Transducer And System Dependency Of Scanning Acoustic Microscope Images For Plastic Encapsulated MicroelectronicsAuthor: Stephen C. Hwang
Company: Sandia National Laboratories
Date Published: 10/13/2013 Conference: SMTA International
In the process of developing SAM contractor specifications, we have imaged selected PEMS components with SAM systems made by two different manufacturers. They are AD795 Si operational amplifiers and MMBT2222 NPN and MMBT2907 PNP Si bipolar transistors. Both SAM manufacturers use the same 15, 25, 30, 35, 50, and 75 MHz frequency ultrasonic transducers. With either system, the SAM reflection images for the same PEMs part and the same transducer are quite similar, but the delamination information produced by each system is different. Our studies indicate that the machine delamination information given by the built-in-phase inversion algorithms is system, transducer, and operator dependent. Thus, the delamination information given by the built-in-phase inversion algorithms requires careful interpretation to avoid either false positives or negatives. An experienced in-house SAM evaluation may be necessary to verify delaminations reported by an outside testing laboratory and any recommendation for a follow-up cross-section of the imaged parts.
For now, we consider SAM as a secondary tool during characterization and reliability test processes. No reject and accept criteria for a PEMs packaged part exists other than IPC/JEDEC J-STD-020A1. Delamination is frequently observed on the mold compound to the lead frame (die paddle) interface after an environmental test. Although this type of delamination is not listed as a “failure” in J-STD- 020A, we consider it to be a warning sign.
Acoustic microscope, plastic encapsulated microelectronics, delamination
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