JP2618019B2 - Conductive paint for plating base and plating method using the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a conductive paint for plating undercoat useful for forming terminal electrodes of low-temperature sintering type multilayer chip capacitors, for example, lead perovskite multilayer chip capacitors. Further, the present invention relates to a plating method in which an electrode surface obtained by using the same is impregnated with an organic insulating resin paint.

[Conventional technology]

Multilayer chip capacitors using ferroelectric materials such as barium titanate, which are currently the mainstream, are sintered at a high temperature of 1300 to 1400 ° C. Ag-Pd-based conductive material is used at 850 ° C for the conductive paint for terminal electrodes of this high-temperature sintering type multilayer chip capacitor.
The electrode is formed by sintering to a thickness of 80 to 100 μm, and a Ni plating of 1 to 3 μm and a solder plating layer of 3 to 5 μm are formed on the electrode, and then mounted and fixed on a substrate by a jet soldering method. Is common.

The Ni plating layer has a role of preventing solder erosion due to molten solder of the conductive paint sintered on the capacitor terminal.

However, recently, low-temperature dielectric materials such as lead perovskite, which have characteristics such as high dielectric constant, high capacity, high withstand voltage, low dielectric loss, and excellent high-frequency characteristics, have been developed. Sintering has been developed and the sintering temperature has dropped to below 1000 ° C.

The sintering temperature of the paint for terminal electrodes of this low-temperature sintering type multilayer chip capacitor also needs to be lowered in order to prevent the decomposition of the dielectric material. However,
If the sintering temperature of the conductive paint for terminal electrodes, which has been used so far, is lowered from the conventional temperature of 850 ° C to 550 ° C to 700 ° C, the sintered structure becomes extremely porous and enters the sintered film during plating. There is a problem that the plating solution infiltrates, reduces the dielectric material, and lowers the insulation resistance.

[Problems to be solved by the invention]

The present invention solves the above-mentioned disadvantages, and manufactures a low-temperature sintering type multilayer chip capacitor represented by a lead perovskite-based material that is resistant to jet soldering, has good solder wetting, and has excellent electrical insulation properties. And a plating method using the same.

[Means for solving the problem]

In order to achieve the above object, a first invention of the present invention is to provide silver powder or 50 to 80% by weight of a metal powder containing 1 to 10% by weight of palladium powder with respect to silver powder, and acid-resistant having a softening point of 500 to 700 ° C. Glass powder and PbO-ZnO- having a softening point of 350 to 500 ° C
Those B ₂ O ₃ containing -SiO ₂ based glass powder 2-10 wt%, and an organic vehicle 10 to 48 wt%, and wherein the sintering plating base for the conductive coating material comprising at 550 to 700 ° C. It is.

Further, a second invention provides a plating method of impregnating an organic insulating resin paint in a low-temperature sintering type multilayer chip capacitor coated with the above-mentioned conductive paint for undercoat plating, thermally curing, polishing, washing, and plating. It is a feature.

[Action]

In the first invention, Pb (Ni _1/3 N) having a low sintering temperature of 550 to 700 ° C.
b _2/3 ) O ₃ , Pb (Mg _1/3 Nb _2/3 ) O ₃ , Pb (Fe _2/3 W _1/3 ) O ₃ ,
Pb (Fe _1/2 Nb _1/2 ) O ₃ is suitable for use as a terminal electrode for lead perovskite-based low-temperature sintering type multilayer chip capacitors.

The average particle size of the silver powder is preferably 0.5 to 3.0 μm. 1 to 10% by weight, preferably 3 to 10% by weight of silver powder or silver powder
By adding 5% by weight of palladium powder, the sintering density of the conductive paint is improved, and the adhesive strength between the sintered film and the dielectric material is improved.

Further, the finer the palladium powder, the better the alloying efficiency with the silver powder becomes.

The metal powder is used in the conductive coating in the range of 50 to 80% by weight, and if it is less than 50% by weight, the thickness of the electronic electrode is insufficient, and if it exceeds 80% by weight, including addition of glass powder,
Uniform paint properties cannot be ensured.

As the acid-resistant glass powder, there is an SiO ₂ —B ₂ O ₃ —TiO ₂ —RO system (RO is MgO, CaO, ZnO, BaO, SrO). The average particle size 1
It is preferable that the thickness be as fine as not more than μm.

