PCB *style* question

[bwanasonic]

I am looking to take advantage of the Express PCB pricing on *miniboards* (3 * 3.8 X 2.5  boards for $59), so I have been attempting the jump from perf to PCB layout. One question I have is the difference between what I call the *more copper the better* style:



and the more basic traces approach:




Any advice appreciated.
Kerry M

[vdm]

it's strange... sometimes you'll see thin traces, and i think this is too reduce the tiny capacitance between the traces - you often hear people talking of tiny capacitance between pcb traces - this is what some say makes pcb worse for tube amps than point to point.
but then you can look at the tonepad layouts, and most them have big block parts... especially for grounds and such..

so all in all, with an effects pedal i dont think it really matters... i doubt it will greatly affect the end product - just choose what you prefer to work with and solder on.

trent

[RobB]

If that's $20 US each then I think the price is too expensive.  If you have access to a bench drill which will take very small drill bits then I suggest you make them your self for a fraction of the price.  

I've just finished making a board using the iron on photo copied transparency method.  Very satisfied with the result.  I even ironed on the parts placement text onto the component side.  

Counting the amoint of ammonium persulphate, copper board and the cost of the transparency I'm sure it didn't cost me any more than $3.00 Aus.  

If you can find the time, then do it your self. :wink:

[Ansil]

futurlec will do them cheaper than that

[Marcos - Munky]

This don't matter when you build effects. But the "less copper" one is better in my opinion, because there's less copper (duh ) and there's less chance to create solder bridges between the traces. The "more copper" one is easier to create solder bridges.

[sirkut]

Take a look at your two pcb pics.  The second one, where the letter A is for that single pad. Now look at the first pic. Which is correct? one is joined with the others close by whereas the second pic it's isolated. Just wanted to point that out.

[smoguzbenjamin]

Hmmm you're right. I'd say do the mroe copper one. Less etching time.

[Nasse]

Maybe there is some good compromise found. In the few designs I have done for myself I have tried to avoid very thin traces, very small pads and especially traces between ic legs. When looking my results with magnifying glass I can see that homemade methods dont always produce professional results. "More copper" saves etchant for sure.

That capacitance and inductance thing is a mystery and hit-and-miss thing for me I quess. But maybe you can do audio freq designs without knowing much about it. Avoiding ground loops and crosstalk may be the problem you meet before. What is confusing "less copper" example or more space between traces does not always mean less capasitance or inductance.

Some commercial stuff (like some cheap building kits I have purchased) is done quickly just with autorouter, resulting hum and other problems. Designing good pcbs is not easy, thats why we continue to see mistakes and problems in some projects. Everybody who does want to take this challenge of making good and working ones, is a hero.

[bwanasonic]

Take a look at your two pcb pics.  The second one, where the letter A is for that single pad. Now look at the first pic. Which is correct? one is joined with the others close by whereas the second pic it's isolated. Just wanted to point that out.

Thanks for paying attention! The skinny trace one was just for illustration purposes.  

Kerry M

[bwanasonic]

If that's $20 US each then I think the price is too expensive.  If you have access to a bench drill which will take very small drill bits then I suggest you make them your self for a fraction of the price.  

I plan on doing 4X up on each board, so I'll be getting 12 circuits for $59. Aside from the dreaded drilling headaches, I live in a small apt. with my wife,  two kids and a cat, so dealing with trays of nasty chemicals is just not worth it for me. I dealt with trays of nasty chemicals for years as a living, so I'm kind of done with that.

Kerry M

[Fret Wire]

What drives me nuts is the two different methods in laying out pcb pads for off-board connections. Some commercial and DIY pcb's have pads on the pcb for almost all the off board connections: all pots and their lugs, and jack tips, for example. Other commercial and DIY pcb's have the minimum number of pads, and you jumper to most of the off board components. Obviously, a pad per connection eats up a lot of board space. especially since most of the pads are usually on one end of the board.

But is one quieter or more efficient than the other? It be nice if there was a simple tutorial on the layout of that alone.

12 boards for $59. Can't beat 5 bucks a board for your own personal layout.

[Peter Snowberg]

I've been getting mini-boards for a few years now and a love them. They're cheaper by a long shot once you count the time, chemicals, and capabilities. I also love plated throughs and small feature sizes so I'm biased. (I like SSOP chips and 0603 resistors... no chance I'll ever hand-etch a board that uses those!)

