Method of making ceramic substrate

• US 6,041,496 A
• Filed: 02/11/1998
• Issued: 03/28/2000
• Est. Priority Date: 02/21/1997
• Status: Expired due to Fees

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Fortney, John H., Haq, Samuel F., Malone, Patrick F., Varner, Donald P.
• Primary Examiner(s): Arbes, Carl J.
• Application Number:
  US09/022,320
• Time in Patent Office: 776 Days
• Field of Search: 29/852, 29/851, 29/825, 156/89.18, 156/89.11, 156/89.12, 156/89.16, 156/89.17, 156/89.28, 174/257
• US Class Current: 29/852
• CPC Class Codes: A61N 1/02 Details
• CPC Class Codes: A61N 1/375 Constructional arrangements, e.g. casings
• CPC Class Codes: A61N 1/37512 Pacemakers
• CPC Class Codes: H01L 21/4857 Multilayer substrates multilayer metallisation on monolayer substrate H01L21/4846
• CPC Class Codes: H01L 21/4867 Applying pastes or inks, e.g. screen printing H01L21/486 takes precedence
• CPC Class Codes: H01L 23/49883 the conductive materials containing organic materials or pastes, e.g. for thick films for printed circuits H05K1/092
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/09701 Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H05K 1/0306 Inorganic insulating substrates, e.g. ceramic, glass
• CPC Class Codes: H05K 1/092 Dispersed materials, e.g. conductive pastes or inks
• CPC Class Codes: H05K 2201/035 Paste overlayer, i.e. conductive paste or solder paste over conductive layer
• CPC Class Codes: H05K 3/248 fired compositions for inorganic substrates
• CPC Class Codes: H05K 3/4061 for via connections in inorganic insulating substrates
• CPC Class Codes: H05K 3/4611 by laminating two or more circuit boards H05K3/4652 takes precedence
• CPC Class Codes: H05K 3/4629 laminating inorganic sheets comprising printed circuits, e.g. green ceramic sheets
• CPC Class Codes: H05K 3/4676 Single layer compositions
• CPC Class Codes: Y10S 428/901 Printed circuit
• CPC Class Codes: Y10T 29/49126 Assembling bases
• CPC Class Codes: Y10T 29/49165 by forming conductive walled aperture in base
• CPC Class Codes: Y10T 428/24917 : including metal layer
• CPC Class Codes: Y10T 428/24926 : including ceramic, glass, porcelain or quartz layer

Abstract

The present invention relates to multi-layer ceramic packaging of hybrid micro-electronic devices, including those for implantable medical devices. The invention permits size reduction and design simplification in such packaging by eliminating the need for electrolytic or electroless plating, and by eliminating or substantially eliminating the shrinkage variation typically associated with surface metallization techniques.

Claims

1. A method of manufacturing a ceramic substrate, comprising the steps of:

(a) forming at least three unfired ceramic layers from green tape or an equivalent material, wherein at least one of the at least three unfired ceramic layers is an internal layer, and wherein two of the at least three unfired ceramic layers are first and second external layers, the first external layer forming an external upper surface of the substrate, the second external layer forming an external lower surface of the substrate;

(b) forming via holes in the at least one internal layer and in at least one of the external layers;

(c) filling the via holes of the at least one internal layer with an internal via paste;

(d) filling the via holes of at least one of the external layers with an external via paste, the external via paste having no tungsten or molybdenum therein, the external via paste comprising ceramic powder and at least one metal selected from the group consisting of palladium, platinum, osmium, iridium, technetium, rhenium, rhodium and ruthenium, and alloys, mixtures and combinations thereof;

(e) applying an internal paste to at least one of an upper surface and a lower surface of at least one internal layer to form at least one internal metallization circuitry pattern thereon;

(f) stacking the at least one internal layer and the external layers such that the at least one internal layer is interposed between the upper external layer and the lower external layer to form an unfired stacked ceramic substrate;

(g) laminating the unfired, stacked ceramic substrate to form an unfired, laminated ceramic substrate having only external vias exposed on the upper and lower surfaces thereof;

