U.S. patent application number 09/815912 was filed with the patent office on 2001-08-02 for vapor deposition coated intracorporeal device.
This patent application is currently assigned to Advanced Cardiovascular Systems, Inc.. Invention is credited to Howland, Johathan M..
Application Number | 20010011158 09/815912 |
Document ID | / |
Family ID | 22835593 |
Filed Date | 2001-08-02 |
United States Patent
Application |
20010011158 |
Kind Code |
A1 |
Howland, Johathan M. |
August 2, 2001 |
Vapor deposition coated intracorporeal device
Abstract
A method of joining two members of a medical device wherein at
least one of the members has a thin layer of joinable material
deposited on the surface thereof by vapor deposition, preferably,
physical vapor deposition. A guidewire for advancement of
intraluminal medical devices may be manufactured by depositing a
thin layer of joinable material on the surface of a component which
is made from a reactive alloy with a tenacious oxide layer. The
thin layer of joinable material facilitates joining difficult to
bond materials with other components of the guidewire. Physical
vapor deposition may also be used to treat components of medical
devices, such as distal guidewire segments, in order to alter their
mechanical properties. Specifically, a pseudoelastic alloy segment
may be made shapeable by vapor deposition of a non-pseudoelastic
metal thereon.
Inventors: |
Howland, Johathan M.;
(Temecula, CA) |
Correspondence
Address: |
Edward J. Lynch
Heller Ehrman White & McAuliffe LLP
275 Middlefield Road
Menlo Park
CA
94025-3506
US
|
Assignee: |
Advanced Cardiovascular Systems,
Inc.
|
Family ID: |
22835593 |
Appl. No.: |
09/815912 |
Filed: |
March 23, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09815912 |
Mar 23, 2001 |
|
|
|
09223224 |
Dec 30, 1998 |
|
|
|
6234981 |
|
|
|
|
Current U.S.
Class: |
600/585 |
Current CPC
Class: |
A61M 25/09 20130101;
A61M 2025/09175 20130101 |
Class at
Publication: |
600/585 |
International
Class: |
A61B 005/00 |
Claims
What is claimed is:
1. A method for joining a first member of a medical device to a
second member of the medical device comprising: a) depositing a
thin layer of joinable material on at least a portion of the first
member by vapor deposition; b) positioning the thin layer of
joinable material on the first member in proximity to a joinable
portion of the second member; c) applying a joining agent to the
thin layer of joinable material on the first member and the
joinable portion of the second member.
2. The method of claim 1 wherein the first member is comprised of a
reactive metal having a tenacious oxide.
3. The method of claim 2 wherein the reactive metal is comprised of
a titanium containing alloy.
4. The method of claim 3 wherein the titanium containing alloy is
comprised of NiTi.
5. The method of claim 2 further comprising substantially removing
the tenacious oxide prior to depositing the thin layer of joinable
material.
6. The method of claim 5 wherein the metal substance is solder.
7. The method of claim 1 wherein the joining agent is comprised of
a polymer material.
8. The method of claim 7 wherein the polymer material is comprised
of a thermosetting epoxy.
9. The method of claim 7 wherein the polymer is a cyanoacrylate
adhesive.
10. The method of claim 1 wherein the thin layer of joinable
material is a metal.
11. The method of claim 1 wherein the thin layer of joinable
material is stainless steel.
12. The method of claim 11 wherein the second member is comprised
of stainless steel.
13. A medical device comprising: a) a first member; b) a second
member; c) a thin layer of joinable material on at least one of the
members; and c) a joining material disposed upon the thin layer of
joinable material joining the first member and the second
member.
14. The medical device of claim 13 wherein the first member is made
of the same metal as the second member.
15. The medical device of claim 13, wherein the first member is a
different metal than the second member.
16. The medical device of claim 13, wherein the first member is a
different metal from the second member that will not facilitate a
strong solder joint together to the metal forming the second
member.
