JPS5883073A - Electrically conductive paint - Google Patents

Abstract

PURPOSE:To provide an electrically conductive paint capable of forming thick film conductors exhibiting strong adhesion to substrate and excellent solderability, prepared by blending electrically conductive powder, crystalline glass powder, noncrystalline glass powder, powdered bismuth oxide and organic vehicle. CONSTITUTION:The titled paint is prepared by blending (A) electrically conductive powder selected from among silver, gold, palladium, copper, nickel, zinc, etc. and oxides of these metals, (B) crystalline glass powder such as SiO2-Al2O3-CaO or ZnO-PbO-B2O3, (C) non-crystalline glass powder such as PbO-SiO2-B2O3 or PbO- SiO2, (D) powdered bismuth oxide and (E) organic vehicle. (B) and (C) are used in the ratio of 10:90-70:30 by weight. The glass powder and powdered bismuth oxide are used in about 0.5-12 and about 1-20pts.wt., respectively, per 100pts.wt. (A).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conductive paint for forming a thick film conductor on an insulating substrate, which has excellent adhesion to the substrate and has good solderability.

A conductive paint is applied to an insulating substrate such as a ceramic, glass, or enameled steel plate by a method such as screen printing, and then baked to form a thick film conductor. The formed conductor is used as a wiring conductor of an electronic circuit, a terminal electrode of a resistor, an electrode of a capacitor, etc. Lead wires and various electronic components are connected to these conductors by soldering, thermocompression bonding, or other methods. Thick film conductors formed with conductive paints are used by being incorporated into electronic circuits and electronic components, but they often generate heat during use. It may be left in high temperature conditions of up to 120°C for long periods of time. However, conventionally, when used for a long time in such a thermal environment, the adhesion strength between the conductor and the board decreases significantly, resulting in the conductor peeling off or lead wires or parts missing. It had its flaws.

For this reason, there was a desire for something that not only has good soldering properties but also has minimal deterioration in adhesion strength to the substrate even when used for long periods of time in a hot environment.

The present invention is a conductive paint for forming a thick film conductor that meets the above requirements, and is composed of a conductive powder, a crystalline glass powder, an amorphous glass powder, a bismuth oxide powder, and an organic vehicle.

The conductor formed using the electrically conductive paint of the present invention has excellent soldering properties and is also capable of suppressing deterioration of dense layer strength when used in the above-mentioned thermal environment.

Electronic circuits and electronic parts obtained using conductive paints using amorphous glass suffer from a significant decrease in the adhesion strength between the conductor and the substrate due to heat generation during use. Therefore, the present inventors conducted research using crystalline glass instead of amorphous glass, but found that the conductor film obtained when crystallized glass
It was found that the soldering method was poor and could not be put to practical use. This is due to the presence of a large amount of crystallized glass on the surface of the conductor film.However, by using crystallized glass, the adhesion with the substrate is good and thermal deterioration is also significantly improved. Bismuth oxide was added to improve the properties of the product, but contrary to expectations, the properties of the product were not improved. As a result of testing various compounding agents, it was found that when amorphous glass powder was further added to the combination of crystalline glass powder and bismuth oxide powder, the soldering properties were very good, and the heat deterioration resistance was also improved. It was also found that there were no negative effects. This is because the amount of glass present on the six faces of the conductor obtained by adding non-crystalline glass is very small, and it is thought that this improves the soldering properties. The above-mentioned functions and effects include conductive powder, crystalline glass powder, amorphous glass powder, and bismuth oxide powder.
It is produced only when the components are used, and even if one component is missing, the unique effect cannot be obtained.

The conductive paint of the present invention can also be used in cases where soldering is not required. For example, gold may be used as conductive powder to form an electronic circuit, and IJ-wires are thermocompression bonded to this, or semiconductor elements may be mounted on a gold conductor film (7). In addition, since the paint of the present invention forms a conductor with less crinkle on the surface, it facilitates heat compression of lead wires and mounting of semiconductors.

