We are experiencing sporadic instances of copper burrs after deburring.  It 
appears that the deburr brushes are "shaving" burrs and almost but not quite 
removing them.  Describing the condition as a burr may be misleading because 
most people think of a burr as protruded copper.  These burrs exist when the 
surface is 100% smooth and free of surface burrs after drill . What is left 
is a curl of copper protruding the hole. What we have observed and done so far:

-When it happens, it is on the whole job-maybe a 2 panel run, maybe a 100 
panel run.

-it occurs on multilayer and double sided panels.

-it happens on .5 ounce through 2 ounce foils.

-we have tried every combination of brushes.  320 grit works as well as 
anything else. (The deburr machine has 2 brushes top, 2 brushes bottom.  The 
operators are performing brush footprint checks several times a day.

-it appears to be on the top side of the panel as it is drilled. We have had 
our drill tool supplier in (inconclusive)and have emphasized the obvious to 
the drill operators-clean between panel stacks, make sure depth is correct, etc.

Any ideas?

thanks,

Lyle Anderson
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