Question: I have a question concerning ceramic CCA and their bake out after aqueous wash cycle prior to parylene coating. In theory, parylene deposition will draw off any moisture before the coating process. Currently we bake at 149F for one hour before masking and coating preparation. Do you have any information on the amount of absorption for ceramic CCA’s?
Answer: I don’t have any information on the absorption capabilities of ceramic components. I did find this test method on the web to check for the permeability of ceramic materials. I would think getting in touch with the component manufacturer to get the material specifications would help and they should be able to provide you with the permeability of the material they use. As for drying the material, this would depend upon the length of time that is taken from the bake cycle to the conformal coating cycle and what the relative humidity is in the particular area of the facility. For example baking an FR-4 Board for 24 hours dries it out, but the moisture gets reabsorb within 8 hours, so quick processing is important.
Here is a link to a test method on ASTM: Standard Test Methods for Vitrified Ceramic Materials for Electrical Applications