Printed Wiring Boards.
Updated Feb 1, 2019 The paper I was using in no
longer available, the new paper listed works better.
Now that computers and laser printers are a common part of the
household or office, it is possible to make high quality printed
wiring boards with very little additional material. The only
additional material that might be needed is to purchase is some
Staples Glossy Color Laser Paper. (Staples SKU 633215).
Laser toner is a mixture of carbon black and the equivalent of
powdered hot melt glue. This will transfer when heated again.
Water/oil based inks will not transfer!
To make a PWB, the first step is to create or reproduce artwork
in your favorite graphics program. (I use Visio for the PC.).
After you finish your artwork, use the "group"and "duplicate"
functions of the graphics program to make several copies of the
artwork on a single page. This method can be used to produce a
single card to a modest production run.
VERY IMPORTANT Prior to printing, make
a MIRROR IMAGE of your artwork. Use your
graphics program to "group" then flip the image horizontal. Now
print your image.(Note, Visio flips the image fine but not any
text. I have to use drawn text.) The copper clad stock I buy now
is sized 4"x6" on Amazon or ebay. I duplicate the
image in my graphics program to put as many copies as I can in a
4"'x6" area then group and dupe that image as many times as I can
to fill up a 8.5"x11" page. If I am going to print, might as well
use the whole page. Cut out the image you are going to transfer.
If you have the option of print density adjust this to the
highest allowed. Normal printing is about 600 DPI and my printer
(It's a HP 3005) has the option of 1200 DPI.
An important note: I have been at this for 30 plus years. Over
time, a tool here and there have been added to the garage
workshop. All I can do at this point is tell you what I use and
what has worked for me. My very first circuit board (a Tube
amplifier) was made on copper stock, holes drilled first and then
used finger nail polish as an etch resist to connect the holes. It
was crude but it worked. It dose not have to be MIL SPEC or CAD
perfect to give you a working printed circuit board.
Prepare the Copper stock.
- Clean copper with a scotch-brite or fine steel wool. Use a
cross hatch pattern. The little micro scratches gives the toner
something to grab on to when you do the transfer. A fingerprint
will mess up the transfer.
- Clean again with acetone until a paper towel or tissue comes
away clean.
- De-bur the edge of the card stock with a utility knife.
Transferring the image
- Place artwork face down (printed side) to the bare copper.
(This is the reason for the mirror image.)
- Using a standard laundry iron, iron the image to the paper.
Set the laundry iron to about 300-350 degrees. When hot use lots
of pressure and iron the image to the copper for about 5
minutes. (Note: In the interests of domestic harmony, find an
old laundry iron at a yard sale, don't use the household laundry
iron.) Do this on a surface that will take the heat. I use a
marble slab cutting board or the glass range top in the kitchen.
- Let cool to touch, now move the card stock to a large bowl in
a sink, fill with water. Let it soak about 10-20 minutes.
- Peel the paper off the card stock,
- Dry and touch up the artwork. Use a Sanford sharpie to
touch-up up any breaks or holes in the artwork.
- Make sure the emulsion is removed between traces. You may have
to brush off some of the used paper with a toothbrush.
- Let it dry, the black lines turn an off white when dry.
- Note: I now use a T-Shirt heat press from Pro World. So far
300 degrees Fahrenheit for 150 seconds works best.
Etching
- Prior to etching, safety precautions please, what is use is
caustic and has fumes. Do this outside near a garden hose. The
etchant will eat most anything metal, so don't use your inside
stainless steel sink. Plastic vessels only, disposable
plastic gloves, and eye protection. I usually use a 5 gallon
bucket upside down as a work platform then a kitchen plastic
wash basin on top of that.
- A home made etch can be made using 2 parts 3% Hydrogen
Peroxide ( any drug store about $1.00 to $1.50 a quart) to 1
part Muriatic Acid (any hardware store or pool supply about
$5.00 a gallon. (Don't buy the "Green" Muratic acid.). I usually
use the whole quart (4 cups or 32 ounces) of Hydrogen peroxide,
and a half quart (2 cups or 16 ounces) of Muriatic Acid. Pour
the Hydrogen Peroxide into the basin
then slowly add the Muriatic Acid. Buy or make your own
measuring cups (Dollar Store item) for this and do not
mix them with the household cooking measuring cups.
- Place card stock into etching bath. Etch turns green as the
copper is dissolved.
- Agitate solution constantly. I use rubber gloves and keep
brushing the card stock with fingers.This enchant works quickly.
- When etching completed, stop the etching process by washing in
water bath. I do the etching process outside near the garden
hose for this reason.
- When the etching is finished, pour the used etch into the 5
gallon bucket, dilute the enchant some with water then
neutralize the etchant with a LARGE package of baking soda. Add
a little at a time. Its going to foam up so be prepared to wash
down the green foam with the garden hose. Add baking soda until
there is limited or no reaction. When neutralized, pour out in
yard somewhere or down a sewer drain. Rinse and clean your
equipment with running water.
Finishing
- Cut to final size. I found the Mighty Mite, 4" hobby table saw
at Harbor Freight works well for cutting out small PWB's rather
than my standard table saw. I did replace the 4" fine kerf blade
with the 4"diamond blade also from Harbor Freight. You can jam
the small motor, so go slow and careful. It was meant for small
hobby work, so don't expect any more than that. I did find
the fine dust a bother, so now I wear eye protection, a
breathing mask and a shop apron when I cut out boards. I usually
do this at a table outside on the patio so I can hose off the
table and patio of dust.
- Drill card per your drill schedule. Here I use a Dremel tool
in the drill press accessory. I start with a #65 drill. Then use
that as a starter hole if I need to go larger.
- Remove the black etch resist with acetone.
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