Home made PCB's.

[Richard]

Hi,
I produced a little guide on making PCB's at home, if anyone finds it
any use here it is.


http://www.synios.com/files/hpcbp.pdf

Richard

 

[Jon Slaughter]

Hi,
I produced a little guide on making PCB's at home, if anyone finds it
any use here it is.


http://www.synios.com/files/hpcbp.pdf

It would be better if you got your transparency professionally done. It
comes out almost completely opaque and generally higher resolution with no
smudging unless the handler is a moron(happened to me once).

Some things to add to your process:

1. Create a copper pour. This makes copper etching faster and wastes less
etchant as you only are removing the copper required to create traces.

2. For very fine pitch traces/pads you want to make sure your transparency
is printed so that the printed side is against the copper. This reduces the
gap which actually can cause finging effects.

3. Generally put the photo mask on for longer periods of time. The boards I
have say for about 8m but I've done tests between 8m and 30m and the all
produce about the same results but closer to 8 and you risk not removing all
the mask which creates problems and generally requires more resist removal
time or stronger solution.

4. Use warm water for photomask removal solution. It can speed up the time
greatly(from mins to seconds) and seems to produce a more crisp image. (I
generally keep a bottle of concentrated solution that I mix when needed)

5. Copper eching technique and time is very important for getting very fine
pitch. Agitation is necessary because it helps create a more uniform etch.
Heat can make a big difference. If I'm not doing super fine pitch stuff I
generally just leave the board in for 30 mins or so then go agitate by hand
a little. Agitation and heat require more supervision.

Probably the biggest thing though is the mask and proper photoresist
removal. This is why I just run down and get a mask made for about $1.

 

[stan]

It would be better if you got your transparency professionally done. It
comes out almost completely opaque and generally higher resolution with no
smudging unless the handler is a moron(happened to me once).

Are you talking aboutsomethng like Kinko's here or do you use someone
who handles electronics stuff?

I've always just DIY. Do you provide somethng like a PS/PDF or some other
electronic format or do you provide paper?

Lately I've been wondering about finding some low volume vendor to
just do the whole thing but I haven't really spent much time looking.

 

[Jon Slaughter]

Are you talking aboutsomethng like Kinko's here or do you use someone
who handles electronics stuff?

I've always just DIY. Do you provide somethng like a PS/PDF or some
other electronic format or do you provide paper?

Lately I've been wondering about finding some low volume vendor to
just do the whole thing but I haven't really spent much time looking.

I go to office depot. It's about 70c and I simply take a usb drive. They do
the rest. You need to tell them to print at the highest quality and dark as
possible. The format is pdf.

I'm not sure how much better it is than DIY I simply find it easier than
worrying about the ink jet method. I've had success with it but the quality
is less.

You might need to tell them not to get fingerprints on the transparency and
only to handle it by the edges as it will ruin it. I believe if you are not
satisfied they will redo it for you for free. Once I did get fingerprints on
one but it wasn't too bad and was able to fix it with a permanent marker.

Here I'm only talking about the transparencies and not sure if you mean the
whole pcb process or not. I do the pcb's myself(of course not the making the
pcb itself) except in some cases when the boards are very large or require
many.

If you have such a place close that can print the transparencies for less
than a dollar it is probably worth it as the ink jet method does require a
lot of ink(if you use copper pours), special transparency pages that are not
cheap, and the quality is nto as good.

Also the inkjet transparencies use an adhesive so the ink and stick to the
page and this does degrade quality.

Now your pcb has to fit within a 8x11 page of course...

 

[Hammy]

It would be better if you got your transparency professionally done. It
comes out almost completely opaque and generally higher resolution with no
smudging unless the handler is a moron(happened to me once).

Some things to add to your process:

1. Create a copper pour. This makes copper etching faster and wastes less
etchant as you only are removing the copper required to create traces.

I could never understand why people etch off all the copper use it for
a trace. Unless you are doing matching (Z) use the copper for a low R
trace or for ground.

I've been using the toner transfer method for dual sided boards. This
is much cheaper and less time consuming then UV exposure.

http://www.dr-lex.be/hardware/tonertransfer.html

When working with fine pitch components you have to watch the pressure
on the iron so you dont smudge your pads.

I do dual sided boards and use surface mount almost exclusively . I
hate to drill and SM has more desirable traits reduced parasitic's and
size to name a few.

[snip]

 

[Richard]

The toner transfer method looks interesting, what's it like for very fine
traces and close pads (SMT)?

 

[Hammy]

The toner transfer method looks interesting, what's it like for very fine
traces and close pads (SMT)?

I just finished an AD9834 dual sided board the AD9834 comes in a 20
lead TSSOP with 0.65 pitch. 0.65 is pretty common for dual bjt's
etc.SC-88 (SOT-363) I use these pretty regularlily traces to 8mil's.

With additional care finer pitches and traces should be possible. You
just have to be careful with the pressure you apply with the iron. If
you use to much you can widen the pads /traces. It just takes a bit of
practice like everything else.

Before I etch I'll go over the board and look for any possible shorts
(Ink smudges) and correct them if required with a tiny sharp
screwdriver. I rarely have to do this anymore.

I also use a minimum etch. This saves on etchant and time. It also
makes the boards more durable for soldering / de soldering.

 

[stan]

I go to office depot. It's about 70c and I simply take a usb drive. They do
the rest. You need to tell them to print at the highest quality and dark as
possible. The format is pdf.

Got it. I used to teach and we outsourced once in awhile but I never
really noticed any special quality advantage; hence I asked the
question. Your idea clearly has merit and I may give it a try.

 

[Clint Sharp]

It would be better if you got your transparency professionally done. It
comes out almost completely opaque and generally higher resolution with
no smudging unless the handler is a moron(happened to me once).

I got some transparency film that was designed for use in laser printers
from Farnell, excellent stuff.

http://uk.farnell.com/mega/100062/laserstar-film-a4-10-sheets/dp/895945

With a genuine HP cartridge I had no problems making PCBs in a small
production run (around 60 boards because we couldn't get them off the
PCB house quickly enough).

Things to remember are that you need to use fresh PCB stock, put the
toner side of the film against the etch resist laminate because you get
a sharper image, turn off RET on the printer (sharper image) and make
sure the driver is set for best quality.

I've prototyped TQFP and SOIC using that film with no major problems,
the problems I did have were caused by old PCB stock and a dodgy
refilled cartridge in the printer. I may have a go at a PCB for some
AD9851 chips I've been hoarding for a couple of years now.