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'[EE] Etching my first PCB - all the details'
2009\07\17@215554 by solarwind

picon face
I etched my first PCB today. It came out very well (considering that
it was the first one I did). I used a mix of different techniques
which all worked out well for me in the end.

To begin, I made a simple design for a quick prototype board for my
dsPIC33FJ128GP802. The board itself is very small, just about 1.5" x
2.5" (off the top of my head). I had a large sheet of copper clad
board so I had to cut out the small piece that I would be working
with. This part was not fun at all.

I printed out my design and traced out the rectangle off a corner of
the large copper clad board. I then used a utility knife to score the
sides of my design. It took a while to get deep enough to snap. Then I
used metal shears to cut one edge of the board. This was an unclean
cut and damaged part of the large board and slightly warped the copper
on my design. No big deal. I then stuck the remaining part of the
board into a vice (with paper towel for padding) and snapped the
remaining edge. I then sanded the sides with a piece of (metal
purpose) sand paper. I was then left with a small rectangle of copper
board ready to be used for toner transfer. I used nail polish remover
to clean the board. Then I used soap and continued to clean the board.
Finally, I took some fine sandpaper and scrubbed the board clean. The
board was now ready for toner transfer.

>From suggestions from my other thread, I tried a different printer. I
used the same paper (staples glossy paper for laser printers) that I
had tried before. I set the print quality to the highest setting and
configured it to deposit the most amount of toner possible. I then cut
out my design and headed over to my clothes iron. I preheated the
board by placing a blank sheet of paper of my board and ironing it for
about a minute. Then I carefully placed my design onto the copper
board. It stuck instantly. I ironed it for about 2 minutes. (60 of
those seconds I just left the iron on top and went downstairs to get a
snack). I didn't do anything special. I just pressed hard (but not too
hard) and went over it with the tip of the iron. I then filled a small
sandwich box with water (about body temperature) and dropped my board
(with the design paper still stuck on it) into the water. I headed
over to my local grocery store to get some groceries for dinner. By
the time I came back, the paper was soft enough to peel and rub off
with my thumb. Some of the toner smudged, but overall, the quality was
pretty good. The toner had definitely stuck well this time.

Now for the etching part. I took a small dish washing sponge and cut
out a square about 3" x 3" x 0.75". I poured about a table spoon of
ferric chloride on the sponge. I put on my vinyl gloves and started
lightly wiping the board with the sponge. The copper started to come
off instantly and turned the bright-yellow sponge nearly black. I kept
wiping for about 2 - 4 minutes and eventually, all of the copper (that
was not protected by the toner, of course) came off. This sponge
method turned out to be very fast, efficient, clean and easy. Also
saved a lot of ferric chloride. I ended up with a very well etched
board. It was easy to see when it was finished and the etching
solution worked very fast and etched very cleanly. Then I washed the
board and inspected it (and admired it). It would have been perfect
had the toner not smudged. The etching process itself was very clean
and precise. The only trouble was the toner. I need to find a better
way to put etchant-resist onto my copper.

I then took the almost-finished board downstairs to drill. This part
was not fun as well. I drilled about two holes then gave up because
all I had was a clunky drill and very brittle drill bits. This
drilling part is impossible without a proper drill press. A CNC
machine would be ideal (even a crude one would do the job
sufficiently). So there ya have it. An almost-finished PCB.

Looks like I'll need to find myself a drill press.

To all the helped and gave advice, thank you very much. This process
turned out to be fun and educational and I leaned a skill that I'm
sure I'll find very useful in the future. The whole process took less
than an hour and gave very good results. The results would have been
perfect if I had a better method to transfer the toner (via laminator
and a good printer, maybe) and a CNC machine or at least a drill
press.

What I was most impressed with was the sponge method of etching. Only
a table spoon of ferric chloride was required and none of that
heating/agitation nonsense was needed. The process was clean and
efficient - no spills, little to clean up afterward. So if there's any
of you still pouring the etching solution into a tub and
heating/agitating, I highly recommend that you give the sponge method
a try. It's awesome!

