[Elecraft] SMT and the K3 - Nerves

[Don Wilhelm]

Mel,

Having the "right tools" certainly makes the task easier, and with the 
right tools, a task like changing a resistor is almost as easy as 
"falling off a log".

There are many who do not have the "right tools" at hand, and purchasing 
the "right tools" for just one task is not a reasonable solution if 
economics are to be considered.

So, there are OK alternate techniques, such as heating both ends of the 
component at the same time as Alan Bloom pointed out, or my usual 
solution of heating both ends alternately in rapid succession until the 
component moves, or the two soldering iron solution.  These all work, 
and IMHO have less probability for damage to the PC board than 
physically breaking the component in two.

Look at the size of the traces.  If the traces cover a relatively large 
area, then breaking the component will be OK, but if the traces are thin 
and the solder pads small,  breaking the component can damage the 
board.  Look at it first - the possibility of board damage comes under 
the category of "it all depends ..."

I do not have the "right tools" for SMD device removal, and it is not 
nice to get the second soldering iron fired up.  But, I will offer yet 
another technique that I use frequently - my pocket knife has a very 
thin blade edge (a single edged razor blade would serve a a substitute), 
and I can heat one end of a component and start (not force) the blade 
between the board and the component - OK, knife blade in - go heat the 
other end and it will pop right off.  Caution, do not attempt this with 
a knife blade honed at a knife "factory edge" angle - I sharpen my 
blades to an angle of about 15 degrees. so the knife edge makes a 
slow-rising ramp for the component.  That angle is similar to the angle 
found on a single edge razor blade (an Exacto knife blade has a steeper 
angle than I use on my knife blades - I do use diamond hones to produce 
the knife edge, final grit is 1200, so the edge has some "polish" to it).

73,
Don W3FPR

On 4/19/2012 6:37 PM, Mel Farrer wrote:
> Well, you are both right and wrong.  Sorry,  The correct way to remove an SMT component is with the right tools.  Most of the accepted makers of SMT soldering and unsoldering equipment have gone to great lengths in minimalizing the undesirable effects of over heating by having available tips that match the size of the component like a saddle. The tip touches both the ends of the component and the solder bridge to loosen the part and with a vacuum pick either in the wand or standing by to suck the part of the PCB.  Honestly it is the most desirable way for minimum impact to the PCB trace.  In a off site situation I have done the leap frog on both ends and with a dental pick lifted one side then with tweezers hold the part and unsolder the offending side. The absolute worst why is to try and pry the part up while overheating one end.  Ugly.  Sorry, guys the had to give my two bits worth.  Buy the way the right tips are far less expensive than a
>   damaged PCB.
>
> Mel, K6KBE
>
> Mel
>
> --- On Thu, 4/19/12, Alan Bloom<n1al at sonic.net>  wrote:
>
> From: Alan Bloom<n1al at sonic.net>
> Subject: Re: [Elecraft] SMT and the K3 - Nerves
> To: "Ron D'Eau Claire"<ron at cobi.biz>
> Cc: "'Elecraft Discussion List'"<elecraft at mailman.qth.net>
> Date: Thursday, April 19, 2012, 2:58 PM
>
> On Thu, 2012-04-19 at 14:23 -0700, Ron D'Eau Claire wrote:
>
>> I have removed hundreds of two-terminal SMDs both by cutting them in half or
>> by unsoldering one end at a time and lifting the part with never any damage
>> to the pcb.
> On most two-terminal SMD parts (resistors, capacitors, etc.), the solder
> terminal on each end extends on both sides (top and bottom).  So the way
> I generally remove them is to tin the top of each contact with a little
> solder and then lay the soldering iron tip across the top of the entire
> part so that it heats both ends at the same time.  Once the solder
> melts, you can push the part off the pads with a toothpick, Exacto
> knife, whatever.
>
>> Good light and your favorite magnifiers (if needed) to see clearly are
>> essential.
> In my experience, being able to see the darn thing clearly is really the
> key to successful SMT work.  I have a binocular microscope with built in
> light that I bought brand new for about $300.  Whatever you use, make
> sure to have a bright light, and some form of magnification is very
> useful for those of us with middle-aged (or greater) eyes.
>
> Alan N1AL
>
>
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