Homebrew PCBs

I'm attempting to debunk the following two myths at the same time;

1. A collimated light source is needed for .005" to .01" rules when 
photoetching.

2. All vertical bubble etching system cause uneven etching. Board size 
is 6"X4" hung vertically as shown. 

http://www.pbase.com/eldata/6_6_rules

derekhawkins wrote:
> I'm attempting to debunk the following two myths at the same time;
> 
> 1. A collimated light source is needed for .005" to .01" rules when 
> photoetching.
> 
> 2. All vertical bubble etching system cause uneven etching. Board size 
> is 6"X4" hung vertically as shown. 
> 
> http://www.pbase.com/eldata/6_6_rules

I've used a vertical bubble etcher for a few years and have no uneven etching
at all. These myths are in the same category such as "ferric chloride is slow",
"PRP doesn't work", etc.

--- In Homebrew_PCBs@yahoogroups.com, Russell Shaw <rjshaw@...> wrote:
>
> derekhawkins wrote:
> > I'm attempting to debunk the following two myths at the same time;
> > 
> > 1. A collimated light source is needed for .005" to .01" rules 
> when 
> > photoetching.
> > 
> > 2. All vertical bubble etching system cause uneven etching. Board 
> size 
> > is 6"X4" hung vertically as shown. 
> > 
> > http://www.pbase.com/eldata/6_6_rules
> 
> I've used a vertical bubble etcher for a few years and have no 
> uneven etching
> at all. These myths are in the same category such as "ferric 
> chloride is slow",
> "PRP doesn't work", etc.

I've used vertical bubble etchers, both homemade, and commercial (but 
cheaper models), and both of them caused terribly uneven etching. I 
suspect that 1) the strength of the air pump and 2) the size and 
placement of the bubbles have a lot to do with this. So if you have a 
vertical bubble etcher that works perfectly, post the name and model 
number of it. I don't remember where I got the commercial one that I'd 
bought, I think it was Electronics Express but I could be wrong. I 
threw it away about two years ago. It etched much, much faster where 
the bubbles hit the metal, and one edge would etch faster than the 
other. So I don't think this is entirely a myth, I think it has to do 
with the quality of the bubble etcher you buy.

fenrir_co wrote:

> I've used vertical bubble etchers, both homemade, and commercial (but 
> cheaper models), and both of them caused terribly uneven etching. I 
> suspect that 1) the strength of the air pump and 2) the size and 
> placement of the bubbles have a lot to do with this. So if you have a 
> vertical bubble etcher that works perfectly, post the name and model 
> number of it. I don't remember where I got the commercial one that I'd 
> bought, I think it was Electronics Express but I could be wrong. I 
> threw it away about two years ago. It etched much, much faster where 
> the bubbles hit the metal, and one edge would etch faster than the 
> other. So I don't think this is entirely a myth, I think it has to do 
> with the quality of the bubble etcher you buy.

If you want the ultimate in etching, you need to collimate that 
process. Bubble or spray etching is a far less collimated process than 
exposing a mask to an uncollimated source.

If you float the board, copper side down on the surface of ferric 
chloride etchant, the etching process proceeds almost straight up. 
The loaded etchant is more dense than fresh, so a convection cell 
forms that provides fresh etchant to the center of the slot (or hole) 
between two edges of resist, and the loaded etchant slides down along 
both sides, preventing undercutting, till the copper is etches all the 
way through.  I have used this technique to etch holes with a diameter 
equal to the copper thickness, and slots narrower than the copper 
thickness.  The sides of the remaining copper traces are smooth and 
almost perpendicular to the board surface.

The skill that must be mastered to make this work is to be able to 
slide the board in, one edge first, so that no bubbles are trapped 
under the board.  I usually slide the board in, to get it wet, raise 
it up, to see if all the exposed copper has been wet, and slide it 
back in.  I usually just use a plate of etchant, selected so that the 
board is supported by the 4 corners just into the surface of the 
puddle.  After that, resist (as much as possible) the urge to peak or 
otherwise agitate the etchant, because that will ramp up undercutting 
until the convection cells reform.  This works especially well with 
single sided boards, where you can see through the board material when 
the etching is about finished.

