Hi Wayne - well, "it depends" ($$$$ for Doug's Diet Mt. Dew fund) on the 
component weight versus solder buoyancy. We measured a whole bunch of 
CLCCs is the late 80's as part of a process investigation and found out 
the typical solder joint standoff was 3-4 mils for devices with 20-44 I/O. 
I would suspect that if you measured a statistically valid number of 
samples of a specific component type, you would find that there is a 
typical standoff that is consistently achieved for a given solderpaste 
stencil and pad pattern set. This is a very interesting question as the 
IPC specifications always list "evidence of wetting" and not a specific 
value.

Dave Hillman
Rockwell Collins
[log in to unmask]




"Thayer, Wayne - IIW" <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
05/20/2010 03:17 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
"Thayer, Wayne - IIW" <[log in to unmask]>


To
[log in to unmask]
cc

Subject
[TN] Solder joint height






Should there be a spec for minimum solder joint height for leadless 
components?  An old paper from Werner (mid 90's, I believe) popped up on 
the Internet when I queried this, and Werner has a statement in it that 
joints less than about 50 microns thick are basically all intermetallics, 
but that is not necessarily a bad thing since the intermetallics are 
stronger than the solder (but more brittle).

I figured since we often try to get additional height for BGA joints to 
improve reliability, we should be concerned about QFNs and LCCs.

I grabbed a 1.5mil (37 micron) tungsten rod out of our cleanroom (used for 
clearing clogged wirebond capillaries)and started seeing if I could get 
that under my leadless components.  Couldn't get it under any of them, 
likewise with the QFNs.

Checked Technet archives and didn't see an obvious thread, but maybe I 
didn't have the correct search parameters--if you just enter "height" you 
get a couple of thousand hits.

Wayne Thayer

This e-mail and any files transmitted with it may be proprietary and are 
intended solely for the use of the individual or entity to whom they are 
addressed. If you have received this e-mail in error please notify the 
sender.
Please note that any views or opinions presented in this e-mail are solely 
those of the author and do not necessarily represent those of ITT 
Corporation. The recipient should check this e-mail and any attachments 
for the presence of viruses. ITT accepts no liability for any damage 
caused by any virus transmitted by this e-mail.

______________________________________________________________________
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
-----------------------------------------------------



______________________________________________________________________
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
-----------------------------------------------------