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Various reflow profiles have been applied on different no-clean fluxes amount in removing the oxide layer of high lead solder bump. The wafers exposed to open air induce an oxide layer on the high lead solder bump. This oxide layer eventually creates the non wet phenomena in flip chip packaging. An experimental study is carried out by varying different soak time of the reflow profile to optimize the effectiveness of the flux in solving the eutectic and controlled collapse chip connection (C4) high lead bump issue, which indirectly solves the non wet issue. Visual inspection on high lead solder bump under high power microscope is carried out after reflow process. Die pull test is carried out on the solder joint strength analysis to test the solder bump strength. Besides, experiments on substrate cleanliness test, nonwet phenomena and die misalignment are also conducted with useful hints to be implemented.

The role of underfill is expanding from preserving solder joint reliability to also protecting fragile low-k chip dielectric layers in flip chip packaging. The aim of this study is to pre-evaluate or presume the reliability performance of several commercial underfill materials for the balance protection against four critical area of locations (four factors) such as package warpage, low-k interface layer dielectric (ILD) or underfill/die interface layer, solder bumps and back die edge in Plastic Flip Chip Ball Grid Array (FCPGBA) packages. The distribution of thermal strain and stress of the package, warpage measurement and solder bump fatigue for different commercial underfills have been assessed and compared via a linear and nonlinear viscoplastic finite element analysis (FEA) under accelerated temperature cycling conditions. The data properties of underfills for simulation have been extracted by using Thermal Mechanical Analyzer (TMA) and Dynamic Mechanical Analyzer (DMA). Both experiments were conducted in-house due to consistent test method compared with the data from supplier. The results from FEA were summarized and discussed to characterize the performance of each underfill material. A total of four factors of equal ranking importance have been considered in this underfill pre-selection approach. The position in the ranking is used to predict the most suitable underfill to be selected for good flip chip package reliability.

Five different types of clean flux and no-clean flux, which are mainly used in flip chip die attach, have been analyzed in respect to the wettability of eutectic solder bump in flip chip PBGA. An experimental study is carried out to measure the spreading area of the eutectic solder bump processed with different types of flux. Various types of clean and no-clean flux are measured and placed on top of silicon die. The effect of the flux has been observed by measuring the spreading area of the eutectic solder bump processed with different types of clean and no-clean fluxes by using Leica Quin Colour (RGB) after the heat treatment. Comparative studies on clean and no-clean fluxes are therefore obtained. Clean flux has shown better wettability on the high lead solder pad proving it to be the optimum choice as also supported by the die pull results. Moreover, the fluxes are tested under thermal gravimetric analyzer (TGA) to observe the flux weight loss on the melting point of eutectic solder bump to correlate with the earlier results.