Homebrew PCBs

I read somewhere on the web that a mercury vapour lamp with the outer uv blocking envelope removed gives a very good source of uv light for photo-pcb resist curing. Obviously removing the outer envelope would require that the uv exposure box be totally enclosed when the system is operating. Can any one confirm that this is comparable or better than the black-light fluorescent approach?
TIA
Regards
John C

Well mercury vapor bulbs are a popular choice for lighting amongst reptile owners because they offer a decent amount of UVB that is needed by a number of reptile species for proper vitamin D3 production but I don't know that it would be enough for curing the photo resist.  For that you might want to look at the UV bulbs used in aquarium and pond UV sterilizers.  They put out considerably more UV to the point that they can be hazardous if not totally enclosed.

  ----- Original Message ----- 
  From: John Craddock 
  To: Homebrew_PCBs@yahoogroups.com 
  Sent: Sunday, September 24, 2006 10:35 PM
  Subject: RE: [Homebrew_PCBs] UV Light Sources


  I read somewhere on the web that a mercury vapour lamp with the outer uv blocking envelope removed gives a very good source of uv light for photo-pcb resist curing. Obviously removing the outer envelope would require that the uv exposure box be totally enclosed when the system is operating. Can any one confirm that this is comparable or better than the black-light fluorescent approach?
  TIA
  Regards
  John C


   


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

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

From: "John Craddock" <John.Craddock@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Monday, September 25, 2006 3:35 AM
Subject: RE: [Homebrew_PCBs] UV Light Sources


>I read somewhere on the web that a mercury vapour lamp with the outer uv 
>blocking envelope removed gives a very good source of uv light for 
>photo-pcb resist curing. Obviously removing the outer envelope would 
>require that the uv exposure box be totally enclosed when the system is 
>operating. Can any one confirm that this is comparable or better than the 
>black-light fluorescent approach?

It's a lot better (much shorter expoosure), but needs to be a long way from 
the PCB/artwork for good collimation (something like 1 m, IIRC). I've got 
some similar sodium lamps that can have the outer envelope removed. The 
ballasts can be difficult to find. For accurate exposure I think you need 
some sort of shutter arrangement as they take some time to warm up.

Leon

>> John Craddock wrote:
>>
>>   I read somewhere on the web that a
>> mercury vapour lamp with the outer uv
>> blocking envelope removed gives a very
>> good source of uv light for photo-pcb
>> resist curing. Obviously removing the
>> outer envelope would require that the
>> uv exposure box be totally enclosed when
>> the system is operating. Can any one
>> confirm that this is comparable or
>> better than the black-light fluorescent
>> approach?

> WilliamK wrote:
>   Well mercury vapor bulbs are a popular
> choice for lighting amongst reptile owners 
> because they offer a decent amount of UVB
> that is needed by a number of reptile
> species for proper vitamin D3 production
> but I don't know that it would be enough
> for curing the photo resist.  For that you
> might want to look at the UV bulbs used in
> aquarium and pond UV sterilizers.  They put
> out considerably more UV to the point that
> they can be hazardous if not totally
> enclosed.

Yes the mecury vapour lamps work fine for
PCB resist.  Most expensive comercial
machines use them I think.

They also (as others have pointed out) need
to be run for a while to be up to temprature.

This means you either need to have some kind
of shutter to expose the PCB or as someone
else said (can't remeber who or when) you can
pre-heat them at a lower voltage and then up
the power for the exposure.

The light from them is also more like a point
source.  This has good and bad points.

I good point is that you can more easily
collimate the rays.  Bad point (as Leon-H
pointed out) you need to have the bulb at a
long distance from the PCB.


Fish tank STERILISING tubes are NOT suitable.
They are shorter wave length UV that is both
useless for the photoresist and dangerous.

AFAIK The arc lamps with covers removed also
produce dangerous UV rays as well as the
usefull (for PCBs) rays.

All up - I think that black light tubes are
probably the most convenient and easiest to
setup and use option.

They don't produce appreciable amounts of
dangerous UV.  Several of them in parallel
will put out plenty of UV.  They are easy
to get.  I think the biggest problem with
them is they don't seem to age gracefully
(at least im my experience they didn't)


If you can't get or have surplus arc lamps
then they should be great for PCBs though.

> -----Original Message-----
> From: Leon Heller [mailto:leon.heller@bulldoghome.com]
> Sent: 25 September 2006 16:27
> To: Homebrew_PCBs@yahoogroups.com
> Subject: Re: [Homebrew_PCBs] UV Light Sources
> >operating. Can any one confirm that this is comparable or 
> better than the 
> >black-light fluorescent approach?
> 
> It's a lot better (much shorter expoosure), but needs to be a 
> long way from 
> the PCB/artwork for good collimation (something like 1 m, 
> IIRC). I've got 
> some similar sodium lamps that can have the outer envelope 
> removed. The 
> ballasts can be difficult to find. For accurate exposure I 
> think you need 
> some sort of shutter arrangement as they take some time to warm up.
> 
> Leon 
Thanks Leon
For the collimation I was going to use a parabolic reflector. With a 16" (400mm) dia., reflector it would seem to be feasible to have a working exposure area of 12" to 18" (300 to 400mm) Instead of a shutter I was thinking of using a slide-in frame holder. In OZ we can get 250 watt self ballasting globes the run off our 240 volt mains supply. This set-up would be far less expensive than say 4 or 5 fluro tubes plus their associated ballasts, starters etc (at least in the antipodes).
Regards
John C

