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Dry Film Storage/Posting - Don't Do What I Did!

Dry Film Storage/Posting - Don't Do What I Did!

2013-05-26 by James

A cautionary tale.

So I have been selling sheets (12x17cm) cut off my roll of dry film
[which I bought from China], not making money really, more as a service
to my fellow New Zealanders who might want to give it a go.

Anyway, I had been trying to think of a way to post it for as cheap, and
little packaging effort as possible.

I started out sending it flat in a sealed cardboard envelope, one stamp,
this worked fine, but actually getting it flat and into the envelope was
always an exercise in frustration, and took me about 10 times longer
than it should have.

So then I started to send it in it's natural "curl/roll", but I had to
use (make) a package out of sturdy cardboard to ensure it wouldn't get
crushed (and therefore creased), this wasn't really a problem, but it
did push the post up from just 70c for the flat envelope, to now $2.70.

So, long story shorter, I was in one of the local "cheap stuff from
china" type shops and I happened across some long lollipop sticks, and
some tissue wrapping paper. Aha! I thought, perfect! I cut a piece of
tissue paper larger than the film, then roll the film and paper around
the lollipop stick, like a sponge roll, a bit of tape around the outside
with a tab to pull it open and they could be sent for just 2 stamps. I
made up a test roll as to how I would send it, and then unrolled it to
test that it would be easy to "unpack", and I looked at the film, and it
looked just fine.

So I made up some of these rolls, and put them in my box which I keep in
the dark recesses of my office cupboard with the film roll.

Come a week later, and somebody wants to buy some. So I grab out the
rolls. I had to make up one more, which I did, then packaged
everything. But before I sent it, something in the back of my mind said
"James, you know, maybe you should do a quality check on one of those
rolls you made up last week.. just in case".

So I de-packaged the order and took a look at a random roll. And it's
just as well I did. The photo sensitive layer seemed to have, for want
of a better word, wrinkled, or crinkled, or rippled, even though the
protective layers were fine. I tested some to be sure, but it's not
usable (adheres to the board normally, but the developed image is like
crinkle-cut chips).

My roll of dry film, and a few loose cut sections I have, which were all
stored in the same place, were fine. The one I had made up earlier
today, it was fine, so I think it must be something to do with being
rolled up tightly (5mm core diameter) for a period of time. It's fairly
warm in my office, so perhaps that has something to do with it, but all
the other film is fine, just these rolled up ones bit the dust.

Luckily I had only made up 10 rolls like this, I've now undone them all
and put them flat between some card and a heavy thing in a warm place to
see if there's any hope of resurrection for my personal usage, but I
doubt it somehow.

Re: [Homebrew_PCBs] Dry Film Storage/Posting - Don't Do What I Did!

2013-05-26 by Roland Harriston

Two wild guesses:

1. If the "sticks" are made of some sort of processed pulp/paper material,
then something used in the process might outgas and affect the film when
in close proximity.

2. Same for wooden sticks, which would be processed (at least cleaned)
in something that reacts with the film.

Not all polymers are alike, and some of them don't like each other at all.

Roland F. Harriston, P.D.
****************************



On 5/26/2013 9:54 AM, James wrote:
>
> A cautionary tale.
>
> So I have been selling sheets (12x17cm) cut off my roll of dry film
> [which I bought from China], not making money really, more as a service
> to my fellow New Zealanders who might want to give it a go.
>
> Anyway, I had been trying to think of a way to post it for as cheap, and
> little packaging effort as possible.
>
> I started out sending it flat in a sealed cardboard envelope, one stamp,
> this worked fine, but actually getting it flat and into the envelope was
> always an exercise in frustration, and took me about 10 times longer
> than it should have.
>
> So then I started to send it in it's natural "curl/roll", but I had to
> use (make) a package out of sturdy cardboard to ensure it wouldn't get
> crushed (and therefore creased), this wasn't really a problem, but it
> did push the post up from just 70c for the flat envelope, to now $2.70.
>
> So, long story shorter, I was in one of the local "cheap stuff from
> china" type shops and I happened across some long lollipop sticks, and
> some tissue wrapping paper. Aha! I thought, perfect! I cut a piece of
> tissue paper larger than the film, then roll the film and paper around
> the lollipop stick, like a sponge roll, a bit of tape around the outside
> with a tab to pull it open and they could be sent for just 2 stamps. I
> made up a test roll as to how I would send it, and then unrolled it to
> test that it would be easy to "unpack", and I looked at the film, and it
> looked just fine.
>
> So I made up some of these rolls, and put them in my box which I keep in
> the dark recesses of my office cupboard with the film roll.
>
> Come a week later, and somebody wants to buy some. So I grab out the
> rolls. I had to make up one more, which I did, then packaged
> everything. But before I sent it, something in the back of my mind said
> "James, you know, maybe you should do a quality check on one of those
> rolls you made up last week.. just in case".
>
> So I de-packaged the order and took a look at a random roll. And it's
> just as well I did. The photo sensitive layer seemed to have, for want
> of a better word, wrinkled, or crinkled, or rippled, even though the
> protective layers were fine. I tested some to be sure, but it's not
> usable (adheres to the board normally, but the developed image is like
> crinkle-cut chips).
>
> My roll of dry film, and a few loose cut sections I have, which were all
> stored in the same place, were fine. The one I had made up earlier
> today, it was fine, so I think it must be something to do with being
> rolled up tightly (5mm core diameter) for a period of time. It's fairly
> warm in my office, so perhaps that has something to do with it, but all
> the other film is fine, just these rolled up ones bit the dust.
>
> Luckily I had only made up 10 rolls like this, I've now undone them all
> and put them flat between some card and a heavy thing in a warm place to
> see if there's any hope of resurrection for my personal usage, but I
> doubt it somehow.
>
>



[Non-text portions of this message have been removed]

Re: [Homebrew_PCBs] Dry Film Storage/Posting - Don't Do What I Did!

