Effects of the functional groups of non-conductive films(NCFs) on materials properties and reliability of NCFs flip-chip-on-organic boards

Abstract

In this study, effects of the functional groups of non-conductive films (NCFs) on materials properties and reliability of NCFs-bonded flip-chip-on-board (FCOB) assemblies were investigated. The most important issue in NCFs-bonded flip-chip-on-board (FCOB) assemblies is thermal cycling reliability. Thermo-mechanical properties such as glass transition temperature (Tg), modulus (E), and thermal expansion coefficient (CTE) of cured NCFs significantly affect to the thermal cycling reliability of NCFs-bonded FCOB assembly. Therefore, this study has been mainly focused on the improvement of thermo-mechanical properties of NCFs by controlling the number of functional groups of NCFs resin. The functionality modified NCFs-bonded FCOB assembly showed significantly enhanced reliability under thermal cycling test environment. To compare the reliability of conventional and modified NCFs-bonded FCOB assemblies after thermal cycling test, electrical analysis and scanning acoustic microscopy (SAM) investigation were performed. Thermal deformations of each NCFs-bonded FCOB assembly under thermal cycling environment were also investigated and quantitatively compared using high sensitivity Twyman-Green interferometry and Portable Engineering $Moir\acute{e}$ Interferometry (PEMI). According to experimental results, the functional groups of NCFs have great effects on thermo-mechanical properties of cured NCFs, thermal deformations, and thermal cycling reliability of NCFs-bonded FCOB assemblies.