Homebrew_PCBs

I am trying to produce a small PCB for a SMD pic16f628a-i/so using
chinese blue dry film photoresist. The exposure seems to work fine using
a bank of uv leds and the photoresist turns a nice darkish blue around
30-45 secs of exposure. I am trying to develop using washing soda (I
forget the exact strength but I think it was 200g in litre of water). I
am having difficulty getting this process right. Either some of the
unexposed photoresist does not come off (particularly between close
tracks) or some of the exposed photoresist lifts if I leave it longer.
Anyone having experience with this process willing to comment on what I
may be missing.

On 07/07/2013 12:31, Kerry Koppert wrote:

> I am trying to produce a small PCB for a SMD pic16f628a-i/so using
> chinese blue dry film photoresist. The exposure seems to work fine using
> a bank of uv leds and the photoresist turns a nice darkish blue around
> 30-45 secs of exposure. I am trying to develop using washing soda (I
> forget the exact strength but I think it was 200g in litre of water). I
> am having difficulty getting this process right. Either some of the
> unexposed photoresist does not come off (particularly between close
> tracks) or some of the exposed photoresist lifts if I leave it longer.
> Anyone having experience with this process willing to comment on what I
> may be missing.

I don't think that washing soda (sodium carbonate) will work, you sodium
hydroxide. That's what I use - 2 teaspooons per litre.

Leon
--
Leon Heller
G1HSM

On 07/07/13 23:31, Kerry Koppert wrote:

>
> I am trying to develop using washing soda (I
> forget the exact strength but I think it was 200g in litre of water).
>

Holy moley, WAY too much.

20 grams of washing soda (sodium carbonate) per litre is fine, if you
are using 200g per litre then I'm not surprised it's giving you
trouble! You do not need a strong solution.

If the water is warm, (not hot, just warm), the developing should take 2
- 3 minutes.

Rub it with your fingers as it's going to help remove the gunk.

PS: After etching, make up some strong washing soda with really hot
water and use that to strip, don't bother with sodium hydroxide (lye),
nasty dangerous stuff, and simply not necessary to use at all.





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

Also, here is a document with all my hints and tips for dry film usage:
http://sirius.gogo.co.nz/dry-film-tips.pdf

On 07/07/13 23:31, Kerry Koppert wrote:
>
>
> chinese blue dry film photoresist. The exposure seems to work fine using
>



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

Leon Heller wrote:

> On 07/07/2013 12:31, Kerry Koppert wrote:

> > I am trying to produce a small PCB for a SMD pic16f628a-i/so using
> > Chinese blue dry film photoresist. The exposure seems to work fine

using

> > a bank of UV LEDs and the photoresist turns a nice darkish blue around
> > 30-45 secs of exposure. I am trying to develop using washing soda (I
> > forget the exact strength but I think it was 200g in litre of water). I
> > am having difficulty getting this process right. Either some of the
> > unexposed photoresist does not come off (particularly between close
> > tracks) or some of the exposed photoresist lifts if I leave it longer.
> > Anyone having experience with this process willing to comment on what I
> > may be missing.

> I don't think that washing soda (sodium carbonate) will work,
> you sodium hydroxide. That's what I use - 2 teaspoons per litre.

> Leon
> Leon Heller
> G1HSM

I agree, the bath must be alkaline and a common
and convenient alkaline bath is "Sodium Hydroxide".
I get mine at the local hardware store where
plumbers use it as a drain cleaner.

Note! This stuff has no shelf life. And the plastic container
doesn't deteriorate, unlike the metal Lewis Lye did.

Another use is to clean out cast iron solder pots.
Especially when switching to ROHS lead free solders.

However, it is used in some "Illicit drug manufacturing" and my
hardware guy says it probably will go on the drug "precursor"
list shortly which will make it harder to get.
Stock up now, actually it is pretty cheap anyway.

Just saying!!!

Duane

--
Home of the $35 Solar Tracker Receiver
http://www.redrok.com/led3xassm.htm [*]
Powered by \ \ \ //|
Thermonuclear Solar Energy from the Sun / |
Energy (the SUN) \ \ \ / / |
Red Rock Energy \ \ / / |
Duane C. Johnson Designer \ \ / \ / |
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White Bear Lake, Minnesota === \ / \ |
USA 55110-3364 === \ |
(651)426-4766 use Courier New Font \ |
redrok@... (my email: address) \ |
http://www.redrok.com (Web site) ===

On 08/07/13 01:06, Duane C. Johnson wrote:

>
>
> I agree, the bath must be alkaline and a common
> and convenient alkaline bath is "Sodium Hydroxide".
> I get mine at the local hardware store where
> plumbers use it as a drain cleaner.
>

Drain cleaner, soap manufacturing, methamphetamine production and
melting the flesh of your enemies... all popular uses for sodium
hydroxide (lye).

