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Friday, February 6, 2015

A De-Soldering Primer By Wayne Burdick


A De-Soldering Primer
By
Wayne Burdick, N6KR

Removing resistors and other parts from double-sided boards is easy and
 fun. After years of careful analysis of my own technique I have documented
 the process. I start with technique #1, below; if that doesn't work, I try
 #2, etc. Good luck!


1. Turn the board over. With one hand behind your back, a wry smile, and
 the confidence of a pet surgeon, simply heat the lead in question and
 listen for the pleasant sound of the component hitting the work bench.


2. Well, that *would* be too easy, wouldn't it. Staying with the solder
 side for now, locate a large solder sucker (the larger the better; it
 should frighten smaller pets when brandished). Heat each joint and deftly
 suck out the solder with a single satisfying Thwop! Listen for the part
 hitting the bench.


3. Didn't fall out, eh? No problem: rummage in that tool bin for a shiny
 new roll of solder wick. Crack open a beer, too, and take a generous swig.
 Wedge that wick in between the lead and pad, heat until you see the solder
 flow nicely onto the wick, and pull it out of the way just in time to see a
 beatiful, black annular ring around your component lead. Nudge each lead
 with your iron and keep your fingers crossed.


4. OK, so you've got a tough customer: small lead, hole just barely
 larger, and a bit of off-color solder that can't be bothered with any of
 the usual techniques. Have another sip of that brew. Vigorously flip the
 board back to the component side. Now grip the lead professionally with
 your most elegant long-nose pliers and hold on tight. Give it a playful
 yank, then pray. Should pop right out.


5. Damn. Finish the beer and get out your brutal, 8" electrician's
 long-nose. Grab the component with gusto this time, buster, then tip the
 board up at a 45. Turn up your soldering station to max and heat that baby
 up on the backside. Pull down hard with the pliers.


6. No go? Hmmmm -- let's get serious. Put the board up directly on its
 edge and hold it in place vertically with your chin. Since your iron is
 suspect by this time, test it for several seconds on the nearest exposed
 skin. (Doing it by accident is just as effective.) Heat the joint with
 *feeling* this time. Lunge and parry. Don't worry about the pad, traces,
 or other parts--this is war! With maximal chin pressure exerted to hold
 the offending board in place, pull the lead out, out, Out!


7. OK, so you "...couldn't get hold of it...," blah blah blah. Fool!
 You must risk everthing at this stage. Insert a small screwdriver under
 the part, and white-knuckle that soldering iron on the obverse. Pry and
 heat until it pops. (Note: It is important to keep in mind the concept of
 "kick-back" should you succeed at this. PC boards are likely to
 wobble, flop, slip, then fling out of your grasp once the offending little
 monster finally lets go, taking test leads and soldering station with it.)


8. So, what kind of inept dweeb are you, anyway? Give up! Clip the part.
 Leave some lead to grab onto and repeat #6 and 7. If your face has turned
 red it is best to shield the work from veiw with your body, then steal a
 quick look behind you to be sure noone is suppressing a giggle as they
 watch this humiliating display.


9A. The lead came out but you STILL have some solder left in the hole?
 Gads. Find another part that you can sacrifice. Press its helpless
 lead into the depressingly small pit you made in the center of the pad.
 Heat the base of the lead until you achieve Punch-Through. Yank and Heat,
 Yank and Heat. Evetually the solder will give up in disgust and the
 sacrificial component lead will slide smoothly, signalling victory.


9B. To your left is a hand drill; to your right is a #60 bit. You know
 what you must do.


10. Now—you brute!— now that you've overheated the pad, broken the trace,
 cracked the component, gouged the board, pitted the tip, blistered the
 skin, wasted a beer, and irrefutably proven once and for all that you
 should have taken up gardening instead, NOW maybe you'll learn the color
 code!
  
;)

 N6KR



Thanks Wayne!  Been there!  Done ALL that!  This brought to mind the time I soldered in a 16 pin logic chip on a double sided board... UPSIDE DOWN.   TRIBAL KNOWLEDGE MY FRIENDS. 


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2 comments:

  1. All electronic wizards have a soldering iron. Gentlemen, my I introduce you to the 'desoldering iron'. Part solder sucker, part soldering iron. http://cpc.farnell.com/duratool/d01849/desolder-iron-sucker/dp/SD01702?in_merch=Featured Products&MER=e-bb45-00001001

    ReplyDelete
  2. Great article. I too have been there and done that.
    When I was doing this professional, many years ago, I had a very nice de-soldering station.
    Not that I have to do much de-soldering when constructing Wayne's creations. The instructions are so clear you rarely get things wrong.
    Thanks for the article Wayne, and thanks to you Bill for the best ham radio blog and podcast on the air.
    73 Gareth - M5KVK
    PS I'm half way through "Adventures" Bill and loving it.

    ReplyDelete

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