Conductor paste for ceramic substrate and electric circuit

1. A conductor paste for a ceramic substrate comprising:

a) a conductive metal powder comprising a silver/palladium co-precipitation powder containing both of silver and palladium;

b) a glass powder; and

c) an organic solvent,

wherein the conductive metal powder has an average particle diameter of not more than 1.2 μm, and the glass powder is a Bi 2 O 3 —SiO 2 —B 2 O 3 type of glass powder, and the content of the glass powder is in a range of from 1 to 6 wt % based on the weight of the paste, and the content of the palladium powder is in the range of 0.1 to 7 wt % based on the total weight of the silver and palladium.

2. The conductor paste according to claim 1 , wherein the conductive metal powder comprises monodispersed particles.

3. The conductor paste according to claim 1 , further comprising, as the conductive metal powder, from 0.1 to 10 wt % of gold or platinum based on the weight of the paste.

4. The conductor paste according to claim 1 , wherein the glass powder has a transition point of from 360 to 450° C., and a softening point of from 400 to 530° C.

5. The conductor paste according to claim 1 , wherein the glass powder has a composition as follows:

Bi 2 O 3 : 65 to 90 wt %

SiO 2 : 0.5 to 8 wt %

B 2 O 3 : 3 to 10 wt %

ZnO: 0 to 8 wt %

Al 2 O 3 : 0 to 3 wt %

TiO 2 : 0 to 3 wt %

alkali metal oxides selected from the group consisting of Li 2 O, Na 2 O, K 2 O and a mixture thereof: 0 to 5 wt %

alkaline earth metal oxides selected from the group consisting of MgO, CaO, BaO, SrO and a mixture thereof: 0 to 5 wt %.

6. The conductor paste according to claim 1 , wherein the content of the conductive metal powder is in a range of from 60 to 92 wt % based on the weight of the paste.

7. The conductor paste according to claim 1 , further comprising a glass softening point adjuster selected from the group consisting of Cu 2 O 3 , CuO, P 2 O 5 , SnO 2 , alkali metal halides, and alkaline earth metal halides.

8. A conductor film formation method comprising steps of: applying onto a ceramic substrate the conductor paste according to claim 1 ; and firing the conductor paste that has been applied to the ceramic substrate at not more than 650° C.

9. An electric circuit substrate having a circuit comprising a conductor film obtained using the conductor paste according to claim 1 .