Homebrew PCBs

Anyone see these extra bits of photomask after developing?

http://www.delorie.com/pcb/inkjet/mask-bits.jpg

This is at 200x, the gap is only 6 mil.  I've tried extra developing,
rinsing under high-pressure water, and scrubbing with a sponge.  I can
get them out one at a time with a pin, but that's not an acceptable
solution.  I'm even exposing a step less than usual in case it's from
a pinhole.

(if the above url complains, use http://www.delorie.com/pcb/inkjet/mask-bits.html)


Also, I discovered that my laminator is too hot for this film.  If I
run a heat-gun-heated board through the laminator, it comes out all
bubbly and wrinkled.

----- Original Message ----- 

From: "DJ Delorie" <dj@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, July 04, 2008 8:14 PM
Subject: [Homebrew_PCBs] today's problem...


> 
> Anyone see these extra bits of photomask after developing?
> 
> http://www.delorie.com/pcb/inkjet/mask-bits.jpg
> 
> This is at 200x, the gap is only 6 mil.  I've tried extra developing,
> rinsing under high-pressure water, and scrubbing with a sponge.  I can
> get them out one at a time with a pin, but that's not an acceptable
> solution.  I'm even exposing a step less than usual in case it's from
> a pinhole.

Dust? Or defects in the resist film.

Leon
--
Leon Heller
Amateur radio call-sign G1HSM
Yaesu FT-817ND and FT-857D transceivers
Suzuki SV1000S motorcycle
leon355@...
http://www.geocities.com/leon_heller

"Leon" <leon355@...> writes:
> Dust? Or defects in the resist film.

It's got the color of resist film.  I'm pretty careful about rinsing
the film and board just before they come together.

----- Original Message ----- 

From: "DJ Delorie" <dj@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, July 04, 2008 9:25 PM
Subject: Re: [Homebrew_PCBs] today's problem...


> 
> "Leon" <leon355@...> writes:
>> Dust? Or defects in the resist film.
> 
> It's got the color of resist film.  I'm pretty careful about rinsing
> the film and board just before they come together.

I meant dust on the artwork or the resist, before exposure.

Leon

"Leon" <leon355@...> writes:
> I meant dust on the artwork or the resist, before exposure.

Ah!  Yes, it could be that.  I'll add "spray print with compressed
air" to my list of things to do.  No, I'm not going to try rinsing it ;-)

I suppose I should wash the plate glass I'm using to hold it down,
too.

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
> 
> Anyone see these extra bits of photomask after developing?
> 
> http://www.delorie.com/pcb/inkjet/mask-bits.jpg
Yup, I have seen a bit of this.  I am no longer doing boards myself,
the commercial shops are SO cheap, although I might do one every few
years.  But, I am using my system for making solder stencils out of
.003" brass shim stock, just like a double-sided PCB.  And, the
geometries are getting VERY small.  The edges of your resist look VERY
jagged.  What is your master artwork?  If the edge of the master
artwork is not very sharp and crisp, it can cause the edges of the
pattern to be jagged or thin, which I believe I can see in your
micrograph.

I have a laser photoplotter that runs at 1000 DPI in both directions,
and it prints a sharp-edged image on litho film.  I definitely get a
sharper resist pattern developed on the PCB/brass, without that
scalloped edge look.

One thing I have been doing is to scrub the board/brass with either
steel wool or fine (600 to 1500 grit) sandpaper, wash well and drip
dry, before laminating.  This greatly helps the resist adhere to the
laminate.

Jon

"Jon Elson" <elson@...> writes:
> The edges of your resist look VERY jagged.  What is your master
> artwork?

2880 DPI inkjet on Silkjet film.  I've posted here before about the
printer's paper feed not being as accurate as needed, giving
comb-shaped edges.

> If the edge of the master artwork is not very sharp and crisp, it
> can cause the edges of the pattern to be jagged or thin, which I
> believe I can see in your micrograph.

Hmmm... so you're thinking it's a bit of half-exposed mask that fell
off and stuck elsewhere or something like that?

> One thing I have been doing is to scrub the board/brass with either
> steel wool or fine (600 to 1500 grit) sandpaper, wash well and drip
> dry, before laminating.  This greatly helps the resist adhere to the
> laminate.

I've tried both scrubbie and 2000 grit sandpaper with comparable
results.

I found that after the cleaning and steel wool, I would give a final 
wipe down with acetone or
denatured alcohol, let if evaporate fully,   and it made all the 
difference with ink adhesion in my case.