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Amphibionics 02 3/24/03 8:08 AM Page 21
Chapter 2 / Printed Circuit Board Fabrication
lation is very important. Use only glass or plastic contain-
ers. Keep out of reach of children. May cause burns or
stain. Avoid contact with skin, eyes, or clothing. Store in
plastic container. Wear eye protection and rubber gloves.
If you use cold ferric chloride, it will take a long time to etch
the board. To speed up the etching process, heat up the solu-
tion. A simple way of doing this is to immerse the ferric chlo-
ride bottle or jug in hot water, adding or changing the water
to keep it heating. A thermostat-controlled crock pot is also
an effective way to heat ferric chloride, as are thermostati-
cally controlled submersible heaters—(glass enclosed, such
as an aquarium heater). An ideal etching temperature is 50°C
(120°F). Be careful not to overheat the ferric chloride. The
absolute maximum working temperature is about 57°C
(135°F). The warmer your etch solution, the faster your
boards will etch. Ferric chloride solution can be used over
and over again, until it becomes saturated with copper. As
the solution becomes more saturated, the etching time will
increase. Agitation assists in removing unwanted copper
faster. This can be accomplished by using air bubbles from
two aquarium air wands with an aquarium air pump. Do not
use an aquarium air stone. The etching process can be assist-
ed by brushing the unwanted resist with a foam brush while
the board is submerged in the ferric chloride. After the etch-
ing process is completed, wash the board thoroughly under
running water. Do not remove the remaining resist protecting
your circuit or image, as it protects the copper from oxida-
tion. If you require it to be removed, use a solvent cleaner.
Figure 2.3 shows an etched board ready for drilling.
5. Drilling and parts placement—Use a 1/32-inch drill bit to
drill all the component holes on the PCB. Drill the holes for
larger components with a 3/64-inch bit where indicated. Drill
any holes that will be used to mount the circuit board at this

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