Since the Copper resistivity is second lowest next to the Silver, the Copper electrodeposits have been very intensively used in the wiring for the semiconductor and the printed circuit board (PCB). The Copper problem is the thermal coefficient of expansion (TCE). The Silicon is 2.6x10^-6 (1/K) and the copper is 17x10^-6 (1/K). If the composite of the Silicon and the Copper (semiconductor and PCB), warpage, protrusion or delamination occurs. Warpage, protrusion or delamination resolution by low TCE copper examples are reported.

Results

1. TSV no pumping at 450^oC. Crack and Copper extrusion occurs at bottom corner of conventional Copper TSV. No crack and no Copper extrusion occurs for our low TCE Copper (Fig.1).
2. No glass crack with 180^oCx1hr for the glass interposer.
3. The Copper wiring for the IGBT wafer shows half warpage and no warpage at 350^oC.
4. The coreless PCB warpage reduce to half.
5. No crack between the ceramics and the copper or Copper wire and IGBT chip in reliability test (Under examination).
6. No crack in via for via on via stacking for the buildup PCB (Under examination).

Reference

1. Q. Dinh and K. Kondo, ECS J. Solid State Sci. Technol., 6, P566–P569 (2017).