Early. Plastic Power Transistor Failure Data Analysis And Countermeasures

Plastic encapsulated power bipolar transistors are used widely in Electronic Ballasts, Electronic Transformers, Switch Power Supplies and charger etc., and they are the key devices in these applications. Plastic encapsulated power bipolar transistors often have problems with reliability which are intrinsic to the structure and the packaging style. It is therefore necessary to study the causes and the mechanism of failures of the device in order to provide guidance for the production to improve the technology, quality and reliability of the product.In this paper, the causes of reliability problems have been analyzed with the help of MINITAB statistical software. It has been found that defects such as package defects, adhesion defects, thermal stress caused by temperature variation, and erosion by humidity intrusion are critical to early failures of devices. Case studies of failure mechanism are done for the prevention of occurrence of failures. The cases include foreign matter failure, chip adhesion failure and thermal stress failure, etc. The failure causes of the plastic encapsulated power bipolar transistors in the warehouse as is are sorted and analyzed. The main course of analyzing is as follows:1. Simply introduce the production process;2. Test the normal parameters of the devices in the warehouse categorized according to the storage time, and analyze the status in quo;3. Test the voltage curve with curve tracers;4. Check the devices nondestructively with X-RAY and C-SAM etc., and analyze the failure cause glance;5. Check the devices destructively with HTS and PCT, and analyze the failure cause in detail;6. De-cap the failed samples;7. Discuss the cause of early failure in the course of encapsulation, including the raw and processed materials of lead frame and plastic; die bonding and wire bonding parameter; delay time before encapsulating; the style of wiping off the spill; water in the devices; 8. Discuss the cause of early failure in the course of chip fabrication, including the raw and processed materials of wafer and the polishing reagent etc.; the disfigurements of small hole/Al speckle/row/etching; the process parameter of passivation and polishing; the voltage value of the device; the location of the die in the wafer; the pollution from the wafer, and so on;9. Discuss the cause of early failure in the course of the design, focusing on the influence of the inner diode;10. Propose projects to improve the reliability of the plastic encapsulated power bipolar transistor according to the analysis of failure causes;11. Produce following improved process, and do comparison analysis.The real data is analyzed with statistic approach in this paper; the situation of "data vacuum" and prevalence of "subjective judgments" is resolved to a large extent through the work. A flat roof to improve the quality of our production is provided.