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or clothing. Store in a plastic container. Wear eye protection and rub-
ber gloves. PDA Robotics
Directions: If you use ferric chloride cold, it will take a long time to
etch the board. To speed up etching, heat the solution. A simple way
of doing this is to immerse the ferric chloride bottle or jug in hot water,
adding or changing the water to keep it hot. A thermostat-controlled
crock pot is also an effective way to heat ferric chloride, as are ther-
mostatically controlled submersible heaters—glass-enclosed such as
an aquarium heater. An ideal etching temperature is 50°C (120°F). Be
careful not to overheat it. The absolute maximum working tempera-
ture is approximately 57°C (135°F). The warmer the etch solution, the
faster the 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 aquarium “air stone.”

The etching process can be assisted by brushing the unwanted resist
with a foam brush while the board is submerged in the ferric chloride.
I found that rocking the board back and forth in the pan by holding it
by the edges with rubber gloves on works well. The ferric chloride can
be kept warm by placing the glass basin on a stove element set to low.
Turn on the fume hood to expel any fumes.

After the etching process is completed, wash the board thoroughly
under running water. Do not remove the remaining resist protecting
your circuit or image. It protects the copper from oxidation.

Figure 6.5
Circuit board ready
for etching.

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