The inventive core for electrical connecting substrates, particularly for printed circuit boards and foil circuit boards, has an inner layer (I) with a columnar structure and on either side, metallic cover layers (A,A'), the columnar structure of the inner layer (I) comprising columns (9.1,9.2), which...http://www.google.com.hk/patents/US5442143?utm_source=gb-gplus-share專利 US5442143 - Core for electrical connecting substrates and electrical connecting substrates with core, as well as process for the production thereof
