JP3340401B2 - Whisker-free galvanized products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a galvanized product free of whiskers.

[0002]

2. Description of the Related Art Covers of various parts in a wide range of electronics fields such as computer equipment and communication equipment,
Electric and electronic components such as cases and chassis such as chassis are required to have high corrosion resistance, solderability, and electrical characteristics.These components have strong anticorrosive properties against base materials such as iron products. Zinc plating has been awarded for its excellent corrosion resistance and low cost.

[0003] However, this zinc plating has a problem that whiskers are liable to be generated over time near room temperature. The generation of zinc whiskers causes short-circuit failures in electrical and electronic components, such as short-circuiting with the mating component in the circuit or between terminals, causing noise or insulation failure.Especially, electrical and electronic components are becoming smaller and smaller. As the density increases, the complexity increases, the current decreases, and the gap between the components becomes narrower, the short-circuit failure due to the generation of zinc whiskers increases. Short-circuit failure may occur when zinc whiskers are generated, when zinc whiskers grow and cross-link each other, or when one piece of grown zinc whiskers falls off due to impact and is cross-linked at other parts. . The generation and growth of this zinc whisker combine various elements in a practical atmosphere,
It appears within one month at the earliest and one to two years later.

The present inventors have previously proposed a bright galvanized product and a bright galvanizing method for electric and electronic parts in which the generation of zinc whiskers has been completely prevented (Japanese Patent Laid-Open No. 9-3684).
No.). However, the zinc concentration g / L of the galvanizing bath is 1
7 to 55 g / L, and [sodium cyanide concentration g / L
/ Zinc concentration g / L] (hereinafter referred to as M ratio) is 2-3.
Therefore, there has been a problem that the cost of chemicals such as zinc and bluish soda is increased, and particularly, wastewater treatment of bluish soda is troublesome and cost is increased. Also, the internal stress during processing remains extremely large in the plating material, and M
When plating was performed under conditions where the ratio was close to 2, whiskers were sometimes generated.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to improve the invention described in Japanese Patent Application Laid-Open No. 9-3684, reduce the cost of chemicals, simplify wastewater treatment, and reduce costs. An object of the present invention is to provide a bright galvanized product for electric and electronic parts which is completely prevented from generating zinc whiskers and has excellent corrosion resistance.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the lattice strain of the plating film and the carbon content in the plating film are all within specific ranges. It was found that the problem could be solved by doing so. In order to make the lattice strain of the plating film and the carbon content in the plating film both within specific ranges, it is preferable to use the method disclosed in
Zinc is plated using a zinc cyanide plating bath having a zinc concentration g / L lower than that described in JP-A-3684 and a slightly increased M ratio, or the zinc cyanide plating bath is used. When plating on a substrate, it was found that the problem could be solved by plating so that the electrodeposition stress of the plating film measured by a spiral contract meter was within a specific range, and the present invention was accomplished. .

In order to solve the above-mentioned problems, the invention according to claim 1 has a caustic soda concentration of 50 to 160 g / L and a zinc concentration of 50 to 160 g / L.
10 to 30 g / L, [blue sodium soda concentration g / L / zinc concentration
g / L] is more than 3 and 4 or less, and a brightener is added.
Plating on a substrate using a zinc cyanide bath
The lattice strain of the plating film measured using an X-ray diffraction apparatus is 0.02 to 0.35%, and the carbon content in the plating film is 0.01 to 0.07% by weight. The present invention relates to a galvanized product free of whiskers. If the lattice distortion of the plating film and the carbon content in the plating film are both within the above specific ranges, a galvanized product for electrical and electronic parts with excellent corrosion resistance, which completely prevents the generation of zinc whiskers, can be obtained. Can be

[0008] By plating zinc with a zinc cyanide plating bath with a reduced zinc concentration and a slightly increased M ratio, the cost of chemicals can be reduced, wastewater treatment can be simplified, and costs can be reduced. The generation of zinc whiskers can be completely prevented, and a glossy galvanized product for electric and electronic parts having excellent gloss and corrosion resistance can be obtained.

