to provide a visual reference for the
sizes of the SMDs, I included a
standard PICAXE-08M2 in a DIP
package on the extreme right.
On the extreme left is a surface-mount single digit seven-segment LED
display, which I only included as one
example of the variety of SMDs that
are currently available.
Let’s take a brief look at each of
the remaining devices, from left to
• LED in a 1206 SMD package.
Resistors, capacitors, diodes, and
many other passive components are
available in several different SMD
sizes — each of which is identified by
a four-digit number. The first two
digits specify the length and the last
two digits specify the width in units
of 0.01”. This red LED is in a 1206
package, i.e., it’s 0.12” long and
• Resistor (10K). This resistor is
also in a 1206 package, so it’s the
same physical size as the LED. In the
photo, I hope you can see the “103”
label that identifies it as a 10K
resistor ( 10 x 10 to the 3rd power).
A 220Ω resistor would be labeled
“221” ( 22 x 10 to the 1st power).
• Resistor (10K). This is another
10K resistor; this time in an 0805
package. Passive devices are also
available in much smaller sizes, but
0805 is the smallest package that I
can easily solder by hand. After I
have had more practice, I may try
the 0603 size if I’m feeling brave.
• Example of an SOT- 23
package. This SMD size is commonly
used for small signal transistors
(including the 2N3904 and 2N3906)
and several logic devices. I have to
confess that I don’t know what this
particular SOT- 23 contains. It’s
labeled “1P,” but I haven’t been able
to find a match among the other
SMDs I’ve been using to practice
soldering. This highlights an
important point. If you intend to do
much work with SMDs, you need to
develop a more organized storage
system than I have at present!
• Voltage regulator, 5V
(LD1117) in an SOT-223 package.
As you can see in the photo, the
SOT-223 package is much larger
than the SOT- 23 package. As a
result, it’s also much easier to solder.
In fact, it’s the easiest of all the
packages shown in Figure 3, and
probably the best place to begin if
you want to try your hand at SMD
soldering. SOT-223 devices are
frequently used for voltage
regulators, power transistors, and
small signal transistors, among other
devices. (The 2N3904 and 2N3906
are available in both SOT- 23 and
There are many other sizes of
SMD packages. Some are larger and
many are smaller — small enough to
make them just about impossible to
solder by hand.
For example, resistors and
capacitors are commonly available
in a 0201 size (0.02” by 0.01”).
Understandably, we’re going to avoid
Now that we have a basic
understanding of the SMD sizes that
we’re discussing, let’s focus on how
to begin to actually solder these
devices. Naturally, my preference was
to begin with strip boards because I
have a large supply of small, leftover
pieces that I can sacrifice to the early
stages of practice.
Figure 4 shows the strip board
placements that I’ve found to be the
easiest to use for soldering the
following four SMD packages: 0805,
1206, SOT-223, and SOT- 23.
Before we discuss each of the
devices, I need to explain the unusual
16 June 2013
■ FIGURE 4.