-- [ solarwind ] -- http://solar-blogg.blogspot.com/

2009\07\18@084604 by Carl Denk

flavicon
face
4 Items:
1: What was the printer and toner that worked and didn't?
2: For a drill press, I have used Dremel with very good results. I also
have a 16.5" Delta drill press with 1/16" - 5/8" chuck, and then a
smaller drill size chuck that can be gripped, but wouldn't even think of
using that, although the small drill bits with 1/8" shanks can be
gripped easily. Get the regular PCB drills with 1/8" shanks and short
drill spiral lengths. The long drill bits with same shank diameter as
drill size get slight bends, wobble, and eventually break.
3: When making the PCB print image, every hole should have a small size
hole etched in the copper. This becomes the equivalent of an accurately
located center punch to get the drill started at the right location. The
drill will wander to that depression if you get close to the location.
4: For double sided boards, I include a donut at 4 corners, both sides.
Pin prick through the paper before ironing on the first side, drill the
4 holes through the board, use pins through the papers and holes to
align, and iron on the 2nd side. Have had good results with careful
work, but there are limits to the accuracy. Dips with 0.1" spacing
should be no problem if there are not traces between the pads. With
traces between, probably will scrap some boards, probably would solder
wire across for the a few to be made. :)


solarwind wrote:
{Quote hidden}

2009\07\18@091036 by Carl Denk

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face
Oh, one more item: Get a variety, and several of each size (they will
break) drill. I have gotten from Hosfelt and Mouser, but they are
readily available, including resharpened. The resharpened may be OK, but
caution, some (maybe a lot) of their fatigue life is gone, and breakage
is not unusual.

Carl Denk wrote:
{Quote hidden}

2009\07\18@100748 by olin piclist

face picon face
solarwind wrote:
> This process
> turned out to be fun and educational and I leaned a skill that I'm
> sure I'll find very useful in the future.

Everyone that eventually plans to design PC boards regularly should do this
a few times.  The real lesson is that it's a very costly and pain in the
butt way to make mediocre PC boards.  For $109 you can get 100 square inches
of double sided boards with plated vias, solder mask, and silkscreen.  You
said it only took a hour, but I doubt that includes even the amortized
per-board cost of scaring up the materials, setting up, cleaning up, and the
cost of not having plated vias, solder mask, or silkscreen.  For a hobbyist,
time is worth a lot less than when you're doing this for real.  For now it's
novel and therefore fun.  That will get old fast.  Soon enough you'll be
making real money, spare time will be scarce, and $109 will look like a
great alternative.

I experimented with various ways of making PC boards when I was in college
and even shortly after.  Since I was also into photography and had my own
darkroom, I used photographic resist and eventually got reasonably good
results.  It was fun to do a few times and to figure out the process, but
once I had it worked out it just seemed too much hassle to do.  Back then
(1980) there were no available small quantity commercial alternatives.
There was also no PC design software accessible to hobbyists.  At work
(Hewlett Packard) I was still drawing schematics on D size vellum by hand
and a draftsman would take a couple of weeks to lay out a board by hand
using calibrated widths of black tape.  I even wrote my own auto router, but
it wasn't sophisticated enough and the computers of the day weren't powerful
enough for it to be useful for anything but small hobby projects.

I don't miss those days.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2009\07\18@211837 by Jinx

face picon face
> Get a variety, and several of each size (they will break) drill

I use a small hand-held high-speed drill, similar to Radiospares 547-616
and 1.0mm high-speed cobalt bits, similar to Radiospares 248-8294

The drill is coming up for 20 years old, the current drill bit 10 years old
and still cuts like new. I've never broken one in a board. The last was
snapped when the drill fell off the bench, but it has enough shank to be
the spare

Tried a drill press once and didn't like it. No tactile feedback. I think I
would break more bits with a press

I've a couple each of hand drill steel bits 1.2mm, 1.5mm, 2mm, and
3mm for fat legs and bolt holes etc


2009\07\18@223357 by solarwind

picon face
On Sat, Jul 18, 2009 at 9:18 PM, Jinx<spam_OUTjoecolquittTakeThisOuTspamclear.net.nz> wrote:
> Tried a drill press once and didn't like it. No tactile feedback. I think I
> would break more bits with a press
>
> I've a couple each of hand drill steel bits 1.2mm, 1.5mm, 2mm, and
> 3mm for fat legs and bolt holes etc

That's interesting. How do you keep your hand so steady to hit the
middle of the holes? How do you keep the angle at a perfect 90
degrees?

2009\07\18@225636 by John Coppens

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face
On Sun, 19 Jul 2009 13:18:08 +1200
Jinx <.....joecolquittKILLspamspam@spam@clear.net.nz> wrote:

> Tried a drill press once and didn't like it. No tactile feedback. I
> think I would break more bits with a press

That's the (huge) difference between 1mm and 0.7mm. The latter _will_
break if drilling by hand!

