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Dan Moos 6th April 2013 06:19 PM

diy pcb materials
 
I plan to start experimenting with the toner transfer method. I have several questions which I suspect have been answered a million times here, but apparently I don't know how to tell the search tool to find properly :rolleyes:.

I've been looking at mouser, but am open to better places to look.

Is 1/16" with 1 oz. copper sufficient for solid state power amp work?

Will single sided boards be fine? I have been doing hand wired tube amps up till now, so I'm not sure what can be done on one side without resorting to jumpers. Is there any down side to ordering double sided boards, and "erasing" the copper from the unused side if it turns out I don't need it?

How is a PCB typically cut? The mouser stuff I am looking at is a 1/16" FR4 laminate from MG Chemicals. If I wanted to print multiple circuits on a single board, what is the best way to cut the boards?

I know pro boards have a solder mask layer that keeps the solder where its wanted. I never hear about this being done on DIY boards. Is there no product that one could apply to a board that would allow solder to only "stick" to copper and pins, and not bare fiberglass? Its not a big deal to me, but would be a cool way to get better build quality if it exists.

Along the same line, I know that pro boards aren't individually soldered, but put in a sort of "solder bath", getting quick and extremely accurate results. Again, this isn't a big deal, but it would be cool if there was some sort of DIY method that sort of did the same thing.

What current production cheap laser printers are known to work decently. I've heard that Brother printers are out. There seems to be monochrome printers well under $100 out there from various manufacturers, but I don't want to get something that doesn't work. I have an inkjet that I am happy with for other printing tasks, so this thing would be only for PCB work.

Is etchant solution all basically the same?

As far as ground planes go, is it typical to have a ground plane to serve all the small signal stuff, and have that plane go to some sort of star point while the high current stuff stays off the plane?

Where is the best place to get all this stuff!

godfrey 6th April 2013 07:02 PM

Quote:

Originally Posted by Dan Moos (Post 3443679)
Is there any down side to ordering double sided boards, and "erasing" the copper from the unused side if it turns out I don't need it?

It'll waste a lot of etchant solution. You may want to leave most of it there as a ground plane.

Quote:

Originally Posted by Dan Moos (Post 3443679)
What current production cheap laser printers are known to work decently.

I haven't tried it, but I have a sneaking suspicion photostats might work (since photocopiers also use melted toner). The idea would be to print it with an inkjet printer, then photocopy that onto the appropriate paper for transfer to the PCB. If that works, there's no need to fork out $$$ for an appliance that just wastes space in your home 99.99% of the time.

Maybe smarter people than me will comment on the viability of this.

counter culture 6th April 2013 07:47 PM

The problem with photocopiers is that the reproduction isn't dimensionally accurate. They often stretch the image slightly, OK for all-discrete designs, but a problem with thru-hole ICs.

You can usually get someone to make a laser print for you. The alternative is to keep single and doublesided resist coated board on hand and make masks using an inkjet printer on inkjet transparency material. Despite the roughness of the transparency material this works well, but the contrast ratio of the mask is only just sufficient to work, so you need fine control of the UV exposure time. There's a thread here somewhere about building an LED based exposure box with a PIC micro timer.

You can buy all kinds of professional-standard PCB production stuff, but the first substantial problem that you run into is plated-thru holes. If you don't have plated-thru holes then all your connections to leaded parts have to be on the solder side of the board. This is manageable, but you may have to dive the track through the board at the last minute with a manually placed wire via. Making plated-thru holes requires pre-drilling the board, filling the holes with conductive ink, and electroplating them. Then you apply photo etch resist, expose, develop and etch them. To drill the holes you need CNC, and then you might as well go for isolation routing instead of etching.

Thru-hole boards are usually wave-soldered in industry. This is what you would imagine from the name.

The best way to manage things for home production is to use surface mount parts. This cuts down the amount of drilling dramatically. You can use wire vias or just straight links on a single-sided board.

Going to SMT means you can use a toaster oven and solder paste. Solder paste is a mixture of flux and tiny solder balls. You can apply it manually with a syringe or make (or get made) a solder stencil, which you put in registration with the board and squeegee paste onto the pads through the holes. Then you place the parts and heat up the board in the oven until the solder flows, which straightens up any skewed parts by surface tension.

You cut the board using a craft knife to make deep scores in it on both sides. You need a steel straitedge. Work carefully, the scores need to be exactly opposite each other and you must apply a lot of force, so be careful not to cut towards yourself, the blade can break and your hand can slip. Put the board on a sharp table edge with the score lines exactly on the edge, press hard on it with one hand and hit the free section hard with the heel of your hand. Job done.

Finally, look at seeedstudio.com. They do 10 off 50*50mm doublesided boards for U$10 + shipping. They also have a special deal for 100*100mm. If you can wait ~10 days, as opposed to needing the board right now, it's a very good deal.

Fun fun fun.

Art M 6th April 2013 07:53 PM

I suggest you start by reading: Printed Circuits Handbook by Clyde F. Coombs, Jr., ISBN 0-07-012754-0 .