17. The medical device of claim 13, wherein the thin layer of
joinable material is a metal.
18. The medical device of claim 13, wherein the thin layer of
joinable material is a non-metal.
19. The medical device of claim 13, wherein the thin layer of
joinable material is up to about 2 microns in thickness.
20. The medical device of claim 13, wherein the thin layer of
joinable material is between about 1 and 2 microns thick.
21. A method of making a guidewire for intraluminal advancement of
a medical device comprising: a) vapor depositing a thin layer of
joinable material on at least a proximal end of a distal section of
an elongate core; b) securing a distal end of a proximal section of
an elongate core to the proximal end of the distal section of the
elongate core; and c) securing a flexible body member about at
least a portion of the distal section of the elongate core.
22. The method of claim 21 wherein the distal section of the
elongate core comprises a titanium containing alloy.
23. The method of claim 22 wherein a) includes depositing a thin
layer of joinable material on at least a distal end and proximal
end of the distal section of the elongate core.
24. The method of claim 23 wherein the distal end of the proximal
section of the elongate core is secured to the proximal end of the
distal section of the elongate core by soldering and the flexible
body member is secured to the distal end of the distal section of
the elongate core by soldering.
25. The method of claim 24 further comprising providing a sleeve
that is positioned over at least a portion of the distal end of the
proximal section of the elongate core and the proximal end of the
distal section of the elongate core and soldered thereto.
26. The method of claim 22 wherein the distal section further
comprises a small diameter distal segment formed into a shapeable
member by vapor deposition of a sufficient layer of a
non-pseudoelastic metal thereon.
27. A guidewire for intraluminal advancement of a medical device
within a patient, comprising: a) a proximal section of an elongate
core with a proximal end and a distal end; b) a distal section of
the elongate core with a proximal end and a distal end and a thin
layer of joinable material on at least a portion of the distal
section with the distal end of the proximal section secured to the
proximal end of the distal section by a joining agent; and c) a
flexible body having a proximal end and a distal end disposed about
and secured to at least a portion of the distal section with a
joining agent.
28. The guidewire of claim 27, further comprising a distal segment
at the distal end of the distal section of the elongate core.
29. The guidewire of claim 28 wherein the distal section is
comprised of a pseudoelastic alloy and the distal segment of the
distal section has a sufficient layer of non-pseudoelastic metal on
it to make it shapeable.
30. The guidewire of claim 27, wherein the distal section has at
least one tapered section.
31. The guidewire of claim 27, wherein a distal segment of the
distal section is flattened.
32. The guidewire of claim 27, wherein the joinable material
deposited is gold.
33. The guidewire of claim 27, wherein the joinable material
deposited is an alloy.
34. The guidewire of claim 33, wherein the alloy is stainless
steel.
35. The guidewire of claim 27, wherein the joinable material
deposited is a polymer.
36. The guidewire of claim 27, wherein the distal section is
completely covered with the deposited joinable material.
37. The guidewire of claim 27, wherein the joinable material is
only deposited on the distal section in areas to which other
members are joined.
38. The guidewire of claim 27, wherein the thickness of the thin
layer is up to 2 microns.
39. The guidewire of claim 27, wherein the thickness of the thin
layer is between 1 and 2 microns.
40. The guidewire of claim 27, wherein the thin coating of joinable
material is sufficient to create a shapeable distal segment of the
distal section.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to joining elongated members such as
elements of guidewires for advancing intraluminal devices within
body lumens. Conventional guidewires for stent delivery catheters,
balloon dilatation catheters, atherectomy catheters and the like
usually comprise an elongated core member with one or more tapered
sections near the distal end thereof and a flexible body such as a
helical coil disposed about the distal portion of the core member.
A shapeable member, which may be the distal extremity of the core
member or a separate shaping ribbon which is secured to the distal
extremity of the core member extends through the flexible body and
is secured to a rounded plug at the distal end of the flexible
body. Torquing means are provided on the proximal end of the core
member to rotate, and thereby steer, the guidewire while it is
being advanced through a patient's vascular system. In some cases,
the physician will bend the distal end of the core member to
facilitate advancement of, the guidewire through the turns of the
patient's body lumen, necessitating the shapeable member.
