RE: PCB Etching (Was : Phono Faceplate - Photos)

["Ian" <I.Bird@xxxxxxx>]

Hi Keith

I took the plunge today and registered the lite versions of Proteus ARES
and
ISIS for 30 quid (special offer). All I have to do now is figure out how to
use them.

How did your etching and circuit building go as below. I have collected all
the bits I now need and plan to have another go this weekend. I still
haven't got the etching fluid out but I will this weekend (in the garage).
I
have enough for one pint so only one weekends worth.

A quick question. I have lots of clear transparencies from my college days
and plan to print on these using a laser. You are talking about opaque
film - are you referring to ink jet tranparencies which are coated? I
assume
this is not ideal if thats what you mean. If not, why opaque drafting film
and where do you get it? Will ordinary transparencies do?

Do you print the component outlines and numbers like R1, C1 etc. on the
'top' side or work from a printout. How can these be printed?

More mundane questions i'm afraid but I'm learning fast I think (hope).
Hopefully an IR board update will follow next week sometime.

Ant chance of that text file on the etching process. I daresay I am not the
only mug out here trying it out.

Thanks

Ian

-----Original Message-----
From: Keith Doxey [mailto:keith.doxey@xxxxxxx]
Sent: 18 November 2000 01:52
To: 'ukha_d@xxxxxxx'
Subject: RE: PCB Etching (Was : [ukha_d] Phono Faceplate - Photos)


Hi Ian,

Its now 01:40 and I have finished etching boards for the night !!!
I started at about 22:00.

I TRIED to make 4 boards.
I SUCCEEDED in making 2 :-(

The printouts were done on HP inkjet transparencies but were not 100%
black. Laser gives much better results. I put a sheet of opaque film over
the printout to diffuse the light slightly.

I did originally try printing on the opaque film but the ink just smudged.
The HP transparancies have a special coating that stops the inks smearing.

Attempt 1 Artwork and Opaque film
8 minute exposure - not long enough. The exposed part of the resist did not
fully remove and the etchant wouldnt touch the board. FAILURE

Attempt 2 Artwork and Opaque film
10 minute exposure - not long enough. The exposed part of the resist did
not fully remove and the etchant only touched the board in some areas.
FAILURE

Attempt 3 Artwork and Opaque film
12 minute exposure - All the unwanted resist was removed but the outline of
the tracks was slightly blurred and I had 2 or 3 areas where the track
shorted but that was cleared by scraping with a scribe between the track.
FAIRLY SUCCESSFUL

Attempt 4 Artwork Only
10 minute exposure - Perfect. SUCCESS
Crisp tracks and complete removal of the unwanted copper.

Ideally you need opaque drafting film that is printed by laser. The artwork
needs to be on the side of the film in contact with the board otherwise the
image gets diffused by the film.

I have a text file that describes the entire process on my other PC. I will
email a copy tomorrow.

Hope that helps

Keith

-----Original Message-----
From:	Ian [SMTP:I.Bird@xxxxxxx]
Sent:	17 November 2000 15:49
To:	ukha_d@xxxxxxx
Subject:	RE: PCB Etching  (Was : [ukha_d] Phono Faceplate - Photos)

Thanks Keith

Now the 100 dollar question. A while back I bought a bubble etch tank and I
have had fish tanks before (lots of spare pumps) so no expence there. In
fact the tank is still wrapped in its original packing. I also have the
mother of all Lasers for home use of which the less said the better as you
know. I also have the schematic in Proteus and it prints beautifully.

Now, the bits I don't have
I am not sure how you are getting the PCB printout (printed on what?) onto
the board and the steps to finally putting it into the etching tank. Can
you
point me at any literature or web addresses for this (or explain if you are
really kind). What is the relationship between the light box and the final
ferric chloride process.
I know of one of these UV boxes I can borrow to try it out. All I need is a
little knowledge and one or two other bits i.e. pre-sensitised boards.
Any part numbers e.g. RS or M*****S so I can read the leaflets would be
great.

Thanks

Ian

p.s. sorry if these are really silly questions but you have to start
somewhere!


-----Original Message-----
From: Keith Doxey [mailto:keith.doxey@xxxxxxx]
Sent: 17 November 2000 13:58
To: ukha_d
Subject: RE: PCB Etching (Was : [ukha_d] Phono Faceplate - Photos)


Hi Ian,

I use photo etching.

Way way back in 1980 I bought a UV Lightbox and used to use drafting film
and stick on templates and track tape. A bit fiddly to do but it gives
excellent results. The track tape is TOTALLY impervious to the UV light so
you get perfect exposures.

Develop the pre-sensitised board in Developer (weak Sodium Hydroxide) and
then etch in Ferric Chloride.

I now have an excellent PCB/Schematic package called Proteus
http://www.labcenter.co.uk
for which thee is a shareware version available as well.

My biggest problem at the moment is lack of a Laser Printer although this
will hopefully be resolved very soon. I used to use the laser printer at
work but since changing offices we have a crappy printer that has a habit
of
depositing black lines on the image. I think it needs a damn good overhaul.
My inkjet printer gives less than perfect results. The image is clear but
the black is nowhere near dense enough. This means I have to be EXTREMELY
careful with the exposure times or I remove all the photoresist :-(

If you do opt for the Photo etch method BUY THE PRE-SENSITISED BOARDS.
I had a load of plain copperclad board bought as part of a bargain pack and
decided to spray it myself. I bought the special spray, cleaned the boards
carefully, sprayed them in near darkness (not an easy or pleasant task) and
then scrapped the lot. The surface of the boards was covered in "fish
eyes"
with a totally uneven covering of resist and after working out the
difference between pre-sensitised board vs plain board + spray + time
p***ing about, the pre-sensitised board won hands down.

I did invest in a bubble etch tank last year along with aquarium pump and
the results are amazing. The quickest etch times ever with all areas of the
board evenly etched.
You do need to cover anything in a 1 metre radius with old newspaper though
because the little bubbles pop and spash ferric chloride everywhere.

Remember, EYESHIELDS, GLOVES, VENTILATION.

Be careful

Keith

> -----Original Message-----
> From: Ian [mailto:I.Bird@xxxxxxx]
> Sent: 17 November 2000 09:36
> To: ukha_d@xxxxxxx
> Subject: RE: [ukha_d] Phono Faceplate - Photos
>
>
> Keith
>
> I am making a PCB for the IR circuit at the moment and am
> just about ready
> to etch this weekend. If all goes well I should have two
> pairs by Sunday. I
> was wondering - your circuit is much more complicated than
> the IR one, how
> do you get it onto the copper. I have used the iorn on
> thingys that are
> printed with a laser and then touched it up with a pen. This
> has not been
> altogether successful. How do you prototype?
>
> Thanks for the forthcoming words of wisdom.
>
> Ian
>
















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