According to a second aspect of the present invention, the caustic soda concentration is 50
160 g / L, zinc concentration 10-30 g / L,
Soda concentration g / L / zinc concentration g / L] exceeds 3 and 4
Below, using a zinc cyanide bath with a brightener added
Spiral contract meter when plating on substrate
The electrodeposition stress of the plating film measured by 10 to 65
Sub-plated to become MPa (megapascal)
A lead-plated product, wherein the lattice distortion of the plating film measured using an X-ray diffraction device is 0.02 to 0.35%, and the carbon content in the plating film is 0.01 to 0.07. weight%
The present invention relates to a galvanized product free of whiskers. Lattice distortion and plating
Each of the carbon contents in the sticky coating specified above
Within the range, the generation of zinc whiskers is completely prevented.
Galvanized products for electrical and electronic parts with excellent corrosion resistance
can get. Using a zinc cyanide plating bath with a reduced zinc concentration and a slightly higher M ratio, plating is performed so that the electrodeposition stress of the plating film falls within a specific range, thereby reducing the chemical cost. In addition, wastewater treatment is simplified, cost can be reduced, zinc whiskers can be completely prevented, and glossy galvanized products for electric and electronic parts having excellent gloss and corrosion resistance can be obtained.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The base material used in the present invention is a metal member for electric / electronic parts and the like, and mainly includes a steel-based member, but is not limited thereto, and corrosion resistance is required, for example, copper,
Widely applicable to metal members such as brass.

In the galvanized product of the present invention, the lattice distortion of the plating film measured using an X-ray diffraction apparatus is 0.02 to 0.3.
5%, preferably 0.02 to 0.32%, more preferably 0.02 to 0.29%, and the carbon content in the plating film is 0.01 to 0.07% by weight, preferably 0%. .
01-0.06% by weight, more preferably 0.01-0.06% by weight.
05% by weight. The shaded range in FIG. 1 is the range of 0.02 to 0.35% of lattice strain of the plating film and the range of 0.01 to 0.07% by weight of carbon content in the plating film. As long as the lattice strain of the plating film and the carbon content in the plating film are within the range shown by the oblique lines in FIG. 1, generation of zinc whiskers can be completely prevented.

In the case of ordinary zinc plating, eutectoid impurities such as carbon intervene in zinc crystal grain boundaries, causing distortion in the surrounding metal lattice and increasing internal stress accompanying electrodeposition. When the internal stress in the plating film exceeds a certain value, zinc nodules (hillocks) begin to appear on the surface, and thereafter, it is estimated that zinc atoms are supplied one after another and grow into whiskers. Of course, it is not limited to this concept. Whiskers do not occur within the range of the carbon content and the lattice strain indicated by hatching in FIG.

When the lattice strain of the plating film exceeds 0.35%, whiskers are generated. On the other hand, it is preferable that the lattice distortion of the plating film is smaller as whiskers are not generated, but it is preferable that the lattice distortion is less than 0.02% even if plating conditions such as current density and bath temperature are changed without using a brightener. Practically difficult.

When the carbon content in the plating film exceeds 0.07% by weight, whiskers are generated. On the other hand, it is preferable that the carbon content in the plating film is smaller as whiskers are not generated, but the carbon content is less than 0.01% by weight, for example, without using a brightener and changing plating conditions such as current density and bath temperature. Is difficult in practice.

The lattice distortion of the plating film in the present invention is X
[100], [101] obtained using a line diffraction device,
From the area and the position of each peak of the five zinc diffraction lines of [110], [200] and [201], JEO
L Application Note XR-23, Toshio Sakamaki, “Principle and Application of X-ray Diffraction Method”, 1992, published by JEOL Ltd., page 163.

That is, the lattice strain η of the plating film in the present invention can be obtained by using an X-ray diffraction apparatus [100],
[101], [110], [200] and [201]
Five measures the integral width β ₁ ~β ₅ and Bragg angle theta ₁ through? ₅ diffraction line of zinc, in the following equation (1), Y
Β ² / tan ²に on the axis and β / tan {sin} on the X axis
Is obtained from the Y-axis intercept of a straight line passing through five points when is plotted. β ² / tan ² Θ = λ / ε × β / tan {sin} + 4η ² Equation (1)

In the present invention, the carbon content in the plating film is determined by previously measuring the zinc content ratio (Zn / Fe + Zn) in the sample using an inductively coupled high frequency plasma emission spectrometer, and using a carbon / sulfur analyzer. Measure the amount of carbon in the sample,
It is determined by dividing the carbon content by the zinc content ratio.

The galvanizing bath used in the present invention is not particularly limited. However, in the present invention, a zinc cyanide plating bath containing caustic soda and sodium cyanide can be preferably used. By using a zinc cyanide plating bath, the smut (metal oxide) of the metal member to be plated is removed well, the plating is uniform, the generation of zinc whiskers is completely prevented, and the gloss and corrosion resistance are excellent. Glossy galvanized products for electric and electronic parts can be stably produced on an industrial mass production scale.

