This article originally appeared in the September issue of Procurement Pro.
Despite growing industry recognition that date code restrictions lack a factual basis, some users of semiconductor components and contract manufacturers continue to enforce limitations on products older than arbitrarily set age limits.
Rochester embarked on a study to evaluate the solderability and board assembly of surface mount technology (SMT) components following various long-term storage periods.
Previous Rochester whitepapers demonstrated that broad types of parts remain fit for use after long-term storage. This study compared solderability test results and printed circuit board (PCB) assembly performance for aged surface mount devices. Rochester aimed to identify the most accurate test method for predicting successful board attachment. The study revealed notable discrepancies when comparing traditional solderability testing to physical device mounting for evaluating devices post-long-term storage.
Traditional solderability testing was independently conducted across three testing sites, using both Solder Bath/Dip and Look and Surface Mount Process Simulation methods. Boards designed to mount these devices were assembled at three contract manufacturers and internally at Rochester Electronics. Assembled boards from each contract manufacturer were submitted to an external laboratory for cross-sectioning and scanning electron microscopy (SEM) imaging analysis. Electrical testing was performed on surface mount devices independently of those selected for board attach.
The findings of this study suggest a surprising revelation: traditional solderability test methods may not accurately reflect the performance of components on boards post-long-term storage. This discrepancy is likely a result of these methods being developed for newly manufactured devices. As demonstrated here, directly mounting devices onto a relevant PCB provides a more precise simulation of real-world component usage conditions.
Each component can be critical for manufacturers of long-lifecycle systems facing product availability and supply chain continuity challenges. Using traditional solderability test methods as a screen at incoming inspection may place an additional and unnecessary constraint on the limited population of available devices. It is essential for users of aged semiconductors to carefully assess the possibility of unnecessarily rejecting fully operational and solderable devices while establishing inspection protocols.
Rochester Electronics’ research on long-term storage has spanned over four years of testing, dozens of product types, and devices manufactured in four decades. Methodologies have included electrical testing, non-destructive X-ray inspection, solderability testing, package deconstruction analysis, PCB assembly, cross-sectioning, SEM imaging, and visual inspection.
To date, no data has been found to indicate degradation of product functionality or usability due to long-term storage at Rochester. Rochester’s newest study reinforces the industry’s prevailing understanding that there is no evidence to support date code restrictions.
