[CCTALK] RE: scanners & circuit boards.. - test-drb@ccmp.vtda.org

20 May 2002

...
 From: "Davison, Lee"
&lt;Lee.Davison(a)merlincommunications.com&gt;

 > You can't scratch glass with metal. What
you can do
> is leave a thin trace of metal on the glass. Jewelers
> rouge will easily remove this is nothing else will. 
	 This is not true. Try running your windshield wipers
	without the rubber.

All generalisations have exeptions, however it's usually the road
grit and oxides on the end of the blades that do the scratching. 
 True but where are you going to find the really clean metal
to rub on the glass? Most surfaces of metals have oxides and other
material on them. I was making the point that under real world
conditions, one can scratch glass with metal objects. One should
not assume it is safe to rub metals on glass. If the pressure is
high enough, most hardened metals can scribe glass, even though
the glass is harder. This is more related to brittleness.

...

	And lastly, the quartz windows of the EPROMs
	are harder than glass.

As can be ceramic chip packages and the PCB itself (glass
fiber laminate).

   I think he was talking about the glass on the
scanner.

I was. 
 I meant this to be in relation to the UV passing.

...

Lee.

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