US5073180A
Expired / Lapsed
US
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Method for forming sealed co-fired glass ceramic structures
Assignee: International Business Machines Corp
•
Filing: 1991-03-20
•
Granted: 1991-12-17
•
Expires: 2011-03-20
Abstract
Abstract A method for forming a co-fired glass ceramic structure including the steps of: forming at least one green sheet of a first crystallizable glass in a thermally decomposable binder; metallizing the green sheet with a pattern of conductive paste including conductive metal, a second crystallizable glass and a thermally decomposable binder, the pattern including at least one via; firing the green sheet according to the following firing cycle steps: a. preheating the green sheet to a first temperature in a furnace with a neutral or reducing ambient so as to effect pyrolysis of the thermally decomposable binders, wherein the first temperature is insufficient to coalesce the first crystallizable glass or the conductive paste; b. introducing a steam ambient into the furnace and then heating the green sheet in the furnace at the first temperature to burn off the pyrolyzed binders; c. replacing the steam ambient with a neutral or reducing ambient and raising the temperature to a second temperature to effect densification and crystallization of the first and second glasses; d. maintaining the second temperature for a predetermined time to effect sealing of the at least one via wherein for a first portion of the predetermined time, the ambient in said furnace is a neutral or reducing ambient and for a second portion of the predetermined time, the neutral or reducing ambient is replaced with a steam ambient; and e. cooling the structure.
Inventors
- 👤 Shaji Farooq
- 👤 Govindarajan Natarajan
- 👤 Srinivasa S. N. Reddy
- 👤 Richard A. Shelleman
- 👤 Nancy C. Stoffel
- 👤 Rao V. Vallabhaneni
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 14:19
CPC Classifications
H; H05; H05K; H05K3/00; H05K3/46; H05K3/4611; H05K3/4626; H05K3/4629; B; B32; B32B; B32B18/00; C; C04; C04B; C04B35/00; C04B35/01; C04B35/16; C04B35/18; C04B35/195; C04B35/622; C04B35/626; C04B35/63; C04B35/638; C04B2235/00; C04B2235/02; C04B2235/30; C04B2235/32; C04B2235/3205; C04B2235/3206; C04B2235/34; C04B2235/3409; C04B2235/65; C04B2235/652; C04B2235/656; C04B2235/6562; C04B2235/6565; C04B2235/6567; C04B2235/658; C04B2235/6582; C04B2235/6588; C04B2235/66; C04B2235/661; C04B2237/00; C04B2237/30; C04B2237/32; C04B2237/34; C04B2237/341; C04B2237/50; C04B2237/70; C04B2237/704; H05K1/00; H05K1/02; H05K1/03; H05K1/0306; H05K1/09; H05K1/092; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49117; Y10T29/49124; Y10T29/49126; Y10T29/49155; Y10T29/49163
Claims Analysis
Total Claims: 63
Claim 1
Independent Claim
233 words
A method for forming a co-fired glass ceramic structure comprising the steps of: forming at least one green sheet of a first crystallizable glass in a thermally decomposable binder; metallizing said green sheet with a pattern of conductive paste comprising conductive metal, a second crystallizable glass and a thermally decomposable binder, said pattern comprising at least one via; firing said green sheet according to the following firing cycle steps: a. preheating said green sheet to a first temperature in a furnace with a neutral or reducing ambient so as to effect pyrolysis of said thermally decomposable binders, wherein said first temperature is insufficient to coalesce said first crystallizable glass or said conductive paste; b. introducing a steam ambient into said furnace and then heating said green sheet in said furnace at said first temperature to burn off said pyrolyzed binders; c. replacing said steam ambient with a neutral or reducing ambient and raising the temperature to a second temperature to effect densification and crystallization of said first and second glasses; d. maintaining said second temperature for a predetermined time to effect sealing of said at least one via wherein for a first portion of said predetermined time, the ambient in said furnace is a neutral or reducing ambient and for a second portion of said predetermined time, the neutral or reducing ambient is replaced with a steam ambient; and e. cooling said structure.
