Title :
Compliant bumps for adhesive flip chip assembly
Author :
Keswick, Kathryn ; German, Randy ; Breen, Mark ; Nolan, Rick
Author_Institution :
MCC, Austin, TX, USA
Abstract :
Flip-chip-on-glass (FCOG) is susceptible to electrical opens for a variety of reasons including, but not limited to, movement in the z-axis caused by flip chip adhesive CTE and water absorption of the adhesive. Flip chip assembly to cofired ceramic and laminate substrates suffers from these problems as well as others, such as bow or twist in the substrate and bond pad height irregularities. Success with adhesive flip chip connections to these substrates has, to date, been limited. Commercially available adhesives have either failed to produce reliable bonds, or have suffered from long cure time or a lack of reworkability. A solution to these problems has been demonstrated by forming compliant bumps on the chip or substrate bond pads using a photoimagible polymer coated with a thin layer of gold. Bumps 17 μm tall with diameters between 17 μm and 95 μm have been fabricated and bonded. The resulting compliant bump structure provides 30% of the bump height (5 μm) within the elastic compression range. This compliance eliminates many of the demands placed on the assembly adhesives by other electrical contacting methods (such as solid metal bumps or particles). Compliant bumps allow the use of commercially available, fast curing, easily reworkable adhesives for reliable flip chip assembly
Keywords :
adhesion; flip-chip devices; integrated circuit interconnections; integrated circuit packaging; integrated circuit reliability; lead bonding; 17 to 95 micron; adhesive flip chip assembly; bond pad height irregularities; bow; ceramic substrates; compliant bumps; curing; elastic compression range; electrical opens; flip chip adhesive CTE; flip-chip-on-glass; laminate substrates; photoimagible polymer; reworkable adhesives; twist; water absorption; Absorption; Assembly; Bonding; Ceramics; Contacts; Flip chip; Gold; Laminates; Polymer films; Solids;
Conference_Titel :
Electronic Components and Technology Conference, 1994. Proceedings., 44th
Conference_Location :
Washington, DC
Print_ISBN :
0-7803-0914-6
DOI :
10.1109/ECTC.1994.367659