If the softening point of the acid-resistant glass exceeds 750 ° C., the sintering property of the conductive paint is significantly deteriorated in the sintering temperature range of 550 to 700 ° C. for the terminal electrode conductive paint. If the softening point of the acid-resistant glass is less than 500 ° C., the content of SiO ₂ and TiO ₂ in the glass component is low, and the acid resistance is poor.

The in _{PbO-ZnO-B 2 O 3} -SiO 2 based glass, there is no drop to lower the flow temperature of the resistant acidic glass exceeds 500 ° C. softening point. If the softening point is lower than 350 ° C., this composition cannot be produced.

Acid-resistant glass powder of the above glass powder mixture and PbO-ZnO
-B ₂ O ₃ -SiO ₂ -based glass powder is mixed in an acid-resistant glass powder and PbO-ZnO-B ₂ O ₃ with respect to 10 parts of the glass powder mixture.
It is desirable that each -SiO ₂ based glass powder is 1 to 5 parts.

Further, the content of the glass powder mixture needs to be 2 to 10% by weight, and if it is less than 2% by weight, the plating solution is more likely to penetrate into the sintered conductive paint film, and the adhesive strength of the terminal electrode and the insulating property are increased. The resistance value decreases. On the other hand, if the content exceeds 10% by weight, the amount of glass exposed on the surface of the sintered terminal electrode increases, so that wetting of nickel plating is hindered.

When a glass powder mixture limited to a composition range of 2 to 10% by weight is used, it melts effectively even at a low sintering temperature of 550 to 700 ° C, diffuses into a dielectric material, and is uniformly dispersed in a terminal electrode layer. And sintered.

The organic vehicle which is one of the coating components of the present invention comprises ethyl cellulose, butyl carbitol, butyl carbitol acetate, terpineol, petroleum naphtha, an alkyd resin, a plasticizer, a dispersant, and the like. The method for obtaining the conductive paint may be a conventional method. That is, it is obtained by uniformly kneading the above-mentioned predetermined amounts of the metal powder, glass powder and organic vehicle at room temperature with a three-roll mill. The content of the organic vehicle is preferably 10 to 48% by weight.

If it is less than 10% by weight, the viscosity of the paint becomes too high, and if it exceeds 48% by weight, on the contrary, the viscosity becomes too low, and there is a problem in forming a uniform coating film on the end portion of the chip capacitor.

The application of the conductive paint to the end portion of the chip capacitor may be performed by a method such as a Palomar method.

Further, in the second invention, it is necessary to perform a plating process in order to enhance the insulating properties of the low-temperature sintered type multilayer chip capacitor. For this purpose, the organic insulating resin paint is repeatedly impregnated into the pores of the conductive paint sintered film under reduced pressure. As the organic insulating resin paint, an electrically stable thermosetting material such as a silicone resin or an acrylic resin is preferable, and a silicone resin is particularly excellent.

As a method of impregnating the organic insulating resin paint, the resin paint is poured into a chamber containing a ceramic capacitor depressurized to about 1 Torr using a vacuum pump, and the pores of the conductive paint sintered film are filled with the resin. Fill with paint. Next, the mixture is centrifuged to remove excess resin paint adhering to the ceramic capacitor, and placed on a mesh net to be thermally cured.

Curing temperature and curing time vary depending on the resin, but 150 to 300
The treatment is performed at 10 ° C. for 10 to 40 minutes, preferably at 200 ° C. for 30 minutes.

After the thermosetting treatment, barrel polishing is performed for about one hour in a container filled with an abrasive to remove the organic insulating resin paint remaining on the conductive paint sintered film. As the abrasive, SiC100 mesh powder is preferably used.

Furthermore, in order to clean the polished surface of the conductive resin paint sintered film, the surface is subjected to ultrasonic cleaning with a 5 to 10% aqueous solution of a mineral acid for 10 to 60 seconds, and then ultrasonically washed to obtain a surface having good plating wetness. To form As a plating method, it is preferable to perform barrel plating in a plating bath containing no halogen ions.