Claim 2
Independent Claim
233 words
A method for forming a co-fired glass ceramic structure comprising the steps of: forming at least one green sheet of a first crystallizable glass in a thermally decomposable binder; metallizing said green sheet with a pattern of conductive paste comprising conductive metal, a second crystallizable glass and a thermally decomposable binder, said pattern comprising at least one via; firing said green sheet according to the following firing cycle steps: a. preheating said green sheet to a first temperature in a furnace with a neutral or reducing ambient so as to effect pyrolysis of said thermally decomposable binders, wherein said first temperature is insufficient to coalesce said first crystallizable glass or said conductive paste; b. introducing a steam ambient into said furnace and then heating said green sheet in said furnace at said first temperature to burn off said pyrolyzed binders; c. replacing said steam ambient with a neutral or reducing ambient and raising the temperature to a second temperature to effect densification and crystallization of said first and second glasses; d. maintaining said second temperature for a predetermined time to effect sealing of said at least one via wherein for a first portion of said predetermined time, the ambient in said furnace is a neutral or reducing ambient and for a second portion of said predetermined time, the neutral or reducing ambient is replaced with a steam ambient; and e. cooling said structure.
Claim 3
Dependent Claim
43 words
The method of claim 1 further comprising the step, prior to cooling, of raising the temperature while in said steam ambient in step d. to a final temperature and holding at said final temperature to effect recrystallization of said first and second glasses.
Claim 4
Dependent Claim
24 words
The method of claim 1 wherein said second temperature is a final temperature at which recrystallization of said first and second glasses is effected.
Claim 5
Dependent Claim
27 words
The method of claim 1 wherein said conductive paste, after firing, comprises 30 to 50 volume percent conductive metal and 70 to 50 volume percent glass ceramic.
Claim 6
Dependent Claim
27 words
The method of claim 4 wherein said conductive paste, after firing, comprises 35 to 45 volume percent conductive metal and 65 to 55 volume percent glass ceramic.
Claim 7
Dependent Claim
23 words
The method of claim 5 wherein said conductive paste, after firing, comprises 40 volume percent conductive metal and 60 volume percent glass ceramic.
Claim 8
Dependent Claim
17 words
The method of claim 4 wherein said conductive metal comprises copper and said glass ceramic comprises cordierite.
Claim 9
Dependent Claim
42 words
The method of claim 1 wherein the step of cooling comprises first cooling the structure to a temperature less than said second temperature in a steam ambient and then replacing the steam ambient with a neutral ambient and cooling to room temperature.
Claim 10
Dependent Claim
23 words
The method of claim 8 wherein said temperature less than said second temperature is in the range of 900 to 400 degrees Centigrade.
Claim 11
Dependent Claim
13 words
The method of claim 8 wherein said neutral ambient consists essentially of nitrogen.
Claim 12
Dependent Claim
16 words
The method of claim 2 wherein said final temperature is insufficient to melt said conductive metal.
Claim 13
Dependent Claim
16 words
The method of claim 3 wherein said final temperature is insufficient to melt said conductive metal.
Claim 14
Dependent Claim
14 words
The method of claim 1 wherein said first and second crystallizable glasses comprise cordierite.
Claim 15
Dependent Claim
26 words
The method of claim 1 wherein the TCE of said first crystallizable glass is equal to or greater than the TCE of said second crystallizable glass.
Claim 16
Dependent Claim
32 words
The method of claim 1 wherein the ratio of H 2 /H 2 O in said steam ambient of said binder burnoff step is maintained between 5×10 -5 and 2×10 -3 .
Claim 17
Dependent Claim
31 words
The method of claim 1 wherein the ratio of H 2 /H 2 O in said steam ambient at said second temperature is slightly oxidizing with respect to said conductive metal.
Claim 18
Dependent Claim
48 words
The method of claim 1 further comprising a drying step interposed between said binder burnoff and densification steps, said drying step comprising exposing said structure to a reducing ambient for a predetermined length of time at an elevated temperature that is insufficient to effect densification of said structure.
Claim 19
Dependent Claim
41 words
The method of claim 1 wherein the composition of said first crystallizable glass comprises, in weight percent, 55% SiO 2 , 21.1% Al 2 O 3 , 22.3% MgO, 1.3% B 2 O 3 and 0.3% P 2 O 5 .
Claim 20
Dependent Claim
21 words
The method of claim 1 wherein the composition of said second crystallizable glass is the same as said first crystallizable glass.