(h) trimming the laminated ceramic substrate to form an unfired, trimmed, ceramic substrate;

(i) firing, at high temperatures and in a reducing atmosphere, the trimmed ceramic substrate in a high-temperature firing step to form a high-temperature fired ceramic substrate;

(j) applying to at least one of the upper external surface and the lower external surface at least one thick film external surface metallization circuitry pattern to form a high-temperature fired ceramic substrate having at least one thick film external surface metallization circuitry pattern applied thereon;

(k) firing, at low temperatures and in an inert atmosphere, the high-temperature fired ceramic substrate to form a low-temperature fired ceramic substrate, and

(l) firing, at low temperatures and in an air atmosphere, the low-temperature fired ceramic substrate to form an air-fired ceramic substrate.

2. The method of claim 1, comprising the further step of incorporating the substrate into an implantable medical device.

3. The method of claim 1, wherein the internal via paste employed in the step of filling the via holes of the at least one internal layer comprises at least one metal selected from the group consisting of iridium, molybdenum, osmium, palladium, platinum, rhenium, rhodium, ruthenium, technetium, tungsten, and alloys, mixtures or combinations thereof, and about 30% by weight or less pre-milled, high-temperature ceramic powder.

4. The method of claim 1, wherein the external via paste employed in the step of filling the via holes of the at least one external layer comprises at least about 70% by weight ruthenium refractory powder and about 30% by weight or less pre-milled, high-temperature ceramic powder.

5. The method of claim 1, wherein the external via paste employed in the step of filling the via holes of the at least one external layer comprises at least one metal selected from the group consisting of palladium, platinum, osmium, iridium, technetium, rhenium, rhodium and ruthenium, and alloys, mixtures and combinations thereof, and about 30% by weight or less pre-milled, high-temperature ceramic powder.

6. The method of claim 1, -wherein the duration of the peak temperature portion of the high-temperature firing step ranges between about 1 hour and about 5 hours.

7. The method of claim 1, wherein the duration of the peak temperature portion of the high-temperature firing step ranges between about 5 minutes and about 8 hours.

8. The method of claim 1, wherein the peak temperature of the high-temperature firing step is between about 1400°

C. and about 1800°

C.

9. The method of claim 1, wherein the peak temperature of the high-temperature firing step is between about 1500°

C. and about 1700°

C.

10. The method of claim 1, wherein after the high-temperature firing step but before the low-temperature firing step, a first external paste is applied on at least the upper surface of the substrate or the lower surface of the substrate to form at least one first external metallization layer or circuitry pattern thereon.

11. The method of claim 10, wherein after the low-temperature firing step but before the air firing step a second external paste is applied on at least the upper surface of the substrate or the lower surface of the substrate to form at least one second external metallization layer or circuitry pattern thereon.

12. The method of claim 1, wherein the inert atmosphere of the low-temperature firing step is provided by at least one of nitrogen gas, argon gas, carbon dioxide gas, helium gas, or a vacuum.

13. The method of claim 1, wherein the reducing atmosphere of the high-temperature firing step is provided by at least one of hydrogen gas, nitrogen gas, or any gas or mixture of gases capable of providing the reducing atmosphere, wherein electrons are readily provided to the ceramic substrate during the high-temperature firing step.

14. The method of claim 1, wherein the duration of the peak temperature portion of the low-temperature firing step ranges between about 15 seconds and about 20 minutes.

15. The method of claim 1, wherein the duration of the peak temperature portion of the low-temperature firing step ranges between about 2 minutes and about 8 minutes.

16. The method of claim 1, wherein the peak temperature of the low-temperature firing step ranges between about 700°

C. and about 900°

C.

17. The method of claim 1, wherein the peak temperature of the low-temperature firing step ranges between about 600°

C. and about 1000°

C.

18. The method of claim 1, wherein the duration of the peak temperature portion of the air-firing step ranges between about 4 minutes and about 3 hours.

