The effect of a heat spreader on the life of the solder joints for underfill-encapsulated, flip-chip packages is investigated through stress analyses and thermal cycling tests. An underfill with suitable mechanical properties is found to be able to prolong the fatigue life of the solder joints even in a package with a heat spreader and an alumina substrate. The delamination of the underfill from the chip is revealed as another critical failure mode for which the shape of the underfill fillet has a large effect.

The interconnection reliability of a contact-joint structure with anisotropic conductive film (ACF) or non-conductive film (NCF) was evaluated in terms of stability of the compressive force at the contact face between a chip bump and a substrate pad. The key factor that dominates the interconnection reliability during temperature cycling is the amount of plastic strain in the chip bump (gold bump) at the contact face. The plastic deformation of the chip bump must therefore be controlled by selecting the appropriate mechanical properties of the adhesive film (ACF or NCF) and the build-up substrate material. Moreover, the interconnection reliability during moisture-resistance tests deteriorates because of stress relaxation near the glass-transition temperature of the commonly used build-up material. It is therefore concluded that a new material system, which includes the mechanical property of the build-up material for preventing stress relaxation, should be developed

Silicone gel is usually applied to electrical automotive devices to protect them from corrosion. However, under a vibration environment, the silicone gel vibrates bonding wires in the devices, thus, to evaluate the reliability of the devices, the vibration analysis of the gel/wire structure is indispensable. In this study, we clarify the relation between

In recent years, the decrease in fatigue life of solder joints at high temperatures has been a major problem in semiconductor packages for automotive applications. In this paper, to improve the accuracy of predicting the fatigue life of solder joints when considering high-temperature degradation, we studied the correlation between high-temperature holding conditions and the decrease in fatigue life by using the mechanical fatigue test results of solder joints after high-temperature holding. The decrease in the fatigue life of solder joints after high-temperature holding was explained by the change in the fatigue ductility coefficient of Coffin-Manson's law, and this fatigue life decrease can be quantitatively estimated using Arrhenius' law with the holding time and holding temperature. We found that the fatigue life predicted by Miner's law using the fatigue ductility coefficient under the test conditions of thermal cyclic tests agreed well with the experimental results.

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