Homebrew PCBs

I am going to start doing some experimenting with dry film resist. I
have just placed an order for a roll from Think Tink.

Since it is way more than what I need, I am planning to sell the
excess. I plan on selling in 5 foot lengths, which should be enough
for people to experiment around with. 

Figuring out time, costs, shipping materials and shipping charges I
expect to charge $20. 

The price includes UPS ground shipping within the continental US. If
you want it sooner or live outside the continental US, contact me
directly by email and we can try to make other arrangements.

If you are interested, send me a private email and I will let you know
when it is available. I plan on setting up payment through Google
Checkout or personal check. If other payment methods are desired, let
me know and I will try to accommodate you. 

Taking into account shipping time, I should be able to take orders in
one to two weeks.

BTW, I ran this by Steve ahead of time so I would not run afoul of any
spamming rules. 

Damon

In article <fmtkv7+ji9s@...>,
   javaguy11111 <javaguy11111@yahoo.com> wrote:
> Since it is way more than what I need, I am planning to sell the
> excess. I plan on selling in 5 foot lengths, which should be enough
> for people to experiment around with. 

Sounds a good idea but I rather suspect that shipping to the UK or Europe
would be too costly, especially if we found ourselves paying customs
charges on top.

The UK post office charges £8, around $16, to collect the charge on behalf
of customs and excise dept

You may want to contact Elga's representative in the UK then. Might be 
that there are more users here from the UK which would be interested also?

Elga Europe Ltd
3 Stephenson Close Daventry Northants NN11 5RF UK
elgaeuropeltd@... <mailto:elgaeuropeltd@...>

Markus

PS: I'm not at all related to any of the firms whoes adress I posted 
lately.

lists schrieb:

>
> In article <fmtkv7+ji9s@... <mailto:fmtkv7%2Bji9s%40eGroups.com>>,
> javaguy11111 <javaguy11111@... 
> <mailto:javaguy11111%40yahoo.com>> wrote:
> > Since it is way more than what I need, I am planning to sell the
> > excess. I plan on selling in 5 foot lengths, which should be enough
> > for people to experiment around with.
>
> Sounds a good idea but I rather suspect that shipping to the UK or Europe
> would be too costly, especially if we found ourselves paying customs
> charges on top.
>
> The UK post office charges \ufffd8, around $16, to collect the charge on behalf
> of customs and excise dept
>

Maybe someone in Europe will set up a similar group purchase if there
are enough users?
Within the EU should suffice to thwart the infamous UK blackmailers ;-)

Anyway, not me, i have no desire to go back to photoprocess.

ST

On Jan 19, 2008 9:43 PM, lists <stuart.winsor.lists@...> wrote:

> Sounds a good idea but I rather suspect that shipping to the UK or Europe
> would be too costly, especially if we found ourselves paying customs
> charges on top.
>
> The UK post office charges £8, around $16, to collect the charge on behalf
> of customs and excise dept
>
>

In article <47926429.6000501@...>,
   Markus Zingg <homebrew-pcb@...> wrote:

> Elga Europe Ltd
> 3 Stephenson Close Daventry Northants NN11 5RF UK
> elgaeuropeltd@... <mailto:elgaeuropeltd@...>

Thank you. I live about 25 miles from Daventry and used to work there! I
did not know of their existance

However they do not give much information on their website.

On the other hand http://www.megauk.com/ do and having dealt with them
before (though on behalf of my former employer as an engineer buying stuff
for work) I would probably go to them.

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

From: "lists" <stuart.winsor.lists@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Saturday, January 19, 2008 9:43 PM
Subject: Re: [Homebrew_PCBs] Small Quntities of Dry Film Resist


In article <fmtkv7+ji9s@...>,
   javaguy11111 <javaguy11111@...> wrote:
> Since it is way more than what I need, I am planning to sell the
> excess. I plan on selling in 5 foot lengths, which should be enough
> for people to experiment around with.

Sounds a good idea but I rather suspect that shipping to the UK or Europe
would be too costly, especially if we found ourselves paying customs
charges on top.

