Apparatus and method for laser welding of ribbons

• US 6,717,100 B2
• Filed: 10/25/2002
• Issued: 04/06/2004
• Est. Priority Date: 10/22/1999
• Status: Expired due to Fees

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Ruben, David A.
• Primary Examiner(s): Evans, Geoffrey S
• Application Number:
  US10/280,965
• Publication Number:
  US 20030127434A1
• Time in Patent Office: 529 Days
• Field of Search: 219/121.63, 219/121.64
• US Class Current: 219/121.64
• CPC Class Codes: B23K 2101/32 Wires
• CPC Class Codes: B23K 2101/38 Conductors
• CPC Class Codes: B23K 2103/08 Non-ferrous metals or alloys
• CPC Class Codes: B23K 2103/10 Aluminium or alloys thereof
• CPC Class Codes: B23K 2103/12 Copper or alloys thereof
• CPC Class Codes: B23K 2103/26 Alloys of Nickel and Cobalt and Chromium
• CPC Class Codes: B23K 26/22 Spot welding
• CPC Class Codes: B23K 26/40 taking account of the properties of the material involved
• CPC Class Codes: H01L 2224/45014 Ribbon connectors, e.g. rectangular cross-section
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45124 Aluminium (Al) as principal constituent
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/45147 Copper (Cu) as principal constituent
• CPC Class Codes: H01L 2224/45155 Nickel (Ni) as principal constituent
• CPC Class Codes: H01L 2224/4554 Coating
• CPC Class Codes: H01L 2224/45565 Single coating layer
• CPC Class Codes: H01L 2224/45655 Nickel (Ni) as principal constituent
• CPC Class Codes: H01L 2224/45669 Platinum (Pt) as principal constituent
• CPC Class Codes: H01L 2224/48 of an individual wire connector
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48472 : the other connecting portion not on the bonding area also being a wedge bond, i.e. wedge-to-wedge
• CPC Class Codes: H01L 2224/78313 : Wedge
• CPC Class Codes: H01L 2224/78314 : Shape
• CPC Class Codes: H01L 2224/78318 : inside the capillary
• CPC Class Codes: H01L 2224/85 : using a wire connector
• CPC Class Codes: H01L 2224/85205 : Ultrasonic bonding
• CPC Class Codes: H01L 2224/85207 : Thermosonic bonding
• CPC Class Codes: H01L 2224/85214 : using a laser
• CPC Class Codes: H01L 2224/85238 : using electric resistance welding, i.e. ohmic heating
• CPC Class Codes: H01L 24/45 : of an individual wire connector
• CPC Class Codes: H01L 24/48 : of an individual wire connector
• CPC Class Codes: H01L 24/78 : Apparatus for connecting with wire connectors
• CPC Class Codes: H01L 24/85 : using a wire connector wire bonding in general B23K20/004
• CPC Class Codes: H01L 2924/00 : Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 : the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/0002 : Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/01002 : Helium [He]
• CPC Class Codes: H01L 2924/01006 : Carbon [C]
• CPC Class Codes: H01L 2924/01007 : Nitrogen [N]
• CPC Class Codes: H01L 2924/01013 : Aluminum [Al]
• CPC Class Codes: H01L 2924/01018 : Argon [Ar]
• CPC Class Codes: H01L 2924/01019 : Potassium [K]
• CPC Class Codes: H01L 2924/01028 : Nickel [Ni]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/01039 : Yttrium [Y]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• CPC Class Codes: H01L 2924/01058 : Cerium [Ce]
• CPC Class Codes: H01L 2924/0106 : Neodymium [Nd]
• CPC Class Codes: H01L 2924/01078 : Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/12042 : LASER
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/181 : Encapsulation
• CPC Class Codes: H01L 2924/19041 : being a capacitor
• CPC Class Codes: H01L 2924/206 : Length ranges
• CPC Class Codes: H01L 2924/20752 : larger or equal to 20 microns less than 30 microns
• CPC Class Codes: H01L 2924/40252 : CO2 LASER

Abstract

An apparatus and method are provided for using laser energy in an automated bonding machine to effect laser welding of ribbons and other connectors, particularly conductive ribbons in microelectronic circuits. The apparatus and method allow bonding and connection of microelectronic circuits with discrete heating avoiding heat damage to peripheral microelectronic components. The apparatus and method also allow bonding of flexible materials and low-resistance materials, and are less dependant on substrate and terminal stability in comparison to existing bonding methods. The bonding method leads to decreased apparatus wear in comparison to existing bonding methods.

Claims

1. A method for bonding of ribbon to a first substrate, comprising:

disposing a segment of an elongated laser-weldable ribbon through a threading aperture of a bond head, wherein said threading aperture comprises structure constraining lateral movement of the elongated laser-weldable ribbon, and wherein a portion of said elongated laser-weldable ribbon passes between an articulated bond head and a first substrate, and wherein an aperture formed in the articulated bond head is adapted to permit passage of a laser beam therethrough;

aiming a laser beam source so that the laser beam passes through the aperture and impinges upon a portion of the elongated laser-weldable ribbon; and

firing the laser beam source for a predetermined time sufficient to form a first weld nugget at a first bond site, the first weld nugget consisting of material from both the elongated laser-weldable ribbon and the first substrate.

