JPS5871507A - Conductive paste - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thick film conductive paste for plating and low temperature firing.

When forming conductors, resistors, and dielectrics as circuits on a substrate using thick film technology, external electrodes may be formed using the conductors in the final step. In this case, firing Ontei is 1.1
- When the resistor is placed in the opposite direction, its characteristic value changes significantly. For this reason, the conductor that will become the external electrode is fired for 500
~t! ; It is generally carried out at a temperature of about O0C.

However, the conventional four-city pace l- for low-temperature firing had the following drawbacks. That is, conventional conductive pastes are composed of noble metal powders (including alloys) such as Ag, Pa, Pt, and Au, glass powder, bismuth oxide, and an organic vehicle.
so-qso Suitable for OC firing, has strong adhesive strength between the fired film and the substrate, and can be soldered. While doing so, apply such a conductive paste on the board.
Even if it is baked at a temperature of approximately 200°C, sufficient adhesive strength cannot be obtained. This is because bismuth oxide does not soften at such low temperatures and does not contribute to the adhesion between the conductive film and the substrate. For this reason, conductive pastes for firing at SOO~500C do not contain bismuth oxide, but instead increase the amount of glass powder to improve adhesive strength.

However, the conductive film formed from a conductive paste with such a composition usually has poor solderability, and therefore, when soldering is required, the conductive film is solder plated, but semi-1 fl plating treatment is used. Then, the adhesive strength of the film tended to decrease markedly. The reason for this is thought to be that pbo and B2O3 in the glass are soaked with the acid in the plating solution.

The present invention eliminates the drawback described in E and provides a low-temperature firing phase homocentric paste that can withstand plating treatment.

In order to achieve this object, the conductive paste of the present invention includes 700 parts by weight of noble metal powder, PbO-, B203-5in2 glass powder, and 2! ~20 parts by weight, zirconia powder 7~7
It is distinctive in that it is dispersed in a base organic vehicle/L consisting of 0 parts by weight.

The noble metal powder used in the present invention is the same as that used in the conventional thick film conductor, and includes Ag, Pa,
It is a simple substance such as Pt or Au, an alloy, or a mixture thereof. Ag SAg-Pa, Ag-Pt in terms of price
etc. are preferred. The particle size of the noble metal powder is suitably 1 to io μm.

The glass powder must be softened or melted during firing to adhere the noble metal powder to the substrate and its side parts; therefore, the softening point is 10 to 200°C, which is the firing temperature r''.
Low glass or required. For this purpose PbO-B
203-5in2 type glass is suitable.

For example, when firing at Otsu 0O0C, pbo Otsu 0, B,
0310°S 102 J O glass (softening point about 560°C) can be used. PbO-B2
O3-8iO2 glass is Zn○, BaO, Al2O3
, TlO2, ZrO2, etc. may be contained in small amounts.

The particle size of the glass powder is suitably pulverized to about -325 mesh. The addition ratio of glass powder is 1 part noble metal powder
00 parts by weight 1! I: It is necessary to set it to -20 parts by weight. If it is less than 25 parts by weight, the adhesive strength with the substrate is insufficient;
If the amount exceeds 0 parts by weight, the conductivity of the fired film decreases and the surface of the fired film cannot be plated uniformly. O 2 zirconia (Z r O2) powder is added to improve the acid resistance of the fired film. The addition ratio of zirconia powder should be 7 to 10 parts by weight per 100" parts of noble metal powder. If it is less than 1 part by weight, the effect of improving acid resistance will be small, and if it exceeds 70 parts by weight, the conductivity of the fired film will be improved. In addition, the adhesive force between the substrate and the fired film decreases, making it impossible to bond the fired film uniformly.

A suitable zirconia powder has an average particle size of about 3 μm.

The base material consisting of the above-mentioned precious metal powder, glass powder, and zirconia powder is kneaded with an organic vehicle to form a uniform paste. The organic vehicle may be that used in conventional thick film pastes. Examples include those obtained by dissolving ethyl cellulose in butyl carbitol acetate and terpineol VC in a weight ratio of about 70 to 20. The ratio of the base material to the vehicle may be determined in relation to the final viscosity of the paste. The standard addition ratio is about qo parts by weight per 700 parts by weight of the main ingredient, Aojin 4 powder.

The paste prepared in this manner can be processed and fired in the same way as conventional conductive pastes.

The four-electrode paste of the present invention may be baked directly onto a glass or ceramic substrate, or it may be applied directly to a glass or ceramic substrate. Z
, a conductor, a resistor, a dielectric, etc. formed in L- can be overlaid and baked.

Below is the actual experiment 191] Ibi/J Misu.

Experiment A/~? 0 Using parts by weight of silver powder lamp and 5 parts by weight of palladium powder as noble metal powder, PbO: B2O3: 5in2-60:1
0:10 (weight ratio) glass powder/, , 15.3.
10.20 and 5 parts by weight, zirconia powder 0, /,! ,i
Pastes were prepared for all combinations of o and/or 2 parts by weight, and the properties after firing were measured. As the organic vehicle, a terpineol solution containing 20% by weight of ethyl cellulose F was used, and 110 parts by weight of each of the above combinations was applied.

The prepared paste was placed on a 7 inch square alumina substrate with a line width of 2J microns and a total length of 3/2. The following uniform plating property and acid resistance tests were conducted on the sample which was screen printed with a zigzag pattern of TILII, dried at about 13oC for 10 minutes, and then baked at toooC.

(1) Plating property Plating was performed using a two-watt bath (containing nickel sulfate, nickel chloride, and boric acid), and it was examined whether nickel was uniformly electrodeposited on the surface of the phosphoric acid film. If there is no plating on the entire surface, it is not acceptable (marked with an x), but if the entire surface is plated, it is acceptable (marked with an ○,
Particularly good ones are 1 Hani (Yotain) and 12.

(2) Acid resistance: The sample was immersed in a 35% hydrochloric acid aqueous solution at 00C for S minutes, then washed with water at I7, and the steel/less needle 1 was placed vertically.
/C The sample surface was rubbed while applying a load of 100 g to check whether the film peeled off from the substrate.O When the needle passed l, cracks and peeling of the film were observed in the traces, and the film did not adhere at all.I7 Things are not allowed (x mark) and I
7. If the adhesion is maintained, there will be needle stripes on the film.
There are only traces or examples. The paste composition and test results are summarized in the table [7].
Ta.

From the above test results, 2 to 20.4 parts of glass powder per 100 parts of precious metal powder and 7 to 10 parts of zirconia powder.
When it comes to parts by weight, it can be seen that both uniform plating properties and acid resistance are good.

Experimenter 37~5?3 Experiment A,? / contains 95 parts by weight of silver powder, 5 parts by weight of platinum powder, and 116 parts by weight of platinum powder. 'I2 contains 700 parts by weight of silver powder, 5 parts by weight of gold powder, and 700 parts by weight of silver powder for experimental flat plate 33 (
A paste was prepared using 5 parts by weight of glass powder, 5 parts by weight of zirconia powder, and 170 parts by weight of vehicle, respectively, and coated and baked in the same manner as in Experiment A/-30, and the plating properties and acid resistance were investigated. Paste composition and test results are shown. In all cases, satisfactory results were obtained in both uniform plating performance and acid resistance.

Claims (1)

[Claims] (1) 700 parts by weight of noble metal powder, pbo-B203-8
A conductive paste made by dispersing a base material consisting of 2 to 102 parts by weight of glass powder and 7 to 10 parts by weight of zirconia powder in an organic vehicle.