Heat Sink Bonding
Attaching boards to a heat sink is a secondary lamination process that requires special materials and processes. This usually requires the absolute minimum flow possible so that the resin from the prepreg does not flow onto areas where components need to be attached. The metal and the board usually have different expansion rates creating process difficulties to maintain flatness of the final assembly.
Arlon provides a variety of low-flow bonding products that may be selected depending on the final property requirements of the finished product. 47N epoxy prepreg is a common choice for external heat sinks because of its very low flow, high adhesion, and capability of lower cure temperatures that can reduce the risk of warpage. The 49N and 51N provide greater thermal resistance and are often the best choice when two boards may be bonded to both sides of a heat sink. The 37N and 38N are polyimide low flow prepregs that match up well with PWBs manufactured with polyimide resin systems that require higher operating temperatures with the finished PWB.