John

2009\07\18@233521 by Jinx

face picon face
> > Tried a drill press once and didn't like it. No tactile feedback. I
> > think I would break more bits with a press
>
> That's the (huge) difference between 1mm and 0.7mm. The latter
> _will_ break if drilling by hand!

You could be right. Now I think of it I could grind off a lot of
the shank so that maybe only 5-6mm of the bit protrudes from
the collet, which is all you really need for a single PCB anyway

2009\07\19@012915 by Marechiare

picon face
> That's the (huge) difference between 1mm and 0.7mm.
> The latter _will_ break if drilling by hand!

I didn't use 0.7mm.  With 0.8mm there were no problem.

2009\07\19@082720 by Carl Denk

flavicon
face
How big was the drill press? Probably the issue is, with say a unit that
will drill 1/2" holes, pushing down on the feed lever can create say 100
lbs. of axial force on the drill bit. Even with a light hand, there will
be little tactile feel to a small drill bit. A small drill press with a
fine (small increments) of low force feed should give tactile feed. As
for shortening and resharpening small bits, forget it unless you have a
jig to hold the bit at the correct angles, and do both sides to
symmetric shape/location. I used to touch up sharpen bits by hand, but
the smallest I could do, and be usable was around 3/16". Now I have a
drill doctor drill sharpener. It does great on 1/8" - 3/4". If a bit is
not sharpened properly, it won't center on the center punch accurately,
walking to the side, and bore ragged oversized holes. In the case of PCB
holes, probably would leave ragged copper edges.

I have broken more drill bits by hand than with a drill press. The drill
press provides concentric force on the bit, minimizing the fatigue from
alternating bending stresses. A hand held drill is even with best of
technique going to cause the bending fatigue. With a handheld drill
motor and a bit 1/8" or less, as  you drill, watch the bit for bending.

Jinx wrote:
{Quote hidden}

2009\07\20@005333 by Jinx

face picon face
> How big was the drill press? Probably the issue is, with say a unit
> that will drill 1/2" holes, pushing down on the feed lever can create
> say 100lbs. of axial force on the drill bit

Yes, I know what you mean. I have a 1/2" bench press that I wouldn't
try to use with PCBs. Its chuck just about closes on a 3mm bit. If I
need smaller holes, say in 2mm steel that has to be tapped out to 3mm,
I've a smaller chuck (from an old cordless IIRC) on a 3/8" bolt to go in
the press 1/2" chuck

Bits from 1.2mm up can be used in hand drill, especially if the hole is
already drilled out with a pilot hole. Not a lot of pressure is needed,
actually less than the weight of the drill for the smaller diameters, so
you're holding the weight of the drill up whilst the bit is cutting

The minidrill press I tried was _OK_ but had no particular advantage
over the way I do them free hand. With the drill in my right hand, my
left index finger acts to push the drill straight down. With a good bit
there's very little resistance. One reason why I never use HSS now.
They're alright-ish on phenolic but dull quickly with glass board. I
must have done thousands of holes with this HSCo bit and it's still
sharp. With care, at an angle, I use it for thinning tracks, removing
bridges etc

> As for shortening and resharpening small bits, forget it unless you
> have a jig to hold the bit at the correct angles

I think you misunderstood. If the total length of the bit is 40mm and
20mm protrudes from the collet, then it's the plain shaft end that could
be shortened, not the cutting end. I'd have no expectations sharpening
a thin cobalt bit successfully

> Now I have a drill doctor drill sharpener. It does great on 1/8" - 3/4"

I have a Bosch bit sharpener as a drill attachment. For other tools a
sanding disc on the wood lathe is pretty good. A belt sander or angle
grinder is OK for things like shears, spades and loppers


2009\07\23@133629 by Marechiare

picon face
>> would break more bits with a press
>>
>> I've a couple each of hand drill steel bits 1.2mm, 1.5mm,
>> 2mm, and 3mm for fat legs and bolt holes etc
>
> That's interesting. How do you keep your hand so steady
> to hit the middle of the holes? How do you keep the angle
> at a perfect 90 degrees?

That should not be a problem for the future neurosurgeon :-)

Seriously, key points are:
- precision of rotation;
- speed of rotation;
- stiffness of the system (bits should be short);
- movable should be the lightest part of the system, that is PCB;

Fix the precision high speed motor. Mount the drill bits socket (<1mm)
on the motor's shaft. And use some llinear drive mechanism (from dot
matrix or ink jet printer, or scanner) to help your hands move the
PCB.

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