We have used this technology for assembly of PTHs on PWAs that are 
otherwise mostly SMD (e.g. for PTH connectors).  Typically the paste 
is applied using a syringe and the PWA reflowed in vapor phase.  

Another option is the use of solder preforms (most solder vendors make 
preforms, Indium Corp. seems to have quite a few formats to choose 
from).  Interestingly enough, vapor phase was initially invented and 
used for soldering large motherboards (PTH) and the SMD applications 
came later.

Some cautions re reflow soldering of PTH devices:
     * Many PTH devices aren't meant to see the temperatures 
associated with reflow assembly (e.g. dwells for 30-90 seconds above 
360F with a "top end" of 420F)

     * The "cleanability" of rosin fluxes decreases with increasing 
reflow time (i.e. the process that removes an RMA flux after wave 
solder may not be adequate after vapor phase).

Hope this helps.

Jim Maguire
Principal Engineer, E/E M&P
Boeing Defense & Space Group
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______________________________ Reply Separator _________________________________
Subject: Paste in hole
Author:  [log in to unmask] at esdigate
Date:    8/16/95 1:28 PM


Hi,

We are interested in assembly alternatives for components requiring wave 
soldering. The option of "paste in hole" was suggested. Does anyone have 
any experience in using "paste in hole" instead of conventional wave 
soldering for assembly of through hole components such as PGAs or 
connectors?  Any related information, e.g. published papers, reference, or 
standards for this manufacturing technique will help.  Thanks in advance.

Tom Chung