2013-05-26 by KeepIt SimpleStupid

<snip>

Why not just use a cardboard mailing tube.  If you need tape, try Post-it tape or Kapton tape.  Kapton is expensive, about $18/roll, but is easily removed even after seeing high temperatures of 200 deg Centegrade.  Kapton tape uses a silicon based adhesive.

You could also try for a flat send is to use either Kapton tape on the corners or a triange of paper and Kapton tape to hold the sheet flat on a backer board.  Then sandwich with another cardboard.

If you live in the states, I could mail the OP a sample piece of the tape.  Contact me via email.


[Non-text portions of this message have been removed]

Re: [Homebrew_PCBs] Dry Film Storage/Posting - Don't Do What I Did! Neg film Riston photoresist storage and packing

2013-05-26 by Robin Whittle

Hi James,

Assuming your film is the same in principle as the Riston MM540 I get
from the Czech Republic: http://www.ebay.com/sch/gaminn/m.html I think
it is vital not to bend or create uneven pressure on the film.

The photosensitive material is soft enough that it can be bonded to
copper with a temperature of 100C to 120C. This means it will creep
(become thinner) if pressed unevenly.

The MM540 is supplied in a roll, without a core, with a diameter of
about 3cm. This is flattened somewhat in the styrofoam box it arrives
in, and I leave it in that for storage. The box itself is white and
this is enclosed in black plastic. I cut open one end of the black
plastic so I can withdraw the roll and peel some off the outside. I
store this in a cardboard box in a relatively dark place.

I think it is probably important to keep the roll closely wound so no
air can get to the film in general. The oxygen in air definitely stops
the photosensitive process - this is my experience and I think it is
documented somewhere. The protective film which covers the
photosensitive film once it has been bonded to the copper is good enough
to keep oxygen out for long enough to do the exposure, however I am not
sure how good it is for longer term storage.

The softer film which is removed before lamination might be even less
protective against oxygen. So I am not convinced that loose sheets of
this material will store well, since this exposes oxygen to both sides
of the three layer material with the softer layer, I guess, being not
such a good protection.

As long as the material is in a roll, without any air gaps (as is the
case with the Riston from the Czech Republic) this resembles the large
rolls on which it is packed in from the manufacturer. Normally, the
moment (or minutes or maybe an hour or so I guess) the 3 layer film
comes off the roll, the soft protective layer will be removed and the
photosensitive layer will be bonded to the copper with the harder
protective film on top. Once bonded to copper, no oxygen can come from
that side. Pulling the hard protective film off the copper before
exposure will make the film less sensitive or totally insensitive to light.

Perhaps the internal loop of Riston at the centre of this roll I get
would have oxygen permeating through the soft film, so I would expect
that last piece of material to be unusable.

- Robin

Re: [Homebrew_PCBs] Dry Film Storage/Posting - Don't Do What I Did!

2013-05-27 by James Sleeman

KeepIt SimpleStupid wrote:
>
>
> Why not just use a cardboard mailing tube.
>

Cost. Sending $2 of film, in a tube that costs probably a $2 on its
own, and means that postage would be at least $6, doesn't make sense.

>
> If you live in the states, I could mail the OP a sample piece of the
> tape. Contact me via email.
>

I have a very large roll of kapton, here in New Zealand.

Re: [Homebrew_PCBs] Dry Film Storage/Posting - Don't Do What I Did! Neg film Riston photoresist storage and packing

2013-05-27 by James Sleeman

Robin Whittle wrote:
> This means it will creep
> (become thinner) if pressed unevenly.
>
Yes, I though that the 5mm core, and rolling it up gently "looked ok".
But I think it must have been too small a diameter to be stored that
way for a period of time, my feeling is that it needs to be in a fairly
"natural" curl.


> that side. Pulling the hard protective film off the copper before
> exposure will make the film less sensitive or totally insensitive to light.
>
Actually my experience, if you do happen to pull off the top layer
before exposure, it still exposes fine. I imagine there is a time
factor, not an instant thing.

Re: Dry Film Storage/Posting - Don't Do What I Did!

2013-05-30 by James

Just an update on this...

On 27/05/13 04:54, James wrote:
> I've now undone them all and put them flat between some card and a
> heavy thing in a warm place to see if there's any hope of resurrection
> for my personal usage, but I doubt it somehow.

This does actually seem to have helped, there is less wrinklyness in the
resist layer and I just successfully used a sheet with just a couple of
touchups which perhaps partly was because I was too lazy to break out
the laminator and just used a clothes iron to apply it to the 7x10cm
board, and may have had the developer a bit strong too (my measuring
style is "eh, that's probably about right").

But anyway, seems to be salvaged good enough for my personal usage, at
least that sheet was.