Surface Activated Bonding Method for Flexible Lamination

A short review is given on the flexible lamination of Cu/LCP by using the modified surface activated bonding (SAB) method. It includes a comprehensive investigation on the adhesion improvement and mechanism, interface quality in terms of mechanical and electrical integrity, and fine pitch patterning [5-7]. Ar-rf plasma cleans the LCP surface and produces dangling sites on the LCP with reduced oxygen. This LCP surface reacts with deposited Cu. Heating in Ar and N₂ gases enhances the reaction resulting in strong adhesion. Heating in O₂ gas reduces adhesion because of the oxidation of Cu across the interface. The source of oxidation is the permeation O₂ gas through the LCP film, and the softening caused recrystallization of Cu foil at high temperature heating. Threefold lower loss in conduction of SAB processed laminate than that of conventional heat laminate was due to smooth interface of the SAB processed laminate. A plausible adhesion mechanism of Cu/LCP is the bonding of Cu adhesion sites (cleaned) to plasma induced dangling sites of LCP surface (Cu deposited), and thermal reconstruction of Cu deposited layers. The SAB processed Cu/LCP has been identified as a suitable candidate laminate for emerging microelectronic, MEMS, and biomedical microsystems.