Sodium carbonate is way way safer, and works just as well (the
"developer" that some ebay sellers include with their dry film, it's
just sodium carbonate). It's found in a large variety of household
products in the laundry aisle of your local supermarket, look for
natural fabric softeners and laundry powders.

Takes a little longer, but you don't have to worry about chemical burns,
or having (more) hazardous chemicals around the place, and much less
chance of leaving it too long and stripping the resist when you were
just trying to develop it.


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

It's an interesting home chemistry demo project to make sodium carbonate from baking soda -- sodium bicarbonate.

Get that box of Arm and Hammer out of the refrigerator and dump into a heavy saucepan. Heat to 400 degrees over a moderate heat, stirring occasionally.

After a while the powder will start boiling. Yes, boiling. It looks cool and will impress your kids.

This is the CO2 dissociating from the bicarbonate. Eventually, all that is left is sodium carbonate, a fire-resistant powder. The CO2? That's how dry powder fire extinguishers do their trick. The bicarbonate absorbs heat and releases CO2.

It's also how soda crackers get fluffy.

Or you can just be boring and buy laundry soda ...


Incidentally, sodium carbonate is sometimes used as a yellow colorant in fireworks.

73
Jim N6OTQ

>________________________________
> From: James <bitsyboffin@...>
>To: Homebrew_PCBs@yahoogroups.com
>Sent: Sunday, July 7, 2013 8:17 AM
>Subject: Re: [Homebrew_PCBs] Developing dry film photoresist
>
>
>On 08/07/13 01:06, Duane C. Johnson wrote:
>>
>>
>> I agree, the bath must be alkaline and a common
>> and convenient alkaline bath is "Sodium Hydroxide".
>> I get mine at the local hardware store where
>> plumbers use it as a drain cleaner.
>>
>
>Drain cleaner, soap manufacturing, methamphetamine production and
>melting the flesh of your enemies... all popular uses for sodium
>hydroxide (lye).
>
>Sodium carbonate is way way safer, and works just as well (the
>"developer" that some ebay sellers include with their dry film, it's
>just sodium carbonate). It's found in a large variety of household
>products in the laundry aisle of your local supermarket, look for
>natural fabric softeners and laundry powders.
>
>Takes a little longer, but you don't have to worry about chemical burns,
>or having (more) hazardous chemicals around the place, and much less
>chance of leaving it too long and stripping the resist when you were
>just trying to develop it.
>
>
>[Non-text portions of this message have been removed]
>
>
>
>------------------------------------
>
>Be sure to visit the group home and check for new Links, Files, and Photos:
>http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>
>
>
>

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

Washing Soda does work, I have been using it since Day 1 with the photo-resist process as it was the cheapest and easiest for me to get. (And with the blue Chinese resist from eBay, too!)

If you have problems with resist staying on between traces, check your mask is dark enough, and you have your printed side right up against the resist etc.

It sounds like your LEDs are quite powerful - mine with LEDs takes about 6 minutes - perhaps this is causing an overexposure problem?


I usually take the board out of the solution and rub it with my finger\soft toothbrush to speed things up too

--- In Homebrew_PCBs@yahoogroups.com, Leon Heller <leon355@...> wrote:
>
> On 07/07/2013 12:31, Kerry Koppert wrote:
> > I am trying to produce a small PCB for a SMD pic16f628a-i/so using
> > chinese blue dry film photoresist. The exposure seems to work fine using
> > a bank of uv leds and the photoresist turns a nice darkish blue around
> > 30-45 secs of exposure. I am trying to develop using washing soda (I
> > forget the exact strength but I think it was 200g in litre of water). I
> > am having difficulty getting this process right. Either some of the
> > unexposed photoresist does not come off (particularly between close
> > tracks) or some of the exposed photoresist lifts if I leave it longer.
> > Anyone having experience with this process willing to comment on what I
> > may be missing.
>
>
> I don't think that washing soda (sodium carbonate) will work, you sodium
> hydroxide. That's what I use - 2 teaspooons per litre.
>
> Leon
> --
> Leon Heller
> G1HSM
>

On 8/07/2013 2:12 p.m., tda7000 wrote:

>
> Washing Soda does work, I have been using it since Day 1 with the
> photo-resist process as it was the cheapest and easiest for me to get.
> (And with the blue Chinese resist from eBay, too!)
>
> If you have problems with resist staying on between traces, check your
> mask is dark enough, and you have your printed side right up against
> the resist etc.
>

Ah right on. Careful examination of the negative show mottling in the
black (I'm using artist's tracing paper in a Kyocera FX720 laser but
I've also tried over-head projector transparency film). The mottling
corresponds to the unexposed(?) resist left behind. I guess my next
question is how do you get really black black on transparent film using
a laser?

