Recirculation filter for an electronic enclosure

1. A filter assembly for use in an electronic enclosure, the filter assembly comprising:

a first sheet of filter material defining an open front face, a closed rear face, and an internal recess, wherein the first sheet of filter media comprises a scrim material and an electrostatic material at least partially covering the scrim material; and

a second sheet of filter material disposed over the open front face and bonded to the first sheet of filter material, wherein the second sheet of filter material is substantially planar.

2. The filter assembly of claim 1 , wherein the scrim material comprises a woven material.

3. The filter assembly claim 1 , wherein the scrim material comprises polypropylene fibers.

4. The filter assembly of claim 1 , wherein the scrim material has a permeability of between about 100 ft./min. at 0.5 inches of water and about 800 ft./min. at 0.5 inches of water.

5. The filter assembly of claim 1 , wherein the electrostatic material comprises a mixed fiber medium comprising polypropylene and acrylic.

6. The filter assembly of claim 1 , wherein the electrostatic material has a permeability of between about 250 ft./min. at 0.5 inches of water and about 750 ft./min. at 0.5 inches of water.

7. The filter assembly of claim 1 , wherein the electrostatic material has a filtering efficiency of about 20% to about 99.99% for 20 to 30 micron particulate contaminants.

8. The filter assembly of claim 1 , wherein the internal recess has a ratio of maximum length to maximum diameter of the open front face of at least 1.0.

9. The filter assembly of claim 1 , wherein the internal recess of the filter assembly has an internal surface area that is at least 2 times the area at the open front face.

10. The filter assembly of claim 1 , wherein the filter assembly comprises a recirculation filter disposed within a housing of a disk drive, and the filter assembly is oriented to filter airflow induced by the rotation of one or more disks within the disk drive housing.

11. The filter assembly of claim 1 , wherein the second sheet of filter material comprises a scrim material and an electrostatic material at least partially covering the scrim material.

12. The filter assembly of claim 1 , wherein the second sheet of filter material comprises a screen layer.

13. A method of making a filter assembly comprising:

forming a first sheet of filter material to substantially retain the shape of an internal recess, wherein the first sheet of filter material comprises a scrim material and an electrostatic material at least partially covering the scrim material;

positioning a second sheet of filter material over the internal recess; and

welding the first sheet of filter material to the second sheet of filter material around the internal recess.

14. The method of claim 13 , wherein forming the first sheet of filter material comprises positioning the first sheet of filter material between a horn and a nest and applying force such that the first sheet of filter material substantially conforms to the shape of the nest.

15. The method of claim 13 , further comprising forming a border around the internal recess of the first sheet of filter material.

16. The method of claim 15 , wherein forming a border comprises applying sonic energy to the first sheet of filter material.

17. The method of claim 13 , further comprising trimming the first filter material and the second filter material extending beyond the welding of the first filter material to the second filter material.

18. The method of claim 13 , wherein the second sheet of filter material comprises an electrostatic layer and a scrim layer.

19. The method of claim 13 , wherein the first sheet of filter material comprises an electrostatic layer positioned between two scrim layers.

20. The method of claim 13 , wherein the electrostatic material is positioned within the internal recess of the first sheet of filter material.