How do I control my conformal coating thickness with my dip system?
The thickness of a conformal coating material applied during a dip process is dependent on several factors. However, the two critical points are:
- The viscosity of the conformal coating being applied
- the speed of withdrawal of the printed circuit boards coming out of the tank of the dip system
The viscosity of the conformal coating being applied
The viscosity of the conformal coating can be monitored by utilizing a flow cup. There are many designs but is essentially a cup with a hole in the base on a wire. You dip the cup into the liquid and lift it out of the conformal coating. you then time taken for the coating to empty from the cup.
Since the volume of the cup is known and fixed, you can relate the time to the viscosity of the conformal coating and you get a relatively accurate and simple method of measuring viscosity which is certainly suitable in 99% of cases.
The speed of withdrawal of the printed circuit boards coming out of the tank of the dip system
Using typical conformal coating dip systems like the DS101 dip system, the dip speed is controlled by air over oil hydraulics which can control the speed down to 2″ (50mm) per minute. This is very precise and more than adequate for conformal coating thickness control and repeatability. The key to dipping is to realise that the slower the withdrawal speed the thinner the conformal coating applied.
Control these two factors and you have a very repeatable conformal coating process.
Click DS101 Conformal coating Dip System for further information on the dip machines.
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