As good as dipping is for applying conformal coating most conformal coating users spray it or use a Nordson select coat. Conformal coatings have a nasty habit of wicking up into places they shouldn't be (like connectors). Masking is time consuming and ill defined.

  Spraying will not cover the back sides of the flat leads of ball grid arrays. In a perfect world the coating would provide a complete envelope  over these leads, bridging the gaps between the leads. This doesn't always happen, particularly in the corners and particularly when  a tall component blocks spray from one side. In this instance the complete envelope (or bag without a hole) is wishful thinking. Sometimes bridging of the coating between leads is iffy.

  Liquid conformal coatings have a tendency to run off sharp bends in flat wire leads (we called those bends knees). These "knees" do not fluoresce when coated boards are inspected with a black light in a darkened room.

  Doug Pauls' employer (and I'm sure some other companies) recognized the short comings of traditional conformal coatings for this application and developed their own techniques.

  I have seen many instances where smaller companies try to develop similar solutions "on the fly" with unexpected and undesired consequences.

  Edward Mines




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