Stencil or stamp?

Hi all,

I have much experience in making printed circuit boards
using photoetching techniques. Recently I got 10 Kgs of
epoxy glass copper clad boards, double sided, from a
friend that quitted his electronics activity.

My past experiences with photoetching have been a great
success if I used already-photoresist-coated boards, and
a total failure when I tried to apply photoresist via a
spray on non photoresist-coated boards (like those 10 Kg
of epoxy glass I recently got).

So I wanted to use a different system for these uncoated
epoxy glass copper boards.

So far I'm imagining two possible solutions:

1) make stencils, and then spray a normal acid-resistant
varnish through its "holes".

2) make stamps, and apply them on the epoxy glass to put
a strate of ink where necessary (will it be thick enough?)

I need to produce really fine detail, like 0.2 mm lines
(surface mount devices), and these lines must not have any
breaks in them, because that would mean an electrical
connection break.

What would be the best path to follow, stencils or stamps?
I would prefer stamps, ideally.

And, then, what would be the best way to make such a high
resolution stamps or stencils?

Thanks!
Giovanni

 

[Harvey White]

On 6 Dec 2003 09:17:52 GMT, giovanni@invalid.de wrote:

Hi all,

As a matter of personal opinion, not having tried either, I'd think
that silk screen would produce finer lines.

However, I don't think that it will produce the line size you want.
Sadly, you might find that the photoetch method is your best option.

I also have a lot of pcboard material, and the only coating method
that I have used, which is quite involved, rather expensive, and uses
some nasty chemicals, is the Kodak KPR photoresist method. I still do
not think that it would be your best choice, and you will need
ultraviolet lamps, developer, ink/dye, the resist, and a negative of
your board pattern.

Harvey

I have much experience in making printed circuit boards
using photoetching techniques. Recently I got 10 Kgs of
epoxy glass copper clad boards, double sided, from a
friend that quitted his electronics activity.

My past experiences with photoetching have been a great
success if I used already-photoresist-coated boards, and
a total failure when I tried to apply photoresist via a
spray on non photoresist-coated boards (like those 10 Kg
of epoxy glass I recently got).

So I wanted to use a different system for these uncoated
epoxy glass copper boards.

So far I'm imagining two possible solutions:

1) make stencils, and then spray a normal acid-resistant
varnish through its "holes".

2) make stamps, and apply them on the epoxy glass to put
a strate of ink where necessary (will it be thick enough?)

I need to produce really fine detail, like 0.2 mm lines
(surface mount devices), and these lines must not have any
breaks in them, because that would mean an electrical
connection break.

What would be the best path to follow, stencils or stamps?
I would prefer stamps, ideally.

And, then, what would be the best way to make such a high
resolution stamps or stencils?

Thanks!
Giovanni

 

[Jon Elson]

On 6 Dec 2003 09:17:52 GMT, giovanni@invalid.de wrote:




I need to produce really fine detail, like 0.2 mm lines
(surface mount devices), and these lines must not have any
breaks in them, because that would mean an electrical
connection break.

What would be the best path to follow, stencils or stamps?
I would prefer stamps, ideally.


Forget these. I seriously doubt either will work. What you want is

DuPont Riston dry film resist. It is applied with a hot roll laminator,
and is amazingly robust and pinhole-free. It is exposed with similar
UV light to the KPR resists, and is then developed in Sodium Carbonate.
Stripper is Lye, the only hazardous chemical in the whole system.
The resist does have a shelf life, but it seems like the shelf life
begins when you laminate the boards, not when the roll was made.
..2 mm lines are pretty common now in the industry, and they almost
exclusively use Riston or somebody's clone of it.

Jon