The UK post office charges \ufffd8, around $16, to collect the charge on behalf
of customs and excise dept



Only if it costs more than \ufffd33, IIRC.

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

On Sat, 19 Jan 2008, lists wrote:

> In article <fmtkv7+ji9s@...>,
>    javaguy11111 <javaguy11111@...> wrote:
> > Since it is way more than what I need, I am planning to sell the
> > excess. I plan on selling in 5 foot lengths, which should be enough
> > for people to experiment around with.
>
> Sounds a good idea but I rather suspect that shipping to the UK or Europe
> would be too costly, especially if we found ourselves paying customs
> charges on top.

Dunno about UK customs, but Isle of Man Customs typically don't bother if
a package is less than $100 or so. I've had all sorts of things sent from
the USA, and apart from a customs stamp they haven't bothered it further.

Strangely enough, they seem to examine my packages of nixie tubes from
Ukraine a lot more closely than the various bits I have sent from the USA!

In article <Pine.LNX.4.58.0801201325410.14584@...>,
   Dylan Smith <dyls@...> wrote:
> > Sounds a good idea but I rather suspect that shipping to the UK or Europe
> > would be too costly, especially if we found ourselves paying customs
> > charges on top.

> Dunno about UK customs, but Isle of Man Customs typically don't bother if
> a package is less than $100 or so. I've had all sorts of things sent from
> the USA, and apart from a customs stamp they haven't bothered it further.

You're lucky, my experience is that anything over about £18 ($35?) you get
stung in mainland UK

Just an update. I have received the resist and shipping materials. 

I decided to use USPS instead of UPS because I have had more requests
for it. I will also be using paypal instead of google checkout. Again
more people were requesting that.  I am trying to keep things simple.

I should be ready to start shipping by Monday and should have payment
information posted before the weekend is up.

Damon

--- In Homebrew_PCBs@yahoogroups.com, "javaguy11111"
<javaguy11111@...> wrote:

>
> I am going to start doing some experimenting with dry film resist. I
> have just placed an order for a roll from Think Tink.
> 
> Since it is way more than what I need, I am planning to sell the
> excess. I plan on selling in 5 foot lengths, which should be enough
> for people to experiment around with. 
> 
> Figuring out time, costs, shipping materials and shipping charges I
> expect to charge $20. 
> 
> The price includes UPS ground shipping within the continental US. If
> you want it sooner or live outside the continental US, contact me
> directly by email and we can try to make other arrangements.
> 
> If you are interested, send me a private email and I will let you know
> when it is available. I plan on setting up payment through Google
> Checkout or personal check. If other payment methods are desired, let
> me know and I will try to accommodate you. 
> 
> Taking into account shipping time, I should be able to take orders in
> one to two weeks.
> 
> BTW, I ran this by Steve ahead of time so I would not run afoul of any
> spamming rules. 
> 
> Damon
>

The photoresist is ready for shipping. It is 5 feet long and was cut
off from a 100ft roll that I purchased from ThinkTink. I have 18 rolls
available and 4 people have contacted me. So there is plenty left, if
anyone wants to give it a try.

If ordering inside the US, the cost is $20 and shipping is by USPS.

If ordering outside the US, the cost is $25 and shipping is by USPS.
You are responsible for any customs charges

I am using PayPal.

Everyone who has emailed already, I have sent a reply with payment
information. If you did send me an email, but have not heard from me
then send me another email.

Damon 
--- In Homebrew_PCBs@yahoogroups.com, "javaguy11111"
<javaguy11111@...> wrote:

