snap off bits on PCB's

[drog_trog]

here is a screen capture from 1 of madbeans projects, I want to create a snap off bit in Eagle, is it just a case of spacing some holes withing the dimension layer?

[gtr2]

The term is mouse bite, yeah...it really is haha
Google PCB mouse bite and you'll have all the info you need.
Josh

[madbean]

I generally use a hole with 27 mil diameter and arrange them just as you see.

Couple things to watch out for:
- Make sure there is enough space between the holes but not too much.
- Make sure your dimension border isn't too close to the outside holes.
- Extra credit: if using ground planes on top or bottom, draw out rectangles in the bRestrict and tRestrict layers that cover just the bridge between the two PCBs. This eliminates the copper pour from the bridge. Why do this? To prevent any damage to the pour when snapping the two boards apart.

[drog_trog]

would it be just as easy to draw a line in the Vscore layer

[madbean]

Absolutely.

[drog_trog]

well for short bits i can use the mouse bites but for long snap off bits i will vscore it.

[alanp]

would it be just as easy to draw a line in the Vscore layer

Fab houses charge more for vscoring, if memory serves.

[madbean]

would it be just as easy to draw a line in the Vscore layer

Fab houses charge more for vscoring, if memory serves.

Elecrow does not, unless you mix more than one PCB design.

[drog_trog]

would it be just as easy to draw a line in the Vscore layer

Fab houses charge more for vscoring, if memory serves.

Elecrow does not, unless you mix more than one PCB design.

Good to know.

Brian, while I have your attention, Where are you upto on the Polytrog?

[gtr2]

Depending on the PCB array, V-score does not always work.
V-score is usually an upcharge for fabs the panalize your design with others.
If you V-score you need to pull back the copper.  Check your fab house for restrictions.
There are entire web pages devoted to both V-score and mouse bites and it's valuable info if you use any of those methods, along with your fab house specifications.

[aion]

I greatly prefer mouse bites to V-score. Here's how I do it:



Hole size is 19.68 mil (0.5mm) and they are spaced 30 mil apart. This violates the Eagle design rules at Elecrow (drill holes too close together), but they let it pass for mouse bites and I have never had an issue, so I just 'Approve' all of the DRC errors.

Mine are also inset from the PCB outline so that there are no protruding pieces of fiberglass once the boards are separated. They snap apart cleanly and easily, but are sturdy enough that they don't come apart unless you want them to.

[drog_trog]

Thanks Kevin