>
> It sounds like your LEDs are quite powerful - mine with LEDs takes
> about 6 minutes - perhaps this is causing an overexposure problem?
>
> I usually take the board out of the solution and rub it with my
> finger\soft toothbrush to speed things up too
>
> --- In Homebrew_PCBs@yahoogroups.com
> <mailto:Homebrew_PCBs%40yahoogroups.com>, Leon Heller <leon355@...> wrote:
> >
> > On 07/07/2013 12:31, Kerry Koppert wrote:
> > > I am trying to produce a small PCB for a SMD pic16f628a-i/so using
> > > chinese blue dry film photoresist. The exposure seems to work fine
> using
> > > a bank of uv leds and the photoresist turns a nice darkish blue around
> > > 30-45 secs of exposure. I am trying to develop using washing soda (I
> > > forget the exact strength but I think it was 200g in litre of
> water). I
> > > am having difficulty getting this process right. Either some of the
> > > unexposed photoresist does not come off (particularly between close
> > > tracks) or some of the exposed photoresist lifts if I leave it longer.
> > > Anyone having experience with this process willing to comment on
> what I
> > > may be missing.
> >
> >
> > I don't think that washing soda (sodium carbonate) will work, you
> sodium
> > hydroxide. That's what I use - 2 teaspooons per litre.
> >
> > Leon
> > --
> > Leon Heller
> > G1HSM
> >
>
>

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

On 8/07/2013 1:06 a.m., Duane C. Johnson wrote:

>
> Leon Heller wrote:
>
> > On 07/07/2013 12:31, Kerry Koppert wrote:
>
> > > I am trying to produce a small PCB for a SMD pic16f628a-i/so using
> > > Chinese blue dry film photoresist. The exposure seems to work fine
> using
> > > a bank of UV LEDs and the photoresist turns a nice darkish blue around
> > > 30-45 secs of exposure. I am trying to develop using washing soda (I
> > > forget the exact strength but I think it was 200g in litre of
> water). I
> > > am having difficulty getting this process right. Either some of the
> > > unexposed photoresist does not come off (particularly between close
> > > tracks) or some of the exposed photoresist lifts if I leave it longer.
> > > Anyone having experience with this process willing to comment on
> what I
> > > may be missing.
>
> > I don't think that washing soda (sodium carbonate) will work,
> > you sodium hydroxide. That's what I use - 2 teaspoons per litre.
>
> > Leon
> > Leon Heller
> > G1HSM
>
> I agree, the bath must be alkaline and a common
> and convenient alkaline bath is "Sodium Hydroxide".
> I get mine at the local hardware store where
> plumbers use it as a drain cleaner.
>

The stuff sold as developer by the chinese supplier is anhydrous sodium
carbonate (washing soda). The solution I'm using is 20g/L which is the
strength recommended by the supplier. I really should use a stronger
solution since the washing soda available in the supermarket is not
anhydrous i.e. it has some water in the crystal Na2CO3.5H2O rather than
Na2CO3.

> Note! This stuff has no shelf life. And the plastic container
> doesn't deteriorate, unlike the metal Lewis Lye did.
>
> Another use is to clean out cast iron solder pots.
> Especially when switching to ROHS lead free solders.
>
> However, it is used in some "Illicit drug manufacturing" and my
> hardware guy says it probably will go on the drug "precursor"
> list shortly which will make it harder to get.
> Stock up now, actually it is pretty cheap anyway.
>
> Just saying!!!
>
> Duane
>
> --
> Home of the $35 Solar Tracker Receiver
> http://www.redrok.com/led3xassm.htm [*]
> Powered by \ \ \ //|
> Thermonuclear Solar Energy from the Sun / |
> Energy (the SUN) \ \ \ / / |
> Red Rock Energy \ \ / / |
> Duane C. Johnson Designer \ \ / \ / |
> 1825 Florence St Heliostat,Control,& Mounts |
> White Bear Lake, Minnesota === \ / \ |
> USA 55110-3364 === \ |
> (651)426-4766 use Courier New Font \ |
> redrok@... <mailto:redrok%40redrok.com> (my email: address) \ |
> http://www.redrok.com (Web site) ===
>
>

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

> Kerry Koppert wrote:
>
> <SNIP>
> I guess my next question is how do you
> get really black black on transparent
> film using a laser?

You buy a $30K laser printer.

When I lost access to the excellent
fuji/textronix printer that I used to
make artwork on I used a HP4xxx for a
little while with toner-density-spray.

Eventually I just caved and tried a
cheapy inkjet with gelatine coated
trannys. It produced better results
than the $2000 laser printer did.