Spray, bubble or other agitated methods are faster than convection 
etching, but, once you compare the precision and accuracy of the 
results, you may decide that the extra time (to make and drink a cup 
of tea), is well worth it, unless you are on a production schedule.  I 
also like the absence of mist that corrodes everything metallic, nearby.

fenrir_co wrote:
> --- In Homebrew_PCBs@yahoogroups.com, Russell Shaw <rjshaw@...> wrote:
> 
>>derekhawkins wrote:
>>
>>>I'm attempting to debunk the following two myths at the same time;
>>>
>>>1. A collimated light source is needed for .005" to .01" rules 
>>when photoetching.
>>>
>>>2. All vertical bubble etching system cause uneven etching. Board 
>>size is 6"X4" hung vertically as shown. 
>>>
>>>http://www.pbase.com/eldata/6_6_rules
>>
>>I've used a vertical bubble etcher for a few years and have no 
>>uneven etching at all. These myths are in the same category such as "ferric 
>>chloride is slow", "PRP doesn't work", etc.
> 
> 
> I've used vertical bubble etchers, both homemade, and commercial (but 
> cheaper models), and both of them caused terribly uneven etching. I 
> suspect that 1) the strength of the air pump and 2) the size and 
> placement of the bubbles have a lot to do with this. So if you have a 
> vertical bubble etcher that works perfectly, post the name and model 
> number of it. I don't remember where I got the commercial one that I'd 
> bought, I think it was Electronics Express but I could be wrong. I 
> threw it away about two years ago. It etched much, much faster where 
> the bubbles hit the metal, and one edge would etch faster than the 
> other. So I don't think this is entirely a myth, I think it has to do 
> with the quality of the bubble etcher you buy.

Look at the blue etcher tank on http://www.kalex.net.au

When the bubbles rise between the pcb and the tank side, a vacuum forms,
pulling the pcb against it. Then the reverse happens on the other side of
the pcb. This causes the hanging pcb to pendulum back and forth. The bubble
stream is quite weak, but the etching still happens evenly over the whole pcb.
I use ferric chloride 1:1 with water (use hot water for bonus speed if you're
mixing a new batch), and 1/4 - 1/2 cup of hydrochloric acid every few months.
I've been using the same etchant in the tank for the last year. Double-sided
35um pcb etches in 6mins at room temp with fresh etchant. More typically, it's
8-12mins, then put the pcb into a tray and do a small amount of brushing to etch
the last few stubborn bits.

>If you want the ultimate in etching, you need to collimate that
>process.

Diminshed returns in a homebrew scenario. I have tried "float 
etching" with Ferric Chloride (FC) and yes it's possible that it 
more faithfully reproduces the original than normal etching. FC in 
general seems to do a better job than the Persulphates (PER) in 
terms of fidelity but that's just another reason why I prefer them 
over FC. Below are extreme (the best my macro lens could do) 
closeups of two of the 6/6 images that demonstrate that what you see 
may not be what you want to get. The edges from inkjet printers are 
far from smooth and I purposely overexpose inkjet artwork and etch 
with PER in order to even things out. The etched board may have lost 
a fraction of a thou along the way but the edges are much smoother 
when compared to the original artwork. Lens to subject distance was 
the same in both cases.

Closeup of original artwork;
http://www.pbase.com/eldata/image/62430331

Closeup of same area of etched board;
http://www.pbase.com/eldata/image/62430370

--- In Homebrew_PCBs@yahoogroups.com, John Popelish <jpopelish@...> 
wrote:
>

>So if you have a vertical bubble etcher that works perfectly, post 
>the name and model number of it.

Kinsten ET-10 is what I have and it works well. The one in the shot 
has seen active duty for around 5 years and worked so well that I 
bought two more around three years ago. Circuit Specialists used to 
sell them for $29.00 but now sells the ET-20 for $44.00. While the 
latter is bigger it may not work as well for that very reason. Also, 
the ET-20 requires a minimum of 2 litres of etchant while the ET-10 
only requires a minimum of 1 litre so I'm led to believe it's using 
the same heater. The heater is too high in the tank IMO, compare the 
two images;

http://www.web-tronics.com/lowcosetsysw.html

http://www.pbase.com/eldata/image/62352753/original


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

> derekhawkins wrote:
>
> I'm attempting to debunk the following two
> myths at the same time;
> 
> 1. A collimated light source is needed for
> .005" to .01" rules when photoetching.
> 
> 2. All vertical bubble etching system cause
> uneven etching.
>
> Board size is 6"X4" hung vertically as shown. 
> 
> http://www.pbase.com/eldata/6_6_rules

Nice etching.

I agree collimation is not needed and bubble
etching works well.  I currently use both an
uncollimated light source and a kinsten
bubble etcher.

My main problem I have with getting to 6/6 is
my phototool.

Printing on my personal laser I can do a 6/6
board FILLED with 6/6 like you have shown but
if I try doing a a board where 1/2 the board
is 6/6 and the other half has large areas of
copper I get problems.  During the develop
I either need to leave it too long for the
large copper areas to be pitted or I take it
out too soon and I get shorts in the 6/6 area.

I just use a little laserjet 4xxx myself.  It
just can't seem to do big black areas well.

The big laserprinter I borrow works well for
large black areas - but it is a half hour ride
to get to use.

How do your boards go with 6/6 AND wide tracks
mixed on a single board ?


I am going to build a think and tinker style
collimated box - but I don't think it is
going to make a noticeable improvement.

