Wireless process communication adapter with improved encapsulation
A wireless process communication adapter for field devices is provided. The adapter includes a metal housing having a first end and a second end. A chamber is defined between the first and second ends. A radio-frequency transparent radome is coupled to the first end. The second end has a field device coupling configured to attach to a field device. At least one circuit board is disposed within the chamber. The circuit board supports at least wireless process communication circuitry. A plurality of wires is coupled to the at least one circuit board and extends through the field device coupling. A silicone potting fills substantially all volume within the chamber not occupied by the at least one circuit board and wireless process communication circuitry.
1. A wireless process communication adapter for field devices, the adapter comprising:
a metal housing having a first end and a second end and defining a chamber therebetween, the first end having an RF transparent radome coupled thereto, the second end having a field device coupling configured to attach to a field device;
at least one circuit board disposed within the chamber, the circuit board supporting at least wireless process communication circuitry;
a plurality of wires coupled to the at least one circuit board and extending through the field device coupling;
a potting filling substantially all volume within the chamber not occupied by the at least one circuit board and wireless process communication circuitry;
a compressible layer separating at least one electrical component of the at least one circuit board from the potting, the compressible layer operable to prevent the potting from crushing the component due to thermal expansion of the potting; and
a release layer adhered to the metal housing, the release layer configured to promote adhesion of the potting to the at least one circuit board during repeated thermal cycling and creating a gap between the potting material and the metal housing at low temperatures;
wherein the potting comprises silicone potting which has a greater adhesion to the at least one circuit board than to the release layer;
whereby, during thermal contraction of the potting, the potting separates from the release layer while adhering to the at least one circuit board.
2. The adapter of claim 1 , wherein the potting is a two-part silicone potting.
3. The adapter of claim 1 , wherein the release layer is a lecithin.
4. The adapter of claim 3 , the compressible layer comprising foam disposed between the at least one electrical component on the at least one circuit board and the potting.
5. The adapter of claim 4 , wherein the foam pad is constructed from polyethylene.
6. The adapter of claim 5 , and further comprising a foam jacket surrounding the at least one electrical component.
7. The adapter of claim 1 , and further comprising a foam pad disposed between at least one electrical component on the at least one circuit board and the metal housing.
8. The adapter of claim 7 , wherein the foam pad is constructed from polyethylene.
9. The adapter of claim 8 , and further comprising a foam jacket surrounding the at least one electrical component.
10. The adapter of claim 8 , wherein the potting is cured at about 50 degrees Celsius.
11. The adapter of claim 1 , wherein the potting is cured at about 50 degrees Celsius.
12. The adapter of claim 1 , wherein the potting is silicone potting.
13. The adapter of claim 1 , wherein the potting has a large coefficient of thermal expansion relative to that of the at least one circuit board.
14. The adapter of claim 4 , wherein the foam comprises a foam pad that is compressed in response to thermal expansion of the potting.