The procedure used for etching the copper foil from the base insulating materials may significantly affect the results of electrical tests. This is true primarily for two reasons. First, the geometry of the copper which remains and forms the electrodes is in part determined by the etching procedure; this is particularly true of closely spaced electrodes on the same surface when the property to be measured depends on the electrode geometry. Second, electrical conductance in the material, particularly surface conductance, may be affected by the chemicals used to etch the copper, the length of time of etching, and the manner in which the specimen is cleaned after etching.

This practice standardizes the etching procedure in order to provide a basis for comparison of electrical properties of copper-clad electrical insulating materials and thermosetting laminates. Experience has shown that the test circuit can be accurately prepared using this procedure, and that the specimen will be substantially free of etching-induced, electrically-conductive contaminants.

It is recognized that commercial processes utilized to manufacture printed circuits may differ appreciably from this practice. Therefore, the results of tests on specimens etched in accordance with this practice may differ from results obtained on specimens etched in a commercial process. Specimens should be etched in accordance with a procedure different from this practice, if it is desired to determine the influence of the different procedure on electrical properties.