| This research effort addresses the integration of a dense z-axis interconnect technology, GB-Matrix-4X, manufactured by Shin-Etsu Polymer America, into a 3D thermo-mechanical multi-chip module with two to eight stack layers. GB-Matrix-4X is a matrix of vertical beryllium-copper wires embedded in silicone. Since it is a composite material, accurately determining its mechanical properties is extremely important for estimating long-term reliability of the electronic package.;Five percent compression of the GB-Matrix-4X elastomer was specified to maintain proper electrical contact between substrates. To determine the corresponding force, Tinius-Olsen compression tests up to 15% were conducted on both single and double layer samples of GB Matrix-4X. In addition, these data were used to infer Young's modulus for GB-Matrix-4X. Both series of tests were also conducted with and without alumina (Al2O3) to simulate the contact surface boundary condition between GB-Matrix-4X and the LTCC substrate (2 pieces were used for the single GB-Matrix-4X case, and 3 pieces were used for the 2 layer GB-Matrix-4X case). All compression tests follow the same trends, though the sample to sample scatter is relatively large (+/- 75%). Because GB-Matrix-4X Poisson's ratio is near 0.5 (volume is conserved), the frictional forces between the contact surfaces is important. By carefully accounting for these frictional forces, we infer a Young's modulus (based on no friction) for GB-Matrix-4X of 3.25 MPa. Using this value with the appropriate contact model (we found that a simpler model with infinite friction is suitable in our case), we are able to successfully design a two-board test vehicle which incorporates GB-Matrix-4X. |
