Issue link: https://iconnect007.uberflip.com/i/1243344
44 SMT007 MAGAZINE I MAY 2020 tiplies the rankings by the weights to calculate the individual scores. The user can then see how each paste compares to the incumbent in each characteristic and category. They make an informed, data-driven decision, and as they migrate toward their new soldering chemistry, they are guarded against the gotchas because they've already looked at 25 different proper- ties on their assembly line and have a good idea of what to expect. We've run into situations where somebody selects the paste because it's low on voiding, and they find out it's not very active, and it doesn't wet very well, or it has great response to idle but isn't pin-test friendly. There's always a trade-off in solder paste. This test method is meant to encompass all the differ- ent properties, so the user knows what their trade-offs are right up front before implement- ing it. Johnson: An evaluating assembly shop is going to get some answers on if I can achieve the kinds of precision that I want and where my current set-up is failing. Is it the paste or equipment I'm using or the expertise of my operators? It would seem that this will tend to shake out the problem areas for the assem- blers. enough overlap that you generally get a good idea with one baseline? Shea: I usually advise my clients to contact as many paste suppliers as they want, but then do a down-select to three before they run any final tests. When a user fills in the scorecard, before they put any data in it, they weight how important a particular characteristic is to their operation. Again, there are 20+ char- acteristics. They know what's important to them. For example, If they are a low-volume shop, response to idle time is very important to them. If they are a high-volume shop that runs 24/7, idle time is of far less consequence. Once they have determined their needs by heavily weighting their key factors, they can then effectively communicate those needs to the paste suppliers, who better understand the trade-offs in properties and can deliver the best candidate for the application. I suggest the user choose whatever the most stringent test is and use that for a down-select. If they want to be able to run that first print after an hour, or everything they run goes through pin test, it's easy to do a down-select there. Then, they take the top two or three and run them against the incumbent. The user ranks the results in the scorecard, which mul- A scorecard breakdown.