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56 I-CONNECT007 MAGAZINE I JANUARY 2026 uct's end operating environment also dictates the best processes to use in manufacturing. These are things that must be considered and communicated when creating the design. For example, if your board's end product is a cell- phone, you can probably assume that it won't be oper- ating in an extreme environment. Your quality spec- ifications will be according to a "normal" operating environment, and the product lifecycle is a few years, not decades. But what if the board you're designing will be placed into a product that lives inside a car, is being shipped and stored in Alaska during winter, or that the end product will be in a server room in India? This is what drives your design, calling out the use of specific laminate material and solder flux. Ideally, you have all this information before you start designing your PCB, but what happens when you don't have the necessary information upfront, or when it's not clearly understood, even on the customer's side, that something has changed? Yes, we had a case where a particular board had been reliably built for years and then, after proba- bly several hundreds of thousands of good assem- blies had worked reliably for the time needed, we suddenly started to see several field failures in one area of the board. The boards were out of compli- ance with the allowable levels of contamination, which caused the failures. What had changed? We conducted a failure anal- ysis and found that a few vias had been moved. That is not normally a big deal, and the assembly was built using the same no-clean flux as always, but what we did not know at that point was that the product would have to operate in a different physi- cal environment than before. The real challenge was that, initially, all the data was good on the parts that came back. So, we really had to dig. We discovered that these particu- lar boards were being placed in a coastal environ- ment (hot, humid, and loaded with contaminants). The failures were due to excessive sodium levels, but the parts that came back showed data within acceptable limits. We used a no-clean chemistry for the soldering process (which does leave a certain amount of residue), and that base level of contam- inant, when the boards were further processed and then tested, created an unacceptable level of contamination cumulatively. However, the board fabricator and we, as the assembler, believed they were in compliance because they were within the range of the only specification we had been given to reference. The key point is that no new require- ments were given to the board manufacturer. How did you resolve this issue to ensure future manufacturability and reliability? We did extensive testing in terms of contamination lev- els and worked directly with the customer to find the root cause of the issue and define new values for the board manufacturer to ensure they would produce boards that were in spec for contamination. Clearly, collaboration and communication remain key. How do you best test for this type of potential defect or failure? What are the types of tests you use and what specific thing(s) are they testing for? We've been doing ion chromatography (IC) to determine what contaminants are on the assembly, also in parallel SIR testing has been performed on PCB coupons level with a new flux chemistry, since the original one that we've started with left behind a residue that did not perform as expected within the "new" end use environment. Now, obviously, IC and SIR tests take time and come with a cost attached. Once we'd identified the new flux that was to be used on the product family we also per- formed C3 and ROSE (with established control lim- its based on experimentation) testing for process control purposes. ROSE testing here would not be the best choice due to the no-clean nature of the materials. C3 was the best suitable test for process control in our case with the original material, but ROSE test was doable with the material that we were selecting for replacement. Tibi, what are the IPC specifications being refer- enced in these cases, and are they adequate? There are some very good documents out there, but nothing provides everything (Table 1). Consult- ing these resources can be the difference between designing for a good result or unintentionally designing for poor reliability.