>
> Just an update. I have received the resist and shipping materials. 
> 
> I decided to use USPS instead of UPS because I have had more requests
> for it. I will also be using paypal instead of google checkout. Again
> more people were requesting that.  I am trying to keep things simple.
> 
> I should be ready to start shipping by Monday and should have payment
> information posted before the weekend is up.
> 
> Damon
> 
> --- In Homebrew_PCBs@yahoogroups.com, "javaguy11111"
> <javaguy11111@> wrote:
> >
> > I am going to start doing some experimenting with dry film resist. I
> > have just placed an order for a roll from Think Tink.
> > 
> > Since it is way more than what I need, I am planning to sell the
> > excess. I plan on selling in 5 foot lengths, which should be enough
> > for people to experiment around with. 
> > 
> > Figuring out time, costs, shipping materials and shipping charges I
> > expect to charge $20. 
> > 
> > The price includes UPS ground shipping within the continental US. If
> > you want it sooner or live outside the continental US, contact me
> > directly by email and we can try to make other arrangements.
> > 
> > If you are interested, send me a private email and I will let you know
> > when it is available. I plan on setting up payment through Google
> > Checkout or personal check. If other payment methods are desired, let
> > me know and I will try to accommodate you. 
> > 
> > Taking into account shipping time, I should be able to take orders in
> > one to two weeks.
> > 
> > BTW, I ran this by Steve ahead of time so I would not run afoul of any
> > spamming rules. 
> > 
> > Damon
> >
>

Hi Damon

5feet long but how wide is it and , briefly, how is it applied please.

Bill


javaguy11111 wrote:

> The photoresist is ready for shipping. It is 5 feet long and was cut
> off from a 100ft roll that I purchased from ThinkTink. I have 18 rolls
> available and 4 people have contacted me. So there is plenty left, if
> anyone wants to give it a try.
>
> If ordering inside the US, the cost is $20 and shipping is by USPS.
>
> If ordering outside the US, the cost is $25 and shipping is by USPS.
> You are responsible for any customs charges
>
> I am using PayPal.
>
> Everyone who has emailed already, I have sent a reply with payment
> information. If you did send me an email, but have not heard from me
> then send me another email.
>
> Damon 
> --- In Homebrew_PCBs@yahoogroups.com, "javaguy11111"
> <javaguy11111@...> wrote:
>   
>> Just an update. I have received the resist and shipping materials. 
>>
>> I decided to use USPS instead of UPS because I have had more requests
>> for it. I will also be using paypal instead of google checkout. Again
>> more people were requesting that.  I am trying to keep things simple.
>>
>> I should be ready to start shipping by Monday and should have payment
>> information posted before the weekend is up.
>>
>> Damon
>>
>> --- In Homebrew_PCBs@yahoogroups.com, "javaguy11111"
>> <javaguy11111@> wrote:
>>     
>>> I am going to start doing some experimenting with dry film resist. I
>>> have just placed an order for a roll from Think Tink.
>>>
>>> Since it is way more than what I need, I am planning to sell the
>>> excess. I plan on selling in 5 foot lengths, which should be enough
>>> for people to experiment around with. 
>>>
>>> Figuring out time, costs, shipping materials and shipping charges I
>>> expect to charge $20. 
>>>
>>> The price includes UPS ground shipping within the continental US. If
>>> you want it sooner or live outside the continental US, contact me
>>> directly by email and we can try to make other arrangements.
>>>
>>> If you are interested, send me a private email and I will let you know
>>> when it is available. I plan on setting up payment through Google
>>> Checkout or personal check. If other payment methods are desired, let
>>> me know and I will try to accommodate you. 
>>>
>>> Taking into account shipping time, I should be able to take orders in
>>> one to two weeks.
>>>
>>> BTW, I ran this by Steve ahead of time so I would not run afoul of any
>>> spamming rules. 
>>>
>>> Damon
>>>
>>>       
>
>
>
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBs 
> Yahoo! Groups Links
>
>
>
>
>

Sorry, I forgot to mention that. It is 12 inches wide. I bought it
from think tink, so you can go to their site for information on how to
apply it. There are plenty of other sites as well. I am just getting
started with this as well. 

For initial tests I will just use a flourescent light as my UV source.
I will also need to get some washing soda(sodium carbonate) to develop
the resist and sodium hydroxide to strip off the exposed resist. 

If you go to a pool supply, do not get sodium hydrogen carbonate,
which is sodium bicarbonate. I did that on Friday, only to discover it
is not what I want. I will still keep it because it is good to have to
clean up acid spills or if I want to bake a cake. :)

After the initial tests I will probably build a UV LED exposure box
like Markus Zingg for my real board work. You can read his posts for
more information.


