JPH0218574B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Technical field of the invention This invention relates to copper plating using a copper sulfate-sulfuric acid bath;
Concerning a conductive paint that can withstand strongly acidic electrolytic plating solutions such as lead alkanolsulfonate and tin alkanolsulfonate solder plating solutions and has good electrical properties as a ceramic capacitor, particularly satisfying tanδ value, Q value, and IR value. It is something. (b) Prior Art and Problems Conventionally, conductive paint containing silver as a main component has been used for the electrodes of general disc-shaped, wedge-shaped, cylindrical, etc. ceramic capacitors. When this conductive paint is used for terminal electrodes, the firing profile shown in FIG. 1 is generally used, and firing is usually carried out at a maximum temperature of 750°C. General commercially available silver paint contains glass with a melting point of 400 to 600°C, and when it is fired at 850°C, the internal electrode 2 expands and pushes up, forming the element body 1. Terminal electrode 3
There is a problem that a gap 4 is generated between the terminal electrode 3 and the terminal electrode 3 in an extreme case. For this reason, during the plating process, the electrolyte soaks into the
The tan δ and Q value deteriorated significantly, and a stable product could not be obtained. In addition, as a recent trend, measures such as adding palladium powder, nickel plating, and copper plating are being attempted in order to increase resistance to solder corrosion. In particular, the terminal electrodes of multilayer chip capacitors have a silver-palladium ratio of 80-20 to 63-35.
The electrodes are thick, ranging from 30 to 80 μm. Furthermore, both silver and palladium are expensive, and their proportion, including internal electrode materials, in the price of a multilayer chip capacitor reaches 50 to 60%. Moreover,
Even if paint with a high palladium content is used, it is impossible to prevent solder erosion, and the market trend is toward direct soldering on automated lines, so multilayer chip capacitors that do not have to worry about solder erosion are being developed. The demand for this is becoming extremely high. (c) Purpose of the Invention This invention was made in response to such demands, and provides a plating base suitable for manufacturing capacitors with good solder adhesion, no solder corrosion, and excellent electrical characteristics. The purpose of the present invention is to provide a conductive paint for use in industrial applications. (d) Structure of the Invention In order to achieve the above object, the present invention provides silver powder or 50 to 80% by weight of noble metal powder containing 1 to 10% by weight of palladium powder relative to silver powder, and
1-5% by weight of acid-resistant glass powder at 600-900℃,
The composition consisted of 15-49% by weight of organic vehicle. (E) Examples of the Invention The first component of this invention, the silver powder or the noble metal powder containing 1 to 10% by weight of palladium powder relative to the silver powder, is the base material of this invention, and It is used in the paint of the invention in a range of 50 to 80% by weight. If this first component is less than 50% by weight, the thickness of the terminal electrode of the capacitor becomes too thin;
It is actually difficult to maintain good physical properties of the paint in the range exceeding % by weight. According to the experimental results,
It has been found that this proportion is in a practical range of 65 to 75% by weight. Further, as the first component, it is desirable to use silver powder alone from the viewpoint of cost calculation, which not only minimizes the paint cost but also allows the present invention to fully exhibit the characteristics as a conductive paint for plating base. However, it is preferable to add palladium powder to increase resistance to solder eating. Therefore,
After conducting various experiments on the amount of palladium powder added, we found that adding 1 to 10% by weight of palladium powder to silver powder improves solderability and promotes mutual diffusion between internal and external electrodes when applied to capacitors. It turned out that. Furthermore, compared to the amount of palladium powder added to silver in conventional silver-palladium paints (25 to 45% by weight), a small amount is required, so costs can be reduced. Further, it is desirable that the average particle size of the silver powder particles, which is the first component, is 1 to 3 μm. The smaller the particle size of the silver powder, the better the sintered silver surface can be obtained, but if the firing thickness is 40 to 70 μm, cracking and swelling are likely to occur. Therefore, in reality, particles with a particle size of 1 to 2 μm are blended.
In addition, the shape of the particles is preferably thick disk-like crystals. On the other hand, the average particle size of palladium powder particles is 0.1μ
m or less, and ultrafine particles called palladium black are particularly preferred. The acid-resistant glass powder, which is the second component of this invention, always melts at the firing temperature of the capacitor (generally 850° C.) and is added to tightly bond the element and the terminal electrode. This acid-resistant glass powder usually has a melting point of 700-800
℃ is used, and if a glass with a melting point of 850℃ or higher is used, a glass with a melting point of 600 to 800℃ is optionally mixed to ensure that it melts even when fired at 850℃ and tightly bonds the element body and terminal electrode. Determine the composition. The reason why the blending ratio of the acid-resistant glass powder, which is the second component, is 1 to 5% by weight is that within this range, the plating will be deposited well, no peeling will be observed, and the Q value of the plating will be low. This is because it is fully guaranteed. On the other hand, if this proportion is less than 1% by weight, sufficient adhesive strength will not be obtained and the Q value will deteriorate due to plating, while if it exceeds 5% by weight, glass will precipitate on the surface of the fired electrode. This not only hinders plating but also causes peeling between the electrode surface and the plating layer. The acid-resistant glass powder selection method in this invention was carried out as follows. The sample glass powder was thinly placed on a barium titanate disk and heated and melted to vitrify it. After this was immersed in 1N sulfuric acid (40°C) for 5 hours, the state of the remaining glass was observed and the weight loss by dissolution was measured.
This is shown in Table 1. When the remaining glass layer was peeled off from the barium titanate substrate by ultrasonic cleaning, the glass films of No. 2 and No. 8 peeled off despite having a high melting point, but the glass films of No. 2 and No. 8 peeled off despite having a high melting point.
Glasses No. 5 and No. 12 showed no change at all.
Further, each glass No. 5 and No. 12 was not attacked even in a strongly acidic plating bath, and was found to be extremely effective. Moreover, the particle size of this acid-resistant glass powder has an important meaning, especially in the conductive paint for the plating base. If the particle size is significantly larger than the first component, silver powder or palladium powder, for example, 10 μm, the position of the glass particles will be 10 μm due to melting of the glass particles, flow toward the element body, and penetration during firing of the terminal electrode. It becomes a large cavity as it is (see B in Figure 3). After that, even if the cavity is somewhat filled by sintering the silver and palladium particles, it remains as a large hole. Therefore, the staining solution is allowed to penetrate. Figure 4 shows the penetration and precipitation of nickel nickel in nickel metal. but,
If the glass particle size used is minute, the holes will be filled by metallizing and the electrode will be stable with acid-resistant glass distributed. Under these conditions, the particle size of the acid-resistant glass powder in this invention was set to an average particle size of 1 μm or less, which is smaller than the silver particles used. In addition, the composition of the acid-resistant glass is based on 10 to 30% by weight _{of TiO2} , 30 to 60% by weight of _SiO2 , and the remaining substances include _Al2O3 , _B2O3 , _PbO , _{Pb3O4 ,} PbF. ₂ ,
_CaF2 , MgO, CaO, BaO, _ZrO2 , CdO, _{Bi2O3 ,}
Contains Na ₂ O, K ₂ O, etc. In addition, BORAX, feldspar powder, etc. may be used to adjust the melting point. The third component of this invention, the organic vehicle, is
It is used to maintain the form of paint.
For screen printing and dip printing, ethyl cellulose, oil alkyd resin, rosin ester resin, etc. are added to solvents such as butyl carbitol, carbitol acetate, petroleum naphtha, and terpineol. For spraying and brush painting, toluene, xylene, and cellosolve-based solvents with low boiling points may be used.

