US4045412A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Alumina substrate and method of manufacturing same
Assignee: Fujitsu Ltd
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Filing: 1975-07-14
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Granted: 1977-08-30
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Expires: 1995-07-14
Abstract
Abstract An improved alumina substrate comprising alumina and magnesium oxide has a surface finish of no more than 0.05 mu m CLA and a density of at least 3.90 g/cm3 in an as-fired condition and is composed of alumina grains which are sufficiently grown to have straight grain boundaries and flat surfaces to form a surface of the substrate. The improved substrate is produced by firing a green sheet having a high content of raw material powder and a density of more than 2.60 g/cm3 at a temperature of 1525 DEG to 1650 DEG C. The green sheet with high density is formed by the process of aggregating an organic agent and a high purity alumina powder by dry milling and casting the resultant slip.
Inventors
- 👤 Seiichi Yamada
- 👤 Kyohei Murakawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 20:10
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/01; C04B35/10; C04B35/111; H; H05; H05K; H05K1/00; H05K1/02; H05K1/03; H05K1/0306
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
226 words
A method of manufacturing an alumina substrate having a surface finish of no more than 0.05 μm center line average on at least one major surface and a density of at least 3.90 g/cm 3 in an as-fired condition, comprising the steps of: making an aggregated raw material powder by dry milling a mixture consisting of fine alumina particles, having high purity, and a grain growth inhibitor of 0.1 to 0.5 wt. %; producing a slip consisting of said aggregated raw material powder and an organic agent comprising a binder and a solvent; said solvent is provided to ensure that said raw material powder is uniformly dispersed in said slip; forming a solvent-free green sheet from said slip, having a high content of said raw material powder and a density of more than 2.60g/cm 3 , said step of forming including the step of subjecting said slip to a vacuum to eliminate bubbles and evaporate said solvent from said slip, followed by the step of shaping said solvent-free slip into a sheet and the further step of drying said sheet at room temperature; and firing said green sheet at a temperature in the range of 1525° C to 1650° C until said alumina particles in said fired sheet grow sufficiently to form straight boundaries and flat surfaces corresponding to said major surface of said alumina substrate.
Claim 2
Independent Claim
226 words
A method of manufacturing an alumina substrate having a surface finish of no more than 0.05 μm center line average on at least one major surface and a density of at least 3.90 g/cm 3 in an as-fired condition, comprising the steps of: making an aggregated raw material powder by dry milling a mixture consisting of fine alumina particles, having high purity, and a grain growth inhibitor of 0.1 to 0.5 wt. %; producing a slip consisting of said aggregated raw material powder and an organic agent comprising a binder and a solvent; said solvent is provided to ensure that said raw material powder is uniformly dispersed in said slip; forming a solvent-free green sheet from said slip, having a high content of said raw material powder and a density of more than 2.60g/cm 3 , said step of forming including the step of subjecting said slip to a vacuum to eliminate bubbles and evaporate said solvent from said slip, followed by the step of shaping said solvent-free slip into a sheet and the further step of drying said sheet at room temperature; and firing said green sheet at a temperature in the range of 1525° C to 1650° C until said alumina particles in said fired sheet grow sufficiently to form straight boundaries and flat surfaces corresponding to said major surface of said alumina substrate.
Claim 3
Dependent Claim
34 words
A method of manufacturing an alumina substrate as in claim 1 wherein said step of firing said green sheet is performed so that said alumina particles grow 3 to 8 times their normal size.
Claim 4
Dependent Claim
34 words
A method of manufacturing an alumina substrate as in claim 1, wherein said step of making an aggregated raw material by dry milling is performed for more than 10 hours with a ball mill.
Claim 5
Dependent Claim
28 words
A method of manufacturing an alumina substrate as in claim 1 wherein said raw material powder contains water which is regulated to be 0.3 to 3.0 wt. %.
Claim 6
Dependent Claim
33 words
A method of manufacturing an alumina substrate as in claim 1 wherein said step of making an aggregated raw material powder includes the step of using magnesium oxide as said grain growth inhibitor.
Claim 7
Dependent Claim
39 words
A method of manufacturing an alumina substrate as in claim 1 wherein said step of making an aggregated raw material powder includes the steps of supplying fine alumina particles which have an average size of less than 0.8 μm.
Claim 8
Dependent Claim
26 words
A method of manufacturing an alumina substrate as in claim 1 wherein said step of firing said green sheet is carried out in a hydrogen atmosphere.
Claim 9
Dependent Claim
24 words
A method of manufacturing an alumina substrate as in claim 1 wherein said step of firing said green sheet is carried out in air.
Claim 10
Dependent Claim
60 words
A method of manufacturing an alumina substrate as in claim 1 wherein said step of producing a slip consisting of said aggregated raw material powder and an organic agent includes providing an organic agent comprising a binder of polyvinyl butyral, a plasticizer of dibuthyl phthalate, a deflocculent of sorbitan trioleate and a solvent of methyl ethyl ketone, methanol and buthanol.
Claim 11
Dependent Claim
33 words
A method of manufacturing an alumina substrate as in claim 9, wherein said step of making an aggregated raw material powder by dry milling is performed for 40 hours with a ball mill.
Claim 12
Dependent Claim
29 words
A method of manufacturing an alumina substrate as in claim 10 wherein said step of producing a slip includes milling said aggregated raw material powder and said organic agent.
Claim 13
Dependent Claim
34 words
A method of manufacturing an alumina substrate as in claim 11 wherein said step of producing a slip includes milling said aggregated raw material powder and said organic agent for more than 100 hours.
Claim 14
Dependent Claim
33 words
A method of manufacturing an alumina substrate as in claim 11 wherein said step of producing a slip includes milling said aggregated raw material powder and said organic agent for about 120 hours.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-08-29 | 1981-02-28 | 1981-08-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-08-29 | 1985-02-28 | 1985-08-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-08-29 | 1989-02-28 | 1989-08-30 | $7700.00 | Window Closed / Lapsed |