The conductive powder used in the present invention is at least one type of powder selected from silver, gold, radium, platinum, copper, nickel, zinc, and oxides of these metals, and is processed by chemical reduction, It can be obtained by methods such as the sleeping method and mechanical crushing.

As the crystalline glass powder, 5i02-A120J-C
aO system, ZnO-PbO-B2O3 system, ZnO-B2O
3 series, Zn0-Bt03-8102 yarn, ZnO-PbO
-B2O3-8 inch square glass or the like is used. As the amorphous glass, PbO-8i02-BzQs system,
PbO-8i0. system, PbQ-EliO2-Ax2o,
glass, PbO-8iOI B20J11403 glass, etc. are used. If these glasses contain a small amount of crystalline glass, the strength of the bond with the substrate will deteriorate when used in a thermal environment.If there is a large amount of crystalline glass, the adhesion strength with the substrate will deteriorate even when used in a thermal environment. Although it is small, it is difficult to get undulations, making it difficult to join lead wires and mount components.

Therefore, the usage ratio of crystalline glass and amorphous glass is
xfil' is preferably 10=90 to 70:308 degrees O The bismuth oxide powder may be one commonly used for conductive paints.

Examples of organic vehicles include ethylcellulose, nitrocellulose, alkyd fat, etc.
y tallate, terpineol, butylcarpitol acetate.

The conductive paint of the present invention preferably contains 0.5 to 12 parts by weight of glass powder and 1 to 20 parts by weight of bismuth oxide powder per 100 parts by weight of conductive powder. However, the present invention is not limited thereto.

In addition, in the examples, all "parts 1" indicate vehicle weight parts. Example 1 Silver powder 70 parts Palladium powder Filter 0 parts Bismuth oxide powder
8 parts crystalline glass powder (Si02
LA1203 - CaO system) 1 part amorphous glass powder (PbO-Sin. system) 6 parts ethyl cellulose,
22 parts of an organic vehicle prepared with terpineol and butyl carbitol acetate The above ingredients were thoroughly mixed to make a conductive paint, which was applied to an alumina plate by screen printing, and then heated at 150°C for 1 hour.
After drying for 0 minutes, the belt furnace reached a peak temperature of 85.0.
Example 2: Conductor obtained by firing at ℃ Silver powder: 70 parts Palladium powder: 30 parts Bismuth oxide powder
10 parts crystalline glass powder (SiO+2-
A1203-CaO system) 3 parts Amorphous glass powder (Pb
O-8in, -B203 series) 6 parts Organic vehicle containing ethyl cellulose, terpineol, and phthyl carbitol acetate 22 parts A conductor was formed using the above components in the same manner as in Example 1.

Example 3 Silver powder 70 parts Palladium powder 60 parts Bismuth oxide powder
10 parts crystalline glass powder (5i02-A
120. -CaO system) 3 parts amorphous glass powder (PbO
-'5i02 series) 22 parts of an organic vehicle containing ethyl cellulose, terpineol, and butyl carbitol acetate A conductor was formed using the above components in the same manner as in Example 1.

Example 4 Silver powder 70 parts Palladium powder 30 parts Bismuth oxide powder
15 parts crystalline glass powder (5i02
A1t03-CaO system) 4.5 parts Amorphous crow powder (PbO5iOt yarn) 25 parts Organic vehicle containing ethyl cellulose, chiruby, all, and phthyl rubitol acetate
Part 22 F Ingredients A conductor was formed in the same manner as in Example 1.

Example 5 Silver powder 88 parts Palladium powder 12 parts Bismuth oxide powder
1 part crystalline glass powder bed (ZnOB2O
3 series) 6 parts amorphous glass powder (PbO-8i
O2-B, OS yarn) 4s Ethyl cellulose, terpineol, phthyl carbitol acetate i Preparation (-) Organic vehicle 22 parts A conductor was formed using the above ingredients in the same manner as in Example 1.

