Issue link: https://iconnect007.uberflip.com/i/1078362
22 SMT007 MAGAZINE I FEBRUARY 2019 looking to qualify and monitor an assembly process. Looking at each solder operation as part of an overall quality system allows you to control cleanliness better. When you are testing PPAP samples, we al- ways recommend some sort of environmental exposure testing along with IC test to help cor- relate performance under elevated heat and humidity conditions. What this additional test does is show that whatever level of residues you have on your product after assembly won't cause electrical leakage related issues, and you will have IC levels to correlate to. When going into full production process monitoring, IC is much faster than a 168-500 hour environmen- tal exposure test. Monitoring specific location cleanliness can be done in several ways. Doug Pauls from Collins Aerospace and I released a presentation at the High-Performance Cleaning and Coating Conference in 2012 that detailed about a dozen different ways to perform local- ized extractions for IC analysis. I've mentioned that this type of testing isn't cheap, but when you compare the cost of prov- ing you have a good, clean process against the cost of a wide-scale recall, it's not even in the same ballpark. When you're competing against other suppliers or CMs, having a better quality system in place than your competitor will pay for itself many times over. SMT007 Eric Camden is a lead investigator at Foresite Inc. To read past columns or contact Camden, click here. When going into full production process monitoring, IC is much faster than a 168–500 hour environmental exposure test. fective wash and rinse processes. If they have that, and the shop down the street is using a one-megohm dummy light, you can pretty much guarantee that the shop with a better water system is supplying you higher quality bare boards. Bare boards are the basis of your final product, so if you start with better quality boards, you will ultimately have higher qual- ity final product. As previously mentioned, the component manufacturers are up against some of the same issues in terms of removing plat- ing chemistries, so the same recommendation for water systems applies here. There isn't a lot more you can test with bare boards regard- ing cleanliness, but having a quality system in place for every customer can put you in front of your competitors without a doubt. When it comes to the CM and the actual as- sembly process, there are more tests you can add to your overall quality system to help give you the edge over your competition. You can start with using suppliers that perform tests previously mentioned that show you're using quality parts and boards. This is especially im- portant when using no-clean flux for the pro- duction as there is not a final wash process that can help remedy the sins of your suppliers. IC analysis is still the gold standard for determin- ing the exact type and amount of ionic residue present on final assemblies, but that is also ex- pensive and not realistic to have in-house in most cases. A few of the larger CMs do have IC in-house, and when used for process quali- fication and monitoring instead of just failure analysis, it can really help put them in their own league. As part of an assembly house's cleanliness strategy, it is important to understand that overall ionic cleanliness is one thing, but look- ing at specific locations on an assembly is even more important. The reason that is true is that when you have a failure, the entire assembly doesn't fail but a single point related to a sin- gle process or part does. Knowing this you can separate each assembly process, better deter- mine which one is the culprit, and be able to do it much faster than any full board analysis. Being able to distinguish reflow from wave- from-hand operations is crucial when you are