Method for fabricating thick film alumina structures used in high frequency, low loss applications and a structure resulting therefrom

• US 20040251230A1
• Filed: 06/16/2003
• Published: 12/16/2004
• Est. Priority Date: 06/16/2003
• Status: Active Grant

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Friel, Kurt B., Ballard, Gregory A., Wardzala, Leonard J.
• Granted Patent: US 7,257,281 B2
• Time in Patent Office: Days
• US Class Current: 216/13
• CPC Class Codes: G02B 6/4228 Passive alignment, i.e. without a detection of the degree of coupling or the position of the elements G02B6/4234 takes precedence
• 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: 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 2203/1126 Firing, i.e. heating a powder or paste above the melting temperature of at least one of its constituents
• CPC Class Codes: H05K 3/1291 Firing or sintering at relative high temperatures for patterns on inorganic boards, e.g. co-firing of circuits on green ceramic sheets
• CPC Class Codes: H05K 3/321 by conductive adhesives
• CPC Class Codes: H05K 3/368 parallel to each other H05K3/361 takes precedence
• CPC Class Codes: Y10T 29/49812 Temporary protective coating, impregnation, or cast layer

Abstract

A method for fabricating thick film alumina structures used in high frequency, low loss applications is provided. More particularly, the invention is directed to a co-fire process for fabricating, or laminating, thick film structures to one another by printing a conductor layer between two thick film circuits, drying the layer, and co-firing the combined structure. This process is particularly useful in fabricating high frequency (e.g. 10 gigabit) fiber optic transmitters.

Claims

1. A method for fabricating high frequency, low loss structures, the method comprising steps of

fabricating circuit layers on a first side of a first ceramic substrate to obtain a first circuit subassembly;

fabricating other circuit layers on a first side of a second ceramic substrate to obtain a second circuit subassembly;

printing a first metal layer on selected portions of a second side of the first ceramic substrate;

drying the first metal layer;

printing a second metal layer on selected portions of a second side of the second ceramic substrate;

drying the second metal layer;

printing a third metal layer on the second metal layer;

aligning the first metal layer with the third metal layer;

placing the first circuit subassembly on the second circuit subassembly to form a resultant assembly based on the aligning;

drying the third metal layer; and

,

firing the resultant assembly.

2. The method as set forth in claim 1 wherein the first ceramic layer is fabricated of 96% alumina.

3. The method as set forth in claim 1 wherein the second ceramic layer is fabricated of 96% alumina.

4. The method as set forth in claim 1 wherein the fabricating of the circuit layers comprises steps of printing, drying and firing the circuit layers.

5. The method as set forth in claim 1 wherein the fabricating of the other circuit layers comprises steps of printing, drying and firing the other circuit layers.

6. The method as set forth in claim 1 wherein the first, second and third metal layers are fabricated of a platinum and silver alloy.

7. The method as set forth in claim 1 wherein the first, second and third metal layers are fabricated of silver.

8. The method as set forth in claim 1 wherein the first, second and third metal layers are fabricated of gold.

9. The method as set forth in claim 1 wherein the first, second and third metal layers are fabricated of a thick film cermet material.

10. The method as set forth in claim 9 wherein the cermet material has a firing range of 500°

Celsius to 950°

Celsius.

11. The method as set forth in claim 1 wherein the resultant assembly is a fiber optic transmitter.

12. The method as set forth in claim 1 wherein the resultant assembly includes a step.

13. A method for fabricating high frequency, low loss structures, the method comprising steps of:

printing a first metal layer on selected portions of a first ceramic substrate;

drying the first metal layer;

printing a second metal layer on selected portions of a second ceramic substrate;

drying the second metal layer;

printing a third metal layer on the second metal layer;

aligning the first metal layer with the third metal layer;

placing the first ceramic substrate on the second ceramic substrate to form a resultant assembly based on the aligning;

drying the third metal layer; and

,

firing the resultant assembly.

14. The method as set forth in claim 13 wherein the first, second and third metal layers are fabricated of a platinum and silver alloy.

15. The method as set forth in claim 13 wherein the first, second and third metal layers are fabricated of silver.

16. The method as set forth in claim 13 wherein the first, second and third metal layers are fabricated of gold.

17. The method as set forth in claim 13 wherein the first, second and third metal layers are fabricated of a thick film cermet material.

18. The method as set forth in claim 13 wherein the first, second and third metal layers are fabricated of gold.

19. The method as set forth in claim 13 wherein the first, second and third metal layers are fabricated of a thick film cermet material.

20. The method as set forth in claim 19 wherein the cermet material has a firing range of 500°

Celsius to 950°

Celsius.

21. The method as set forth in claim 13 wherein the resultant assembly is a fiber optic transmitter.

22. The method as set forth in claim 13 wherein the resultant assembly includes a step.

23. An apparatus comprising:

a first ceramic subassembly having a first circuit fabricated on a first side thereof; and

,

a second ceramic subassembly having a second circuit fabricated on a first side thereof,

wherein the first ceramic subassembly is joined to the second ceramic subassembly by metal layers that are selectively printed on one of a second side of the first ceramic subassembly and a second side of the second ceramic subassembly, dried and co-fired.

24. The apparatus as set forth in claim 23 wherein the apparatus is a fiber optic transmitter.

25. The apparatus as set forth in claim 23 wherein the metal layers are fabricated of a platinum and silver alloy.

26. The apparatus as set forth in claim 23 wherein the metal layers are fabricated of silver.

27. The apparatus as set forth in claim 23 wherein the metal layers are fabricated of gold.

28. The apparatus as set forth in claim 23 wherein the metal layers are fabricated of a thick film cermet material.

29. The apparatus as set forth in claim 23 wherein the metal layers are fabricated of gold.

30. The apparatus as set forth in claim 23 wherein the metal layers are fabricated of a thick film cermet material.

31. The apparatus as set forth in claim 30 wherein the cermet material has a firing range of 500°

Celsius to 950°

Celsius.

32. The apparatus as set forth in claim 23 wherein the first and second ceramic subassemblies are fabricated of 96% alumina.