19. The method of claim 1, wherein the peak temperature portion of the air firing step has a duration ranging between about 10 minutes and about 2 hours.

20. The method of claim 1, wherein the peak temperature portion of the air-firing step ranges between about 600°

C. and about 1000°

C.

21. The method of claim 1, wherein the peak temperature portion of the air-firing step ranges between about 800°

C. and about 900°

C.

22. A method of manufacturing a ceramic substrate, the substrate having at least three layers, at least one of the at least three layers being an internal layer, two of the at least three layers being first and second external layers, the first external layer forming an external upper surface of the substrate, the second external layer forming an external lower surface of the substrate, comprising the steps of:

(a) firing, at high temperatures and in a reducing atmosphere, the ceramic substrate in a high-temperature firing step to form a high-temperature fired ceramic substrate;

(b) applying to at least one of the upper external surface and the lower external surface at least one thick film external surface metallization circuitry pattern to form a high-temperature fired ceramic substrate having at least one thick film external surface metallization circuitry pattern applied thereon;

(c) firing, at low temperatures and in an inert atmosphere, the high-temperature fired ceramic substrate to form a low-temperature fired ceramic substrate; and

(d) firing, at low temperatures and in an air atmosphere, the low-temperature fired ceramic substrate to form an air-fired ceramic substrate.

23. The method of claim 22, wherein the duration of the peak temperature portion of the high-temperature firing step ranges between about 5 minutes and about 8 hours.

24. The method of claim 22, wherein the duration of the peak temperature portion of the high-temperature firing step ranges between about 1 hour and about 5 hours.

25. The method of claim 22, wherein the peak temperature of the high-temperature firing step is between about 1400°

C. and about 1800°

C.

26. The method of claim 22, wherein the peak temperature of the high-temperature firing step is between about 1500°

C. and about 1700°

C.

27. The method of claim 22, wherein the duration of the peak temperature portion of the low-temperature firing step ranges between about 15 seconds and about 20 minutes.

28. The method of claim 22, wherein the duration of the peak temperature portion of the low-temperature firing step ranges between about 2 minutes and about 8 minutes.

29. The method of claim 22, wherein the peak temperature of the low-temperature firing step ranges between about 700°

C. and about 900°

C.

30. The method of claim 22, wherein the peak temperature of the low-temperature firing step ranges between about 600°

C. and about 1000°

C.

31. The method of claim 22, wherein the duration of the peak temperature portion of the air-firing step ranges between about 4 minutes and about 3 hours.

32. The method of claim 22, wherein the peak temperature portion of the air firing step has a duration ranging between about 10 minutes and about 2 hours.

33. The method of claim 22, wherein the peak temperature portion of the air-firing step ranges between about 600°

C. and about 1000°

C.

34. The method of claim 22, wherein the peak temperature portion of the air-firing step ranges between about 800°

C. and about 900°

C.

35. A method of manufacturing a ceramic substrate, comprising the steps of:

(a) forming at least three unfired ceramic layers from green tape or an equivalent material, wherein at least one of the at least three unfired ceramic layers is an internal layer, and wherein two of the at least three unfired ceramic layers are first and second external layers, the first external layer forming an external upper surface of the substrate, the second external layer forming an external lower surface of the substrate;

(b) forming via holes in the at least one internal layer and in at least one of the external layers;

(c) filling the via holes of the at least one internal layer with an internal via paste;

(d) filling the via holes of at least one of the external layers with an external via paste, the external via paste having no tungsten or molybdenum therein, the external via paste comprising ceramic powder and at least one metal selected from the group consisting of palladium, platinum, osmium, iridium, technetium, rhenium, rhodium and ruthenium, and alloys, mixtures and combinations thereof;

(e) stacking the at least one internal layer and the external layers such that the at least one internal layer is interposed between the upper external layer and the lower external layer to form an unfired stacked ceramic substrate;

(f) firing, at high temperatures and in a reducing atmosphere, the unfired stacked ceramic substrate in a high-temperature firing step to form a high-temperature fired ceramic substrate;

(g) applying to at least one of the upper external surface and the lower external surface at least one thick film external surface metallization circuitry pattern to form a high-temperature fired ceramic substrate having at least one thick film external surface metallization circuitry pattern applied thereon; and

(h) firing, at low temperatures and in an inert atmosphere, the high-temperature fired ceramic substrate to form a low-temperature fired ceramic substrate.