Claim 21
Dependent Claim
41 words
The method of claim 1 wherein the composition of said second crystallizable glass comprises, in weight percent, 55% SiO 2 , 21.23% Al 2 O 3 , 20% MgO, 1% B 2 O 3 and 2.77% P 2 O 5 .
Claim 22
Dependent Claim
19 words
The method of claim 1 wherein said first temperature is in the range of 690 to 750 degrees Centigrade.
Claim 23
Dependent Claim
19 words
The method of claim 1 wherein said second temperature is in the range of 900 to 1000 degrees Centigrade.
Claim 24
Dependent Claim
56 words
The method of claim 1 wherein there are a plurality of said green sheets and further comprising the steps of: metallizing at least one of said green sheets with a pattern of conductive paste comprising conductive metal, a thermally decomposable binder and no crystallizable glass; and prior to firing, stacking and laminating said metallized green sheets.
Claim 25
Dependent Claim
87 words
The method of claim 23 wherein there are a plurality of metallized green sheets having the conductive paste without the crystallizable glass and at least one metallized green sheet having the conductive paste with the crystallizable glass, the metallized green sheets being stacked such that the metallized green sheets having the conductive paste without the crystallizable glass are stacked together and the at least one metallized green sheet having the conductive paste with the crystallizable glass is placed either at the top or bottom of the stack.
Claim 26
Dependent Claim
88 words
The method of claim 23 wherein there are a plurality of metallized green sheets having the conductive paste without the crystallizable glass and a plurality of metallized green sheets having the conductive paste with the crystallizable glass, the metallized green sheets being stacked such that the metallized green sheets having the conductive paste without the crystallizable glass are stacked together and at least one each of the metallized green sheets having the conductive paste with the crystallizable glass is placed at the top and bottom of the stack.
Claim 27
Dependent Claim
58 words
The method of claim 1, prior to the step of metallizing, further comprising the step of forming the conductive metal of the conductive paste comprising mixing particles of CuO with particles of the second crystallizable glass and then exposing the mixture of particles to a reducing atmosphere for a time sufficient to reduce the CuO to elemental copper.
Claim 28
Dependent Claim
19 words
The method of claim 26 wherein said CuO particles have a particle size of about 2 microns or less.
Claim 29
Dependent Claim
26 words
The method of claim 26 wherein the exposing of the mixture of particles is in hydrogen at an elevated temperature less than about 600 degrees Centigrade.
Claim 30
Dependent Claim
15 words
The method of claim 1 wherein the ambient of step c is a reducing ambient.
Claim 31
Dependent Claim
19 words
The method of claim 1 wherein the ambient in the first portion of step d is a neutral ambient.
Claim 32
Independent Claim
232 words
A method for forming a co-fired glass ceramic structure comprising at least one metallized green sheet of a first crystallizable glass in a thermally decomposable binder having a pattern of conductive paste comprising conductive metal, a second crystallizable glass and a thermally decomposable binder, said pattern comprising at least one via, the method comprising the steps of: firing said green sheet according to the following firing cycle steps: a. preheating said green sheet to a first temperature in a furnace with a neutral or reducing ambient so as to effect pyrolysis of said thermally decomposable binders, wherein said first temperature is insufficient to coalesce said first crystallizable glass or said conductive paste; b. introducing a steam ambient into said furnace and then heating said green sheet in said furnace at said first temperature to burn off said pyrolyzed binders; c. replacing said steam ambient with a neutral or reducing ambient and raising the temperature to a second temperature to effect densification and crystallization of said first and second glasses; d. maintaining said second temperature for a predetermined time to effect sealing of said at least one via wherein for a first portion of said predetermined time, the ambient in said furnace is a neutral or reducing ambient and for a second portion of said predetermined time, the neutral or reducing ambient is replaced with a steam ambient; and e. cooling said structure.
