Electrolytic capacitor cover method and materials for the manufacture thereof

• US 6,370,016 B1
• Filed: 11/13/2000
• Issued: 04/09/2002
• Est. Priority Date: 08/06/1997
• Status: Expired due to Fees

• Current Assignee: BC Components Holdings B.V.
• Original Assignee: BC Components Holdings B.V.
• Inventors: Stevens, James L., Dapo, Roland F.
• Primary Examiner(s): Reichard, Dean A.
• Assistant Examiner(s): Thomas, Eric W.
• Application Number:
  US09/711,826
• Time in Patent Office: 512 Days
• Field of Search: 361/517-521, 361/536-540
• US Class Current: 361/519
• CPC Class Codes: H01G 9/08 Housing; Encapsulation
• CPC Class Codes: H01G 9/10 Sealing, e.g. of lead-in wires

Abstract

Improved covers for electrolytic capacitors, offering both durability and low extractability of halides by high temperature electrolytes, can be produced from molding compositions comprising thermoset polymers having low halide extractability, preferably based on materials such as phenolic resins, and nonporous fillers, the compositions preferably being essentially free of porous fillers.

Claims

1. An electrolytic capacitor cover produced by a method comprising

(a) preparing a molding composition comprising a thermoset resin and a nonporous filler, said nonporous filler being in an amount of 25 to 90 weight percent, said molding composition having a low halide extractability such that less than 1 ppm of halide ion is extracted when said molding composition is immersed in water at 90°

C. for 64 hours, and wherein said molding composition has an extraction ratio of extracted halide to bulk halide in the molding composition of less than 0.1, and

(b) molding said cover from said molding composition.

2. The electrolytic capacitor cover in accordance with claim 1, wherein said resin is a phenolic resin.

3. The electrolytic capacitor cover in accordance with claim 2, wherein the molding composition comprises 20 to 40 weight percent of the phenolic resin and further comprises 2 to 20 weight percent of a mineral fiber, with the balance of the molding composition weight percent being a nonporous filler other than the mineral fiber.

4. The electrolytic capacitor cover in accordance with claim 1, wherein said molding composition further comprises a nonporous mineral fiber, said mineral fiber being in an amount of about 2 to about 20 weight percent based on the weight of said molding composition.

5. The electrolytic capacitor cover in accordance with claim 1, wherein said molding composition is essentially free of porous fillers.

6. The electrolytic capacitor cover in accordance with claim 1, wherein the molding is carried out by injection molding.

7. The electrolytic capacitor cover in accordance with claim 1, wherein the molding is carried out by transfer molding.

8. The electrolytic capacitor cover in accordance with claim 1, wherein the nonporous filler is in an amount of 25 to 75 weight percent.

9. The electrolytic capacitor cover in accordance with claim 1, wherein the molding composition contains 30 to 60 weight percent of the resin.

10. The electrolytic capacitor cover in accordance with claim 9, wherein the nonporous filler is selected from the group consisting of mica, alumina, silica, calcium carbonate, clay, talc, feldspar, glass fiber, glass spheres, solid ceramic spheres formed from fly ash, hollow spheres of sodium silicate, hollow spheres of alumina, aramid fiber and hybrid fibers containing aramid and carbon.

11. The electrolytic capacitor cover in accordance with claim 10, wherein the molding composition further comprises 2 to 8 weight percent of a mineral fiber selected from the group consisting of wallastonite, wallastakup, glass fiber and asbestos.

12. The electrolytic capacitor cover in accordance with claim 1, wherein the nonporous filler is in an amount of 30 to 60 weight percent.

13. A durable cover for an electrolytic capacitor molded from a thermoset molding composition comprising (a) from 20 to about 40 weight percent of a phenolic resin, (b) from about 2 to about 20 weight percent of a mineral fiber, and (c) the balance being a nonporous filler, said molding composition having a low halide extractability such that less than 1 ppm of halide ion is extracted when said molding composition is immersed in water at 95°

C. for 64 hours.

14. The cover in accordance with claim 13, wherein said molding composition is essentially free of a porous filler.