Minimum slot size, Mouse bites, Arrggh!

[Winfield Hill]

How to choose minimum slot size on PCB layout,
All about mouse bites, hole size, spacing, etc.

Breakaway for 0.5 x 10.5-in board, no grooves.
After machine assembly, break off 1.7" end piece.


--
Thanks,
- Win

 

[John Larkin]

On 5 May 2019 13:40:37 -0700, Winfield Hill <hill@rowland.harvard.edu>
wrote:

How to choose minimum slot size on PCB layout,
All about mouse bites, hole size, spacing, etc.

Breakaway for 0.5 x 10.5-in board, no grooves.
After machine assembly, break off 1.7" end piece.

Sketch? I can't exactly envision what you want to do. Multiple small
breakaways from a long strip?


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Winfield Hill]

John Larkin wrote...

Sketch? I can't exactly envision what you want to do.

Forgot to add sketches to my answering post. Here's
the 10-parameter five sensor IC circuit-board section.
https://www.dropbox.com/s/zcrdts69d4189t8/TH-stick_five-sensor-ICs.PNG?dl=0

And here's the entire 10.5" long manufactured PCB.
https://www.dropbox.com/s/bfng1lx20q2fpza/TH-stick_full.PNG?dl=0

The right 8.8-inch portion sticks into the hive. The
left 1.7-inch section is broken off, and connected
with MOLEX 1.25-mm spacing, 0.12mm thick Premo-Flex,
past the beehive walls, to the sensor section.

One should not have to do two PCBs and two machine
assemblies, when one can work, to be separated later.



--
Thanks,
- Win

 

[Winfield Hill]

John Larkin wrote...

On 5 May 2019 13:40:37, Winfield Hill wrote:

How to choose minimum slot size on PCB layout,
All about mouse bites, hole size, spacing, etc.

Breakaway for 0.5 x 10.5-in board, no grooves.
After machine assembly, break off 1.7" end piece.

Sketch? I can't exactly envision what you want to
do. Multiple small breakaways from a long strip?

Yes, good. We have five sensor ICs on the 1.7-inch
end of a 8.8-inch long, 0.45-inch-wide TH-stick PCB.
The 10-parameter sensor PCB projects into the middle
of a bee-hive, near the queen. At the hive wall, a
thin flexible strip carries I2S signals + power past
the hive's wooden supers (frame sections). A second
1.7-inch PCB piece mates the strip to a 4-wire cable
to our 60-sensor bee-hive monitor (making a total of
70 sensors). The PCB sections are made and machine-
assembled as one, but need to be broken apart for use.


--
Thanks,
- Win

 

[John Larkin]

On 5 May 2019 18:22:40 -0700, Winfield Hill <hill@rowland.harvard.edu>
wrote:

John Larkin wrote...

Sketch? I can't exactly envision what you want to do.

Forgot to add sketches to my answering post. Here's
the 10-parameter five sensor IC circuit-board section.
https://www.dropbox.com/s/zcrdts69d4189t8/TH-stick_five-sensor-ICs.PNG?dl=0

And here's the entire 10.5" long manufactured PCB.
https://www.dropbox.com/s/bfng1lx20q2fpza/TH-stick_full.PNG?dl=0

The right 8.8-inch portion sticks into the hive. The
left 1.7-inch section is broken off, and connected
with MOLEX 1.25-mm spacing, 0.12mm thick Premo-Flex,
past the beehive walls, to the sensor section.

One should not have to do two PCBs and two machine
assemblies, when one can work, to be separated later.

If you want nice clean breaks, v-score is great. You could make a 2d
array.

It won't work for mouse-bite solder connections, but you don't seem to
have those.

You can snap the scores by hand, but we use this:

https://www.dropbox.com/s/3nmho4t77n3ucpa/Cutter_1.JPG?dl=0

(My production people love to buy toys.)





--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Tim Williams]

"Winfield Hill" <hill@rowland.harvard.edu> wrote in message
news:qanho502bvk@drn.newsguy.com...

How to choose minimum slot size on PCB layout,
All about mouse bites, hole size, spacing, etc.

Breakaway for 0.5 x 10.5-in board, no grooves.
After machine assembly, break off 1.7" end piece.

