Encapsulated electrical device and method of fabrication

1. A device, comprising:

an electrical assembly having at least one electrical component;

an inner shell comprising a first polymeric material disposed around the electrical assembly and in contact with the electrical assembly, the inner shell comprising a first mechanical strength; and

an outer shell comprising a second polymeric material conformally disposed around the inner shell and in contact with the inner shell, the outer shell comprising a second mechanical strength greater than the first mechanical strength,

wherein the electrical component comprises a first coefficient of thermal expansion (CTE), the inner shell comprises a second CTE, and the outer shell comprises a third CTE, and wherein a difference between the first CTE and second CTE is less than 0.5×10 −5 /K, and the third CTE exceeds the first CTE by 4×10 −5 /K to 11×10 −5 /K.

2. The device of claim 1 wherein the electrical assembly has a first outer surface defining a first outer shape, the inner shell comprises a second outer surface defining a second outer shape different than the first outer shape; and wherein the outer shell comprises a third outer surface defining a third outer shape different than the first outer shape.

3. The device of claim 1 , wherein the inner shell comprises a thermoset material and the outer shell comprises a thermoplastic material.

4. The device of claim 1 , wherein the electrical assembly comprises a printed circuit board (PCB) and at least one electrical component disposed thereon.

5. The device of claim 1 , wherein the inner shell and outer shell are configured to operate over a temperature range of −50° C. to 150° C.

6. The device of claim 2 , wherein the second outer surface of the inner shell comprises a sealing rib assembly configured to increase sealing between the inner shell and outer shell by mechanically coupling to the outer shell.

7. The device of claim 2 , wherein the third outer shape is different than the second outer shape.

8. The device of claim 1 , wherein the inner shell comprises a post portion configured to couple to the outer shell.

9. A method of forming an electrical device, comprising:

providing an electrical assembly having at least one electrical component;

forming an inner shell comprising a first polymeric material around the electrical assembly, the inner shell being in contact with the electrical assembly; and

forming an outer shell comprising a second polymeric material around the inner shell and in contact with the inner shell,

wherein the electrical assembly comprises a first coefficient of thermal expansion (CTE), the inner shell comprises a second CTE, and the outer shell comprises a third CTE, and wherein a difference between the second CTE and first CTE is less than a difference between the third CTE and first CTE, wherein the forming the inner shell comprises:

providing the electrical assembly in a first mold;

dispensing a first liquid precursor of the inner shell into the first mold; and

performing a first injection molding process on the first liquid precursor and electrical component at a first temperature and a first pressure, wherein a singly encapsulated device is formed comprising the inner shell and electrical assembly, and

wherein the forming the outer shell comprises:

providing the singly encapsulated device in a second mold;

dispensing a second liquid precursor of the second polymeric material into the second mold; and

performing a second injection molding process on the singly encapsulated device at a second temperature and a second pressure greater than the first pressure.

10. The method of claim 9 , wherein the second temperature is higher than the first temperature.

11. The method of claim 9 , wherein the inner shell comprises a thermoset material, and wherein the outer shell comprises a thermoplastic material.

12. The method of claim 9 , wherein the first temperature is between 150° C. and 200° C. and the first pressure is between 20 kgf/cm 2 and 100 kgf/cm 2 .

13. The method of claim 9 , wherein the second temperature is between 275 and 315° C. and the second pressure is between 700 kgf/cm 2 and 1100 kgf/cm 2 .

14. A sensor device, comprising:

a printed circuit board;

at least one sensor attached to the printed circuit board;

an inner shell comprising a first polymeric material disposed around the printed circuit board and at least one electrical device, and in contact with the printed circuit board and at least one electrical device; and

an outer shell comprising a second polymeric material disposed around the inner shell and in contact with the inner shell, the inner shell comprising a first mechanical strength; and the outer shell comprising a second mechanical strength greater than the first mechanical strength,

wherein the printed circuit board comprises a first coefficient of thermal expansion (CTE), the inner shell comprises a second CTE, and the outer shell comprises a third CTE, and wherein a difference between the first CTE and second CTE is less than 0.5×10 −5 /K, and the third CTE exceeds the first CTE by 4×10 −5 /K to 11×10 −5 /K.

15. The sensor device of claim 14 , wherein the inner shell comprises a thermoset material and the outer shell comprises a thermoplastic material.

16. The sensor device of claim 14 , wherein the inner shell and outer shell are configured to operate over a temperature range of −50° C. to 150° C.

17. The sensor device of claim 14 , wherein the inner shell comprises:

a sealing rib assembly configured to increase sealing between the inner shell and outer shell by mechanically coupling to the outer shell; and

a post portion configured to couple to the outer shell.