Hi, Dave
We tack solder certain components frequently, as we have certain components that get underfilled or are mounted with special heat transfer slugs, etc.
For the underfilled parts, we need to apply the underfill first, tack solder two or 4 leads to hold the component in place while the underfill cures, then go back and flux and solder these parts.
We need to train and certify the operators in this process, and they need to know to take special care to completely reflow the leads previously tack soldered, this time with flux, along with the rest of the leads.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Sunday, October 09, 2011 9:33 PM
To: [log in to unmask]
Subject: [TN] The Use of Tack Soldering

Hi folks! I am looking for your opinions and information on tack soldering 
for holding components in position for wave or selective soldering 
processes. I know that tack soldering can result in some void and/or 
insufficient solder joint defects. Does any know of any published studies 
on tack soldering or have any experiences they can share? If you do use 
tack soldering, is there any technique or tack configuration that you use 
that eliminates/reduces defects? 

TIA

Dave Hillman
Rockwell Collins
[log in to unmask]


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