[0002] In a typical coronary procedure, a guiding catheter having a
preformed distal tip is percutaneously introduced into a patient's
peripheral artery, e.g. femoral or brachial artery, by means of a
conventional Seldinger technique and advanced therein until the
distal tip of the guiding catheter is seated in the ostium of a
desired coronary artery. A guidewire is positioned within an inner
lumen of a dilatation catheter and then both are advanced through
the guiding catheter to the distal end thereof. The guidewire is
first advanced out of the distal end of the guiding catheter into
the patient's coronary vasculature until the distal end of the
guidewire crosses a lesion to be dilated. A desired diagnostic or
therapeutic system can then be advanced over the guidewire to
perform a procedure at the site of the lesion. Typical procedures
include balloon angioplasty and intracoronary stent delivery.
[0003] A major requirement for guidewires is that they have
sufficient column strength to be pushed through a patient's
vascular system or other body lumen without kinking. However, the
distal portion must also be flexible enough to avoid damaging the
blood vessel or other body lumen through which they are advanced.
Efforts have been made to improve both the strength and flexibility
of guidewires to make them more suitable for their intended uses,
but these two properties are for the most part diametrically
opposed to one another in that an increase in one usually involves
a decrease in the other.
[0004] Further details of guidewires, and devices associated
therewith for various interventional procedures can be found in
U.S. Pat. No. 4,748,986 (Morrison et al.); U.S. Pat. No. 4,538,622
(Samson et al.): U.S. Pat. No. 5,135,503 (Abrams); U.S. Pat. No.
5,341,818 (Abrams et al.); U.S. Pat. No. 5,636,641 (Fariabi); and
U.S. Pat. No. 5,345,945 (Hodgson, et al.) which are hereby
incorporated herein in their entirety by reference thereto.
[0005] One approach to achieving both flexibility and column
strength in a guidewire is to use a pseudoelastic alloy for a core
member, such as NiTi. When stress is applied to a core member
exhibiting pseudoelastic characteristics at a temperature at or
above which the transformation of martensite phase to the austenite
phase is complete, the core member deforms elastically until it
reaches a particular stress level where the alloy then undergoes a
stress-induced phase transformation from the austenite phase to the
martensite phase. As the phase transformation proceeds, the alloy
undergoes significant increases in strain but with little or no
corresponding increases in stress. The strain increases while the
stress remains essentially constant until the transformation of the
austenite phase to the martensite phase is complete. Thereafter,
further increase in stress is necessary to cause further
deformation.
[0006] If the load on the pseudoelastic alloy is removed before any
permanent deformation has occurred, the martensitic core metal will
elastically recover and transform back to the austenite phase. The
reduction in stress first causes a decrease in strain. As stress
reduction reaches the level at which the martensite phase
transforms back into the austenite phase, the stress level in the
specimen will remain essentially constant (but substantially less
than the constant stress level at which the austenite transforms to
the martensite) until the transformation back to the austenite
phase is complete, i.e. there is significant recovery in strain
with only negligible corresponding stress reduction. After the
transformation back to austenite is complete, further stress
reduction results in elastic strain reduction.
