Introduction: How to Make 2-sided Printed Circuit Boards

Picture of 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

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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?

Step 2: Print Your Board

Picture of Print Your Board

I won't tell you how to lay out a board. If you want to learn, SparkFun has a great tutorial.http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=109

Put your photo paper in to a laser printer. Most printers have a setting for the density of the toner. Turn that all the way up, and print your boards. Check to make sure they printed correctly, things are mirrored correctly, etc.

Step 3: Cut and Register Board Layers

Picture of Cut and Register Board Layers

Cut out your two layers. Leave at least 1/4" around the board on three sides. Leaving the other side longer is good.

Now, turn on the light box. Place the bottom layer facing up, and the top layer facing down. Line them up so that all the pads are aligned evenly. Then tape around the edges and draw a box outlining the board dimensions.

Take the two pieces of paper off the light box, and tape them down to a piece of copper board. Now, drill the registration holes. You should drill at least three holes in an asymmetric pattern around the edge of the box. The holes should go through the paper and the board. Un-tape the paper and board.

Step 4: Toner Transfer

Picture of Toner Transfer

It's time to transfer the image off the paper, and onto the board. This requires a clean board. As you can see, mine was pretty oxidized. Use a scotch brite pad to scrub it clean. Do not use steel wool. It will wreak havoc on your board. Once it's nice and shiny, rinse it off and blot with a clean cloth. Don't touch it. the oils from your skin will interfere with the transfer. Let it dry completely.

Find the side of the board that has holes that match the ones on your copper board. Line it up so that all the holes are aligned. The light table is helpful when doing this. Once aligned, tape two sides so it won't move. Heat up the iron. Put it on the hottest setting. Then iron over the paper, pushing down hard. You have to push down really hard. Do this in 30 second bursts for five to six minutes. When you're done ironing, run the board under cold water until it's cool. then peel off the paper. Rub it with your finders until there's no paper left on the board. That should be easy, as usually not much sticks.

Step 5: Etching

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I use the sponge method of etching. It's not really that difficult, and is much faster than tank etching. It also has the nice benefit of allowing you to etch one side at a time. You'll want to use a utility sink, and a tub.

Before you do anything, put on your safety glasses and gloves.

Soak your sponge with water. Then squeeze it out. Do that four times. Then, put your sponge into the tub, and pour about a tablespoon of ferric chloride into it. Begin to wipe the board with the sponge. Don't scrub, just wipe. The copper should start disappearing very quickly. Keep going until you have etched a satisfactory portion of your board. Then rinse the board under running water until all the ferric chloride is gone. Wash out the sponge, making sure to use lots of water. Such a small amount of ferric chloride diluted with so much water is OK to put down your drain. Get rid of your gloves, or wash them off and reuse them if you like.

Step 6: Repeat

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Repeat steps 4 and 5 again to do the other side of the board. That's it for etching. Now all that remains is to drill the board, cut it out, and get rid of the toner.

Step 7: Drilling

Picture of Drilling

This is probably the simplest part. Put the #60 bit in the chuck of your drill press, and make sure it's centered. Then drill. Make sure that you go slowly so you don't blow out the pads on the bottom. It is also a good idea to have a piece of smooth wood underneath to drill into. I use a piece of 1 1/2" MDF.

Step 8: Finishing Up

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All that remains is to cut the board, sand the edges, and get rid of the toner.

Cutting is easy, just be careful, wear safety glasses, and don't cut the traces or pads.

Sand the edges to smooth them out. 120 grit sandpaper works well.

Take some acetone, and wipe down the board. The toner should be no more.

And that's it! You're done!

This is my first instructable, so please feel free to tell me what you think.

Comments

vishwa.basnayake.9 (author)2014-08-10

nice

pkrouse (author)2011-05-09

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 (author)pkrouse2012-11-03

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 (author)mguima2012-11-19

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

mguima (author)zwheel2012-11-19

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 (author)mguima2012-11-20

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.

pkrouse (author)zwheel2012-11-20

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.

tinygeek (author)mguima2012-11-03

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 (author)tinygeek2012-11-07

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 (author)2010-04-09

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 (author)Computerman292010-04-10

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

jeff-o (author)2010-02-17

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 (author)jeff-o2010-02-17

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 (author)tinygeek2010-02-18

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 (author)jeff-o2010-02-18

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 (author)tinygeek2010-02-18

 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 (author)jeff-o2010-02-19

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

UbuntuNinja (author)2010-01-02

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

tinygeek (author)UbuntuNinja2010-01-02

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 (author)2009-11-14

 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 (author)2009-09-26

Cha bra but ill stick with my radio shack ones

munchman (author)2009-09-25

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

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