[DEMI] Re: [Microwave] Soldering pipe caps on DEMI 10 GHz Xvtr board

[Zack Widup]

On Mon, 23 Jul 2001, Bob Gormley wrote:

> DEMI 10 GHz transverter builders:
> 
> I recently purchased the DEMI 10 GHz transverter through the NTMS project.
> During the assembly of my DEMI 10 GHz transverter, I came to the part about
> soldering the pipe caps to the pcb with a propane torch. I was a little 
> uncomfortable with this method without first experimenting with a sample
> pipe cap. First, I cleaned a copper cap with scotchbrite and decided to tin
> the open end with solder. The results, in my estimation, was unacceptable.
> The pipe cap didn't tin very well, due to excessive heat from the torch and
> was all black and nasty. I was not about to destroy my transverter board
> with
> poor soldering and excessive heat from a torch.
> 

I haven't had any problems soldering pipe cap filters.  I haven't built
the DEM/W1GHZ 10 GHz kit but I built his 5760 MHz transverter and the W1VT
10 GHz transverter which use pipe cap filters.  I made my own pc boards
for these projects.

What I did was make sure I had a clean board to start (polishing it with
some regular kitchen cleanser and water seems to work fine) and swiped the
edges of the pipe caps with a file.  Note the tuning of the pipe caps is
primarily a function of diameter and changing the height of the cap by a
few mils doesn't affect them.

I make a loop out of a twisted pair of lengths of solder that will just go
around the bottom of the pipe cap, pinch it slightly so it will fit
tightly around the base of the cap where it meets the board, and then
gently and slowly heat the pipe cap with a torch until the solder just
starts to melt. I do that by just applying the flame to the pipe cap for a
fraction of a second, then moving it away for a couple seconds, then
repeating. Then I keep warming the pipe cap slightly until the solder
flows uniformly around the pipe cap and onto the board.  

This method has worked perfectly for me every time.  If you haven't
done it before, it's probably a good idea to practice it a few times with
scrap pipe caps and board pieces so you can get the "feel" for how it
works.  Make sure the scrap pipe caps have a hole in the top to keep the
expanding air from blowing out through the solder!

Zack W9SZ



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