[0007] This ability to incur significant strain at relatively
constant stress upon the application of a load and to recover from
the deformation upon the removal of the load is commonly referred
to as pseudoelasticity. These properties to a large degree allow a
guidewire core of a pseudoelastic material to have both flexibility
and strength. However, many pseudoelastic alloys, particularly
titanium containing alloys, are difficult to join or secure to
other components, primarily because a tenacious oxide layer that
develops on the surface of such alloys. Prior methods for attaching
subassemblies to psuedoelastic or superelastic components included
molten or fusion salt etching and then pre-tinning with gold or
similar materials to facilitate forming a strong bond, as seen in
U.S. Pat. No. 5,695,111 to Nanis, et al. which is hereby
incorporated in its entirety. In addition, it is often desirable
for a guidewire to have an integral core member of a unitary piece
of metal that extends from a proximal section to the distal tip of
the guidewire. However, it also often desirable for the distal tip
of a guidewire to be shapeable with manual deformation so that a
physician can tailor the shape of the distal tip to the vasculature
that must be traversed. As discussed above, pseudoelastic alloys
can withstand a large amount of stress without incurring plastic
deformation, and are thus difficult to shape when used as core
members in distal guidewire sections.
[0008] What has been needed and heretofore unavailable, however, is
a method for manufacturing a guidewire with a superelastic or
pseudoelastic component which will allow the component to accept a
weld, solder or adhesive joint with ease of manufacture and low
cost. What has also been needed is a distally contiguous distal
segment of a guidewire core made of a pseudoelastic or superelastic
alloy which can be shaped or bent to allow for guiding, without the
need of a separate non-pseudoelastic piece, i.e. a stainless steel
shaping ribbon.
SUMMARY OF THE INVENTION
[0009] The present invention is directed to a method for joining a
first member of a medical device to a second member of a medical
device by depositing a thin layer of joinable material on at least
a portion of the first member by vapor deposition, preferably, by
physical vapor deposition. The thin layer of joinable material can
then be secured by suitable methods to the second member of the
medical device with a joining agent or joining process. The
invention is also directed to a medical device, preferably a
guidewire, that has at least two members or elements joined by
using a thin layer of joinable material deposited by vapor
deposition.
[0010] A guidewire having features of the invention preferably has
at least one elongate core section that is made of a pseudoelastic
alloy that is secured or bonded to other elongate core sections,
flexible body members or the like. Preferably, NiTi alloy is used
for the pseudoelastic alloy material, however, other suitable
pseudoelastic alloys may be used. The joining or securing of
pseudoelastic components, particularly titanium containing alloys,
in a medical device is often complicated by a tenacious oxide layer
that forms on the surface of such a pseudoelastic alloy which does
not readily accept joining agents such as molten material of the
same pseudoelastic alloy during welding, solder or polymer
adhesives such as heat curable epoxies or cyanoacrylates. The
present invention solves this problem by using vapor deposition to
coat the pseudoelastic alloy with a readily joinable material such
as metals like stainless steel, suitable polymers or the like. The
joinable material layer creates a bondable or joinable surface that
can be welded, soldered or bonded. Suitable joinable materials can
include stainless steel, gold, platinum, tantalum or any other
suitable material that lends itself to bonding, welding or
soldering. Suitable joining agents include molten metals of the
same composition as the joinable material, various solders, various
brazes, or polymer adhesives such as heat curable epoxies,
cyanoacrylates and the like.
[0011] One embodiment of the invention is directed to the use of
vapor deposition to apply a thin layer of joinable material to a
tapered distal NiTi core used in guidewires. The layer can be
specifically deposited in areas to which other subassemblies must
be attached using a solder joint or other suitable means. The vapor
deposition of a joinable material allows the subassemblies to
attach to the distal core.
[0012] In another aspect of the invention, vapor deposition is used
to process a distal segment of a pseudoelastic distal section of a
guidewire core member so as to create a distally contiguous
shapeable member. The shapeable member functions similarly to a
separate stainless steel shaping ribbon but is integral to the
distal section so as to minimize any risk of detachment or failure
of a bond therebetween. It has been found that by subjecting the
distal segment of a distal section of an elongate core member made
of pseudoelastic alloy to vapor deposition of stainless steel or
other non-pseudoelastic metals, that the distal segment of
pseudoelastic alloy can be made shapeable with similar mechanical
properties to a stainless steel shaping ribbon. Shapeability of a
superelastic or psuedoelastic distal segment of a guidewire is
achieved by vapor depositing sufficient stainless steel or other
suitable metal or material onto the distal segment so as to
decrease the pseudoelastic characteristics of the distal segment as
a whole.