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

From: "John Craddock" <John.Craddock@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Monday, September 25, 2006 8:13 AM
Subject: RE: [Homebrew_PCBs] UV Light Sources


>
>
>> -----Original Message-----
>> From: Leon Heller [mailto:leon.heller@...]
>> Sent: 25 September 2006 16:27
>> To: Homebrew_PCBs@yahoogroups.com
>> Subject: Re: [Homebrew_PCBs] UV Light Sources
>> >operating. Can any one confirm that this is comparable or
>> better than the
>> >black-light fluorescent approach?
>>
>> It's a lot better (much shorter expoosure), but needs to be a
>> long way from
>> the PCB/artwork for good collimation (something like 1 m,
>> IIRC). I've got
>> some similar sodium lamps that can have the outer envelope
>> removed. The
>> ballasts can be difficult to find. For accurate exposure I
>> think you need
>> some sort of shutter arrangement as they take some time to warm up.
>>
>> Leon
> Thanks Leon
> For the collimation I was going to use a parabolic reflector. With a 16" 
> (400mm) dia., reflector it would seem to be feasible to have a working 
> exposure area of 12" to 18" (300 to 400mm) Instead of a shutter I was 
> thinking of using a slide-in frame holder. In OZ we can get 250 watt self 
> ballasting globes the run off our 240 volt mains supply. This set-up would 
> be far less expensive than say 4 or 5 fluro tubes plus their associated 
> ballasts, starters etc (at least in the antipodes).

I was going to remove the envelope from one of my sodium lamps, but the cat 
knocked it off the bench onto the floor and did it for me. 8-) I got some 
ceramic bulb holders without any problems, I really must get a ballast and 
try it out. I got the bulbs cheap on Ebay; I should have got one of the 
units you mention, it would have been less trouble.

Leon

>Most expensive comercial
>machines use them I think.

Search these archives on >Colight DMVL-930<. A fellow recently posted 
on a commercial setup here using twin mercury vapor bulbs that exposed 
both sides of the board at once. Craddock must have at least searched 
these archives for >mercury vapor< before starting this thread. Flags 
raise when "people play the fool to catch the wise", begging the 
question "What's his MO?".

--- In Homebrew_PCBs@yahoogroups.com, "Andrew" <andrewm1973@...> wrote:
>

We had two DMVL-930 exposure units for dry film photoresist and they
used 1000 watt bulbs. When I closed the PWB plant I kept the best one
for my home shop and junked the other one since nobody wanted it at
the time. 

I think the bulb part number is R1000 if my memory is correct. It's
just a standard 1000 watt mecury vapor bulb with a reflector. There is
no need to worry about collimation of the beam unless you are exposing
very large panels. Don't break the outer glass from the lamp unless
you want ozone. 

Just the other day I saw a lamp assembly that would be perfect for a
homebrew exposure unit. It was a mercury vapor lamp with reflector in
a metal enclosure at the base of a flagpole. This lamp looked like a
400 watt bulb but that would work great for dry film resist. Just
build a box around the lamp assembly and leave a slot at the bottom
for your contact frame to slide in and out. The bulb could be about 12
inches from the contact frame. 

At 400 watts I'm guessing about 45 seconds for exposure at 12 inches.
My system uses the 1000 watt lamps. They idle at 1000 watts and during
exposure they are overdriven to 1500 watts. Exposure time for DuPont
1.5 mil photoresist is 17 seconds. I do 5 mil lines and spaces daily
with this system. My film work is photoplotted on 7 mil thick films. 
Dry film resist is negative acting and has a fast exposure time.
Positive resists are slower and will take longer to expose.

Tom


--- In Homebrew_PCBs@yahoogroups.com, "John Craddock"
<John.Craddock@...> wrote:
>
> 
> 
> > -----Original Message-----
> > From: Leon Heller [mailto:leon.heller@...]
> > Sent: 25 September 2006 16:27
> > To: Homebrew_PCBs@yahoogroups.com
> > Subject: Re: [Homebrew_PCBs] UV Light Sources
> > >operating. Can any one confirm that this is comparable or 
> > better than the 
> > >black-light fluorescent approach?
> > 
> > It's a lot better (much shorter expoosure), but needs to be a 
> > long way from 
> > the PCB/artwork for good collimation (something like 1 m, 
> > IIRC). I've got 
> > some similar sodium lamps that can have the outer envelope 
> > removed. The 
> > ballasts can be difficult to find. For accurate exposure I 
> > think you need 
> > some sort of shutter arrangement as they take some time to warm up.
> > 
> > Leon 
> Thanks Leon
> For the collimation I was going to use a parabolic reflector. With a
16" (400mm) dia., reflector it would seem to be feasible to have a
working exposure area of 12" to 18" (300 to 400mm) Instead of a
shutter I was thinking of using a slide-in frame holder. In OZ we can
get 250 watt self ballasting globes the run off our 240 volt mains
supply. This set-up would be far less expensive than say 4 or 5 fluro
tubes plus their associated ballasts, starters etc (at least in the
antipodes).

