An analysis on the properties of epoxy based die attach material and the effect to delamination and wire bondability

Silver filled epoxy is widely used as interconnect of chip to leadframe. This paper introduces material analysis method to study effect of epoxy glue properties to delamination and wire bondability in Dual Flat Non Leaded (DFN) package. Five epoxy glues were characterized using TMA, DMA, TGA. DSC, Moisture Absorption Test and Die Shear Test. Epoxy glues were assembled into 5 × 6 × 1mm DFN package and subjected to Moisture Sensitivity Level 3. thermal cycling and autoclave test. Material analysis result is reflected into experimental verification. CTE mismatch between epoxy glue with molding compound, chip, and leadframe is identified as the primary factor causing epoxy glue delamination. High elastic modulus 1034MPa at 260°C is preferred to resist solder reflow stress. Interfacial adhesion degradation at high temperature is another key factor; investigation revealed with chip size 2mm2 high shear strength as 1.98 kg and cohesive mode with 40% epoxy remnants able to prevent epoxy glue delamination. Result showed that at wire bond temperature of 220°C, minimum elastic modulus required for consistent wire bondability is 101MPa base on chip size of 2mm2.