>Date: Thu, 30 Jan 1997 07:35:35 >To: [log in to unmask] >From: Neil Maloney <[log in to unmask]> >Subject: Re: FAB - Defective units on panelized PWBs > >Jennifer, > I know the problem and a possible solution. >In our plant we use a Mydata TP9-2 PNP which has a "bad board indicator" feature. Each PWB on the panel has a "bad board fiducal" placed somewhere central (generally in the center of a large component, like a QFP) If the PNP vision system sees contrast around the fiducal, if surmises that the PWB is good. On the other hand, if it sees no contrast around the location (as if a white sticker were placed over the spot) it declares the PWB bad and places only to the "good" boards on the panel. Automatic. > Before each panel is put into production, our operator places a VERY THIN white label over the bad board fiducal. It doesn't even HAVE to be a fiducal, any large pad or contrasting mark will do. > >Down, dirty, and cheap--but effective. > >The thickness of the label is very important, as it will be stuck to the panel throughout the process, including screen printing. Also there may be ESD issues here. > >If your PNP can do this, (most of them can, I believe) no problem. > >For the other question, I make PCMCIA adapters in an 8-up panel (4-layer, 20 mil pitch, .002in thick). Because of the tight parameters, board house loses some out (especially in E.T.) In my case I get 1 or 2 bad units on at least 10% all the panels in the lot. Not much fun, but do-able. > >Neil Maloney >Contemporary Control Systems, Inc >[log in to unmask] > > >At 01:41 PM 1/29/97 -0500, you wrote: >>Is there an industry standard for allowable defects, or x-outs, for panelized >>PWBs? For instance, if a panel is 8-up, and there are 625 panels in the lot >>(5000 pcs. total in the lot), what is a reasonable defect rate? A PWB >>manufacturer has suggested 1 PWB per panel, and a max. of 10% of the panels in >>the lot. For this example, that allows 62 panels with an x-out, which seems >>excessive. The problem with the x-out is that the automatic pick and place >>equipment will stuff the bad PWB unless manually overridden, so there will be >>scrap component costs. Comments, please. >> >>*************************************************************************** >>* TechNet mail list is provided as a service by IPC using SmartList v3.05 * >>*************************************************************************** >>* To unsubscribe from this list at any time, send a message to: * >>* [log in to unmask] with <subject: unsubscribe> and no text. * >>*************************************************************************** >>* If you are having a problem with the IPC TechNet forum please contact * >>* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * >>*************************************************************************** >> >> >> > *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************