US20070237480A1 - Method for fabricating thick film alumina structures used in high frequency, low loss applications and a structure resulting therefrom - Google Patents
Method for fabricating thick film alumina structures used in high frequency, low loss applications and a structure resulting therefrom Download PDFInfo
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- US20070237480A1 US20070237480A1 US11/709,331 US70933107A US2007237480A1 US 20070237480 A1 US20070237480 A1 US 20070237480A1 US 70933107 A US70933107 A US 70933107A US 2007237480 A1 US2007237480 A1 US 2007237480A1
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/36—Assembling printed circuits with other printed circuits
- H05K3/368—Assembling printed circuits with other printed circuits parallel to each other
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4219—Mechanical fixtures for holding or positioning the elements relative to each other in the couplings; Alignment methods for the elements, e.g. measuring or observing methods especially used therefor
- G02B6/4228—Passive alignment, i.e. without a detection of the degree of coupling or the position of the elements
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/48—Manufacture or treatment of parts, e.g. containers, prior to assembly of the devices, using processes not provided for in a single one of the subgroups H01L21/06 - H01L21/326
- H01L21/4814—Conductive parts
- H01L21/4846—Leads on or in insulating or insulated substrates, e.g. metallisation
- H01L21/4857—Multilayer substrates
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/48—Manufacture or treatment of parts, e.g. containers, prior to assembly of the devices, using processes not provided for in a single one of the subgroups H01L21/06 - H01L21/326
- H01L21/4814—Conductive parts
- H01L21/4846—Leads on or in insulating or insulated substrates, e.g. metallisation
- H01L21/4867—Applying pastes or inks, e.g. screen printing
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/03—Use of materials for the substrate
- H05K1/0306—Inorganic insulating substrates, e.g. ceramic, glass
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/09—Use of materials for the conductive, e.g. metallic pattern
- H05K1/092—Dispersed materials, e.g. conductive pastes or inks
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/11—Treatments characterised by their effect, e.g. heating, cooling, roughening
- H05K2203/1126—Firing, i.e. heating a powder or paste above the melting temperature of at least one of its constituents
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
- H05K3/12—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using thick film techniques, e.g. printing techniques to apply the conductive material or similar techniques for applying conductive paste or ink patterns
- H05K3/1283—After-treatment of the printed patterns, e.g. sintering or curing methods
- H05K3/1291—Firing or sintering at relative high temperatures for patterns on inorganic boards, e.g. co-firing of circuits on green ceramic sheets
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
- H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
- H05K3/321—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by conductive adhesives
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/4981—Utilizing transitory attached element or associated separate material
- Y10T29/49812—Temporary protective coating, impregnation, or cast layer
Definitions
- This invention relates to a method for fabricating thick film alumina structures used in high frequency, low loss applications and a structure resulting therefrom. 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.
- high frequency e.g. 10 gigabit
- thick film processes on 96% alumina processes
- LTCC low temperature co-fired ceramic
- thick film processes have many advantages over LTCC processes.
- thick film processes are traditionally conducted by established manufacturers with established supply chains. As such, there is lower cost in implementing these processes. From a performance standpoint, thick film processes result in lower loss for high frequency structures. In addition, thick film processes result in structures having greater thermal conductivity.
- thick film processes There are also disadvantages to the use of thick film processes. For multi-layer circuits used in high frequency applications, thick film processes result in poor performance of the structure. Additionally, since dielectrics can only be printed, thick film processes are limited to using a thin dielectric layer. The thin dielectric layer limits the types of high frequency structures that can actually be built.
- LTCC processes have advantages and disadvantages.
- LTCC processes have at least some performance advantages over other technologies; however, LTCC processes require a large capital investment on the part of the manufacturer.
- disadvantages in performance LTCC processes typically result in higher loss ratios than thick film technology for the structure fabricated.
- LTCC tape is typically not available in comparable alumina thickness, thereby requiring more layers of tape to realize an equivalent thickness in alumina.
- LTCC processes typically result in shrinkage of fabricated elements. This shrinkage is, of course, not desired and must be compensated for in the design.
- the present invention contemplates a new and improved process for fabricating thick film alumina structures used in high frequency, low loss applications that resolves the above-referenced difficulties and others.
- a method for fabricating thick film structures used in high frequency, low loss applications is provided.
- a useful structure results from the implementation of the method.
- the method comprises 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.
- the method comprises 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.
- an apparatus is fabricated using the method, the 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.
- the ceramic layers are fabricated of 96% alumina.
- the first, second and third metal layers are fabricated of a platinum and silver alloy.
- the first, second and third metal layers are fabricated of silver.
- the first, second and third metal layers are fabricated of gold.
- the first, second and third metal layers are fabricated of a thick film cermet material.
- the cermet material has a firing range of 500° Celsius to 950° Celsius.
- the resultant assembly is a fiber optic transmitter.
- the resultant assembly includes a step.
- FIG. 1 illustrates a cross-sectional view of a ceramic assembly or structure fabricated according to a method of the present invention
- FIGS. 2 ( a )-( c ) show a cross-sectional view of the steps for fabricating a subassembly according to the present invention
- FIGS. 3 ( a )-( c ) illustrate steps for fabricating a subassembly according to the present invention.
- FIGS. 4 ( a )-( c ) illustrate steps for fabricating the ceramic assembly according the present invention.
- FIG. 1 provides a view of an assembly fabricated according to a method of the present invention.
- the assembly shown may be useful in many high frequency, low loss environments; however, it finds particular application as a high frequency fiber optic transmitter, where low loss is a primary objective.
- a ceramic assembly 10 includes a first circuit subassembly 12 and a second circuit subassembly 14 .
- the first circuit subassembly 12 includes a first ceramic substrate 16 having a circuit portion, or circuit layers, 18 fabricated on a first side thereof.
- Metallization layer(s) 30 are also fabricated on a second side of the ceramic substrate 16 . It should be understood that the precise form or pattern of the metallization layer(s) 30 (as well as layers 32 and 40 ) will vary depending on the configuration of the ultimate structure. For example, it may be a single continuous layer, multiple layers, a discontinuous layer or separate portions of material applied in the same plane, as shown in FIG. 1 .
- the second circuit subassembly 14 includes a ceramic substrate 20 having a circuit portion, or circuit layers, 22 fabricated thereon.
- the circuit portion 22 is disposed on a first side of the ceramic substrate 20 .
- Metallization layers 32 are fabricated on a second side of the substrate, as shown.
- Metallization layer(s) 40 are disposed in a place between the layers 30 and 32 . It is to be understood that, as described below, the layer(s) 40 is preferably fabricated on the layer(s) 32 of the second subassembly 14 . However, it could be fabricated in other manners.
- a gap 50 exists between the first circuit subassembly 12 and the second circuit subassembly 14 .
- This gap may be of any dimension, and may well not even be pertinent to operation of the circuit assembly. Therefore, the gap 50 could be minimized to a negligible dimension, depending on the thickness of the metal layers 30 , 32 and 40 .
- the structure, or assembly, 10 that is shown in FIG. 1 is merely representative of a variety of structures that could be fabricated.
- the structure shown is relatively simply in character to illustrate the aspects of the present invention and should not be considered to be limiting in nature.
- the present invention is particularly useful to form a step 60 as representatively shown in FIG. 1 .
- more complex structures of this nature could be similarly fabricated using the present invention.
- wells, cavities, channels or multi-layer steps may be fabricated using the present invention.
- the ceramic substrate 16 and ceramic substrate 20 are preferably fabricated of 96% alumina, but could be fabricated of any suitable ceramic material.
- the circuit portions, or circuit layers, 18 and 22 can be fabricated on the appropriate sides of the substrates using a variety of methods.
- the circuit layers 18 and 22 are fabricated using a print, dry, and fire (PDF) process.
- PDF print, dry, and fire
- the printing portion of that process is preferably a screen printing process that can be accomplished in a number of manners that are accepted in the field.
- the drying process would include drying the material for a sufficient amount of time to prepare it for firing. Of course, firing the material should be accomplished over time intervals and in temperature ranges that are appropriate for the materials used in fabricating the circuit portions.
- any suitable material may be used for formation of the circuit portions.
- the metallization layers 30 , 32 and 40 are preferably fabricated of a platinum (Pt) and silver (Ag) alloy. It should be appreciated, however, that any suitable thick film cermet (ceramic-based metal material) conductor with a firing range of 500° C. to 950° C. may be used. There are a variety of industry standard conductor alloys that fall within this category of thick film metallization materials or conductors. For example, silver or gold could alternatively be used as the metallization layer. It should be appreciated, however, that for a particular structure being fabricated, it is preferred that all metal layers 30 , 32 and 40 have the same composition.
- the process for fabricating the assembly 10 of FIG. 1 can be accomplished by laminating, or joining, the two thick film circuit subassemblies 12 and 14 and selectively printing, drying and firing the structure.
- the process allows for formation of the structure without cracking the material.
- the resultant structure forms an excellent electrical connection and realizes a variety of other practical and performance-based advantages.
- the process does not require high capital investment.
- the fabricated assembly does not experience any shrinkage during processing as a result of implementation of the invention.
- the loss characteristics of the resultant assembly are favorable. Therefore, the resultant assembly is particularly suited for high frequency and low loss applications of thick film ceramic-based material.
- the present application is particularly suited to the formation of high frequency fiber optic transmitters.
- FIG. 2 a method for fabricating the first circuit subassembly 12 is shown.
- the process begins by obtaining a ceramic substrate 16 .
- the ceramic substrate is preferably fabricated of 96% alumina.
- circuit layers 18 are then fabricated on a first side of ceramic substrate 16 by any appropriate processes.
- a print, dry and fire (PDF) process is used to do so.
- PDF print, dry and fire
- the materials selected may vary but such materials should be of a nature to withstand the processes contemplated by the implementation of the present invention. It should also be understood that the circuit portion 18 may take a variety of forms and/or patterns.
- the metallization layer(s) 30 are fabricated on a second side of the substrate 16 by printing the metallization layer and allowing it to dry.
- the metallization layers are preferably printed by a suitable screen printing process. The drying period may vary from case to case. Notably, the metallization layers are not fired at this point.
- FIG. 3 a method for fabricating the second circuit subassembly 14 is illustrated.
- a ceramic substrate 20 is first obtained.
- the ceramic substrate is preferably fabricated of 96% alumina.
- FIG. 3 ( b ) illustrates that a circuit portion, or circuit layers, 22 is appropriately fabricated on a first side of the substrate 20 .
- the circuit layers 22 are fabricated using any known process; however, it is preferred that a circuit is fabricated using a print, dry and fire (PDF) process.
- PDF print, dry and fire
- the materials selected may vary but such materials should be of a nature to withstand the processes contemplated by the implementation of the present invention.
- the circuit portion 22 may take a variety of forms and/or patterns.
- metallization layer(s) 32 are fabricated on the other side of the substrate 20 .
- the metallization material may be any of a number of compositions; however, it should be the same as layer 30 .
- the layer(s) 32 are printed and permitted to dry.
- the metallization layers are preferably printed by a suitable screen printing process. The drying period may vary from case to case. Notably, the metallization layers are not fired at this point.
- the first circuit subassembly 12 and the second circuit subassembly 14 are then laminated, or joined together. More particularly, with reference to FIG. 4 ( a ), a metallization layer 40 is printed on the metallization layer 32 of the circuit subassembly 14 .
- the metallization layer 40 should be fabricated of the same material as layers 30 and 32 . Again, screen printing is preferred.
- the first circuit subassembly 12 is aligned, or fixtured, with the second circuit subassembly 14 . In doing so, the metallization layer(s) 30 are aligned with the metallization layers 40 , as shown. Any suitable alignment technique may be used to accomplish this objective. It should also be understood that the metallization layers 40 are not dried at this point in the process.
- the first circuit subassembly 12 and the second circuit subassembly 14 are laminated, or joined together, based on the alignment of FIG. 4 ( b ).
- the structure, particularly the metallization layers 40 is then permitted to dry and then fired, or co-fired, to obtain the final assembly 10 . Any appropriate drying and co-firing process may be implemented so that the metallization layers 30 , 32 and 40 form a sufficient bond for the resultant assembly.
- the assembly 10 includes the step 60 , as noted above.
- the drying and firing processes may vary from application to application.
- the precise time intervals and/or temperature ranges depend on the structures being formed and the materials.
- a sufficient drying period may depend on the amount of ventilation that can occur so that the vehicle (or liquid) for the paste (or printed material) sufficiently evacuates.
- the drying process is facilitated by providing vent holes in the ceramic structure.
- an 850° C. profile is preferably used; however, it should be understood that the firing of the structures is dependant on the material used.
- the process for fabricating a completed thick film ceramic assembly used as a circuit is illustrated. It should be appreciated the invention is not so limited, however.
- the processes for fabricating the circuit layers 18 and 22 are not necessary as described for implementation of the present invention. Structures other than circuit layers may be suitably formed on the ceramic substrate.
- the ceramic substrates are first bonded using the present invention. Subsequent processes may then be used to form circuit portions or other structures on appropriate sides of the substrates.
- applications using the present invention may not necessitate the formation of any additional circuit portions or other structures.
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.
Description
- This invention relates to a method for fabricating thick film alumina structures used in high frequency, low loss applications and a structure resulting therefrom. 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.
- While the invention is particularly directed to the art of fabricating thick film alumina structures used in high frequency, low loss applications, and will be thus described with specific reference thereto, it will be appreciated that the invention may have usefulness in other fields and applications. For example, principles of the invention may be used in any application where an alternative to LTCC (low temperature, co-fired ceramic) processes is desired.
- By way of background, within the ceramics industry, there are primarily two technologies used for fabricating multi-layer ceramic structures: thick film (on 96% alumina) processes and LTCC (low temperature co-fired ceramic) processes. Thick film processes have historically been the dominant technology.
- In this regard, thick film processes have many advantages over LTCC processes. For example, thick film processes are traditionally conducted by established manufacturers with established supply chains. As such, there is lower cost in implementing these processes. From a performance standpoint, thick film processes result in lower loss for high frequency structures. In addition, thick film processes result in structures having greater thermal conductivity.
- There are also disadvantages to the use of thick film processes. For multi-layer circuits used in high frequency applications, thick film processes result in poor performance of the structure. Additionally, since dielectrics can only be printed, thick film processes are limited to using a thin dielectric layer. The thin dielectric layer limits the types of high frequency structures that can actually be built.
- Likewise, LTCC processes have advantages and disadvantages. For example, LTCC processes have at least some performance advantages over other technologies; however, LTCC processes require a large capital investment on the part of the manufacturer. As to disadvantages in performance, LTCC processes typically result in higher loss ratios than thick film technology for the structure fabricated. Moreover, LTCC tape is typically not available in comparable alumina thickness, thereby requiring more layers of tape to realize an equivalent thickness in alumina. Still further, LTCC processes typically result in shrinkage of fabricated elements. This shrinkage is, of course, not desired and must be compensated for in the design.
- Accordingly, it is desirable to implement a process that realizes the benefits of both thick film processes and LTCC processes. However, no such process was heretofore available.
- The present invention contemplates a new and improved process for fabricating thick film alumina structures used in high frequency, low loss applications that resolves the above-referenced difficulties and others.
- A method for fabricating thick film structures used in high frequency, low loss applications is provided. A useful structure results from the implementation of the method.
- In one aspect of the invention, the method comprises 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.
- In another aspect of the invention, the method comprises 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.
- In another aspect of the invention, an apparatus is fabricated using the method, the 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.
- In another aspect of the invention, the ceramic layers are fabricated of 96% alumina.
- In another aspect of the invention, the first, second and third metal layers are fabricated of a platinum and silver alloy.
- In another aspect of the invention, the first, second and third metal layers are fabricated of silver.
- In another aspect of the invention, the first, second and third metal layers are fabricated of gold.
- In another aspect of the invention, the first, second and third metal layers are fabricated of a thick film cermet material.
- In another aspect of the invention, the cermet material has a firing range of 500° Celsius to 950° Celsius.
- In another aspect of the invention, the resultant assembly is a fiber optic transmitter.
- In another aspect of the invention, the resultant assembly includes a step.
- Further scope of the applicability of the present invention will become apparent from the detailed description provided below. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.
- The present invention exists in the construction, arrangement, and combination of the various parts of the device, and steps of the method, whereby the objects contemplated are attained as hereinafter more fully set forth, specifically pointed out in the claims, and illustrated in the accompanying drawings in which:
-
FIG. 1 illustrates a cross-sectional view of a ceramic assembly or structure fabricated according to a method of the present invention; - FIGS. 2 (a)-(c) show a cross-sectional view of the steps for fabricating a subassembly according to the present invention;
- FIGS. 3 (a)-(c) illustrate steps for fabricating a subassembly according to the present invention; and,
- FIGS. 4 (a)-(c) illustrate steps for fabricating the ceramic assembly according the present invention.
- Referring now to the drawings wherein the showings are for purposes of illustrating the preferred embodiments of the invention only and not for purposes of limiting same,
FIG. 1 provides a view of an assembly fabricated according to a method of the present invention. The assembly shown may be useful in many high frequency, low loss environments; however, it finds particular application as a high frequency fiber optic transmitter, where low loss is a primary objective. - As shown, a
ceramic assembly 10 includes afirst circuit subassembly 12 and asecond circuit subassembly 14. Thefirst circuit subassembly 12 includes a firstceramic substrate 16 having a circuit portion, or circuit layers, 18 fabricated on a first side thereof. Metallization layer(s) 30 are also fabricated on a second side of theceramic substrate 16. It should be understood that the precise form or pattern of the metallization layer(s) 30 (as well aslayers 32 and 40) will vary depending on the configuration of the ultimate structure. For example, it may be a single continuous layer, multiple layers, a discontinuous layer or separate portions of material applied in the same plane, as shown inFIG. 1 . - The
second circuit subassembly 14 includes aceramic substrate 20 having a circuit portion, or circuit layers, 22 fabricated thereon. Thecircuit portion 22 is disposed on a first side of theceramic substrate 20.Metallization layers 32 are fabricated on a second side of the substrate, as shown. - Metallization layer(s) 40 are disposed in a place between the
layers second subassembly 14. However, it could be fabricated in other manners. - It is to be appreciated that a
gap 50 exists between the first circuit subassembly 12 and the second circuit subassembly 14. This gap may be of any dimension, and may well not even be pertinent to operation of the circuit assembly. Therefore, thegap 50 could be minimized to a negligible dimension, depending on the thickness of themetal layers - It should also be noted that the structure, or assembly, 10 that is shown in
FIG. 1 , is merely representative of a variety of structures that could be fabricated. The structure shown is relatively simply in character to illustrate the aspects of the present invention and should not be considered to be limiting in nature. It should be noted, for example, that the present invention is particularly useful to form astep 60 as representatively shown inFIG. 1 . However, more complex structures of this nature could be similarly fabricated using the present invention. For example, wells, cavities, channels or multi-layer steps may be fabricated using the present invention. - The
ceramic substrate 16 andceramic substrate 20 are preferably fabricated of 96% alumina, but could be fabricated of any suitable ceramic material. The circuit portions, or circuit layers, 18 and 22 can be fabricated on the appropriate sides of the substrates using a variety of methods. Preferably, the circuit layers 18 and 22 are fabricated using a print, dry, and fire (PDF) process. The printing portion of that process is preferably a screen printing process that can be accomplished in a number of manners that are accepted in the field. The drying process would include drying the material for a sufficient amount of time to prepare it for firing. Of course, firing the material should be accomplished over time intervals and in temperature ranges that are appropriate for the materials used in fabricating the circuit portions. Of course, any suitable material may be used for formation of the circuit portions. - The metallization layers 30, 32 and 40 are preferably fabricated of a platinum (Pt) and silver (Ag) alloy. It should be appreciated, however, that any suitable thick film cermet (ceramic-based metal material) conductor with a firing range of 500° C. to 950° C. may be used. There are a variety of industry standard conductor alloys that fall within this category of thick film metallization materials or conductors. For example, silver or gold could alternatively be used as the metallization layer. It should be appreciated, however, that for a particular structure being fabricated, it is preferred that all
metal layers - The process for fabricating the
assembly 10 ofFIG. 1 can be accomplished by laminating, or joining, the two thickfilm circuit subassemblies - Referring now to
FIG. 2 , a method for fabricating thefirst circuit subassembly 12 is shown. InFIG. 2 (a), the process begins by obtaining aceramic substrate 16. As noted above, the ceramic substrate is preferably fabricated of 96% alumina. As shown inFIG. 2 (b), circuit layers 18 are then fabricated on a first side ofceramic substrate 16 by any appropriate processes. Preferably, a print, dry and fire (PDF) process is used to do so. The materials selected may vary but such materials should be of a nature to withstand the processes contemplated by the implementation of the present invention. It should also be understood that thecircuit portion 18 may take a variety of forms and/or patterns. Last, the metallization layer(s) 30 are fabricated on a second side of thesubstrate 16 by printing the metallization layer and allowing it to dry. The metallization layers are preferably printed by a suitable screen printing process. The drying period may vary from case to case. Notably, the metallization layers are not fired at this point. - Referring now to
FIG. 3 , a method for fabricating thesecond circuit subassembly 14 is illustrated. As shown, inFIG. 3 (a), aceramic substrate 20 is first obtained. As noted above, the ceramic substrate is preferably fabricated of 96% alumina.FIG. 3 (b) illustrates that a circuit portion, or circuit layers, 22 is appropriately fabricated on a first side of thesubstrate 20. As withcircuit layers 18, the circuit layers 22 are fabricated using any known process; however, it is preferred that a circuit is fabricated using a print, dry and fire (PDF) process. The materials selected may vary but such materials should be of a nature to withstand the processes contemplated by the implementation of the present invention. It should also be understood that thecircuit portion 22 may take a variety of forms and/or patterns. Last, as illustrated inFIG. 3 (c), metallization layer(s) 32 are fabricated on the other side of thesubstrate 20. As indicated above, the metallization material may be any of a number of compositions; however, it should be the same aslayer 30. The layer(s) 32 are printed and permitted to dry. The metallization layers are preferably printed by a suitable screen printing process. The drying period may vary from case to case. Notably, the metallization layers are not fired at this point. - With reference to
FIG. 4 (a)-(c), thefirst circuit subassembly 12 and thesecond circuit subassembly 14 are then laminated, or joined together. More particularly, with reference toFIG. 4 (a), ametallization layer 40 is printed on themetallization layer 32 of thecircuit subassembly 14. Of course, themetallization layer 40 should be fabricated of the same material aslayers FIG. 4 (b), thefirst circuit subassembly 12 is aligned, or fixtured, with thesecond circuit subassembly 14. In doing so, the metallization layer(s) 30 are aligned with the metallization layers 40, as shown. Any suitable alignment technique may be used to accomplish this objective. It should also be understood that the metallization layers 40 are not dried at this point in the process. - Referring now to
FIG. 4 (c), thefirst circuit subassembly 12 and thesecond circuit subassembly 14 are laminated, or joined together, based on the alignment ofFIG. 4 (b). The structure, particularly the metallization layers 40, is then permitted to dry and then fired, or co-fired, to obtain thefinal assembly 10. Any appropriate drying and co-firing process may be implemented so that the metallization layers 30, 32 and 40 form a sufficient bond for the resultant assembly. Note that theassembly 10 includes thestep 60, as noted above. - As noted above, the drying and firing processes may vary from application to application. The precise time intervals and/or temperature ranges depend on the structures being formed and the materials. For example, when drying, a sufficient drying period may depend on the amount of ventilation that can occur so that the vehicle (or liquid) for the paste (or printed material) sufficiently evacuates. Preferably, the drying process is facilitated by providing vent holes in the ceramic structure. For firing, an 850° C. profile is preferably used; however, it should be understood that the firing of the structures is dependant on the material used.
