BDMICRO SMT SOLDERING TUTORIAL
Are you worried about not being able to solder the surface mount
components onto the MAVRIC-IB and MAVRIC-IIB board(s)? If so, please read
the following quick tutorial. I was worried about it too, but
with a few simple techniques and the right tools, anyone can do
Soldering the ATmega128
The following video demonstrates the technique. Click on the
image below to view the video (4.3 MB).
The basic technique for soldering the ATmega128 TQFP package as
well as SOIC and other SMD chips is as follows:
Soldering 0603 Sized Surface Mount Resistors and Capacitors
Use small diameter solder - 0.015 inch diameter works well
most SMD parts. The solder I use is Digikey part
Next, make sure that your soldering iron is hot enough. If
the iron is not hot enough, you will have trouble.
While not absolutely required, a good temperature
controlled iron can make the process easier. You
don't have to pay a lot of money for one, the one in the
photo here was found on e-bay for a good price. Expect to
pay around $40 to $100 or so new.
Carefully position the ATmega128 over the pads.
With the ATmega128 in position, keep it in position with
your finger. Use flux to wet the one or two sides of the
TQFP package that you can reach without lifting your other
finger. Heat several of the pins on the part to tack it in
place. Because of the flux, the existing solder on the PCB
pads will wick up on the leads and hold them in place
You can now lift your finger. Apply flux the other side of
the chip. If it's a quad chip, flux the other three
sides. Using the small diameter solder, lay the solder
right across all the pins of a side so the solder is on top
of the pins parallel to the chip edge. Drag the hot iron
across that row, contacting both the solder and the leads
(lightly). You have to have the flux on there otherwise it
won't work very well. Physics is a wonderful thing - just
the right amount of solder will flow around each pin, the
flux is the key.
If you do happen to cause a solder bridge, just add a bit
more flux, sponge off your iron, then use the iron to wick
up the bridge. Alternatively, just drag the iron over the
bridge and redistribute its solder across the other pins or
dump it into a nearby via, no need for solder braid.
Repeat for the other chips on the board. The same
technique works with the SOIC chips and other pinned SMD
The 0603 sized surface mount resitors and capacitors are quite
small but they can be easily soldered by hand. I've found that
the easiest way to solder these is as follows:
Notes for Success
The cap we'll solder is capacitor C3 on the MAVRIC board located below. This is a
0603 sized .1uF bypass cap for the DS1307Z real time clock.
Begin by preparing one pad by melting a small amount of solder onto it.
This will create a raised nub of solder on the pad as shown.
Next, use tweezers to position the cap over it's location:
Use the fingernail of the index finger of your free
hand to hold the part in place while you heat the solder
nub that you created a moment ago:
The solder nub will melt and the part will sink into
position and be held securely:
Be sure and use your fingernail which has no nerves
and you won't burn yourself. If you have really short
fingernails, perhaps use an exacto knife to hold the part
in place for this step.
Now just use your iron and a small amount of solder to
solder the other end:
Use your solder sparingly, it only takes a small amount per
pin. Bridging is the result of using too much solder.
Use a small diameter solder (0.015 inches is good) for the
small pins. It is much easier to control the amount of
solder being applied when using the small diameter.
Iron temperature plays an important part. If your iron is
not hot enough, the process will be very difficult.
However, don't get it too hot, otherwise you could damage
the part. I've found that 630 to 680 degrees F works well
for my iron, but the ideal temperature will probably vary
from iron to iron and even the type of solder used. It may
be a good idea to give the part a short rest for a few
seconds every few pins to cool down a bit.
Using these simple techniques, you can successfully mount the SMT
parts to the MAVRIC-IB and MAVRIC-IIB boards and save a few bucks.