HOW TO MAKE A
PRINTED CIRCUIT BOARD
This is a step-by-step guide on how I
make PCB's.
Producing a PCB in your home can be very
easy with a little practice. There are
many different ways to do it using many different tools. Here is how I do it.
After designing a circuit on breadboard
and making sure it works the way I want it to, I draw the entire circuit on the
computer. The drawing is a reversed
image, for example, if you looked at the image in a mirror it would look
correct. I design the circuit as if the
circuit board material is see-through and I'm looking at it from the component
side. The image will be flipped back to
normal during the transfer process (below).
Any drawing program will work, however, I
prefer using a CAD program. I use an
older program called Corel Draw version 3.0.
The illustration below shows two circuits ready to be created.
If you have access to a laser printer you
can print the image directly onto the transfer film (press-n-peel). If you use an ink jet printer you can print
the circuit onto regular paper, then re-copy it onto the transfer film using a
photocopier, this is the method I use.
The key is the find a way to get the
image onto the transfer film using a toner cartridge type of powder, like the
kind used in photocopiers and laser printers.
The photo above is the result of my HP
Deskjet printout put on a photocopier and then re-copied. This re-copy is used as a template for the
size, shape and position of the transfer film that I will need. Leave the original HP Deskjet printout on
the copy machine. Don't move it because
if you do the template will not be aligned.
Now cut out the shapes you will need.
Tape the transfer film over the images on
the template. Shiny side goes against
the paper so you can print on the dull side of the film. Make sure the tape will not be printed on.
Make another copy of the same HP Deskjet
image onto the same template with the film held in place with tape.
The image will be printed onto the dull
side of the film. Use scissors to cut
the film from the paper template and remove the tape from the film.
The film can now be used to mark the
dimensions of the copper clad board you will need.
When the dimensions are marked, you are
ready to cut the board to the correct shape using a rotary tool with a cutting
wheel installed.
The edges of the board will need to be
sanded with sandpaper. Take
caution not to sand the board too much, you could end up with a board smaller
than the pattern you want to print to it.
Now use fine grit (220) sandpaper to clean the copper. This is
a very important step to ensure the image transfers correctly and adheres to
the copper, especially near the edges and corners!
In the past I have used a small hobby
iron to heat-press the image onto the copper but now I use a hot roller
laminator.
I had to remove the case because the
entry slot in the case made access to the actual laminator difficult. There was about 4 inches of spacing between
the opening of the case and the rollers.
With the case removed there is about 1 inch of spacing between the
opening of the frame to the rollers. I
constructed a simple wood and plastic mount for the laminator frame.
I usually run the board with the film
sitting on top through the laminator twice.
Notice the dull side of the film with the pattern printed on it is
against the copper, the shinny side up.
This reverses the image.
I use a fine point sharpie to fill-in any
areas that did not transfer. The need
to do this is rare now that I use a hot laminator. When I do have problems with transfer, I can usually attribute
this problem to inadequate cleaning with fine sandpaper.
I call upon my trusty rotary tool again,
this time with a small drill bit installed.
My rotary unit is mounted into a mini press available from dremel. I always seem to break drill bits when
drilling holes by hand. Since I make
many PCB's, the press was worth the small expense.
Make sure the layout is dust free. A small paintbrush is perfect for this
task. Use caution not to disturb the
pattern. Do not wipe the dust away with
cloth or cotton ball, you will wipe away your pattern !
The board is ready for the acid
bath. The copper etchant solution is
available at Radio Shack. A word of
caution about this chemical... This etchant solution is harmful. READ THE WARNING LABEL! Don't get in eyes, on skin or clothes. Do not breath the fumes. Don't pour it down metal sinks or pipes.
I re-use old etchant by straining it
though a coffee filter before each use.
You can see traces of copper in the old solution I saved from previous
etchings. I add a little new solution
each time I etch to replace that which is discarded.
I get the best results by running a small
paintbrush around my pattern on the board and constantly tilting the glass bowl
back and forth. Keeping the liquid
moving speeds up the etching process and maintains uniform etching. Remember to use adequate ventilation.
When all the copper that is not covered
by the transferred image is etched away, remove the board from the solution and
immerse in water to halt the etching process.
Again use a fine grit sandpaper to remove
the mask and... PRESTO! You now have a
pretty good quality Printed Circuit Board.
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