Can anyone recommend a good mousebite drill pattern that breaks cleanly?

[deanclaxton]

I use JLCPCB for my boards generally, and use a fairly generous 2mm routing slot width and 6mm tab (4mm at narrowest point). I'm interested in drill patterns for the tab which break away cleanly - recommended drill size and spacing, board edge to drill centre distance etc. Most of the patterns I've used to date leave "fingers" of FR4 sticking out past the board edge between the holes which leads me to think that I'd be better off going smaller on the drills and having more of them.

The latest pattern I used was 5 x 0.75mm holes spaced at 1.27mm centres and set back 0.25mm from the board edge. The routing path intersected the holes at each end  ( I was trying to ensure the snapped edge was back inside the board outline). See the attached file for the layout I am describing.

Very interested in patterns that people have had good clean easy breaking boards with.

[Alex Eisenhut]

Depends on board thickness and material and how many mousebites you have in a line. Easiest is to simply let the assembly house tell you what they think is best and use that.

[Algoma]

Few pattern notes here, if of any use:

https://www.electronicdesign.com/technologies/boards/article/21801451/pcb-designers-need-to-know-these-panelization-guidelines

Cleanest Edge would be a straight V-Groove but requires a bit more effort to separate the panels.

https://www.allpcb.com/mouse_bites_pcb.html

[deanclaxton]

Thanks - yeah the catch there is that I'm rounding the corners on the boards which makes v-score a bit tricky. Will definitely give that more thought though. Also on one design there are traces going across the bridge - so I need a tab for that one.

That's a good link - pretty sure I used those guideline originally. I might try smaller drills and more of them with tighter spacing.

Actually there is a recommendation in there "Ideally with outside edge of holes in line with edge of board - cleaner
break" where the hole is tangent to the board edge - might give that a go. That would mean moving the drill centre line back inside the board slightly in my case.

[beanflying]

While this will still likely need a wipe with something for the sharp edge (deburring tool) post breaking out any reason not to consider this style. I use this on timber boards when routing out panels (manually) and last time I fired up my baby router to do a PCB it was the 'normal' toolpath. It is also the more normal panel method with larger CNC routers as it avoids a bit change.

Last boards I got from OSHPark needed a fair bit of work to fix their mousebite pattern.