Optimization of the Substrate Preheat Temperature for the Encapsulation of Flip Chip Devices

Category: Flip Chip and Die Placement
Post Date: July 19, 2004
Author(s): K. Srihari, Ph.D., and C-Y. Huang, Ph.D. State University of New York at Binghamton; and Peter Borgesen, Surface Mount Laboratory, Universal Instruments

Description
Flip Chip On Board (FCOB) technology involves the bonding of bare die directly onto a Printed Circuit Board (PCB). The interconnections are provided by solder bumps which are arranged in the area under the chip. Encapsulation is the preferred strategy used to reduce the impact of the thermal stress that results from the mismatch in the Coefficient of Thermal Expansion (CTE) between the silicon chip and the substrate. The length of time needed for the dispensing and capillary flow of the encapsulant is one of the important factors that inhibits the high volume use of FCOB technology. Pre-heating the substrate prior to and during the dispensing of the encapsulant enhances its flow characteristics by reducing its viscosity.

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