> Regards
> John C
>

>There is no need to worry about collimation of the beam unless you 
>are exposing very large panels. 

Hear, hear!

--- In Homebrew_PCBs@yahoogroups.com, "twb8899" <twb8899@...> wrote:
>

> -----Original Message-----
> From: derekhawkins [mailto:eldata@...]
> Sent: 26 September 2006 00:18
> To: Homebrew_PCBs@yahoogroups.com
> Subject: [Homebrew_PCBs] Re: UV Light Sources
Snip
> Craddock must have at least searched 
> these archives for >mercury vapor< before starting this thread. Flags 
> raise when "people play the fool to catch the wise", begging the 
> question "What's his MO?".
> 
> --- In Homebrew_PCBs@yahoogroups.com, "Andrew" 
> <andrewm1973@...> wrote:
Derek
FYI in the English language we spell "vapor" as vapour, so a search missed it; sorry we don't have any American schools in OZ. Your insinuation in the snide comment above is pretty dammed offensive and totally uncalled for in a list such as this. FYI my "MO" is that over here a 250 watt mercury "vapour" globe of the self-ballasting variety costs AU$36 including the ceramic holder. Otoh 4 uv fluorescent tubes plus the control gear to go with them costs 5 times that amount. SAVING MONEY IS MY "MO".
Regards
John C

Tom, thank you very much for that information. I have a few questions mixed in context below.

> -----Original Message-----
> From: twb8899 [mailto:twb8899@...]
> Sent: 26 September 2006 04:17
> To: Homebrew_PCBs@yahoogroups.com
> Subject: [Homebrew_PCBs] Re: UV Light Sources
> 
> It's just a standard 1000 watt mecury vapor bulb with a reflector. There is
> no need to worry about collimation of the beam unless you are exposing
> very large panels. Don't break the outer glass from the lamp unless
> you want ozone.
Is the reflector built into the globe i.e.. is it a PAR type globe or is it separate?
> 
> Just the other day I saw a lamp assembly that would be perfect for a
> homebrew exposure unit. It was a mercury vapor lamp with reflector in
> a metal enclosure at the base of a flagpole. This lamp looked like a
> 400 watt bulb but that would work great for dry film resist. Just
> build a box around the lamp assembly and leave a slot at the bottom
> for your contact frame to slide in and out. The bulb could be about 12
> inches from the contact frame. 
> 
I was going to use a 250 watt self-ballasting globe. Do you think that would be OK?

> At 400 watts I'm guessing about 45 seconds for exposure at 12 inches.
> My system uses the 1000 watt lamps. They idle at 1000 watts and during
> exposure they are overdriven to 1500 watts. Exposure time for DuPont
> 1.5 mil photoresist is 17 seconds. I do 5 mil lines and spaces daily
> with this system. My film work is photoplotted on 7 mil thick films. 
> Dry film resist is negative acting and has a fast exposure time.
> Positive resists are slower and will take longer to expose.
> 
Would you use a similar distance of 12 inches for a 250 watt unit?
Would 2 * 250 watt globes be a better way to go? I will be exposing Kinsten positive resist PCBs
> Tom

Once again Tom thank you for your guidance.
Regards
John C

>FYI in the English language we spell "vapor" as vapour, so a search 
>missed it

Missed what? Searching on >mercury vapour< gives another set of hits 
including this;

>>DO NOT break the outer glass shell of a mercury vapour lamp! It 
>>will radiate a lot of short wave UV (UV-A) which is dangerous for 
>>eyes and skin, and it generates lot of ozone (O3). Good results 
>>could be obtained without breaking the outer glass shell.

>Your insinuation in the snide comment above is pretty dammed 
>offensive and totally uncalled for in a list such as this.

I'm inquisitive too...What are you really up to? You're coming 
across like a "Man dressed in black".

--- In Homebrew_PCBs@yahoogroups.com, "John Craddock" 
<John.Craddock@...> wrote:
>

derekhawkins wrote:
>>There is no need to worry about collimation of the beam unless you 
>>are exposing very large panels. 
> 
> Hear, hear!

I made a UV lightbox with a 125Watt HID lamp (HPR-125) 24" from the glass,
and in a cylindrical parabolic reflector (lamp lays horizontal). 90%+ exposure
happens in 30secs, and i found a good optimum to use is 90secs for
pre-coated negative pcb. The pcb is held against the glass by the lid
that has a layer of sponge.

Without the reflector and beam collimation, you'll need a bigger globe
for the same exposure time.

