SMT007 Magazine

SMT-July2018

Issue link: https://iconnect007.uberflip.com/i/1000349

Contents of this Issue

Navigation

Page 25 of 105

26 SMT007 MAGAZINE I JULY 2018 rial handling. Is it open to the environment? Could your areas have humidity or temper- ature control that could cause failure when you're doing paste printing? During the reflow, especially under low standout components, is all the flux activated? When you start looking at component placement you look at the larger companies versus smaller companies, is it all done manually? Are they using gloves? Do they have finger oils and residues that are trans- ferred from product to product? Then with wave soldering, is there any inac- tivated flux? Do either the tooling or the low standoff pin through hole components or from the thermal profile that's used that doesn't acti - vate all the flux that might be hidden? All of these areas are potential locations for ionics to be added to the board which would then get down in the field for what I look at ruggedization. If they're not cleaned they could produce field fail - ures like Bob listed earlier about corrosion. Now, when you start looking at best practices of conformal coating, the first thing is to select the conformal coating material. Not really for what's the cheapest available, which unfortu- nately is what a lot of people do, or what is the material we have in house? We should use it for this other product. They need to look at what's the lowest total cost of ownership for a product life cycle, not just the individual prod- uct cost to produce that device. That's one key aspect. The other one is, as we were mentioning earlier, you need an agreement between the user and the customer about workmanship. Where is coating required? Where is coating not required to be present? The key aspect of both those two are what are the tolerances? When you have a connector and then you have a line that goes up to the connector body, well is a splash on a connector body acceptable? These types of discussions have to happen. Then you look at inspection limits and magni- fication. IPC only has up to 4X, yet a lot of people will look at soldering and then conformal coating under a microscope and they find all these defects that might not actually be defects as looking after conformal coating. Repair—is it allowable, or is it not? If it is allowed, what are the condi- tions? Is there an approval process? When you start looking at all this and you're develop- ing an optimal conformal coating factory for productivity as well as operator safety, what do you need in place for best practice? Is it a single-piece fixture flow? You've got to make sure you have all the appropri- ate Kanbans. The coating application system you're going to use, does it meet customer requirements as well as manufacturing targets? All the process controls that are used, are they both available and are they correct? Sometimes, people are like, "I've got process control. I get this value in line." But it might not be the right process control you need to make sure you're using the correct ones. Some of the key stuff is DUEs and CPKs. Did they do that at the very beginning of a process implementation review to make sure they get the most robust process so that every product is done with the best reli- ability and best repeatability? Then, is there a final report that's available that says all of these parameters and everything is documented showing that all the require- ments are achieved? Above all of that, anyone that's then doing conformal coating or some other types of ruggedization, how do you know what you're getting? How do you know how you're controlling it and how do you figure out what needs to be done and discussed so that you can get to that point? I think those are the key aspects I look at for best practices.

Articles in this issue

Archives of this issue

view archives of SMT007 Magazine - SMT-July2018