Methods of forming catheters with soft distal tips

1. A method of forming a catheter having an elongate shaft and a distal tip, the catheter having a distal end and a proximal end, the elongate shaft comprising an inner layer and an outer layer, the distal tip having a distal end and a proximal end, the method comprising:

flaring a portion of the distal tip proximate the proximal end to form a flared proximal end;

positioning the distal tip such that the flared proximal end of the distal tip overlaps the distal end of the outer layer; and

applying heat and pressure to melt and flow together the outer layer proximate the distal end and the overlapped portion of the flared proximal end of the distal tip, thereby forming a joint between the catheter shaft and the distal tip.

2. The method of claim 1 , wherein applying heat and pressure comprises positioning a shrink-wrap over the overlapped portion of the flared proximal end of the distal tip and applying heat, thereby shrinking the shrink-wrap.

3. The method of claim 2 , further comprising applying a compressive force to the overlapped portion of the distal tip, in addition to that applied by the shrink wrap.

4. The method of claim 2 , further comprising removing the shrink-wrap after forming the joint.

5. The method of claim 1 , wherein the catheter has an outer diameter at the joint between the distal tip and the elongate shaft that is substantially equal to an outer diameter of the shaft at a position proximate the joint.

6. The method of claim 1 , wherein the elongate shaft further comprises an intermediate reinforcing layer that is positioned between the inner layer and the outer layer.

7. The method of claim 6 , wherein the inner layer and the intermediate reinforcing layer extend from the proximal end of the elongate shaft to the distal end of the elongate shaft.

8. The method of claim 6 , wherein the outer layer comprises a proximal portion that extends from the proximal end of the elongate shaft to a position proximal of the distal end of a first polymer and a distal portion that extends from the proximal portion to the distal end of the elongate shaft, the distal portion formed of the same soft material as the distal tip.

9. The method of claim 1 , wherein flaring the proximal end of the distal tip comprises increasing a diameter of the proximal end by about 16 percent.

10. The method of claim 1 , wherein positioning the distal tip comprises positioning the distal tip such that about 0.010 inches to about 0.030 inches of the flared proximal end of the distal tip overlaps the distal end of the outer layer.

11. The method of claim 1 , wherein positioning the distal tip comprises positioning the distal tip such that about 0.020 inches of the flared proximal end of the distal tip overlaps the distal end of the outer layer.

12. A method of forming a catheter comprising an elongate shaft and a distal tip, the catheter having a distal end and a proximal end, the elongate shaft comprising an inner layer and an outer layer, the inner layer extending distally beyond the distal end of the outer layer, the distal tip having a distal end and a proximal end, the distal tip comprising a soft material, the method comprising: providing a distal segment having a distal end and a proximal end, the distal segment formed of the same soft material as the distal tip;

securing the distal segment over the distal end of the inner layer such that the proximal end of the distal segment abuts the distal end of the outer layer;

flaring the proximal end of the distal tip to form a flared proximal end;

positioning the distal tip such that the flared proximal end of the distal tip overlaps the distal end of the distal segment; and

applying heat and pressure to melt and flow together the distal segment and the overlapped portion of the flared proximal end of the distal tip, thereby forming a joint between the catheter shaft and the distal tip.

13. The method of claim 12 , wherein securing the distal segment comprises:

positioning the elongate shaft over a mandrel;

positioning the distal segment over the distal end of the inner layer; and

forming a butt joint between the distal end of the outer layer and the proximal end of the distal segment.

14. The method of claim 12 , wherein applying heat and pressure compnses positioning a shrink-wrap over the overlapped portion of the flared proximal end of the distal tip and applying heat, thereby shrinking the shrink-wrap.

15. The method of claim 14 , further comprising applying a compressive force to the overlapped portion of the distal tip, in addition to that applied by the shrink-wrap.

16. The method of claim 14 , further comprising a subsequent step of removing the shrink-wrap after forming the joint.

17. The method of claim 12 , wherein the catheter has an outer diameter at the joint between the distal tip and the elongate shaft that is substantially equal to an outer diameter of the shaft at a position proximate the joint.

18. The method of claim 12 , wherein the soft material of the distal end of the outer layer and the soft material of the overlapping portion of the soft distal tip, as a result of melting and flowing, form a homogenous material.

19. The method of claim 12 , wherein flaring the proximal end of the distal tip comprises increasing a diameter of the proximal end by about 16 percent.

20. The method of claim 12 , wherein positioning the distal tip comprises positioning the distal tip such that about 0.010 inches to about 0.030 inches of the flared proximal end of the distal tip overlaps the distal end of the outer layer segment.

21. The method of claim 12 , wherein positioning the distal tip comprises positioning the distal tip such that about 0.020 inches of the flared proximal end of the distal tip overlaps the distal end of the outer layer segment.

22. The method of claim 12 , wherein the elongate catheter shaft has an outer diameter of less than about 0.0710 inches.