| 摘要 |
<p>A composite sheet material comprises a porous, expanded polytetrafluoroethylene base sheet 1 impregnated with a first resin 2 that has a lower heat-shrinkability than the base sheet, the impregnated base sheet having a covering layer 3 which has a thickness of at least three micrometers and which comprises a second resin whose hardening rate is lower that that of the impregnating resin. The present invention is useful in printed circuit boards wherein a prepreg as above described is laminated with a metal sheet, a resin sheet, or another printed circuit board.</p> |
