Effects of polyvinylidene difluoride (PVDF) anchoring polymer layer (APL) solder anisotropic conductive films (ACFs) on fine pitch flex-on-flex (FOF) assembly using a thermo-compression bonding method

Abstract

Nowadays, the trends in electronic products requiring high capability, flexibility and I/O density, fine pitch Flex-on-Flex assembly was introduced into packaging area. In this paper, the effects of Polyvinylidene Difluoride (PVDF) Anchoring polymer layer (APL) solder ACFs on fine pitch Flex-on-Flex was investigated. The capture rates and insulation rates have been improved by using PVDF APL ACFs due to the high tensile strength of PVDF layer, the function can be obtained by the ultimate tensile strength (UTS) equipment and optical microscope. According to the results, the capture rates increase as the tensile strength of PVDF increased. In addition, the tensile strength of PVDF layer decreased as the flux activators content in APL increased. Furthermore, after the pressure cooker test (PCT) and 85 $^\circ C$/ 85% (RH) test, the optimized flux activators content in ACFs with 0.5 wt. % in APL and 2 wt. % in NCFs and optimized heating rates showed stability in contact resistance. The PVDF APL solder ACF assembly can be used into the small dimension and high capability electronic products packaging area.