Claim 33
Independent Claim
232 words
A method for forming a co-fired glass ceramic structure comprising at least one metallized green sheet of a first crystallizable glass in a thermally decomposable binder having a pattern of conductive paste comprising conductive metal, a second crystallizable glass and a thermally decomposable binder, said pattern comprising at least one via, the method comprising the steps of: firing said green sheet according to the following firing cycle steps: a. preheating said green sheet to a first temperature in a furnace with a neutral or reducing ambient so as to effect pyrolysis of said thermally decomposable binders, wherein said first temperature is insufficient to coalesce said first crystallizable glass or said conductive paste; b. introducing a steam ambient into said furnace and then heating said green sheet in said furnace at said first temperature to burn off said pyrolyzed binders; c. replacing said steam ambient with a neutral or reducing ambient and raising the temperature to a second temperature to effect densification and crystallization of said first and second glasses; d. maintaining said second temperature for a predetermined time to effect sealing of said at least one via wherein for a first portion of said predetermined time, the ambient in said furnace is a neutral or reducing ambient and for a second portion of said predetermined time, the neutral or reducing ambient is replaced with a steam ambient; and e. cooling said structure.
Claim 34
Dependent Claim
43 words
The method of claim 31 further comprising the step, prior to cooling, of raising the temperature while in said steam ambient in step d to a final temperature and holding at said final temperature to effect recrystallization of said first and second glasses.
Claim 35
Dependent Claim
24 words
The method of claim 31 wherein said second temperature is a final temperature at which recrystallization of said first and second glasses is effected.
Claim 36
Dependent Claim
27 words
The method of claim 31 wherein said conductive paste, after firing, comprises 30 to 50 volume percent conductive metal and 70 to 50 volume percent glass ceramic.
Claim 37
Dependent Claim
27 words
The method of claim 34 wherein said conductive paste, after firing, comprises 35 to 45 volume percent conductive metal and 65 to 55 volume percent glass ceramic.
Claim 38
Dependent Claim
23 words
The method of claim 35 wherein said conductive paste, after firing, comprises 40 volume percent conductive metal and 60 volume percent glass ceramic.
Claim 39
Dependent Claim
17 words
The method of claim 34 wherein said conductive metal comprises copper and said glass ceramic comprises cordierite.
Claim 40
Dependent Claim
42 words
The method of claim 31 wherein the step of cooling comprises first cooling the structure to a temperature less than said second temperature in a steam ambient and then replacing the steam ambient with a neutral ambient and cooling to room temperature.
Claim 41
Dependent Claim
23 words
The method of claim 38 wherein said temperature less than said final temperature is in the range of 900 to 400 degrees Centigrade.
Claim 42
Dependent Claim
13 words
The method of claim 38 wherein said neutral ambient consists essentially of nitrogen.
Claim 43
Dependent Claim
16 words
The method of claim 32 wherein said final temperature is insufficient to melt said conductive metal.
Claim 44
Dependent Claim
16 words
The method of claim 33 wherein said final temperature is insufficient to melt said conductive metal.
Claim 45
Dependent Claim
14 words
The method of claim 31 wherein said first and second crystallizable glasses comprise cordierite.
Claim 46
Dependent Claim
26 words
The method of claim 31 wherein the TCE of said first crystallizable glass is equal to or greater than the TCE of said second crystallizable glass.
Claim 47
Dependent Claim
32 words
The method of claim 31 wherein the ratio of H 2 /H 2 O in said steam ambient of said binder burnoff step is maintained between 5×10 -5 and 2×10 -3 .
Claim 48
Dependent Claim
31 words
The method of claim 31 wherein the ratio of H 2 /H 2 O in said steam ambient at said second temperature is slightly oxidizing with respect to said conductive metal.
Claim 49
Dependent Claim
48 words
The method of claim 31 further comprising a drying step interposed between said binder burnoff and densification steps, said drying step comprising exposing said structure to a reducing ambient for a predetermined length of time at an elevated temperature that is insufficient to effect densification of said structure.
Claim 50
Dependent Claim
40 words
The method of claim 31 wherein the composition of said first crystallizable glass comprises in weight percent, 55% SiO 2 , 21.1% Al 2 O 3 22.3% MgO, 1.3% B 2 O 3 and 0.3% P 2 O 5 .
Claim 51
Dependent Claim
21 words
The method of claim 31 wherein the composition of said second crystallizable glass is the same as said first crystallizable glass.
