■ FIGURE 7. PCB ready for
Etch the board
using the instructions
supplied with the etching chemical. Be sure to
use personal protective
equipment. You don’t
want to splash chemicals into your eyes. Also,
the chemical will stain
everything it touches, including your
hands and clothes. Ferric chloride
does not come out in the wash!
After the board is etched, you
can remove the toner mask using
mechanical or chemical means. Nail
polish remover (acetone) and a green
scouring pad do the trick. It takes a bit
of elbow grease to remove the toner.
You may want to experiment with
more aggressive chemicals.
prototypes, it is best to build and debug
as you go. Small sections are much easier to debug than entire circuit boards.
The finished product will look like
the board in Figure 3. Notice that there
are open copper runs. You can leave
these as they are, run solder over the
runs, or apply a sealant to the entire
board. Personally, I leave them as they
are since it doesn’t affect performance.
Once you have a clean board, you
are ready to solder your SMT components. It doesn’t take long to acquire soldering skills. Here’s a quick run down:
1. Apply a small amount of flux to the
pads you are going to solder
2. Apply a small amount of solder to one
pad (for ICs, use pin 1).
3. Remove the SMT component from its
protective tape and position the
part using tweezers.
4. Remelt the solder from Step 2 while
holding the part with tweezers. The
part will sink into the solder.
5. Solder the other connections.
6. Use a solder wick to remove solder
7. Clean the flux off using a solvent
Each of us has a stash of components we have collected over the
years. A good way to procure your
SMT components is to purchase kits. I
purchased an assortment of 1/4W
(1206) 5% resistors from Digi-Key (part
#PHE2A-KIT). This has a good value.
You may also scavenge some SMT
components from old equipment. Be
sure to test them before you use them.
I trust this article demonstrates that
you can build and design with SMT
devices. Once you start, you will
appreciate the speed at which you can
make a quality circuit. You will also reap
the benefit of being able to use many of
the newer integrated circuits. NV
Since most of your boards will be
One company — SchmartBoard
— has revolutionized electronic
circuit prototyping using surface
mount components. Check out
what they have to offer at
■ Aaron Dahlen is devoted to his
family and country. He serves in
the US Military and is currently
somewhere above the Artic Circle. In
the little spare time he has, he
enjoys experimenting and designing
electronics. You may reach him via
email at APDahlen@gmail.com
December 2007 71