--- In Homebrew_PCBs@yahoogroups.com, Bill Maxwell <wrmaxwell@...> wrote:
>
> Hi Damon
> 
> 5feet long but how wide is it and , briefly, how is it applied please.
> 
> Bill
> 
> 
> javaguy11111 wrote:
> > The photoresist is ready for shipping. It is 5 feet long and was cut
> > off from a 100ft roll that I purchased from ThinkTink. I have 18 rolls
> > available and 4 people have contacted me. So there is plenty left, if
> > anyone wants to give it a try.
> >
> > If ordering inside the US, the cost is $20 and shipping is by USPS.
> >
> > If ordering outside the US, the cost is $25 and shipping is by USPS.
> > You are responsible for any customs charges
> >
> > I am using PayPal.
> >
> > Everyone who has emailed already, I have sent a reply with payment
> > information. If you did send me an email, but have not heard from me
> > then send me another email.
> >
> > Damon 
> > --- In Homebrew_PCBs@yahoogroups.com, "javaguy11111"
> > <javaguy11111@> wrote:
> >   
> >> Just an update. I have received the resist and shipping materials. 
> >>
> >> I decided to use USPS instead of UPS because I have had more requests
> >> for it. I will also be using paypal instead of google checkout. Again
> >> more people were requesting that.  I am trying to keep things simple.
> >>
> >> I should be ready to start shipping by Monday and should have payment
> >> information posted before the weekend is up.
> >>
> >> Damon
> >>
> >> --- In Homebrew_PCBs@yahoogroups.com, "javaguy11111"
> >> <javaguy11111@> wrote:
> >>     
> >>> I am going to start doing some experimenting with dry film resist. I
> >>> have just placed an order for a roll from Think Tink.
> >>>
> >>> Since it is way more than what I need, I am planning to sell the
> >>> excess. I plan on selling in 5 foot lengths, which should be enough
> >>> for people to experiment around with. 
> >>>
> >>> Figuring out time, costs, shipping materials and shipping charges I
> >>> expect to charge $20. 
> >>>
> >>> The price includes UPS ground shipping within the continental US. If
> >>> you want it sooner or live outside the continental US, contact me
> >>> directly by email and we can try to make other arrangements.
> >>>
> >>> If you are interested, send me a private email and I will let
you know
> >>> when it is available. I plan on setting up payment through Google
> >>> Checkout or personal check. If other payment methods are
desired, let
> >>> me know and I will try to accommodate you. 
> >>>
> >>> Taking into account shipping time, I should be able to take
orders in
> >>> one to two weeks.
> >>>
> >>> BTW, I ran this by Steve ahead of time so I would not run afoul
of any
> >>> spamming rules. 
> >>>
> >>> Damon
> >>>
> >>>       
> >
> >
> >
> >
> > Be sure to visit the group home and check for new Links, Files,
and Photos:

> > http://groups.yahoo.com/group/Homebrew_PCBs 
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
>

Just as a note, you don't need a UV-LED based box for the resist. I used 
it for years with an exposure box using UV tubes. The advantage of UV 
LEDs over tubes IMHO are:

- LEDs have a 20 degree (or less, see below) viewing angle whereas tubes 
radiate all around them. Alas you get more paralellized light
- UV tubes are MUCH stronger. Exposure time was here < 10 seconds. Thats 
a problem if the tubes do not start all at the same time cause then not 
all areas are evenly exposed.

I can say that since I'm using the LED box, I can do finer artwork. I 
already did sucessfully a board with 5mil traces (GigE switch, the 
signal pairs from the PHYs to the RJ45 transformers) Whereas I've not 
been able to go that fine with the previous setup. Exposure time with 
the LEDs is pretty much exactly one minute and obviousely the LEDs go on 
and off all simultanousely. Exposure time of course varries a great deal 
depending on the distance and quantity of LEDs used.

