Homebrew PCBs

I was thinking of making a new UV exposure box.   Got rid  of my old one
years ago when I was in a down sizing mood.

Been looking for UV bulb sources.   I think my old unit used  F15T8BL
tubes but not sure of the number.

Looking on ebay I see a lot of low cost nail curing lamps and nail
curing units.  One add has  4 9W  U shaped CF  style UV lamps for $8.49 
(item # 310199835791).  Then you can get an entire nail unit for about
$35 and get 4 bulbs, balasts and lamp sockets.   I think 4 bulbs would
make a nice  5 x7  or 6x8  exposure unit.

Has anyone ever tried these bulbs or one of the units on PCB resist?

I was thinking of using an array of UV led's but this may be easier and
provide more power.

Craig

After reading your post yesterday, I decided that building an exposure box
for 2 sided boards is a huge step toward getting 2 sided boards out of my
kitchen with reliable results.  I ordered a 15w blacklight from:

http://www.musiciansfriend.com/

It is the entire fixture, not just the lamp.  $13.  They wanted $8 to ship 4
of these to Michigan.  That is hard to beat.

Now, I choose not to use 2 on each side, but 1.  I have been using a single
bulb 12" from a 6 x 9 board, with a 24 min exposure.  So I am going to start
with 1 per side.  If I need to up the number, I will.

On Sat, Feb 13, 2010 at 7:18 PM, designer_craig <cs6061@...> wrote:

>
>
>
> I was thinking of making a new UV exposure box. Got rid of my old one
> years ago when I was in a down sizing mood.
>
> Been looking for UV bulb sources. I think my old unit used F15T8BL
> tubes but not sure of the number.
>
> Looking on ebay I see a lot of low cost nail curing lamps and nail
> curing units. One add has 4 9W U shaped CF style UV lamps for $8.49
> (item # 310199835791). Then you can get an entire nail unit for about
> $35 and get 4 bulbs, balasts and lamp sockets. I think 4 bulbs would
> make a nice 5 x7 or 6x8 exposure unit.
>
> Has anyone ever tried these bulbs or one of the units on PCB resist?
>
> I was thinking of using an array of UV led's but this may be easier and
> provide more power.
>
> Craig
>
>  
>



-- 
Thank you,

Barry


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

Barry Demers <sdad@...> writes:
> I have been using a single bulb 12" from a 6 x 9 board, with a 24
> min exposure.

A single 15 watt bulb?

I've been pondering upgrading to two-sided UV exposure, but my LED box
exposes in only 5 minutes.

Can you reduce the exposure time by using mirrors to reflect more of
the UV light to the board?  I.e. something behind the bulbs, or the
sides of the box.  Or is it just going to mess up the quality of the
exposure?

Absolutely, a single F15T8-BL. One.

OK, I've been using a positive method, pre-sensitized board.  The amount of
time that it takes to cure the resist is a square function of distance
source to object.  Further away, larger the area that can be cured.  But,
the time it takes is increased.  Don't like the time, move closer, but do a
smaller board. In my opinion, however, its like fine adjusting with the
course control.  With a longer exposure time, the lower the probability of
over exposure.  A 10 turn pot instead of a single turn.  Now, if you can
dial in that closely then go for it.  I have found very consistent results
from batch to batch of different coatings.  As the output of the bulb
decreases, as it does with time, I need to do very little, to no
compensating.  By the way, this is not in any enclosure, I set the fixture
on the counter, positon the target on a couple of plastic drink containers,
set the timer, turn on the lamp and go do something else for a couple of
minutes.  There isn't any reflective surface added, black light shining on
all the cookie crumbs on the counter.
The 2 sided fixture that I envision may well end up in a box, but if an
aluminum frame to hold the 2 fixtures and the glass plates between them can
be fashioned sturdy enough, that's where I'll go first.  If I need more
light power then I can put in reflection and if that still isn't good enough
then an additional pair of bulbs, but tonight I'm thinking all of that isn't
needed.
Based on that premise, though I priced 4 fixtures from the source, I only
purchased one.  Came in at $18 with the shipping.  I'll spend the dif on
more cookies.

