John Maxwell, Where can we find your articles about DFM? Answer off-line if you want. ===== Original Message from [log in to unmask] (TechNet E-Mail Forum.) at 1/06/00 18:14 >Hi TechNet, >To be precise I never recommended water jet cutting due to poor through put >and high capitol expense. I have never been an admirer of roller blade >cutting except when I was a consultant and it put my wife and oldest son >most of the way through university. Ceramic capacitors are sensitive to >cracking and becoming more so due to technology trends reducing dielectric >thickness. Isolating parts from PWB edges is still a good idea and >orienting MLCC parts parallel to a PWB edge helps. > >As a second note, in a former life I designed transistor structures for >integrated circuits and I have a comment on X-ray. X-rays are ionizing >radiation and can change transistor gate threshold voltages in your >integrated circuits by damaging the gate oxide. As gate oxides get thinner >the problem appears to get worse. I suggest that a call to your silicon >vendors might be in order and ask them to check with their device >designers. Some that I have talked to have expressed real concern if we get >carried away with our X-ray machines. I have one and it is one of many >process development and failure analysis tools. > >John Maxwell > >At 10:11 AM 6/1/00 -0700, you wrote: >>John Maxwell discouraged using rolling blade shear but recommended water >jet >>cutting for depaneling. Does any body know who makes such water jet >>cutter? Any >>users out there who can share some experience? >> >>Thanks, >>KK Chin >>Artesyn Technologies >>Fremont, CA >> >> >> >> >>Gabriela Bogdan <[log in to unmask]> on 06/01/2000 09:25:55 AM >> >>Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please >respond to >> Gabriela Bogdan <[log in to unmask]> >> >>To: [log in to unmask] >>cc: (bcc: KK Chin) >> >>Subject: Re: [TN] V-Score--stress >> >> >> >>Being one of John Maxwell's "fans" I recommend his articles about design >for >>manufacturability . Concerning chip capacitors, we follow as much as >possible >>the rules >>, and Dwight's comments are in this spirit. Most of the failures we also >>encountered >>were with chip capacitors, and the separation method , the distance from >the >>edge, and >>the orientation of the chip were the culprits, alone or in combination. We >had >>for >>instance one panel with circuits which were manufactured first as single, >then >>as 4 in >>panel. Due to the proximity of the chip cap to the edge, we had failures >after >>separation, and had to change the artwork accordingly. >>Gaby >> >>Dwight Mattix wrote: >> >> > We score many designs. It's a really useful process to optimize panel >> > utilization and sometimes assy tooling/depaneling tradeoffs. However, >our >> > experience here shows your concerns are valid. I suggest the even >bigger >> > concern should be the risk of latent defects that will pass through all >> > your tests and into the field. >> > >> > We've seen the risk to be with ceramic chip components (chip caps et al) >> > within .1 - .2" of the score. The mode is latent ceramic cracking >leading >> > to leakages or outright device failure. Either way the end result is >the >> > same -- field infant mortality. >> > >> > As a result of our experience (read scar tissue -- and some crude long >> > forgotten rel experiments way back in the early 90's dark ages -- Phil >> > Bavaro may have better memory of that) our design rules don't allow >scoring >> > if chip components are within 0.200" of the score. The exception to the >> > rule we sometimes make is when the assembly has shields soldered out to >> > board edge effectively making a box beam that stops/reduces flex of the >> pwb. >> > >> > I'd be real interested to hear what others have learned and design rules >> > they maintain -- esp if there's been some science applied to their >> > establishing their rules. >> > >> > Dwight >> > >> > At 11:01 AM 6/1/00 -0400, Ed Holton wrote: >> > >We have recently started using boards with V-score for the >> panelization and >> > >we have a debate raging here. There is a concern about separating the >> > >boards before versus after the incircuit test and whether there is the >> > >possibility that there is imparted stress to the board that could >create a >> > >failure mechanism that might have been caught at the ICT and not at the >> > >functional test, thus the requirement to singulate before versus after >> ICT. >> > >I have read various articles, but am wondering what people have found >in >> > >the real world. >> > > >> > >Thanks >> > > >> > >Ed Holton >> > >Manufacturing Engineer and Group Leader >> > >Hella Electronics >> > >Telephone (734) 414-0944 >> > >Fax (734) 414-0941 >> > > >> > >############################################################## >> > >TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for >> additional >> > >information. >> > >If you need assistance - contact Keach Sasamori at [log in to unmask] or >> > >847-509-9700 ext.5315 >> > >############################################################## >> > >> > ############################################################## >> > TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for >> additional >> > information. >> > If you need assistance - contact Keach Sasamori at [log in to unmask] or >> > 847-509-9700 ext.5315 >> > ############################################################## >> >>############################################################## >>TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for >additional >>information. >>If you need assistance - contact Keach Sasamori at [log in to unmask] or >>847-509-9700 ext.5315 >>############################################################## >> >>############################################################## >>TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for >additional >>information. >>If you need assistance - contact Keach Sasamori at [log in to unmask] or >>847-509-9700 ext.5315 >>############################################################## > >############################################################## >TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for additional >information. >If you need assistance - contact Keach Sasamori at [log in to unmask] or >847-509-9700 ext.5315 >############################################################## Martin Christie ACW Technology Ltd., Hylton Road, Petersfield, Hants. GU32 3XX Tel: 01730 300000 ext 146 Fax: 01730 266045 e-mail: [log in to unmask] ############################################################## TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################