Method for encapsulation of electronics received in water meter pits with an improved wax-based encapsulant/moisture barrier
View Patent ↗The presently disclosed subject matter is directed to method for forming an encapsulant and coating electronic components such as those utilized in AMR technology with the encapsulant. The encapsulant comprises a wax, a tackifier, a polymer, a plasticizer, a thixotropic agent, and an antioxidant and is designed to protect electronic components from harsh environments such as those where high levels of humidity or corrosive liquids may be present. For example, the encapsulant exhibits minimal percent weight gain due to moisture vapor when subjected to temperatures ranging from about −40° C. to about 70° C. and relative humidities ranging from 0% to 85% over a period of 200 days.
1. A method for forming an encapsulant and coating an electronic component with the encapsulant, whereby the encapsulant protects electronic components used in automatic meter reading technology from moisture and corrosive liquids, comprising:
mixing a wax, a tackifier, a polymer, and a plasticizer to form the encapsulant, wherein the mixing occurs at a temperature ranging from about 90° C. to about 120° C.;
adjusting the temperature of the electronic component to a temperature ranging from about 80° C. to about 95° C.;
adjusting the temperature of the encapsulant to a temperature ranging from about 80° C. to about 95° C.; and
dispensing the encapsulant around the electrical component to form a coating round the electrical component; and
allowing the coated electrical component to harden and cool before operating the electronic component at temperatures of less than about 65° C., wherein the encapsulant exhibits a percent weight gain ranging from about 0.001% by, weight to about 0.75% by weight percent over, a period of 200 days when subjected to temperature cycling ranging from −40° C. to 70° C and humidity cycling ranging from 0% to 85% relative humidity.
2. The method as in claim 1 , wherein the wax is present in an amount ranging from about 40% by weight to about 60% by weight of the encapsulant.
3. The method as in claim 1 , wherein the wax comprises a microcrystalline wax, a paraffin wax, or a Fischer-Trope wax.
4. The method as in claim 1 , wherein the tackifier is present in an amount ranging from about 20% by weight to about 40% by weight of the encapsulant.
5. The method as in claim 1 , wherein the tackifier comprises a hydrocarbon resin; a glycerol ester of partially hydrogenated rosin; a thermoplastic, acidic resin; or a thermoplastic ester resin.
6. The method as in claim 1 , wherein the polymer is present in an amount ranging from about 2.5% by weight to about 20% by weight of the encapsulant.
7. The method as in claim 1 , wherein the polymer comprises a polyolefin, an ethylene-propylene copolymer, or an isobutylene.
8. The method as in claim 1 , wherein the plasticizer is present in an amount ranging from about 5% by weight to about 25% by weight of the encapsulant.
9. The method as in claim 1 , wherein the plasticizer comprises a polyisobutylene having a molecular weight ranging from about 500 g/mole to about 2500 g/mole.
10. The method as in claim 1 , further comprising a thixotropic agent, wherein the thixotropic agent is present in an amount ranging from about 0.25% by weight to about 1.50% by weight of the encapsulant.
11. The method as in claim 10 , wherein the thixotropic agent comprises a hydrophobic silica.
12. The method as in claim 1 , further comprising an antioxidant, wherein the antioxidant is present in an amount ranging from about 0.01% by weight to about 0.20% by weight of the encapsulant.
13. The method as in claim 12 , wherein the antioxidant comprises a phenolic antioxidant.
14. The method as in claim 1 , wherein the encapsulant has a melting temperature ranging from about 70° C. to about 80° C.
15. The method as in claim 1 , wherein the encapsulant has a dispensing temperature ranging from about 80° C. to about 95° C.
16. The method as in claim 1 , wherein the encapsulant has a viscosity ranging from about 250 centipoise to about 450 centipoise when dispensed.
17. The method as in claim 1 , wherein the encapsulant has a dielectric constant ranging from about 2.0 to about 8.0.
18. The method as in claim 1 , wherein the encapsulant exhibits a percent weight gain ranging from about 0.001% by weight to about 0.75% by weight of the encapsulant over a period of 200 days at 35° C. and 95% relative humidity.
19. The method as in claim 1 , wherein the encapsulant exhibits a percent weight gain ranging from about 0.05% by weight to about 1.5% by weight over a period of 200 days at 70° C. and 85 percent relative humidity.