0. Don't. Let the fab panelize for you. They charge per board anyway, and
they get better utilization putting your boards anywhere on the panel. (If
these are production quantites, you'll probably want a full custom panel,
for many other reasons besides just PCB cost.)

1. 2mm width is the "everyone does this by default" size. They can rout at
maximum speed with 2mm end mills.

2. Most fabs will do slots down to 1.0, even 0.6mm. This is effective for
creepage between component pads, but takes more time -- it will be a cost
adder particularly for long routs.

3. Mouse bites are typically 0.5mm holes, closely spaced, positioned
tangential to (and inside) the board perimeter. This ensures that the
broken material tends not to stick out. It is rough, of course.

4. V-score is done in a straight line, and almost always completely across
the panel. (You can order partial v-score, but the tolerances on start/end
position are awful -- it's basically a hand operation.) It can be done over
routs, which gives the opportunity to make scored tabs -- they break off
cleaner than full score (which leaves a full edge rough), and much smoother
than mouse bites.

I'm fond of doing the latter -- a routed edge (often in profile, so it fits
nicely into place and has smooth edges), with scored tabs so it breaks away
smoothly.

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

 

[Winfield Hill]

Tim Williams wrote...

0. Don't. Let the fab panelize for you. They charge
per board anyway, and they get better utilization
putting your boards anywhere on the panel. (If these
are production quantites, you'll probably want a full
custom panel, for many other reasons besides just PCB
cost.)

1. 2mm width is the "everyone does this by default" size.
They can rout at maximum speed with 2mm end mills.

2. Most fabs will do slots down to 1.0, even 0.6mm.
This is effective for creepage between component pads,
but takes more time -- it will be a cost adder
particularly for long routs.

3. Mouse bites are typically 0.5mm holes, closely
spaced, positioned tangential to (and inside) the
board perimeter. This ensures that the broken material
tends not to stick out. It is rough, of course.

Thank you Tim! This is the exact information I needed,
and couldn't get from the PCB house (when it was closed).

4. V-score is done in a straight line, and almost always
completely across the panel. (You can order partial
v-score, but the tolerances on start/end position are
awful -- it's basically a hand operation.) It can be
done over routs, which gives the opportunity to make
scored tabs -- they break off cleaner than full score
(which leaves a full edge rough), and much smoother
than mouse bites.

I'm fond of doing the latter -- a routed edge (often
in profile, so it fits nicely into place and has
smooth edges), with scored tabs so it breaks away
smoothly.

I am a V-score fan, but the extra distances required
beyond my PCB section are troublesome. Long V-scores
(e.g., 10 inches) are hard to break, and using a brake
or other tool, puts machine assembled parts at risk.
What's more, I feel compelled to sand the broken edges.

V-score over routes, what? Cuts the trace, right?
Sounds super useful, but leaves me totally confused.
Hmm: rout, route?


--
Thanks,
- Win

 

[Clifford Heath]

On 6/5/19 3:18 pm, Tim Williams wrote:

"Winfield Hill" <hill@rowland.harvard.edu> wrote in message
news:qanho502bvk@drn.newsguy.com...
How to choose minimum slot size on PCB layout,
All about mouse bites, hole size, spacing, etc.

Breakaway for 0.5 x 10.5-in board, no grooves.
After machine assembly, break off 1.7" end piece.


0. Don't.  Let the fab panelize for you.  They charge per board anyway,
and they get better utilization putting your boards anywhere on the
panel.  (If these are production quantites, you'll probably want a full
custom panel, for many other reasons besides just PCB cost.)

1. 2mm width is the "everyone does this by default" size.  They can rout
at maximum speed with 2mm end mills.

2. Most fabs will do slots down to 1.0, even 0.6mm.  This is effective
for creepage between component pads, but takes more time -- it will be a
cost adder particularly for long routs.

3. Mouse bites are typically 0.5mm holes, closely spaced, positioned
tangential to (and inside) the board perimeter.  This ensures that the
broken material tends not to stick out.  It is rough, of course.

4. V-score is done in a straight line, and almost always completely
across the panel.  (You can order partial v-score, but the tolerances on
start/end position are awful -- it's basically a hand operation.)  It
can be done over routs, which gives the opportunity to make scored tabs
-- they break off cleaner than full score (which leaves a full edge
rough), and much smoother than mouse bites.

