Process for solid electrolytic capacitors using polymer slurries

• US 8,808,403 B2
• Filed: 09/14/2011
• Issued: 08/19/2014
• Est. Priority Date: 09/15/2010
• Status: Active Grant

• Current Assignee: Kemet Electronics Corporation (Yageo Corporation)
• Original Assignee: Kemet Electronics Corporation (Yageo Corporation)
• Inventors: Qiu, Yongjian, Hahn, Randolph S., Key, Kristen, Chen, Qingping
• Primary Examiner(s): NIKMANESH, SEAHVOSH J
• Application Number:
  US13/232,325
• Publication Number:
  US 20120063063A1
• Time in Patent Office: 1,070 Days
• Field of Search: None
• US Class Current: 29/25.03
• CPC Class Codes: H01G 9/0029 Processes of manufacture
• CPC Class Codes: H01G 9/028 Organic semiconducting electrolytes, e.g. TCNQ
• CPC Class Codes: H01G 9/15 Solid electrolytic capacitors H01G11/00 takes precedence

Abstract

A process for forming a solid electrolytic capacitor and an electrolytic capacitor formed by the process. The process includes: providing an anode wherein the anode comprises a porous body and an anode wire extending from the porous body; apply a thin polymer layer onto the dielectric, and

forming a dielectric on the porous body to form an anodized anode;

applying a first slurry to the anodized anode to form a blocking layer wherein the first slurry comprises a first conducting polymer with an median particle size of at least 0.05 μm forming a layer of crosslinker on the blocking layer; and

applying a layer of a second conducting polymer on the layer of crosslinker.

Claims

1. A process for forming a solid electrolytic capacitor comprising:

providing an anode wherein said anode comprises a porous body and an anode wire extending from said porous body;

forming a dielectric on said porous body to form an anodized anode;

and

applying a first slurry to said anodized anode to form a blocking layer wherein said first slurry comprises a first conducting polymer with a median particle size of at least 0.05 μ

m;

forming a layer of crosslinker on said blocking layer; and

applying a slurry of a second conducting polymer on said layer of crosslinker.

2. The process for forming a solid electrolytic capacitor of claim 1 wherein said second conducting polymer is a slurry.

3. The process for forming a solid electrolytic capacitor of claim 1 wherein said median particle size is at least 0.065 μ

m.

4. The process for forming a solid electrolytic capacitor of claim 1 wherein said first conducting polymer and said second conducting polymer are the same.

5. The process for forming a solid electrolytic capacitor of claim 1 wherein said layer of crosslinker is dried prior to applying subsequent layers.

6. The process for forming a solid electrolytic capacitor of claim 1 further comprising applying at least one subsequent crosslinker layer followed by at least one subsequent conducting polymer.

7. The process for forming a solid electrolytic capacitor of claim 1 further comprising drying each layer of said conducting polymer and each layer of said crosslinker prior to application of a subsequent layer.

8. The process for forming a solid electrolytic capacitor of claim 1 wherein at least one of said first conducting polymer or said second conducting polymer is selected from the group consisting of polyaniline, polythiophene and polypyrrole.

9. The process for forming a solid electrolytic capacitor of claim 8 wherein said polythiophene is polyethylenedioxythiophene.

10. The process for forming a solid electrolytic capacitor of claim 1 further comprising forming a conducting polymer pre-layer prior to formation of said blocking layer.

11. The process for forming a solid electrolytic capacitor of claim 10 wherein said conducting polymer pre-layer is formed by in-situ polymerization.

12. The process for forming a solid electrolytic capacitor of claim 11 wherein said in-situ polymerization is a process selected from the group consisting of electrolytic polymerization and chemical polymerization.

13. The process for forming a solid electrolytic capacitor of claim 1 wherein said crosslinker comprises at least one group selected from diamine, triamine, oligoamine, and a polyvalent cation.

14. The process for forming a solid electrolytic capacitor of claim 13 wherein said crosslinker comprises a polyvalent cation is selected from a compound with at least two phosphonium groups, a compound with at least one phosphonium group and at least one amine group and a compound with at least two sulfonium groups.

15. The process for forming a solid electrolytic capacitor of claim 13 wherein said crosslinker comprises a polyvalent metal cation.