[0013] These and other advantages of the invention will become more
apparent from the following detailed description of the invention
when taken in conjunction with the accompanying exemplary
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 shows an elevational view in partial section of an
embodiment of a guidewire having features of the invention.
[0015] FIG. 2 shows a transverse cross sectional view of the
guidewire of FIG. 1 taken at 2-2.
[0016] FIG. 3 shows a transverse cross sectional view of the
guidewire of FIG. 1 taken at 3-3.
[0017] FIG. 4 shows an elevational view of an embodiment of a
guidewire having features of the invention.
[0018] FIG. 5 is a schematic view of a device which can be used for
vapor deposition processing with a distal section of a guidewire
core positioned within a vapor deposition chamber.
DETAILED DESCRIPTION
[0019] FIG. 1 shows an elevational view in partial section of a
guidewire 10 having features of the invention. The guidewire 10 has
an elongate core 11 with a proximal section 12 and a distal section
13. The proximal section 12 has a proximal end 14 and a distal end
15. The distal section 13 has a proximal end 16 and a distal end
17. The proximal section 12 is made from a high strength material,
preferably stainless steel, and is preferably round in cross
section. The proximal section 12 is shown as a constant diameter
section but may have one or more tapered segments thereon. The
diameter of the proximal section 12 can be from about 0.010 inches
to about 0.025 inches, but is preferably about 0.012 to about 0.016
inches. The length of the proximal section 12 can be from about 75
to about 300 cm, but is preferably about 125 cm to about 175
cm.
[0020] The distal section 13 has a tapered segment 18. Although the
embodiment shown in FIG. 1 has only one tapered segment 18 on the
distal section, any number of tapered segments can be used as the
performance requirements of the guidewire 10 dictate. The tapered
segment 18 creates a more flexible distal section for improved
trackability. The distal section 13 is made from a pseudoelastic
alloy, such as NiTi, and has a thin layer of joinable material 21
vapor deposited thereon. Preferably, any tenacious oxide layer
disposed on the distal section 13, such as titanium oxide, has been
removed from an outer surface 22 of the distal section prior to the
application of the thin layer of joinable material 21 in at least
those areas of the outer surface on which the joinable material is
disposed. The oxide layer can be removed by chemical or plasma
etching or other suitable means. The entire outer surface 22 of the
distal section may be coated with a thin layer of joinable material
21, or only desired portions thereof. For example, the distal
section can be coated with the thin layer of joinable material 21
only in areas of the outer surface 22 where other components of the
guidewire will be attached. Preferably about 15 to about 20 cm of
the distal end 17 and proximal end 16 of the distal section 13 have
a thin layer of joinable material 21 deposited thereon. The thin
layer of joinable material 21 is preferably applied with a vapor
deposition process which produces a thin layer having a thickness
up to about 20 microns, preferably about 1 to about 5 microns, and
more preferably about 1 to about 3 microns.
[0021] The distal section 13 has a distal segment 23 at the distal
end 17 which is a segment having a small cross section which
provides flexibility and preferably shapeability to the distal end
17. The distal segment 23 is a distally contiguous and integral
portion of the distal section 13 and is made of the same
pseudoelastic alloy as the rest of the distal section. It is
desirable for the distal segment 23 to have shapeable
characteristics by virtue of the deposition of the thin layer of
joinable material 21. The thin layer of joinable material can be
made of metals such as stainless steel, which can have
non-pseudoelastic mechanical properties which give malleable
properties and shapeability to the distal segment. The thickness of
the thin layer of joinable material 21 on the distal segment 23
required to give the distal segment shapeable properties can vary
depending on the material used for the distal section and the
processing undergone by that material. The thickness of the thin
layer of joinable material 21 required for a shapeable distal
segment 23 can also depend on the type of material used for the
thin layer. If stainless steel is used for the thin layer 21 on a
distal segment 23 of NiTi alloy, the thickness of the thin layer
required for a shapeable distal segment is about 1 to about 2
microns, although a thickness greater than 2 microns can give
greater shapeability.