I'm fond of doing the latter -- a routed edge (often in profile, so it
fits nicely into place and has smooth edges), with scored tabs so it
breaks away smoothly.

Tim, I'm just designing a board just like this, that will snap full
panels into boards that then snap into a dozen small boards each.

How do the fabs like to receive Gerbers for this? Routing and V-scores
in separate layers/files? Or how? Can you share a setup you use to
create these Gerbers? (I'm using Kicad)

Clifford Heath

 

[Winfield Hill]

Tim Williams wrote...

3. Mouse bites are typically 0.5mm holes, closely spaced,

OK, how closely spaced? Much, much closer than my CAD
system's default minimum hole-to-hole spacing, I assume?


--
Thanks,
- Win

 

[Clifford Heath]

On 6/5/19 4:39 pm, Winfield Hill wrote:

Tim Williams wrote...

0. Don't. Let the fab panelize for you. They charge
per board anyway, and they get better utilization
putting your boards anywhere on the panel. (If these
are production quantites, you'll probably want a full
custom panel, for many other reasons besides just PCB
cost.)

1. 2mm width is the "everyone does this by default" size.
They can rout at maximum speed with 2mm end mills.

2. Most fabs will do slots down to 1.0, even 0.6mm.
This is effective for creepage between component pads,
but takes more time -- it will be a cost adder
particularly for long routs.

3. Mouse bites are typically 0.5mm holes, closely
spaced, positioned tangential to (and inside) the
board perimeter. This ensures that the broken material
tends not to stick out. It is rough, of course.

Thank you Tim! This is the exact information I needed,
and couldn't get from the PCB house (when it was closed).

4. V-score is done in a straight line, and almost always
completely across the panel. (You can order partial
v-score, but the tolerances on start/end position are
awful -- it's basically a hand operation.) It can be
done over routs, which gives the opportunity to make
scored tabs -- they break off cleaner than full score
(which leaves a full edge rough), and much smoother
than mouse bites.

I'm fond of doing the latter -- a routed edge (often
in profile, so it fits nicely into place and has
smooth edges), with scored tabs so it breaks away
smoothly.

I am a V-score fan, but the extra distances required
beyond my PCB section are troublesome. Long V-scores
(e.g., 10 inches) are hard to break, and using a brake
or other tool, puts machine assembled parts at risk.
What's more, I feel compelled to sand the broken edges.

V-score over routes, what? Cuts the trace, right?

I read that as V-score over routed slots. So you have a row of
through-routed slots, and you v-score the non-routed bits (tabs) so they
snap better. That sounds perfect for what I need (what I was asking
about FR2 the other day)

Clifford Heath.

 

[Tim Williams]

"Winfield Hill" <hill@rowland.harvard.edu> wrote in message
news:qaokrf0tsj@drn.newsguy.com...

I am a V-score fan, but the extra distances required
beyond my PCB section are troublesome. Long V-scores
(e.g., 10 inches) are hard to break, and using a brake
or other tool, puts machine assembled parts at risk.
What's more, I feel compelled to sand the broken edges.

Yeah, that's a good reason to, well -- what they do commercially is use a
dual-pizza-cutter contraption to more like wedge the boards apart, rather
than bend and break them. (You still want a good 100-200 mils clearance
around the board edge, where components are prohibited; they aren't always
careful about parts close nearby.) But otherwise, yeah, good reason to make
tabs.

V-score over routes, what? Cuts the trace, right?
Sounds super useful, but leaves me totally confused.
Hmm: rout, route?

Yeah, "rout". Regrettable that the same word (give or take spelling, if
that's even the correct spelling for this use actually..?) is used, within
the same subject, for two very different things. I'm sure you know an
English professor to gripe at about it. :^)

Regarding mousebites: probably like 20 mil holes, 10 mil web between holes
(so, 30 mil pitch). Shouldn't be prohibited by most tools or fabs.

They may well just see that you're putting in bites or tabs, and delete
yours and put in their own according to their own rules (give or take how
much effort they want to spend on it, and how much you want them to check?).