36. The method of claim 35, wherein the external via paste employed in the step of filling the via holes of the at least one external layer comprises at least about 70% by weight ruthenium refractory powder and about 30% by weight or less pre-milled, high-temperature ceramic powder.

37. The method of claim 35, wherein the external via paste employed in the step of filling the via holes of the at least one external layer comprises at least one metal selected from the group consisting of palladium, platinum, osmium, iridium, technetium, rhenium, rhodium and ruthenium, and alloys, mixtures and combinations thereof, and about 30% by weight or less pre-milled, high-temperature ceramic powder.

38. The method of claim 35, wherein the internal via paste employed in the step of filling the via holes of the at least one internal layer comprises at least one metal selected from the group consisting of iridium, molybdenum, osmium, palladium, platinum, rhenium, rhodium, ruthenium, technetium, tungsten, and alloys, mixtures or combinations thereof, and about 30% by weight or less pre-milled, high-temperature ceramic powder.

39. The method of claim 35, wherein the duration of the peak temperature portion of the high-temperature firing step ranges between about 5 minutes and about 8 hours.

40. The method of claim 35, wherein the duration of the peak temperature portion of the high-temperature firing step ranges between about 1 hour and about 5 hours.

41. The method of claim 35, wherein the peak temperature of the high-temperature firing step is between about 1400°

C. and about 1800°

C.

42. The method of claim 35, wherein the peak temperature of the high-temperature firing step is between about 1500°

C. and about 1700°

C.

43. The method of claim 35, wherein the duration of the peak temperature portion of the low-temperature firing step ranges between about 15 seconds and about 20 minutes.

44. The method of claim 35, wherein the duration of the peak temperature portion of the low-temperature firing step ranges between about 2 minutes and about 8 minutes.

45. The method of claim 35, wherein the peak temperature of the low-temperature firing step ranges between about 700°

C. and about 900°

C.

46. The method of claim 35, wherein the peak temperature of the low-temperature firing step ranges between about 600°

C. and about 1000°

C.

47. A method of manufacturing a ceramic substrate, comprising the steps of:

(a) forming at least three unfired ceramic layers from green tape or an equivalent material, wherein at least one of the at least three unfired ceramic layers is an internal layer, and wherein two of the at least three unfired ceramic layers are first and second external layers, the first external layer forming an external upper surface of the substrate, the second external layer forming an external lower surface of the substrate;

(b) forming via holes in the at least one internal layer and in at least one of the external layers;

(c) filling the via holes of the at least one internal layer with an internal via paste;

(d) filling the via holes of at least one of the external layers with an external via paste, the external via paste having no tungsten or molybdenum therein, the external via paste comprising ceramic powder and at least one metal selected from the group consisting of palladium, platinum, osmium, iridium, technetium, rhenium, rhodium and ruthenium, and alloys, mixtures and combinations thereof;

(e) stacking the at least one internal layer and the external layers such that the at least one internal layer is interposed between the upper external layer and the lower external layer to form an unfired stacked ceramic substrate;

(f) firing, at high temperatures and in a reducing atmosphere, the unfired stacked ceramic substrate in a high-temperature firing step to form a high-temperature fired ceramic substrate; and

(g) applying to at least one of the upper external surface and the lower external surface at least one thick film external surface metallization circuitry pattern to form a high-temperature fired ceramic substrate having at least one thick film external surface metallization circuitry pattern applied thereon.

48. The method of claim 47, wherein the external via paste employed in the step of filling the via holes of the at least one external layer comprises at least about 70% by weight ruthenium refractory powder and about 30% by weight or less pre-milled, high-temperature ceramic powder.

