[hpsdr] Atlas soldering hints

[Bob Fish K6GGO]

Hi All.
You may want to pay a visit to this guy's website. I am in the process 
of building the Spectrum Analyzer kit that he sells. He has a tutorial 
there for a SMT soldering technique using a hot air gun and hot plate 
that works very well indeed. He will sell you a syringe full of solder 
paste for 5 dollars. Solder paste is (IMHO) the secret to the whole 
thing. No tinning required, just put a small amount of paste on each 
pad, squish the components down into the paste and heat with hot air 
until the solder reflows. The component even centers itself on the pads 
due to the surface tension of the solder. Best technique I have seen 
that didn't involve buying a 2500 dollar reflow oven  Nice guy too, very 
helpfull. The spectrum analyzer is pretty cool also, but we aren't going 
to be needing one of those are we?

Here is his website,
KD5SSJ at zianet.com

Bob   K6GGO

Mike Naruta wrote:

>***** High Performance Software Defined Radio Discussion List *****
>
>Thanks to the SDR group, I have done my first
>foray into surface-mount soldering.  Here's
>some hints that worked for me.
>
>
>I use a lighted magnifying device like the
>GC Electronics 22-423.  I can get up close,
>there's lots of light, I can take my glasses
>off to take advantage of my nearsightedness
>without worrying about solder or flux
>splashing into my eye, and it directs the
>flux smoke away from my face.
>
>I use a temperature-controlled soldering iron.
>This is terrific.  My old irons were always too
>hot.  And different heats are useful for the
>different components.  The by-pass capacitors,
>for example, work best for me at 325 C (620 F).
>The DIN connector pins at 350 C (660 F).  The
>LEDs below 315 C (600 F).  (Lead-Tin solder)
>
>Thanks, guys, for the intro to the water-soluble
>flux.  This made cleanup a dream.  I just held
>the board under the faucet and scrubbed with a
>toothbrush.  All the flux came off and it looks
>professional.  The Kester solder I'm using is
>24-6337-6422.  (63/37, 0.015, water-soluble).
>
>I also hit the board and connector pins with a
>felt-tip flux pen (Kester 2331-ZX).  Watch out
>for the manufacture date on the flux pens; I got
>a batch with about 2/3 of their shelf life gone.
>
>Note:  This flux is flammable.  I excitedly
>discovered the flame going up a piece of wire
>that I was tinning.
>
>Put a large sheet of blank paper under your work
>area.  This helps when you drop a part.  You will
>drop a part.  Oh, also clean the floor before you
>start.  I gave up on a capacitor I dropped on the
>floor.  Sure glad that I ordered extra parts for
>my Atlas.  I lost two capacitors; one that hit the
>floor and one that arced off towards the scopes.
>
>For holding down the SMDs, I use an old push-pin.
>I use tweezers to position the SMD, center the
>point of the pin on the SMD and apply moderate
>pressure to hold it while soldering.
>
>Tweezers with a bent end are more comfortable.
>
>A way to hold the circuit board stationary is a must.
>
>I tried tinning the pad with a blob of solder first,
>but that gave an uneven surface.  This caused more
>of a Tiddlywinks effect on the SMD.  I tried my
>dual-iron tweezer, but I had trouble getting a good
>position on the SMD and looked like the SMD got
>very hot.  The tweezer irons are great for removing
>soldered SMDs.
>
>I tried laying a small, cut piece of solder next to
>the SMD while heating it, but spent a lot of time
>fussing with the solder and SMD to get them lined-up
>first.  I don't have access to soldering paste.
>
>The technique I settled into is to use the residual
>solder on the SMD to tack one end into place by
>putting the iron against the pad and SMD.  Then,
>after a cooling period, apply solder to the other
>end of the SMD.
>
>Note:  Too much heat and the other end de-solders
>the tacked side and you have an SMD on the loose.
>
>Note:  It takes LESS solder than you expect.
>
>Note:  The LEDs just have Gold plating, no solder,
>so you need to add some solder to the pad first.
>
>After the soldered side cools, you can go back to
>the original side and solder it.
>
>Do not dwell on the connection with your iron.
>It is tiny and you're putting a lot of heat on it.
>That's why you turn down the temperature.  I saw no
>signs of pads lifting.  For the DIN connector pins,
>if you have the iron on the connection for more
>than two seconds, you need to change something.
>
>For the DIN connectors, I used a screw, lock washer,
>and nut to attach them to the board first.  The plastic
>of the DIN connector probably has enough yield to hold
>the nut on, but why take chances.
>
>I started on the center row of pins, soldering every
>other pin, then came back and soldered the skipped pins.
>This helped spread the heating effect, but probably
>wasn't necessary.  Then I when down one side and
>alternated pins again.  By having the alternating
>pattern, it helped distract me from the tedious task.
>
>Do not be in a hurry to solder the pins.  Take your
>time with each one.  As I learned from manufacturing,
>inspection is only about 50% effective.  It will be
>much harder to diagnose an locate a faulty connection,
>than to focus on each one the first time.  Give
>yourself breaks.  This is supposed to be fun.
>
>Thanks SO much to the great folks in the group who
>developed this and encourage us to do it ourselves.
>What an exciting time in amateur radio!
>
>
>Check out photos of my soldering stuff at HamSDR.com
>< http://www.hamsdr.com/profile.aspx?id=76 >
>
>Mike - AA8K
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