Board outline thickness?

Questions about the BatchPCB service

Moderator: robacarp

Locked
PJMonty
Posts: 14
Joined: Sat Feb 26, 2005 7:11 pm

Board outline thickness?

Post by PJMonty » Sat Feb 26, 2005 7:31 pm

I use Protel 2.8 to create boards. How thick should I make the board outline? Is 1 mil okay or do you prefer something heavier? Also, is the routing done to the outside of the line, the inside, or the middle? I ask only because if I use a 10 mil line (for example), the difference of where the router goes adds up to something noticeable. Of course, if a 1 mil line is acceptable, then the last question is pretty moot.

Thanks,
PeterM

User avatar
sparky
Site Admin
Posts: 862
Joined: Mon May 05, 2003 6:02 pm
Location: Colorado
Contact:

Post by sparky » Mon Mar 28, 2005 8:52 am

Most of our borders are 10mil. I've never thought about the absolute milling sizes - most tolerances are +/-5mil. I can only assume a boards temperature would affect some of that.

I would suggest using a 10mil outline on your first board then measuring for future orders.

A 1mil outline should be fine for the manufacturer, but it makes it a bit harder on us to see during panelization.

-Nathan

Steve
Posts: 44
Joined: Sat Mar 26, 2005 9:16 am
Location: Brisbane Australia

Post by Steve » Tue Mar 29, 2005 2:16 am

Most of our borders are 10mil. I've never thought about the absolute milling sizes - most tolerances are +/-5mil. I can only assume a boards temperature would affect some of that.
I have some experience with PCB milling, so I'll say a few words here.

If you use an outline layer to define the edges of your board, then the manufacturer will rout to the centreline of the border track. The software we use does this automatically (when I say 'we' I mean the company I work for, not SFE). The width of the track is not important. What IS important is that the border tracks meet each other accurately at the corners.

There are some issues I know of that affect routing accuracy. The major one is that the panels to be routed are aligned with the router machine using 0.125" inch pins. This is always likely to introduce some error. Sometimes, for example, the pin hole in the panel is damaged, or blocked with solder so that the pin doesn't insert properly.

The other issues are all related. The router bit does bite into the material and this can cause deflection due to the tool bending slightly, or wear on the router spindle, or even the material distorting slightly during routing. FR4 probably doesn't distort much, but perspex certainly does.

I've seen badly aligned edges due to the CNC router being incorrectly homed, but this is a hardware problem and not the common experience.

Steve.

PJMonty
Posts: 14
Joined: Sat Feb 26, 2005 7:11 pm

Post by PJMonty » Tue Mar 29, 2005 8:53 pm

I appreciate the info guys.

Thanks,
PeterM

Locked

Return to “BatchPCB”