getting ready to make my PCB

[jrz126]

Ok guys,

I'm making some progress in making the PCB for my LEDs. I'm getting ready to put in my order, and I've got some questions (I'll underline them). I was planning on going with Electronics xpress, but they are slow to respond. So I think I'm gonna switch to Digikey.
I dont think Digikey sells any sort of etchant chemicals though. So I might just have to go with ferric chloride from radio shack. (it's at a good price and I dont have to pay shipping on it)
I've read and have been told to use Ammonium persulfate. Is there a major advangtage to using this? Also, does this chemical have other uses that would make it pretty easy to pick up locally?


Here's what I plan to order:
3 - 6"x9" double sided boards (1/16 thickness). for $6.57 each.

200 - 82 ohm resistors (for current limiting, I only need 62, but I'm sure I'll use the others for other LED projects) $4.72 total for these

4' of clear and 4' of black 1/8" heatshrink tubing. $0.88 each.
Are there any other tools, or anything else that I should buy that would help in making the pcb?

I might be able to have my dad take the board to work and drill it on a $150k cnc machine. If I cant however, I'll have to use my drill press and drill the holes by hand. There is a local Harbor Freight store, which should have the drill bits for a decent price.

For the VIA's in the board, is it worth it to try to find those little insert things, or should I just try to slop some solder inside there? I'm gonna have the some pieces of leads left over from the LED's when I solder the wire to them, so I think I'll try sticking these in the VIA's and putting solder on them and trim them as necessary. to try to get them as flush as possible. any suggestions?

Oh yeah, I dont have any sort of desoldering tool (I have one of those spring loaded suction things, but it doesnt work too great) which type is the best?

Hope you guys can help me out.

[/u]

 

[evandude]

try electronics goldmine for the PCB's. the boards they sell are thin (about half as thick as regular ones) but REALLY cheap (about 3 cents per square inch)

you might try looking for sodium persulphate as an etching chemical. if you plan to use the toner transfer method, the ammonium persulfate is said to eat the toner right off, so you couldnt' use that method, whereas the sodium persulphate is supposed to be OK. i got some, but haven't tried it yet. in the mean time, ferric chloride works alright, it's just messy because it stains everything it touches.

good luck finding the drill bits. they are wire drill bit sizes, which makes them a lot harder to find. you can use the dremel wire drill bit sets, although the bits will only last maybe 100 holes apiece. look for sets of repointed carbide PCB drill bits on ebay. for about 50 bucks i have a TON of bits - one assortment of a few each of most common sizes, and a set of 50 of one size. carbide bits will last nearly forever, until you break them, which in a decent drill press is not a real problem.

 

[Russlk]

Do you really need a 2 sided board? All my boards are single sided and where I need a crossover I use a wire jumper.

 

[gerty]

Jameco.com 1/4 watt resistors $.99 for a hundred . They have a pretty good assortment of other stuff also...

 

[Dean Huster]

I've used ammonium persulfate heated to around 110° for years with the toner transfer process with no problems whatsoever.

Kelvin Electronics has a lot of PCB etching supplies and they're cheap, but I think they sell only to schools. Might check there just in case.

Dean

 

[kentken]

You want to get sodium persulfate. It is a clear etch that turns blue after use. Very clean and easy to use.
It is said to be compatiable with etch resist pens, I use nail polish to fix the toner designs.

Kent

 

[jrz126]

Do you really need a 2 sided board? All my boards are single sided and where I need a crossover I use a wire jumper.

I've thought about making it single sided, but I think it might be too much trouble in laying it out. my dimensions of the board is 6.75x7.25, and I need:
8 shift register (20 pin dip)
8 drivers for the leds (18 pin dip)
4 40 pin headers (2 for shift resiter control 2 for led out)
64 1/8W resistors
8 bypass caps.
3 vregs
3 heatsinks
6 extra caps for the vregs (dont think I need them, but I'm gonna use em anyway just to be safe.)

I want this board to look good too, I dont want to have ugly jumper wires all over the place. and with the double sided, I wont have to worry about a bad connection on the board as much, so it will help debugging.

Kentken, so you are saying nail polish can be used instead of an etch resist pen? I was thinking about buying one, but my sister has a ton of nailpolish so I should be good.

Does the sodium persulfate need to be heated? My college has a pretty good EE lab, do you think they would carry the sodium persulfate, (or any chemicals for that matter)?

A thinner PCB would be easier to drill, but the boards from goldmine will be about 2.5 times thinner, how strong will this board be? I dont want to get halfway through making it and have it crack in half.

 

[Nigel Goodwin]

6 extra caps for the vregs (dont think I need them, but I'm gonna use em anyway just to be safe.)

It's essential to have two capacitors as close as possible to 78xx voltage regulators - it's unwise to leave them out, they 'may' work under some circumstances, but are likely to become unstable under some conditions.

 

[fat-tony]

My college has a pretty good EE lab, do you think they would carry the sodium persulfate, (or any chemicals for that matter)?

Are you in EE? At my college, they will make PCBs for EE students for free!

 

[plot]

My college has a pretty good EE lab, do you think they would carry the sodium persulfate, (or any chemicals for that matter)?

Are you in EE? At my college, they will make PCBs for EE students for free!

my college does too, we can't mass produce the things or anything like that though... for any project we do in school or out of school, they let us mill the PCB's.