[0022] By way of example, a preferred embodiment of a distal
section 13, having a shapeable distal segment 23 is produced by
starting with a piece of NiTi alloy wire approximately 0.0135
inches in diameter and about 40 to about 45 cm in length. A distal
taper is ground by conventional centerless grinding techniques onto
the distal section 13 to reduce the nominal 0.0135 inch diameter to
a diameter of about 0.0025 to about 0.0035 inches at the distal
segment 23. The distal segment 23 at this stage will have a
substantially constant outer diameter and a length of about 3 to
about 10 mm, preferably about 5 to about 8 mm. The distal section
13 is then chemically etched, preferably in a mixture of nitric
acid and sulfuric acid, to remove the oxide layer on the distal
section. About 16 to about 20 cm of the distal end of the distal
section 13 is then inserted into a suitable PVD chamber and plasma
etched for about 5 minutes in a working gas such as argon. The
temperature within the PVD chamber during the plasma etch is about
200 to about 300 degrees Centigrade. After plasma etching, the
portion of the distal section 13 within the PVD chamber is PVD
coated with a layer of 316 stainless steel to a thickness of about
1 to about 2 micrometers. The PVD coating process normally takes
about 5 to about 10 minutes to complete. The temperature within the
PVD coating chamber during PVD coating of the 316 stainless steel
is about 200 to about 300 degrees Centigrade. After the PVD coating
process is complete, the distal section 13 is removed from the PVD
coating chamber and the distal segment 23 is flattened in a
pneumatic press to a thickness of about 0.0015 to about 0.002
inches. In this flattened state, with a 1 to 2 micrometer thick
layer of stainless steel applied, the distal segment 23 will
exhibit shapeable characteristics.
[0023] The proximal end 16 of the distal section 13 and distal end
15 of the proximal section 12 are joined with a sleeve 24. The
sleeve 24 is disposed over at least a portion of the proximal end
16 of the distal section 13 and the distal end 15 of the proximal
section 12. The sleeve 24 can be attached in a variety of ways, but
is preferably soldered to the distal end 15 of the proximal section
and the thin layer of joinable material 21 disposed on the proximal
end 16 of the distal section at a joining interface 25. The sleeve
24 can be made from a variety of high strength materials, but is
preferably made from a tube of stainless steel. In such an
embodiment, joinable material 21 is also stainless steel.
[0024] A flexible body member 26 is disposed about the distal
section 13. The flexible body 26 has a proximal end 27 and a distal
end 28 and is preferably made of a helical coil of metal. The
flexible body 26 preferably has an outer diameter similar to that
of the proximal section 12 of the elongate core 11. The flexible
body 26 can be from about 1 to about 50 cm in length, preferably
about 5 to about 20 cm in length, and more preferably about 7 to
about 12 cm. The flexible body 26 can be constructed from
radiopaque metals such as gold, platinum, tantalum or the like, but
may also be made from non-radiopaque metals such as stainless
steel. Combinations of radiopaque and non-radiopaque metals can
also be used for the flexible body 26, such as stainless steel with
a gold or platinum outer layer. The material from which the
flexible body 26 is made generally has a transverse diameter of
about 0.001 to about 0.004 inch, preferably about 0.002 to about
0.003 inch (0.05 mm). Multiple turns of the distal portion of
flexible body may be expanded to provide additional flexibility.
The flexible body may 26 have transverse dimensions about the same
as the proximal core section.
[0025] The flexible body 26 may also consist of a polymer or
composite jacket of polyimide, polyethylene, polyurethane, TFE,
PTFE, ePTFE and the like. If a polymer material is used for the
flexible body 26, it may be desirable to use a similar polymer for
the thin layer of joinable material 21 disposed on the distal
section 13.
