Steve & Darrel, I appreciate both your inputs. Sounds like my vendor is correct in saying 'some people do tent only one side'. Steve, I have to agree with you about getting contamination into a 12 mil via which has been reduce in size by solder mask. In fact, I am not so sure I can even clean a 12 mil via (0.062 thick PWB) if it didn't have solder mask tenting. (I am using a water/saponifier in-line cleaning system.) Maybe my concern about trapping additional contamination is not valid. Jim Kittel >-----Original Message----- >From: Stephen R. Gregory [SMTP:[log in to unmask]] >Sent: Tuesday, March 23, 1999 10:21 PM >To: [log in to unmask] >Subject: Re: [TN] FW: LPI Tented Vias for BGA's...Part II > >In a message dated 3/23/99 4:43:25 PM Pacific Standard Time, >[log in to unmask] >writes: > >> I'm not sure if either method is better then the other, but from my >perspective, having tenting on the secondary side presented more of a risk >then the primary side as far as providing a place for getting "stuff" trapped >under the BGA was concerned. I suspect Steve has his perspective as well, and >I have no data to say one way or the other, but we tent the primary side, to >give you another datapoint. > >Regards......DT > >Hi Jim, it's me again, > >Thinking about what Darrel said, he may have a point. I think a lot of it may >depend on how big the via's are. You said that the vias in question are >.012"...that's pretty small. So even if the opening isn't completely closed >off by the mask, it sure does make the opening smaller than .012''...how >much >smaller I don't know. > >What I'm thinking, is that when you think about the the physics of surface >tension of the flux and solder, that's what's preventing "stuff" from getting >in there, it can't get through openings that small.....I guess I'm thinking >out loud trying to understand why Darrel doesn't have any problems when vias >are open on the wave side. Maybe when I had the problems I spoke of, maybe >the >vias were a larger diameter... > >One last issue with vias open on the wave side (and this may be size related >too...) is re-reflow of connections that have short trace lengths to a >topside >pad...there's a bunch of us that have seen that before... > >-Steve Gregory- > >################################################################ >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 ################################################################