We get burrs on larger hole sizes over 3mm and find that deburr brushes do not 
do the job on heavier burrs. If you use wet & dry with a rubber block and light 
pressure to cut the burrs down they should not be pushed into the holes. It is a 
manual operation but does a better job. After deburring this way, the deburr 
machine gives a final surface polish for subsequent processing. It should only 
be necessary to deburr the top side of the top panel so it is not too much extra 
work. 240 grit is good enough for this job but be careful not to put the panel 
onto a flat surface as foil damage can result on the bottom side from trapped 
particles. Use a rubber mat with sharp ridges so that particles can drop down 
into the grooves. Use a filter face mask to prevent breathing in copper dust.

If you get heavy burrs on the smaller sizes, something is wrong with the drill 
feeds and speeds. As a guide, RPM should be set to give a peripheral speed of 
500-600 fpm with an infeed of 2 - 3 mil per rev. Pulling the drill out too fast 
may also contribute to the problem. 

I would like to hear of a better way but hope this helps,
Paul Gould
EMail [log in to unmask]

In your message dated Wednesday 11, December 1996 you wrote :
> 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.

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