| Wondering if anyone has information on percentage of components that we | can expect to "lose" during our SMT process. We are new to SMT, using | QUAD machines and feel we are losing to many parts during our process. | We are spending a lot of touch-up time replacing components. Any help would | be appreciated. Tim, You don't ever "lose" components, you have what's called "process attrition"...(hehehe...) The first figures I ever heard quoted to one of our consigned customers was 3% and 1%...3% for passives, and 1% for actives...(we were running FUJI equipment at the time...) That has always seemed like a reasonable number when you figure in threading feeders without enough leader, test failures, and such. The 3% and 1% may seem a little excessive... and maybe it is a little, but that's what we always told our customers. Mainly, just to make sure that they always gave us at least SOME attrition for a job...nothing worse than getting down to the last 10 or 15 boards in a job, and then start running out of parts. Now when you say you're losing components in your process, do you know exactly where it's happening? Is the machine rejecting them? Or are you discovering the missing components someplace later in the process like Test, or Final Q.A.? The boards shouldn't be coming out of your pick and place machine missing parts...if they are, something is DEFINITELY wrong! I found from experience that bottomside epoxied parts are pretty easy to lose in your process if people aren't aware about certain things. A lot of people don't understand that the epoxy that we use for bottomside components is ONLY strong enough to hold the parts on the board while they go through wave solder, and nothing more. When they hear the word epoxy, a lot of people think of some 2-part, 2-ton stuff that they've always used to fix that broken chair leg at home with. So they aren't as careful as they should be when handling the partially built PCB's after they've come out of the oven from curing the epoxy. Components can easily get knocked off when carrying them around in tilt racks, or when they're being masked and stuffed for wave solder. Those figures should be easily doable unless you're having some other problems. If the machine is rejecting all the parts that you're talking about, then I would get somebody from QUAD to come and help you out...there should be no reason to exceed that 3% and 1%... I hope this helps a little... -Steve Gregory-
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Wondering if anyone has information on percentage of compo...
- Apr 13, 1998
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