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24 SMT007 MAGAZINE I JUNE 2021 Feature Article by Graham Naisbitt GEN3 Determining acceptable cleanliness demands significantly more investigation than has histor- ically been the case. Until recently, the industry has been too reliant on the use of a "cleanliness" level of <1.56 µg per cm 2 NaCl equivalence. at has been removed from the venerable IPC-J- STD-001 now in Revision H. With increasing packaging density, coupled with hostile operating conditions, the inci- dence of circuit failure has increased. Such failures are, most likely, the result of adverse electrochemical migration. Dendrites are the result. Today's non-negotiable requirement is to produce objective evidence. As can be seen from Figure 1, the two tools that have been proven to be up to the task, are SIR followed by PICT. What can also be seen is the plethora of issues that must be addressed. For far too many years, the industry had been using the term "cleanliness," which was partic- ularly unsuitable because: • Cleanliness assumes you have tested all possible contaminants on the board. You can't do this. • Process control assumes you are removing the same contaminants every time. You can do this reliably and reproducibly. Cleaning and Inspection

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