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Old 8th February 2003, 08:32 PM   #1
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Default making pc boards

I hope I am in the right place to ask this...

Anyway, I have an amp design, and made a pc board layout for it using ExpressPCB. I then did manage to print it out successfully without the stupid grid dots, so I have it just on a piece of paper for now. What type of board is recommended? Copper etched or photo-sensitive? Which is easier? Cheaper? How do I do both? Thanks

If size of board matters, the amp itself is about 3.3"x5.85" and the crossfeed I added (if I use it) is a separate board of about 3"x4" roughly.
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Old 8th February 2003, 09:47 PM   #2
halojoy is offline halojoy  Sweden
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Default Re: making pc boards

Quote:
Originally posted by trespasser_guy
I hope I am in the right place to ask this...

Anyway, I have an amp design, and made a pc board layout for it using ExpressPCB. I then did manage to print it out successfully without the stupid grid dots, so I have it just on a piece of paper for now. What type of board is recommended? Copper etched or photo-sensitive? Which is easier? Cheaper? How do I do both? Thanks

If size of board matters, the amp itself is about 3.3"x5.85" and the crossfeed I added (if I use it) is a separate board of about 3"x4" roughly.
I seldome use PCBs.
When I have done that, I have not used the photo method.

I have just taped the drawn circuit onto the board.
Then I have used a sharp pointed punch to mark out the holes
through the paper.

Then have I have used a pen with water resistent ink
to draw the circuit by hand, on the PCB.
Then I have etched.

It is called the direct etching method.
It is good and easy, if you do not need 10 identical PCBs.
In that case photo method is better.

/halo - simple as possible
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Old 8th February 2003, 09:56 PM   #3
sam9 is offline sam9  United States
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Default sam9

I, on the otherhand have made a mess out of PCBs attemted with "Press-N-Peel" and hand drawn. For something as complex as an amp board, I have much better luck with photo etch. I use Datak posative process boards. These are a little more expensive than negative process, but a bit less messy. Also the latest version work with normal 100W bulbs (or even sunlight) - no florescent or UV required.

For very simple cicuits such as a power suplly or a master-slave relay cicuit, I have used pens successfully. You can go one step further and use a demel tool to grind off the copper where it should not be - crude, but fast, inexpensive, and effective.

It is worth trying all of them, because it seems different people have different degrees of success with different methods. Still, I've only heard of one person who was really happy with the iron on method (unless the invested a few hundred buck for special equipment!).
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Old 8th February 2003, 11:19 PM   #4
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Default Re: sam9

Quote:
Originally posted by sam9
I use Datak posative process boards. These are a little more expensive than negative process, but a bit less messy. Also the latest version work with normal 100W bulbs (or even sunlight) - no florescent or UV required.
This is very interesting indeed. I have been looking for photo-
resist that can be exposed without using UV light, but failed
to find any. All photoresist and boards with photoresist sold
here are intended for UV and it is strongly recommended not
to use any other light sources.

It seems from what you say that these boards are rather new,
so perhaps that is an indication that they will appear also here
eventually. BTW, has anyone tried exposing photoresist in
non-UV light? For instance, I do have daylight fluoroscent tubes
which are much closer to UV than ordinarey fluoroscent tubes
and light bulbs are. I will probably make some experiments with
using these in the future, but I would welcome hearing about
other peoples experiences.
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Old 8th February 2003, 11:29 PM   #5
halojoy is offline halojoy  Sweden
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Default I agree with sam9

It is only when you have some simpler, smaller circuit
when the direct etching method can be used.
When things get very complex, and the place is narrow
with thin rails,
some method for copy an original is better.

But for simpler cicuits, or parts of cicuits,
or non-critical stuff,
when you only need 1 PCB,
the direct method is quicker and good enough method.

