Patent Application
20080073408
An example of a preferred embodiment of a bonding apparatus in accordance with the invention will now be described with reference to the accompanying drawings, in which:
The bonding tool is arranged over an electronic device 20 to be bonded, which may comprise a die mounted onto a leadframe. Wire connections are to be made between the die and the leadframe. A clamping device, which may be in the form of a window clamp 22, is located at a first position to clamp the electronic device 20 to a worktable during bonding. The window clamp 22 has an opening or window to expose a bonding area on the electronic device 20 at which wire bonding is to be conducted, for access by the capillary 14.
During operation, bonding wire hangs from the tip of the capillary 14. The EFO torch 18 produces a spark that melts the wire into a molten ball. The ball of molten wire is then bonded to the electronic device, as explained above.
According to the preferred embodiment of the invention, the EFO torch mounting 16 is movable to change the height of the EFO torch 18, and the EFO torch 18 can thus be located at a lower position than in the conventional apparatus wherein the EFO torch mounting is fixed. In this case, the EFO torch 18 may even be moved to a height 28 that is at or below the top surface of the window clamp 22 during bonding. However, it should still be positioned higher than any ribs or other structure that is present across the opening of the window clamp 22, which should be avoided. At this low height, the capillary 14 needs to travel a shorter distance 24 to move between the electronic device 20 and a position adjacent to the EFO torch 18. Hence, travel time needed for the capillary to perform bonding is reduced. Moreover, the height of the EFO torch 18 is preferably fixed close to the electronic device 20 for the bonding of multiple bonding positions on the electronic device 20 so that bonding speed is further optimized by reducing unnecessary motion.
The EFO torch mounting 16 is pivotally mounted at a pivot 34 between the EFO torch 18 and the voice coil motor 32, which pivot 34 is mounted onto the wire bonding apparatus 10 or some other support. Upon driving of the EFO torch mounting 16 by the voice coil motor 32, the EFO torch 18 is made to move upwards or downwards relative to the horn 12 and capillary 14 of the bonding tool.
A position feedback sensor 36 is preferably included to monitor the position of the EFO torch mounting 16, and therefore of the EFO torch 18, at all times. With the position feedback sensor, the height of the EFO torch 18 can be controlled and programmed to any level by providing corresponding commands to the voice coil motor 32. For travel between two fixed levels, generally only the actuator is needed. However, for increased flexibility in having multiple programmable heights for positioning the EFO torch 18 within its travel range, both the actuator and position feedback sensor 36 would preferably be required.
It should be appreciated that the movable EFO torch mounting 16 in accordance with the preferred embodiment of the invention can be used to shorten the travel distance of the bonding tool from a position where sparking is performed to create a molten ball and a bonding position during bonding. This is useful to reduce bonding cycle time and increase the productivity of the wire bonding apparatus 10 as compared to the prior art.
The invention described herein is susceptible to variations, modifications and/or additions other than those specifically described and it is to be understood that the invention includes all such variations, modifications and/or additions which fall within the spirit and scope of the above description.
