I guess I should do a cross-section, huh? One cross-section coming up! (gimme a day or two) -Steve Gregory- "Wenger, George M." <[log in to unmask]> wrote: -----Original Message----- From: Wenger, George M. Sent: Monday, September 12, 2005 8:23 PM To: 'John Burke'; 'TechNet E-Mail Forum' Subject: RE: [TN] raised vias... John, We won't know for sure until Steve does a cross section but my assessment right now is that the raised ant hills are all too uniform to be unfilled vias that have solder being pushed out. When I look at the photograph it looks like a continuous sheet of copper that has bulged areas rather than ant hills with an opening due to outgassing. Regards, George George M. Wenger, Andrew Corporation Reliability / FMA Engineer Base Station & Subsystems Group 40 Technology Drive, Warren, NJ 07059 (908) 546-4531 [log in to unmask] -----Original Message----- From: John Burke [mailto:[log in to unmask]] Sent: Monday, September 12, 2005 8:15 PM To: 'TechNet E-Mail Forum'; Wenger, George M. Subject: RE: [TN] raised vias... I think they are not filled, I believe the HASL process filled the vias (horizontal HASL). I also think that the very thick core kept the via hole solder molten long enough after process for the outgassing taking place in the via holes to push the solder back out of the via forming the ant hills. Who knows...............Section it Steve................... John ------------------------------------ Avanex John Burke Senior Manager RoHS Compliance [log in to unmask] 40919 Encyclopedia Circle Fremont CA 94538 tel: 510 897 4250 fax: 510 979 0189 mobile: 510 676 6312 ------------------------------------ -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Wenger, George M. Sent: Monday, September 12, 2005 4:57 PM To: [log in to unmask] Subject: Re: [TN] raised vias... Michael, I've taken a closer look at the raised via photo on Steve's site and I agree the board does appear to have HASL surface finish and a cross section should eliminate any guess work as to the cause for the raised via. I would be more worried with Layer 1 copper plating attachment to the via barrel plating than I would to the via fill material. Regards, George George M. Wenger, Andrew Corporation Reliability / FMA Engineer Base Station & Subsystems Group 40 Technology Drive, Warren, NJ 07059 (908) 546-4531 [log in to unmask] -----Original Message----- From: Mcmaster, Michael [mailto:[log in to unmask]] Sent: Monday, September 12, 2005 7:44 PM To: 'TechNet E-Mail Forum'; Wenger, George M. Subject: RE: [TN] raised vias... I would bet they were planarized down to the surface initially. It looks like the board has HASL surface finish and I would bet the resin in the vias expanded, pushing out the copper which then stayed there. Cross section should show whether the copper is still attached to the via fill. This is one of the problems of trying to use prepreg resin to fill vias. The resins meant to fill vias generally give better plating adhesion and don't show this "bullet hole" appearance. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M. Sent: Monday, September 12, 2005 4:36 PM To: [log in to unmask] Subject: Re: [TN] raised vias... Valerie, I think I agree with you that the bumps are prepreg and that the fabricator needs to plane the prepreg back down to the copper level. However, the problem with doing that is control of the plane operation so it doesn't remove too much copper and weaken the Layer 1 via knees. My suggestion to Steve is to cross section some of the raised vias and examine the integrity of the Layer 1 plating to the blind via barrel plating. And I would also repeat the cross sectioning process on reflowed bare boards after the fabricator eliminates the raise vias to insure he has good interconnect integrity/reliability. Regards, George George M. Wenger, Andrew Corporation Reliability / FMA Engineer Base Station & Subsystems Group 40 Technology Drive, Warren, NJ 07059 (908) 546-4531 [log in to unmask] -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Valerie St.Cyr Sent: Monday, September 12, 2005 7:18 PM To: [log in to unmask] Subject: Re: [TN] raised vias... Nope .... those vias are filled with prepreg from the lamination cycle. It had nowhere to go ... it melts and floods up the hole, capillary action. The fabricator should have planed the surfaces to bring the prepreg back down level to the copper layer. Valerie stephen gregory Sent by: TechNet 09/12/2005 07:02 PM Please respond to TechNet E-Mail Forum; Please respond to stephen gregory To: [log in to unmask] cc: Subject: Re: [TN] raised vias... Hi Everyone! I'm home now, but I can answer some of the questions. The picture of the board is as it was given to us. It hasn't been through reflow...this is how the bare board looks. The vias aren't filled.This is a 10-layer board that is made from IPC-4101/26 (GF) material. BUT, there is 5-layers on one side of a .045" thick copper core, and on the other side of the core is the other 5-layers. There is double-sided SMT on the board, and both sides have the "anthills" like you see in the picture. Pretty strange, huh? -Steve Gregory- "Brooks,Bill" wrote: I'm just passing the message on... it's Steve's board... 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