[Elecraft] Notes on maintenance of DEsoldering guns

[Tom Hammond NØSS]

Folks:

I offer the following notes (from my personal experience) for those of us 
who have (or may have) desoldering guns.

While my comments are specifically with regard to the Hakko desoldering 
gun, I suspect many, if not all, will equally applicable to most devices of 
this type. Of course, YMMV.

    1. When you are finished using your desoldering gun (for the
       day, or for a while), run the cleaning tool (looks like a
       long, thin wire with a spring on one end) through the
       complete solder path to ensure that nothing is clogging the
       passage. Do this BEFORE you put the device away, or DAILY,
       whichever is applicable. .

       Not only can solder accumulate, but the most damage comes
       from burnt rosin which builds up inside the heating tube.
       Since this is already burned, it will no longer melt (to be
       readily sucked into the catch tube the next use) and thus
       it can quickly clog up the tube. If not REGULARLY cleaned
       out (every 30 or so joints cleaned, especially if there's a
       lot of residue on the joint) it can build up to the point
       that it is VERY difficult to clean out.

       I used my DremelTool to grind the end of this cleaning rod
       down to a screwdriver-like tip. This allows me to twist the
       rod, as I run it in, to more easily loosen accumulated
       residues. It works almost like a drill bit.

    2. Be aware of the temperature setting of your desoldering
       gun. Sometimes, as they come from the manufacturer, the
       temperature may be set quite a bit higher than required. To
       the point of doing damage to PC boards if left on the joint
       too long.

       I normally set my heat range so that I can effectively
       clean out a plated-thru hole in about 2-3 seconds (max.).
       If my gun heats the joint too slowly, I turn it up a bit.
       Sometimes GROUNDED pads (because they can 'sink' heat away
       more quickly) may require either a bit more heat or a
       slightly longer dwell time on the joint before it is
       thoroughly melted.

    3. When using a desoldering gun, once the tip is on the joint
       and the joint is molten, hold the tip flush against the
       board and 'circle' it around the tip of the component lead
       AS you press the trigger.

       What I mean by 'circle' is NOT to spin the gun, but to hold
       the gun in the same position, but move the tip just so that
       the component lead circles around the inside edge of the
       nozzle. This causes the component lead to be moved away
       from the sides of the plated-thru hole and exposes all of
       the hole to the vacuum.

    4. Keep your solder catch tube clean. This is the device which
       holds all of the solder you've removed from the PC board.
       After a period of time, the solder (and the vaporized
       rosin) will build up to the point that it begins to effect
       the gun's ability to sustain a usable vacuum.

       Clean out the catch tube (and any filters, if applicable)
       each day's use, BEFORE you put it away. On Hakko guns, you
       can pop out the catch tube, pull out the aluminum
       pre-filter, and pop off all of the stuck-on solder. At the
       same time, take your finger (or a smooth-edged/dull)
       knife blade) and lightly scrape away any bits of solder
       which have adhered to the inside of the catch tube.

       Check the filter itself. If it appears to be badly clogged
       with the residue of vaporized rosin, clean or replace it.
       Hakko filters are made of what they call 'ceramic paper'
       which can (to some extent) be rejuvenated by a bath in
       alcohol (isopropyl or denatured, NOT drinking!). Allow the
       filter to DRY COMPLETELY before you reinstall it. Filters
       will probably not require any attention for at least
       several HUNDRED desoldered joints. But it never hurts to
       check anyway.

    5. The pre-filter of the Hakko 808 desoldering gun resides
       inside the black (silicone, I think) filter holder. The
       pre-filter resembles a disk with four short,
       equally-placed, arms sticking out.

       I found it rather difficult to reinstall the filter holder
       into the catch tube once the per-filter had been installed
       INTO the filter holder. The 'fit' is close enough that
       pressing this assembly back in was difficult to the point
       of risking damage to the thin walls of the filter holder.

       I solved this problem by using a fine file to take about
       2-3 light passes across end of each of the 'arms' of
       the pre-filter. This does not compromise the effectiveness
       of the pre-filter, yet it allows the pre-filter and the
       filter holder to be VERY easily reinstalled following
       cleaning of the catch tube.

    6. Hakko provides (in it's 'kit' of desoldering gun parts)
       what looks to be a terribly long, thin screwdriver... well,
       it DOES have a screwdriver tip...  This device is another
       cleaning rod, but specifically for use in the heating tube
       of the gun ONLY. It will not fit through the nozzle itself.
       Use this device every 50-100 desoldered joints be first
       removing the nozzle and then passing the rod thru the
       length of the heating tube. You may have to heat the gun up
       in order to use this device. But DO NOT leave the gun
       plugged in for a long time. It heats VERY quickly (20
       seconds without the nozzle attached) and will retain this
       heat more than long enough to clean out the heater tube.

    7. DO NOT, UNDER ANY CIRCUMSTANCES grab hold of EITHER of the
       cleaning rods right after they've been passed thru the
       heating tube... bad things (and bad words) will happen...!
       Been there, done that... won't do it again... until the
       next time I forget.

    8. Note that Hakko offers several different nozzle sizes and
       styles, a couple of which I bought for "special occasions":

       A1007 - Similar to the 1.0mm (.039") diameter tip supplied
          with the gun, but with a 1.6mm (.062") diameter hole.
          this addresses many of the larger leads and lugs found
          in Elecraft kits. Though I did not purchase it, the
          model A1396 nozzle offers a 2.3mm (.09") I.D. orifice
          as well.

       A1394 - A very long and slender nozzle with a 1.0mm (0.04")
          inside diameter and a 2.1mm (0.083") outer diameter tip.
          This allows me to get to those components which are
          mounted from the BOTTOM of the PC board and which cannot
          be easily accessed with the 'fatter' (original
          equipment) nozzles. Gets down between adjacent
          components with ease. This top is not cheap, running
          about $13.

    9. Hakko offers 'drill bits', and a pin vise holder for use
       when you REALLY have an immovable accumulation of junk in
       the nozzle or heating tube. There are different bits for
       each I.D. of nozzle. This having been said, these bits and
       pin vise are pretty 'pricey' if purchased from Hakko. But
       you can just as easily find the pin vise and the drill bits
       'wire gauge' (also metric and inch dimension) diameters at
       both hobby and some of the better hardware stores for a LOT
       less cost.

   10. Get to 'know' your desoldering tool. LISTEN to what it's
       saying as it works. Soon, you'll be able to hear whether
       it's working properly or not. The sound is different when
       it's clogged up or when the joint hasn't been thoroughly
       heated or cleared.

       Sometimes, if you can't readily clear a hole, ADD a little
       more solder to the joint and then try again. Often it's
       nothing more than a case of there not being enough solder
       available for the nozzle to heat and transfer that heat the
       the rest of the joint. Of course, if the problem hole is
       GROUNDED, you may require a bit more heat, or a slightly
       longer dwell time before you hit the button.


That's all folks... I'm sure there are a number of things I've missed. 
Hopefully some of you who have more experience with this type of 
desoldering tool will now chime in and add to this list, for the benefit of 
all of us.

73,

Tom Hammond   N0SS