> Steve, > We do a percentage of lot inspection for ISO. If you are considering > becoming certified then you will need to do process control which will > require a need for inspection. BGA's can only be inspected by x-ray so how > else would you do it? > > Linda Hi Linda! How would I do it you ask? Easy, we got this guy workin' for us named Clark Kent and he...what?....not buyin' that are ya?...didn't think ya would...hehehe. Seriously, my logic is that when you're pumping out production boards, you should have your processes dialed-in. Production scenario: You've got your stencil tweeked, paste is just the stuff you want, and you know you can print 15 times and then program a cleaning cycle to keep the image crisp. You also know that each print takes 3-grams of paste, so you'll program a dispense cycle in every 30 prints to keep a nice roll of paste in front of the squeegee. You know your placement programs are dead on because they came from cad data, you also verified that on your first article. Reflow profile was created, plotted, and given a fine adjust for the first article, which was followed with the xray inspection. Now you're gonna run some revenue. You've got your people doing periodic, random, process checks and logging them after solderpaste print, placement, and reflow, and they're doing a great job making sure that happens. So you tell me, when should I fire up the ol' x-ray machine again? When would I r-e-a-l-l-y need to if what I described above was happening? See my point? Things normally don't all of a sudden go wacko for three boards and fall back in line again. If you have your process set and being monitored, I have a hard time coming up with a good reason to justify x- ray for anything other than initial process set-up and verification. If you find something during a production run, in my mind, it's too late. What would you do? Stop production and go back and x-ray all the boards that were built from the last time a board was x-rayed? Don't get me wrong, I'm not saying what you're doing is a waste, but these are things that I've been thinking about trying to really justify the expense of a x-ray. Will it really be earning it's keep while every other machine is producing something? Food for thought huh? -Steve Gregory- Steve, I would have to agree somewhat with you. We have built a couple of hundred thousand, or more, cards with BGA's (both ceramic and plastic). We don't use x-ray inspection for two reasons, expense of the x-ray machine, and question marks over it's ability to reliably detect contact opens. We verify our processes by cross-sectioning, on the first few cards. In production the two sets of parameters that seem to affect repeatability are paste application and reflow profile. We use a cybercentry in line to verify that paste has been deposited correctly, and a continuously monitored reflow oven to control reflow profile. Once optimised these two mechanisms allow us to maintain paste and reflow conditions within acceptable limits. Regards Evan Evan Jones Manufacturing/Test Engineer Bluegum Technology Pty Ltd PO Box 609, Wangaratta, Australia, 3676 Ph: 61 3 5720 2539 Fax: 61 3 5720 2412 Internet: [log in to unmask] ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################