The disadvanteage of the UV-LED based aproach is that they are 
relatively costly. I used 80pcs (20x20cm squares, Kingbright L-7113UVC 
in my case). Make sure to get a datasheet and check that the peek 
radiation is around 400nm. Also look at the viewing angle and use some 
trigonometric calculations to find out how many LEDs you need at what 
distance to cover the area your unit is suposed to work with.

It apears like the general distributors (Mouser, Digikey etc.) in the 
meantime no longer carry UV LEDs due to the dangers involved with using 
them. Ledtronics does. However they want you to sign a form where you 
state to have read and understood the dangers involved and that you do 
not hold them responsible. They have a fairly interesting LED ( 
http://www.ledtronics.com/ds/L200CUV395/ article L200CUV405-8D 
<dsdc0304.pdf>) whoes viewing angle is only 8!! degrees. However, such a 
narrow beam means even more LEDs. This one is $1.15/pp, minium oder 
quantity 100. I'm tempted to try them :-)

HTH

Markus


javaguy11111 schrieb:

>
> Sorry, I forgot to mention that. It is 12 inches wide. I bought it
> from think tink, so you can go to their site for information on how to
> apply it. There are plenty of other sites as well. I am just getting
> started with this as well.
>
> For initial tests I will just use a flourescent light as my UV source.
> I will also need to get some washing soda(sodium carbonate) to develop
> the resist and sodium hydroxide to strip off the exposed resist.
>
> If you go to a pool supply, do not get sodium hydrogen carbonate,
> which is sodium bicarbonate. I did that on Friday, only to discover it
> is not what I want. I will still keep it because it is good to have to
> clean up acid spills or if I want to bake a cake. :)
>
> After the initial tests I will probably build a UV LED exposure box
> like Markus Zingg for my real board work. You can read his posts for
> more information.
>
> --- In Homebrew_PCBs@yahoogroups.com 
> <mailto:Homebrew_PCBs%40yahoogroups.com>, Bill Maxwell <wrmaxwell@...> 
> wrote:
> >
> > Hi Damon
> >
> > 5feet long but how wide is it and , briefly, how is it applied please.
> >
> > Bill
> >
> >
> > javaguy11111 wrote:
> > > The photoresist is ready for shipping. It is 5 feet long and was cut
> > > off from a 100ft roll that I purchased from ThinkTink. I have 18 rolls
> > > available and 4 people have contacted me. So there is plenty left, if
> > > anyone wants to give it a try.
> > >
> > > If ordering inside the US, the cost is $20 and shipping is by USPS.
> > >
> > > If ordering outside the US, the cost is $25 and shipping is by USPS.
> > > You are responsible for any customs charges
> > >
> > > I am using PayPal.
> > >
> > > Everyone who has emailed already, I have sent a reply with payment
> > > information. If you did send me an email, but have not heard from me
> > > then send me another email.
> > >
> > > Damon
> > > --- In Homebrew_PCBs@yahoogroups.com 
> <mailto:Homebrew_PCBs%40yahoogroups.com>, "javaguy11111"
> > > <javaguy11111@> wrote:
> > >
> > >> Just an update. I have received the resist and shipping materials.
> > >>
> > >> I decided to use USPS instead of UPS because I have had more requests
> > >> for it. I will also be using paypal instead of google checkout. Again
> > >> more people were requesting that. I am trying to keep things simple.
> > >>
> > >> I should be ready to start shipping by Monday and should have payment
> > >> information posted before the weekend is up.
> > >>
> > >> Damon
> > >>
> > >> --- In Homebrew_PCBs@yahoogroups.com 
> <mailto:Homebrew_PCBs%40yahoogroups.com>, "javaguy11111"
> > >> <javaguy11111@> wrote:
> > >>
> > >>> I am going to start doing some experimenting with dry film resist. I
> > >>> have just placed an order for a roll from Think Tink.
> > >>>
> > >>> Since it is way more than what I need, I am planning to sell the
> > >>> excess. I plan on selling in 5 foot lengths, which should be enough
> > >>> for people to experiment around with.
> > >>>
> > >>> Figuring out time, costs, shipping materials and shipping charges I
> > >>> expect to charge $20.
> > >>>
> > >>> The price includes UPS ground shipping within the continental US. If
> > >>> you want it sooner or live outside the continental US, contact me
> > >>> directly by email and we can try to make other arrangements.
> > >>>
> > >>> If you are interested, send me a private email and I will let
> you know
> > >>> when it is available. I plan on setting up payment through Google
> > >>> Checkout or personal check. If other payment methods are
> desired, let
> > >>> me know and I will try to accommodate you.
> > >>>
> > >>> Taking into account shipping time, I should be able to take
> orders in
> > >>> one to two weeks.
> > >>>
> > >>> BTW, I ran this by Steve ahead of time so I would not run afoul
> of any
> > >>> spamming rules.
> > >>>
> > >>> Damon
> > >>>
> > >>>
> > >
> > >
> > >
> > >
> > > Be sure to visit the group home and check for new Links, Files,
> and Photos:
> > > http://groups.yahoo.com/group/Homebrew_PCBs 
> <http://groups.yahoo.com/group/Homebrew_PCBs>
> > > Yahoo! Groups Links
> > >
> > >
> > >
> > >
> > >
> >
>
>

