a) Redesign the thermal pad  grounding so that it is not fully contacted with the thermal layer.
b) At solder during the SMT process (ensure that the pin is still able to insert into the hole).
c) Increase the preheat to even out the whole board 
d) If the space/distance between chip wave and main is too far, do not turn on the chip wave.

________________________________

From: TechNet on behalf of Charming Chan
Sent: Tue 10/28/2008 8:25 PM
To: [log in to unmask]
Subject: [TN] How to improve solder filling and wetting contact angles for thermal vias at wave soldering process.



Hello TechNet experts,

At the wave soldering process, the solder filling of thermal vias(the via
holes connected with copper plane by thermal pad) can not fulfill the 75%
acceptance spec in IPC-610D. Moreover, at the lead free wave soldering
process, the wetting contact angles of thermal pads exceed 90° often.

My question is how to improve solder filling and wetting contact angles
for thermal via holes? Thanks a lot.

Best Regards
Charming Chan
PCBA Engineer




--------------------------------------------------------
ZTE Information Security Notice: The information contained in this mail is solely property of the sender's organization. This mail communication is confidential. Recipients named above are obligated to maintain secrecy and are not permitted to disclose the contents of this communication to others.
This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the originator of the message. Any views expressed in this message are those of the individual sender.
This message has been scanned for viruses and Spam by ZTE Anti-Spam system.



---------------------------------------------------
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
-----------------------------------------------------