NDLI: A new approach to using anisotropically conductive adhesives for flip chip assembly

Content Provider	IEEE Xplore Digital Library
Author	Lyons, A.M. Hall, E.E. Yiu-Huen Wong Adams, G.
Copyright Year	1995
Description	Author affiliation: AT&T Bell Labs., Murray Hill, NJ, USA (Lyons, A.M.; Hall, E.E.; Yiu-Huen Wong; Adams, G.)
Abstract	The use of anisotropically conductive adhesives (ACAs) for the direct interconnection of silicon chips to printed circuits offers numerous advantages including: reduced package thickness, improved environmental compatibility, lowered assembly temperatures, increased metallization options, and decreased equipment needs. To increase throughput and to lower costs, we have developed a new approach to flip-chip assembly with ACAs. Our process uses two unique features: an ACA thixotropic paste formulation and a batch curing fixture. The thixotropic paste, which replaces the more conventional film form of the adhesive, can be easily dispensed onto the substrate with a stencil printer. Chips placed into the ACA paste are held securely due to the "tacky" nature of the material much like surface mount components are held by solder pastes. As a result, no heating of the chips is required during assembly, increasing throughput and relaxing co-planarity tolerances in the alignment equipment. As with all ACAs, the paste must be cured by the simultaneous application of heat and pressure. In our process, curing is accomplished in a fixture capable of holding multiple chips and/or circuit boards simultaneously. Uniform pressure is applied to components during the 3-5 minute thermal cure cycle via a conformable silicone rubber bladder. Initial yield and temperature cycling data are reported in this paper. Silicon chips with gold metallization show small (<15%) increases in contact resistance after more than 1000 test cycles (between 0-100/spl deg/C); bumping the chips was not required. Aluminum metallized chips proved to be unreliable after temperature cycling tests.
Starting Page	107
Ending Page	113
File Size	1542203
Page Count	7
File Format	PDF
ISBN	0780327365
DOI	10.1109/ECTC.1995.514369
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	1995-05-21
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Anisotropic magnetoresistance Conductive adhesives Assembly Temperature Metallization Silicon Printed circuits Throughput Curing Fixtures
Content Type	Text
Resource Type	Article

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