While searching around I saw the 8 degree LEDs from LEDTronics as
well. I decided to stick with the 20 degree leds.

I had done a quick calculation for the amount of undercut of 10 degree
half angle versus 8 degree half angle. This is not taking into account
 the affects that index of refraction would have.

For .0015 resist with 10 degrees gives an under cut of .26 thousands
of an inch. A 4 degree half angle gives .1 thousands of an inch undercut.

If I could find an index of refraction for the photoresist, then I
could take that into account as well. The undercut would be a little
less since the index of refraction(IOR) of resist is greater than the
IOR of air. If we were taking glass, the angle for 10 degrees would
reduce to about 7 degrees. Since I expect that the IOR for resist is
less than glass, the angle would be somewhere between 7 and 10.

After  going through all this, my conclusion is that unless I
eliminate other things that cause scattering such as glass that is not
optically flat and better masking materials, I would not reach the .26
thousands undercut of the 10 degree, much less the .1 thousands of the
4 degree.

So when I do build my UV LED box, I personally will stick with 20
degree viewing angle LEDs.


--- In Homebrew_PCBs@yahoogroups.com, Markus Zingg <homebrew-pcb@...>
wrote:
>
> Just as a note, you don't need a UV-LED based box for the resist. I
used 
> it for years with an exposure box using UV tubes. The advantage of UV 
> LEDs over tubes IMHO are:
> 
> - LEDs have a 20 degree (or less, see below) viewing angle whereas
tubes 
> radiate all around them. Alas you get more paralellized light
> - UV tubes are MUCH stronger. Exposure time was here < 10 seconds.
Thats 
> a problem if the tubes do not start all at the same time cause then not 
> all areas are evenly exposed.
> 
> I can say that since I'm using the LED box, I can do finer artwork. I 
> already did sucessfully a board with 5mil traces (GigE switch, the 
> signal pairs from the PHYs to the RJ45 transformers) Whereas I've not 
> been able to go that fine with the previous setup. Exposure time with 
> the LEDs is pretty much exactly one minute and obviousely the LEDs
go on 
> and off all simultanousely. Exposure time of course varries a great
deal 
> depending on the distance and quantity of LEDs used.
> 
> The disadvanteage of the UV-LED based aproach is that they are 
> relatively costly. I used 80pcs (20x20cm squares, Kingbright L-7113UVC 
> in my case). Make sure to get a datasheet and check that the peek 
> radiation is around 400nm. Also look at the viewing angle and use some 
> trigonometric calculations to find out how many LEDs you need at what 
> distance to cover the area your unit is suposed to work with.
> 
> It apears like the general distributors (Mouser, Digikey etc.) in the 
> meantime no longer carry UV LEDs due to the dangers involved with using 
> them. Ledtronics does. However they want you to sign a form where you 
> state to have read and understood the dangers involved and that you do 
> not hold them responsible. They have a fairly interesting LED ( 
> http://www.ledtronics.com/ds/L200CUV395/ article L200CUV405-8D 
> <dsdc0304.pdf>) whoes viewing angle is only 8!! degrees. However,
such a 

> narrow beam means even more LEDs. This one is $1.15/pp, minium oder 
> quantity 100. I'm tempted to try them :-)
> 
> HTH
> 
> Markus
>

I can never avoid making some mistake when typing something up. The 8
degree half angle should be a 4 degree half angle. 