16. The process for forming a solid electrolytic capacitor of claim 13 wherein said crosslinker comprises a material selected from the group consisting of:

(2-dimethylaminoethyl)triphenylphosphonium bromide;

p-xylyenebis(triphenylphosphonium bromide);

(2-dimethyl-aminoethyl)triphenylphosphonium bromide;

1,4-diaminocyclohexane or 1,4-bis(aminomethyl)cyclohexane;

ethylenediamine;

1,6-hexanediamine;

1,7-heptadiamine;

1,8-octanediamine 1,9-nonanediamine;

1,10-decanediamine;

1,12-dodecanediamine, N,N-dimethylethylenediamine;

N,N,N′

N′

-tetramethylethylenediamine;

N,N,N′

N′

-tetramethyl-1,4-butanediamine;

N,N,N,N′

N′

N′

-hexamethylhexamethylene-diammonium dibromide;

piperazine;

1,4-diazabicyclo[2.2.2]octane;

N,N,N′

N′

-tetrakis(2-hydroxypropyl)ethylenediamine;

N-[3-trimethoxysilyl)propyl]ethylenediamine;

1,4-bis(3-aminopropyl)piperazine;

N,N′

diacetyl-1,6-hexanediamine;

N,N,N′

,N′

-tetraacetylethylene diamine;

1,4-diformylpiperazines;

N,N′

-ethylenebis(stearamide);

1,4-bis(3-aminopropyl)piperazine;

N-(6-aminohexyl)-1,6-diaminohexane;

N-(3-aminopropyl)-1,4-diaminobutane;

3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane;

4,4′

-methylenebis(N,N-diglycidylaniline);

o-phenylene-diamine;

m-phenylenediamine;

p-phenylenediamine;

1,5-diaminonaphthalene;

1,8-diaminonaphthalene;

2,3-diaminonaphthalene;

3-aminophenyl sulfone;

4-aminophenyl sulfone;

4-aminophenyl ether;

3,3′

-diaminobenzidine;

2-(4-aminophenyl)ethylamine;

4,4′

-methylenedianiline;

2,6-diaminotoluene;

N,N,N′

N′

-tetramethyl-p-phenylenediamine;

4,4′

-bis(diethylaminobenzophenone;

4,4′

-bis(dimethylamino)benzhydrol;

3,3′

,5,5′

-tetramethylbenzidine;

Auramine O;

Rubine S;

m-xylenediamine;

phthalein;

Brilliant Blue G;

folic acid;

4,4′

,4″

-methylidinetris(N,N-dimethylaniline);

citrulline;

arginine;

glutamine;

lysine;

asparagine;

histidine;

tryptophan;

poly(propylene glycol)-bis(2-aminopropyl)ether;

polyethyleneimine;

poly(allylamine);

ethoxylated polyethyleneimine;

17. The process for forming a solid electrolytic capacitor of claim 13 wherein said crosslinker comprises sulfonic acid.

18. The process for forming a solid electrolytic capacitor of claim 17 wherein said crosslinker is selected from the group consisting of decanediamine toluenesulfonate and polystyrene sulfonate.

19. The process for forming a solid electrolytic capacitor of claim 1 wherein said crosslinker concentration is no more than 3500 μ

g per gram of a combination of said anode, said dielectric, said blocking layer and any additional conducting polymer layer.

20. The process for forming a solid electrolytic capacitor of claim 19 wherein said crosslinker concentration is no more than 2000 μ

g per gram of said combination.

21. The process for forming a solid electrolytic capacitor of claim 20 wherein said crosslinker concentration is no more than 1500 μ

g per gram of said combination.

22. The process for forming a solid electrolytic capacitor of claim 1 further comprising washing after applying said second conducting polymer.

23. The process for forming a solid electrolytic capacitor of claim 22 wherein said washing is with water.

24. The process for forming a solid electrolytic capacitor of claim 22 wherein said washing is at a temperature of at least 5°

C. to no more than 85°

C.

25. The process for forming a solid electrolytic capacitor of claim 24 wherein said washing is at a temperature of at least 30°

C.

26. The process for forming a solid electrolytic capacitor of claim 25 wherein said washing is at a temperature of at least 50°

C.

27. The process for forming a solid electrolytic capacitor of claim 1 wherein forming of said layer of crosslinker comprises dipping in a crosslinker solution.

