Silicone Oil Removal from Polyimide Surface

Question:
How do you clean residual silicone oils from polyimide film surfaces during a lamination process (polyimide bonded to Inconel metal foils)? The oil is only contacting the polyimide. What can be used to clean this polyimide surface that will leave behind no residue?

Answer:
You have a very challenging problem here. Silicone oils are very tenacious and difficult to remove. Polyimides are somewhat delicate and some do not like water, so you will have to confirm these factors prior to using water based cleaners, which is what Alconox sells. Moreover, polyimides often don’t tolerate alkalinity or high temperature. Typcially silicone oils are removed by high emulsifying alkaline cleaners at very high temperatures. For most silicone oil cleaning we recommend 2% Alconox at 170 deg F under immersion cleaning. Assuming the polyimide being cleaned is thermoset, you should be ok with high temperature, however since there may be a problem with alkalinity compatibility, so our recommendation is an acid cleaner, Citranox. Specifically 4% Citranox at 170 deg F using immersion cleaning, ideally in an ultrasonic tank if that is available or alternatively by soaking and using some sort of devise to mechanically clean with, i.e. a wipe or soft brush. Citranox is a high emulsifying mild acid (pH 2.5) cleaner that has the best chance to clean silicone oils. We suggest that you try 10 minutes in an ultrasonic tank or 30 minutes of soaking followed by some sort of mechanical cleaning. If the polyimide can not withstand heat, then the only reasonable thing to try is the hottest temperature 2% Alconox solution that the polyimide will tolerate. Ideally use ultrasonic cleaning or the same soaking/scrubbing process stated above with triple the soak times.

Alconox cleaners are available globally with consistent formulations and are GMP compliant. Downloadable certificates of analysis, technical bulletins, MSDS, trace analysis, and inhibitory residue testing are available from the Alconox website at Alconox.com.