On Sat, Feb 13, 2010 at 11:08 PM, DJ Delorie <dj@...> wrote:

>
>
>
> Barry Demers <sdad@... <sdad%40chipchristy.com>> writes:
> > I have been using a single bulb 12" from a 6 x 9 board, with a 24
> > min exposure.
>
> A single 15 watt bulb?
>
> I've been pondering upgrading to two-sided UV exposure, but my LED box
> exposes in only 5 minutes.
>
> Can you reduce the exposure time by using mirrors to reflect more of
> the UV light to the board? I.e. something behind the bulbs, or the
> sides of the box. Or is it just going to mess up the quality of the
> exposure?
>  
>



-- 
Thank you,

Barry


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

Barry Demers <sdad@...> writes:
> Now, if you can dial in that closely then go for it.

Sure, just pick up a transmission step gauge and a timer.  I've got my
UV box down to exactly where the film says the exposure should be, and
I know how far over or under I can go and still get good results.

In my case, I have 8 steps of working range, or a 16x time difference
between "just enough" and "almost too much", which means a window from
1.4 minutes to 22 minutes (I use 5.5 minutes).

What I'd like is a box that can do both sides in less time, which
means *more* UV.  If you need 24 minutes with a 15 watt bulb, then I'd
need four 30 watt bulbs - per side - to improve on my exposure times.

Since you can measure your exposure with accuracy, reduce your distance and
increase your time.  For example, 6" distance should equate to 6 minutes.
(half the distance, 1/4 the time).  One thing that I haven't dialed in yet.
The bulbs have a lifetime, they wear out.  Longer they are on for each job,
the fewer the jobs before replacement.

On Sun, Feb 14, 2010 at 2:02 AM, DJ Delorie <dj@...> wrote:

>
>
>
> Barry Demers <sdad@chipchristy.com <sdad%40chipchristy.com>> writes:
> > Now, if you can dial in that closely then go for it.
>
> Sure, just pick up a transmission step gauge and a timer. I've got my
> UV box down to exactly where the film says the exposure should be, and
> I know how far over or under I can go and still get good results.
>
> In my case, I have 8 steps of working range, or a 16x time difference
> between "just enough" and "almost too much", which means a window from
> 1.4 minutes to 22 minutes (I use 5.5 minutes).
>
> What I'd like is a box that can do both sides in less time, which
> means *more* UV. If you need 24 minutes with a 15 watt bulb, then I'd
> need four 30 watt bulbs - per side - to improve on my exposure times.
>  
>



-- 
Thank you,

Barry


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

On 14/02/2010 14:49, Barry Demers wrote:
> Since you can measure your exposure with accuracy, reduce your distance and
> increase your time.  For example, 6" distance should equate to 6 minutes.
> (half the distance, 1/4 the time).  One thing that I haven't dialed in yet.
> The bulbs have a lifetime, they wear out.  Longer they are on for each job,
> the fewer the jobs before replacement.

Don't forget that you lose collimation with shorter distances.

Leon
-- 
Leon Heller
G1HSM

> Barry Demers <sdad@...> writes:
> > I have been using a single bulb 12" from a 6 x 9 board, with a 24
> > min exposure.
> 
> A single 15 watt bulb?
> 
> I've been pondering upgrading to two-sided UV exposure, but my LED box
> exposes in only 5 minutes.
> 
> Can you reduce the exposure time by using mirrors to reflect more of
> the UV light to the board?  I.e. something behind the bulbs, or the
> sides of the box.  Or is it just going to mess up the quality of the
> exposure?
>

I have 4 15 Watt 18" lamps and do upto 8" x 12" boards at about 6" from the lamps.   Use to expose about 6 mins. but now have found that 10 mins is better as long as you have a really good transparency.  

Now that I am using Dip Trace instead of the old Ivex Winboard I get a lot better printouts onto the Transparencies.  Seem to get a lot more ink down printing from Dip Trace than I did from Ivex Winboard, even though I would set the amount of ink to max in the printer settings.  With Ivex Winboard I had to always double up or try to print it twice which did not always work.

Ben

Barry,
I have also been thinking about a UV led box. Five minutes seems ok to me. Can you describe your LED array? What sort of spacing do you have on the LED array and distance do you run between the board and the LEDs?

