Homebrew_PCBs

Hi all,

I am experiencing a problem when developing a UV-sensitive PCB type AA16, made by CIF, available from RS Components as stock number 159-6057.

I mentioned this in my last post to this group, and have now made an exposure test from 1-10mins just to see more what's going on.

My problem is that it is difficult to remove all of the exposed etch resist layer reliably, at almost every exposure level. I'm using Sodium Metasilicate universal developer, RS stock number 690-849, in a hand-agitated plastic developing tray.

After removing the board's protective film, I notice there is a pattern like wood grain which is visible in the unexposed etch resist layer, which runs across the width of the board.

This pattern remains visible throughout the development, even after 10 minutes of constant agitation at 20'C.

I agitate the board as much as possible while developing it, then rinse the board thoroughly.

Here's a flatbed scan of the developed, but un-etched, boards:

https://www.sendspace.com/file/lr6uay (sorry, scan cropped the bottom board a bit)

And after etching:
https://www.sendspace.com/file/6xi3gw

 

I wonder whether there is a compatibility issue between the etch resist layer and my choice of developer? Do manufacturers tend to specify a preferred type of developer that works best with their boards?

When I etch the developed board, the remaining grain pattern creates lots of fine hair-like copper traces which interfere with the design.

So, I would be very grateful for any and all suggestions, comments and questions.

Kind regards,
Matt

On 29/08/2014 12:25, mattmoose1969@... [Homebrew_PCBs] wrote:

> Hi all,
>
> I am experiencing a problem when developing a UV-sensitive PCB type
> AA16, made by CIF, available from RS Components as stock number 159-6057.
>
> I mentioned this in my last post to this group, and have now made an
> exposure test from 1-10mins just to see more what's going on.
>
> My problem is that it is difficult to remove all of the exposed etch
> resist layer reliably, at almost every exposure level. I'm using Sodium
> Metasilicate universal developer, RS stock number 690-849, in a
> hand-agitated plastic developing tray.

How are you making the transparency? Does it have enough contrast?

Leon
--
Leon Heller
G1HSM

Hi Leon,

I'm laser printing the artwork onto 90gsm tracing paper, as recommended by someone who has done a lot more of this than I have.

Thanks,
Matt

>>>>

On 29/08/2014 12:25, mattmoose1969@... [Homebrew_PCBs] wrote:

> Hi all,
>
> I am experiencing a problem when developing a UV-sensitive PCB type
> AA16, made by CIF, available from RS Components as stock number 159-6057.

I should have added - how hot is the solution?

Leon
--
Leon Heller
G1HSM

On 29/08/2014 12:49, mattmoose1969@... [Homebrew_PCBs] wrote:

> Hi Leon,
>
> I'm laser printing the artwork onto 90gsm tracing paper, as recommended
> by someone who has done a lot more of this than I have.

It might not have enough contrast, try using LaserStar film. I think
it's available from RS, or you can get it from Mega Electronics (UK).

Leon
--
Leon Heller
G1HSM

Hi, sorry you downloaded an .exe somehow, the Sendspace link usually just works. Thanks for copying the image files elsewhere, very kind.

The paper is 90gsm as I said, and no it's not crinkling. The crinkly pattern is absolutely a function of how the etch resist is deposited. The issure really seems to be etch resist's own non-uniformity. I tried transparent film before, and the same effect results. The patterning does not tie up with either type of transparent material that I've used.

Hi Leon,

I'm using the developer at around 21'C, and I believe that its working temperature needs to be 20-25'C.

Thanks,
Matt

>>>>>>>>>>>>>>>>

---In Homebrew_PCBs@yahoogroups.com, <leon355@...> wrote :

On 29/08/2014 12:25, mattmoose1969@... [Homebrew_PCBs] wrote:

> Hi all,
>
> I am experiencing a problem when developing a UV-sensitive PCB type
> AA16, made by CIF, available from RS Components as stock number 159-6057.

I should have added - how hot is the solution?

Leon
--
Leon Heller
G1HSM

I'll order some LsaerStar film and see if anything improves!

Thanks,
Matt

>>>>>>>>>>>>>>>>>>>>

---In Homebrew_PCBs@yahoogroups.com, <leon355@...> wrote :

On 29/08/2014 12:49, mattmoose1969@... [Homebrew_PCBs] wrote:

> Hi Leon,
>
> I'm laser printing the artwork onto 90gsm tracing paper, as recommended
> by someone who has done a lot more of this than I have.

It might not have enough contrast, try using LaserStar film. I think
it's available from RS, or you can get it from Mega Electronics (UK).

Leon
--
Leon Heller
G1HSM

Hi Bertho,

Thanks for your suggestion, that makes total sense. I'll give it a go next.

Regards
Matt