Such features are indicated on a mechanical or drill drawing. Just put down
some lines with arrows and a note describing what it is. So, point at one
edge of the board and say "V-SCORE WITH TABS" or the like. Put some notes
in regards to panelization on there, too (if you're doing the panel
yourself, then something to the effect of "PANELIZATION: BUILD AS SHOWN"
might clarify that).

Oh, incidentally, they may ask about thieving (unconnected copper pads,
added to open areas to improve copper balance, reducing warpage). You may
or may not want that on your board, but it's definitely fine on the rails.

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

 

[Jeroen Belleman]

Tim Williams wrote:

"Winfield Hill" <hill@rowland.harvard.edu> wrote in message
news:qaokrf0tsj@drn.newsguy.com...
I am a V-score fan, but the extra distances required
beyond my PCB section are troublesome. Long V-scores
(e.g., 10 inches) are hard to break, and using a brake
or other tool, puts machine assembled parts at risk.
What's more, I feel compelled to sand the broken edges.

Yeah, that's a good reason to, well -- what they do commercially is use
a dual-pizza-cutter contraption to more like wedge the boards apart,
rather than bend and break them. (You still want a good 100-200 mils
clearance around the board edge, where components are prohibited; they
aren't always careful about parts close nearby.) But otherwise, yeah,
good reason to make tabs.


V-score over routes, what? Cuts the trace, right?
Sounds super useful, but leaves me totally confused.
Hmm: rout, route?

Yeah, "rout". Regrettable that the same word (give or take spelling, if
that's even the correct spelling for this use actually..?) is used,
within the same subject, for two very different things. I'm sure you
know an English professor to gripe at about it. :^)

Aren't they two different words? To route, pronounced 'ROOt' and
meaning 'planning a path' and to rout, pronounced 'Rowt' meaning
'to dig up'?

Jeroen Belleman

 

[Martin Riddle]

On Mon, 6 May 2019 16:41:19 +1000, Clifford Heath <no.spam@please.net>
wrote:

On 6/5/19 3:18 pm, Tim Williams wrote:
"Winfield Hill" <hill@rowland.harvard.edu> wrote in message
news:qanho502bvk@drn.newsguy.com...
How to choose minimum slot size on PCB layout,
All about mouse bites, hole size, spacing, etc.

Breakaway for 0.5 x 10.5-in board, no grooves.
After machine assembly, break off 1.7" end piece.


0. Don't.  Let the fab panelize for you.  They charge per board anyway,
and they get better utilization putting your boards anywhere on the
panel.  (If these are production quantites, you'll probably want a full
custom panel, for many other reasons besides just PCB cost.)

1. 2mm width is the "everyone does this by default" size.  They can rout
at maximum speed with 2mm end mills.

2. Most fabs will do slots down to 1.0, even 0.6mm.  This is effective
for creepage between component pads, but takes more time -- it will be a
cost adder particularly for long routs.

3. Mouse bites are typically 0.5mm holes, closely spaced, positioned
tangential to (and inside) the board perimeter.  This ensures that the
broken material tends not to stick out.  It is rough, of course.

4. V-score is done in a straight line, and almost always completely
across the panel.  (You can order partial v-score, but the tolerances on
start/end position are awful -- it's basically a hand operation.)  It
can be done over routs, which gives the opportunity to make scored tabs
-- they break off cleaner than full score (which leaves a full edge
rough), and much smoother than mouse bites.

I'm fond of doing the latter -- a routed edge (often in profile, so it
fits nicely into place and has smooth edges), with scored tabs so it
breaks away smoothly.

Tim, I'm just designing a board just like this, that will snap full
panels into boards that then snap into a dozen small boards each.

How do the fabs like to receive Gerbers for this? Routing and V-scores
in separate layers/files? Or how? Can you share a setup you use to
create these Gerbers? (I'm using Kicad)

Clifford Heath

I've put the V-score info on the dimension layer, No questions or
problems. Just make the notes clear.

Cheers

 

[Winfield Hill]

Martin Riddle wrote...

Clifford Heath wrote:

How do the fabs like to receive Gerbers for this? Routing and
V-scores in separate layers/files? Or how? Can you share a
setup you use to create these Gerbers? (I'm using Kicad)

I've put the V-score info on the dimension layer, No questions
or problems. Just make the notes clear.

