Failure Analysis of Open Circuit at Output Terminal of the Voltage Comparator

This paper explains the process of failure localization and mechanism analysis for a voltage comparator failure case. The output terminal of the voltage comparator is open circuit. The analysis adopted a series of analysis ideas such as non-destructive troubleshooting, internal positioning, and data statistical analysis. The material of the failure component bonding wire is aluminum. Aluminum corrosion products and external remainder particles led to virtual bonding of the bonding wire. The result of the non-destructive bond pull test showed a value of 0 grams. The debonding position was located in the external bonding area. The corrosion products contained C, O, Al and Cl. Aluminum corrosion of the output bonding wire was an internal failure phenomenon of the voltage comparator. Inspection revealed the movement trajectory of remainder particles. The corrosion location was in the external bonding area. There were similar remainder particles near the corrosion site. The remainder particles adhered to the ceramic. They extended towards the sealing ring position on the long side of the shell side wall. This was consistent with the suspicious hole location found during the appearance inspection. Conduct a profile analysis along the long edge of the leaking sealing ring. The grinding and polishing work was paused at the outer edge of the sealing ring. There was a hole between the metal sealing ring and the ceramic. There was no obvious tungsten layer at the position of the hole. When the grinding and polishing work progressed to a quarter of the width of the sealing ring, the holes decreased. At this point, the tungsten layer at the sealing ring position was discontinuous. The discontinuous position was nickel. When the grinding and polishing work progressed to about one-third of the width of the sealing ring, the holes disappeared. The tungsten layer presented a continuous state. There was the hole between the metal sealing ring and the ceramic substrate. The components needed to be cleaned after installation. During the cleaning process, soldering fluxes and cleaning agent entered through the holes. Ultimately, it led to aluminum corrosion. Repeated parallel seam welding leads to the formation of pores at the junction. The same batch of components had the same problem. And the rejection rate of unqualified sealing was much higher than other batches of the same model. This paper summarizes the research ideas and results. In future work, the feasibility of repeating parallel seam welding processes is worth pondering. This article can help manufacturers improve the robustness of device casings. At the same time, assist the manufacturer in formulating a reasonable range of sealing process parameters. Data statistical analysis methods should be widely applied in failure analysis. By comparing and analyzing different dimensions, it can identify the real potential problem. It can provide reference for similar failure analysis in the future.