Mechanical strength enhancement of low temperature co-fired multilayer ceramic substrates by introducing residual stress

Two low temperature cofirable ceramic materials with thermal expansion coefficients (TEC) of 5.9 ppm/K and 6.6 ppm/K, respectively, were used in this work to introduce residual stress by the multilayer cofiring process. Theoretical calculation and finite element method (FEM) simulation were used to optimize the multilayered ceramic substrate composition design to obtain enhanced mechanical performance. Based on the failure condition of materials, the multilayered ceramic substrate has an optimal thickness ratio of the surface layers to the whole laminate (sandwich structure). Indentation method was used to measure the surface residual stresses and 3-point bending tests were used to measure the mechanical strength. Enhanced mechanical strength of 404 MPa can be obtained when the thickness ratio of surface layer to the whole laminate is 0.19.