Overcoming Assembly Process Challenges in Glass Interposer: Development of Jigs and Fixtures

This paper focuses on the singulation and extraction of multiple dies of different sizes and orientations from a glass wafer. We developed a 6" glass wafer consisting of Optics, Processor and interposer dies together for a Co-Packaged Optics and Processor heterogeneous package. The purpose of the work is to fabricate dies for process development. The wafer has two-sided metallization and passivation with Through Glass Vias. Due to the limitations imposed by the glass-copper mismatch in the vias, the wafer thickness is selected as 150um. Due to the brittle nature of glass, singulating the dies is a challenge as we need to apply as little force as possible. To maximize the yield, the dies are arranged in an asymmetrical pattern while the interpose has an irregular surface contour causing problems for machine dicing. Hence, manual singulation is selected. We designed and fabricated vacuum jigs and stencils for use with a diamond cutter and scribe. The vacuum pressure was calibrated and optimized for freezing the wafer within the jig and stencils with different thicknesses were fabricated to match the diamond cut blade. Another complexity is that the chips have different dimensions, orientations, bump pitch and pad sizes making the stencil design complex. The metrology report of the diced chips is presented in terms of tolerance check with the actual one, and the edged chips deviation is found. The diced chipsets are then transferred to a vacuum-based Solder Dispensing Jig setup. The impact of accurate and precise dicing and solder dispensing impacts the next steps of the assembly line. The solder material selection for variable bump size and pitch of the chips, as well as the definition and optimization of the reflow line setup for high-temperature solder (HTS) and low-temperature solder (LTS) will be the subject of next paper.