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64 SMT007 MAGAZINE I SEPTEMBER 2023 Feature Interview by Nolan Johnson I-CONNECT007 e practical question around CHIPS Act development and electronics assembly is, "Will this change how we do business?" Indium Corporation's Dr. Andy Mackie sat down with Nolan Johnson to share what he sees as emerg- ing answers to that question from his perspec- tive as an expert in electronics assembly and packaging, and as a participant in standards development through IPC, JEDEC, and SEMI. When we talk about the CHIPS Act, that leads to a discussion about the assembly process, as they seem so interrelated. Certainly. As the CHIPS Act money started rolling out last year, IPC hosted a conference in Washington, D.C. to point out that semicon- ductor chips do not exist in a vacuum; they are part of an electronics ecosystem that includes interconnection and protection. erefore, U.S.-based packaging and assembly would be needed, alongside U.S. chip fabrication. is appeared to be news to many. e role of solder in advanced packaging has been changing over the years, but solder will continue to be needed. Take first level interconnect (FLI) flip-chip solder, which has been around for a long time as solder bumps, then bumped copper pillars, and has reached the end of its run for really advanced assemblies. But at what point (pitch) that happens depends on who you talk to, and engineers are notorious for sticking to what they know works. Five years ago, Intel was predicting the end of FLI solder at 20-micron pitch. However, when putting silicon die on a silicon interposer, there's no CTE mismatch between the chip and the substrate, so ther- mal cycling stresses are much less of a concern. Obviously, that lower silicon is bonded and electrically interconnected to something— probably organic in the near term—so there are CTE mismatches at that lower level. Note that 10-micron pitch flip-chip solder has been used by TSMC several years now for silicon on silicon.

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