28. The process for forming a solid electrolytic capacitor of claim 27 wherein said crosslinker solution comprises at least 4 wt % to no more than 15 wt % of said crosslinker.

29. The process for forming a solid electrolytic capacitor of claim 28 wherein said crosslinker solution comprises at least 6 wt % to no more than 10 wt % of said crosslinker.

30. The process for forming a solid electrolytic capacitor of claim 29 wherein said crosslinker solution comprises at least 7 wt % to no more than 9 wt % of said crosslinker.

31. The process for forming a solid electrolytic capacitor of claim 1 wherein said layer of crosslinker is present in an amount of 10 μ

moles per gram of a combination of said anode, said dielectric, said blocking layer and any additional conducting polymer layer.

32. The process for forming a solid electrolytic capacitor of claim 1 wherein said layer of crosslinker is present in an amount of 10 μ

N per gram of a combination of said anode, said dielectric, said blocking layer and any additional conducting polymer layer.

33. The process for forming a solid electrolytic capacitor of claim 1 wherein said layer of crosslinker is present in an amount of 20 μ

N per gram of a combination of said anode, said dielectric, said blocking layer and any additional conducting polymer layer.

34. The process for forming a solid electrolytic capacitor of claim 1 wherein said average pore size is 0.01 μ

m to 10 μ

m.

35. A solid electrolytic capacitor formed by the process of claim 1 wherein said porous body comprises planar faces and corners and wherein said conducting polymer has a thickness measured from an apex of said corners of at least 1 μ

m to no more than 15 μ

m.

36. The solid electrolytic capacitor of claim 35 wherein said porous body comprises planar faces and corners and wherein said conducting polymer has a thickness measured from an apex of said corners of at least 5 μ

m to no more than 15 μ

m.

37. The solid electrolytic capacitor of claim 35 wherein a ratio of a thickness of said polymer on a face to a thickness of said conducting polymer on at least one of a corner or an edge is no more than 20:

1.

38. The solid electrolytic capacitor of claim 37 wherein a ratio of a thickness of said conducting polymer on a face to a thickness of said conducting polymer on at least one of a corner or an edge is no more than 10:

1.

39. The solid electrolytic capacitor of claim 35 wherein said anode comprises a valve metal.

40. The solid electrolytic capacitor of claim 39 wherein said valve metal is selected from the group consisting of tantalum, aluminum and niobium.

41. The solid electrolytic capacitor of claim 39 wherein said anode is NbO.

42. A process for forming a solid electrolytic capacitor comprising:

providing an anode wherein said anode comprises a porous body and an anode wire extending from said porous body

forming a dielectric on said porous body to form an anodized anode;

apply a conductive polymer layer onto the dielectric, and

forming a layer of crosslinker on said conducting polymer layer; and

applying a conducting polymer slurry layer on said layer of crosslinker;

wherein after applying said conducting polymer slurry layer said crosslinker concentration is no more than 3500 μ

g per gram of a combination consisting of said anode, said dielectric, and all said conducting polymer.

43. The process for forming a solid electrolytic capacitor of claim 42 further comprising washing after applying said conducting polymer slurry layer.

44. The process for forming a solid electrolytic capacitor of claim 42 further comprising applying at least one subsequent crosslinker layer followed by at least one subsequent conducting polymer slurry layer.

45. The process for forming a solid electrolytic capacitor of claim 42 further comprising drying each layer of said conducting polymer and each layer of said crosslinker prior to application of a subsequent layer.

46. The process for forming a solid electrolytic capacitor of claim 42 wherein at least one of said conducting polymer layer or said conducting polymer slurry layer is selected from the group consisting of polyaniline, polythiophene and polypyrrole.

47. The process for forming a solid electrolytic capacitor of claim 46 wherein said polythiophene is polyethylenedioxythiophene.

48. The process for forming a solid electrolytic capacitor of claim 42 wherein said conductive polymer layer is formed by in-situ polymerization prior to said applying said conducting polymer slurry layer.

49. The process for forming a solid electrolytic capacitor of claim 48 wherein said in-situ polymerization is a process selected from the group consisting of electrolytic polymerization and chemical polymerization.

50. The process for forming a solid electrolytic capacitor of claim 42 wherein said crosslinker comprises at least one group selected from diamine, triamine, oligoamine, and a polyvalent cation.

