PCB Cutting

[Mark Jones]

Those are scribes. A scoring knife has a slight hook and is sharpened
on the handle side of that hook, so it peels a thread of material off
when pulled.

Is scoring the copper clad really going to achieve a clean break? Seems to me
you'd have to at least score through the copper into the fiberglass. Even then,
would it necessarily break clean? Most boards AFAIK, are multi-layer, weaved
construction. Very strong. ISTR FR4 "splintering" when broken, but that was
without being scored.

For that matter, what about using a box & pan brake?
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=90606

 

[John Popelish]

Is scoring the copper clad really going to achieve a clean break? Seems to me
you'd have to at least score through the copper into the fiberglass.

Agreed. If you score through something like 1/8th to 1/4 of the way
through the board from each side, than the break isn't too fuzzy and
doesn't cause delamination to extend too far into the board from glass
fibers being pulled out of the matrix. After sliding the board along
a piece of silicon carbide sandpaper on the bench, the edged can look
pretty good.
But, yes, the scoring needs to be more than a surface blemish.

A negative I haven't seen mentioned in this thread about sawing
methods is the very hazardous properties of the fiberglass dust
generated. It is one of the reasons I dislike any method that
involved high speed cutters that disperse the dust into the air. I
have had months of respiratory problems following such procedures.

 

[Luhan Monat]

Mark Jones wrote:




Agreed. If you score through something like 1/8th to 1/4 of the way
through the board from each side, than the break isn't too fuzzy and
doesn't cause delamination to extend too far into the board from glass
fibers being pulled out of the matrix. After sliding the board along
a piece of silicon carbide sandpaper on the bench, the edged can look
pretty good.
But, yes, the scoring needs to be more than a surface blemish.

A negative I haven't seen mentioned in this thread about sawing
methods is the very hazardous properties of the fiberglass dust
generated. It is one of the reasons I dislike any method that
involved high speed cutters that disperse the dust into the air. I
have had months of respiratory problems following such procedures.

I seldom use fiberglass for small projects or prototypes, so scoring and
breaking works just fine for phenolics.