Example 6 Gold powder 100 parts Bismuth oxide powder 5 parts Crystalline glass powder (Z
nO-B203-8i02 series) 1.5 parts Amorphous glass powder (PbO-8i02 series) 2 parts Ethyl cellulose, terpineol, diethyl phthalate 25 parts of an organic vehicle in which all the components were prepared - A conductor was prepared using the above components in the same manner as in Example 1. was formed.

Comparative Example 1 Silver powder 70 parts Palladium powder 60 parts Bismuth oxide powder
10 parts crystalline glass powder (Si02-A
1203-cao) 7 parts Organic vehicle prepared from ethyl cellulose, terpineol, and butyl rubitol acetate 22 parts A conductor was formed using the above components in the same manner as in Example 1. Q Comparative Example 2 Silver powder 70 parts Palladium powder Filter 0 bismuth oxide powder
10 parts amorphous glass powder (PPbO-
A conductor was formed using the above ingredients in the same manner as in Example 1.

Comparative Example 6 Silver powder 70 parts Palladium powder Filter 0 parts Crystalline glass powder (S
in,,-A120. -CaO type) 6 parts Amorphous crow powder (PbO-8], 02 type) 4 parts Organic vehicle prepared with ethyl cellulose, terpineol, and butyl carbitol acetate
22 parts All of the above components were filtered in the same manner as in Example 1 to form a conductive gold.Comparative Example 4 Gold powder 100 parts Bismuth oxide powder 5 parts Crystalline glass powder (Z
nO-B2O3-8j, 02 series) 6.5s ethyl cellulose, terpineol, diethyl phthalate 25 parts of M machine vehicle, all of which were blended. Conductive gold was formed using the above components in the same manner as in Example 1.

Comparative Example 5 Gold powder 100 parts Bismuth oxide powder 5 parts Amorphous glass powder (
5iOz-PbO system) 6.5 parts M machine vehicle containing ethyl cellulose, terpineol, and diethyl phthalate 25 parts A conductor was formed using the above components in the same manner as in Example 1.

The initial adhesion strength with the substrate of the conductor thus formed, and the properties of adhesion and soldering after being left in a heat environment for a long time were measured, and the results are shown in Table 1. Initial density N strength is 1.51111 x 1.5 Solder plated copper wire with a diameter of 0.51111 is Sn 63 /
After soldering with Pb67 solder, pull this lead wire perpendicularly to the board, and the kyl when the conductor peels off from the board.
Represented by i. The adhesion strength after being left in a heat environment is determined by soldering the lead wire to the conductor and then heating it to a temperature of 150℃ for 1 hour.
The adhesion strength with the board after being held for 00 hours was measured in the same way as the initial dense layer strength.
．． When 5 sheets of 5N63/Pb37z dowel balls are placed on a conductor and held on a hot plate heated to 230°C for 20 seconds, the spread of the no-da balls is expressed as FLOW%, and 0F10W% is expressed by the following formula. I mean, the bigger it is...
/Dinner is good quality.

However, for Example 6 and Comparative Example 4.5, Sn6ro/P
In 50/Pb 50/- instead of b37 solder
I used .

Table 1 (Note) Regarding Comparative Example 1.5.4, the lead wire.../
Adhesion strength was not measured because it could not be attached. In Comparative Example 2.5, the adhesion strength decreased significantly after being left at 150° C. for 100 hours.

As is clear from the examples, the conductor formed using the conductive paint of the present invention has good soldering properties, so that the connection between lead wires and electronic components can be made firmly. Even if exposed to the pot temperature for a long time, there is little loss of adhesion strength, so it can withstand use in hot environments.

Claims (1)

[Claims] conductive powder, crystalline glass powder, amorphous glass powder,
A conductive paint consisting of bismuth oxide powder and an organic vehicle.