Go with the big copper version. Parasitic capacitance is a non-issue here and since the process they use is tin-over-copper the longevity is also great, but I think larger traces are generally better for making stronger boards if you're ever going to desolder something.

Since they're double sided, consider running a ground plane over the entire back of the board. You can never have ground traces that are too big.

Take care,
-Peter

[blabj]

i personally like big traces because theres more room for error but if you do make smaller traces then you can in theory make the board smaller... although how much it would reduce it is another question...   :?

[smoguzbenjamin]

It probably won't make much difference. Plus, a 1590B box isn't going to get smaller because the PCB's a little thinner

[nooneknows]

I prefer quite large traces and large pads but keeping some space between them.
I don't think parassite capacitance is such a big problem with this type of  BF circuits and I haven't seen any distorsion box that we could consider audiophile proof...
large traces are mechanical stronger and large pads let a number of solder/desolder actions without damages.

[The Tone God]

I'm a fan of the "remove only what you don't need" style then the "keep only what you need" style for board designs. There are good and bad points about using large traces. Some of which follows.

Good:

- More surface area means easier to solder (if you don't do SLI) most of the time.

- With the extra surface area there is more strength between the copper and board material. Also means stronger off board connections like to wires.

- If you are etching your own boards it reduces the amount of copper you have to etch off reducing etching time and extending etchant life.

Bad:

- It can be harder in some cases to solder if there are nearby traces. You can get solder arcs.

- With high gain circuits in particular there is an increased chance of having crosstalk between traces. Think of it as almost like bundling all the wires together.

- You may need to stick a ground plane and isolation traces between offending trace runs. More work.

At this point its not as much the size of the traces but the space between traces. My usual advice is make a board or two yourself to see how the board sounds before you get a batch made. That way your not wasting your money.

If you getting the boards made for you then maybe stick with medium size traces like half way between what you have there.

Andrew

[ErikMiller]

Some time ago, some folks asked me how I managed to keep the Crucible Fuzz from self-oscillating when both knobs are turned up (seeing as it is a FF-type circuit with high gain silicon transistors).

PCB traces are not perfect conductors. They have their own resistance, capacitance and, people seem to forget, inductance.

I avoid the capacitance and inductance by keeping them away from each other.

Dunlop's Hendrix Fuzz oscillated all over the place, and its PCB used the big blocky traces with little space between them method.

I designed my first printed circuit 21 years ago, and way back then, I learned to keep the traces just wide enough for manufacturability and power handling, and far enough apart that they don't interfere with each other.

That goes for analog, digital, and RF, all of which I've done.

Here's one thing: having the trace neck down from the pad helps keep the solder AT the pad, where it's needed, rather then flowing up the trace.

I'm not saying my way is the only right way, mind you, but if you open up professionally-made devices and check out the PCB's, you'll see plenty of examples like the second figure, and not too many like the first one. The first one looks like a power supply design.

[bwanasonic]

Thanks for all the tips!

Kerry M

[spongebob]

Chapter 17 (Circuit Board Layout Techniques) of Opamps For Everyone might also be worth a read...

[Branimir]

cheers!

i've been using EasyPC for drawing pcb's, it doesn't have any autorouter thingy or anything, but it's quite easy to use and has a large library of components (of course they're not labeled as TL072 and such, just sizes of the cases), i haven't been much into diy pcb lately, most of the projects i've done are on pcb's already made by someone else (tonepad for example), or manually drawn on paper and then on pcb (like my ax84 project)...

the reason i don't use easypc no more is that it's dated 1989 and still is a great program, but it doesn't run in winxp (actually i doesn't run in any windows), and of course i can forget about usb printer to use it to print from the program...

i've tried other pcb drawing software and been brought down by a fact that all of them that i've tried have wierd component library or there's no idea how the board is actually big, it doesn't have an export function to some "normal" format (like jpg or something) and not to mention the printing of it..
it use to take me 20 minutes to draw a, i don't know son of screamer or something and every time i run these new programs it's like "what does this wierd function do? why do i have this this this and that and still i can't find what size is all this? how can i export this to something so i can make a pdf file? what is excatly .eoq or .i8u or .bb1 (i'm spazing off now heh) for an export file?"


heh, so please, is there any intuitive pcb drawing software to use that doesn't use millions of gb of hard drive, that has measures, that doesn't have that router stuff and has a library of 4 and 8 pin ic's, resistors and capacitors, can export to something "normal" and it prints from the program as it should appear on board

heh thanks