The concentration of caustic soda in the zinc cyanide plating bath preferably used in the present invention is 50 to 160 g / L, preferably 60 to 120 g / L, more preferably 75 to 90 g.
/ L. If the concentration of caustic soda is less than 50 g / L, the electrodeposition rate decreases, the anode zinc becomes passivated, the bath temperature rises and the gloss decreases, and the bath becomes dirty due to the passivation of the anode zinc. Problem may occur. If the concentration of caustic soda exceeds 160 g / L, problems such as increased dissolution of anodic zinc, easy decomposition of brighteners, uneconomical use of chemicals, and burden on wastewater are undesirable.

The zinc concentration in the zinc cyanide plating bath preferably used in the present invention is 10 to 30 g / L, preferably 10 to 30 g / L.
To 25 g / L, more preferably 10 to 20 g / L. If the zinc concentration is less than 10 g / L, the electrodeposition rate may decrease. When the zinc concentration exceeds 30 g / L, problems such as poor throwing power and an increase in the amount of blue baking soda to maintain a specified M ratio occur.

The M ratio of the zinc cyanide plating bath preferably used in the present invention is more than 3 and 4 or less, preferably 3.2-4.
More preferably, it is in the range of 3.2 to 3.6. If the M ratio is 3 or less, whiskers may be easily generated. If the M ratio exceeds 4, the amount of blue baking soda used will increase, the electrodeposition rate will decrease, the chemicals will be uneconomical, the wastewater treatment will be burdensome, and the plated products will be roughened. appear.

The sodium cyanide concentration in the zinc cyanide plating bath used in the present invention can be calculated by determining the zinc concentration and the M ratio.

FIG. 2 shows the ranges of the sodium cyanide concentration and the caustic soda concentration of the zinc cyanide plating bath used in the present invention (shaded portions), and FIG. 3 shows the zinc concentration of the zinc cyanide plating bath used in the present invention. And the range of sodium cyanide concentration (shaded area) (M ratio is shown in FIG. 3; M ratio in the present invention is more than 3 and 4 or less), and FIG. 4 shows cyanide used in the present invention. The range of the zinc concentration and the caustic soda concentration of the galvanizing bath (portion indicated by oblique lines) is shown.

FIG. 5 shows the range of sodium cyanide concentration and caustic soda concentration in the zinc cyanide plating bath described in JP-A-9-3684 (the shaded portion), and FIG. 6 shows the zinc cyanide plating. The range of the zinc concentration and the sodium cyanide concentration of the bath (the shaded portion) (the M ratio is shown in FIG. 6; the M ratio in this case is 2-3) is shown in FIG. The range of the zinc concentration and the caustic soda concentration of the plating bath is shown (shaded area).

FIG. 8 shows the concentration of caustic soda on the Z axis, the concentration of zinc on the Y axis, and the concentration of sodium cyanide on the X axis.
The range of the bluing soda concentration is shown three-dimensionally [part shown in (a)].

Similarly, FIG.
The ranges of the caustic soda concentration, the zinc concentration, and the blue cyanide concentration of the zinc cyanide plating bath described in JP-A No. 4 are shown three-dimensionally [portions indicated by (b) (portions indicated by oblique lines)].

In FIG. 8, the range surrounded by A, B, C, and D described on the plane formed by the Y axis and the X axis is the above (A).
Is a projection view on the same plane in the Z-axis direction, and a range surrounded by a, b, c, and d described on the same plane is a projection view on the same plane in the Z-axis direction (b) (hatched line) (The part indicated by).

FIG. 8 shows that the ranges of the sodium hydroxide concentration, the zinc concentration, and the sodium cyanide concentration of the zinc cyanide plating bath used in the present invention are determined by the sodium hydroxide concentration of the zinc cyanide plating bath described in JP-A-9-3684. It is evident that the ranges do not overlap with the ranges of zinc, zinc concentration and sodium cyanide concentration.

In the present invention, the electrodeposition stress of the plating film when galvanizing a substrate using the above zinc cyanide plating bath is 10 to 65 MPa, preferably 10 to 62 MPa.
a, more preferably 10 to 55 MPa, plating can be completely prevented from generating whiskers.

The electrodeposition stress of the plating film is the electrodeposition stress measured by using a spiral contract meter in accordance with JIS H8626 during the galvanization of the substrate, and the twist angle of the spiral piece and the plating film are measured. It is determined from the thickness.

