Process for laser joining dissimilar metals and endoluminal stent with radiopaque marker produced thereby

• US 6,554,854 B1
• Filed: 12/10/1999
• Issued: 04/29/2003
• Est. Priority Date: 12/10/1999
• Status: Expired due to Fees

• Current Assignee: Boston Scientific Scimed, Inc. (Boston Scientific Corporation)
• Original Assignee: Scimed Life Systems Incorporated (Boston Scientific Corporation)
• Inventors: Flanagan, Aiden
• Primary Examiner(s): Milano, Michael J.
• Assistant Examiner(s): Bui, Vy Q.
• Application Number:
  US09/458,851
• Time in Patent Office: 1,236 Days
• Field of Search: 623/1.46, 623/1.15, 623/1.34, 623/1.44, 606/194, 606/195, 606/198, 148/22, 219/121.63, 219/121.64
• US Class Current: 623/1.1
• CPC Class Codes: A61B 90/39 Markers, e.g. radio-opaque or breast lesions markers
• CPC Class Codes: A61F 2/90 characterised by a net-like or mesh-like structure
• CPC Class Codes: B23K 2103/05 Stainless steel
• CPC Class Codes: B23K 2103/08 Non-ferrous metals or alloys
• CPC Class Codes: B23K 2103/18 Dissimilar materials
• CPC Class Codes: B23K 26/244 Overlap seam welding
• CPC Class Codes: B23K 26/26 of rectilinear seams
• CPC Class Codes: B23K 26/323 involving parts made of dissimilar metallic material

Abstract

A process for laser joining a first metal, having a first reflectance curve as a function of wavelength, such as nitinol or stainless steel, and a second metal, having a second reflectance curve, such as gold. The process comprises placing the first and second metals in contact with one another then exposing at least one of the first metal and second metal to a laser beam having a wavelength selected from an optimal range of wavelengths over which the reflectance curves of the two metals essentially overlap. The first metal may comprise a first metal element having a sufficiently low heat sink capacity and a sufficiently lesser reflectance than the second metal at wavelengths outside the optimal range of wavelengths such that laser joining at such wavelengths exposes the first metal to a risk of excessive melting, vaporization, or cutting through the first metal element. The first metal element may be a stent adapted for endoluminal deployment, wherein the second metal is a radiopaque marker relative to the first metal. A stent produced by this process may comprise one or more first metal elements with a radiopaque marker metal attached to one or more portions of at least one element, the radiopaque marker comprising the second metal attached to the first metal by a weld, a clad layer of the second metal over the first metal, or an alloy layer of the two metals over the first metal.

Claims

1. A process for laser joining a first metal with a second metal, the first metal comprising an element of a stent adapted for endoluminal deployment and having a first reflectance curve as a function of wavelength, the second metal comprising a radiopaque marker relative to the first metal and having a second reflectance curve, die first metal having a sufficiently lesser reflectance than the second metal outside an optimal range of wavelengths over which the first reflectance curve and the second reflectance curve essentially overlap such that laser processing at a wavelength outside the optimal range exposes the first metal to a risk of excessive melting, vaporization, or cutting through the first metal clement, the process comprising placing the first metal in contact with the second metal and exposing at least one of the first metal and second metal to a laser beam having a wavelength selected from the optimal range of wavelengths, the process comprising first creating pitholes in the first metal stent element and then filling the pitholes with the second metal.

2. The process of claim 1 wherein the step of exposing at least one of the first metal and the second metal to a laser beam comprises welding the second metal to the first metal, cladding the first metal with the second metal, alloying the first metal and the second metal, or a combination thereof.

3. The process of claim 1 wherein the second metal is one of:

gold or copper.

4. The process of claim 1 wherein the first metal is one of:

nickel, titanium, iron, or an alloy thereof.

5. The process of claim 4 wherein the alloy comprises one of:

nitinol or stainless steel.

6. The process of claim 4 wherein the second metal is gold.

7. The process of claim 6 wherein the optimal range of wavelengths consists of:

wavelengths less than approximately 0.55 μ

m or greater than approximately 3 μ

m, wherein the first metal comprises an element of a stent adapted for endoluminal deployment and the second metal comprises a radiopaque marker relative to the first metal.

8. The process of claim 7 wherein the optimal range of wavelengths consists of:

wavelengths between approximately 0.40 μ

m to approximately 0.55 μ

m.

9. The process of claim 8 wherein the selected wavelength is approximately 0.532 μ

m.

10. The process of claim 9 wherein the laser beam is generated by a frequency-doubled Nd:

YAG laser.

11. The process of claim 1 wherein the first metal comprises an element of a stent adapted for endoluminal deployment and the second metal comprises a radiopaque marker relative to the first metal and the laser beam is generated by a YAG laser.

12. The process of claim 11 wherein the YAG laser is an Nd:

YAG laser.

13. The process of claim 1 wherein the first metal comprises one of:

nitinol or stainless steel, and the second metal comprises one of;

gold or copper.

14. The process of claim 1 further comprising adding an additional layer of the second metal over the first metal stent element and the pitholes filled with the second metal.

15. The process of claim 1 further comprising attaching the radiopaque marker second metal to the stent element first metal in a pattern comprising one of:

an unbroken line along the stent element, a broken line along the stent element, a dot pattern along the stent element, or a combination thereof.

16. The process of claim 1 wherein the stent element first metal has a peripheral surface, the process further comprising attaching the radiopaque marker second metal to the stent element first metal over:

all of the peripheral surface of the element or a part of the peripheral surface of the element.

17. A stent produced by the process according to claim 1.

18. A stent produced by the process according to claim 13.

19. The process of claim 7, wherein the step of exposing at least one of the first metal and the second metal to a laser beam comprises welding the second metal to the first metal.

20. The process of claim 7, wherein the step of exposing at least one of the first metal and the second metal to a laser beam comprises cladding the first metal with the second metal.

21. The process of claim 1, wherein the step of placing the first metal in contact with the second metal comprises placing a wire of the first metal in contact with a wire of the second metal.