DIY Etching pre-alpha

[comrade904]

Following some guides I found on the internet I am going to try to Etch a board or two and see what happens, or if it would be reasonable. I might make a guide specific to DIYEFI etching. I just have two questions that would help if I had the answer to.

1. From the looks of things, no components are soldered on the back of the board even though the board is etched on both sides. Is that correct?

2. Is there a list of components available somewhere? If not I'll just try to make my own list from the schematics.

[Fred]

Hold fire a bit longer man :-)

I'll most likely be getting some work done this weekend on pin allocations etc. Hopefully after that we can move forward on making the design more final and less of a guess.

I wouldn't etch it just yet.

Jared can answer the list question, usually called BOM, not sure what is included/available yet. It's not intended to be built just yet though, so no public/html list yet.

Jared can answer 1) too :-)

Fred.

[jharvey]

Following some guides I found on the internet I am going to try to Etch a board or two and see what happens, or if it would be reasonable. I might make a guide specific to DIYEFI etching. I just have two questions that would help if I had the answer to.

I like the enthusiasm, but it's not ready yet. The wires are missing that go from the CPU to the actual circuits. I'm waiting for Fred to iron the pin out a bit more. A huge undertaking for this would be drilling the holes. I recommend you don't try it unless you have a CNC drill. I seem to recall it's about 400 holes of varying sizes. I tried to make it user friendly for folks that want to etch their own, but still it's a lot of work. Components are soldered to both sides.

1. From the looks of things, no components are soldered on the back of the board even though the board is etched on both sides. Is that correct?

Some parts are SMT and require soldering to the "component" side. There are no SMT parts on the "copper" side, however there are VIA that required connections on both sides.

2. Is there a list of components available somewhere? If not I'll just try to make my own list from the schematics.

There is an incomplete list, I haven't finished populating it with vendor information, but the major fields have been populated. Like resistor % and wattage.

In the released zip files there is a file called freeEMS_1.lst it is the BOM produced by KICAD. Which is based on the fields I've been populating.

[comrade904]

Bummer, I got the blank transparencies in hand and I'm standing next to a laser printer...

I'm not too worried about drilling, I intend to make a second mask for the holes and I think my hardware store has a "drill-press like" attachment for my Dremel. Combined with a few tiny carbide bits for drilling copper, and some plastic vises to keep everything together and it should have a chance to come out functional. I think if it can't be done with this, then it probably can't be done at home. That said, we won't know until some one tries it.

I am definitely not scared by soldering, I've been modifying and repairing Xboxs, and 360's for a while. 360's are a terrible pain cause the traces are easily 5 times closer to together than the FreeEMS schematic shows IIRC and the boards are epoxy dipped so traces aren't normally accessible.

If I can fight that... I can do any "consumer level" diy electronics project you can throw at me.

I just can't wait for the groupbuy, to get my hands on some real meaty electronics project. And to make some turbo 200cc four-strokes.

I'd like to throw out there, I've been teaching myself as much as I can about circuit design, and anyone with a diy attitude might be interested in a pretty cool circuit simulator that can be found here-> http://www.falstad.com/circuit/

This is the only simulator I have used, mainly cause it is free, so I don't have anything to compare it to. But it seems pretty good to me. I've been using it to try to design some adjustable warning lights for resistance based automotive sensors.

Anyways I gotta go, Have a nice day all!

[jharvey]

For circuit sim, check out QUCS.

About the board, I guess I could toss in those traces based on the data sheet. That would get you a verision you can etch. I may move some of the AN's around, but other than that, it should be a good first step.

About the drilling, I'd recommend drill before etch if you can. Drilling after etching is more prone to tear up, and much less prone when have more copper around it.

Also sounds like your using one of those fancy etching kits. I don't recommend them. I know a guy that did an entire radio (not a simple radio, a real radio) by running glossy bubble jet paper through his wife's lazer printer. The lazer jet ink / plastic, stuck to the gosssy paper. Then he put that paper on the copper clad, and reheated it with an clothing iron. This caused the lazer jet ink to transfer from the glossy paper to the copper clad.

His end result was far better then I've been able to obtian with the kits. He held SMT tolerancing with out issue, where I've had troulbe keeping the right with the kit's I've used.