[Table] Next, the present invention will be specifically explained with reference to Examples. Example 1 Paint composition (A): Ag particles (average particle size 2 μm) 40% by weight Ag particles (average particle size 1 μm) 30% by weight Pd particles (average particle size 0.1 μm or less) 2% by weight Acid-resistant glass powder (No. 1 Table No. 5) 2% by weight Organic vehicle 26% by weight (Ethyl cellulose 10% by weight Terpineol 40% by weight Butyl carbitol 30% by weight Rosin ester resin 20% by weight) Paint composition (B): Ag particles (average particle size 2 μm) ) 40% by weight Ag particles (average particle size 1 μm) 30% by weight Pd particles (average particle size 0.1 μm or less) 2% by weight Acid-resistant glass powder (Table 1 No. 6) 2% by weight Organic vehicle (paint (A) (same composition) 26% by weight The above paint compositions (A) and (B) were respectively applied as terminal electrodes of TC chip capacitors, fired at 850℃, and then nickel and solder were electrically plated using a barrel. A terminal electrode having a three-layer structure as shown in FIG. 5 was obtained. In the figure, 5 is an element body, 6 is an internal electrode, 7 is a silver electrode layer, 8 is a nickel layer, and 9 is a solder layer. The obtained chip capacitor is HP4275A, 1MHz
The Q value was measured. The results are shown in Table 2. Furthermore, terminal electrodes having a three-layer structure were similarly obtained for HiK chip capacitors using the above-mentioned paint compositions (A) and (B). The obtained Hi-type chip capacitor
The tanδ value was measured using HP4275A at 10KHz. The results are shown in Table 3.