51. The process for forming a solid electrolytic capacitor of claim 50 wherein said crosslinker comprises a polyvalent cation is selected from a compound with at least two phosphonium groups, a compound with at least one phosphonium group and at least one amine group and a compound with at least two sulfonium groups.

52. The process for forming a solid electrolytic capacitor of claim 50 wherein said crosslinker comprises a polyvalent metal cation.

53. The process for forming a solid electrolytic capacitor of claim 50 wherein said crosslinker comprises a material selected from the group consisting of:

(2-dimethylaminoethyl)triphenylphosphonium bromide;

p-xylyenebis(triphenylphosphonium bromide);

(2-dimethyl-aminoethyl)triphenylphosphonium bromide;

1,4-diaminocyclohexane or 1,4-bis(aminomethyl)cyclohexane;

ethylenediamine;

1,6-hexanediamine;

1,7-heptadiamine;

1,8-octanediamine 1,9-nonanediamine;

1,10-decanediamine;

1,12-dodecanediamine, N,N-dimethylethylenediamine;

N,N,N′

N′

-tetramethylethylenediamine;

N,N,N′

N′

-tetramethyl-1,4-butanediamine;

N,N,N,N′

N′

N′

-hexamethylhexamethylene-diammonium dibromide;

piperazine;

1,4-diazabicyclo[2.2.2]octane;

N,N,N′

N′

-tetrakis(2-hydroxypropyl)ethylenediamine;

N-[3-trimethoxysilyl)propyl]ethylenediamine;

1,4-bis(3-aminopropyl)piperazine;

N,N′

diacetyl-1,6-hexanediamine;

N,N,N′

,N′

-tetraacetylethylene diamine;

1,4-diformylpiperazines;

N,N′

-ethylenebis(stearamide);

1,4-bis(3-aminopropyl)piperazine;

N-(6-aminohexyl)-1,6-diaminohexane;

N-(3-aminopropyl)-1,4-diaminobutane;

3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane;

4,4′

-methylenebis(N,N-diglycidylaniline);

o-phenylene-diamine;

m-phenylenediamine;

p-phenylenediamine;

1,5-diaminonaphthalene;

1,8-diaminonaphthalene;

2,3-diaminonaphthalene;

3-aminophenyl sulfone;

4-aminophenyl sulfone;

4-aminophenyl ether;

3,3′

-diaminobenzidine;

2-(4-aminophenyl)ethylamine;

4,4′

-methylenedianiline;

2,6-diaminotoluene;

N,N,N′

N′

-tetramethyl-p-phenylenediamine;

4,4′

-bis(diethylaminobenzophenone;

4,4′

-bis(dimethylamino)benzhydrol;

3,3′

,5,5′

-tetramethylbenzidine;

Auramine O;

Rubine S;

m-xylenediamine;

phthalein;

Brilliant Blue G;

folic acid;

4,4′

,4″

-methylidinetris(N,N-dimethylaniline);

citrulline;

arginine;

glutamine;

lysine;

asparagine;

histidine;

tryptophan;

poly(propylene glycol)-bis(2-aminopropyl)ether;

polyethyleneimine;

poly(allylamine);

ethoxylated polyethyleneimine;

54. The process for forming a solid electrolytic capacitor of claim 50 wherein said crosslinker comprises sulfonic acid.

55. The process for forming a solid electrolytic capacitor of claim 54 wherein said crosslinker is selected from the group consisting of decanediamine toluenesulfonate and polystyrene sulfonate.

56. The process for forming a solid electrolytic capacitor of claim 42 wherein said crosslinker concentration is no more than 2000 μ

g per gram of said combination.

57. The process for forming a solid electrolytic capacitor of claim 42 further comprising washing after applying said conducting polymer slurry layer.

58. The process for forming a solid electrolytic capacitor of claim 57 wherein said washing is with water.

59. The process for forming a solid electrolytic capacitor of claim 57 wherein said washing is at a temperature of at least 5°

C. to no more than 85°

C.

60. The process for forming a solid electrolytic capacitor of claim 59 wherein said washing is at a temperature of at least 30°

C.

61. The process for forming a solid electrolytic capacitor of claim 60 wherein said washing is at a temperature of at least 50°

C.

