Issue link: https://iconnect007.uberflip.com/i/1379105
JUNE 2021 I SMT007 MAGAZINE 19 economical, and the quickest time, but you've got to get it done. Johnson: Cleaning uses chemicals, and water; you have spent material at the end of the pro- cess. What are the challenges of handling that, environmentally? Forsythe: It varies by the process. If you're deal- ing with stencil or misprint cleaning, where you've got raw paste with all those solder balls and once it's cleaned, you have piles of metal, that can probably go out with the dross. at's got to be dealt within its proper mechanism. Frankly, when we were using lead—which was a very reactive metal—it was laying around cleaning products for a long time, and it was easier for cleaning products to absorb it. Not so much with tin, so that's gotten better over the years. ese are organic materials. For most peo- ple, their rinse water will have only minute amounts of the cleaning product in it and an even tinier bit of the soil. In most parts of the world, this will be in complete compliance for disposal down the drain because this is the same waterworks where your gray water goes to and is a massive scale waste proces- sor designed specifically to address low-level organic waste. Most of these rinse water streams have very low-levels of organic materials, so people sell closed-loop systems, and they work fine, but they don't have that scale that the waterworks can achieve. In some places, you need a spe- cial permit. It can be a hassle, so you have to do it wisely. In other places, it's easy to be com- pliant. e products themselves typically have higher organic levels than the rinse water. e soils will eventually build up in the wash tank if it is doing its job. It generates a little bit of waste, but it's not a lot and usually is not a big driver. e issues do come up from time to time. e solvent guys used to talk about that all the time because they liked to boil off the solvent. e soil doesn't really evaporate, their approach is to wrap it in less solvent, so it's in a smaller box. Fundamentally, when you really look at the nuts and bolts of waste, it turns out not to be the biggest issue. Eliminating lead has helped with that a lot, frankly. You only needed a few parts per million lead to become hazardous material. A few parts per million isn't really very much. Johnson: Right. Tom, any parting thoughts? Forsythe: e key to engineering and science is to get granular, and when you do that, the dif- ference between surface prep and cleaning is easy to grasp. When you go up to 10,000 feet or higher, now it's not the same. ere's a lot of surface prep stuff that's very clearly not clean- ing. at's probably why in the assembly world that word never really caught on. Johnson: is has been insightful for me. ere are times when any of us can be in the industry for a long time and just stop, step back, look at it, and come away with a completely differ- ent, changed perspective, and a bit more con- text for everything. It's as simple as that. Forsythe: at's the key to everything. e key is context. I'm glad I could be helpful. I appre- ciate the opportunity to talk about it. It's always fun. SMT007 Ultrasonic cleaning ensures the cleaning agent reaches every surface of the circuit boards.