When the electrodeposition stress of the plating film exceeds 65 MPa, whiskers may be generated. On the other hand, the electrodeposition stress of the plating film is preferably as small as possible, but it is usually difficult to make it less than 10 MPa.

FIG. 9 shows the lattice strain (%) of the plating film on the Z axis, the electrodeposition stress (MPa) of the plating film on the Y axis, and the carbon content (% by weight) in the plating film on the X axis. The ranges of lattice strain, electrodeposition stress, and carbon content used in the present invention are shown three-dimensionally [a rectangular parallelepiped part shown by (c)]. (C)
If it exceeds the rectangular parallelepiped portion indicated by, whiskers may be generated.

Examples of the brightening agent used in the present invention include known inorganic compounds such as nickel salts and cobalt salts, and the like.
Organic compounds such as peptone, polyvinyl alcohol, gelatin, heliotropin, coumarin, glue, thiourea, vanillin, formaldehyde resin and piperonal can be used alone or in combination. About 5 to 5 g / L can be suitably used.

When galvanizing is performed within the range of the bath composition described above, the thickness of the galvanizing is not particularly limited.
About 0 μm is preferable. When the film thickness is less than 2 μm, the corrosion resistance is reduced, and when the film thickness is more than 20 μm, the productivity is significantly reduced, which is not preferable.

In the present invention, a chromate treatment can be performed after galvanizing. As a chromate treatment for forming a chromate film after galvanizing, any of colorless chromate, colored chromate, black chromate and the like can be applied. Examples of the chromate solution used here include known chromic anhydride / sulfuric acid / nitric acid system, sodium bichromate / sulfuric acid system, chromic anhydride / sulfuric acid system, etc., depending on the corrosion resistance and color tone of the desired chromate film. It is appropriately selected for use.

[0036]

EXAMPLES The practicality and effectiveness of the present invention will be described below with reference to examples and comparative examples, but it is needless to say that the present invention is not limited to these examples. (Example 1) An iron plate (5 cm x 5 cm) having a thickness of about 1 mm was thoroughly degreased with an alkaline degreaser, and then washed with water to obtain 8% by volume.
The oxide film was dissolved and removed in hydrochloric acid, and washed thoroughly with water. As shown in Table 1, the pretreated base material had a caustic soda concentration of 75%.
g / L, a bluish soda concentration of 33 g / L, a metal zinc ion concentration of 10 g / L, and a bright zinc plating bath containing 3 g / L of a brightener (trade name "J1114" manufactured by Nippon Surface Chemical Co., Ltd.) Then, plating was performed under the conditions of a bath temperature of 30 ° C. and a current density of 3 A / dm ² .

JIS H8 while galvanizing the substrate
The electrodeposition stress of the plating film was measured using a spiral contract meter [manufactured by Yamamoto Plating Test Equipment Co., Ltd.] in accordance with 626. Table 1 shows the measurement results.

X-ray diffractometer [JDX- manufactured by JEOL Ltd.]
3500] was used to determine the lattice strain of the plating film. Table 1 shows the measurement results.

The carbon content in the plating film was measured by an inductively coupled high frequency plasma emission spectrometer [JY17, manufactured by Rigaku Corporation].
0 ULTRACE], the ratio of zinc in the sample was measured, and a carbon-sulfur analyzer [HORIBA, Ltd., EMI
A3200], the carbon content in the sample was measured, and the carbon content was determined by dividing the carbon content by the zinc content ratio. Table 1 shows the measurement results.

The obtained sample was left in a thermostat at 100 ° C. for 3 days, and the occurrence of whiskers was observed at an appropriate magnification with a scanning electron microscope or a stereomicroscope. As a result, no zinc whiskers were found. .

(Examples 2 to 9) In the same manner as in Example 1,
The pretreated substrate was plated with zinc using a bright zinc plating bath having the composition shown in Table 1. In the same manner as in Example 1, the electrodeposition stress of the plating film, the lattice distortion of the plating film, the carbon content in the plating film, and the occurrence of whiskers were measured. Table 1 shows the measurement results.

Comparative Examples 1 to 7 In the same manner as in Example 1,
The pretreated substrate was plated with zinc using a bright zinc plating bath having the composition shown in Table 1. In the same manner as in Example 1, the electrodeposition stress of the plating film, the lattice distortion of the plating film, the carbon content in the plating film, and the occurrence of whiskers were measured. The measurement results are shown in Table 1.

