Ribbon bonding in an electronic package
A flexible conductive ribbon is ultrasonically bonded to the surface of a die and terminals from a lead frame of a package. Multiple ribbons and/or multiple bonded areas provide various benefits, such as high current capability, reduced spreading resistance, reliable bonds due to large contact areas, lower cost and higher throughput due to less areas to bond and test.
1. A method of providing an electrical interconnection between a first element and a second element, the method comprising the steps of:
a) ultrasonically bonding a first portion of a ribbon material to a first element using a bonding tool to form a first bonded area, the ribbon material having a rectangular cross section;
b) extending a length of the ribbon material, continuous with the first portion, to a second element after step a); and
c) bonding a second portion of the ribbon material to the second element using the bonding tool to form a second bonded area, thereby providing an electrical interconnection between the first element and the second element,
wherein at least one of the first bonded area and the second bonded area are formed at an angle that is non-perpendicular to a length along which the ribbon material extends from the first element to the second element.
2. The method of claim 1 , wherein the ribbon material having the rectangular cross section is provided such that a ratio of a width of the ribbon material to a thickness of the ribbon material is in a range of 7-13.
3. The method of claim 1 , wherein step a) includes ultrasonically bonding the first portion of the ribbon material to a semiconductor die supported by a substrate.
4. The method of claim 3 , wherein the substrate is a leadframe, and step c) includes bonding the second portion of the ribbon material to a lead of the leadframe.
5. The method of claim 1 , wherein each of the first element and the second element comprise a semiconductor die.
6. The method of claim 1 , wherein extending the length of the ribbon material includes feeding the length of the ribbon material after step a).
7. The method of claim 6 , wherein the feeding the length of the ribbon material includes guiding the length of the ribbon material with a ribbon guide.
8. The method of claim 1 , further including the step of:
d) cutting the ribbon material after step c).
9. The method of claim 1 , wherein step b) includes extending the length of the ribbon material such that the length follows an arc shape.
10. The method of claim 1 , wherein step a) includes ultrasonically bonding the first portion of the ribbon material to the first element such that the first portion of the ribbon material includes a first bonded portion, a second bonded portion, and a third bonded portion, the first bonded portion being closest to the second element in comparison to a position of the second bonded portion and the third bonded portion, the second bonded portion being positioned between the first bonded portion and the third bonded portion, wherein when measured in a direction along which the ribbon material extends (1) a distance between a centerline of the second bonded portion to a centerline of the first bonded portion is less than (2) a distance between a centerline of the third bonded portion to the centerline of the second bonded portion.
11. The method of claim 1 wherein a thickness of the ribbon material is in a range of between 2-10 mils.
12. The method of claim 1 wherein a width of the ribbon material is in a range of between 20-100 mils.
13. The method of claim 1 wherein step (a) includes ultrasonically bonding the first portion of the ribbon material at a frequency higher than 60 kHz.
14. The method of claim 1 wherein the ribbon material is an aluminum ribbon material.
15. The method of claim 1 wherein the ribbon material is a copper ribbon material.
16. The method of claim 1 wherein the first element is part of a power semiconductor device.
17. The method of claim 1 wherein the first element is part of a power MOSFET.
18. The method of claim 1 wherein the first element is part of a TO-220 semiconductor package.
19. The method of claim 1 wherein the first element is part of an SO-8 semiconductor package.
20. The method of claim 1 wherein the first element is part of an SO-12 semiconductor package.
21. The method of claim 1 wherein the bonded first portion of the ribbon material and the bonded second portion of the ribbon material are formed at different angles from one another.
22. The method of claim 1 wherein step a) includes ultrasonically bonding the first portion of the ribbon material to the first element such that the first portion of the ribbon material includes a first bonded portion, a second bonded portion, and a third bonded portion.
23. The method of claim 22 , wherein step a) includes forming a first loop of the ribbon material between the first bonded portion and the second bonded portion, and forming a second loop of the ribbon material between the second bonded portion and the third bonded portion.
24. A method of providing an electrical interconnection between a first element and a second element, the method comprising the steps of:
a) ultrasonically bonding a first portion of a ribbon material to a first element using a bonding tool to form a first bonded area, the ribbon material having a rectangular cross section;
b) extending a length of the ribbon material, continuous with the first portion, to a second element after step a); and
c) bonding a second portion of the ribbon material to the second element using the bonding tool to form a second bonded area, thereby providing an electrical interconnection between the first element and the second element,
wherein the first bonded area and the second bonded area are formed at different angles from one another.
25. A method of providing an electrical interconnection between a first element and a second element, the method comprising the steps of:
a) ultrasonically bonding a first portion of a ribbon material to a first element using a bonding tool, the ribbon material having a rectangular cross section;
b) extending a length of the ribbon material, continuous with the first portion, to a second element after step a); and
c) bonding a second portion of the ribbon material to the second element using the bonding tool, thereby providing an electrical interconnection between the first element and the second element,
wherein step a) includes ultrasonically bonding the first portion of the ribbon material to the first element such that the first portion of the ribbon material includes a first bonded portion, a second bonded portion, and a third bonded portion, the first bonded portion being closest to the second element in comparison to a position of the second bonded portion and the third bonded portion, the second bonded portion being positioned between the first bonded portion and the third bonded portion, wherein when measured in a direction along which the ribbon material extends (1) a distance between a centerline of the second bonded portion to a centerline of the first bonded portion is less than (2) a distance between a centerline of the third bonded portion to the centerline of the second bonded portion such that a length of ribbon material between the centerline of the third bonded portion and the centerline of the second bonded portion is greater than a length of ribbon material between the centerline of the second bonded portion and the centerline of the first bonded portion.