49. The method of claim 47, wherein the external via paste employed in the step of filling the via holes of the at least one external layer comprises at least one metal selected from the group consisting of palladium, platinum, osmium, iridium, technetium, rhenium, rhodium and ruthenium, and alloys, mixtures and combinations thereof, and about 30% by weight or less pre-milled, high-temperature ceramic powder.

50. The method of claim 47, wherein the internal via paste employed in the step of filling the via holes of the at least one internal layer comprises at least one metal selected from the group consisting of iridium, molybdenum, osmium, palladium, platinum, rhenium, rhodium, ruthenium, technetium, tungsten, and alloys, mixtures or combinations thereof, and about 30% by weight or less pre-milled, high-temperature ceramic powder.

51. The method of claim 47, wherein the duration of the peak temperature portion of the high-temperature firing step ranges between about 5 minutes and about 8 hours.

52. The method of claim 47, wherein the duration of the peak temperature portion of the high-temperature firing step ranges between about 1 hour and about 5 hours.

53. The method of claim 47, wherein the peak temperature of the high-temperature firing step is between about 1400°

C. and about 1800°

C.

54. The method of claim 47, wherein the peak temperature of the high-temperature firing step is between about 1500°

C. and about 1700°

C.

55. A method of manufacturing a ceramic substrate, the substrate having at least three layers, at least one of the at least three layers being an internal layer, two of the at least three layers being first and second external layers, the first external layer forming an external upper surface of the substrate, the second external layer forming an external lower surface of the substrate, comprising the steps of:

(a) firing, at high temperatures and in a reducing atmosphere, the ceramic substrate in a high-temperature firing step to form a high-temperature fired ceramic substrate;

(b) applying to at least one of the upper external surface and the lower external surface at least one thick film external surface metallization circuitry pattern to form a high-temperature fired ceramic substrate having at least one thick film external surface metallization circuitry pattern applied thereon;

(c) firing, at low temperatures and in an inert atmosphere, the high-temperature fired ceramic substrate to form a low-temperature fired ceramic substrate; and

(d) firing, at low temperatures and in an air atmosphere, the low-temperature fired ceramic substrate to form an air-fired ceramic substrate.

56. The method of claim 55, wherein the duration of the peak temperature portion of the high-temperature firing step ranges between about 5 minutes and about 8 hours.

57. The method of claim 55, wherein the duration of the peak temperature portion of the high-temperature firing step ranges between about 1 hour and about 5 hours.

58. The method of claim 55, wherein the peak temperature of the high-temperature firing step is between about 1400°

C. and about 1800°

C.

59. The method of claim 55, wherein the peak temperature of the high-temperature firing step is between about 1500°

C. and about 1700°

C.

60. The method of claim 55, wherein the duration of the peak temperature portion of the low-temperature firing step ranges between about 15 seconds and about 20 minutes.

61. The method of claim 55, wherein the duration of the peak temperature portion of the low-temperature firing step ranges between about 2 minutes and about 8 minutes.

62. The method of claim 55, wherein the peak temperature of the low-temperature firing step ranges between about 700°

C. and about 900°

C.

63. The method of claim 55, wherein the peak temperature of the low-temperature firing step ranges between about 600°

C. and about 1000°

C.

64. A method of manufacturing a ceramic substrate, the substrate having at least three layers, at least one of the at least three layers being an internal layer, two of the at least three layers being first and second external layers, the first external layer forming an external upper surface of the substrate, the second external layer forming an external lower surface of the substrate, comprising the steps of:

(a) firing, at high temperatures and in a reducing atmosphere, the ceramic substrate in a high-temperature firing step to form a high-temperature fired ceramic substrate;

(b) firing, at low temperatures and in an inert atmosphere, the high-temperature fired ceramic substrate to form a low-temperature fired ceramic substrate; and

(c) firing, at low temperatures and in an air atmosphere, the low-temperature fired ceramic substrate to form an air-fired ceramic substrate.

