First demonstration of copper-plated through-package-via (TPV) reliability in ultra-thin 3D glass interposers with double-side component assembly

Abstract

This paper reports the first reliability demonstration of copper-plated laser-drilled through-package-vias (TPV) in ultra-thin 3D glass interposers with double-side component assembly. This was accomplished with four major innovations: 1) TPV geometry design for low stress, 2) fabrication of TPV with minimum defects, 3) interconnection and assembly process development, and 4) package design for minimal warpage during assembly and thermal cycling test (TCT). Finite element models were used to obtain design guidelines for reliability and estimate critical regions of the 3D package during thermal cycling. Following the design guidelines from modelling, 6‘×6’ glass interposer panels of 100µm thickness were fabricated with TPVs. Vias were formed with 355nm UV laser at 60µm diameter. Test dies were assembled on both sides and connected with TPVs. Distance between the solder bump of test die and TPV was varied in order to assess its effect on reliability. Additionally, TPV daisy-chain coupons without dies were fabricated to investigate the reliability of UV laser drilled TPVs in free-standing glass. Test coupons were subjected to liquid-to-liquid thermal cycling test between 125°C and −40°C with 5 minutes dwell time at each temperature extremes. All TPV daisy-chains in free-standing glass and all double-side assembly coupons passed 1000 thermal cycles. Further thermal cycling up to 2000 thermal cycles resulted in failures related to solder bump-glass interposer connection. There were no failures in TPV chain in both free-standing and double-side die assembled test coupons as was predicted by simulations.