> -----Original Message----- > From: Lee, Scott > Sent: Tuesday, October 06, 1998 11:08 AM > To: 'Nüchter Wolfgang (FV/FLT) *' > Subject: RE: [TN] Via's under BGA's > > Wolfgang, > > We have been utilizing this land shape since mid 1993. Many of our > products are used in extreme rugged conditions including deployment in > a variety of land, air and sea vehicles. These products, obviously, > go through rigorous qualification testing that includes temperature, > vibration, and humidity parameters (we base our testing on > MIL-STD-810E). I am not aware of a land ever being a cause for > failure. > We, also, have a pretty fair handle on our component rework process > and have not experienced land failures due to that mechanism. > > As far as your concern of strange pad shapes, we have had success with > both the teardrop (our preference) and the barbell style pads. But, > we have not delved into anything particularly exotic. > > Best of luck. > > Scott E. Lee > Manufacturing Engineer > Mercury Computer Systems > > -----Original Message----- > From: Nüchter Wolfgang (FV/FLT) * > [SMTP:[log in to unmask]] > Sent: Tuesday, October 06, 1998 10:41 AM > To: 'TechNet E-Mail Forum.'; 'Lee, Scott' > Subject: AW: [TN] Via's under BGA's > > Scott, > have you any expirience with lifetime behaviour of your teardrop pads? > Or temperature cycling, ... > Does anyone uses other strange pad-shapes and has experience with new > failure modes? > > Wolfgang Nuechter > Corporate Research > Robert Bosch GmbH > Germany > > > > ---------- > > Von: Lee, Scott[SMTP:[log in to unmask]] > > Antwort an: TechNet E-Mail Forum.;Lee, Scott > > Gesendet: Montag, 5. Oktober 1998 21:31 > > An: [log in to unmask] > > Betreff: Re: [TN] Via's under BGA's > > > > Romeo, > > > > Be very careful of aspect ratios if you go this way, the use of a > > microvia will generally limit the layer count due to this factor. > Which > > in turn, will limit the available surface area for escape routes. > In a > > lower I/O count BGA, the impact may be lessened. If not, to > overcome > > this, you may need to go to blind segments, this tradeoff is not one > > that I would accept. > > > > We have had much success keeping it simple and utilizing teardropped > > lands to the via. In this approach, the routing limitations are > > therefore only felt on the primary layer. In general practice, we > have > > found that the more exotic the solution, the lower the yield rates. > > > > Scott E. Lee > > Manufacturing Engineer > > Mercury Computer Systems > > > > > -----Original Message----- > > > From: Kubes, Romeo (NM75) [SMTP:[log in to unmask]] > > > Sent: Monday, October 05, 1998 3:03 PM > > > To: [log in to unmask] > > > Subject: Re: [TN] Via's under BGA's > > > > > > Chad, > > > > > > Is using blind Microvias acceptable, since their cavity is so > small it > > > would > > > rob a very small % of the solder? (I know this is expensive, but > > > besides > > > this factor). > > > > > > R. Kubes > > > Honeywell DAS Albq > > > > > > > ---------- > > > > From: Thibodeau, Chad[SMTP:[log in to unmask]] > > > > Sent: Monday, October 05, 1998 11:41 AM > > > > To: [log in to unmask] > > > > Subject: Re: [TN] Via's under BGA's > > > > > > > > Bridget, > > > > > > > > There was an excellent paper written by Paul Mescher of Amkor > Anam > > > > addressign "...Surface Mount Assembly of Amkor/Anam BGA > Packages". > > > In > > > > this > > > > paper Paul describes the importance of PTH isolation (via > isolation) > > > and > > > > to > > > > paraphrase him: "No matter what shape or definition technique is > > > used for > > > > the mounting pad, the isolation of the PTH from the mounting pad > is > > > an > > > > important feature. If the PTH is contained within the mounting > pad, > > > > solder > > > > can and will wick down the PTH. The amount of solder that wicks > > > depends > > > > on > > > > many factors, including PTH finish and coating variations. > Because > > > of > > > > this, > > > > the results are somewhat unpredictable. Some solder joints may > be > > > > unaffected, while others will be starved to the point of > creating > > > opens. > > > > The worst result is a partially starved joint with severely > reduced > > > cross > > > > section. This joint can have significantly lower fatigue life > and > > > result > > > > in > > > > early system failure. Because the quality of the solder joint > is > > > > guaranteed > > > > by control, rather than inspection, designs/processes that > result in > > > > random > > > > distributions are generally considered unacceptable, and the > > > PTH-in-pad > > > > design is not recommended." > > > > > > > > If you require additional information you may want to talk with > Paul > > > > himself. I do not have his number, but he is located in > Chandler, > > > AZ. > > > > > > > > Chad Thibodeau > > > > EF Data > > > > Component Engineer > > > > 602 333-2138 Phone > > > > 602 921-9012 Fax > > > > [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 > > > > ################################################################ > > > > > > > > > > ################################################################ > > > 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 > > > ################################################################ > > > > ################################################################ > > 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 > > ################################################################ > > ################################################################ 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. 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