2. A method according to claim 1, wherein the laser beam is focused adjacent the bond site.

3. A method according to claim 1, wherein the elongated laser-weldable ribbon is an electrically conductive material having a geometric cross-sectional shape, a round cross-sectional shape, an elongated cross-sectional shape or a substantially rectangular cross-sectional shape.

4. A method according to claim 1, wherein the elongated laser-weldable ribbon comprises at least a one of the group:

nickel-clad copper, platinum, nickel 505, nickel 270, aluminum 6061.

5. The method of claim 1, wherein the laser beam source operates either in a pulsed mode or in a continuous wave mode.

6. A method according to claim 1, wherein said laser beam source is a neodymium yttrium aluminum garnate laser source, an argon-ion laser source, a carbon dioxide laser source, or a copper vapor laser source.

7. A method according to claim 1, further comprising the steps of:

moving the articulated bond head relative to a work piece to position the articulated bond head adjacent to a second bond site disposed on a second substrate while playing out the elongated laser-weldable ribbon from a ribbon spool;

disposing the elongated laser-weldable ribbon between the articulated bond head and the second substrate;

aiming the laser beam source so that the laser beam passes through the aperture and impinges upon the elongated laser-weldable ribbon; and

firing the laser beam source for a predetermined time sufficient to form a second weld nugget at the second bond site, the second weld nugget consisting of material from both the elongated laser-weldable ribbon and the second substrate.

8. The method of claim 7, further comprising the additional step of severing the elongated laser-weldable ribbon adjacent the second bond site.

9. The method of claim 8, wherein the elongated laser-weldable ribbon is severed by the articulated bond head to form a wedge bond.

10. The method of claim 1, further comprising the steps of:

moving the articulated bond head horizontally, vertically or radially with respect to a location proximate to the first bond site, and

firing the laser for an additional predetermined time sufficient to form a security weld.

11. An apparatus for bonding a section of laser-weldable ribbon to at least one substrate pad, comprising:

a laser beam generator;

a bond foot moveable with respect to the laser beam generator and having an aperture formed through a portion of said bond foot for passage of a laser beam emitted from the laser beam generator therethrough;

aiming means for directing the laser beam to a bond site; and

a ribbon-pathway means for smoothly deploying a length of elongated laser-weldable ribbon material from a ribbon source to a position adjacent the aperture.

12. An apparatus according to claim 11, wherein the ribbon source comprises a portion of elongated laser-weldable ribbon disposed upon a reciprocating ribbon-storing spool;

and further comprising means for preventing the uncontrolled release of the portion of ribbon from the ribbon-storing spool.

13. An apparatus according to claim 12, wherein the preventing means comprises a mechanical clamp.

14. An apparatus according to claim 13, wherein the ribbon-pathway means further comprises structure disposed on opposing sides of a ribbon pathway to restrain the elongated laser-weldable ribbon from moving laterally relative to a major longitudinal axis of said elongated laser-weldable ribbon.

15. An apparatus according to claim 11, further comprising magnification means adapted for visually magnifying a region, said region including at least a portion of the bond site.

16. An apparatus according to claim 15, wherein the magnification means further comprises at least one magnifying lens coupled to a part of the apparatus and disposed adjacent a mirror directing the laser beam to the bond site and wherein the magnifying lens and the mirror have different optical paths to the bond site.

17. An apparatus according to claim 11, wherein the aiming means further comprises an optic fiber coupled to the laser beam generator at a proximal end and having a portion disposed in the aperture of the bond foot and wherein a distal end terminates adjacent the bond site.

18. The apparatus of claim 17, wherein the optic fiber adjacent the bond head is firmly coupled to a portion of the bond head.

19. An apparatus according to claim 11, wherein the laser beam generator is a one of the following:

a neodymium yttrium aluminum garnate, an argon-ion, a carbon dioxide, or a copper vapor laser beam generator.

20. An apparatus according to claim 11, further comprising a means for articulating the bond head relative to the bond site.

21. A bonding apparatus for connecting a segment of a ribbon to at least one substrate pad member that is coupled to a stationary, substantially unconstrained work piece to form a bond connection at a bond site, the apparatus comprising:

a stationary laser beam source;

a pedestal moveable with respect to the stationary laser beam source and including a bond foot with an aperture for admitting a laser beam emanating from the laser beam source and a ribbon alignment means for positioning a ribbon between the bond site and the bond foot such that a part of the ribbon aligned with said aperture; and

an aiming structure to direct the laser beam at the bond site;

wherein said ribbon alignment means further comprises structure disposed on at least one side of a predetermined ribbon pathway to constrain a portion of ribbon from twisting or slipping out registration of said predetermined ribbon pathway.