Homebrew PCBs

I just made my first PCB. I did two of them, with different expossure
times.

Two 6W blacklight tubes, 7 cm away from the PCB, trough a 0.5mm glass.

First, I did 5 minutes exposure. Then, 2 minutes 30 seconds in
metasilicate developer. It came out quite well. All shiny. But it
seems that when I took it out of the developer, and tried to clean
with a soft dumped paper, some of the etch-resistant tended to difuse.
So I stoped, then washed it with lots of fresh water, and then dry it
with some toilet paper.

It came out well, but some borders not perfectly defined. So, I tried
more expossure.
This time 7 minutes, 30 seconds, and 2 minutes in metasilicate.
This one came out better defined, but tracks were thiner, and a little
section of a thin track dissapear.

These are my conclusions...
the second board was overexpossed. I should try near 5 minutes, and
near 2 minutes in metasilicate.

But I find hard to know when developing is over, because I see a light
gray layer over the bare copper areas, and I don't know if it is
finished or not. And  don't know if I can safely clean it with a soft
paper, or this way I can take it off!

Any help about this to get better next time??
Thank you!!

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

From: "patroclus04" <patroclus04@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Saturday, April 08, 2006 10:45 PM
Subject: [Homebrew_PCBs] My first PCB (photo-resist).


>I just made my first PCB. I did two of them, with different expossure
> times.
>
> Two 6W blacklight tubes, 7 cm away from the PCB, trough a 0.5mm glass.
>
> First, I did 5 minutes exposure. Then, 2 minutes 30 seconds in
> metasilicate developer. It came out quite well. All shiny. But it
> seems that when I took it out of the developer, and tried to clean
> with a soft dumped paper, some of the etch-resistant tended to difuse.
> So I stoped, then washed it with lots of fresh water, and then dry it
> with some toilet paper.
>
> It came out well, but some borders not perfectly defined. So, I tried
> more expossure.
> This time 7 minutes, 30 seconds, and 2 minutes in metasilicate.
> This one came out better defined, but tracks were thiner, and a little
> section of a thin track dissapear.
>
> These are my conclusions...
> the second board was overexpossed. I should try near 5 minutes, and
> near 2 minutes in metasilicate.
>
> But I find hard to know when developing is over, because I see a light
> gray layer over the bare copper areas, and I don't know if it is
> finished or not. And  don't know if I can safely clean it with a soft
> paper, or this way I can take it off!
>
> Any help about this to get better next time??

Your artwork might not be dense enough. How are you making your 
transparencies?

Leon 

---
[This E-mail has been scanned for viruses but it is your responsibility 
to maintain up to date anti virus software on the device that you are
currently using to read this email. ]

0.5mm glass????

patroclus04 <patroclus04@...> wrote:  I just made my first PCB. I did two of them, with different expossure
times.

Two 6W blacklight tubes, 7 cm away from the PCB, trough a 0.5mm glass.


__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com 

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

>But it seems that when I took it out of the developer, and tried to 
>clean with a soft dumped paper, some of the etch-resistant tended 
>to difuse.

Use a foam brush to **lightly** wipe the board while it's developing 
in the solution. Just use the weight of the brush instead of 
pressing down with it on the board while wiping. Turn the board over 
to wipe the other side.

Wiping not only speeds up the process but it also allows you to see 
the exposed copper areas more clearly. It's done when all exposed 
copper areas show no traces whatsoever of etch resist. Tracks should 
be clearly defined without a "haze" of etch resist between them. 

Remove the board from the solution when done and hold it under 
running water, do both sides. Use compressed air to dry then 
inspect. You can also pat the board with a paper towel instead of 
using compressed air.

Typically, the above takes 3 to 5 minutes provided the boards are 
relatively new and they weren't underexposed. Here's a picture of a 
foam brush;

http://www.circuitspecialists.com/products/full/3758.jpg


--- In Homebrew_PCBs@yahoogroups.com, "patroclus04" 
<patroclus04@...> wrote:
>

Sorry, I meant 5mm glass.
I made my transparency with inkject transparency paper, using a inkjet
printer. It came out pretty well, and as I sais, I made two PCBs out
of it, and one of then, more expossed, came out perfectly defined. But
I think it is overexpossed as all tracks were thiner, and one little
part dissapear...
So, I suppose I should try less expossure time?

The non-defined borders could be due to ?
- trying to clean the board while developing (to see if copper was
completely visible)??
- little expossure time??

So, if I try to clean SOFTLY the PCB while developing, I will not ruin
it ?? It seemed to me that last time my borders got bad definition and
I was thiking of it being caused by trying to clean the PCB while
developing.. maybe it's just my impression

On Tue, 11 Apr 2006 10:34:45 +0200, patroclus04 <patroclus04@...>  
wrote:

>
> So, if I try to clean SOFTLY the PCB while developing, I will not ruin
>
> it ?? It seemed to me that last time my borders got bad definition and
>
> I was thiking of it being caused by trying to clean the PCB while
>
> developing.. maybe it's just my impression
>
>


i don't do photo any more, but to me it seemed pretty sturdy and i used to  
rub it.
It seemed more like the exposed areas get soft and dissolved than the  
masked areas getting hard during developing, so they were not damaged.

ST

> So, if I try to clean SOFTLY the PCB while developing, I will not ruin
> it ?? 

Which positive boards are you using or are you using a spray for resist?

--- In Homebrew_PCBs@yahoogroups.com, "patroclus04" <patroclus04@...> 
wrote:
>

I'm using a brand of positive board that surely does not exist in the
US. I live in Spain. It is green.

Yesterday I did some tests, and photoresist SURELY goes out it I try
to clean it. I need to wash it with fresh water then let it dry a bit.
Else, all I touch fades away... I tried for several exposure times. It
seems that more time, more resist... but not sure. Not very clear
evidence...
I really don't know what to think or what to do!

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

From: "patroclus04" <patroclus04@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, April 12, 2006 3:37 PM
Subject: [Homebrew_PCBs] Re: My first PCB (photo-resist).


> I'm using a brand of positive board that surely does not exist in the
> US. I live in Spain. It is green.
> 
> Yesterday I did some tests, and photoresist SURELY goes out it I try
> to clean it. I need to wash it with fresh water then let it dry a bit.
> Else, all I touch fades away... I tried for several exposure times. It
> seems that more time, more resist... but not sure. Not very clear
> evidence...
> I really don't know what to think or what to do!

What brand of board is it? Is there a data sheet?

Leon

>Yesterday I did some tests, and photoresist SURELY goes out it I try
>to clean it. 

The exposed resist should easily dissolve away in the solution leaving 
bare copper provided the exposure time was sufficient. No cleaning as 
such should be necessary. Agitation or wiping/brushing speeds up the 
process and allows for quicker and even development. It also disperses 
any green concentration in the solution that may hide the bare copper.

>I need to wash it with fresh water then let it dry a bit.
>Else, all I touch fades away

The unexposed resist should be much more durable than that. You should 
be able to skip the drying step and go straight into the etchant if 
inspection isn't required. Look into the exposure time, quality of the 
boards, concentration of the developer solution etc.. Try and contact 
someone who has worked with those particular boards. 

--- In Homebrew_PCBs@yahoogroups.com, "patroclus04" <patroclus04@...> 
wrote:
>