Example 1 A lead green perovskite-based dielectric material Pb _1-x Sr _x (Mg, W) O ₃ was prepared, and a capacitor green chip was prepared using an internal electrode paste of Ag85 / Pb15 composition. ° C
To obtain a 3.2 × 1.6 mm type Z5U multilayer chip capacitor. The following conductive paint for plating base was applied to the chip capacitor terminals, dried, and then sintered at 650 ° C.

Plating base conductive paint composition for low-temperature sintering Silver powder (average particle size 2 μm) 35% by weight Silver powder (average particle size 1 μm) 32% by weight Palladium powder (average particle size 0.1 μm) 3% by weight Acid-resistant glass powder (softening point 580) ° C.) * 4 _{wt% PbO-ZnO-B 2 O} 3 -SiO 2 based glass powder (softening point 360 ° C.) 3
Wt% organic vehicle 23 _{wt% * SiO 2 -TiO 2 -B 2} O 3 -MgO-CaO-Na 2 O-K 2 O (SiO 2 = 30wt%, TiO 2 = 20wt%) silicone resin to the chip capacitor 10 % Xylene solution (Shin-Etsu Silicone KR-282) was repeatedly vacuum impregnated three times, dried at 100 ° C, and finally thermally cured at 200 ° C for 30 minutes. Next, dry polishing the electrode surface using SiC powder,
The surface of the electrode was activated by treatment with a nitric acid solution, and plating was performed in the order of nickel and tin under the following conditions.

Nickel: Watt bath (pH = 4.5) Carboxy tin bath: pH = 5.5 (manufactured by Kizai Co., Ltd.) The cross section of the obtained plated product showed a three-layer structure that was not different from that of a high-temperature firing type terminal. The initial electrical characteristics before and after plating are as shown in Table 1, indicating that the deterioration due to plating was eliminated.

[Example 2] BaTiO _{3 was} prepared using the terminal electrode paint for plating base described below.
Using the lead perovskite-based material stabilized in the above, a plating type multilayer chip capacitor obtained in the same manner as in Example 1 was measured. As shown in Table 2, satisfactory electric characteristics were obtained.

Low-temperature sintering plating conductive coating composition Silver powder (average particle size 1.5 μm) 37% by weight Silver powder (average particle size 1.0 μm) 35% by weight Acid-resistant glass powder (softening point 580 ° C) 5% by weight ZnO-B ₂ O ₃ -SiO ₂ -Li ₂ O system glass powder (softening point 430 ° C.) 2
Wt% organic vehicle 21 wt% Comparative Example A terminal electrode was formed by baking at 650 ° C. in the same manner as in Example 1 using a terminal electrode paint containing bismuth oxide powder having the following composition, and then nickel plating and tin plating were performed.

Plating base conductive paint composition Silver powder (average particle size 1.5 μm) 65.0% by weight Palladium powder (average particle size 0.1 μm) 5.0% by weight PbO-B ₂ O ₃ —SiO ₂ glass powder 1.0% by weight Bismuth oxide 3.0% by weight Organic Vehicle 26.0% by weight The results are summarized in Table 3.
In particular, insulation resistance failure was remarkable, and conductive products accounted for half.

[Effects of the Invention] According to the present invention, plating of a terminal electrode of a low-temperature sintering type multilayer capacitor which is a lead perovskite system has been achieved. The plated terminal electrode was extremely resistant to solder erosion, and no deterioration in electrical characteristics due to plating was observed. Therefore,
Jet soldering becomes possible, and the applications of lead perovskite multilayer chip capacitors are expanded, and the effect is extremely large.

Claims (2)

(57) [Claims] 1. A silver powder or 50 to 80% by weight of a metal powder containing 1 to 10% by weight of palladium powder based on silver powder, an acid-resistant glass powder having a softening point of 500 to 700 ° C. and a softening point of 350 to 500
℃ of _{PbO-ZnO-B 2 O 3} -SiO 2 based glass powder 2-10 wt%
And 10 to 48% by weight of an organic vehicle, and 550 to 700%.
Conductive paint for plating underlayer sintered at ℃. 2. A low-temperature sintering type multilayer chip capacitor coated with the conductive coating for undercoat plating according to claim 1 is impregnated with an organic insulating resin coating, thermally cured, polished, washed, and plated. A plating method characterized in that: