6,063,442
`[11] Patent Number:
`[19]
`United States Patent
`
`Cohen et al.
`[45] Date of Patent:
`May 16, 2000
`
`US006063442A
`
`[54] BONDING OF POROUS MATERIALS TO
`OTHER MATERIALS UTILIZING
`CHEMICAL VAPOR DEPOSITION
`
`[75]
`
`Inventors: Robert C. Cohen, Rockaway
`Township, N.J.; Joseph R. Vargas,
`Garnerville, NY.
`
`[73] Assignee:
`
`Implex Corporation, Allendale, N].
`
`[21] Appl. No.: 09/179,119
`.
`OCt- 26, 1998
`Flledi
`[22]
`Int. Cl.7 ..................................................... C23C 16/08
`[51]
`[52] US. Cl.
`.......................... 427/250; 427/226; 427/253
`[58] Field of Search .................................. 427/224, 2.26,
`427/248.1 250 252 253
`’
`’
`’
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`5,282,861
`
`2/1994 Kaplan ...................................... 623/16
`
`Primary Examiner—Timothy Meeks
`Attorney, Agent, or Firm—Arthur L. Plevy; Buchanan
`Ingersoll PC
`
`[57]
`
`ABSTRACT
`
`A process for bonding a porous material having an opened
`porous cellular structure to a substrate material, the process
`including the steps of: conditioning the substrate With tan-
`talum in a reactor at 925° C. having a tantalum source pot
`at 550° C; affixmg th‘? Porous material to the conditioned
`subStrate to form in affixed comPOSitC 5““:er by Clamping
`the porous material to the conditioned substrate; and, sub-
`jecting the composite structure to a chemical vapor deposi-
`tion process (CVD) Which uses tantalum as a source material
`for a time sufficient to CVD bond the porous material to the
`conditioned substrate material.
`
`2,130,879
`
`9/1938 Dobke .................................. 228/124.6
`
`11 Claims, 2 Drawing Sheets
`
`Orthopedic Implant Material:
`ie: 1‘16—4 and CoCrMo
`
`20
`
`Machine Desired insert Geometry
`from RVC, Near Net Shape or Bulk Hedrocel Material.
`
`22
`CVD Final Densification of Hedrocel Insert
`
`
`
`Ta Condition Implant Material
`Temperature Settings: Reactor 925°C. Ta Source Pot 550°C,
`Temperature Settings: Reactor 900°C, Ta Source Pot 550°C
`
`
`
`
`Gas Settings: 1000ccm Ar. 500ccm C12 and 1000ccm H2
`Gas Settings: 1000ccm Ar, 900ccm 012 and 1800ccm H2
`
`23
`
`21
`
`24
`
`25
`
`
`Assemble Implant Component for CVD Bonding
`
`
`Hx Hedrocel Insert to Conditioned implant Material. Use clamping devices, Glue, Ta Paste, TI Paste. Tack
`
`Weld or the best combination there of depending on the final
`implant use or application.
`Note: Pastes and/or glues must be cure and dried completely before next step.
`
`
`
`C'D Bonding Cycle
`
`Load assembled components into the clear quartz reactor, cover and pull vacuum to below 1.0 Torr, perform
`
`leak test to meet <1.0 Torr in 10 minutes leak—up, and Run
`
`Temperature Settings: Reactor 975°C, Ta Source Pot 550°C,
`Gas Settings: 1000ccm Ar. 900ccm C12, 1800ccm H2 and 25ccm MGA
`Time at Temp. Cycle: 1000 minutes or time to meet requirements.
`
`Control atomos-here Cool
`to room tem-erature and unload.
`
`
`
`
`
`
`
`
`
`
`
`
`
`26
`
`
`
`Post CVD Bonding Processes (optional)
`
`
`Depending on the Materials used and the requirements there of machining may
`
`
`to damage the Hedrocel and/or the
`be required.
`In this case some care not
`implant device in general must be used. Controlled atmosphere heat
`treating
`
`
`may also be required for some materials and applications.
`
`Page 1 of 6
`
`ZIMMER EXHIBIT 1021
`
`ZIMMER EXHIBIT 1021
`
`Page 1 of 6
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`

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`Page 2 of 6
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`

`

`US. Patent
`
`May 16, 2000
`
`6,063,442
`
`
`
`Page 3 of 6
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`Page 3 of 6
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`

`

`6,063,442
`
`1
`BONDING OF POROUS MATERIALS TO
`OTHER MATERIALS UTILIZING
`CHEMICAL VAPOR DEPOSITION
`
`This invention relates to the high temperature bonding of
`porous materials to other materials utilizing a chemical
`vapor deposition (CVD) process to produce continuous
`layers of a desired material, generally metallic, deposited at
`the porous material and the host material interface.
`BACKGROUND OF THE INVENTION
`
`While the invention is not particularly limited to medical
`devices,
`it
`is indicated at
`the onset
`that a wide use of
`open-cell tantalum structures have been employed for bone
`implants and cells as well as tissue receptors. The use of
`materials such as sold under the trademark HEDROCEL by
`Implex Corporation, the assignee herein, utilizes a metallic
`porous cellular structure which is a biomaterial containing
`tantalum. Such structures are extremely useful and for
`example, are described in detail in US. Pat. No. 5,282,861
`issued on Feb. 1, 1994, and entitled “OPEN CELL TAN-
`TALUM STRUCTURES FOR CANCELLOUS BONE
`IMPLANTS AND CELL AND TISSUE RECEPTORS” to
`
`Richard B. Kaplan and assigned to Ultramet of Pomona,
`Calif.
`
`In that patent there is described the need for a cancellous
`bone substitute and/or cell and tissue receptive material. The
`“Background of the Invention” of the ”861 patent gives
`detail on the prior art as well as various structures that are
`employed. In the patent there is described a reticulated open
`cell carbon foam which is infiltrated with tantalum by the
`chemical vapor deposition (CVD) process.
`It is noted that niobium which has similar chemical and
`
`mechanical properties to tantalum may also be used as well
`as appropriate alloys of tantalum and niobium. A carbon
`foam is infiltrated by chemical vapor deposition (CVD). The
`resulted lightweight strong porous structure basically
`resembles the microstructure of bone and acts as a matrix for
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`the incorporation of bone or for the reception of cells and
`tissues. The pores of this particular material are connected to
`one another to form continuous uniform channels of no dead
`
`40
`
`ends. This network of interconnected pores provides optimal
`permeability in a high surface area to encourage cell and
`tissue ingrowth. It is desirable to utilize a material such as
`that and bond that material to another metallic layer or to
`another substrate.
`
`SUMMARY OF THE INVENTION
`
`This invention involves the use of CVD processes which
`are generally used for thick or thin film applications not
`involving with bonding of different components together.
`More specifically, this invention is related to the novel use
`of continuous CVD layers to bond porous materials as
`described above, for example, to metal, ceramic, vitreous
`carbon or pyrolitic carbon substrates or devices made of
`these substrate materials. The invention to be described is
`
`concerned with the deposition of plated layers that are
`formed utilizing a CVD process. The unique characteristic
`of CVD layers is that the chemical elements composing the
`layer can be deposited at the porous material bonding site to
`form a tough encapsulating layer that bridges or fills the gaps
`between the material surfaces to be bonded. This makes for
`
`a very useful composite material for many medical and other
`applications.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a general flowchart for the CVD bonding process
`according to this invention.
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`FIG. 2 is a schematic diagram of a composite material
`fabricated according to this invention.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`Before proceeding with a description of the preferred
`embodiment of the invention,
`it
`is understood that
`the
`invention involves but does not restrict the use of CVD
`
`processes with thin or thick film applications, which do not
`involve bonding of different components. Specifically as
`indicated above, this invention is related to the novel use of
`continuous CVD layers to bond different components, one
`being a porous material and the other a metal, ceramic,
`vitreous carbon and/or pyrolitic carbon substrate or device
`made of these materials. The host substrate material for the
`
`porous material may be quite different, similar and/or the
`same in nature as the porous material. The CVD layer can be
`of a single metallic element such as tantalum but the present
`techniques are not limited to a specific element and/or alloys
`of different metallic compositions. Depending on the
`application, different CVD layer compositions may be desir-
`able. This invention, as will be described, can be employed
`with all materials that can be deposited using CVD pro-
`cesses with the intent that the deposited layer be involved
`with the bonding of the selected porous material to another
`host substrate material. Thus the intent of the invention is to
`
`bond by CVD bonding a porous material to a substrate layer
`to form a composite material useful in medical and other
`applications.
`As indicated above, HEDROCEL is sold by the Implex
`Corporation and essentially is a metallic porous cellular
`structure containing tantalum. HEDROCEL has been CVD
`bonded to Ti 6-4 (Titanium 6-4) using tantalum (as the
`source material to form the continuous CVD layers).
`While the invention is not limited to metal components, it
`has a particular applicability to the above-described struc-
`ture. As will be explained, metallographic evaluation of the
`tantalum layer deposited indicated that the porous material
`surfaces that were reasonably close to the Ti 6-4 substrate
`surface were bridged and bonded. It has been noticed that
`there can be a significant amount of inter-diffusion between
`metallic materials in both substrates and the deposited layer.
`The HEDROCEL cellular structure biomaterial was also
`
`bonded to CoCrMo, pyrolitic carbon and aluminum oxide
`substrate materials (A1203).
`In the case of ceramic and pyrolitic carbon, the bonding
`was due to the tantalum primarily due to encapsulating the
`substrate materials while the tantalum layer chemically
`interacts with the HEDROCEL. As would be expected,
`significant
`interdifusion of the tantalum layer and the
`ceramic or the pyrolitic carbon at the CVD bonding tem-
`peratures used was not noticed. The desired end product and
`application governs the selection of the CVD process param-
`eters and materials used.
`
`This invention applies equally to layers formed by pure
`gaseous CVD processes, where the source material(s) do not
`come in physical contact with the components to be bonded.
`For example, pure chlorine gas can be used to react with a
`particular source material such as tantalum, at a set tem-
`perature between 490° C. and 650° C. Halide gases are
`formed which transport the desired elements to the surfaces
`to be bonded. This is done under vacuum or with a positive
`flow of inert carrier gas. When bonding HEDROCEL tan-
`talum cellular porous material to Ti 6-4 solid material, the
`halide gas such as tantalum penta-chloride (TaCls), three-
`dimensionally infiltrates through the porous material to the
`
`Page 4 of 6
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`Page 4 of 6
`
`

