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This paper presents the assembly optimization and characterization of through-silicon vias (TSV) interposer technology for two 8 Ã 10mm2 micro-bumped chips. The two micro-bumped chips represent different functional dies in a system-in-package (SiP). In the final test vehicle, one of the micro-bumped chips had 100Â¿m bump pitch and 1,124 I/O; the other micro-bumped chip had 50Â¿m bump pitch and 13,413 I/O. The TSV interposer size is 25 Ã 25 Ã 0.3mm3 with CuNiAu as UBM on the top side and SnAgCu bumps on the underside. The conventional substrate size is 45 Ã 45mm2 with 1-2-1 layer configuration, a ball-grid array (BGA) of 1mm pitch and a core thickness of 0.8mm. The final test vehicle was subjected to MSL3 and TC reliability assessment. The objective of this paper was to incorporate two 8 Ã 10mm2 micro-bumped chips into TSV interposer. The micro-bumped chips should have no underfill voiding issue and the whole package should be able to pass moisture sensitivity level 3 (MSL3) and thermal cycling (TC) reliability assessment. To achieve this objective of incorporating micro-bumped chips into the TSV interposer, the challenges were small standoff height/ low bump pitch of the micro-bumped chip, underfill flowability and its reliability performance. To overcome these challenges, different types of capillary flow underfill, bump layout designs and bump types were evaluated and a quick reliability assessment was used to select the materials and test vehicle parameters for final assembly and reliability assessment.