62. The process for forming a solid electrolytic capacitor of claim 42 wherein forming of said layer of crosslinker comprises dipping in a crosslinker solution.

63. The process for forming a solid electrolytic capacitor of claim 62 wherein said crosslinker solution comprises at least 4 wt % to no more than 15 wt % of said crosslinker.

64. The process for forming a solid electrolytic capacitor of claim 63 wherein said crosslinker solution comprises at least 6 wt % to no more than 10 wt % of said crosslinker.

65. The process for forming a solid electrolytic capacitor of claim 64 wherein said crosslinker solution comprises at least 7 wt % to no more than 9 wt % of said crosslinker.

66. The process for forming a solid electrolytic capacitor of claim 42 wherein said layer of crosslinker is present in an amount of less than 10 μ

moles per gram of a sum of an anodized anode mass and all conductive polymer.

67. The process for forming a solid electrolytic capacitor of claim 42 wherein said layer of crosslinker is present in an amount of less than 10 μ

N per gram of a sum of polymer coated anodize anode mass.

68. The process for forming a solid electrolytic capacitor of claim 42 wherein said layer of crosslinker is present in an amount of less than 20 μ

N per gram of a sum of polymer coated anodize anode mass.

69. A process for forming a solid electrolytic capacitor comprising:

providing an anode wherein said anode comprises a porous body and an anode wire extending from said porous body;

forming a dielectric on said porous body to form an anodized anode;

forming a layer of crosslinker;

applying a layer of conducting polymer wherein said conducting polymer and said crosslinker interact; and

washing to remove excess crosslinker.

70. The process for forming a solid electrolytic capacitor of claim 69 wherein said conducting polymer is a slurry.

71. The process for forming a solid electrolytic capacitor of claim 69 further comprising applying at least one subsequent crosslinker layer followed by at least one subsequent conducting polymer.

72. The process for forming a solid electrolytic capacitor of claim 69 further comprising drying each layer of said conducting polymer and each layer of said crosslinker prior to application of a subsequent layer.

73. The process for forming a solid electrolytic capacitor of claim 69 wherein at least one of said first conducting polymer or said second conducting polymer is selected from the group consisting of polyaniline, polythiophene and polypyrrole.

74. The process for forming a solid electrolytic capacitor of claim 69 further comprising forming a blocking layer prior to said forming said layer of crosslinker.

75. The process for forming a solid electrolytic capacitor of claim 74 further comprising forming a conducting polymer pre-layer prior to formation of said blocking layer.

76. The process for forming a solid electrolytic capacitor of claim 75 wherein said conducting polymer pre-layer is formed by in-situ polymerization.

77. The process for forming a solid electrolytic capacitor of claim 76 wherein said in-situ polymerization is a process selected from the group consisting of electrolytic polymerization and chemical polymerization.

78. The process for forming a solid electrolytic capacitor of claim 69 wherein said crosslinker comprises at least one group selected from diamine, triamine, oligoamine, and a polyvalent cation.

79. The process for forming a solid electrolytic capacitor of claim 78 wherein said crosslinker comprises a polyvalent cation is selected from a compound with at least two phosphonium groups, a compound with at least one phosphonium group and at least one amine group and a compound with at least two sulfonium groups.

80. The process for forming a solid electrolytic capacitor of claim 78 wherein said crosslinker comprises a polyvalent metal cation.

81. The process for forming a solid electrolytic capacitor of claim 78 wherein said crosslinker comprises a material selected from the group consisting of:

(2-dimethylaminoethyl)triphenylphosphonium bromide;

p-xylyenebis(triphenylphosphonium bromide);

(2-dimethyl-aminoethyl)triphenylphosphonium bromide;

1,4-diaminocyclohexane or 1,4-bis(aminomethyl)cyclohexane;

ethylenediamine;

1,6-hexanediamine;

1,7-heptadiamine;

1,8-octanediamine 1,9-nonanediamine;

1,10-decanediamine;

1,12-dodecanediamine, N,N-dimethylethylenediamine;

N,N,N′

N′

-tetramethylethylenediamine;

N,N,N′

N′

-tetramethyl-1,4-butanediamine;

N,N,N,N′

N′

N′

-hexamethylhexamethylene-diammonium dibromide;

piperazine;

1,4-diazabicyclo[2.2.2]octane;