[0043]

[Table 1]

From Table 1, it can be seen that whiskers do not occur when the electrodeposition stress, lattice strain, and carbon content are within the ranges specified in the present invention. On the other hand, when the electrodeposition stress, lattice strain, and carbon content are out of the ranges specified in the present invention, it is found that whiskers are generated.

FIG. 9 shows Examples 1 to 9 and Comparative Example 1.
Lattice strain, electrodeposition stress, and carbon content of ~ 7 were plotted.
○ indicates the measured value of the example, and ● indicates the measured value of the comparative example. The circle with no whiskers is inside the rectangular parallelepiped shown by (c), whereas the circle with whiskers is (c)
It can be seen that it is outside the rectangular parallelepiped indicated by.

[0046]

In the galvanized product according to the first aspect, since both the lattice strain of the plating film and the carbon content in the plating film are within specific ranges, no zinc whiskers are generated and the corrosion resistance and the like are reduced. Excellent, used as galvanized products for electric and electronic parts.

The galvanized product of claim 1, wherein are those sodium hydroxide concentration, zinc concentration, and a specific range of M ratio were obtained by plating on a substrate using a zinc cyanide bath with the addition of brightener Therefore, zinc whiskers are not generated, and they are excellent in corrosion resistance and the like, and can be used as galvanized products for electric and electronic parts. In addition, the cost of chemicals is low, the wastewater treatment is simple, and the cost can be reduced.

In the galvanized product according to the second aspect, when the base material is plated using a zinc cyanide bath to which the concentration of caustic soda, the concentration of zinc, and the M ratio are within specific ranges and a brightener is added, a plating film is formed. Since it is obtained by plating so that the electrodeposition stress is within a specific range, no zinc whiskers are generated, it has excellent corrosion resistance, etc., and it can be used as a galvanized product for electric and electronic parts. In addition, the cost of chemicals is reduced, the wastewater treatment is simplified, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a graph showing the lattice strain of a plating film and the range of the carbon content in the plating film as defined in the present invention.

FIG. 2 is a graph showing a range of sodium cyanide concentration and caustic soda concentration of a zinc cyanide plating bath used in the present invention.

FIG. 3 is a graph showing a range of zinc concentration and sodium cyanide concentration of a zinc cyanide plating bath used in the present invention.

FIG. 4 is a graph showing a range of a zinc concentration and a caustic soda concentration of a zinc cyanide plating bath used in the present invention.

FIG. 5 is a graph showing the range of sodium cyanide concentration and caustic soda concentration in a conventional zinc cyanide plating bath.

FIG. 6 is a graph showing a range of zinc concentration and sodium cyanide concentration in a conventional zinc cyanide plating bath.

FIG. 7 is a graph showing the range of zinc concentration and caustic soda concentration in a conventional zinc cyanide plating bath.

FIG. 8 is a graph three-dimensionally showing the ranges of caustic soda concentration, zinc concentration and sodium cyanide concentration of a zinc cyanide plating bath used in the present invention.

FIG. 9 shows lattice strain, electrodeposition stress,
It is a graph which shows the range of carbon content in three dimensions.

Continuation of front page (56) References JP-A-50-57034 (JP, A) JP-A-47-17630 (JP, A) JP-A-11-229180 (JP, A) JP-A-11-140686 (JP) JP-A-10-244217 (JP, A) JP-A-9-3684 (JP, A) JP-B-47-16521 (JP, B1) JP-B-47-16047 (JP, B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) C25D 7/00 C25D 3/24 H01B 1/02

Claims (2)

(57) [Claims] (1) a caustic soda concentration of 50 to 160 g / L;
The zinc concentration is 10 to 30 g / L, and the sodium cyanide concentration g / L
/ Zinc concentration g / L] is more than 3 and 4 or less,
The substrate was plated using a zinc cyanide bath with an additive
A galvanized product, wherein the lattice strain of the plating film measured using an X-ray diffraction device is 0.02 to 0.35%, and the carbon content in the plating film is 0.01 to 0.07. A galvanized product that does not generate whiskers, which is characterized by weight%. 2. A sodium hydroxide concentration of 50 to 160 g / L,
The zinc concentration is 10 to 30 g / L, and the sodium cyanide concentration g / L
/ Zinc concentration g / L] is more than 3 and 4 or less,
The substrate using a zinc cyanide bath with an additive
When measured by a spiral contract meter
The electrodeposition stress of the plating film is 10-65MPa (megapass
Cal.)
The lattice strain of the plating film measured using an X-ray diffraction device is 0.02 to 0.35%, and the carbon content in the plating film is 0.01 to 0.07% by weight. A galvanized product that does not generate whiskers.