- Polyurethane (UR) conformal coatings generally provide good humidity & moisture protection although not always as good as the acrylics. However, it normally is enough to protect the circuit board.
- Normally, urethanes are selected for their excellent chemical resistance. This is because the coatings cure rather than dry. That is they cross-link by one of many different methods including heat, UV, moisture and catalysed cure.
- Typically they have higher dielectric properties compared to the acrylic conformal coatings.
- Their chemical resistance, however, can be a limitation since rework and repair generally is more difficult than the acrylic coatings.
- UR coatings are normally available as either single or two-component formulations. Pot life is dependent on the cure mechanism but can be more limited than the acrylic coatings.
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