DIY PhotoResist?

[Jon Slaughter]

Anyone here have any experience with adding photoresist yourself? I have a
few copper clad boards with no resist on them and I'd like to maybe add some
myself.

Even going farther I was wondering how difficult it would even be to make
the copper clad board itself? Copper is pretty cheap... just a few pennies
and I'm not sure about the prepreg but I'm sure for prototyping one could
probably using just about anything? (hell maybe even cardboard?) I imagine
it might be difficult to get decent results but maybe its not all that
difficult? (either by copper sheets or melt some copper and roll them
yourself? (I don't actually mean roll them)) I know everyone is going to say
its better to buy, but I at 20 bucks a pop for double sides it seems to
expensive for prototyping or making small quantities of circuits that don't
need the high quality insulative material(Which I imagine can probably still
be done DIT even cheaper than buying(although I'm not taking into account
labor)).

(Main point here is not that I will probably actually end up doing it myself
but just curious if anyone has tried)

Thanks,
Jon

 

[Tim Williams]

I would guess PCB is made by gluing foil with the PCB board stuff when it's
molded. You could try electroforming on top of blank board, but don't
expect nice results, and certainly don't expect a good bond. If you have a
vacuum chamber you could deposit copper vapor before electroplating, but
somehow I doubt that's any cheaper.

I don't know what photoresist consists of, but I'm sure it's a bitch to
cook up at home.

Tim

 

[D from BC]

Anyone here have any experience with adding photoresist yourself? I have a
few copper clad boards with no resist on them and I'd like to maybe add some
myself.

Even going farther I was wondering how difficult it would even be to make
the copper clad board itself? Copper is pretty cheap... just a few pennies
and I'm not sure about the prepreg but I'm sure for prototyping one could
probably using just about anything? (hell maybe even cardboard?) I imagine
it might be difficult to get decent results but maybe its not all that
difficult? (either by copper sheets or melt some copper and roll them
yourself? (I don't actually mean roll them)) I know everyone is going to say
its better to buy, but I at 20 bucks a pop for double sides it seems to
expensive for prototyping or making small quantities of circuits that don't
need the high quality insulative material(Which I imagine can probably still
be done DIT even cheaper than buying(although I'm not taking into account
labor)).

(Main point here is not that I will probably actually end up doing it myself
but just curious if anyone has tried)

Thanks,
Jon

Huhhhh... I've posted this so times....
'Try out dry film photoresist..'..
mmmm...maybe I should start selling the stuff on here..

You could try out toxic potassium dichromate + a protein. (So I've
heard.)
But I don't think it's popular.


D from BC

 

[Tom Bruhns]

Huhhhh... I've posted this so times....
'Try out dry film photoresist..'..
mmmm...maybe I should start selling the stuff on here..

You could try out toxic potassium dichromate + a protein. (So I've
heard.)
But I don't think it's popular.

D from BC

http://www.thinktink.com/ -- but if you offered dry film for sale in
modest quantities, you very well could find some takers. Supposedly
Injectorall will coat boards for you, too.

I used to coat my own boards with Shipley AZ-111, but that was when I
needed enough for other things to buy it by the quart, and a couple
quarts wasn't all that expensive. I believe it's now close to $1000 a
quart and is sold in 6 quart lots, minimum--though I may be mistaken.
But given the time it takes to lay out a board and the cost of the
parts to put on it, even paying one of the fast-turn proto shops to
make a board for you isn't all that bad. And if you do etch your own,
paying something like 30 cents per square inch for top-quality pre-
coated double sided board material seems cheap.

 

[D from BC]

http://www.thinktink.com/ -- but if you offered dry film for sale in
modest quantities, you very well could find some takers. Supposedly
Injectorall will coat boards for you, too.

I used to coat my own boards with Shipley AZ-111, but that was when I
needed enough for other things to buy it by the quart, and a couple
quarts wasn't all that expensive. I believe it's now close to $1000 a
quart and is sold in 6 quart lots, minimum--though I may be mistaken.
But given the time it takes to lay out a board and the cost of the
parts to put on it, even paying one of the fast-turn proto shops to
make a board for you isn't all that bad. And if you do etch your own,
paying something like 30 cents per square inch for top-quality pre-
coated double sided board material seems cheap.

