Metallic strain-absorbing layer for improved fatigue resistance of solder-attached devices
AssigneeTexas Instrument Incorporated
InventorJohn P. Tellkamp
Life of this patent
Estimating the term…
Abstract
An integrated circuit chip 501 has a plurality of contact pads (FIG. 5B) to be connected by reflow attachment 510 to outside parts. The chip comprises a deposited layer 505 of 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 layer 506 of solderable metal is on the alloy, operable as diffusion barrier after reflow attachment.
Claims24
An integrated circuit chip having a plurality of contact pads to be connected by reflow attachment to outside parts, comprising:
- a deposited layer of nickel/titanium alloy on each of said pads, said alloy having a composition and crystalline structure operable in reversible phase transitions under thermomechanical stress, whereby mechanical strain is absorbed by said alloy layer;
- and
- a layer of solderable metal on said alloy, operable as diffusion barrier after said reflow attachment.
A metallurgical interconnection attaching an electronic device having first coefficient of thermal expansion to an outside body having second coefficient of thermal expansion, comprising:
- an electronic device having a plurality of contact pads exposing the device metallization;
- each of said contact pads having a layer of nickel/titanium alloy deposited over said device metallization, followed by a solderable nickel barrier layer;
- a solder bump attached to said solderable layer of each contact pad;
- said outside body having a plurality of terminal pads located in positions respective to said device contact pads, said terminals exposing the metallization of said outside body;
- said device attached to said outside body so that said contact pads are aligned with said respective terminal pads, whereby a plurality of metallurgical interconnections are formed operable to absorb, in said nickel/titanium
- layer, strain caused by thermomechanical stress due to the difference between said first and second coefficients of thermal expansion.
A metallurgical interconnection attaching an outside body having first coefficient of thermal expansion to an electronic device having second coefficient of thermal expansion, comprising:
- an outside body having a plurality of terminal pads exposing the body metallization;
- each of said terminal pads having a layer of nickel/titanium alloy deposited over said body metallization, followed by a solderable barrier layer;
- a solder bump attached to said solderable layer of each terminal pad;
- said electronic device having a plurality of contact pads located in positions respective to said body terminal pads, said contacts exposing the metallization of said device;
- said device attached to said outside body so that said contact pads are aligned with said respective terminal pads, whereby a plurality of metallurgical interconnections are formed operable to absorb, in said nickel/titanium layer, strain caused by thermomechanical stress due to the difference between said first and second coefficients of thermal expansion.
An integrated circuit device including a plurality of contact pads, comprising:
- a layer of nickel/titanium alloy on each of said pads, said alloy having a composition of between about 55.5 and about 56.5 weight % nickel and between about 43.5 and about 44.5 weight % titanium;
- and
- a layer of solderable metal over said alloy.
Dependencies are inferred from the claim text.