> -----Original Message-----
> From: derekhawkins [mailto:eldata@...]
> Sent: 26 September 2006 10:05
> To: Homebrew_PCBs@yahoogroups.com
> Subject: [Homebrew_PCBs] Re: UV Light Sources
> 
> 
> >FYI in the English language we spell "vapor" as vapour, so a search 
> >missed it
> 
> Missed what? Searching on >mercury vapour< gives another set of hits 
> including this;
> 
> >>DO NOT break the outer glass shell of a mercury vapour lamp! It 
> >>will radiate a lot of short wave UV (UV-A) which is dangerous for 
> >>eyes and skin, and it generates lot of ozone (O3). Good results 
> >>could be obtained without breaking the outer glass shell.
That was precisely the reason for my question (see the first post on this thread). I understand from my web searching that UV-A is the radiation band that actively polymerises the UV resist. I further understand that the more intense the UV-A radiation is the quicker the polymerisation. I have also read that the quicker the exposure, the better is the definition achievable. Seeing as the exposure unit would be fully enclosed, I don't see a problem with the eyes and skin bit. Anyway, from the research that I have done, it seems that the dangerous radiation bands are UV-B and UV-C; so your quotation is quite incorrect on that point but the UV-B and UV-C also is unblocked by breaking the glass filter. So the recommendation in that excerpt is appropriate for some purposes. However it is out of context so I cannot tell. The so-called solariums (facial tanners) rely on UV-A as their active radiation ingredient so it cannot be too harmful. Ozone has got me a bit worried though.
Still trying to get a range of views on whether mercury vapour is a better way to go than fluorescent.

> I'm inquisitive too...What are you really up to? You're coming 
> across like a "Man dressed in black".
> 
That is your opinion. Problem with the English language I guess. Re-read the thread and reflect on whether you are being just a teensy bit paranoid.
Regards
John C

> Tom, thank you very much for that information. I have a few
questions mixed in context below.
> 
> > -----Original Message-----
> > From: twb8899 [mailto:twb8899@...]
> > Sent: 26 September 2006 04:17
> > To: Homebrew_PCBs@yahoogroups.com
> > Subject: [Homebrew_PCBs] Re: UV Light Sources
> > 
> > It's just a standard 1000 watt mecury vapor bulb with a reflector.
There is
> > no need to worry about collimation of the beam unless you are exposing
> > very large panels. Don't break the outer glass from the lamp unless
> > you want ozone.

> Is the reflector built into the globe i.e.. is it a PAR type globe
or is it separate?

The reflectors in my exposure unit are external to the lamp. They are
    made of thin polished aluminum sheet. You could probably just use
some cheap glass mirrors to do the same thing. 


> > 
> > Just the other day I saw a lamp assembly that would be perfect for a
> > homebrew exposure unit. It was a mercury vapor lamp with reflector in
> > a metal enclosure at the base of a flagpole. This lamp looked like a
> > 400 watt bulb but that would work great for dry film resist. Just
> > build a box around the lamp assembly and leave a slot at the bottom
> > for your contact frame to slide in and out. The bulb could be about 12
> > inches from the contact frame. 
> > 


> I was going to use a 250 watt self-ballasting globe. Do you think
that would be OK?

I think a 250 watt bulb would work ok. Give it a try without the
reflectors first and you may find that it works fine for smaller boards.


> 
> > At 400 watts I'm guessing about 45 seconds for exposure at 12 inches.
> > My system uses the 1000 watt lamps. They idle at 1000 watts and during
> > exposure they are overdriven to 1500 watts. Exposure time for DuPont
> > 1.5 mil photoresist is 17 seconds. I do 5 mil lines and spaces daily
> > with this system. My film work is photoplotted on 7 mil thick films. 
> > Dry film resist is negative acting and has a fast exposure time.
> > Positive resists are slower and will take longer to expose.
> > 
> Would you use a similar distance of 12 inches for a 250 watt unit?
> Would 2 * 250 watt globes be a better way to go? I will be exposing
Kinsten positive resist PCBs

I'm not familiar with Kinsten resist. You mentioned that it is
positive acting so it may take longer to expose no matter what type of
lamp you use. Try the 12 inche distance first and see how it works out.

I saw another mercury lamp this evening that was being used to light
up the side of a building. This one did have a 400 watt bulb and it
would make an excellent exposure unit. It had a polished stainless
steel reflector around the lamp. Check out one of these lamps to get
an idea of how it's set up. 

BTW, my 1000 watt system also does a good job with silk screens. The
Autotype Five-Star emulsion takes 30 seconds and the diazo liquid
types take 90 seconds.

No matter what type of bulb you use it is a good idea to get a
Stouffer 21 step exposure strip to test your exposure times. If you
take just a little bit of time to calibrate your system the results
will be excellent. These Stouffer 21 step test strips are inexpensive
and a good tool to have on hand if you do any work with photoresist.


