Failure Analysis of Abnormal Input Voltage in Error AMP Part of the PWM Controller

This paper explains the process of failure localization and mechanism analysis for a pulse width modulator failure case. The input voltage of the error amplification part of the pulse width modulator is zero. The input terminal has low resistance to ground. The failure phenomenon is unstable. It will change with changes in temperature, vibration, and other factors. Under certain conditions, the failure can recur. The analysis adopts a series of analysis ideas such as non-destructive troubleshooting, internal positioning, and replication verification. The collapse and deformation of the input bonding wires is an internal failure phenomenon of the PWM Controller. It connects the metallized edges of the chip. The metallization in this area is not covered by the passivation layer. This leads to a short circuit between the input and ground. The thermal expansion and contraction of the collapsed bonding wires during temperature cycling can lead to the unstable failure. And the movement of the bonding wires position during vibration can also lead to the unstable failure. This paper summarizes the research ideas and results. Especially the continuous and repeated adjustment of ideas can provide a reference for the subsequent failure analysis of similar and unstable failure.