Aproaching definitive PCB

Using Arduino General Electronics
#1

First of all it’s the first time I am doing a complex project with Arduino and also with any electronics.

For the past months I have been working on some sort of synth with an AY-3-8910 chip.
I have finished with almost all of the Arduino programing and did a schematic with Eagle for taking the next step, creating a PCB and soldering the components for a definitive installation.
From the attached image you can see that the circuit is somewhat complex and after designing the actual board (2nd image) everything fits in a 12x12 cms square (4.8x4.8 inches)

Now, using Eagle autorouter it’s imposible to do all the connections on a single layer, so I have to use two (up and bottom). That increments the difficult of printing and etching.

I tried printing both layers with the toner method (using a magazine paper) but I failed because I couldn’t align both layers correctly, I think it’s because it was difficult to do with magazine paper. After doing the holes with a manual drill and a 1mm drill bit I noticed that the component holes where off from the actual printed place.

What would you recommend me to do? Should I try again with photographic paper? Do you think it would be better separate it to different single layer modules and connecting them with cables?

What do you think?

Thanks!!!

Schematic complete.jpg
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Boardcomplete.jpg
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#2

I would create Gerber files, and send them off to one of the pcb houses to get the boards made professionally.

#3

I thought about that, there are 2 inconveniences.

1) I live in Argentina so I would have to wait like 2 months for it to get to me. 2) I may have some errors on the design so everything will be wasted if I can't correct them. That's why I wanted to make this by myself first, in order to test it.

I may try consulting some prices with China companies, the shipping to here is cheaper from China.

Also, by ordering one alone I think the price will be high, right?

#4

A good way to help line them up is make reference points on the outside of the board (like one on 2 opposite corners), once you have one side, drill tiny holes in them and poke a pin though them, now when you go to put the other side on you can poke though the paper on your reference marks

it wont be perfect, but its better than trying to eyeball it

two other things to keep in mind is that autorouting is pretty dumb, and sometimes just moving something or rotating it will give you what you need

Also, by ordering one alone I think the price will be high, right?

I doubt you will find a house with a minimum order of one, and it adds up real quick

#5

I would try without using the autorouter - it seems like it will be hard or it will take a long time, but its worth it.

I find that doing the power first helps, and if I have the top layer for mostly going horizontal and the bottom layer vertical things get a bit easier. You could of course swap those around.

This might help you condense your board into a smaller area so you can get it into one of seeed studio’s 10cmx10cm board pricing ranges - which is a lot cheaper than their 15cmx15cm price!

One things am doing at the moment is splitting up component parts of a circuit over two boards to fit into the 100x80mm board size restriction in Eagle, then connecting the relevant parts and power with a double row pin header.

One last thing, and its not important but it bugs me, odd angle traces look ugly.

#6

You might check these guys out. Others here have been using them. So cheap, they're probably china. Click on OpenPCB.

http://iteadstudio.com/store/

#7

iteadstudio is definitely China. 12x12 falls into the >10cm x 10cm size, I think $22 for5 boards.

#8

Whether you do it yourself or send it out is immaterial except the board house can mate top and bottom a lot better than you can. There are easy techniques I have used for many years. The first is to make sure that the Datum or Origin of the board has a common marker in the same place on top and bottom. If you use 2 alignment targets at diagonal corners and outside of the art work then align the film by the targets and clamp the film in the contact frame, expose one side and without moving the registration from top to bottom flip it and expose the other side, develop, etch, clean and drill. The process is very easy but you NEED to create a method to align both sides of the film on the sensitized area and off board so they can be seen and used. This is the way to get the holes to line up. Try it with a small PCB as practice, You will soon become used to the process and it will get a lot better. I haven't made a 2 sided board at home in 40 years but that was the way I did it... Right out of a book on home-made PCB's... Worked great.

Doc

#9

In the board image you can see that I made some lines above and under the board to guide both layers, maybe as you say, doing something like that on four corners it's better, I'll try that. Another thing that made the layers to dis-align was the paper (I used magazine paper), it wrinkled and made it more difficult I think. I should try with photo paper.

#10

be picky with photo paper, the stuff I got with my printer (like 2 years ago) is paper with a plastic film on top, so its like ironing on cling wrap film

to this day the best experience I have ever had with home made PCB's is the photo mask method, but you got to buy sensitized PCB's and developer, basicly you print your mask out on transparency and stick it under a fluorescent light for a few min, develop and your good to go

#11

CrossRoads: iteadstudio is definitely China. 12x12 falls into the >10cm x 10cm size, I think $22 for5 boards.

I've used ITead Studio for three lots of boards. I was very happy with the quality, and I received them in under two weeks.

#12

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