Multilayer Polymer Substrate for Direct Chip Attachment
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Disclosed is a substrate that provides two different coefficients of thermal expansion (CTE) in a single assembly. The use of a buried island of INVAR* in a copper plane results in a CTE of \3 ppm where the INVAR is located and a value of 16.5 ppm (copper) everywhere else. A multilayer substrate built on top of this plane will be stabilized where a circuit chip is to be located by the INVAR and will match the expansion of an epoxy/glass board otherwise.