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Compensation of Thermal Expansiveness In Plastic DCA-Flip-Chip Assemblies Using A Mechanically Compliant Dielectric

Published

Author(s)

Jan Obrzut

Abstract

Application of a compliant, low modulus dielectric layer between the chip joints (C4) and the carrier can decrease the thermally induced bending and probability of failure. Model analysis and experimental data indicate that the optimal thickness of the decoupling layer ranges from 3 to 2 of the C4underfil gap. The desirable range of the Young's Modulus is between 108 N/m2 to 3 108 N/m2. To verify these predictions we have investigated thermally induced deformation in assembled plastic FCBGA chip carriers. The compliant, decoupling layer was made of a photoimageable, interpenetrating network of polymer dielectric. According to the experimental data, the relative bending of the assembled packages with the compliant layer is smaller than that of the conventional laminate at all temperatures, and approaches zero at about 110 {degrees} C. At this temperature the interpenetrating polymer network is in its semirubbery state, and therefore, it can simultaneously conform to different thermal expansion rates of the chip end the laminate carrier. This decouples the chip expansion from that of the carrier, which minimize the warping of the assembly at temperatures well below the glass transition of the laminate.The results of the dielectric and mechanical evaluation were verified by executing a series of standard reliability tests. We have determined that FlipChip assemblies with the compliant dielectric layer can satisfy the standard reliability requirements, and that the construction is suitable for a variety of packaging configurations including the chip scale packaging.
Conference Dates
March 12-14, 1999
Conference Location
Braselton, GA
Conference Title
IMAPS International Advanced Technology Workshop on Flip Chip Technology

Keywords

flip-chip technology, microvias, organic chip carriers, polymer dielectrics

Citation

Obrzut, J. (1999), Compensation of Thermal Expansiveness In Plastic DCA-Flip-Chip Assemblies Using A Mechanically Compliant Dielectric, IMAPS International Advanced Technology Workshop on Flip Chip Technology, Braselton, GA, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851554 (Accessed April 19, 2024)
Created May 3, 1999, Updated February 19, 2017