 
| Subject: | |
| From: | |
| Reply To: | TechNet E-Mail Forum. |
| Date: | Mon, 12 Nov 2001 09:16:25 +0100 |
| Content-Type: | text/plain |
| Parts/Attachments: |
|
|
Hi Warren,
What about covering the BGA-via's on both sides, with addition of dedicated testpads on the bottom ?
Daan Terstegge
SMT Centre
Thales Communications
Unclassified mail
Personal Website: http://www.smtinfo.net
>>> <[log in to unmask]> 11/09 9:23 pm >>>
I have seen different ways to address masking small vias (<13mils) under BGA.
cover them with mask prior to HASL top an bottom ( can't we need to ict probe
bottom)
cover top with mask prior to HASL (could cause trapped chemistry in via and
will not allow solder thru, we like the effect on thermal reliability for
environmental extremes)
leave the mask opening only slightly larger than via (tent)
do a post hasl mask to cover over via ( causes 2x the thickness of mask at
overlap, could be a problem with uBGA ball only 14mils dia to start with may
not touch pads)
We use #3 but have problems with rework leaving solder plugged vias that look
like shorts in xray.
If there are some other ideas or thoughts on how to design the via masking under
the BGAs I would like input. Thanks!
---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
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 delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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 1.8d
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 delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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
---------------------------------------------------------------------------------
|
|
|
