Experimental Characterization of Monotonic and Fatigue Delamination of Novel Underfill Materials

[+] Author and Article Information
Saketh Mahalingam, Kunal Goray

 General Electric Global Research Center, Bangalore, India, 560066

Sandeep Tonapi

 General Electric Global Research Center, Niskayuna, NY 12309

Suresh K. Sitaraman1

Computer Aided Simulation of Packaging Reliability (CASPaR) Lab, G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405suresh.sitaraman@me.gatech.edu


Corresponding author.

J. Electron. Packag 128(4), 405-411 (Oct 04, 2006) (7 pages) doi:10.1115/1.2386242 History: Received July 25, 2005; Revised October 04, 2006

No-flow underfill materials reduce assembly processing steps and can potentially be used in fine-pitch flip chip on organic board assemblies. Such no-flow underfills, when filled with nano-scale fillers, can significantly enhance the solder bump reliability, if the underfills do not prematurely delaminate or crack. Therefore, it is necessary to understand the risk of underfill delamination during assembly and during further thermal excursions. In this paper, the interface between silicon nitride (SiN) passivation and a nano-filled underfill (NFU) material is characterized under monotonic as well as thermo-mechanical fatigue loading, and fracture parameters have been obtained from such experimental characterization. The passivation-underfill interfacial delamination propagation under monotonic loading has been studied through a fixtureless residual stress induced decohesion (RSID) test. The propagation of interfacial delamination under thermo-mechanical fatigue loading has been studied using sandwiched assemblies and a model for delamination propagation has been developed. The characterization results obtained from this work can be used to assess the delamination propagation in flip-chip assemblies. Though the methods presented in this paper have been applied to nano-filled, no-flow underfill materials, their application is not limited to such materials or material interfaces.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Residual stress induced decohesion test

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Figure 2

Residual stress test setup

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Figure 3

RSID test—plot of displacement versus temperature

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Figure 4

Residual stress induced decohesion

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Figure 5

Finite element model of the RSID test

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Figure 6

Temperature dependent CTE of the NFU material

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Figure 7

Temperature dependent modulus of the NFU material

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Figure 8

Fatigue test specimen

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Figure 9

Progress of interfacial delamination observed using CSAM

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Figure 10

Optically visible interfacial delamination. (a) Sample when oriented parallel to view. (b) Sample when tilted under microscope.

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Figure 11

Finite element model of the fatigue test specimen

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Figure 12

Comparison between finite element solution and analytical solution

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Figure 13

Rate of crack propagation

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Figure 14

Paris law for underfill delamination



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