N,N,N′

N′

-tetrakis(2-hydroxypropyl)ethylenediamine;

N-[3-trimethoxysilyl)propyl]ethylenediamine;

1,4-bis(3-aminopropyl)piperazine;

N,N′

diacetyl-1,6-hexanediamine;

N,N,N′

,N′

-tetraacetylethylene diamine;

1,4-diformylpiperazines;

N,N′

-ethylenebis(stearamide);

1,4-bis(3-aminopropyl)piperazine;

N-(6-aminohexyl)-1,6-diaminohexane;

N-(3-aminopropyl)-1,4-diaminobutane;

3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane;

4,4′

-methylenebis(N,N-diglycidylaniline);

o-phenylene-diamine;

m-phenylenediamine;

p-phenylenediamine;

1,5-diaminonaphthalene;

1,8-diaminonaphthalene;

2,3-diaminonaphthalene;

3-aminophenyl sulfone;

4-aminophenyl sulfone;

4-aminophenyl ether;

3,3′

-diaminobenzidine;

2-(4-aminophenyl)ethylamine;

4,4′

-methylenedianiline;

2,6-diaminotoluene;

N,N,N′

N′

-tetramethyl-p-phenylenediamine;

4,4′

-bis(diethylaminobenzophenone;

4,4′

-bis(dimethylamino)benzhydrol;

3,3′

,5,5′

-tetramethylbenzidine;

Auramine O;

Rubine S;

m-xylenediamine;

phthalein;

Brilliant Blue G;

folic acid;

4,4′

,4″

-methylidinetris(N,N-dimethylaniline);

citrulline;

arginine;

glutamine;

lysine;

asparagine;

histidine;

tryptophan;

poly(propylene glycol)-bis(2-aminopropyl)ether;

polyethyleneimine;

poly(allylamine);

ethoxylated polyethyleneimine;

82. The process for forming a solid electrolytic capacitor of claim 78 wherein said crosslinker comprises sulfonic acid.

83. The process for forming a solid electrolytic capacitor of claim 82 wherein said crosslinker is selected from the group consisting of decanediamine toluenesulfonate and polystyrene sulfonate.

84. The process for forming a solid electrolytic capacitor of claim 69 wherein said crosslinker concentration is no more than 3500 μ

g per gram of said combination.

85. The process for forming a solid electrolytic capacitor of claim 84 wherein said crosslinker concentration is no more than 2000 μ

g per gram of said combination.

86. The process for forming a solid electrolytic capacitor of claim 85 wherein said crosslinker concentration is no more than 1500 μ

g per gram of said combination.

87. The process for forming a solid electrolytic capacitor of claim 69 wherein said washing is with water.

88. The process for forming a solid electrolytic capacitor of claim 69 wherein said washing is at a temperature of at least 5°

C. to no more than 85°

C.

89. The process for forming a solid electrolytic capacitor of claim 88 wherein said washing is at a temperature of at least 30°

C.

90. The process for forming a solid electrolytic capacitor of claim 89 wherein said washing is at a temperature of at least 50°

C.

91. The process for forming a solid electrolytic capacitor of claim 69 wherein forming of said layer of crosslinker comprises dipping in a crosslinker solution.

92. The process for forming a solid electrolytic capacitor of claim 91 wherein said crosslinker solution comprises at least 4 wt % to no more than 15 wt % of said crosslinker.

93. The process for forming a solid electrolytic capacitor of claim 92 wherein said crosslinker solution comprises at least 6 wt % to no more than 10 wt % of said crosslinker.

94. The process for forming a solid electrolytic capacitor of claim 93 wherein said crosslinker solution comprises at least 7 wt % to no more than 9 wt % of said crosslinker.

95. The process for forming a solid electrolytic capacitor of claim 69 wherein said layer of crosslinker is present in an amount of less than 10 μ

moles per gram of a sum of an anodized anode mass and a blocking layer mass.

96. The process for forming a solid electrolytic capacitor of claim 69 wherein said layer of crosslinker is present in an amount of less than 10 μ

N per gram of a sum of polymer coated anodize anode mass.

97. The process for forming a solid electrolytic capacitor of claim 69 wherein said layer of crosslinker is present in an amount of less than 20 μ

N per gram of a sum of polymer coated anodize anode mass.