Outer lead and die bond reliability in high density TAB

An evaluation of the reliability of solder-reflow outer lead bonds (OLBs) and conductive epoxy die bonds made in the tape automated assembly of high-performance, high-lead-count emitter-coupled-logic (ECL) devices into plastic pin-grid-array packages is discussed. Temperature cycling, thermal shock tests, and thermal resistance measurements were used to test reliability. Solder fluxes for OLBs were also evaluated. No significant degradation was observed in OLB strength after 2000 temperature cycles or 500 thermal shock cycles between 0°C and 100°C. Under more severe conditions from -65°C to 150°C mean OLB strengths degraded by about 35% from 83 to 54 gm between 500 and 1000 cycles. Die bond shear strength degraded by 50% after 500 temperature cycles between -65°C and 150°C at the beginning of the test. Measured thermal resistances of the die bonds were less than 2.5°C/W