ideally on a 2 layer pcb you would have 1 side entirely ground and run everything else on the other side. In practice unless you are running micro wave applications you do not need to be that strict on having an unbroken ground.
If you are working in through hole components(something I try to never do because they take to long to assemble and make your boards big) then a solder mask is not needed. If work with surface mount components then solder masks are often esential.
A few helpful guidelines to 2 layer boards
1) make back of board ground where ever possible and run as much as possible on top side.
*for through hole components and no solder mask you are better off to have your ground plane on top and your traces on the bottom since it makes soldering easier.
2) Keep all components on the top side when ever possible. If using surface mount components try to only place bypass caps and pull up resisters on the back. This will save you on assembly costs if you ever plan to get assembled by third party.
3) when you must run only low frequency traces on the side of the ground plane. Keep them as short as possible and never cross a high frequency trace on the other side.
4) Once your board design is done check your return current paths. Ideally it will be able to follow directly under the trace on the ground plane but if you have run any traces on that side then it will deviate to get around those traces. try to minimize this deviation distance as the farther it goes out of its way the more EMI there will be. use vias and traces on the top side to make bridges, rewrote traces to shorten this distance do what ever you must.
*Don't sweet this to much unless you need to get your boards certified.
Well, my current board is small enough to fit everything on one side. It is a very simple design. But you guys are right about putting ground only on one side....it would be nearly impossible to make a board that didn't have its wires intersect somewhere...
....it would be nearly impossible to make a board that didn't have its wires intersect somewhere...
True. But don't forget, you can also use jumper wires if you find you've traced yourself into a conundrum. A wire or two here and there won't be too bad, unless you're dealing with finicky higher frequency circuits, that is. Also, you can repair some oopsies by using an Exacto knife and soldering wires to the severed traces.
True. But don't forget, you can also use jumper wires if you find you've traced yourself into a conundrum. A wire or two here and there won't be too bad, unless you're dealing with finicky higher frequency circuits, that is. Also, you can repair some oopsies by using an Exacto knife and soldering wires to the severed traces.
Or use existing vias (don't cover the vias with soldermask). That has saved a couple protos in my time.
....Please let me know if something is out of place!!!
Hi Rav,
Although I'm totally unfamiliar with the Picaxe, there are a couple minor things that come to mind.
First, you should always try to round out the corners of your traces so they do not form 90 degree turns. Also, because you seem to have plenty of room, keep your traces away from the edges of the board - it's just a safety precaution to make sure the traces aren't so easily scratched or touch something near the edge or get accidently trimmed down when the board is made.
Personally, I would rather have the components on the top of the board and most of the traces on the bottom, if that works out for you.
How will this board be mounted to whatever? Would you like to use standoffs? If so, you might want to add some stand off screw holes.
As for pin 19 on the picaxe, are you sure it's okay to just leave it dangling in space? Are you sure it doesn't need to be grounded or something?
Are you certain that the sips you are going to buy will actually fit in the spaces provided on the pcb? If the sips are physically too wide, you will be in a world of pain. When in doubt, space them out.
You can use the text tool to label components, etc. so the label will show up in the same copper as the trace material. It's a cheap way to get around not using silk screen when you just want to remind yourself of how, for example, a cap needs to be oriented, etc.
Be sure to read the tips that expressPCB provides on their website: it's especially important when your traces get close together and you start making ground planes, etc. http://www.expresspcb.com/ExpressPCBHtm/Tips.htm
As said, don't use right-angles, put two 45-degree angles instead. Also, aesthetically, you should try to keep your traces as vertical and horizontal as possible (and 45s are OK). You have some traces going at weird angles.
You don't have any spot for regulators (why not have the regulators on your board?). It appears your power input holes are only 0.029". Seems like you might want those a little larger.
It's always a good idea to put in copper pours (ExpressPCB calls it "filled plane") for ground, and V+ power.
Wow, thanks guys...The Picaxe doesn't need to have pins connected to anything(If you are not using them). The 20x2 series has a wide operating voltage range so i didn't include a regulator...Uh about mounting....I didn't really think of that. I hope the SIP's will be in the same shape as a female header...What is a copper pour? Also, Bob. Why is the whole background either green or red? IS that going to be filled entirely? Is that what is called a "Plane"? Thanks again for the help....It really means a lot
Yeah, most PCB software will call it copper pour, but Express PCB called it a filled plane. That entire area will be filled in with copper. I connected the top pour to your positive side of power, the bottom pour is connected to the negative. I left in the traces, but you don't need them (make sure the pins/pads are correctly connected to the pours). But the pours will act as a shield for electrical interference and vastly reduce the resistance between connections.
Comments
If you are working in through hole components(something I try to never do because they take to long to assemble and make your boards big) then a solder mask is not needed. If work with surface mount components then solder masks are often esential.
A few helpful guidelines to 2 layer boards
1) make back of board ground where ever possible and run as much as possible on top side.
*for through hole components and no solder mask you are better off to have your ground plane on top and your traces on the bottom since it makes soldering easier.
2) Keep all components on the top side when ever possible. If using surface mount components try to only place bypass caps and pull up resisters on the back. This will save you on assembly costs if you ever plan to get assembled by third party.
3) when you must run only low frequency traces on the side of the ground plane. Keep them as short as possible and never cross a high frequency trace on the other side.
4) Once your board design is done check your return current paths. Ideally it will be able to follow directly under the trace on the ground plane but if you have run any traces on that side then it will deviate to get around those traces. try to minimize this deviation distance as the farther it goes out of its way the more EMI there will be. use vias and traces on the top side to make bridges, rewrote traces to shorten this distance do what ever you must.
*Don't sweet this to much unless you need to get your boards certified.
True. But don't forget, you can also use jumper wires if you find you've traced yourself into a conundrum. A wire or two here and there won't be too bad, unless you're dealing with finicky higher frequency circuits, that is. Also, you can repair some oopsies by using an Exacto knife and soldering wires to the severed traces.
Hi Rav,
Although I'm totally unfamiliar with the Picaxe, there are a couple minor things that come to mind.
First, you should always try to round out the corners of your traces so they do not form 90 degree turns. Also, because you seem to have plenty of room, keep your traces away from the edges of the board - it's just a safety precaution to make sure the traces aren't so easily scratched or touch something near the edge or get accidently trimmed down when the board is made.
Personally, I would rather have the components on the top of the board and most of the traces on the bottom, if that works out for you.
How will this board be mounted to whatever? Would you like to use standoffs? If so, you might want to add some stand off screw holes.
As for pin 19 on the picaxe, are you sure it's okay to just leave it dangling in space? Are you sure it doesn't need to be grounded or something?
Are you certain that the sips you are going to buy will actually fit in the spaces provided on the pcb? If the sips are physically too wide, you will be in a world of pain. When in doubt, space them out.
You can use the text tool to label components, etc. so the label will show up in the same copper as the trace material. It's a cheap way to get around not using silk screen when you just want to remind yourself of how, for example, a cap needs to be oriented, etc.
Be sure to read the tips that expressPCB provides on their website: it's especially important when your traces get close together and you start making ground planes, etc. http://www.expresspcb.com/ExpressPCBHtm/Tips.htm
Hope that helps,
You don't have any spot for regulators (why not have the regulators on your board?). It appears your power input holes are only 0.029". Seems like you might want those a little larger.
It's always a good idea to put in copper pours (ExpressPCB calls it "filled plane") for ground, and V+ power.
Check out the attached file.