hobby double sided pcb's

Actually I found a post on the yahoo homebrew_pcb group and on google that suggested using either of the following to coat the other side

nail polish lacquer or varnish

And the last two come in spray bottles which should make coating much easier

samiam wrote:

Print two images, red side and blue side (call them component and solder, top and bottom, whatever you want).

Lay down red side on one side of the pc board substrate using iron-on or photo process, whichever you prefer.

Spray paint color of your choice on the other side.

Etch.

Remove spray paint with paint thinner.

Drill two holes through red side pads.

Pierce blue side artwork same two holes.

Run small wires through red side pads and blue side artwork holes (registration).

Lay down blue side art on the pc board substrate.

Spray paint red side traces.

Etch.

Remove paint with paint thinner.

Clean board.

Jim

RST Eng>Spray paint color of your choice on the other side.

I'm missing something here. Why is paint necessary at all?

If you do this when you iron on the 2nd side of each board, paint is not necessary and everything can be etched in 1 go.

Its a pain in the ass trying to align the holes without doing them one at a time

Yes but getting the holes to register is much more difficult with this method. Its really better to do them one side at a time

samiam wrote:

After ironing-on the 1st side, I drilled out 1 hole each near opposite corners of the board and stuck a straight pin thru each hole. I never had the slighted problem getting the 2nd layer registered.

...and registration-wise, I still don't see how putting on and taking off paint changes anything. . . It would be nice if you left in the attribution in your blockquotes.

You put on the paint so you can etch the first side separately from the second. That way, the drilling and handling doesn't mess up the first side. Iron and etch ONE side, drill and align, iron and etch SECOND side.

If you have a double sided UV source it is a lot easier to do it photographically. Take your plots of both sides and line them up on top of each other. Stick them together round three edges to make an envelope, put pcb in envelope and expose to UV. Others have suggested sunlight works better than a UV source so this may work for you.

Colin

By the time you have bought all the chemicals, copper clad board etc. Then still failed.

It would have been cheaper and less traumatic to get someone to make it for you.

Why the defeatist attitude?

We've had this discussion before. There are many valid reasons, including cost, for making your own pcbs. It's not *always* the right thing to do, but sometimes it is.

Even if you DO fail the 1st time, you have a greater appreciation of ways to get the pros to get your boards back to you more quickly. (Fewer mistakes/questions == Faster turnaround)

Maybe. Depends on what parameters count most to you and how you weight your time:

DIY PCBs == Protos *NOW* -- Tim Auton

Good technique + cheap materials == Useful PCBs -- slebetman, DJ

If the boards are going to stay in-house, DIY could be just the ticket. . .

I have been in electronics for 25-30 years and have never been impressed with amateur PCB's.

If we show a customer a PCB it has to look the business.

I think it requires quite a bit of skill to produce PCB's at home. Even the drilling requires a high level of dexterity to ensure the holes at least line up fairly well.

Over etching/ under etching both cause problems.

One problem I had was uneven etching, where one side of the board was over etched and the other side under etched !

I have seen the professionals get it seriously wrong so I dont expect much from an amateur.

I once got a PCB back and it was all copper but it had the holes in the right place. Some idiot had input a wrong size into the system at the pcb manufacturers end. At least we got it redone free of charge.

I don't expect mine to be impressive, just quick and functional.

I hope you put as much effort into your grammar.

I use a sponge to etch, so I can control over/under etching fairly well. At least, well enough for my unimpressive boards.

Amateurs built the Ark; professionals built the Titanic.

Jim

You probably don't get out much then. :-) I've seem homebrew PCBs that looked as good as what you get off of a $40k LPKF-type machine, for instance.

For a final PCB, sure, but personally I'd be a little wary of any company that *didn't* have a bunch of cut boards or "ugly construction"-style boards around that they did various tests/development on. It tends to vary with the compleixty of design, of course -- with digital boards there's often no need for a prototype.

Sure, it does, and for those in the U.S. getting PCBs made commercially is cheap enough that it's difficult to argue that it's worthwhile to make your own unless you simply enjoy doing it. For many people outside the U.S., even something like US$39 is still expensive enough that most hobbyists have no choice but to make their own.

You can eliminate 3 and 4 if you are careful.

Many years ago in my youth I made double sided boards one at home one side at a time as you describe by floating the board on the surface of the etchant. Ferric chloride has quite a high surface tension and it if fairly easy to float the board on top of it. It is even possible to agitate it a bit if you are careful. If it sinks, no matter so long as you fish it out again quickly.

You can eliminate 3 and 4 if you are careful.

Many years ago in my youth I made double sided boards one at home one side at a time as you describe by floating the board on the surface of the etchant. Ferric chloride has quite a high surface tension and it if fairly easy to float the board on top of it. It is even possible to agitate it a bit if you are careful. If it sinks, no matter so long as you fish it out again quickly.

And this ladies and gentlemen is the reason our country is in decline manufacturingwize.

This notion that: SOMEONE ELSE should always do it for you: CHEAPER

I need prototypes so sending them out at $100 a pop for a 4x6 double sided boarded is a waste of money.

As for gathering the chemicals and tools - I ALREADY have that from earlier projects and with the exception of FECL and bare copper- its all a one time investment

More like steady, unless you have an overwhelming interest in employment rather than production.

Only if your overall time is worth less. Their productivity and quality is bound to be higher. Hobbyists can count their time at $0/hr (or perhaps they would pay for have such fun) but the rest of us need to use a higher (positive) number. You may lose out on the learning of how to make boards, but you will learn how to create usable Gerber files and drill files.

And will you dispose of the chemicals responsibly when they are spent? That's typically a significant cost for businesses that produce prototypes.

Best regards, Spehro Pefhany

Absolutely. I pour it into a plastic bottle and seal the cap. Then write FeCL and hazardous on the side.

I take it to either the waste disposal plant in the next village or to the local repair shop. They know what it is and charge $3 to dispose of it.

Trust me they know what it is and its not mixed with other liquid waste they have to dispose of. Its one trip to the waste disposal/threatment plant for them.