So for $100 of inkjet and $1 per sheet
for the trannys you are very "win"

--- In Homebrew_PCBs@yahoogroups.com, Kerry Koppert <kkoppert@...> wrote:

>
> On 8/07/2013 2:12 p.m., tda7000 wrote:
> >
> > Washing Soda does work, I have been using it since Day 1 with the
> > photo-resist process as it was the cheapest and easiest for me to get.
> > (And with the blue Chinese resist from eBay, too!)
> >
> > If you have problems with resist staying on between traces, check your
> > mask is dark enough, and you have your printed side right up against
> > the resist etc.
> >
>
> Ah right on. Careful examination of the negative show mottling in the
> black (I'm using artist's tracing paper in a Kyocera FX720 laser but
> I've also tried over-head projector transparency film). The mottling
> corresponds to the unexposed(?) resist left behind. I guess my next
> question is how do you get really black black on transparent film using
> a laser?

You don't use a laser printer!

I get excellent results with an HP 5940 inkjet and Mega Electronics JetStar film.

Leon

Hi,

What is a "gelatine coated trannys"?

Thanks.

Steve K.

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

On 09/07/2013 22:30, Leon wrote:

>
> You don't use a laser printer!
>
> I get excellent results with an HP 5940 inkjet and Mega Electronics
> JetStar film.

Should be JetStar Premium.

Leon
--
Leon Heller
G1HSM

Kerry Koppert wrote:

>
>
> I guess my next
> question is how do you get really black black on transparent film using
> a laser?
>

You print two copies of the artwork on tracing paper and put them togethor.

On 10/07/2013 8:58 a.m., cunningfellow wrote:

>
> > Kerry Koppert wrote:
> >
> > <SNIP>
> > I guess my next question is how do you
> > get really black black on transparent
> > film using a laser?
>
> You buy a $30K laser printer.
>
> When I lost access to the excellent
> fuji/textronix printer that I used to
> make artwork on I used a HP4xxx for a
> little while with toner-density-spray.
>
> Eventually I just caved and tried a
> cheapy inkjet with gelatine coated
> trannys. It produced better results
> than the $2000 laser printer did.
>
> So for $100 of inkjet and $1 per sheet
> for the trannys you are very "win"
>

Interesting, but I can't find it in New Zealand and importing 50 sheets
would cost $100.

>
>

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

In "Re: [Homebrew_PCBs] Re: Developing dry film photoresist", Kerry
Koppert wrote about trouble with the track resist not being solid enough
after development:

> Ah right on. Careful examination of the negative show mottling in the
> black (I'm using artist's tracing paper in a Kyocera FX720 laser but
> I've also tried over-head projector transparency film). The mottling
> corresponds to the unexposed(?) resist left behind. I guess my next
> question is how do you get really black black on transparent film
> using a laser?

I have had good, high-contrast, results with a laser film from Canada:

http://screenprinting.asc365.com/index.asp?ID=TT1029

I got about 7:1 contrast - so the clear parts let through 7 times as
much as the black parts. This is an average reading in visible light,
but the toner is plain black, so I guess it should be the same for the
350 to 380nm UVA light to which Riston MM540 negative acting photoresist
is sensitive.

http://tech.groups.yahoo.com/group/Homebrew_PCBs/message/31293?var=0&l=1

http://www2.dupont.com/Imaging_Materials/en_US/assets/downloads/datasheets/mm500series.pdf


There is a little unevenness (what an odd looking word!) in the black,
depending on the laser printer and exactly how the toner roller puts
toner on the drum. So the contrast ratio in the lightest parts of the
toner would probably be 5:1 or 4:1 at worst.

I am using Brother laser printers. 600DPI is fine. I have some 1200 x
1200 DPI Brother printers and they are marginally better. With 1200 x
1200 I could get 0.005 inch tracks with 0.005 inch
spacings (127 micron). That was pushing the limits, but the results
were really solid at 0.010 inch (254 micron) which is as small a track
as I would probably want on a PCB.

I wrote more about this in August last year:

http://tech.groups.yahoo.com/group/Homebrew_PCBs/message/30467?var=0&l=1

Thid laser film is also available from Australia:

http://myworld.ebay.com.au/printingsupplies2009/

I haven't tried the blackening agent at the Canadian site. I see no
need for it with my current setup, which involves a reasonably
collimated light source - a 400W 230V halogen lamp. The Riston I am
using has high contrast. Ideally I would use a 10 watt UV LED light,
which would not heat up the PCB and phototool to the degree which the
400W lamp does.

- Robin

I think the reccomendation of checking the mask is a good one.

You might try reducing your exposure time as well

David Punsalan <david_punsalan@...> writes:

> You might try reducing your exposure time as well

Anyone doing photo exposures should get a step transmission gauge and
*test* their exposure, so that they *know* it's correctly exposed.
They're cheap and they take all the guesswork out of it.