[0026] The distal end 28 of the flexible body 26 is secured to the
distal end 17 of the distal section 13 of the elongate core 1 1 by
a first solder body 31. The first body of solder 31 may be formed
into a rounded shape to create a non-traumatic configuration for
the distal end 17 of the distal section. The proximal end 27 of the
flexible body 26 is secured to the distal section 13 by a second
solder body 32. The flexible body 26 may be secured to the distal
section 13 along its length in other locations between the distal
end 28 and proximal end 27. The flexible body 26 may also be
constructed of several different lengths of helical coil which may
be made from different or similar materials. For example, the
flexible body 26 may be made from two helical coils, one of which
is radiopaque, the other of which is nonradiopaque.
[0027] The first solder body 31 and second solder body 32 are
disposed between the respective portions of the flexible body 26
and the distal section 13 of the elongate core 11. The solder
bodies are preferably made of a material that adheres readily to
both the material of the flexible body 26 and that of the thin
layer of joinable material 21 disposed on the distal section 13.
Preferably both the flexible body 26 and the thin layer of joinable
material 21 are made of stainless steel.
[0028] FIG. 2 is a transverse cross sectional view of the guidewire
10 of FIG. 1. The second solder body 32 is disposed about and
bonded to the thin layer of joinable material 21. The thin layer of
joinable material 21 is disposed about the distal section 13 of the
elongate core 11.
[0029] FIG. 3 is a transverse cross sectional view of the guidewire
10 of FIG. 1. The flexible body 26 is disposed about the distal
segment 23 of the distal section 13 of the elongate core 11. The
thin joinable layer 21 is disposed about the distal segment 23. The
distal segment 23 has a flattened rectangular cross section, but
may also have a round, elliptical or square cross sectional shape
or any other suitable configuration. A flattened distal segment 23
improves the shapeability of the segment.
[0030] FIG. 4 depicts an alternative embodiment of a guidewire 40
having features of the invention. A distal section 41 of an
elongate core 42 has a tapered segment 43, a distal segment 44 and
a distal end 45. The distal section 41 can be made from materials
similar to those described for the distal section of the guidewire
of FIG. 1, and can be similarly attached to a proximal section. The
distal section 41 is preferably made from NiTi alloy which has been
coated with a thin layer of joinable material 46 on a bonding area
47. In the embodiment shown in FIG. 4, only the portions of the
distal section 41 which are to be bonded to other components, i.e.
the bonding area 47, have been coated with a thin layer of joinable
material 46 such as stainless steel.
[0031] A shaping ribbon 48 having a proximal end 51 and a distal
end 52 is disposed adjacent the distal segment 44. The shaping
ribbon 48 can be made from any suitable high strength material, but
is preferably made from a flattened piece of stainless steel. A
flexible body 53 having a proximal end 54 and a distal end 55 is
disposed about at least a portion of the distal segment 44 and the
shaping ribbon 48. The distal end 55 of the flexible body 53 is
secured to the distal end 52 of the shaping ribbon 48 with a first
body of solder 56. The proximal end 54 of the flexible body 53 is
secured to the proximal end 51 of the shaping ribbon 48 and the
bondable area 47 of the distal section 41 with a second body of
solder 57. The distal end 45 of the distal section 41 is disposed
within the flexible body 53. The flexible body 53 may be
constructed in a manner similar to the flexible body 26 of the
embodiment of FIG. 1.
[0032] FIG. 5 depicts a schematic view of a vapor deposition
apparatus 60. The apparatus 60 has a vacuum chamber 61 disposed
about a vapor deposition device 62. The vapor deposition device 62
preferably has an elongate hollow body 63 with a vapor deposition
chamber 64 and a sputtering device 65 operably attached thereto. A
distal section 70 of a guidewire having features of the invention
is shown with a proximal end 72 and a distal end 73 disposed within
the vapor deposition chamber 64. In this way, the proximal end 72
and distal end 73 of the distal section 70 can be coated with a
thin layer of joinable material without coating an intermediate
portion 74 of the distal section 70.
