Low Firing Temperature Multilayer Glass-Ceramic Substrate

A glass-ceramic material, which has a low constant (7.5) and can be sintered at 900°C in air or in a neutral atmosphere, has been found. As a result, it has become possible to prepare a multilayer glass-ceramic substrate which is advantageous for decreasing propa- gation delay. The new multilayer glass-ceramic (MGC) substrate has the following excellent characteristics. 1) Gold and silver-palladium alloys can be used in fabricating wirings or circuit patterns. 2) The new MGC substrate has a high flexural strength of 3000 kg/cm2 (43000 Ib/in2). 3) During the firing process, shrinkage is around 12.5 percent and shrinkage tolerance is extremely small (0.3 percent or less). 4) The thermal expansion coefficient is about 42 x 10 -7 deg -1 (from room temperature to 250°C) and is close to that for silicon semicon- ductor chips. The MGC substrate was experimentally produced and used in multilayer substrates for a multichip package computer sys- tem. It is possible to form via holes easily with 100 pm diameter and to use loo-pm linewidth on a 200~pm line-to-line grid. A green sheet (120 mm square) may have as many as 110 000 via holes punched into it. It has become possible to provide a high-density packaging substrate using this method.