Claim 52
Dependent Claim
41 words
The method of claim 31 wherein the composition of said second crystallizable glass comprises, in weight percent, 55% SiO 2 , 21.23% Al 2 O 3 , 20% MgO, 1% B 2 O 3 and 2.77% P 2 O 5 .
Claim 53
Dependent Claim
19 words
The method of claim 31 wherein said first temperature is in the range of 690 to 750 degrees Centigrade.
Claim 54
Dependent Claim
19 words
The method of claim 31 wherein said second temperature is in the range of 900 to 1000 degrees Centigrade.
Claim 55
Dependent Claim
15 words
The method of claim 31 wherein the ambient of step c is a reducing ambient.
Claim 56
Dependent Claim
19 words
The method of claim 31 wherein the ambient in the first portion of step d is a neutral ambient.
Claim 57
Independent Claim
269 words
A method for forming a co-fired glass ceramic structure comprising a plurality of stacked and laminated metallized green sheets of a first crystallizable glass in a thermally decomposable binder, at least one of the metallized green sheets having a pattern of conductive paste comprising conductive metal, a second crystallizable glass and a thermally decomposable binder, said pattern comprising at least one via, and at least one of the metallized green sheets having a pattern of conductive paste comprising conductive metal, a thermally decomposable binder and no crystallizable glass, the method comprising the steps of: firing said green sheets according to the following firing cycle steps: a. preheating said green sheets to a first temperature in a furnace with a neutral or reducing ambient so as to effect pyrolysis of said thermally decomposable binders, wherein said first temperature is insufficient to coalesce said first crystallizable glass or said conductive paste; b. introducing a steam ambient into said furnace and then heating said green sheets in said furnace at said first temperature to burn off said pyrolyzed binders; c. replacing said steam ambient with a neutral of reducing ambient and raising the temperature to a second temperature to effect densification and crystallization of said first and second glasses; d. maintaining said second temperature for a predetermined time to effect sealing of said at least one via wherein for a first portion of said predetermined time, the ambient in said furnace is a neutral or reducing ambient and for a second portion of said predetermined time, the neutral or reducing ambient is replaced with a steam ambient; and e. cooling said structure.
Claim 58
Independent Claim
269 words
A method for forming a co-fired glass ceramic structure comprising a plurality of stacked and laminated metallized green sheets of a first crystallizable glass in a thermally decomposable binder, at least one of the metallized green sheets having a pattern of conductive paste comprising conductive metal, a second crystallizable glass and a thermally decomposable binder, said pattern comprising at least one via, and at least one of the metallized green sheets having a pattern of conductive paste comprising conductive metal, a thermally decomposable binder and no crystallizable glass, the method comprising the steps of: firing said green sheets according to the following firing cycle steps: a. preheating said green sheets to a first temperature in a furnace with a neutral or reducing ambient so as to effect pyrolysis of said thermally decomposable binders, wherein said first temperature is insufficient to coalesce said first crystallizable glass or said conductive paste; b. introducing a steam ambient into said furnace and then heating said green sheets in said furnace at said first temperature to burn off said pyrolyzed binders; c. replacing said steam ambient with a neutral of reducing ambient and raising the temperature to a second temperature to effect densification and crystallization of said first and second glasses; d. maintaining said second temperature for a predetermined time to effect sealing of said at least one via wherein for a first portion of said predetermined time, the ambient in said furnace is a neutral or reducing ambient and for a second portion of said predetermined time, the neutral or reducing ambient is replaced with a steam ambient; and e. cooling said structure.
Claim 59
Dependent Claim
43 words
The method of claim 55 further comprising the step, prior to cooling, of raising the temperature while in said steam ambient in step d to a final temperature and holding at said final temperature to effect recrystallization of said first and second glasses.
Claim 60
Dependent Claim
24 words
The method of claim 55 wherein said second temperature is a final temperature at which recrystallization of said first and second glasses is effected.
Claim 61
Dependent Claim
18 words
The method of claim 51 wherein said steam ambient is slightly oxidizing with respect to said conductive metal.
Claim 62
Dependent Claim
15 words
The method of claim 55 wherein the ambient of step c is a reducing ambient.
Claim 63
Dependent Claim
19 words
The method of claim 55 wherein the ambient in the first portion of step d is a neutral ambient.
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