Craig

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:

>
> 
> Barry Demers <sdad@...> writes:
> > I have been using a single bulb 12" from a 6 x 9 board, with a 24
> > min exposure.
> 
> A single 15 watt bulb?
> 
> I've been pondering upgrading to two-sided UV exposure, but my LED box
> exposes in only 5 minutes.
> 
> Can you reduce the exposure time by using mirrors to reflect more of
> the UV light to the board?  I.e. something behind the bulbs, or the
> sides of the box.  Or is it just going to mess up the quality of the
> exposure?
>

Yes, you don't want to get too close.  I haven't taken the time to do any
calcs on this stuff yet.  I simply have a system that works and will improve
on it as time and need allows.  Be interesting to run the math, though.  A
parabolic reflector seems like a fun exercise.

On Sun, Feb 14, 2010 at 10:00 AM, Leon Heller <leon355@...>wrote:

>
>
> On 14/02/2010 14:49, Barry Demers wrote:
> > Since you can measure your exposure with accuracy, reduce your distance
> and
> > increase your time. For example, 6" distance should equate to 6 minutes.
> > (half the distance, 1/4 the time). One thing that I haven't dialed in
> yet.
> > The bulbs have a lifetime, they wear out. Longer they are on for each
> job,
> > the fewer the jobs before replacement.
>
> Don't forget that you lose collimation with shorter distances.
>
> Leon
> --
> Leon Heller
> G1HSM
>  
>



-- 
Thank you,

Barry


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

At 01:30 PM 2/14/2010, you wrote:
>  A
>parabolic reflector seems like a fun exercise.

lighting centers in places like Home Depot have a chrome-reflective 
plastic grid that is used to 'sorta' collimate florescent bulbs. i've 
seen these same units in professional screen printing exposure units 
that have UV tubes. the grid goes between the bulbs and the glass 
exposure surface and are angled to reflect light back up in a 
straighter line. i do think they are a good addition to an exposure unit.

William Alford  

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

Interesting.  I'll take a look on my next trip to Manard's

On Sun, Feb 14, 2010 at 2:55 PM, William <walford@...> wrote:

>
>
> At 01:30 PM 2/14/2010, you wrote:
> > A
> >parabolic reflector seems like a fun exercise.
>
> lighting centers in places like Home Depot have a chrome-reflective
> plastic grid that is used to 'sorta' collimate florescent bulbs. i've
> seen these same units in professional screen printing exposure units
> that have UV tubes. the grid goes between the bulbs and the glass
> exposure surface and are angled to reflect light back up in a
> straighter line. i do think they are a good addition to an exposure unit.
>
> William Alford
>
> [Non-text portions of this message have been removed]
>
>  
>



-- 
Thank you,

Barry


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

"Ben L" <bhleavi@...> writes:
> Seem to get a lot more ink down printing from Dip Trace than I did
> from Ivex Winboard,

If you have an epson printer that can do 2880 dpi, I have a program
that prints PBM files with 100% ink coverage - so much ink you need
specially coated films to keep it from smearing.

"designer_craig" <cs6061@...> writes:
> Can you describe your LED array? What sort of spacing do you have on
> the LED array and distance do you run between the board and the
> LEDs?

I use a triangular grid, spacing about 1", about 5" from the board.
Total 99 LEDs, in 11 strings of 9 on a 37 volt power supply:

        http://www.delorie.com/pcb/uvled/

These are low-angle (8-10 degrees) and the spacings are designed to
give approximately uniform coverage, assuming I can aim the things
accurately.  Been thinking about redoing it with a PCB instead of a
chunk of plywood so I can solder them in securely, and at the same
time increase the LED density and add the second side.

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
> 
> "Ben L" <bhleavi@...> writes:
> > Seem to get a lot more ink down printing from Dip Trace than I did
> > from Ivex Winboard,
> 
> If you have an epson printer that can do 2880 dpi, I have a program
> that prints PBM files with 100% ink coverage - so much ink you need
> specially coated films to keep it from smearing.
>

Don't have a Epson, have HP's  cp 1700 and Officejet 7410.  I am fine with the print I get from Dip Trace to them, and don't use the Ivex anymore.  Like the HP Transparencies the best, but have used the Office Depot brand with good results.

Ben