$1000.00/qrt !!!
Damn might be more expensive than ink jet ink.

For small boards, I use precoated Injectorall boards from Digikey.
For larger boards, I wet laminate the dry film onto cheapo surplus
boards.

Using keyword 'photoresist' on ebay returns no relevant results.
Time to set up shop
Or figure out why no one else has...


D from BC

 

[[email protected]]

norland 60 or norlan 61 UV optical cured cement is 16$ a bottle for a
ounce or two. start there.
They probably have something hackable on their web site.

Steve

 

[Spehro Pefhany]

http://www.thinktink.com/ -- but if you offered dry film for sale in
modest quantities, you very well could find some takers. Supposedly
Injectorall will coat boards for you, too.

I used to coat my own boards with Shipley AZ-111, but that was when I
needed enough for other things to buy it by the quart, and a couple
quarts wasn't all that expensive. I believe it's now close to $1000 a
quart and is sold in 6 quart lots, minimum--though I may be mistaken.
But given the time it takes to lay out a board and the cost of the
parts to put on it, even paying one of the fast-turn proto shops to
make a board for you isn't all that bad. And if you do etch your own,
paying something like 30 cents per square inch for top-quality pre-
coated double sided board material seems cheap.

These guys have KPR-3 for only $478 US a quart.

http://www.dalpro.net/Page.html


Best regards,
Spehro Pefhany

 

[John Larkin]

Anyone here have any experience with adding photoresist yourself? I have a
few copper clad boards with no resist on them and I'd like to maybe add some
myself.

Even going farther I was wondering how difficult it would even be to make
the copper clad board itself? Copper is pretty cheap... just a few pennies
and I'm not sure about the prepreg but I'm sure for prototyping one could
probably using just about anything? (hell maybe even cardboard?) I imagine
it might be difficult to get decent results but maybe its not all that
difficult? (either by copper sheets or melt some copper and roll them
yourself? (I don't actually mean roll them)) I know everyone is going to say
its better to buy, but I at 20 bucks a pop for double sides it seems to
expensive for prototyping or making small quantities of circuits that don't
need the high quality insulative material(Which I imagine can probably still
be done DIT even cheaper than buying(although I'm not taking into account
labor)).

(Main point here is not that I will probably actually end up doing it myself
but just curious if anyone has tried)

Thanks,
Jon

The classic glop was KPR, Kodak PhotoResist. I still have some around.
You'd spin or spray it on some copperclad, bake dry, and expose
through a negative. There was a developer which was mostly xylene. It
polymerized where UV hit it, making those regions insoluble to the
developer.

I think KPR and/or its developer were mildly toxic, so I don't know if
they're still on the market. I've seen references to KPR3, maybe the
newer generation. Google <kpr photoresist>

It was easy to do clean 8 mil lines/spades with KPR and decent
emulsion-down film.

John

 

[Tom Bruhns]

These guys have KPR-3 for only $478 US a quart.

http://www.dalpro.net/Page.html

Best regards,
Spehro Pefhany

KPR?? Yeccchhhhh!

Sorry, but I'd a lot rather pay the price for some good resist. That
could be a personal bias, but I gave up on KPR within, um,
microseconds of trying the Azoplate resist. It ended up being a good
choice also from the standpoint of what I was doing; the processing
took fewer steps with the AZ111 than it would have with KPR. But the
world of photoresists has moved on, rather a long ways I suppose,
since the days of KPR and AZ111. These days, perhaps Rohm and Haas
Photoposit SN66??

Cheers,
Tom

 

[Robert Baer]

I would guess PCB is made by gluing foil with the PCB board stuff when it's
molded. You could try electroforming on top of blank board, but don't
expect nice results, and certainly don't expect a good bond. If you have a
vacuum chamber you could deposit copper vapor before electroplating, but
somehow I doubt that's any cheaper.

