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Belfort Y.,Failure Analysis Laboratory and Technology Validation | Caignard J.-M.,Failure Analysis Laboratory and Technology Validation | Keller S.,Failure Analysis Laboratory and Technology Validation | Guerveno J.-P.,Failure Analysis Laboratory and Technology Validation
Microelectronics Reliability | Year: 2015

This failure analysis concerns a commercial DC-DC module assembled on board, which the OP-AMP servo stage is failed. The electrical failure is an intermittent open circuit on the pins of the OP-AMP. When the board is powered ON, the open circuit generates a malfunction of the servo stage and leads either, to an overvoltage on the module output, or to one input destruction by electrical over stress (EOS). The failed OP-AMPs have copper wire bonding unlike the previous versions which never failed and had gold one. OP-AMPs with copper wire bonding, had populations with defects and without. The investigations and the failure mechanism study showed that the open circuits observed on the OP-AMP were due to a galvanic corrosion of the bonding/die interface at intermetallic level. To obtain this failure mechanism, it's necessary to have the combination of temperature, humidity and pressure. The specificity of the module technology allows having the conditions for the combination of these three factors. The trigger element is a high temperature storage performed at a step of manufacturing flow to avoid damage on components with high moisture sensibility level (MSL). The failure analysis allowed to identify and to reproduce the defect observed on OP-AMPs. © 2015 Elsevier Ltd. Source

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