David,

     For a number of years we had the misfortune of having to process a
     flexi circuit onto FR4 daughter/mother boards.  My experience is that
     it's a pain in the proverbial - we since shot the designer.  We used a
     Rossell (Swiss made) fully automated m/c.  The flexi was 15 cm with a
     0.05" pitch pads.

     The problems noted over the years were:

     Difficult to get a consistent thermal profile needed for batch
     sampling of the process - we tried a myriad of different techniques.

     Warpage in the FR4 was a constant problem - often open circuits.

     Variation in different batches of flexi's - causing pad alignment
     problems.

     Overall the process was flawed with problems.  In the end we hand
     soldered them & guess what? all the open circuits went away.  Various
     reliability trials proved it successful.

     Moral of the story, hot bar soldering - knock it on the head!

     I'm sure this will provoke a response from all the die-hards of hot
     bar soldering but that's my 3 cents worth.

     P.s If you still want a supplier, try Karl Benz
     ([log in to unmask]) he's extremely helpful and very passionate
     about hot bar soldering.

     Advise on flexi's - keep the design small.

     Iain.


______________________________ Reply Separator _________________________________
Subject: [TN] Hot Bar Soldering
Author:  david.bruni ([log in to unmask]) at Internet
Date:    10/6/98 3:24 PM


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     A recent SMT magazine contained an article on hot bar soldering.  I am
     searching for information on this process.

     1) Equipment and manufacturers
     2) Process
     3) Design Guidelines

     If anyone is currently using this process or has experience with it
     and could provide me with some information I would appreciate it.

     -David Bruni
     [log in to unmask]

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