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The Mechanism of the Die Crack in Exposed Pad Quad Flat Package (ePad QFP) with Large Die due to Die-Attach Adhesive with High Modulus
Keywords: Die attach adhesive, CTE, Die crack
Thermal-enhanced plastic packages, such as exposed Pad Qual Flat Package (ePAD QFP), are more sensitive to thermal stress and warpage. As a result, thermal stress and waprage in ePAD QFP can lead to severe die cracking. This stress and warpage are mainly due to the thermal mismatch of packaging materials with different coefficients of thermal expansion (CTE). In particular, the die attach adhesive plays an important role in controlling stress and warpage in the package. In this paper, both experimental data and simulation were employed to gain a better understanding in a stress development and failure mechanism in ePAD QFP with a large die. Two different die-attach adhesives with different modulus were used for the evaluation of die crack and delamination. And the effect of the adhesion between Si die and Die-attach adhesive on the die crack was also discussed in this paper. The simulation for thermal stress due to CTE mismatch was done by shadow moiré measurement technique and dynamic profiling method to verify the stress concentration area around the die in the package. And the delamination and die crack were simulated by thermal cycling test after changing different packaging process parameters that can directly affect on the die crack and the adhesion. The mechanism of die crack and the crack propagation through the die were mainly discussed in details at first and then the stress concentration and die crack initiation was verified by thermal simulation test and experimental test. In addition, the major property of the die-attach adhesive to be considered for better reliability performance in ePAD QFP was suggested.
Dong-Nam Kim,
TLi Inc.
Seongnam-si, Gyeonggi-do 463-828,
South Korea

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