In Altium, I add another layer, and explain it in a note to
the PCB house. I wish Altium had separate place commands
for holes and slots (they make you place and alter pads),
and an official / layer setup for scoring.


--
Thanks,
- Win

 

[John Larkin]

On 5 May 2019 13:40:37 -0700, Winfield Hill <hill@rowland.harvard.edu>
wrote:

How to choose minimum slot size on PCB layout,
All about mouse bites, hole size, spacing, etc.

Breakaway for 0.5 x 10.5-in board, no grooves.
After machine assembly, break off 1.7" end piece.

What are you measuring about the hive? Temperature? Sounds?

I suspect the e-field would be interesting. Maybe plants and insects
use e-fields, like fish do.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Tim Williams]

"Winfield Hill" <hill@rowland.harvard.edu> wrote in message
news:qap8a601ul8@drn.newsguy.com...

In Altium, I add another layer, and explain it in a note to
the PCB house. I wish Altium had separate place commands
for holes and slots (they make you place and alter pads),
and an official / layer setup for scoring.

Altium uses a Region for that, or at least in "newer" versions; PCAD I don't
know about. Place a region and tag it as board cutout, just that easy.

I make sure to add the outline of the region to the board outline layer
(Keep-out Layer) just in case. Actually even better is, starting with the
layout and use Tools/Convert/Create Region from Selected Objects, and
setting the new region to cutout.

V-score support would be nice, kind of odd I guess that they don't. They do
have flex support (kinda sorta done in a similar way, cutting the design
into board regions), and AD17 and 18 or thereabouts added backdrilling and
blind holes and stuff, which is nice I guess.

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

 

[Winfield Hill]

Tim Williams wrote...

Winfield Hill wrote,
In Altium, I add another layer, and explain it in a note to
the PCB house. I wish Altium had separate place commands
for holes and slots (they make you place and alter pads),
and an official / layer setup for scoring.

Altium uses a Region for that, ...

Aha, Place Solid Region, I never explored that, thanks!

Place a region and tag it as board cutout, just that easy.

I make sure to add the outline of the region to the board
outline layer (Keep-out Layer) just in case. Actually
even better is, starting with the layout and use
Tools/Convert/Create Region from Selected Objects,
and setting the new region to cutout.

V-score support would be nice, kind of odd I guess that
they don't. They do have flex support (kinda sorta done
in a similar way, cutting the design into board regions),
and AD17 and 18 or thereabouts added backdrilling and
blind holes and stuff, which is nice I guess.

I moved to AD18, liked the dark grey, but after fighting
many issues, went back to 17 to get work done. Have
installed 19, maybe will get brave, and see if they
have fixed a bunch of stuff, or not.


--
Thanks,
- Win

 

[Tom Gardner]

On 06/05/19 12:15, Jeroen Belleman wrote:

Tim Williams wrote:
"Winfield Hill" <hill@rowland.harvard.edu> wrote in message
news:qaokrf0tsj@drn.newsguy.com...
I am a V-score fan, but the extra distances required
beyond my PCB section are troublesome.  Long V-scores
(e.g., 10 inches) are hard to break, and using a brake
or other tool, puts machine assembled parts at risk.
What's more, I feel compelled to sand the broken edges.

Yeah, that's a good reason to, well -- what they do commercially is use a
dual-pizza-cutter contraption to more like wedge the boards apart, rather than
bend and break them.  (You still want a good 100-200 mils clearance around the
board edge, where components are prohibited; they aren't always careful about
parts close nearby.)  But otherwise, yeah, good reason to make tabs.


V-score over routes, what?  Cuts the trace, right?
Sounds super useful, but leaves me totally confused.
Hmm: rout, route?

Yeah, "rout".  Regrettable that the same word (give or take spelling, if
that's even the correct spelling for this use actually..?) is used, within the
same subject, for two very different things.  I'm sure you know an English
professor to gripe at about it. :^)


Aren't they two different words? To route, pronounced 'ROOt' and
meaning 'planning a path' and to rout, pronounced 'Rowt' meaning
'to dig up'?

Yes, and you also "Rowt" mobs and armies.