Tom

> Once again Tom thank you for your guidance.
> Regards
> John C
>

> -----Original Message-----
> From: Russell Shaw [mailto:rjshaw@netspace.net.au]
> Sent: 26 September 2006 12:17
> To: Homebrew_PCBs@...m
> Subject: Re: [Homebrew_PCBs] Re: UV Light Sources

> I made a UV lightbox with a 125Watt HID lamp (HPR-125) 24" 
> from the glass,
> and in a cylindrical parabolic reflector (lamp lays 
> horizontal). 90%+ exposure
> happens in 30secs, and i found a good optimum to use is 90secs for
> pre-coated negative pcb. The pcb is held against the glass by the lid
> that has a layer of sponge.
> 
> Without the reflector and beam collimation, you'll need a bigger globe
> for the same exposure time.
> 

Thank you very much for that information Russell. Points like your experience on the exposure time and distance between light source and object provide a real contribution to my knowledge base and, no-doubt, many others on this list on this matter.
Regards
John C

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

From: "John Craddock" <John.Craddock@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, September 26, 2006 4:07 AM
Subject: RE: [Homebrew_PCBs] Re: UV Light Sources


>
>
>> -----Original Message-----
>> From: derekhawkins [mailto:eldata@...]
>> Sent: 26 September 2006 10:05
>> To: Homebrew_PCBs@yahoogroups.com
>> Subject: [Homebrew_PCBs] Re: UV Light Sources
>>
>>
>> >FYI in the English language we spell "vapor" as vapour, so a search
>> >missed it
>>
>> Missed what? Searching on >mercury vapour< gives another set of hits
>> including this;
>>
>> >>DO NOT break the outer glass shell of a mercury vapour lamp! It
>> >>will radiate a lot of short wave UV (UV-A) which is dangerous for
>> >>eyes and skin, and it generates lot of ozone (O3). Good results
>> >>could be obtained without breaking the outer glass shell.
> That was precisely the reason for my question (see the first post on this 
> thread). I understand from my web searching that UV-A is the radiation 
> band that actively polymerises the UV resist. I further understand that 
> the more intense the UV-A radiation is the quicker the polymerisation. I 
> have also read that the quicker the exposure, the better is the definition 
> achievable. Seeing as the exposure unit would be fully enclosed, I don't 
> see a problem with the eyes and skin bit. Anyway, from the research that I 
> have done, it seems that the dangerous radiation bands are UV-B and UV-C; 
> so your quotation is quite incorrect on that point but the UV-B and UV-C 
> also is unblocked by breaking the glass filter. So the recommendation in 
> that excerpt is appropriate for some purposes. However it is out of 
> context so I cannot tell. The so-called solariums (facial tanners) rely on 
> UV-A as their active radiation ingredient so it cannot be too harmful. 
> Ozone has got me a bit worried though.

Several people remove the outer envelope, it has to be done with sodium 
vapour lamps anyway. I think that the Hg lamps will emit a lot of UV as it 
is. I used to get a lot of ozone from EPROM eraser tubes (germicidal tubes), 
so I'm used to it. It gets converted to O2 quite quickly, and the main 
effect is as an irritant. We will only have it on for a few minutes at a 
time, so I can't see it being a problem.

They used to pump O3 throught the London Underground system at night, to 
kill germs. Perhaps they still do. I think a carbon filter will remove O3, 
they are used on photocopiers, which used to emit lots of ozone. At any 
rate, the old Xerox ones did - I used to work for Rank-Xerox (UK). It was 
produced by the corotron which charged the photoreceptor.

Leon
--
Leon Heller, G1HSM
Suzuki SV1000S motorcycle
leon.heller@...
http://www.geocities.com/leon_heller

--- In Homebrew_PCBs@yahoogroups.com, "John Craddock"
<John.Craddock@...> wrote:
>
> 
> 
> > -----Original Message-----
> > From: derekhawkins [mailto:eldata@...]
> > Sent: 26 September 2006 00:18
> > To: Homebrew_PCBs@yahoogroups.com
> > Subject: [Homebrew_PCBs] Re: UV Light Sources
> Snip
> > Craddock must have at least searched 
> > these archives for >mercury vapor< before starting this thread. Flags 
> > raise when "people play the fool to catch the wise", begging the 
> > question "What's his MO?".
> > 
> > --- In Homebrew_PCBs@yahoogroups.com, "Andrew" 
> > <andrewm1973@> wrote:
> Derek
> FYI in the English language we spell "vapor" as vapour, so a search
missed it; sorry we don't have any American schools in OZ. Your
insinuation in the snide comment above is pretty dammed offensive and
totally uncalled for in a list such as this. FYI my "MO" is that over
here a 250 watt mercury "vapour" globe of the self-ballasting variety
costs AU$36 including the ceramic holder. Otoh 4 uv fluorescent tubes
plus the control gear to go with them costs 5 times that amount.
SAVING MONEY IS MY "MO".
> Regards
> John C

Please watch your language and your temper.

FYI, that's American English.... ;')

Derek, I must have missed something, I wasn't picking up any ulterior
(ulteriour?) motives.

Steve Greenfield

--- In Homebrew_PCBs@yahoogroups.com, "derekhawkins" <eldata@...> wrote:
>
...
> I'm inquisitive too...What are you really up to? You're coming 
> across like a "Man dressed in black".

I'm sorry to do this, but since you continue to be combatative and are
attempting to bait, you are now on moderated status.

Steve Greenfield
listowner

>Without the reflector and beam collimation, you'll need a bigger 
>globe for the same exposure time.

This is more to do with focus than collimation. Parallel rays would be 
better than divergent rays but convergent rays would even be better 
than parallel rays if shortest exposure time was the only goal.