【table】

[Table] Example 2 Paint composition (C): Ag particles (average particle size 3 μm) 35% by weight Ag particles (average particle size 1 μm) 35% by weight Acid-resistant glass (Table 1 No. 5) 1% by weight Acid resistance Glass (Table 1 No. 12) 1% by weight Organic vehicle (same composition as paint (A)) 28% by weight The above paint composition (C) was applied as a terminal electrode of a multilayer chip capacitor and baked at 850℃. ,
The occurrence of voids as shown in FIG. 2 was not observed, indicating a good adhesion state, and the three-layer structure with nickel-solder plating also showed good electrical characteristics as shown in Table 4.

[Table] Example 3 Paint composition (D): Ag particles (average particle size 1.0 μm) 50% by weight Acid-resistant glass (No. 5 in Table 1) 1% by weight Organic vehicle 49% by weight (Ethyl cellulose 5% by weight Butyl cellosolve 20% by weight xylene 20% by weight toluene 30% by weight oil alkyd resin 15% by weight) Above coating composition (D) (for spraying or brush painting, viscosity 1
~5POISE) was applied with a brush to a barium titanate disk and fired at 850°C to form an electrode layer with a thickness of approximately 5 μm. Nickel plating and solder plating were performed on this. The properties of this product, such as Cap (PF), tanδ, and IR, are the same as regular products using silver electrodes, and the temperature is 270℃, 60/
Even in the 40 eutectic solder bath, no solder was eaten away by the 30 second dip. The tensile strength after soldering was also the same as that of unplated silver electrodes, and the element body did not break, proving that it had sufficient strength. In each of the above embodiments, the application to terminal electrodes of a multilayer chip capacitor was described in detail.
The conductive paint for plating base according to the present invention is also effective for forming electrodes of leadless capacitors. That is, paint compositions (A), (C), and (D) are applied to a leadless capacitor by a method such as screen printing, brush painting, or spraying, and after baking, a barrel is applied to the resulting electrode. Electric plating (nickel-copper-solder plating or tin plating, nickel-solder plating or tin plating, nickel-copper-silver plating) was performed. As a result, it was possible to obtain a leadless ceramic capacitor that has good solderability, is resistant to solder corrosion, and has excellent electrical characteristics. Further, the present invention can be used for cylindrical ceramics, IC boards, etc., and is particularly effective in preventing solder from being eaten away. (f) Effects of the invention As described above, this invention adds acid-resistant high-melting glass powder containing TiO ₂ and SiO ₂ as fine particles of 1 μm or less to silver or silver-palladium paints, which provides excellent plating. It became possible to produce base paint. As a result, HiK series, TC
Ceramic capacitors of any type can be plated with nickel, solder, tin, copper, silver, etc., which not only makes it possible to obtain ceramic electronic components that have good electrical characteristics and are extremely resistant to solder erosion. In particular, the elimination or reduction of expensive palladium is achieved, which has the advantage of greatly contributing to the cost reduction of chip capacitors.

[Brief explanation of drawings]

Fig. 1 is a graph showing the firing profile of the terminal electrode of a multilayer chip capacitor, Fig. 2 is an enlarged cross-sectional view showing the protrusion and gap of the internal electrode of the multilayer chip capacitor, and Fig. 3 is a graph showing the firing profile of the terminal electrode of the multilayer chip capacitor. FIG. 4 is an enlarged cross-sectional view showing the occurrence of voids due to the elution of nickel. FIG. 4 is an enlarged cross-sectional view showing the penetration and precipitation of nickel due to nickel plating in the terminal electrode of a multilayer chip capacitor. FIG. FIG. 2 is an enlarged cross-sectional view of a sample that has been coated with a paint (paint composition (A)) and then subjected to nickel-solder plating. 1, 5... element body, 2, 6... internal electrode, 3...
Terminal electrode, 4... air gap, 7... silver electrode layer, 8...
Nickel layer, 9...Solder layer.

Claims (1)

[Claims] 1. Silver powder or 50 to 80% by weight of noble metal powder containing 1 to 10% by weight of palladium powder based on silver powder
A conductive paint for a plating base comprising: 1 to 5% by weight of acid-resistant glass powder having a melting point of 600 to 900°C, and 15 to 49% by weight of an organic vehicle. 2. The conductive paint for plating base according to claim 1, wherein the acid-resistant glass powder has an average particle size of 1 μm or less. 3 Acid-resistant glass powder is the main component of TiO ₂ 10~
30% by weight, and 30 to 50% by weight of SiO ₂ .