Flip chip is the emerging interconnect technology for the next generation of high performance electronics. To eliminate the process bottlenecks associated with flip chip assembly, a new assembly technique based around “No-flow” underfill formulations has been proposed. In this paper, we have studied the correlation between the mechanical strength and the curing condition of no-flow flip chip assemblies using six different reflow profiles. It is found that both and intermetallics (IMCs) are formed at the solder/substrate pad and UBM (Under Bump Metallization)/solder interfaces respectively. The thickness of both IMCs increase with the increasing heating factor. The characteristics of the mechanical strength of these IMCs have been demonstrated. A correlation between the mechanical strength and the interfacial metallurgical reaction has been discussed. Also, the fastest possible reflow profile for both the cure of the underfill and maximizing the shear strength is identified. Based on the observed relationship of the mechanical strength and underfill curing of no-flow flip chip assemblies with the reflow profile should be controlled with caution in order to optimize both the mechanical strength and time for underfill cure. Only a clearer understanding of these correlation can allow manufacturers to develop a optimal, high reliable, low cost, high throughput no-flow flip chip assembly process.
Correlation Between the Mechanical Strength and Curing Condition of No-Flow Flip Chip Assemblies
Contributed by the Electronic and Photonic Packaging Division for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received by the EPPD Division, October 15, 2000; revised manuscript received October 18, 2001. Associate Editor: M. Shiratori.
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Tang , C. W., Chan , Y. C., Hung , K. C., and Tu, P. L. (December 12, 2002). "Correlation Between the Mechanical Strength and Curing Condition of No-Flow Flip Chip Assemblies ." ASME. J. Electron. Packag. December 2002; 124(4): 397–402. https://doi.org/10.1115/1.1510865
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