--- In Homebrew_PCBs@yahoogroups.com, Russell Shaw <rjshaw@...> wrote:
>

Hello Leon,

  Tuesday, September 26, 2006, 9:52:31 AM, you wrote:

Some snippings :) and replies inbetween the lines

>>> >>DO NOT break the outer glass shell of a mercury vapour lamp! It
>>> >>will radiate a lot of short wave UV (UV-A) which is dangerous for
                                           UV-C (UV-A) is long wave UV

>>> >>eyes and skin, and it generates lot of ozone (O3). Good results
>>> >>could be obtained without breaking the outer glass shell.

>> That was precisely the reason for my question (see the first post on this 
>> thread). I understand from my web searching that UV-A is the radiation
            Good one! Polymerisation is affected by UV-A
>> band that actively polymerises the UV resist. I further understand that 
...
>> have done, it seems that the dangerous radiation bands are UV-B and UV-C;
>> so your quotation is quite incorrect on that point but the UV-B and UV-C 
>> also is unblocked by breaking the glass filter. So the recommendation in
           Absolutely true

>> that excerpt is appropriate for some purposes. However it is out of 
>> context so I cannot tell. The so-called solariums (facial tanners) rely on 
>> UV-A as their active radiation ingredient so it cannot be too harmful. 
>> Ozone has got me a bit worried though.

> Several people remove the outer envelope, it has to be done with sodium 
> vapour lamps anyway. I think that the Hg lamps will emit a lot of UV as it 
> is. I used to get a lot of ozone from EPROM eraser tubes (germicidal tubes),

Germicidal tubes (real ones produced by Phillips os Osram do not emmit
ozone. Their glass and gas combination are specificially formulated so
that these lamps do not emmit ozone.

> so I'm used to it. It gets converted to O2 quite quickly, and the main 
> effect is as an irritant. We will only have it on for a few minutes at a 
> time, so I can't see it being a problem.

> They used to pump O3 throught the London Underground system at night, to 
> kill germs. Perhaps they still do. I think a carbon filter will remove O3, 
> they are used on photocopiers, which used to emit lots of ozone. At any 
> rate, the old Xerox ones did - I used to work for Rank-Xerox (UK). It was 
> produced by the corotron which charged the photoreceptor.

> Leon
> --
> Leon Heller, G1HSM
> Suzuki SV1000S motorcycle
> leon.heller@...
> http://www.geocities.com/leon_heller 

For  more  mine  replies  on  this  subject  please take a look at the
following messages in this group:
249
250
4116
13065
13086

-- 
 Best regards,
 Zoran A. Scepanovic
 zastos@...

*********
RAM = Rarely Adequate Memory
*********

Please be advised what was said may be absolutely wrong, and hereby this disclaimer follows.  I reserve the right to be wrong and admit it in front of the entire world.



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

derekhawkins wrote:
>>Without the reflector and beam collimation, you'll need a bigger 
>>globe for the same exposure time.
> 
> This is more to do with focus than collimation. Parallel rays would be 
> better than divergent rays but convergent rays would even be better 
> than parallel rays if shortest exposure time was the only goal.

That's just a roundabout way of saying you get the fastest exposure by
focusing all the light to a smaller area, maximizing the power density.

I designed the reflector to give parallel rays, and the result shows as
an even power density of the size larger than an A4 sheet.

>That's just a roundabout way of saying you get the fastest exposure 
>by focusing all the light to a smaller area, maximizing the power 
>density.

If you remove the reflector and put a collimator in front of the lamp 
you'll get your collimation without focus. Yes, nice low intensity 
parallel rays. 

--- In Homebrew_PCBs@yahoogroups.com, Russell Shaw <rjshaw@...> wrote:
>

> -----Original Message-----
> From: Steve [mailto:alienrelics@...]
> Sent: 27 September 2006 00:13
> To: Homebrew_PCBs@yahoogroups.com
> Subject: [Homebrew_PCBs] Re: UV Light Sources

> 
> Please watch your language and your temper.
> 
> FYI, that's American English.... ;')
> 
> Derek, I must have missed something, I wasn't picking up any ulterior
> (ulteriour?) motives.
> 
> Steve Greenfield
Well Steve you just created another lurker. Sorry I asked the question.
Regards
John C

So basically UVB is useless for photoresist and it's UVA output that's key?  Wouldn't 
a full spectrum plant bulb work fairly well then?  If I recall most put out a fair amount of UVA
and fairly cost effective.

  Andrew wrote:



  Yes the mecury vapour lamps work fine for
  PCB resist. Most expensive comercial
  machines use them I think.

  They also (as others have pointed out) need
  to be run for a while to be up to temprature.

  This means you either need to have some kind
  of shutter to expose the PCB or as someone
  else said (can't remeber who or when) you can
  pre-heat them at a lower voltage and then up
  the power for the exposure.

  The light from them is also more like a point
  source. This has good and bad points.

  I good point is that you can more easily
  collimate the rays. Bad point (as Leon-H
  pointed out) you need to have the bulb at a
  long distance from the PCB.

  Fish tank STERILISING tubes are NOT suitable.
  They are shorter wave length UV that is both
  useless for the photoresist and dangerous.

  AFAIK The arc lamps with covers removed also
  produce dangerous UV rays as well as the
  usefull (for PCBs) rays.

