[Elecraft] desoldering

[Henry Gardiner]

At 04:22 PM 3/24/04, you wrote:
>Other than the Hakko 808, or perhaps riggin up my own pump to a RS desoldering
>iron, does anyone else suggest an affordable (< $500) desoldering iron?

For my own use I bought a very second-hand solder/desolder Pace MBT-200 
which has an internal air pump for $100 from a guy at the hamfest in 
Arlington, TX.  He didn't know how to or didn't want to repair it.  You 
might check around your area.  This unit required some repair work on 
connector pins, handpiece and the pump.  But no new parts outside of 
filters.  It's nice because typically components fall out as I desolder the 
last pin if I'm not holding the component with a spare finger.  A resistor 
pack would be out in 30 seconds with a little extra time for partially 
bent-over pins.  Munged eyelets are very rare.  I repair a lot of 
production errors at work.
   Using these Pace desolderers requires some discipline.  Most techs I 
deal with never catch on.  They pretend the non-self heated desolderers 
work but actually the techs just remove most of the solder and accept 
sometimes yanking out the barrel of the plated-through hole.  Then they 
resolder the pins of the new component on both sides of the board as 
needed.  Totally unprofessional and it looks totally unprofessional.  It's 
also slow.
   1. Read the manual for the correct procedure to use.
   2. Make a reaming tool out of a paper clip or wire to periodically clear 
out the junk from the tip and heater body.  Pace supplies more official 
reaming tools.
   3. Don't try to nurse a tip to the bitter end.  They can be reshaped, 
but there's an increased tendency to scratch the substrate around the 
eyelet and the thermal transfer will remain impaired.  Some of the Pace 
tips don't cost much.
   3.5  Don't have more than the minimum needed tip length extending from 
the heater body.
   4. Make sure all the needed filters are installed and reasonably clean 
unless you enjoy taking pumps apart.  Solder bits can lodge between sectors 
of the motor commutator.
   5. If the Pace glass cartridge won't slide out because of accumulated 
solder at the input end, try the maximum temperature setting briefly.  Then 
be suspicious you didn't follow step 1.  Be real careful with needle nose 
pliers on the cartridge or it will break.
   6. Another paper clip with a hook at the end will get the metal 
deflector out of the glass cartridge so you can empty the cartridge.

   The air suction plus movement of the component lead around the perimeter 
of the eyelet removes the solder.  Continued suction and motion for a 
couple seconds is needed to cool the cleaned joint so the lead won't 
re-weld to the side of the plated-through hole when the sucker is pulled 
away.  If the lead sticks nonetheless after an apparently successful solder 
extraction, maybe the temperature is too high.  Only after the handpiece is 
withdrawn is the pump turned off.

Henry