Being setup for macro shots I decided to take some possibly useful 
reference shots;

Unetched copper surface at same magnification as previous closeups;

http://www.pbase.com/eldata/image/62468091

A cheap commercial PCB;

http://www.pbase.com/eldata/image/62473838

Closeup of above;

http://www.pbase.com/eldata/image/62473839

Better commercial PCB;

http://www.pbase.com/eldata/image/62473840

Closeup of above;

http://www.pbase.com/eldata/image/62473841


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

>Nice etching.

Thanks.

> Printing on my personal laser I can do a 6/6
> board FILLED with 6/6 like you have shown but
> if I try doing a a board where 1/2 the board
> is 6/6 and the other half has large areas of
> copper I get problems.  During the develop
> I either need to leave it too long for the
> large copper areas to be pitted or I take it
> out too soon and I get shorts in the 6/6 area.

Assuming you're already using the highest toner density setting, you 
could try the solvent fumigation trick or one of those sprays like 
Laser Buddy. Most of us just switch to Inkjet to solve that problem.

> The big laserprinter I borrow works well for
> large black areas - but it is a half hour ride
> to get to use.

Which model printer is this?

> How do your boards go with 6/6 AND wide tracks
> mixed on a single board ?

Not a problem, Inkjet artwork is so opaque you can severly 
overexpose in terms of time and still not have pitting or undercut 
issues.

> I am going to build a think and tinker style
> collimated box - but I don't think it is
> going to make a noticeable improvement.

Just add a collimation grid to an existing lightbox, waste of time 
though, it's not going to solve your opacity problem nor is it going 
to address any issues you may have in the .005" - .010" range IMO.

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

> Derek wrote: 
> <snip>
> Assuming you're already using the
> highest toner density setting, you 
> could try the solvent fumigation
> trick or one of those sprays like 
> Laser Buddy. Most of us just switch
> to Inkjet to solve that problem.

Never heard of fumigation trick or laser
buddy - I will google them both now.

I have an endless supply of inkjets and
ink for them  (I have a friend that
imports and sells bottled ink systems
for epson and canon printers).  I
always liked the sharp edge of the
laser better.  Guess I can give an
inky a try though.

>> The big laserprinter I borrow works
>> well for large black areas - but it
>> is a half hour ride to get to use.
> 
> Which model printer is this?

Fuji Xerox one which I think uses the
technology they aquired with tektronics.

It's a big true 1200dpi colour laser that
I think costs as much as a small car.

It's 4 and a bit foot tall, 4 foot wide
and 3 foot deep.  Makes my little LJ4000
look like a pocket sized portable.

Does a very very nice job on vellum.
Incredibly black and no pin holes in
sight.

> <snip>
>> I am going to build a think and tinker style
>> collimated box - but I don't think it is
>> going to make a noticeable improvement.
> 
> Just add a collimation grid to an existing
> lightbox, waste of time though, it's not
> going to solve your opacity problem nor is
> it going to address any issues you may have
> in the .005" - .010" range IMO.

My current light box is a breifcase style
kinsten one.  The lamps are too close in the
breifcase style boxes and I get uneven
exposure.  SO I want to build a better one
anyways.  No harm in putting in the
collimating grid while I am building it I
think :D

Hopefully the laser plotter will solve the
opacity problem.  And I think all my sub 8
thou problems are photo tool related.

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

From: "Andrew" <andrewm1973@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Monday, June 26, 2006 4:58 AM
Subject: [Homebrew_PCBs] Re: 6/6 Rules (.006" lines and .006" spacing)


>> Derek wrote: 
>> <snip>
>> Assuming you're already using the
>> highest toner density setting, you 
>> could try the solvent fumigation
>> trick or one of those sprays like 
>> Laser Buddy. Most of us just switch
>> to Inkjet to solve that problem.
> 
> Never heard of fumigation trick or laser
> buddy - I will google them both now.

Using solvent fumes to make the image denser.

Leon

> John Popelish wrote:
> <snip>
> If you float the board, copper side
> down on the surface of ferric chloride
> etchant, the etching process proceeds
> almost straight up.  The loaded
> etchant is more dense than fresh, so a
> convection cell forms that provides
> fresh etchant to the center of the
> slot (or hole) between two edges of
> resist, and the loaded etchant slides
> down along both sides, preventing
> undercutting, till the copper is
> etches all the way through.  I have
> used this technique to etch holes with
> a diameter equal to the copper
> thickness, and slots narrower than the
> copper thickness.  The sides of the
> remaining copper traces are smooth and 
> almost perpendicular to the board
> surface.
> <snip>

I will give this a try with some CuCl on
the weekend and see if it works with that
and what I think of it.

Andrew wrote:
>>John Popelish wrote:
>><snip>
>>If you float the board, copper side
>>down on the surface of ferric chloride
>>etchant, the etching process proceeds
>>almost straight up.
(snip)

> I will give this a try with some CuCl on
> the weekend and see if it works with that
> and what I think of it.

I await your report.  I have used the method only with ferric chloride.