Printed circuit boards (PCBs) have a wide range of applications in electronics where they
are used for electric signal transfer. For a multilayer build-up, thin copper foils are alternated with
epoxy-based prepregs and laminated to each other. Adhesion between copper and epoxy
composites is achieved by technologies based on mechanical interlocking or chemical bonding,
however for future development, the understanding of failure mechanisms between these materials
is of high importance. In literature, various interfacial failures are reported which lead to adhesion
loss between copper and epoxy resins.
The invention of multi-layer boards triggered the miniaturization of electronic products and
continued to drive PCB manufacturing technology towards smaller and more densely packed boards
with increased electronic capabilities. Thereby, manufacturing is dependent on the adhesion between
copper and epoxy composites. Due to increasing component density in PCBs and decreasing line width
of copper wires and interconnects, the temperature within an electronic device can reach up to 200 ◦C
during operation. Weak copper/epoxy joints cause failures during the application of multi-layer
boards. Crack growth at the interface of the copper/epoxy joint and subsequent delamination are the
consequences. In addition, when advancing to thinner copper foils, finer copper patterns or application
in the high frequency sector, the type of bonding between copper and epoxy resin is of high importance.
Improving the adhesion between the copper and the polymeric backing is crucial in providing better
performance, resistance to cracking and delamination and, therefore, higher reliability.