`

`3
`
`4
`
`6,063,442
`
`substrate bonding surface. Hydrogen gas (H2) is introduced
`and is transported along with the halide gas to the bonding
`surfaces. At the desired bonding sites, the temperature is
`appropriately controlled to reverse the above-mentioned
`reaction to form HCL gas and releasing the source material
`to form the bond layer on all exposed surfaces. For tantalum,
`the desired deposition temperature is between 890° C. and
`1100° C.
`It should be understood that this invention CVD is not
`
`limited to pure gaseous CVD. CVD is used here to describe
`diffusion coating processes,
`includes all out of contact
`process. Contact processes such as pack and slurry diffusion
`processes, alloy powder slurries brushed or sprayed as well
`as slurry electrophoresis processes can be used to deposit the
`layer before component assembly. Layers are included
`where the chemical deposition process is carried out to
`create a bond at the interface of a porous material to another
`material. Apowder mixture, (pack or slurry), in contact with
`or near the part or substrate to be bonded, contains the
`element or elements to be deposited (source material), a
`halide salt (activator), and an inert diluent (filler). When the
`mixture is heated the activator reacts to produce an atmo-
`sphere enriched with the source element halides such as
`tantalum chloride which diffuse in the pack and transfer to
`the bonding sites where the CVD layer is formed.
`While the present invention is not restricted to the bond-
`ing of any particular materials,
`it employs a process in
`conjunction with the bond layer formed and described
`herein. The bonding method is applicable to a wide variety
`of metals, alloys, ceramics, graphites, high temperature
`glasses, pyrolitic carbon and vitreous carbon material com-
`binations. According to the present invention, any of the
`CVD processes can be used. The deposited continuous layer
`must be of sufficient thickness and toughness to bridge the
`gap between the materials to be bonded. The CVD tech-
`niques used to demonstrate explain the process to represent
`any and all CVD techniques that can be conventionally
`employed.
`Referring to FIG. 1, there is shown a general flowchart for
`the. CVD bonding process. Essentially, each of the rectan-
`gular modules is designated by a reference numeral
`to
`describe the particular process step.
`It
`is of course
`understood, as indicated above, that other CVD techniques
`can be employed.
`At the left side, module 20 represents the orthopaedic
`implant material, which as indicated above,
`is Ti 6-4 or
`CoCrMo or a combination of both. At the right, the machine
`desired insert geometry is specified which insert is fabri-
`cated from a porous material such as RVC or the HEDRO-
`CEL material. A type of HEDROCEL porous material is
`more particularly described in US. Pat. No. 5,282,861,
`which shows an open-cell tantalum structure. Other open-
`cell or porous materials can be utilized in place of the
`material described in module 21.
`
`(Ti 6-4,
`the orthopaedic implant material
`As seen,
`CoCrMo) is then conditioned as shown in module 22. In this
`particular process, it is conditioned for a tantalum condition
`implant. Note that in some cases the tantalum layer(s) will
`be only be applied to specific areas on the component or will
`be removed from certain areas during subsequent process
`steps as per the design requirements. Temperature settings
`are specified, for example the reactor is set at 925° C.,
`tantalum source material is set at 550° C.,
`the gas flow
`settings are 1000 ccm of Argon (Ar), 500 ccm of Chlorine
`(C12) and 1000 ccm of Hydrogen (H2). As shown in module
`23, the CVD final densification of the HEDROCEL insert, is
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`done by setting the reactor at 90° C. the tantalum source at
