Hi Earl, Across an 18 x 24 panel, the minimum registration tolerance of clearance to pad is +/- 0.002". Isolated features can be held to +/- 0.001" if essential. We recommend a minimum solder mask web width of 0.004". An absolute minimum of 0.0025" can be maintained in isolated areas. Hope this helps. Best regards, Keith Larson Circuit Technology Inc. [log in to unmask] wrote: > I've been afronted with the latest BGA schemes dreamed up by someone not looking at, or willing to > follow relatively simple design rules. That's my story. > > I remember LPI could hold fairly tight registration dimensions and tolerances across a panel. I just > don't remember all I forgot concerning how tight these parameters might be. > > The best way to describe this dilemma is to say someone designed a 432 ball permiter BGA with some > outer layer traces within 5 mils of the inside balls when 50 mils was available. With all things > considered, without redesigning, there often are traces open to the aforementioned pads. Wonder why? > > The real question is what currently is reality without special "tweaking"? I mean, what are the > practical process capability limitations concerning how tight will LPI S/M cover the distance > without shorting - routinely - over say an 18 by 24 panel? > > Earl Moon > > ################################################################ > 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 > ################################################################