I painted myself in a corner. How to layout?

Question

I'm a hobbyist working mostly in DC projects. For development and testing, I use breadboards, and later a perforated board. My projects are normally low count: an Arduino Nano/Pro Mini + a few ICs.

All my works are one-of-a-kind, and making a PCB is out of question for me.

I use the ICs and physical board itself to test the layout of components on board. I have Fritzing, but it's not up to the task for planning the physical layout; it's more like an ideal vision of the circuit where wires have no thickness and every thing fits neatly in the matrix.

My problem is that sometimes I paint myself in a corner: after soldering a few things, I found the next pin buried under other wires and components; no way to solder anything. I'd been searching for tips, found none. How is your flow work? How do you do these things?

Here some questions:

1. Solder all component first and wire them later?
2. Wire each component directly to Vcc, Gnd and shared signal or use rails?
3. How to layout for changes? Maybe I need to add something in the future.

Answer 1

Your suggestions are spot on.

1. Solder your components first, but think about what you could use as a wire, e.g. a resistor can be used as a jumper. ICs are the main thing to put in first, as they are set and will have a lot of dense connections. Try and work in a matrix, with all wires/components running along rows and columns.

2. Rails are best - you'll have lots of things going up to V+ and down to ground so fit around that.

3. Leave yourself space in the prototyping phase. You can scale down later if need be, but once you've started small it's hard make it larger. A bit of planning will go a long way :)

You could also try some simple stripboard layout software. A number of them are paid (and surprisingly expensive), but PEBBLE is free and is a good starting point at least.

Answer 2

Even though you are using perf-board to build your projects, there is nothing stopping you from using schematic capture and PCB layout software to lay out the placement of your components.

Doing this would benefit you in several ways:

1. You would learn a useful skill doing this.
2. The software can generate and check your netlist to verify you've actually accounted for each connection.
3. While performing the layout, you may discover that you don't have enough space between parts to route, or that the parts need to be moved. It is easier to move things around in the layout software than it is on a perf board.

I've had good success with the following method:

1. Match the PCB layout on a grid spacing that matches your perf board. This is key, as it allows you to verify on the computer that you will physically be able to place and wire to each part. Keeping on the grid pattern will keep your layout neat and easier to follow later.
2. Route your traces as needed, keeping in mind that tracks on the bottom layer will be implemented as solder bridges/buss wire and tracks on the top layer(s) will be run as insulated jumper wire. If you follow the grid and make an effort to avoid running multiple jumpers on top of each other, any needed troubleshooting will be much simpler.
3. Print both sides of the PCB on a 1:1 scale, with the bottom layer as a mirror image. On the top layer print only the component pads and silkscreen and any top-layer traces. Using different colors for different top layers, maybe to match the colors of the jumper wire you have, would be helpful.
4. Place the printout of top layer on the top (non-copper) side of the perf board, aligning with the grid of the board.
5. Place components through the paper and solder them into place on the bottom side of the board.
6. Any jumper wires needed to implement top layer traces are installed next, soldering them into place.
7. Flip the board over to run any bottom layer traces. Use the mirror-image bottom print as reference to locate and solder those.

Answer 3

As @mguima and @spuck said, use PCB software to do your layouts. They will help you a lot to figure things out.

Also, don't be afraid to bridge your perfboard contacts to make tracings. This might be a pain for longer stretches, so you can still use a wire, but just fine for shorter runs and helps avoid weaving wires over your components or the pads you need to get to for your crucial/longer wiring. (I'm not assuming that you already do it, but I hope whoever taught you how to do electronics also taught you this "trick".)

If you have PCB software for layouts, you might be able to take the file to your local maker space to make a legit custom board. (If you don't know where the nearest maker space is, there are online maps to research them.) Some of them have the capability to build PCBs using CNC machines, laser cutters, and other techniques to even make them near professional quality. Quite often, you'll find other hobby level or, possibly, professional level electronics people that can help you even further.

As far as the actual professional services go, several of them can take a file online, then simply ship you the board. Some can even pre-populate the board for you. I was going to suggest Seeed Studio, but it looks like their min quantity for most PCB orders is 5.

You say making your own board is out of the question, but CNC machines that have accuracy good enough to make PCBs can be as small as about 12" cubed. They can cut the traces as well as the holes, then you don't even need the smelly acids. I've seen them on Amazon and eBay for less than $500. If you don't care too much about tiny traces, even a less than $300 CNC machine will work. Noise might be a factor, though, since they can be about as noisy as a drill, Dremel, or other small rotary tool. Some of them even use a Dremel as the cutting head.

Depending on the software that comes with the CNC machine. you might be able to use your layout file directly in the CNC machine. Depending on your layout software, you should still be able to at least export the file into something the CNC machine can use.