  All up - I think that black light tubes are
  probably the most convenient and easiest to
  setup and use option.

  They don't produce appreciable amounts of
  dangerous UV. Several of them in parallel
  will put out plenty of UV. They are easy
  to get. I think the biggest problem with
  them is they don't seem to age gracefully
  (at least im my experience they didn't)

  If you can't get or have surplus arc lamps
  then they should be great for PCBs though.



   


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

Just something else that occured to me in regards to MV bulbs put to use for photoresist.
If you want to find them cheap/free make friends with some local reptile owners.  Many of us
use them for the UVB that they emitt for a number of reptiles that require UVB for Vit D3 
systhesis.  The kicker is that UVB levels drop off to a point of being of no use for us
and as a result have to be replaced.  However, they should still emitt plenty of UVA which would
longer wavelength UV.

  Also beware of the self ballasting MV bulbs.  I know of several people
that have had issues with them since the filaments tend to be quite fragile, especially when hot.
I have yet to hear of someone experiencing a failure with an externally ballasted bulb though.

  ----- Original Message ----- 
  From: Leon Heller 
  To: Homebrew_PCBs@yahoogroups.com 
  Sent: Monday, September 25, 2006 2:26 AM
  Subject: Re: [Homebrew_PCBs] UV Light Sources


  ----- Original Message ----- 
  From: "John Craddock" <John.Craddock@...>
  To: <Homebrew_PCBs@yahoogroups.com>
  Sent: Monday, September 25, 2006 3:35 AM
  Subject: RE: [Homebrew_PCBs] UV Light Sources

  >I read somewhere on the web that a mercury vapour lamp with the outer uv 
  >blocking envelope removed gives a very good source of uv light for 
  >photo-pcb resist curing. Obviously removing the outer envelope would 
  >require that the uv exposure box be totally enclosed when the system is 
  >operating. Can any one confirm that this is comparable or better than the 
  >black-light fluorescent approach?

  It's a lot better (much shorter expoosure), but needs to be a long way from 
  the PCB/artwork for good collimation (something like 1 m, IIRC). I've got 
  some similar sodium lamps that can have the outer envelope removed. The 
  ballasts can be difficult to find. For accurate exposure I think you need 
  some sort of shutter arrangement as they take some time to warm up.

  Leon 



   


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

derekhawkins wrote:
 >Russell Shaw wrote:
 >> derekhawkins wrote:
 >>
 >>>>Russell Shaw wrote:
 >>>>Without the reflector and beam collimation, you'll need a bigger
 >>>>globe for the same exposure time.
 >>>
 >>>This is more to do with focus than collimation. Parallel rays would be
 >>>better than divergent rays but convergent rays would even be better
 >>>than parallel rays if shortest exposure time was the only goal.
 >>
 >> That's just a roundabout way of saying you get the fastest exposure by
 >> focusing all the light to a smaller area, maximizing the power density.

 > If you remove the reflector and put a collimator in front of the lamp
 > you'll get your collimation without focus. Yes, nice low intensity
 > parallel rays.

If you put a collimator (lens) in front of an isotropic light source such
that the cone of interception is 90 degrees (quite efficient for a lense setup),
then you'll only collimate 15% of the light (the other 85% is lost).

My cylindrical parabolic reflector intercepts light 270 degrees around the globe,
so 75% of the light is reflected. Because it is only parabolic in one axis, more
light is not collimated in the other axis, so hits the box sides.

Because the globe is laying horizontal and there is no light emission along the
axis of the globe, then not as much efficiency is lost.

The efficiency is certainly triple that of a lens collimator of similar area.

   "Yes, nice low intensity parallel rays."

The intensity of parallel rays does not decrease with distance.

By using 24" of distance, the divergent rays from the globe is quite low
and the parallel rays are much more intense.

 >> I designed the reflector to give parallel rays, and the result shows as
 >> an even power density of the size larger than an A4 sheet.

--- In Homebrew_PCBs@yahoogroups.com, "John Craddock"
<John.Craddock@...> wrote:
>
> 
> 
> > -----Original Message-----
> > From: Steve [mailto:alienrelics@...]
> > Sent: 27 September 2006 00:13
> > To: Homebrew_PCBs@yahoogroups.com
> > Subject: [Homebrew_PCBs] Re: UV Light Sources
> 
> > 
> > Please watch your language and your temper.
> > 
> > FYI, that's American English.... ;')
> > 
> > Derek, I must have missed something, I wasn't picking up any ulterior
> > (ulteriour?) motives.
> > 
> > Steve Greenfield

> Well Steve you just created another lurker. Sorry I asked the question.
> 

Huh? I was taking Derek to task. How have I offended you?

Steve Greenfield

Also, remember window soda glass shuts off anything below 270nm so that 
includes _all_ UVB. I haven't done side by side comparisons between the 
various HID MV lamps, but I do know that standard phosphorised MV "white 
dulux" works pretty well for photoresist. Might be better to get a clear 
MV or the more expensive Philips 125W MV blacklight. Clear MV bulbs may 
be available in the electrical section at supermarkets in the USA, but 
here in Australia, clear bulbs are rare as hens teeth. I was forced to 
buy a bulb with the phosphor coated.

