Karl,
Those are excellent points. I'd not seen an OEM put a number on it before. Thanks for the information.
Assuming that the adjacent layer is a "Must Remove" are we looking at design standard 0.2 mm dielectric minimum? Or greater? I don't recall if the design standards address this...?
Another concern is that if there is poor hole-wall adhesion the "must not penetrate" now becomes the end-stake... with no wrap.
In B.R.s case below he mentions rough hole-wall. Assuming this means good adhesion, I would suspect that this would actually increase the reliability of the backdrilled hole.
In any case, I would suggest that B.R. use convection reflow simulation as thermal stress prior to SI assessment. Method 2.6.27 has already proven itself to impart cycling (copper) damage mechanisms not seen in multiple solder floats.
Chris
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Thursday, July 01, 2010 10:59 AM
To: TechNet E-Mail Forum; Chris Mahanna
Subject: Re: [TN] Single PCB backdrilling
Chris,
How reliable a back-drilled hole is depends upon how close the drilling gets to the "Must Not Penetrate" layer. The back-drill bit geometry, drilling parameters and hole size affect how much copper is pushed into the hole ahead of the tip and how much the PTH hole wall is stressed near the tip of the drill bit. A conservative rule of thumb is that the stressed area not be closer than 0.1 MM to the connecting or "Must Not Penetrate" layer.
Regards,
Karl Sauter
On 7/1/2010 6:33 AM, Chris Mahanna wrote:
Backdrills are generally considered a unique structure for which structural integrity after thermal stress shall be assessed to prove conformance.
However, this is not 100% agreed upon and the specifications are rather mute/ambiguous.
Some procurement activities allow conformance assessment from simple electrical test of properly designed test coupons.
I personally have not seen mandated reliability testing on backdrills. I suspect the lack of mandates indicates a general consensus that, in typical use, backdrills are more structurally reliable than their non-backdrilled counterparts.
Chris
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of ??
Sent: Thursday, July 01, 2010 12:01 AM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: [TN] Single PCB backdrilling
Dear Technos,
Anyone use backdrilling tech in a single pcb? We backdrilled a lot of backplanes, but none of them should survive a second reflow process and maybe a wave process.
Here is the questions:
Does the high temperature stress affect the backdrill holes reliability? Two reflow processes and a wave process, Consider the PTHs' drilled edge are rough, maybe they will easy to be damaged by thermal stress.
Will the the rework process of the connector damage the backdrilled holes?
Anything we can do? No HALS? More inner layer connection? Other suggestions?
Thank you so much.
B.R.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Li Yi
H3C R&D DFM Engineer312 Room, Oriental Electronics Bldg., Shangdi Information
Industry Base, Haidian District, Beijing, PRC(100085)
Tel: 8610 82774692
Fax:8610 82774214
www.H3C.com<http://www.H3C.com>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Causion:
This e-mail and its attachments contain confidential information from H3C, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it!
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]<mailto:[log in to unmask]>
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask]<mailto:[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]:<mailto:[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]:<mailto:[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]<mailto:[log in to unmask]> or 847-615-7100 ext.2815
-----------------------------------------------------
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]<mailto:[log in to unmask]>
______________________________________________________________________
--
[cid:[log in to unmask]]<http://www.oracle.com>
Karl Sauter | Principal Engineer
Phone: +14082763207<tel:+14082763207>
4150 Network Circle, MS: SCA12-306 | Santa Clara, California 95054
[cid:[log in to unmask]]<http://www.oracle.com/commitment>Oracle is committed to developing practices and products that help protect the environment
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
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
-----------------------------------------------------
|
