Graham, You can also add the back side of leads, sharp angles, and points. I suppose it depends on just how "lucky" you feel! David A. Douthit Manager LoCan LLC Collins Graham wrote: > Hi Joe! > Well, as Joyce observed, Parylene will coat everything, so that's one > (expensive) way. Another way is to underfill the BGA before coating, > with an underfill material. This is what we are currently doing. > > I do question the ability of anyone to truly meet that requirement > though, when using a conventional spray technique. For example, if you > have vias under components (which is pretty much standard these days) > then you will have exposed circuitry unless you are using a dry film > solder mask. > > regards, > > Graham Collins > Process Engineer, > Northrop Grumman Canada Corporation > Halifax > (902) 873-2000 ext 6215 > > >>> [log in to unmask] 08/08/03 03:04PM >>> > Tech Netters, > > I am looking for some input on a special issue related to the > conformal > coating of boards with BGAs. According to IPC-A-610C, section 9.1.2, > voids > in the conformal coating material can not expose circuitry, bridge > lands or > adjacent conductors. In order words, all exposed circuitry/conductors > are > to be conformally coated. > > BGAs have conductors/solder balls located "under" the package unlike > leaded > parts where the leads are exposed and easily covered with conformal > coating > material. Conformal coating may partially wick under the BGA covering > some > of the conductors/balls but not all the way. Some of the BGAs also > stand off > the board a measurable distance which the conformal coat material may > not > bridge resulting in an uncoated gap between the BGA and the pwb. Some > would > interpret this as leaving exposed conductors (under the BGA). > > I would like to know how other manufacturers are dealing with this > issue. > Ideally, one would seal the perimeter of the BGA with conformal coat > thereby > not exposing conductors but conformal coat material will not bridge > gaps > greater than x mils. Look forward to your response. thanks > > joe > > --------------------------------------------------- > Technet Mail List provided as a free service by IPC using LISTSERV > 1.8e > To unsubscribe, send a message to [log in to unmask] with following text > in > the BODY (NOT the subject field): SIGNOFF Technet > To temporarily halt or (re-start) delivery of Technet send e-mail to > [log in to unmask]: SET Technet NOMAIL or (MAIL) > To receive ONE mailing per day of all the posts: send e-mail to > [log in to unmask]: SET Technet Digest > Search the archives of previous posts at: > http://listserv.ipc.org/archives > Please visit IPC web site http://www.ipc.org/html/forum.htm for > additional > information, or 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 1.8e > To unsubscribe, send a message to [log in to unmask] with following text in > the BODY (NOT the subject field): SIGNOFF Technet > To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) > To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest > Search the archives of previous posts at: http://listserv.ipc.org/archives > Please visit IPC web site http://www.ipc.org/html/forum.htm for additional > information, or 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 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------