[fyleow]

I bought the radio shack kit and I want to try to make my own PCB. Could anyone that has done it answer a few questions?

What type of paper works best? and what drill bit size do you use? The radio shack kit comes with a 1/16 drill bit but I think it's rather large. 1/32 would work better i think but I can't find it at Sears or Home Depot.

This is for the kevin gilmore amp btw.

 

[erix]

I've used the Shack's kit - it's not too bad. Here's a disjointed list of things I've noticed.

1. Read the directions - wear safety glasses.
2. Make sure your artwork is the copper side - not the top side. Easy to mess that up.
3. Cut the board to size.
4. Clean the board with the green scotchbrite pad.
5. Clean it really good.
6. Squeaky clean.

Here's where I divirge from the instructions - I like to lay a piece of paper on the board with the artwork and drill all my holes before etching. I use the tiny little ball bit for Dremels - just the right size and cuts clean.

7. Clean that board again and don't touch it!

Now I use Sharpie pens to draw my traces. I use the fat tip one to make the pad holes and the fine tip one for the traces. I have another fat tip for thicker traces. You can't make the lines to dark - let them dry and go over them again and again.

8. Get a a container large enough to hold the board and the acid solution - just enough to cover the top 1/4" or so.
9. Fill your kitchen sink with enough hot water to go over the level of the acid solution when you put the container in. Maybe you should do this when your wife/mother isn't home. Warm solution etches faster.
10. A little swirly agitating is fine just don't overdo it.

You just want the board in there long enough to take away the not-needed copper. The more copper there is to remove - the longer it takes. If you are making a one-sided board perhaps you should remove all the copper from that side first (before you start drilling and drawing).

I use tweezers to get the board out and rinse it in cold water - the water that's already in the sink helps dilute it. Don't pour acid down the drain - it'll be good for a few more boards!

Good luck!

ok,
erix

 

[antness]

Well, most holes on my Gilmore board are 0.029" which would be about a 0.75mm drill bit. Using a large drill bit will result in a LOT of broken traces on the board as well as cold solder joints, because the width of the traces on that board is generally less than 1/16"

BTW - have fun with the 250 holes

 

[BoyElroy]

Hi Fyleow,

I think that everyone's got their preferred method and it's up to you to figure out which works best for you. As for my 2 cents, I've tried several different methods; sharpie-on-copper, photographic paper, regular copy paper and transparencies. I have to say that the transparency method has worked best for me and has been a huge time saver compared to other approaches.

I've used HP and 3M transparencies and they all seem to work equally well. Just make sure that you get a fairly heavy weight sheet. A too flimsy sheet may distort or fail during the ironing transfer process. You can do a Google search and find many, many sites that detail different ways to make DIY PCB's or look at an earlier thread on the Gilmore amp in this forum where I've written about my preferred method in a little more detail.

Jeff Noxon has an excellent guide available here

You can also lay the two Gilmore circuit boards side by side on a single 6.25" x 4.5" Radio Shack copper plate and save space and some money too. To do this, just print out two transparencies; iron one on the plate, then register and iron the second one next to it. You can also do this in Photoshop or Paintshop Pro.

I can't agree more with Erix on the importance of sanding and cleaning the surface of the copper plate. Any gunk on the copper plate will actually protect the copper from the Ferric Chloride solution and prevent it from being etched away. Erix' advice on how to actually etch the board in the solution also makes a lot sense. You can try using a heat gun to warm the solution as well (and add salt to the solution if the reaction seems to be slowing down)

Also, while Antness is right on re: the high number of holes, if you use a .038"/ .039 " bit drill bit with a Dremel, you can drill the holes VERY quickly and its actually quite enjoyable drilling through the pcb plate like its a layer of refrigerated chocolate; bzzzzz...bzzzzz. (This was on the full sized pcb pattern, however, not the mini-PCB pattern)

American Science and Surplus sells a mini drill kit at their website here


I got myself a mini drill bit kit for my Dremel that contains about 20 mini-bits, sized from .039" on down to .0135". It cost about $15 US.

Best of luck!

 

[tangent]

'Course the question antness is hinting at is, "how bad do you really want to save $62?" That being the fee ExpressPCB will charge for a set of 3 prototype boards. (3.8" by 2.5") For your money, you get boards with straight traces with exactly the right sizes, dual-layer boards (try doing that with hand etching!), and plated through holes. If your design is dense or complex at all, I wouldn't do it any other way.

