Solder-Free Pressure Contact Micro-Springs in High-Density Flip-Chip Packages

This work investigates electrical pressure contacts based on a micro-spring with orders of magnitude smaller pitch and force than conventional pressure contacts. Flip-chip packages were assembled with hundreds of micro-springs at 20 mum pad-pitch, 40 mum spring-pitch, and an operating force of 0.01 gram on gold pads. These packages are shown to have stable resistance values during both in-situ thermocycle (0 degC to 125 degC) and humidity testing (60 degC at 95% RH). High-speed glitch measurements are performed to confirm the pressure contact does not have intermittent opens during thermocycling. These results suggest that a low-force solder-free pressure spring contact is a viable technology for next generation flip-chip packaging