Formation of pure silver (Ag) flip-chip interconnect of silicon (Si) chips on copper (Cu) substrates is reported. Arrays of Ag columns, each 36 μm in height and 40 μm in diameter, are fabricated on 2-in. Si wafers which are first coated with chromium (Cr)/gold (Au) dual layers. The Si wafers are diced into 6 mm × 6 mm chips, each having 50 × 50 Ag columns. The Si chip with Ag columns is directly bonded to Cu substrate at 260 °C in 80 mTorr vacuum to inhibit oxidation. The static bonding pressure is as low as 680 psi (4.69 MPa), corresponding to a load of 0.021 oz (0.60 g) per column. During bonding, the Ag columns deform and conform to the Cu substrate. They are well bonded to the Cu. No molten phase is involved in the bonding process. The joints consist of pure Ag only. The ductile Ag joints are able to accommodate the thermal expansion mismatch between Si and Cu. It is well known that in nearly all soldering processes used in electronic industries, intermetallic compound (IMC) formation is essential to make a solder joint. In the pure Ag interconnect, no IMCs exist. Thus, reliability issues associated with IMCs are eliminated. Compared to tin-based lead-free solders, pure Ag joints have superior electrical and thermal properties.
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September 2011
Research Papers
40 μm Silver Flip-Chip Interconnect Technology With Solid-State Bonding
Chu-Hsuan Sha,
Chu-Hsuan Sha
Electrical Engineering and Computer Science, Materials and Manufacturing Technology,
University of California – Irvine
, Irvine, CA 92697-2660
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Chin C. Lee
Chin C. Lee
Electrical Engineering and Computer Science, Materials and Manufacturing Technology,
University of California – Irvine
, Irvine, CA 92697-2660
Search for other works by this author on:
Chu-Hsuan Sha
Electrical Engineering and Computer Science, Materials and Manufacturing Technology,
University of California – Irvine
, Irvine, CA 92697-2660
Chin C. Lee
Electrical Engineering and Computer Science, Materials and Manufacturing Technology,
University of California – Irvine
, Irvine, CA 92697-2660J. Electron. Packag. Sep 2011, 133(3): 031012 (4 pages)
Published Online: September 30, 2011
Article history
Received:
January 27, 2011
Revised:
June 13, 2011
Online:
September 30, 2011
Published:
September 30, 2011
Citation
Sha, C., and Lee, C. C. (September 30, 2011). "40 μm Silver Flip-Chip Interconnect Technology With Solid-State Bonding." ASME. J. Electron. Packag. September 2011; 133(3): 031012. https://doi.org/10.1115/1.4004660
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