65. The method of claim 64, wherein the duration of the peak temperature portion of the high-temperature firing step ranges between about 1 hour and about 5 hours.

66. The method of claim 64, wherein the duration of the peak temperature portion of the high-temperature firing step ranges between about 5 minutes and about 8 hours.

67. The method of claim 64, wherein the peak temperature of the high-temperature firing step is between about 1400°

C. and about 1800°

C.

68. The method of claim 64, wherein the peak temperature of the high-temperature firing step is between about 1500°

C. and about 1700°

C.

69. The method of claim 64, wherein the duration of the peak temperature portion of the low-temperature firing step ranges between about 15 seconds and about 20 minutes.

70. The method of claim 64, wherein the duration of the peak temperature portion of the low-temperature firing step ranges between about 2 minutes and about 8 minutes.

71. The method of claim 64, wherein the peak temperature of the low-temperature firing step ranges between about 700°

C. and about 900°

C.

72. The method of claim 64, wherein the peak temperature of the low-temperature firing step ranges between about 600°

C. and about 1000°

C.

73. The method of claim 64, wherein the duration of the peak temperature portion of the air-firing step ranges between about 4 minutes and about 3 hours.

74. The method of claim 64, wherein the peak temperature portion of the air firing step has a duration ranging between about 10 minutes and about 2 hours.

75. The method of claim 64, wherein the peak temperature portion of the air-firing step ranges between about 600°

C. and about 1000°

C.

76. The method of claim 64, wherein the peak temperature portion of the air-firing step ranges between about 800°

C. and about 900°

C.

77. A method of manufacturing an unfired ceramic substrate, comprising the steps of:

(a) forming at least three unfired ceramic layers from green tape or an equivalent material, wherein at least one of the at least three unfired ceramic layers is an internal layer, and wherein two of the at least three unfired ceramic layers are first and second external layers, the first external layer forming an external upper surface of the substrate, the second external layer forming an external lower surface of the substrate;

(b) forming via holes in the at least one internal layer and in at least one of the external layers;

(c) filling the via holes of the at least one internal layer with an internal via paste; and

(d) filling the via holes of at least one of the external layers with an external via paste, the external via paste having no tungsten or molybdenum therein, the external via paste comprising ceramic powder and at least one metal selected from the group consisting of palladium, platinum, osmium, iridium, technetium, rhenium, rhodium and ruthenium, and alloys, mixtures and combinations thereof.

78. The method of claim 77, wherein the external via paste employed in the step of filling the via holes of the at least one external layer comprises at least about 70% by weight ruthenium refractory powder and about 30% by weight or less pre-milled, high-temperature ceramic powder.

79. The method of claim 77, wherein the external via paste employed in the step of filling the via holes of the at least one external layer comprises at least one metal selected from the group consisting of palladium, platinum, osmium, iridium, technetium, rhenium, rhodium and ruthenium, and alloys, mixtures and combinations thereof, and about 30% or less by weight pre-milled, high-temperature ceramic powder.

80. The method of claim 77, wherein the internal via paste employed in the step of filling the via holes of the at least one internal layer comprises at least one metal selected from the group consisting of iridium, molybdenum, osmium, palladium, platinum, rhenium, rhodium, ruthenium, technetium, tungsten, and alloys, mixtures or combinations thereof, and about 30% by weight or less pre-milled, high-temperature ceramic powder.

82. The method of claim 77 or 81, further comprising the step of applying an internal paste to at least one of an upper surface and a lower surface of at least one internal layer to form at least one internal metallization circuitry pattern thereon.

83. The method of claim 77 or 81, further comprising the step of laminating the ceramic substrate to form an unfired, laminated ceramic substrate having only external vias exposed on the upper and lower surfaces thereof.

84. The method of claim 77 or 81, further comprising the step of trimming the laminated ceramic substrate to form an unfired, trimmed, ceramic substrate.

85. The method of claim 77 or 81, further comprising the step of applying to at least one of the upper external surface and the lower external surface at least one thick film external surface metallization circuitry pattern to form a high-temperature fired ceramic substrate having at least one thick film external surface metallization circuitry pattern applied thereon.

