Examination of non‐shrinkage firing using low‐temperature co‐fired alumina containing a small quantity of Cu–Ti–Nb–Ag–O additive

Abstract In this study, we examined non‐shrinkage firing in the planar direction using low‐temperature co‐fired alumina (LTCA) containing a small quantity of Cu–Ti–Nb–Ag–O additive. A good restraint effect was obtained using AL‐43‐L alumina as a constraint layer whose particle diameter was several times larger (1 to 2 μm) than that of alumina in the LTCA material TM‐5D (0.2 μm). The x ‐ y shrinkage ratio of the non‐shrinkage fired sample using AL‐43‐L as the constraint layer was within 2 %. However, the density of the non‐shrinkage fired sample was much lower than that of the normal shrinkage fired sample. By producing a powder using a freeze‐dry method, we obtained a well‐sintered alumina with a relative density of approximately 95 % at 950°C, which is lower than the melting point of silver. That is, we achieved both suppression of the shrinkage rate in the x ‐ y direction and ensured sinterability below the melting point of silver. The thermal conductivity of the sample was 16.2 W/mK, which is extremely high for low‐temperature co‐fired ceramics materials.