Effect of copper lamination on the rheological and copper adhesion properties of a thermotropic liquid crystalline polymer used in PCB applications

Attempts were made to improve the adhesion and strength properties of a copper clad thermotropic liquid crystalline polymer (LCP) for use in advanced printed circuit board (PCB) applications, through manipulation of processing/laminating conditions. Two types of copper foil were investigated. Most significantly, it was observed during these trials that the presence of the copper itself in a laminated sample dampens the modulus growth rate of the LCP during the recrystallization process, which occurs during the lamination cycle. The amount to which this dampening occurred appeared to depend both on the concentration of higher melting crystals already present in the LCP as well as the type of copper used for lamination. This observation has not been previously reported and is expected to influence modulus calculations relating to the construction of advanced PCB applications using LCPs as the substrate material.