Yep, effectively solder flows towards heat. At least it melts first in the hottest area and then, now being mobile, surface tension/wetting forces will tend to pull it there. The flux, which is temperature activated, will also be most effective initially in the first heated areas. Eventually heated area becomes uniform, all the solder will melt, and then things may even up [as much as the geometry of wettable area and remaining flux effectiveness allows]. Regards Mike -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner Sent: Monday, June 28, 2010 7:11 PM To: [log in to unmask] Subject: Re: [TN] QFP short at top of the leads Hi, That dull gray makes me thing of reflow without any flux. Was that SAC paste with PbSn on the parts? If so maybe the PbSn reflowed first and for some reason was pulled to the body. (Does solder really flow towards the heat?) Bob Kondner -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Jerry Dengler Sent: Monday, June 28, 2010 7:40 AM To: [log in to unmask] Subject: Re: [TN] QFP short at top of the leads Jowan, Was this part dipped in solder before placing? It looks like solder has coated the whole lead right up to the body. Jerry -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Iven, Jowan Sent: Monday, June 28, 2010 5:08 AM To: [log in to unmask] Subject: [TN] QFP short at top of the leads Has anyone ever seen a QFP where shorts occur after soldering at the top of the leads? And the leads look pretty dull after soldering. Any ideas? A picture is available at http://ipc-technet.groupsite.com/uploads/galleries/x/000/020/5ba/technet 01.jpg Jowan Iven ************************************************************************ ********************** This e-mail and any attachment is confidential and may be legally privileged or otherwise protected from disclosure. If you are not the intended recipient, please notify the sender immediately by returning this e-mail. Neways Electronics NV is not responsible for the improper or incomplete transmission of any e-mail, or for any delay in its receipt. ************************************************************************ ********************** ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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