colored aluminum plate. Therefore, the colored surface-treated aluminum plate of the present invention can be suitably applied as a heat sink with excellent heat dissipation that can be soldered.
On the other hand, among the plated aluminum plates provided as comparative examples, the aluminum plate with plating number D has a small amount of nickel coating, and the aluminum plate with plating number E has a small amount of galvanized film, particularly in terms of plating adhesion. In addition, good solder wettability and solder strength were not obtained.

  The colored surface-treated aluminum plate of the present invention has excellent solder wettability, high solder strength, and high thermal emissivity and thermal conductivity and excellent heat dissipation, so it is suitable as a heat sink for high-density printed circuit boards and the like. Since it is not only usable but also excellent in color clarity, it can be suitably applied to electronic equipment casings that require solderability and heat radiation.

Schematic which shows the joining state of a heat sink and a heat generating body.

Explanation of symbols

1 Heating element 2 Heat sink 3 Direction of heat conduction 4 Direction of heat dissipation

Claims (2)

On a substrate made of an aluminum plate, galvanized 0.005 to 0.5 / ^{m 2} from the substrate side, the nickel plating 0.2 to 50 g / ^{m 2,} to form a tin plating 1 to 50 g / ^{m 2,} An aqueous acrylic resin containing 0.05 to 10 μm aqueous urethane resin containing 1 to 50% by weight coloring pigment or 0.05 to 10 μm rosin containing 1 to 50% by weight coloring pigment. A colored surface-treated aluminum plate, characterized by forming a film comprising: The colored surface-treated aluminum plate according to claim 1, wherein the colored pigment is a black pigment .

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