Metallic strain-absorbing layer for improved fatigue...

Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Ball or nail head type contact – lead – or bond

Reexamination Certificate

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C257S779000, C257S764000, C438S614000

Reexamination Certificate

active

07095121

ABSTRACT:
An integrated circuit chip 501 has a plurality of contact pads (FIG.5B) to be connected by reflow attachment510to outside parts. The chip comprises a deposited layer505of nickel/titanium alloy on each of the pads; the alloy has a composition and crystalline structure operable in reversible phase transitions under thermomechanical stress, whereby mechanical strain is absorbed by the alloy layer. Preferably, the alloy has between 55.0 and 56.0 weight % nickel, between 44.0 and 45.0 weight % titanium, and a thickness in the range from 0.3 to 6.0 μm, recrystallized after deposition in a temperature range from 450 to 600° C. for a time period between 4 and 6 min. A layer506of solderable metal is on the alloy, operable as diffusion barrier after reflow attachment.

REFERENCES:
patent: 6255723 (2001-07-01), Light et al.
patent: 6489229 (2002-12-01), Sheridan et al.
patent: 0 753 990 (1997-01-01), None
patent: 01 081264 (1989-03-01), None
patent: 09 129647 (1997-05-01), None
patent: 2001 024021 (2001-01-01), None
“Biocompatibilty Evaluation of Nickel-titanium Shape Memory Metal Alloy”, Jorma Ryhanen, 1999, Oulu University Library, Oulu, Finland.
“Effect of Thermomechanical Treatment on the Two-way Shape Memory Effect of NITI Alloy Spring”, Zhiguo Wang et al, Materials Letters, North Holland Publishing Company, Amsterdam, NL, vol. 54. No. 1 May 2002, pp. 55-61.

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