Abnormal ESD failure mechanism in high-pin-count BGA packaged ICs due to stressing nonconnected balls |
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Authors: | Wen-Yu Lo Ming-Dou Ker |
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Affiliation: | Mixed Signal Product Div., Silicon Integrated Syst. Corp., Hsinchu, Taiwan; |
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Abstract: | An abnormal failure mechanism due to ESD pulse applied on the nonconnected (NC) solder balls of a high-pin-count (683 balls) BGA packaged chipset IC is presented. The ESD test results of the IC product were found below human-body-model (HBM) 2 kV when stressing all balls or only stressing NC balls, but above HBM 3 kV when stressing all balls excluding NC balls. Failure analyses, including scanning electron microscopy (SEM) photographs and the measurement of current waveforms during ESD discharging event, have been performed. With a new proposed equivalent model, a clear explanation on this unusual phenomenon is found to have a high correlation to the small capacitor method (SCM). Several solutions to overcome this failure mechanism are also discussed. |
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