We supply Burn-In PWBs to 60 layers to the ATE industry with high aspect ratios. The\y are used as part of the ASIC reliability testing process during which components are stressed to detect failures. These PWBs consist of sockets to accommodate tested ASICs and are designed to withstand very high temperatures during testing.
Materials used for these PWBs include High-Tg FR4 and Polyimides.