As now everyone seems to be aware that photoresist are primarily 
sensitivity to UVA, then buying specialized UV MV lamps will only waste 
your money.

See figure 1 in,

http://www2.dupont.com/Imaging_Materials/en_US/assets/downloads/tech_bulletins/tb0169.pdf


My setup parameters are:

Lamp: 400W "dulux white" MV HID bulb,
Distance to PCB = 300mm
Materials in light: 3mm windows glass + 0.2mm inkjet Epson transparency film
Photoresist: "dry film" negative
Exposure time: 80 to 120 seconds

I would recommend 250W MV, as more suitable size for hobby work.




william.kroyer@... wrote:

>   So basically UVB is useless for photoresist and it's UVA output that's key?  Wouldn't 
> a full spectrum plant bulb work fairly well then?  If I recall most put out a fair amount of UVA
> and fairly cost effective.
> 
>   Andrew wrote:
> 
> 
> 
>   Yes the mecury vapour lamps work fine for
>   PCB resist. Most expensive comercial
>   machines use them I think.
> 
>   They also (as others have pointed out) need
>   to be run for a while to be up to temprature.
> 
>   This means you either need to have some kind
>   of shutter to expose the PCB or as someone
>   else said (can't remeber who or when) you can
>   pre-heat them at a lower voltage and then up
>   the power for the exposure.
> 
>   The light from them is also more like a point
>   source. This has good and bad points.
> 
>   I good point is that you can more easily
>   collimate the rays. Bad point (as Leon-H
>   pointed out) you need to have the bulb at a
>   long distance from the PCB.
> 
>   Fish tank STERILISING tubes are NOT suitable.
>   They are shorter wave length UV that is both
>   useless for the photoresist and dangerous.
> 
>   AFAIK The arc lamps with covers removed also
>   produce dangerous UV rays as well as the
>   usefull (for PCBs) rays.
> 
>   All up - I think that black light tubes are
>   probably the most convenient and easiest to
>   setup and use option.
> 
>   They don't produce appreciable amounts of
>   dangerous UV. Several of them in parallel
>   will put out plenty of UV. They are easy
>   to get. I think the biggest problem with
>   them is they don't seem to age gracefully
>   (at least im my experience they didn't)
> 
>   If you can't get or have surplus arc lamps
>   then they should be great for PCBs though.
> 
> 
> 
>    
> 
> 
> [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_PCBs
> 
> If Files or Photos are running short of space, post them here:
> http://groups.yahoo.com/group/Homebrew_PCBs_Archives/ 
> Yahoo! Groups Links
> 
> 
> 
> 
> 
> 
> 
> 
> 
>

--- In Homebrew_PCBs@yahoogroups.com, "derekhawkins" <eldata@...> wrote:
>
> >Most expensive comercial
> >machines use them I think.
> 
> Search these archives on >Colight DMVL-930<. A fellow recently posted 
> on a commercial setup here using twin mercury vapor bulbs that exposed 
> both sides of the board at once. Craddock must have at least searched 
> these archives for >mercury vapor< before starting this thread. Flags 
> raise when "people play the fool to catch the wise", begging the 
> question "What's his MO?".

I don't know what you have against John Craddock, but I don't tolerate
bullying.

Derek, you are on moderated status.

Steve Greenfield
listowner

>Derek, you are on moderated status.

Thought I was already in the "dog house". LOL!

--- In Homebrew_PCBs@yahoogroups.com, "Steve" <alienrelics@...> wrote:
>

In article <efenve+kenr@...>,
   Steve <alienrelics@...> wrote:
> Huh? I was taking Derek to task. How have I offended you?

> Steve Greenfield

Probably because your comment appears to be to John's post, at least
that's how it appears to me viz:

----------------------------------------------------------------------
> FYI in the English language we spell "vapor" as vapour, so a search
> missed it; sorry we don't have any American schools in OZ. Your
> insinuation in the snide comment above is pretty dammed offensive and
> totally uncalled for in a list such as this. FYI my "MO" is that ove
> here a 250 watt mercury "vapour" globe of the self-ballasting variety
> costs AU$36 including the ceramic holder. Otoh 4 uv fluorescent tubes
> plus the control gear to go with them costs 5 times that amount. SAVING
> MONEY IS > MY "MO".

> Regards
> John C

Please watch your language and your temper.

FYI, that's American English.... ;')

----------------------------------------------------------------------

--- In Homebrew_PCBs@yahoogroups.com, lists <stuart.winsor.lists@...>
wrote:
>
> In article <efenve+kenr@...>,
>    Steve <alienrelics@...> wrote:
> > Huh? I was taking Derek to task. How have I offended you?
> 
> > Steve Greenfield
> 
> Probably because your comment appears to be to John's post, at least
> that's how it appears to me viz:

I spoke to him off list and we've got it all sorted out. I was upset
at Derek for baiting, and John for taking the bait. It didn't help
that one of my posts took days to show up, so it looked like I was
coming down on John while giving Derek a pass. I think it's sorted out
now.

Steve Greenfield
owner Homebrew_PCBs