SP MSro MUtoty ORpin UFgNAWit TCh E
Back when I was a child,
you could find tube radios
and TVs in second-hand
stores. But — and here’s
the important part — you
couldn’t purchase a new
radio or TV that used
vacuum tubes. The same
thing has happened to
simply don’t use them
anymore. With few
exceptions, they have
been displaced by surface
This “displacement” has become a
problem for us hobbyists. Many
new and powerful integrated circuits
are available, but only in surface
mount technology (SMT) packages.
My solution is to build inexpensive
printed circuit boards (PCBs) using
SMT. These boards can be constructed using readily-available materials.
No special components or tools are
required other than the PCB and the
etching chemical. If you live in a
moderately-sized city, you can pick up
your supplies and begin today.
Why Surface Mount?
circuit boards are faster to build as you
don’t have to drill holes in the circuit
board and you don’t have to bend component leads when you stuff the board.
On the downside, SMT devices
are very small, as seen in Figure 1.
You must have acute vision or a
magnification system to work with
these devices. And lastly, SMTs are an
unfamiliar technology. We all shy
away from things we are not familiar
with. I suspect that is why we don’t
see more SMT designs in Nuts & Volts.
Let’s face the facts: through-hole
68 December 2007
components are a thing of the past.
Like the vacuum tube, they will
gradually disappear from general use
except for specialized applications
such as those requiring high power
(e.g., power transistors, high wattage
resistors, and large storage capacitors).
For the DIY hobbyist, this is a
mixed blessing. SMT devices are
relatively inexpensive and they allow us
to design smaller circuits. The newly
available SMT chips are amazing and
getting better every day. It’s hard to
believe that you can have a 16-bit
microcontroller today for a few dollars!
SMT has the potential to perform better
at higher frequencies due to the
reduced lead length. Finally, SMT
Surface mount technology has