PCB design: Is silkscreen on ground plane okay?

A

Andy C

Guest
Hi all,

I'm doing my first PCB design. I'm an EE, but I am not familiar with many
of the practical aspects of PCB fab. I have IPC-2221 and a couple of other
documents like it, and have done some searches, but so far I haven't found
an explicit answer to this question.

I have a two-layer PCB for which the bottom layer is devoted to signal
traces and the top to ground plane, with a few signal traces on top. I'd
like to have a silkscreen layer to help with stuffing the board, but I'm
not sure if it's kosher to have a silkscreen layer on top of a ground
plane. Is this okay, or do board houses frown on this?

Thanks in advance,
Andy
 
In article <151k5986jziby$.pz0em3qptqv3.dlg@40tude.net>,
none@none.invalid says...
Hi all,

I'm doing my first PCB design. I'm an EE, but I am not familiar with many
of the practical aspects of PCB fab. I have IPC-2221 and a couple of other
documents like it, and have done some searches, but so far I haven't found
an explicit answer to this question.

I have a two-layer PCB for which the bottom layer is devoted to signal
traces and the top to ground plane, with a few signal traces on top. I'd
like to have a silkscreen layer to help with stuffing the board, but I'm
not sure if it's kosher to have a silkscreen layer on top of a ground
plane. Is this okay, or do board houses frown on this?

Thanks in advance,
Andy

I don't see why it would be any different from any other silkscreen job.
Click to expand...
Hell, it is probably quite a bit smoother than the surface of most
boards they have to screen.


Jim
 
I'm doing my first PCB design. I'm an EE, but I am not familiar with many
of the practical aspects of PCB fab. I have IPC-2221 and a couple of other
documents like it, and have done some searches, but so far I haven't found
an explicit answer to this question.

I have a two-layer PCB for which the bottom layer is devoted to signal
traces and the top to ground plane, with a few signal traces on top. I'd
like to have a silkscreen layer to help with stuffing the board, but I'm
not sure if it's kosher to have a silkscreen layer on top of a ground
plane. Is this okay, or do board houses frown on this?
Click to expand...
Is this a fancy/expensive board? (microwaves) If so, then
ask your board house, hire a consultant, or ask your colleagues.

If it's a low cost board, then I wouldn't expect any problems.
(I've done it.) If there would be a problem, the board house
should mention it on their web page or design guide.

--
These are my opinions, not necessarily my employer's. I hate spam.
 
I have a two-layer PCB for which the bottom layer is devoted to signal
traces and the top to ground plane, with a few signal traces on top.
Click to expand...
That brings up an interesting point. Assuming you are working on
a 2 layer board and one of them is a ground plane, how do you decide
if the ground plane goes on top or the bottom? I'm also assuming
that most of the parts go on the top.

My first reaction was to put the ground plane on the bottom so the
pads from the chips on top don't cut holes in the ground plane.

Signals that are easy to route won't need any vias and/or won't
cut up the plane as much.


--
These are my opinions, not necessarily my employer's. I hate spam.
 
On Sat, 24 Feb 2007 14:09:53 -0600, Hal Murray wrote:
That brings up an interesting point. Assuming you are working on
a 2 layer board and one of them is a ground plane, how do you decide
if the ground plane goes on top or the bottom? I'm also assuming
that most of the parts go on the top.
Click to expand...
This is a +/- 120 Volt DC voltage regulator taking about +/- 130 Volts DC
in. The board has radial-lead electrolytics on the top that have these
voltages on their non-grounded pins. If the main traces were on top, the
radial-lead electrolytics could end up resting on these high-voltage
traces. Though it may not be a problem in practice, the thought of this
made me paranoid. There doesn't seem to be any insulation spec that I can
find for the top side of the radial-lead electrolytics. So I thought it
best for safety reasons to not allow the bodies of these parts to rest on
high-voltage traces on the top of the board. Perhaps I'm overreacting, but
let's just say I have "respect" for high voltages.

My first reaction was to put the ground plane on the bottom so the
pads from the chips on top don't cut holes in the ground plane.

Signals that are easy to route won't need any vias and/or won't
cut up the plane as much.
Click to expand...
This being a DIY project, all my parts are through-hole types, so they'll
have pads on top and bottom. But I agree - with lots of surface-mount
parts, putting the ground plane on the bottom would be much better.

Andy
 
On Sat, 24 Feb 2007 14:04:38 -0600, Hal Murray wrote:

Is this a fancy/expensive board? (microwaves) If so, then
ask your board house, hire a consultant, or ask your colleagues.
Click to expand...
This is a DIY effort, so I'm in this by myself. It's not a microwave board
or anything terribly exotic. But there are some voltages over 100 V
involved - see my other reply.

If it's a low cost board, then I wouldn't expect any problems.
(I've done it.) If there would be a problem, the board house
should mention it on their web page or design guide.
Click to expand...
Thanks. I will check the web pages of the board house.

Andy
 
Oops - had to fix the default setting of my newsreader :).

Andy
 
On Sat, 24 Feb 2007 14:04:58 -0500, James Beck wrote:

I don't see why it would be any different from any other silkscreen job.
Hell, it is probably quite a bit smoother than the surface of most
boards they have to screen.
Click to expand...
Thanks!

Andy
 
On Sat, 24 Feb 2007 19:00:38 GMT, Andy C <none@none.invalid> wrote:

Hi all,

I'm doing my first PCB design. I'm an EE, but I am not familiar with many
of the practical aspects of PCB fab. I have IPC-2221 and a couple of other
documents like it, and have done some searches, but so far I haven't found
an explicit answer to this question.

I have a two-layer PCB for which the bottom layer is devoted to signal
traces and the top to ground plane, with a few signal traces on top. I'd
like to have a silkscreen layer to help with stuffing the board, but I'm
not sure if it's kosher to have a silkscreen layer on top of a ground
plane. Is this okay, or do board houses frown on this?

Thanks in advance,
Andy
Click to expand...
No problem doing this. It prints nicer since you'll have very few
traces on top.
 
Andy C wrote:
Hi all,

I'm doing my first PCB design. I'm an EE, but I am not familiar with many
of the practical aspects of PCB fab. I have IPC-2221 and a couple of other
documents like it, and have done some searches, but so far I haven't found
an explicit answer to this question.

I have a two-layer PCB for which the bottom layer is devoted to signal
traces and the top to ground plane, with a few signal traces on top. I'd
like to have a silkscreen layer to help with stuffing the board, but I'm
not sure if it's kosher to have a silkscreen layer on top of a ground
plane. Is this okay, or do board houses frown on this?

Thanks in advance,
Andy
Click to expand...
My rule is that there *will* be silk on each surface components are
loaded on.

Now, it is often the case that _all_ the silk information can not be
placed (on dense designs) but at least some information should be on the
silk for each loaded layer.

Cheers

PeteS
 
No problem putting silkscreen on copper.
Just keep it well away from any pads that are to be soldered
Cheers


Andy C wrote:
Hi all,

I'm doing my first PCB design. I'm an EE, but I am not familiar with many
of the practical aspects of PCB fab. I have IPC-2221 and a couple of other
documents like it, and have done some searches, but so far I haven't found
an explicit answer to this question.

I have a two-layer PCB for which the bottom layer is devoted to signal
traces and the top to ground plane, with a few signal traces on top. I'd
like to have a silkscreen layer to help with stuffing the board, but I'm
not sure if it's kosher to have a silkscreen layer on top of a ground
plane. Is this okay, or do board houses frown on this?

Thanks in advance,
Andy
Click to expand...
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top