`550° C., with gas settings 1000 ccm of Argon, 900 ccm of
`C12 and 1800 ccm of H2. The two treated materials are then
`assembled as an implant component for CVD bonding. For
`example,
`the tantalum condition implant material from
`module 22 is now assembled together with the material from
`module 23. The material as indicated in module 21 can
`
`assume any type of shape such as an implant for a hip stem
`or a knee implant or any type of prosthesis or other shape
`and this implant is now to be bonded to the implant material.
`Module 24 indicates that the assembled implant is then
`combined together for CVD bonding. For example,
`the
`HEDROCEL insert
`is fixed to the conditioned implant
`material using any type of clamping device or bonding
`material such as a glue, tantalum paste, titanium paste, in
`some applications tack welding may be used. Any combi-
`nation of the aforementioned can be incorporated depending
`on the final implant use and design. In other words,
`in
`module 24 the entire component
`is assembled and held
`together by means of a typical bond which is not a perma-
`nent bond. Then the assembled component from module 24
`is subjected to the CVD bonding cycle.
`As shown in module 25 one loads the assembled com-
`
`ponents into a clear quartz reactor for CVD, covers and pulls
`a vacuum to below 1.0 torr. Leak tests are performed to meet
`the vacuum requirements as indicated in module 25. The
`temperature settings are also shown in module 25 where the
`reactor is set at 975° C., the tantalum source is 550° C. and
`gas settings are 1000 ccm Argon, 900 ccm C12, 1800 ccm H2
`and 25 ccm MGA. Time at temperature is 1,000 minutes or
`the time sufficient to perform a CVD bonding of the two
`materials. The atmosphere is normally controlled during the
`bonding layer deposition process and the cooling to room
`temperature and the component is unloaded.
`After the CVD bonding occurs, there can be a post CVD
`bonding process which is indicated in module 26 as optional.
`Depending on the materials used, further requirements or
`machining may be required. In this case some care has to be
`made not to damage the porous metal or the HEDROCEL
`components and/or the implant device in general must be
`used. Controlled atmosphere heat
`treating may also be
`required for some materials and applications.
`As one can see from the general flowchart, it is the main
`objective of the present invention to bond a porous material
`to other materials using a chemical vapor deposition (CVD)
`technique. The unique characteristic of CVD layers is that
`the chemical elements composing the layer can be deposited
`at the porous material bonding site to form a tough encap-
`sulating layer that will bridge or fill the gaps between the
`material surfaces to be bonded.
`
`As indicated, the CVD process is very well known and
`such a typical process is, for example, described in the
`above-noted patent US. Pat. No. 5,282,861. Essentially the
`CVD process utilizes a reaction chamber which can enclose
`a chlorination chamber or other gas chamber and a hotwall
`furnace. Some type of heater, for example a resistance
`heater, surrounds the chambers and an induction heating coil
`can surround the reaction chamber to heat
`the furnace.
`Metals such as tantalum can be located within the chlori-
`
`nation chamber and a substrate would also be positioned
`within the hotwall furnace. Chlorine gas and other gasses as
`indicated above react with the tantalum and the open-cell
`material to CVD bond. As indicated the tantalum chloride
`
`mixes with hydrogen which is also injected into the chamber
`and then passes through an opening in the chamber as an
`opening in a hotwall furnace. The mixture as indicated is
`
`Page 5 of 6
`
`Page 5 of 6
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`