This Tome has plenty of information on Process, Materials and Equipment for commercial PCB manufacturing. Then you can research the Toner Transfer method by going to Google.com , there is a ton of information on this subject.

dchisholm 6th April 2013 08:05 PM

You can probably get help from the Yahoo "Homebrew_PCBs" group at http://tech.dir.groups.yahoo.com/group/Homebrew_PCBs/

Dale

counter culture 6th April 2013 08:07 PM

Oh, there are multiple types of etchant.

Ferric chloride or ammonium persulphide or muriatic (hydrochloric) acid (spirits of salt) + hydrogen peroxide. The last is handy, because you can get the ingredients pretty much anywhere, whereas the first 2 need to be obtained from a specialist supplier.

JMFahey 6th April 2013 08:17 PM

Quote:

Originally Posted by Dan Moos (Post 3443679)
I plan to start experimenting with the toner transfer method.
Is 1/16" with 1 oz. copper sufficient for solid state power amp work?

Yes.

Quote:

Will single sided boards be fine? ... I'm not sure what can be done on one side without resorting to jumpers.
Commercial products often use single side + lots of jumpers.
Cheaper/easier than going double face, which requires vias and through hole plating, not practical at home.
The added complexity/delay of using jumpers is the least bad solution, by far.
I desigh "double side" but on the top side use only as few tracks as possible and layout those as straight lines, so a simple jumper can replace them.
Any zig zagging is done below.

Quote:

Is there any down side to ordering double sided boards, and "erasing" the copper from the unused side if it turns out I don't need it?
Yes, you needlessly waste etchant and time, contaminate the Earth, etc.

Quote:

How is a PCB typically cut? The mouser stuff I am looking at is a 1/16" FR4 laminate from MG Chemicals. If I wanted to print multiple circuits on a single board, what is the best way to cut the boards?
Just answered in another thread.
I have a 30" blade shear, but if not there I scratch a small notch on each face, using a hard plastic or Formica knife , the one with a blade like a sharp "hook" and a steel ruler and snap it.
With practice it breaks quite clean.

Quote:

I know pro boards have a solder mask layer that keeps the solder where its wanted. I never hear about this being done on DIY boards. Is there no product that one could apply to a board that would allow solder to only "stick" to copper and pins, and not bare fiberglass? Its not a big deal to me, but would be a cool way to get better build quality if it exists.
There *is* a photoimageable mask which *can* be home applied, or you can silkscreen it (usually 2 component Epoxy "ink") but it's not worth for home use.
Personally I coat the bare copper surface with rosin+alcohol flux and a *good* brush.
Protects from oxidation and eases soldering.

Quote:

Along the same line, I know that pro boards aren't individually soldered, but put in a sort of "solder bath", getting quick and extremely accurate results. Again, this isn't a big deal, but it would be cool if there was some sort of DIY method that sort of did the same thing.
Not at home.

Quote:

What current production cheap laser printers are known to work decently. I've heard that Brother printers are out. There seems to be monochrome printers well under $100 out there from various manufacturers, but I don't want to get something that doesn't work. I have an inkjet that I am happy with for other printing tasks, so this thing would be only for PCB work.
I have successfully used many brands, main factor is paper surface , rather than toner.
As far as the image is black, even and without pinholes, it's fine.
So all new printers work well.
Used ones ? .... wouldn't risk one, unles fully tested: draw an A4 letter sized 100% black rectangle in Corel or whatever you have and print it before buying.
This is the hardest task for any Laser printer.

Quote:

Is etchant solution all basically the same?
Not at all.

For continuous production, classic etchant is Ferric Perchloride.
Stains everything, from clothes to skin, eats any metal it touches (except, maybe lead).

For quickies, Peroxide water + Hydrochloric acid , real fast but in practice single use , does not keep.
Toxic fumes, eats everything, even what it does not touch, burns skin, splashes in your eyes can make you blind, so always use goggles and waterproof gloves.

Am I exaggerating?
Not at all, what do you expect from any solution which eats ***metal*** away in *minutes* ??

Watch many Y.T. videos before working, a few are well made.

Dan Moos 6th April 2013 09:26 PM

Thanks JM!

I figured the etching solution would be nasty stuff.

What about tinning? I see that in a lot of the Y.T. videos. Is it necessary?

Also, any experience with transparency paper? I know that the printer needs to support it, but other than that, how is it? I've read you can sort of "preview" the transfer before you completely peel the paper off this way.

jcx 6th April 2013 09:46 PM

I don't understand the PCB fab hobbyist thing - for myself - or to encourage others

employed in 1st world country you can get pro fabbed pth, soldermasked single boards for lunch money

they work to finer tolerance, deal with limited life chemicals, disposal, have protective equipment, are up the safe practices learning curve...

you will destroy cothes with the etchant - worst case chemical burns could blind - have to safely dispose of the unused and waste chemicals


why bother for a poor result?

you should also learn a few hand protoyping techniques: veroboard, point-to-point, "dead bug"...

counter culture 6th April 2013 09:54 PM

Quote:

Originally Posted by jcx (Post 3443867)
I don't understand the PCB fab hobbyist thing - for myself - or to encourage others

It's not a PCB fab hobbyist thing. It's an electronics hobby thing. There's just no way to get a comparable result as quickly. Dead bug, veroboard, point-to-point just don't match up. I can have an idea and have a board in my hands an hour later.

I use manufacturers too, I recommended one, it's just a question of horses for courses.


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