 

[BoyElroy]

I'd agree with Tangent to a certain extent; if this were the only time you were ever going to make a pcb and you don't already own a drill, then it would be cheaper to buy a pre-fabbed board.

On the other hand, if you want to make both the Gilmore power supply board as well as the Gilmore amp pcb, I think the cost savings of buying pre-made pcb's diminishes a bit, if not disappears outright. Moreover, once the DIY'er purchases the basic elements involved here; the Dremel drill and bits being the only major outlays, he can print out and make basically any circuit board that's been posted to the Headwize library. The printing resolution is actually quite remarkable.

On top of that, there's the extra satisfaction of looking at your amp and thinking, "Gee, I basically put this darn thing together from scratch!"

Using the transparency method, the Gilmore amp pcb can be printed out quite easily and, assuming the DIY'er already has a Dremel drill, the total cost for a DIY-printed dual board comes out to:

$3.99 for the copper plate
$3.99 for a reusable bottle of solution
$.50 for 2 sheets of transparency paper.

You can then print out the power supply pcb for an additional :

$3.99 for the copper plate
$.25 for the sheet of transparency

(my prices may be off by a couple of dollars or so...)

The total sum here for all the necessary pcb's (amp board plus power supply board) is about $15 US.

In addition to low cost, another advantage to printing your own pcb's is that you can modify the board to fit your tastes without ordering a whole new set of proto-boards. If you want to add another pair of capacitors or dual connectors, etc., all you have to do if modify the pattern in Photoshop and print out a new transparency.

In Fyleow's case, since the Gilmore amp pcb requires neither dual layers nor complex circuit paths, it should be a fairly straightforward process to print out and fabricate it at home.

(I should add that this applies only to the full sized Gimore amp pcb's. I have not made the mini-boards and so cannot comment on how well they lend themselves to DIY-printing. )

 

[antness]

actually, it's only half of $62 for a stereo amp board with silkscreen and solder mask like the META42 board.

 

[fyleow]

Thanks for the replies everyone. I do own a drill I just don't own the drill bits, that shouldn't be too expensive or hard to get. I have a laser printer at home so I have the nessecary tools.

I am going to be making the power supply and the board design that Kevin Gilmore originally supplied with his amp article. The only problem I see now is the power supply was designed for the Radio shack board but the case that I have is smaller than that. It's only 4 inches while the PSU is 4.5 inches.

I'll keep you updated.

 

[BoyElroy]

Hi Antness,

To begin with, fantastic job on your amp! It looks pretty spectacular and I agree wholeheartedly with your endorsement of the Gilmore design. I notice that you used two ceramic caps in place of poly caps in your power supply. Do the ceramic caps sound better and what value are you using?

Getting back to the thread at hand, $32 for a finished stereo board is not that bad. At that price, I'd be torn on whether to buy the finished pcb or invest in a DIY pcb set up. I guess it would all depend on whether the person expected to make any additional boards in the future...

 

[antness]

I used the ceramic caps because poly caps caused the opamp to oscillate. the ultra-fast $7 each caps that kevin used may not cause this, but my WIMA caps sure did. no capacitor also resulted in some oscillation. the ceramic cap stopped it completely

 

[BoyElroy]

Antness:

That's good to know. I guess its time to break out the old soldering gun and do some modifying.


Fyleow:

Hmmnnn...I'm curious to know how you'll squeeze it in. Perhaps the easiest solution would be to just get a bigger case (!)

 

[fyleow]

I've already purchased the case from Mouser so it's too late to get a bigger one now. Worst case is I'll just try to modify yours to get it to fit somehow

 

[BoyElroy]

Hi Fyleow,

I'll try re-drawing the power supply pcb to fit inside your 4" wide case. I should have it done sometime this weekend (wife permitting, of course...)

 

[fyleow]

Acutally BoyElroy I think I might just purchase the boards from Antness. I don't really plan to make anymore PCBs in the future so I think the investment into drill bits and solution etc would be wasted. I really really appreciate your help (and everyone elses) though. Thanks for the offer too!

 

[eric343]

Well, Olimex does Eurocard-sized PCBs for $26, and they do solder mask AND silkscreen included in that price...

You just have to learn to use EAGLE. (www.cadsoft.de)

It's not that hard, I'd recommend reading and doing the tutorial and keeping the manual (downloadable from the site, NOT included).

Also, the freeware version of Eagle limits you to a half-Eurocard PCB, so just design one channel in it and have Olimex panelize it.