Flip chip die attach flux evaluation method

Die attach process play an important role for flip chip packaging. The main factors of die attach yield are: process parameter and flux activity. Die attach flux's main function is to promote good wetting during reflow by removing oxidant and pollutants on pad during flux activation stage. Flip Chip package reliability depends on good bump wetting. Therefore, flux has a significant impact on the reliability. The aim of this paper is to study and derive method in flux selection stage. In this paper, the main topic is flip chip die attach flux evaluation items: 1) Flux TGA weight loss test result to compare the influence of void issue. 2) Use flux spread test to confirm flux activity. 3) Boiling temperature test to gauge the boiling properties of flux during temperature reflow and 4. Viscosity test (Worse case) to test the consistency of the flux. After selecting the flux, it is then used on oxidized bump samples to check for effectiveness.