[0033] The vapor deposition process may be carried out by
evaporative or sputtering techniques. Preferably, the vapor
deposition process is physical vapor deposition utilizing a
sputtering technique. Argon is typically use as a working gas,
which forms a plasma in the vacuum. After cleaning the NiTi of
oxide, the argon plasma acts as an energizing agent to impinge upon
the molecules of the target material. The target material is made
of a joinable material that is to be formed in a thin layer on the
desired segment of the core wire. Once energized by the argon gas
molecules, the energized target material molecules leave the target
substrate and attach to the core material substrate. The energized
target material molecules can be compelled toward the core section
material during the deposition process by applying a voltage
potential between the target material and the core section
substrate to be coated. The vapor deposition process described
above can be carried out with the distal core section held in a
stationary position, however, the process may also be carried out
with a continuous dynamic process wherein a long piece of distal
core section material is continuously drawn through the vapor
deposition chamber with the chamber activated thereby coating or
applying a thin layer of joinable material to the entire length of
the distal section or to multiple distal sections which can be
attached end to end for vapor deposition processing and separated
later.
[0034] The vapor deposition process normally involves inserting a
shaped or tapered NiTi core wire into a vapor deposition vacuum
chamber, in its entirety, or any portion or portions thereof.
Preferably, about 15 to about 20 cm of the distal end and about 15
to about 20 cm of the proximal end of a pseudoelastic distal core
section is disposed within the vapor deposition chamber. The vapor
deposition chamber dimensions can be about 30 inches in length with
an 18 inch diameter, although those skilled in the art will realize
that a wide variety of chamber dimensions can be used. The vapor
deposition chamber is located within a larger vacuum chamber which
surrounds the vapor deposition chamber. The vacuum chamber is
pumped down to a pressure of about 5.0E-6 Torr. Argon is injected
into the vacuum chamber to a pressure of about 3.0 mTorr. The argon
can then optionally be energized into a plasma for the purpose of
precleaning the portions of the NiTi core segment disposed within
the vapor deposition chamber. The precleaning process can be
designed to remove the tenacious oxide layer on the outside surface
of the distal guidewire core section.
[0035] The target material or joinable material which is deposited
on the distal core section by the vapor deposition processing can
be a relatively unreactive metal or alloy such as platinum, gold,
silver or stainless steel or the like. Stainless steel is preferred
because it is inexpensive compared to the other mentioned materials
and the proximal section of the elongate core is typically
constructed of stainless steel which facilitates soldering or
bonding of like materials. The longer the vapor deposition process
is operated for any given core section or other substrate to which
a thin layer of joinable material is deposited, the thicker the
deposited coating will be. The thin layer of joinable material can
be applied at a thickness up to 100 microns, but is preferably
applied at a thickness up to 2 microns. More preferably, the
coating will have a thickness of about 1 to about 2 microns, which
is sufficient for a high integrity solder joint.
[0036] The entire vapor deposition process is preferably
temperature controlled in order to avoid altering the mechanical or
pseudoelastic properties of the distal core section or of any other
material that is be treated by the vapor deposition process. The
vapor deposition processing can be performed at a temperature up to
about 300.degree. C., but is preferably performed at a temperature
of about 200.degree. C. or lower. This vapor deposition process can
be used to deposit any suitable material on any similar or
dissimilar material that requires a surface interface or thin layer
that would facilitate joining.
[0037] The invention has been described herein in terms of a vapor
deposition, preferably a physical vapor deposition process for
joining material. Those skilled in the art will recognize that
other forms of deposition may be employed. Moreover, while
particular forms of the invention have been illustrated and
described, it will be apparent that various modifications can be
made without departing from the spirit and scope of the invention.
Accordingly, it is not intended that the invention be limited,
except as by the appended claims.
* * * * *