--- In Homebrew_PCBs@yahoogroups.com, "javaguy11111"
<javaguy11111@...> wrote:

>
> I had done a quick calculation for the amount of undercut of 10 degree
> half angle versus 8 degree half angle. This is not taking into account
>  the affects that index of refraction would have.
>

I currently also use 20 degree LEDs and so far I'm very happy with the 
setup. I observed though that it seems to become harder to get those I 
have already. I.e. the Kingbright website no longer lists any UV LEDs. 
The main advantage of the 8 degree ones (which at the same time also can 
be the disadvantage) is that you can place more LEDs to get the same 
coverage. This would reduce the exposure time acordingly. I'm happy with 
the 1 minute value though, so this does not justify the effort for me at 
the moment. I agree with you that from the point of view of undercut 
it's probably not that important.

Markus

javaguy11111 schrieb:

>
> While searching around I saw the 8 degree LEDs from LEDTronics as
> well. I decided to stick with the 20 degree leds.
>
> I had done a quick calculation for the amount of undercut of 10 degree
> half angle versus 8 degree half angle. This is not taking into account
> the affects that index of refraction would have.
>
> For .0015 resist with 10 degrees gives an under cut of .26 thousands
> of an inch. A 4 degree half angle gives .1 thousands of an inch undercut.
>
> If I could find an index of refraction for the photoresist, then I
> could take that into account as well. The undercut would be a little
> less since the index of refraction(IOR) of resist is greater than the
> IOR of air. If we were taking glass, the angle for 10 degrees would
> reduce to about 7 degrees. Since I expect that the IOR for resist is
> less than glass, the angle would be somewhere between 7 and 10.
>
> After going through all this, my conclusion is that unless I
> eliminate other things that cause scattering such as glass that is not
> optically flat and better masking materials, I would not reach the .26
> thousands undercut of the 10 degree, much less the .1 thousands of the
> 4 degree.
>
> So when I do build my UV LED box, I personally will stick with 20
> degree viewing angle LEDs.
>
> --- In Homebrew_PCBs@yahoogroups.com 
> <mailto:Homebrew_PCBs%40yahoogroups.com>, Markus Zingg <homebrew-pcb@...>
> wrote:
> >
> > Just as a note, you don't need a UV-LED based box for the resist. I
> used
> > it for years with an exposure box using UV tubes. The advantage of UV
> > LEDs over tubes IMHO are:
> >
> > - LEDs have a 20 degree (or less, see below) viewing angle whereas
> tubes
> > radiate all around them. Alas you get more paralellized light
> > - UV tubes are MUCH stronger. Exposure time was here < 10 seconds.
> Thats
> > a problem if the tubes do not start all at the same time cause then not
> > all areas are evenly exposed.
> >
> > I can say that since I'm using the LED box, I can do finer artwork. I
> > already did sucessfully a board with 5mil traces (GigE switch, the
> > signal pairs from the PHYs to the RJ45 transformers) Whereas I've not
> > been able to go that fine with the previous setup. Exposure time with
> > the LEDs is pretty much exactly one minute and obviousely the LEDs
> go on
> > and off all simultanousely. Exposure time of course varries a great
> deal
> > depending on the distance and quantity of LEDs used.
> >
> > The disadvanteage of the UV-LED based aproach is that they are
> > relatively costly. I used 80pcs (20x20cm squares, Kingbright L-7113UVC
> > in my case). Make sure to get a datasheet and check that the peek
> > radiation is around 400nm. Also look at the viewing angle and use some
> > trigonometric calculations to find out how many LEDs you need at what
> > distance to cover the area your unit is suposed to work with.
> >
> > It apears like the general distributors (Mouser, Digikey etc.) in the
> > meantime no longer carry UV LEDs due to the dangers involved with using
> > them. Ledtronics does. However they want you to sign a form where you
> > state to have read and understood the dangers involved and that you do
> > not hold them responsible. They have a fairly interesting LED (
> > http://www.ledtronics.com/ds/L200CUV395/ 
> <http://www.ledtronics.com/ds/L200CUV395/> article L200CUV405-8D
> > <dsdc0304.pdf>) whoes viewing angle is only 8!! degrees. However,
> such a
> > narrow beam means even more LEDs. This one is $1.15/pp, minium oder
> > quantity 100. I'm tempted to try them :-)
> >
> > HTH
> >
> > Markus
> >
>
>

