How to make 2-sided Printed Circuit Boards

Often, when making circuits, it can be nice to put your finished project on a printed circuit board(PCB). Making single sided boards is easy enough, but sometimes a circuit is too dense or complicated for all the traces to fit on one side. Enter double sided boards. They are actually much easier to make than one might think, provided that you don't rush through the process. In this instructable, I will show you how to make double sided PCBs easily, and somewhat quickly.

Step 1: Materials

Things you will need:

Strip of 2-sided copper-clad board. The size of this will depend on the size of your layout.

Paper. You don't need anything fancy. Just get basic gloss photo paper.

Tape. Scotch tape works fine.

Sponge. I use a potter's sponge (available cheaply at art supply stores), but any type of sponge will work.

Ferric Chloride. Available at most Radio Shacks.

Iron.

Light Box. Optional, but very useful. If you don't have one, you can make one easily, or use a window on a sunny day.

Drill Press. You really don't want to use a hand held drill.

#60 Drill Bit.

Saw.

Acetone. This will dissolve toner in a hurry.

Scotch Brite Pad. Buy a lot of these. They wear out.

Rubber Gloves. You really don't want to get ferric chloride on your skin.

Safety Glasses. Need I say more?

Comments

[pkrouse]

Great instructable, but I thought I'd mention a safety issue here.
Ferric chloride is safe enough for disposal,such that is is, but be advised that the copper that gets etched into the solution is quite nasty. Even in trace amounts, it is poisonous to fish, and possibly other aquatic wildlife. There is an excellent instructable on the site that describes etching with muriatic acid and peroxide that lasts a long time, is fast and clean, and lets you avoid putting copper down the sink. Search for 'a better etching solution' and you'll find it. Food for thought. Oh, and the muriatic acid/peroxide etchant is CHEAP.

[mguima]

If you use muriatic acid and peroxide, doesn´t the copper gets in the solution, too? Or does the copper get precipitated? BTW, isn´t muriatic acid and peroxide toxic, too?

[zwheel]

Yes but it is re-usable. The copper doesn't get into the environment if you keep it to use again!

[pkrouse]

That is sort-of the point. With the muriatic acid/peroxide etchant, the copper precipitates out and collects at the bottom. I am not sure it is reusable at that point (maybe it is) but you can dispose of it at a toxic waste facility if you like, and keep on using the etchant again and again. My only point was that with FC etchant, you have to dispose of all of it when it can no longer etch your boards. At least with the muriatic acid/peroxide etchant, you pour it off the sediment into a new container and keep going.

It's cheaper than FC up front, and stays reuseable. Win-win in my opinion.

[mguima]

I have the same perchloride jar and solution for 25 years. Sometimes I add some new perchloride. The copper isn´t in the environment.

[pkrouse]

Well that's pretty cool then. This is a ferric choride etchant you are talking about, or an ammonium persulfate powder? When you mention perchloride, I am not sure what you are referring to.

[tinygeek]

Frankly, everything that's going to dissolve copper is toxic.

I'm not a chemist, and I'm not going to pretend to be, but I think the copper doesn't precipitate.

[pkrouse]

The instructable I referred you to details how the copper comes out of solution and can be removed for disposal as toxic waste. At that point, the solution is "self-regenerating", for lack of a better term. Ferric chloride, on the other hand, gets spent and has to be replaced in its entirety. Sure, you can dispose of the spent ferric chloride properly, just like the precipitate from the instructable I mentioned, but you're better off in the long run (just my opinion) with the regenerating etchant. I encourage you all to find and read the instructable.

[Computerman29]

Hello All,

I had ZERO success with ANY toner transfer methods until I tried these two things together:

1) After scrubbing the copper board, drop it into the etching solution for a few seconds. Remove and rinse. Be careful not to touch the copper after it is dipped/rinsed.  It roughens up the surface and makes the toner stick much better. It also removes any oils and deep-down dirt that the scrubbing missed.

2) When repairing traces with a "sharpie", roast the board on your iron for about 30 sec. to make sure the "sharpie" ink is completely dry, then etch.

I use a beat-up HP Laserjet 6L, press-n-peel blue with my iron on about 3/4 full heat and moderate pressure, and get great results. Your millage will vary. Experiment a bit. It is probably different with photo paper, but try the above tricks. Good luck!

[tinygeek]

That's cool. I like the idea of quickly putting it in the etchant to clean it. Thanks for the tips!

[jeff-o]

I wonder, is it even necessary to drill the registration holes if the two sides of the pattern are already aligned using the light table?  As long as there's some overlap the board could just be slid in between the pieces of paper and fused as-is.

It might be necessary to use heat-proof Kapton tape, though.

[tinygeek]

There is a "fold over" method of registration. The two sides are printed next to each other and then folded around the board. This is just the way I find easiest, but to each, his own.

[jeff-o]

Hmmm, that might also work, but you have to factor in the thickness of the board.  For what I've got in mind, that may introduce too much error.

One further question, have you ever tried doing the toner transfer to both sides of the board at the same time?  I've only ever done it one side at a time and it tends to smudge the side that's already done.  I want to avoid that, too...

[tinygeek]

I've tried transferring both sides at once, but I find that hard to do with an iron. That tends to work better with a small pouch laminator, but I don't have one of those. The one time I did use one, it worked quite nicely. I've pretty much stopped experimenting with toner transfer since I started milling my boards, but I would imagine that if you had a jig to hold the board still and in the same place, you could do one side after the other without smudging.

[jeff-o]

 Well, I gave it a shot.  I'm happy to say that I achieved nearly perfect alignment with the top and bottom pattern - Hooray!  I did it by lining up the layers using a light table, then taping together three of the four edges.  Then I just slid the board between the layers and went at it with an iron.

The toner transfer itself could have been better.  Perhaps it was not heated enough, or some dust or fingerprints got on there.  Still, I should be able to repair the board with some etch resist pen.

[tinygeek]

Awesome. I'll have to try that if I etch again.

[UbuntuNinja]

Does a double sided PCB only work if you have a combination of through-hole and surface mount components?

[tinygeek]

No, If you don't have through hole components, you can make vias. all you have to do is solder a wire through them. No SMD is easy, but no through hole is a little more work definitely doable, though. I've found that with the standard EAGLE via size, magnet wire works well, and also doesn't take up any space.

[bigmike55]

 Thank U tinygeek. Up till now I have been blowing my brain out as to how to etch double sided PCBs. I am used to lacquering one side and etch the other. after that side etches, lacquer it, then remove the lacquer from the first side and set it to etch. All this lacquering and etching is time consuming. Never thought of sponging it. This is a real cool thing. 

[MACKattacksnipe]

Cha bra but ill stick with my radio shack ones

[munchman]

This is cool, definitely useful. (I hope you don't mind, I posted about this on my blog)