The last In-Circuit test strategy created by an outsourced Vendor was like the" blind leading the blind", so maybe I dew. Dewey -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Valerie St.Cyr Sent: Wednesday, April 19, 2006 7:10 AM 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, --------------------------------------------------- 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 ----------------------------------------------------- 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 -----------------------------------------------------