`

`6,063,442
`
`5
`heated to produce reactions so that the gasses assure that
`there is a vapor deposition of materials and a bonding of the
`materials.
`While indicated above the substrate to be used is Ti 6-4
`
`and CoCrMo, other substrates can be employed as well. It is
`also noted that there are many advances being made in the
`CVD fields such as plasma assisted CVD and other tech-
`niques which are being explored and utilized in the semi-
`conductor field. It is anticipated that such techniques may
`also be employed in conjunction with this invention.
`One can employ plasma enhanced chemical vapor depo-
`sition (PECVD). PECVD is a widely accepted technique for
`the deposition of dielectric films such silicon nitride and
`silicon oxide. PECVD has also been employed for the
`deposition of refractory metals and so on.
`It is therefore understood that while the above techniques
`particularly describe a conventional CVD process,
`it
`is
`understood that other processes can be utilized to bond
`porous materials to other materials using the vapor deposi-
`tion technique.
`Referring to FIG. 2, there is shown a composite material
`provided by this invention. Essentially, reference numeral 30
`depicts a porous material which as indicated previously it is
`preferably a tantalum open-cell structure which could be
`formed by chemical vapor deposition by use of a reticulated
`carbon foam substrate. While tantalum is described, it is of
`course understood that other materials can be utilized as
`well.
`
`As seen from FIG. 2, the material while being porous can
`be shaped into many configurations simple or complex. This
`can be done by shaping the raw carbon substrate prior to
`metal infiltration or it can be done by typical machining
`techniques. For purposes of illustration, the porous material
`is also referred to by the trademark HEDROCEL and is
`shown by reference numeral 30. The material is bonded to
`a substrate 31 which as indicated above can be many
`materials including Ti 6-4 and CoCrMo and other materials
`as well. It is of course explained and indicated above that
`these materials are many.
`It is the major purpose of the invention to produce a
`composite article as shown in FIG. 2 which uses CVD layers
`to bond porous materials to metal, ceramic, vitreous carbon
`and/or pyrolitic carbon substrates or devices made of such
`materials. It is of course again repeated that the host sub-
`strate material for the porous material may be quite different,
`similar and/or the same in nature as the porous material thus
`substrate 31 can be extremely different or similar to porous
`material 30. It is noted that porous material 30 and substrate
`31 are bonded together using a chemical vapor deposition
`technique.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`6
`It is also noted that both the porous material 30 and the
`substrate material 3 1 can be pre-treated as explained above.
`Hence either material can be further treated with tantalum
`using a CVD process to further coat the material before
`bonding substrate 31 to porous material 30 using a continu-
`ous CVD process.
`What is claimed:
`1. A process for bonding a porous material having an
`opened porous cellular structure to a substrate material, said
`process comprising the steps of:
`conditioning said substrate with tantalum in a reactor at
`925° C. having a tantalum source pot at 550° C.;
`affixing said porous material to said conditioned substrate
`to form an affixed composite structure by clamping said
`porous material to said conditioned substrate; and,
`subjecting said composite structure to a chemical vapor
`deposition process (CVD) which uses tantalum as a
`source material for a time sufficient to CVD bond said
`porous material to said conditioned substrate material.
`2. The process according to claim 1 wherein said porous
`material
`is a metallic porous cellular structure material
`containing tantalum.
`3. The process according to claim 1 wherein said substrate
`is titanium.
`4. The process according to claim 1 wherein said substrate
`is CoCrMo.
`
`5. The process according to claim 1 wherein said reactor
`uses argon, chlorine and hydrogen gases during said condi-
`tioning.
`6. The process according to claim 1, further comprising
`the step of CVD densifying said porous material prior to
`CVD bonding it to said substrate.
`7. The process according to claim 6 wherein said step of
`CVD densification includes placing said porous material in
`a reactor housing a tantalum source and using argon, chlo-
`rine and hydrogen gases.
`8. The process according to claim 7 wherein the tempera-
`ture of said reactor is 900° C.
`9. The process according to claim 8 wherein gas settings
`of said reactor are 1000 ccm Ar, 900 ccm C12 and 1800 ccm
`H2.
`10. The process according to claim 1 wherein said chemi-
`cal vapor deposition for bonding includes;
`placing said composite structure in a reactor having a
`tantalum source pot and using argon, chlorine and
`hydrogen gases for a time sufficient to bond said porous
`material to said conditioned substrate material.
`
`11. The process according to claim 10 wherein said
`reactor is a quartz reactor at a temperature of about 925° C.
`with said source pot at about 550° C.
`*
`*
`*
`*
`*
`
`Page 6 of 6
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`Page 6 of 6
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`