I would think that the people with most experience with that (which I wouldn't do either) would be the mobile telephone guys. Any of them on the forum? John John Burke Senior Manager - Operations , Optichron [log in to unmask] W: 510 249 5233 M: 408 515 4992 http://www.optichron.com Profile: https://www.linkedin.com/e/fps/2665502/ -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Valerie St.Cyr Sent: Wednesday, April 19, 2006 8:33 AM To: [log in to unmask] Subject: Re: [TN] Question re Test Probe and blind microvia I don't want to allow it, the Test development engineer doesn't want to allow it. But we have no data at all one way or the other, and it would take some time to make up a DOE, get samples fabricated, make a test fixture for this experiment etc etc... They want an answer and preferably one with some amount of experience informing the decision..... so, just trying to see if anyone has tried it. Valerie Rex Waygood <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 04/19/2006 10:28 AM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Rex Waygood <[log in to unmask]> To [log in to unmask] cc Subject Re: [TN] Question re Test Probe and blind microvia I will be interested to read the replies of others. We've never probed microvias but as vias in general are probably the least reliable part of a pcb and pcbs often the least reliable part of an assembly.............do you want to be "hitting it with a LOT of force"???? Our approach is to avoid probe testing on vias, never yet contemplated a microvia. Rex -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Valerie St.Cyr Sent: 19 April 2006 15:10 To: [log in to unmask] Subject: [TN] Question re Test Probe and blind microvia All, I have a question: have any of you first hand experience with allowing blind microvias to be used as test points for In-circuit or Functional Test? The Engineer would like to probe a microvia to eliminate the stub we would normally have from a through hole via used as a test point. I don't know if that should be avoided. The probes we used are either "spear" or "blade" tips; I am talking about probing the loaded board, so this means probing after the board has seen 3 or maybe 4 reflows; the microvia starting laser ablated diameter is typically .006"; if it is a Layer 1 to Layer 2 it is .003" or .004" deep (we used prepreg in that opening, no RCC); if it is Layer 1 to Layer 3, the depth could increase by anywhere from another .0035" to .0055"ish. Our plating specification is IPC6012A Class 3. Our intention would be to drop that blind via in a very large pad, much larger than normal for a blind via; then paste it so it is closed up when we go to probe. That will keep the probe from directly piercing the sidewall plating or the hole knee. Which leaves, I think, the question of how well the plated copper is adhered to the copper foil capture pad - we will be hitting it with a LOT of force - will that mechanical stress cause a de-bonding or weaken that bond ? What if the board needs to be retested and retested if there is a fault and we have to do repetitive debug? So, anyone with experience probing to microvias, your knowledge would help us a lot. Thank you, Valerie --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------