Homebrew_PCBs

> It's a good idea to use the pre-coated PCB material fairly soon after
> buying it, as the shelf-life is limited. I find I get rather poor results
> when using stock much older than about six months. I tend to accumulate a
> lot of odd-sized pieces of unknown vintage, so I need some sort of FIFO
> technique.
>
> Leon

On Tue, 1 Jul 2003 14:00:07 -0500, Neil <cobra_neil@...> wrote:

> Speaking of which, anyone here know what process/materials I need to
> sensitize bare copper-clad boards, for positive-exposure?
>
> Cheers,
> -Neil.
>
>
> On Tuesday 01 July 2003 13:41, Leon Heller scribbled:
>> It's a good idea to use the pre-coated PCB material fairly soon after
>> buying it, as the shelf-life is limited. I find I get rather poor
>> results
>> when using stock much older than about six months. I tend to accumulate
>> a
>> lot of odd-sized pieces of unknown vintage, so I need some sort of FIFO
>> technique.
>>
>> Leon
>
>
>
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>

> please use the search function - we discussed this not too long ago.

> 2 methods:
> dry film (i don't know about)
> liquid resist
>
> basically you need the "laquer".
> this is sold in pressurized spray cans (good for occassional use, ready..)
> and simply as laquer in other containers.
> apply by spraying on OR "spinning" (mount pcb on spinning plate and the
> centrifugal force spreads a center-applied amount evenly over the pcb (use
> shieldig on the outside of course to catch excess))
>
> be aware of dangerous dust (causes shorts etc.)
> maybe dry in a box (dustfree and dark).
>
> but use search please this is better described somewhere.
>
>
> regards
> stefan

> It's a good idea to use the pre-coated PCB material fairly soon after buying
> it, as the shelf-life is limited. I find I get rather poor results when
> using stock much older than about six months. I tend to accumulate a lot of
> odd-sized pieces of unknown vintage, so I need some sort of FIFO technique.
>
> Leon
> --
> Leon Heller, G1HSM
> leon_heller@...
> http://www.geocities.com/leon_heller
>
>
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
>
> To unsubscribe from this group, send an email to:
> Homebrew_PCBs-unsubscribe@yahoogroups.com
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>

> It's a good idea to use the pre-coated PCB material fairly soon after

> it, as the shelf-life is limited. I find I get rather poor results when
> using stock much older than about six months. I tend to accumulate a lot

> odd-sized pieces of unknown vintage, so I need some sort of FIFO

----- Original Message -----
From: "adam Seychell" <adam_seychell@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, July 01, 2003 11:40 PM
Subject: Re: [Homebrew_PCBs] Pre-coated PCB stock shelf-life


> I can only have experience with negative dry film resists.
> Generally the longer its been on there the more difficult it
> is to remove an invisible residue (scum) left behind on the
> copper surface after developing. They call this "resist lock
> on". I did not notice any change with the stripping and
> exposure between 1 week old boards and 2 years old. The
> residue can be removed with vigorous developing (>35°C &
> lots of brushing), but you run into the chance of damaging
> the exposed resist pattern.
>

Thanks, Adam.

That's something like the problem I got with the old stuff (positive). It
took a lot longer than usual to etch fully, by which time there was a lot of
overetching in other places. I've used brushing as well, on occasions. Just
after I had this problem, I made another PCB with fresh stock and got a
perfect board.

Leon
--
Leon Heller, G1HSM
leon_heller@...
http://www.geocities.com/leon_heller

----- Original Message -----
From: "Mike Putnam" <circuit@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, July 02, 2003 1:17 AM
Subject: Re: [Homebrew_PCBs] Pre-coated PCB stock shelf-life


>
>
> > It's a good idea to use the pre-coated PCB material fairly soon after
> buying
> > it, as the shelf-life is limited. I find I get rather poor results when
> > using stock much older than about six months. I tend to accumulate a lot
> of
> > odd-sized pieces of unknown vintage, so I need some sort of FIFO
> technique.
>
> Leon,
> Evidently it depends upon the chemical used to coat the boards. There are
> different chemicals and I cannot tell you what they are. However, I have
> always had a good quantity of stock on hand and when I stopped running the
> business, this caused me to have a lot of board stock that has been
sitting
> in my bin. I am now using stock that I purchased more than two years ago
and
> I am not seeing any differences in the way it etches or develops. All I
can
> tell you about the material is that it is the green coating and that I had
> the stock with the red tinted coating in the past and it did not last very
> long like what you have described.
> -Mike

Is your material negative-working? It looks as though that lasts longer than
the positive stuff I use.

Leon
--
Leon Heller, G1HSM
leon_heller@...
http://www.geocities.com/leon_heller

> > I am not seeing any differences in the way it etches or develops. All I
> can
> > tell you about the material is that it is the green coating and that I

> > the stock with the red tinted coating in the past and it did not last

> > long like what you have described.
> > -Mike
>
> Is your material negative-working? It looks as though that lasts longer

> the positive stuff I use.
>
> Leon