Browse Prior Art Database

REWORKABLE ENCAPSULANT-FREE FLIP CHIP ASSEMBLY

IP.com Disclosure Number: IPCOM000008982D
Original Publication Date: 1999-Jan-01
Included in the Prior Art Database: 2002-Jul-29
Document File: 2 page(s) / 107K

Publishing Venue

Motorola

Related People

Gregory Dunn: AUTHOR [+2]

Abstract

Current flip chip assemblies require encapsulant material for enhanced reliability performance. Encapsulant is used to couple the die mechanically to the substrate to constrain the board during ther- mal excursions and to reduce the stress transferred to the solder joints. Underfilling the die with encap- sulant requires additional equipment such as dis- pensing robots and curing ovens. In addition, typical encapsulant materials absorb approximately 0.6 wt% moisture which affects adhesion properties and can lead to "popcorn" type failures when a flip chip ball grid array package is attached to the mother board. Finally, the use of encapsulant precludes easy removal of the die (rework).

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Technical Developments

REWORKABLE ENCAPSULANT-FREE

FLIP CHIP ASSEMBLY

by Gregory Dunn and Daniel Gamota

PROBLEM

  Current flip chip assemblies require encapsulant material for enhanced reliability performance. Encapsulant is used to couple the die mechanically to the substrate to constrain the board during ther- mal excursions and to reduce the stress transferred to the solder joints. Underfilling the die with encap- sulant requires additional equipment such as dis- pensing robots and curing ovens. In addition, typical encapsulant materials absorb approximately 0.6 wt% moisture which affects adhesion properties and can lead to "popcorn" type failures when a flip chip ball grid array package is attached to the mother board. Finally, the use of encapsulant precludes easy removal of the die (rework).

SOLUTION

  In lieu of encapsulant, a ceramic component configured as a collar or frame around the flip chip is affixed to the printed wiring board or package interposer by a combination of solder joints (at the required electrical contacts) and adhesive. The ceramic component may be a multilayer ceramic decoupling capacitor, providing a local source of charge to the die during switching, or a multilayer ceramic integrated circuit comprising multiple pas- sive elements such as capacitors and inductors.

BENEFITS

  The ceramic collar mechanically constrains the organic board or interposer and reduces the stresses generated and transferred to the die during thermal cyc...