- It should also be understood that the process for fabricating a completed thick film ceramic assembly used as a circuit is illustrated. It should be appreciated the invention is not so limited, however. For example, the processes for fabricating the circuit layers 18 and 22 are not necessary as described for implementation of the present invention. Structures other than circuit layers may be suitably formed on the ceramic substrate. Alternatively, there may be applications where the ceramic substrates are first bonded using the present invention. Subsequent processes may then be used to form circuit portions or other structures on appropriate sides of the substrates. Moreover, applications using the present invention may not necessitate the formation of any additional circuit portions or other structures.
- The above description merely provides a disclosure of particular embodiments of the invention and is not intended for the purposes of limiting the same thereto. As such, the invention is not limited to only the above-described embodiments. Rather, it is recognized that one skilled in the art could conceive alternative embodiments that fall within the scope of the invention.
Claims (32)
1. (canceled)
2. (canceled)
3. (canceled)
4. (canceled)
5. (canceled)
6. (canceled)
7. (canceled)
8. (canceled)
9. (canceled)
10. (canceled)
11. (canceled)
12. (canceled)
13. (canceled)
14. (canceled)
15. (canceled)
16. (canceled)
17. (canceled)
18. (canceled)
19. (canceled)
20. (canceled)
21. (canceled)
22. (canceled)
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.
Priority Applications (1)
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US11/709,331 US20070237480A1 (en) | 2003-06-16 | 2007-02-21 | Method for fabricating thick film alumina structures used in high frequency, low loss applications and a structure resulting therefrom |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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US10/462,447 US7257281B2 (en) | 2003-06-16 | 2003-06-16 | Method for fabricating thick film alumina structures used in high frequency, low loss applications and a structure resulting therefrom |
US11/709,331 US20070237480A1 (en) | 2003-06-16 | 2007-02-21 | Method for fabricating thick film alumina structures used in high frequency, low loss applications and a structure resulting therefrom |
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US10/462,447 Division US7257281B2 (en) | 2003-06-16 | 2003-06-16 | Method for fabricating thick film alumina structures used in high frequency, low loss applications and a structure resulting therefrom |
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US10/462,447 Expired - Fee Related US7257281B2 (en) | 2003-06-16 | 2003-06-16 | Method for fabricating thick film alumina structures used in high frequency, low loss applications and a structure resulting therefrom |
US11/709,331 Abandoned US20070237480A1 (en) | 2003-06-16 | 2007-02-21 | Method for fabricating thick film alumina structures used in high frequency, low loss applications and a structure resulting therefrom |
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US7214881B2 (en) * | 2004-04-01 | 2007-05-08 | Delphi Technologies, Inc. | High temperature electrical connection |
US7414316B2 (en) * | 2006-03-01 | 2008-08-19 | Freescale Semiconductor, Inc. | Methods and apparatus for thermal isolation in vertically-integrated semiconductor devices |
US8347613B2 (en) * | 2009-09-29 | 2013-01-08 | Ford Global Technologies, Llc | Controlling operation of exhaust of an engine including a particulate filter |
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US7257281B2 (en) | 2007-08-14 |
US20040251230A1 (en) | 2004-12-16 |
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