Process for making a high heat-conductive, thick film multi-layered circuit board

A process for making a heat-conductive, thick film multi-layered circuit board, comprising:

• (1) providing a substrate having heat conductivity and resistance to heat, which substrate is a material selected from the group consisting of AlN, SiC/BeO, BeO, SiC, Cu/W and ZrB.sub.2 and has a heat conductivity of at least 40 W/M.degree. K. at room temperature;
• (2) oxidizing a surface of said substrate to form an oxidized layer thereon, said oxidized layer being formed on a layer of said substrate by surface treatment of said substrate in a reducing atmosphere containing water at a temperature of from 1,000.degree. C. to 1,500.degree. C.;
• (3) applying onto the oxidized layer an electrically conductive paste containing therein crystallized glass to form a printed electrically conductive paste layer and heating said printed electrically conductive paste layer to consolidate it;
• (4) applying onto the conductive paste layer an insulating paste comprising crystallized glass as a principal constituent to form a printed insulating paste layer and heating said printed paste insulating layer to consolidate it;
• (5) repeating steps (3) and (4) at least one cycle to form a laminate;
• and
• (6) heating the resultant laminate at a temperature sufficient to consolidate the conductive and insulating layers to form an integral multi-layer circuit board.

A process for making a heat-conductive, thick film multi-layered circuit board, comprising:

• (1) providing a substrate having heat conductivity and resistance to heat, which substrate is a material selected from the group consisting of AlN, SiC/BeO, BeO, SiC, Cu/W and ZrB.sub.2 and has a heat conductivity of at least 40 W/M.degree. K. at room temperature;
• (2) oxidizing a surface of said substrate to form an oxidized layer thereon, said oxidized layer being formed on a layer of said substrate by surface treatment of said substrate in a reducing atmosphere containing water at a temperature of from 1,000.degree. C. to 1,500.degree. C.;
• (3) applying on the oxidized layer an insulating paste comprising crystallized glass as a principal constituent to form a printed insulating paste layer and heating said printed paste insulating layer to consolidate it;
• (4) applying on the insulating paste layer an electrically conductive paste containing therein crystallized glass to form a printed electrically conductive paste layer and heating said printed electrically conductive paste layer to consolidate it;
• (5) repeating steps (3) and (4) at least one cycle to form a laminate;
• and
• (6) heating the resultant laminate at a temperature sufficient to consolidate the insulating and conductive layers to form an integral multi-layer circuit board.