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 electrically connecting an electronic device to an external lead, comprising:
ultrasonically bonding, using a bond tool in connection with an ultrasonic bonding machine, a first portion of a conductive flexible ribbon to a first portion on a conductive upper surface of the device, the conductive flexible ribbon being a multi-layer ribbon including a lower aluminum layer positioned below an upper copper layer;
feeding ribbon material to form a loop between (1) the first portion on the conductive upper surface and (2) the external lead; and
bonding, using the bonding tool, a second portion of the conductive flexible ribbon to the external lead, wherein the entire ribbon is flexible.
2. The method of claim 1 , wherein the electronic device is a semiconductor die.
3. The method of claim 1 , further comprising ultrasonically bonding a third portion of the ribbon to a second portion on the conductive upper surface of the device.
4. The method of claim 1 , further comprising:
ultrasonically bonding a first portion of a second ribbon to a second portion on the conductive upper surface of the device; and
bonding a second portion of the second ribbon to the external lead.
5. The method of claim 1 , wherein the ultrasonically bonding is performed with the bond tool having a diamond-shaped pattern.
6. The method of claim 1 , further comprising cutting the ribbon after the bonding.
7. The method of claim 6 , wherein the ultrasonic bonding and cutting are along parallel lines and may be performed at different angles.
8. The method of claim 1 , wherein the lower aluminum layer is a bonding layer and the upper copper layer is a conductive layer overlying the bonding layer.
9. The method of claim 8 , wherein the ribbon further comprises a coupling layer overlying the conductive layer.
10. The method of claim 1 , wherein the conductive upper surface is aluminum.
11. The method of claim 4 , wherein the first and second ribbon are parallel to each other.
12. The method of claim 3 , wherein the first and second portions on the conductive surface are between gate fingers.
13. The method of claim 1 , further comprising ultrasonically bonding a first portion of a second ribbon to the first portion on the conductive surface, wherein the second ribbon overlies the ribbon.
14. A method of electrically connecting an electronic device to an external lead, comprising:
(1) ultrasonically bonding a first portion of a flexible conductive ribbon to a first portion on a conductive upper surface of the device;
(2) bonding a second portion of the flexible conductive ribbon to the external lead, wherein the entire ribbon is flexible, such that between steps (1) and (2 ) a first ribbon loop has been bonded between the upper surface of the device and the external lead; and
(3) bonding a second ribbon loop between the upper surface of the device and the external lead, the second ribbon loop being positioned above the first ribbon loop in a stacked configuration.
15. The method of claim 14 , further comprising bonding a third portion of the ribbon to a second portion on the conductive upper surface of the device.
16. The method of claim 1 wherein the copper layer is thicker than the aluminum layer.
17. The method of claim 1 further comprising a top aluminum layer positioned above the upper copper layer.
18. The method of claim 14 wherein the electronic device is a semiconductor die.
19. The method of claim 14 further comprising ultrasonically bonding a third portion of the ribbon to a second portion on the conductive upper surface of the device.
20. The method of claim 14 wherein the ultrasonically bonding is performed with a bond tool having a diamond-shaped pattern.
21. The method of claim 14 further comprising cutting the ribbon after steps (1) and (2).
22. the method of claim 14 wherein the flexible conductive ribbon is a multi-layer ribbon including a lower aluminum layer positioned below an upper copper layer.
23. The method of claim 22 wherein the lower aluminum layer is a bonding layer and the upper copper layer is a conductive layer overlying the bonding layer.
24. The method of claim 23 wherein the flexible conductive ribbon further comprises a coupling layer overlying the conductive layer.
25. The method of claim 22 wherein the copper layer is thicker than the aluminum layer.
26. The method of claim 22 further comprising a top aluminum layer positioned above the upper copper layer.
27. The method of claim 14 wherein the conductive upper surface comprise aluminum.