86. The method of claim 77 or 81, further comprising the step of firing, at low temperatures and in an inert atmosphere, the high-temperature fired ceramic substrate to form a low-temperature fired ceramic substrate.

87. The method of claim 77 or 81, further comprising the step of firing, at low temperatures and in an air atmosphere, the low-temperature fired ceramic substrate to form an air-fired ceramic substrate.

81. A method of manufacturing a ceramic substrate, comprising the steps of:

(a) forming at least three unfired ceramic layers from green tape or an equivalent material, wherein at least one of the at least three unfired ceramic layers is an internal layer, and wherein two of the at least three unfired ceramic layers are first and second external layers, the first external layer forming an external upper surface of the substrate, the second external layer forming an external lower surface of the substrate;

(b) forming via holes in the at least one internal layer and in at least one of the external layers;

(c) filling the via holes of the at least one internal layer with an internal via paste;

(d) filling the via holes of at least one of the external layers with an external via paste, the external via paste having no tungsten or molybdenum therein, the external via paste comprising ceramic powder and at least one metal selected from the group consisting of palladium, platinum, osmium, iridium, technetium, rhenium, rhodium and ruthenium, and alloys, mixtures and combinations thereof;

(e) stacking the at least one internal layer and the external layers such that the at least one internal layer is interposed between the upper external layer and the lower external layer to form an unfired stacked ceramic substrate; and

(f) firing, at high temperatures and in a reducing atmosphere, the unfired ceramic substrate in a high-temperature firing step to form a high-temperature fired ceramic substrate.

88. A method of manufacturing a ceramic substrate, the substrate having at least three layers, at least one of the at least three layers being an internal layer, two of the at least three layers being first and second external layers, the first external layer forming an external upper surface of the substrate, the second external layer forming an external lower surface of the substrate, comprising the steps of:

(a) firing, at high temperatures and in a reducing atmosphere, the ceramic substrate in a high-temperature firing step to form a high-temperature fired ceramic substrate; and

(b) firing, at low temperatures and in an air atmosphere, the high-temperature fired ceramic substrate to form an air-fired ceramic substrate.

89. A method of implanting an implantable medical device containing a substrate, the substrate comprising at least three stacked, laminated and trimmed ceramic layers formed from green tape or an equivalent material, wherein at least one of the at least three ceramic layers is an internal layer, and wherein two of the at least three ceramic layers are first and second external layers, the first external layer forming an external upper surface of the substrate, the second external layer forming an external lower surface of the substrate, at least one internal via formed in the at least one internal layer, the internal via being formed from an internal via paste, at least one external via formed in at least one of the external layers, the external via being formed from an external via paste having no tungsten or molybdenum therein, the external via paste comprising ceramic powder and at least one metal selected from the group consisting of palladium, platinum, osmium, iridium, technetium, rhenium, rhodium and ruthenium, and alloys, mixtures and combinations thereof, at least one internal metallization circuitry pattern disposed on at least one of an upper surface and a lower surface of at least one internal layer and formed from an internal paste, wherein the unfired stacked, laminated and trimmed ceramic layers are fired in the ordered steps of:

(a) firing at high temperatures in a reducing atmosphere;

(b) firing at low temperatures in an inert atmosphere, and (c) firing at low temperatures in an air atmosphere to form the substrate, the substrate being disposed in, and forming an operative electronic component in the circuitry of, the implantable medical device, comprising the steps of;

(a) providing the implantable medical device;

(b) surgically implanting the medical device in one of a human being and a mammalian subject to effect electrical stimulation of an organ, organs or portion of the organ therein; and

(c) telemetrically, magnetically, electrically or manually enabling the implanted medical device so that it may electrically stimulate the organ, organs or portion of the organ.

90. The method of claim 89, wherein the implantable medical device provided is one of a pacemaker, a defibrillator, a PCD, an ICD, a neurological stimulator and a gastrointestinal stimulator.