/halo - the p2p hardwire man
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Old 9th February 2003, 04:03 AM   #6
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I burn my own boards (positive boards) when I need to turn something around the same day -- I use a lightbox that is normally used for viewing negatives -- 6 to 8 minutes exposure is satisfactory. develop the board in a 3% solution of Sodium Hydroxide. Drill the holes before you etch! (Using surface mount means you drilll far fewer holes !) You can touch up the traces with an indelible marker.

The prototyping boards sold by (aaaarrrrghhhh!) Radio Shack actually work very well and are extremely easy to use. I just built a power supply controller with one today.

But remember, TIME=MONEY. You can get prototype boards made pretty inexpensively in the US ./
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Old 9th February 2003, 04:53 PM   #7
sam9 is offline sam9  United States
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For info. Non-UV boards I mentioned are sold by DATAK and called "Premier". Wierd thing is that tey come in the same foil packet as the older types and the insert talks only about UV. There is a plastic packet around the foil packet that includes an inset regarding the standard light version. Recomends a 100W bulb in a reflector at a distance of 12" up to a 5"x5" for 10 minutes. Appearently UV still works if you are already set up that way.

Anyway, the 100W method definately works - I exposed two boards last night. I'm going down to the garage right now to drop them in the ferrous chloride.
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Old 9th February 2003, 05:33 PM   #8
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Default Etching PC Boards!

You guys reminded me of an experience I had as a wee lad, about 11 years old.

I was etching a circuit board in the bathroom laboratory, since it had adequate ventilation and running water- plus the approval of my parents. This was an ambitious project, a 10 watt transistor amplifier based upon the topology of my first amplifier, a 3.85W monaural amplifier: a Heathkit.

I carefully traced the circuit on a 6-inch square piece of fresh clad board, and realized that the plastic solution tray I planned to use was too small!

Off to the kitchen for a suitable substitute. I knew my mother would not appreciate the laboratory use of her pretty Corningware dishes...so I rummaged through the cabinet. Ah! Pie tins! So clean...utilitarian, and flat they are! Surely, Mum would appreciate her son using the old pie tin instead of wares for cooking!

It was at this point that I filled the tray with etching solution, started the timer, turned the vent fan on, and added the copper board to the soup. Then I learned an important lesson in another discipline other than electronics: chemistry!

It's called heat of reaction, I believe. As a chemical reaction takes place, it accelerates rapidly as the ongoing reaction liberates heat...more reaction can then take place at the elevated temperature.

I know many of you are quite amused at this point. Well, I was in a state of amazement and adrenaline-induced activity! The demise of the pie tin was a glorious spectacle indeed!

The etching solution destroyed the aluminum pie tin in record time! At least I knew from my father that one never adds water to a happy reagent...I scooted the disaster into the sink, and carefully washed it up once the fizzing subsided.

My experience in photography led me to a different method of laying the circuit pattern on the board. I like to draw the pattern on acetate, sandwich this layer over the board, and expose the image.

What methods of board production work for all of you? This might be an interesting topic....
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Old 9th February 2003, 06:58 PM   #9
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Default I use Avery Labels

Clear Labels, Avery #8665 , and a laser printer. You use the "reflected" setting in postprocessing and just stick the label to the unexposed board. I have used mylar sheets (overhead transparency medium) with both a laser printer and ink jet.

Sometimes you won't get the deep density in the areas like ground planes and the temptation is to run them through the printer again, but if you are working with 10 mil traces and TSSOP devices it's not a good idea at all.


For holes -- I start them out with a 0.011 drill --

Need light -- a red darkroom safelight won't affect the PCBoard.
Someone has said that if you can get a refillable pen and use acrylic floorwax tinted with green food coloring it should work. Has anyone tried this ?

My last word of advice -- a lot of the pens which say they're waterproof aren't.
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Old 9th February 2003, 07:33 PM   #10
Rob M is offline Rob M  United States
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Quote:
Originally posted by jackinnj
But remember, TIME=MONEY. You can get prototype boards made pretty inexpensively in the US ./
Where's a good/cheap place to have them made? Any recommendations?
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