Reworkable Edgebond Applied Wafer-Level Chip-Scale Package

Tae-Kyu Lee, Ph.D.
Portland State University
Portland, OR, USA

Kola Akinade, Ph.D., Cherif Guirgis, Weidong Xie, and Steven Perng, Ph.D.
Cisco Systems
San Jose, CA, USA

Edward Ibe and Karl Loh
Zymet
East Hanover, NJ, USA

This paper presents data showing that localized distribution of recrystallized grains is an accurate indicator of solder joint life-cycle degradation and enhancement. Monitoring the distribution is proposed as a new analytical approach. The correlation between an elevated temperature environment and thermal cycling induced crack propagation, in a series of cross section analyses, on reworkable edgebond material applied wafer level chip scale package (WLCSP) components was conducted. The printed circuit board was designed to provide elevated temperature during thermal cycling by an embedded heating element inside the PCB. The localized heating of the WLCSP, to simulate an active component, degrades life cycles due to a higher creep rate, which negatively impacted the crack propagation. The application of a reworkable edgebond material enhanced thermal cycling fatigue performance.

Use of a reworkable edgebond adhesive enhanced life cycles for both normal temperature and elevated temperature thermal cycling. Monitoring local distribution of recrystallized grains is a promising approach to collecting predictive lifecycle data. This paper will discuss the overall performance of the reworkable edgebond, which provided a good stability enhancement to the WLCSP structure under thermal cycling at elevated temperature environment.

This paper presents data showing that localized distribution of recrystallized grains is an accurate indicator of solder joint life-cycle degradation and enhancement. Monitoring the distribution is proposed as a new analytical approach. The correlation between an elevated temperature environment and thermal cycling induced crack propagation, in a series of cross section analyses, on reworkable edgebond material applied wafer level chip scale package (WLCSP) components was conducted. The printed circuit board was designed to provide elevated temperature during thermal cycling by an embedded heating element inside the PCB. The localized heating of the WLCSP, to simulate an active component, degrades life-cycle due to a higher creep rate. This higher creep rate negatively impacted the crack propagation. The application of a reworkable edgebond material enhanced thermal cycling fatigue performance. The edgebond material provide stability at the edge row and shift the deformation and damage accumulation location into the component interior located solder joint. The damage accumulation indications via grain refinement observation tell us that where the defect accumulation and deformation occurred. Monitoring local distribution of recrystallized grains is a promising approach to collecting predictive life-cycle data.