Under $20 (USD) Air-Pencil SMD Soldering Iron

by Rob Severson

This is how I created the (probably) worlds-first air-pencil soldering iron for under $20.

On the PICLIST the discussion of surface-mount soldering has often, uh, surfaced. People have talked about using a toaster oven as a reflow oven. With a little effort, this method works. You can pick up a new oven for $50. A used oven even less. This is a nice low-budget solution.

But this is about a different surface-mount soldering method. I have used a hot-air soldering tool at work that melts solder with softly moving air at about 250 degrees Celsius. This cool tool will set you back a cool $1000 or so.

So how can you make one for almost pennies? Well it turned out to be very simple. And inexpensive.

The "Under $20 (USD) Air-Pencil Soldering Iron" is made from a desoldering iron and an aquarium air pump. I purchased a RadioShack® 45-watt desoldering iron (64-2060) for $9.99 (USD) and removed the vacuum bulb. I then attached the air pump (about $8.00) tube to the location that the bulb had occupied. I needed to melt the end of the tube slightly to get it to fit over the end of the metal tube.

At this point if you plug in the iron and pump, the iron will heat and warm air will eventually come out. This air just isn't hot enough to melt solder. But here is the trick to get it to work. Remove the hollow iron tip and stuff a small piece of steel wool into the open end. This will slightly restrict the air flow. But the steel wool will heat to the temperature of the iron and transfer the heat to the stream of air. The steel wool provides more hot surface area for the air stream to interact with. Put the tip back on.

Below are two pictures from a video capture of this setup.

Note: A variety of bulb-type desoldering irons may work for this application.

Note: If you have access to paste-solder this may be easier to use than roll solder. If you use roll, use the thinest that you can find.

Note: Leave the air pump running after you have shut the iron off. This will prevent the hose from melting off. You may wish to add a speed control to the air pump and perhaps a temp control to the iron.

Note: Experiment with the steel wool grade of courseness for most efficient effect. Stainless steel wool has been suggested by Don Hyde for longer life. I have even tested this with brass shavings. Experiment with the amount of wool stuffed into the opening.

Note: If you invert a clothes iron and set your PCB on the hot surface to pre-warm the board, this will assist in the soldering process. The iron can be set to its "coolest" setting.

Note: Please feel free to email me if you have any ideas to add to this application.

This creation is dedicated to my 4-year-old son's fish Sam and Julia, who passed away but donated their pump to science... and to Roman Black who prompted me to prove that this was possible.

Copyright © USBmicro, February 2001 used by permission of the author.

Also check out the Marvy Embossing Heat Tool:
²

It is a self contained hot air tool for crafters. It works great for surface mount device, as well as for flash remelting toner to remove pinholes. The best part is the amazing low cost: about $18! Can't build one for that.

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