Summary
Package crack/void between non-connected terminals is a critical anomaly in plastic encapsulated parts. This is so as these can turn into a conductive path and lead to catastrophic failures. In this regard, Scanning Acoustic Microscopy (SAM) is the most effective non-destructive approach for the sensitive detection of such deviations within plastic packages. The present note shows the comprehensive inspection of a thick power transistor and the detection of this type of internal anomalies.
Sample & Method
The images show the confocal scanning acoustic microscopy (C-SAM) inspection of a power transistor specially designed for hard switching SMPS topologies. Similarly to other power transistors, the device features a thick plastic package (TO-263). Thus an appropriate transducer/frequency must be specifically selected for the comprehensive inspection of the systems and to reach the required quality and definition.
In such a thick package a multi-depth inspection approach is selected to confocally resolve micrometric cracks thanks to the C-Scan-mode of the acoustic microscope. This inspection process is conducted i.a.w. the acceptance/rejection criteria indicated in the applicable inspection methods (J-STD-020E, ESCC 25200, PEM-INST-001 & MIL-STD-1580).
Remarks
C-mode scanning acoustic microscopy discloses a rejectable crack that extends the whole length between at least two terminals. In this case, the image was optimized to register the crack.
The A-scan below shows clear phase inversion sings (right) that contrast with the normal-positive peak detected on a defect-free lead finger (left). Such a type of anomaly is considered a cause of rejection according to different test methods. This is so as the detected crack can open a conductive path between lead-frame-fingers designed to be isolated, which compromises the reliability and the suitable performance of the device.
Contact our team
In 2014 he started his career within the aerospace sector by as Quality Technician at the Incoming-Inspection Service. There he was involved in diverse testing activities and acquired specialized skills and experience in different inspection techniques, such as Radiographic inspection, Lead Material Verification and others.
In 2017, he joined the Destructive Physical Analysis Laboratory (DPA), where he performs physical test and comprehensive inspection on EEE parts by advanced characterization tools such as Confocal scanning Acoustic Microscopy.
- Crack detection within plastic packages by C-SAM - 28th April 2020
- Incoming Inspection Electronic Components | EEE Parts - 9th December 2015
