#1430
Author: Eldridge M. Mount III, EMMOUNT Technologies
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Subject: Optical density (OD) versus resistivity of metallized polyester
The relationship between resistivity and metal thickness is:
Thickness = resistivity x 100/surface resistance
For aluminum the resistivity is 2.65 ohm cm
But for an aluminum thickness below 5 angstroms, the data would be suspect because of the electrical effects on electrons due to the thin layer. You can measure the surface resistance and back-calculate the thickness and see where you are. Then you will have to relate OD to thickness independently, typically by transmission electron microscope measurements.
You also could search the literature for a reference of OD, or light transmission, for thin aluminum layers. However, I am not sure that at those OD levels you are achieving a complete film of aluminum or if you have an incomplete aluminum layer. I have no ready references for the thickness vs. OD at those ranges for aluminum. You will need to make measurements to determine if you have a complete film and then measure the thickness directly with a transmission electron microscope.
At this point your best bet is to simply measure what you obtain and develop a relationship between your optical and electrical results if you are wanting to use this data for QC purposes. However the aluminum film quality may affect the electrical readings.
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