Those are interesting thoughts on LED light boxes. I had the idea some 
time ago ,but my preliminary calculations showed that my 400W mercury 
vapour light box would give lower undercut than 20 degree LEDs. I'd love 
to chuck that old heavy thing away and replace it with an 
environmentally friendly  shoe box size exposure unit.
Now you mention +-8 degree LEDs are available, then I might re-consider 
the project.
Off ebay you can get bulk +-10 degree UV LEDs really really cheap

http://cgi.ebay.com.au/SUPER-BRIGHT-UV-3000MCD-VIOLET-5MM-LED-X-100pcs_W0QQitemZ190193336488QQihZ009QQcategoryZ105796QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Doing precise calculations will only give an estimate. The only way to 
check undercutting is the test with various exposure times. You run 
minimum exposure, and then at increasing times. If the features in the 
developed photoresist don't change much between exposure times then you 
have a pretty good setup. A microscope helps a lot in diagnosing any flaws.

Adam

javaguy11111 wrote:

> 
> 
> While searching around I saw the 8 degree LEDs from LEDTronics as
> well. I decided to stick with the 20 degree leds.
> 
> I had done a quick calculation for the amount of undercut of 10 degree
> half angle versus 8 degree half angle. This is not taking into account
> the affects that index of refraction would have.
> 
> For .0015 resist with 10 degrees gives an under cut of .26 thousands
> of an inch. A 4 degree half angle gives .1 thousands of an inch undercut.
> 
> If I could find an index of refraction for the photoresist, then I
> could take that into account as well. The undercut would be a little
> less since the index of refraction(IOR) of resist is greater than the
> IOR of air. If we were taking glass, the angle for 10 degrees would
> reduce to about 7 degrees. Since I expect that the IOR for resist is
> less than glass, the angle would be somewhere between 7 and 10.
> 
> After going through all this, my conclusion is that unless I
> eliminate other things that cause scattering such as glass that is not
> optically flat and better masking materials, I would not reach the .26
> thousands undercut of the 10 degree, much less the .1 thousands of the
> 4 degree.
> 
> So when I do build my UV LED box, I personally will stick with 20
> degree viewing angle LEDs.

I just realized potential confusion about LED angle specifications. Is 
"20 degree" LED a 20 degree from centre (or +-20 degree) or the total 
conical span (+-10 degree) ?

In any case a 8 degree LED will have much higher mcd rating than 20 
degree due to the difference in light concentration.

Adam Seychell wrote:
> I just realized potential confusion about LED angle specifications. Is 
> "20 degree" LED a 20 degree from centre (or +-20 degree) or the total 
> conical span (+-10 degree) ?

Usually it means +/-10deg between 3dB points. The LEDs on ebay commonly
show the radiation polar plot.

> In any case a 8 degree LED will have much higher mcd rating than 20 
> degree due to the difference in light concentration.

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@...>
wrote:
>
> Off ebay you can get bulk +-10 degree UV LEDs really really cheap
> 

I have seen those, but I have to wonder why they can sell 100 for 6
dollars or six cents apiece, while a distributor sells them for a
dollar apiece. I know part of it is markup, but such a drastic
difference in price makes me a little suspicious. If it sounds too
good to be true...