[davebmw]

I too have used the laser transfer method for years it works very well.
I have found that it is best to minimize the amount of copper you take of of the FR4 substrate as waiting for the large planes to etch off tends to allow time for undercutting or through cutting of the toner traces.
For very fine traces and complex PCB's with very close tracks I use the blue laser transfer sheets with slightly stronger etchant solution.
It has always worked a treat for me.

[Fred]

I have found that it is best to minimize the amount of copper you take of of the FR4 substrate as waiting for the large planes to etch off tends to allow time for undercutting or through cutting of the toner traces.

Quoted for truth. Good advice.

[jharvey]

I too have used the laser transfer method for years it works very well.

Curious, are you using transfer paper specifically intended for PCB, or glossy ink jet paper found at the dollar store? I'm curious which you have been using. I believe the glossy paper method that my friend uses, he learned about it from a guy in the UK. I'm just wondering how and if that technique is spreading.

I have found that it is best to minimize the amount of copper you take of of the FR4 substrate as waiting for the large planes to etch off tends to allow time for undercutting or through cutting of the toner traces.

True, true. Some other benefits of flooding your extra space include, stretching out how much acid your bath can etch, and keeping a plane that can be grounded, reducing noise.

I should figure out how to do that for the next release. I know it can be done, but haven't done it yet. Zones is what I think it's called in KICAD. I also have to admit some surprise that someone hasn't piped up about how I spelt timming vs timing on the schematic. All stuff to add to increase the quality of that layout.

[Delta]

This method is well known on the internet, lots of sites around that give full colour piccys of how to do the whole thing with the shiny paper in a laser printer

So yeah its been around a while. I've used this method successfully on a number of occasions even with quite small traces and spaces between traces. The big problem I find, is to do double sided boards and get it really really well aligned. I tend to find you have to increase trace width and spacing for double sided boards, especially if your going to be using ground planes. The other thing with this method is obviously since its not going to be plated through you have to solder in a rivet or spare diode leg or something into all the vias - which while not being a problem; just shits me.

[davebmw]

Well for normal single sided or less densely populated double sided PCB's with down to 17 thou track and 40 thou clearance using the A4 glossy ink-jet photo paper (140GSM) from Asda Smartprice (the cheapest i have found at 30 sheets for just under £3.00)
And a second hand HP LaserJet 4L with a £8.99 replacement toner cartridge!
the results are impressive. I made a simple connector adapter PCB for one of my contracts in work a couple of weeks ago. Even without copper filled areas I was able to etch the above spec with minimal toner etch through.
The photo below is that PCB prior to etching showing the toner traces that have been ironed onto the FR4 laminate.

I use fine etch crystals bought from RS 363-6573 i think they are potassium persulfate crystals, much cleaner and easier to use than ferric chloride. you can see the copper etching away as the solution remains clear only taking on the slightest blue tinge when used.
it also doesn't stain the kitchen sink so it keeps the wife happy!
This PCB has standard IDC 0.1" connector on it and you can run tracks in between the pins no problem. The finish on the edges of the tracks can be greatly improved by copper filling as much as possible so that you are not waiting for the last bit in the middle of the copper area to etch away. using this method there is really no reason why you cannot achieve tracks thin enough to connect to the 144 pin LQFP used on the bigger brother of our XDP512 chips.
I also use the blue thermal transfer sheets but usually only when i have to cover over through plated holes and vias.
Registration of the layers can be difficult if you don't print alignment marks on the transfer paper, a light box is very helpful too!
Contrary to belief through plating is not that difficult to achieve at home. you need an old fish tank or similar, a car battery charger or hefty PSU, some copper bars or old copper pipe, an aquarium air pump, and aquarium heater, sulfuric acid 35% and just a touch of hydrochloric acid,
Copper Sulfate Pentahydrate Crystals, copper gleam start up and de-ionised water, and some conductive ink from this site: www.thinktink.com, a colleague of mine has built one at home for plating various metal parts and PCB's we plated a PCB for a project at work the results were surprisingly good and very solder-able. there are some pretty obnoxious chemicals in there though so its one thats best done in a well ventilated shed with gloves, aprons, goggles and a tap with lots of water available!