I don't know what photoresist consists of, but I'm sure it's a bitch to
cook up at home.

Tim

Photoresist is cheap as hell to make: egg white for the base and
potassium dichromate for photosensitivity.
After exposure, use the universal solvent (water) as the developer.

 

[Robert Baer]

Huhhhh... I've posted this so times....
'Try out dry film photoresist..'..
mmmm...maybe I should start selling the stuff on here..

You could try out toxic potassium dichromate + a protein. (So I've
heard.)
But I don't think it's popular.


D from BC

Correct, not "popular" but useable.

 

[Spehro Pefhany]

KPR?? Yeccchhhhh!

Sorry, but I'd a lot rather pay the price for some good resist. That
could be a personal bias, but I gave up on KPR within, um,
microseconds of trying the Azoplate resist. It ended up being a good
choice also from the standpoint of what I was doing; the processing
took fewer steps with the AZ111 than it would have with KPR. But the
world of photoresists has moved on, rather a long ways I suppose,
since the days of KPR and AZ111. These days, perhaps Rohm and Haas
Photoposit SN66??

Cheers,
Tom

So what's the difference between the various KPRs?


Best regards,
Spehro Pefhany

 

[Sarason]

Anyone here have any experience with adding photoresist yourself? I have a
few copper clad boards with no resist on them and I'd like to maybe add some
myself.

Even going farther I was wondering how difficult it would even be to make
the copper clad board itself? Copper is pretty cheap... just a few pennies
and I'm not sure about the prepreg but I'm sure for prototyping one could
probably using just about anything? (hell maybe even cardboard?) I imagine
it might be difficult to get decent results but maybe its not all that
difficult? (either by copper sheets or melt some copper and roll them
yourself? (I don't actually mean roll them)) I know everyone is going to say
its better to buy, but I at 20 bucks a pop for double sides it seems to
expensive for prototyping or making small quantities of circuits that don't
need the high quality insulative material(Which I imagine can probably still
be done DIT even cheaper than buying(although I'm not taking into account
labor)).

(Main point here is not that I will probably actually end up doing it myself
but just curious if anyone has tried)

Thanks,
Jon

I studied the chemistry of photoresists with a view to making a homebrew
or a cheap'n safe version for the homebrew market. The evolution of
photoresists is way to complex to cover in a single post. But their is a
book called oddly enough "Photoresists" by Williams which IIRC was
published about 1970. Photoresists have moved on a lot from there, as
the IC industry has required better and better lithography for IC
manufacture. Now the gotcha's wet resist needs to be of a consistent
thickness to get consistent exposure times. This is a real PITA for home
use. One solution to this is a record player used as the spin on table.
The best solution are dry negative resists which are used by the PCB
manufacturers. Applying them with a machine made for the process, or
wetting the circuit board and then floating a precut out sheet of resist
you can do at home. Then the film is rolled onto the board, so that no
bubbles get to form. Exposure with an inkjet negative and etching will
get you a very nicely made board. If you want very high resolution lines
a homebuilt spray etcher is the way to go. There is a Yahoo group
devoted to Homebrew.

http://groups.yahoo.com/group/Homebrew_PCBs

There are allsorts of tips and techniques in that group

Best of luck

Andrew

 

[Barry Lennox]

Anyone here have any experience with adding photoresist yourself? I have a
few copper clad boards with no resist on them and I'd like to maybe add some
myself.

Yes, KPR, I used it for many years with good results (Xylene was the
'cheap' developer instead of the real ($$$) stuff. It was very
important to get a thin coat, I used to swab it on, as thin as
possible, then spin it on a much-modified turntable

Actually, I still have much of the quart bottle I paid (IIRC) $16 for
in about 1973. I last used some a year ago, and it still works
perfectly!

Even going farther I was wondering how difficult it would even be to make
the copper clad board itself? Copper is pretty cheap...

I'll bet it's not as cheap as surplus PCB stock, I have acquired good
stocks that way. Also check out a local PCB house, if nearby, they
will generally give you offcuts free, I still operate from a donated
boxful from about 10 years ago.