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Cover story


9001 certifi ed and has over 17 years of industry experience. The Quality and Reliability teams


at Rochester performed analyses of package internal integrity, component-to-PCB solder joint quality and electrical test results, to validate that semiconductor devices do not degrade after long- term storage. Analysis methods included X-ray imaging, laser, acid decapsulation, cross-sectioning, scanning electron microscopy (SEM), and both functional and timing electrical tests. A random sample was conducted


by selecting three packages of different types, with varying date codes of devices available for testing. The three package types were a 28-lead plastic leaded chip carrier (PLCC), a 14-lead thin shrink small-outline package (TSSOP), and an 8-pad very thin small-outline non- leaded package (VSON). Laser decapsulation was


performed on the selected devices to expose the die and examine for defects. No corrosion, cratering or bond pad cracking were found. Rochester partnered with industry experts for the design, manufacture and use of printed circuit boards to mount various surface-mount devices of differing package types and date codes. All devices successfully completed refl ow at the independent PCB assembler. Rochester verifi ed these results via optical and X-ray inspection of solder joints, cross-sectioning along the length of soldered leads, and SEM imaging of cross-sectioned solder joints. Fifty-seven plastic surface-mount


devices of 12 different outlines, packaged as early as 2006, were mounted on both sides of each PCB. All pads were inspected, and no failures were found, confi rming successful PCB assembly. To gain further insight into otherwise obscured solder fi llets, PCB assemblies were imaged by


All devices were laser decapsulated Rochester’s


diligent research has shown that long-term storage doesn’t necessarily result in product degradation. In


fact, components can still be functionally


assembled and are electrically viable for many years


X-ray at an oblique view. Imaging of the VSON package didn’t provide any additional detail, due to the length scale and density of solder coverage. Additionally, SEM images were


captured after cross-sectioning through leads, revealing the precise profi le and internal structure of solder fi llets. Internal structures of solder fi llets were found to be robust, matching external inspections and further validating successful PCB assembly.


The same imaging techniques


were also used to validate the integrity of encapsulated materials and inspect internal device features for defects. No defects were observed.


Rochester Electronics is the world’s largest continuous source of semiconductors – 100% authorised by over 70 leading semiconductor manufacturers. As an original manufacturer stocking distributor, Rochester has over 15 billion devices in stock, encompassing more than 200,000-part numbers, providing the world’s most extensive range of end-of-life (EOL) semiconductors and broadest range of active semiconductors.


www.electronicsworld.co.uk April 2023 07


and fi nished with a short acid etch. No damage was observed that’s consistent with environmental stresses or proposed mechanisms of degradation after long-term storage. All devices were found to be free of cracking, delamination and bond wire defects. Three products of two different date codes were tested to their respective datasheet requirements. The tested devices span nearly 15 years. Twenty 9513APC devices, 25 27S21PC devices, and 50 UC3835N devices of each date code were tested. All devices met their respective datasheet specifi cation limits and exhibited no signifi cant or consistent shifts in data distributions across date codes. The data presented indicates that


devices maintain internal and external integrity, including robust soldering to printed circuit boards, beyond a decade of storage. Devices exhibited no evidence of corrosion, cracks, or delamination. The tested devices passed all applicable functional and timing tests. Rochester’s diligent research has shown that long-term storage doesn’t necessarily result in product degradation. In fact, components can still be functionally assembled and are electrically viable for many years. Storage presents a viable solution for long-lifecycle applications. Find out more: www.rocelec.com


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