Any PCB - easy and cheap

[Koy]

Not everybody has money to spend them for professionaly made PCB (nice but expensive). There are lot of ways how to "home"made any PCB. I have very good experience with one method. When doing the bord on the PC simply print the board ( not mirrored version!) out. Than make the copy on the copy machine ( try to get the wires the darkest as possible). Put the copy on the board (printed face on the clean copper surface of the board) and with the hot electric iron reprint the original on the board. Using any water resistant marker paint the places that can not be etched. Than you can start etching ( with FeCL3). That is all.

[GRollins]

I found that the iron we've got wasn't flat on the base. It *looked* flat, but it wasn't flat enough to do the job properly. I tried various things, but hit upon the idea of using the oven for heat and bricks (ground face-to-face until flat) for pressure. It works well within its size limitations.

Grey

[Pete Fleming]

Grey, here’s a trick from woodworking to get tool soles flat. Take a piece of glass and glue some “wet and dry” sandpaper to it. Spray contact is good. The grade of paper will depend on just how much you need to remove, but go finer until it’s as polished as you want it. Place the glass on a flat surface and rub the base of the iron on it until even. Use the paper dry, and if you’re having trouble seeing if it’s flat draw lines across the base with a marker. Provided you’re not using a “non stick” style iron you’ll have a perfectly smooth, yet undamaged, iron.

May be easier than the bricks.

Cheers,

Pete

[GRollins]

Pete,
Aye, I'm used to that trick...been doing woodworking almost as long as audio (recently got a new tablesaw--my old one was pretty dead). The problem is that irons (at least the one we've got) have a chrome plating on the bottom. Once that's gone, the iron rusts. Perhaps an iron retired from service could be flattened.
However, I had another problem in that I couldn't get consistent pressure over the entire surface of the circuit board. Bricks solved that problem, also. I can put on bricks (about 4.5 pounds each) until I get the right pressure (about 1 psi, as near as I can determine, i.e. a 2"x2" board would take one brick, as that's about the right pressure).
Worse yet, if the board's of any size, you've got to move the iron around to heat all of it. Ultimately, the board gets heated unevenly, either in temperature or duration.
My main limitation now is the size of a brick. I'm open to suggestions for larger flat surfaces. The only thing I've thought of yet is getting a pair of pieces made up by a monument (tombstone) maker that are polished. I have not yet pursued this.

Grey

[Pete Fleming]

Ok, yes some of the irons I've used were aluminium. What about using a piece of marble or granite. I've seen very inexpensive marble slabs sold around my part which may be of use for you. Used by those wise in the ways of cooking (ie certainly not me) to roll dough upon when making bread.

Cheers,

Pete

[Thoth]

Try a stone floor tile (not simulated). These have a polished surface, and are readily available in sizes up to 18"x18" (maybe larger). You only need one of these. You can pile bricks on top to get the right pressure.

If this isn't large enough, try a local custom countertop place. They'll probably have 'scrap' up to 30"x30", but it will cost more.

Good luck.

Thoth

[Koy]

I don´t understand. Large PCBs? Do you produce computers or so? There are good ideas using thombstone. But why?
Simple ironing is capable to copy A4 form at least and is more flexible. I am afraid constant pressure (tile etc.) does not produce good results. And there is no possibility to control the temperature.

[Thoth]

I don´t understand. Large PCBs? Do you produce computers or so? There are good ideas using thombstone. But why?

Grey had stated that he didn't have a flat iron. Flatness is required for this transfer method. He said that he used bricks with their faces flattened, and that the weight of one brick was about right for a 2"x2" square.

With this information, it can be seen that the largest PCB that can be created with this method is about 3"x8" (or whatever the size of your brick happens to be). This size is adequate for a medium power Class-B amp, or a low-power Class-A amp.

For anything above that, the size of PCB needed to hold the output devices and emitter resistors is too big, and another method is required. Grey specifically asked about larger PCBs, so I assume he's hit that limit.

And there is no possibility to control the temperature

Grey said that he uses an oven to provide the heat. I assume that he heats the bricks in the oven, then sets them on the paper/PCB stack.

I found two URLs for creating PCBs, that might be useful. They are 'http://www.al-williams.com/wd5gnr/pcb.htm' and 'http://www.eng.uci.edu/~rshah/pc-board.html'.

I hope this helps.

Thoth

[GRollins]

Thoth is correct. I preheat the bricks I will need in the oven for about 20 minutes, then build a stack with the number of bricks I require for the pressure. Temperature stability is excellent (the thermal mass of a PCB is trivial compared to a few bricks). I place one brick underneath as a base, then the PCB, then one to three bricks, depending on how much pressure I need. Incidentally, I wrap the PBC and transfer paper in a paper towel to keep the PCB from being scratched by the bricks. Yes, the paper turns a golden brown from the heat, but does not ignite; I've never had a fire problem.
I also turn the oven off during the "baking" phase. The oven walls and bricks maintain temperature quite easliy for the 3 min. or so needed to produce a transfer.
Thoth, your suggestion about a floor tile is a good one, as far as the surface flatness goes. Perhaps if I look earnest enough I can get Lowe's/Home Depot to give me samples to 'check how they look in my kitchen' and so save money. I am not sure that the thickness (1/4", plus or minus a bit?) will be mechanically strong, but I'm certainly willing to give it a try. Seeing as how I've got a second pair of Aleph 2's to build, I may be able to try this fairly soon.

Grey