POWER GOLD FOR 175°C Tj-maxAuthors: James J. Wang and Bob Baird
Company: Motorola, Inc.
Date Published: 2/18/2003 Conference: Pan Pacific Symposium
Top silicon metallization and wire bond pads are gold. Gold process integrates with wafer flow having aluminum interconnect layers underneath the top Power Au layer. Thick Power Au carries current, minimizes electromigration through thinner aluminum bus and provides an oxide free pad for Au wire bonding. Both Au ball bonding speed and ball shear strength improve with gold bond pads over conventional aluminum bond pads.
Gold to gold wire joints are impervious to halides and do not corrode at high temperature. Rough gold surface adheres to mold compounds and survives MSL1 preconditioning and autoclave without delamination over die surface. Power Au allows SMARTMOS. product to survive 4000 hours of high temperature bake at 190°C and 1500 cycles of air to air temperature cycling from -65°C to 175°C.
Although only few selected packages are tested, results suggest Power Au is compatible to standard molded packages. Package Theta-jc remains same; nevertheless, power capability increases when silicon junctions operate at 175°C. Circuit boards also dissipate more power. Power Au cost for 8" wafers is comparable to one layer of aluminum plus ILD. Introduction of Power Au onto ICs improves power plus reliability of packaging.
Key words: power gold, power IC, Tjmax, 175C, Au-Au bond.
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