Controlled moisture vapor transmission filter assembly for electronic enclosures

1. An adsorbent construction for use in an electronic enclosure, the adsorbent construction comprising:

a) a plastic housing defining a cavity;

b) a first adsorbent material disposed within the cavity;

c) a substantially water-impermeable film coupled to the housing and covering the cavity, wherein the film defines an opening configured to allow fluid communication between the cavity and the interior of the electronic enclosure; and

d) a second adsorbent material, wherein the film is disposed between the first adsorbent material and the second adsorbent material, and wherein the substantially water-impermeable film regulates the flow of water vapor into and out of the first adsorbent material.

2. The adsorbent construction of claim 1 , wherein the first adsorbent material comprises silica gel.

3. The adsorbent construction of claim 1 , wherein the first adsorbent material comprises silica gel, molecular sieve, activated carbon, or combinations thereof.

4. The adsorbent construction of claim 1 , wherein the first adsorbent material comprises a compression molded tablet.

5. The adsorbent construction of claim 1 , wherein the first adsorbent material comprises at least 10 percent silica gel and at least 10 percent activated carbon.

6. The adsorbent construction of claim 1 , wherein the film comprises a metal coating.

7. The adsorbent construction of claim 1 , further comprising a filter material coupled to the plastic housing, wherein the film is disposed between the filter material and the housing.

8. The adsorbent construction of claim 1 , wherein the opening is less than 2.0 mm wide.

9. The adsorbent construction of claim 1 , wherein the second adsorbent has a water adsorption capacity of less than 5% grams per gram of adsorbent below 60% relative humidity.

10. An adsorbent construction for use in an electronic enclosure, the adsorbent construction comprising:

a) a first adsorbent material;

b) a housing defining an internal volume and comprising a substantially water-impermeable polymeric material, wherein the first adsorbent material is disposed within the internal volume;

c) an opening defined by the polymeric material;

d) a filter material in fluid communication with the opening; and

e) a second adsorbent material, wherein the polymeric material is disposed between the first adsorbent material and the second adsorbent material.

11. The adsorbent construction of claim 10 , wherein the first adsorbent material comprises silica gel.

12. The adsorbent construction of claim 10 , wherein the first adsorbent material comprises from 10 to 90 percent silica gel.

13. An adsorbent construction for use in an electronic enclosure, the adsorbent construction comprising:

a) a substantially rigid body defining an internal volume and at least a first opening;

b) a first adsorbent material positioned within the internal volume of the substantially rigid body, the adsorbent material substantially surrounded by a polymeric cover; and

c) a second adsorbent material positioned within the substantially rigid body, the second adsorbent material positioned outside of the polymeric cover.

14. The adsorbent construction of claim 13 , wherein the polymeric cover has a moisture vapor transmission rate of less than 25 grams per square meter per 24 hours per 1 mil thickness at 38 degrees C. and 90 percent relative humidity.

15. The adsorbent construction of claim 13 , wherein the adsorbent material comprises silica gel, molecular sieve, activated carbon, or combinations thereof.