Resin composition with high thermal conductivity and method of producing the same

1. A resin composition having high thermal conductivity comprising 40 vol % or more of a matrix resin, 10 to 55 vol % of a thermally conductive filler dispersed in the matrix resin and the balance of a low-melting point alloy connecting the thermally conductive filler to each other and having a melting point not higher than 500° C., wherein the proportion of the volume ratio of the low-melting point alloy to that of the thermally conductive filler is in a range from 1/30 to 3/1, and wherein the thermally conductive filler comprises at least a copper powder and graphite powder.

2. The composition according to claim 1 , wherein the low-melting point alloy is at least one selected from the group consisting of Sn—Cu, Sn—Al, Sn—Zn, Sn—Pt, Sn—Mn, Sn—Mg, Sn—Ag, Sn—Au, Al—Li and Zn—Li.

3. The composition according to claim 1 , wherein the thermally conductive filler further comprises 5 to 15 vol % of a carbon fiber.

4. The composition according to claim 3 , wherein the carbon fiber has a thermal conductivity of 100 W/m·K or higher.

5. The composition according to claim 1 , wherein the matrix resin comprises a heat resistant resin having a deflection temperature of 100° C. or higher under load.

6. The composition according to claim 1 , wherein the composition has a thermal conductivity of 5 W/m·K or higher.

7. A method of producing a resin composition having high thermal conductivity, comprising:

heating a powder mixture including a matrix resin, a thermally conductive filler and a low-melting point alloy having a melting point not higher than 500° C. so as to bring the low-melting point alloy into semi-molten state in which a solid phase and liquid phase coexist, said powder mixture comprising 40 vol % or more of the matrix resin, 10 to 55 vol % of the thermally conductive filler comprising at least a copper powder and graphite powder, and the balance of the low-melting point alloy;

kneading the mixture in a condition which the matrix resin is completely melted; and

molding the mixture into a desired shape.

8. The method according to claim 7 , wherein a proportion of the volume ratio of the low-melting point alloy to that of the thermally conductive filler is in a range from 1/30 to 3/1.

9. The method according to claim 7 , wherein the thermally conductive filler comprises 5 to 15 vol % of carbon fiber.

10. An optical pickup base formed from a resin composition, said resin composition comprising 40 vol % or more of a matrix resin, 10 to 55 vol % of a thermally conductive filler comprising at least a copper powder and graphite powder and dispersed in the matrix resin and the balance of a low-melting point alloy connecting the thermally conductive filler to each other and having a melting point not higher than 500° C., the proportion of the volume ratio of the low-melting point alloy to that of the thermally conductive filler being in a range from 1/30 to 3/1.

11. The optical pickup base according to claim 10 , wherein the optical pickup base has a thermal conductivity of 5 W/m·K or higher.

12. A casing for a fan motor formed from a resin composition, said resin composition comprising 40 vol % or more of a matrix resin, 10 to 55 vol % of a thermally conductive filler comprising at least a copper powder and graphite powder and dispersed in the matrix resin and the balance of a low-melting point alloy connecting the thermally conductive filler to each other and having a melting point not higher than 500° C., the proportion of the volume ratio of the low-melting point alloy to that of the thermally conductive filler being in a range from 1/30 to 3/1.

13. The casing according to claim 12 , wherein the casing has a thermal conductivity of 5 W/m·K or higher.