wrote:
The frequency that I am lapping the crystals upto is 20 MHz and the
average spread observed is around 200 KHz,
This frequency spread is the difference in the frequency between the
highest frequency crystal and the lowest frequency crystal obtained out
of one batch of crystals i.e. when few hundred crystals were lapped
together the highest frequency crystal observed was of 20,150,000 Hz =
20.15 MHz while the lowest frequency crystal was around 19,950,000 Hz =
19.95 MHz thereby giving a spread of 200 KHz.
I hope its very clear now.
My target is to bring this spread below 50 KHz.......I want some help
Please....

Thank you very much for your time
Pankaj Trivedi

Lets start with what you are lapping. Is it a sawn disk ? I suspect so.
From a large xtal. This then would be one of the issues.

From Semiconductor background, the wafers (a xtal themselves) are lapped
but across the surface - up to 300mm now - the flat isn't flat. There are
hills and valleys all across the wafer. There are machines that measure this
and qualify a wafer to use. Sometimes it is lapped again. Often the wafers
are very think and after testing the die are back lapped for packaging.

SO I suspect the source and the lap is not to the spec level it needs to be.
After lapping - measure the flatness of the material. Light helps, but there
are machines. Research mirror lapping and measuring. Good stuff there!

I suspect you are fighting some of this - microscopic hills and valleys.

Martin

--
Martin Eastburn
@ home at Lion's Lair with our computer lionslair at consolidated dot net
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder

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