3 Automatic Needle Alignment
3-15
3.3 Pad
Alignment
Low mag. pad alignment
High mag. pad alignment
Detected needle tip position
Position/size of
registered pad
Wafer theta alignment
In the pad alignment, the probe tip images obtained
through the probe tip viewing camera are fitted to
the registered pad locations and sizes in the low
magnification and then in the high magnification.
The left figure of the low magnification process
shows that the probe tip images are compared and
fitted to the pattern of a registered pad group.
In the high magnification view, each probe tip is
reviewed while changing the camera height to
determine the probe tip position and height
accurately.
When the tip position and height have been
determined, two windows appear; the outer window
shows the corresponding pad area and the inner
window shows the determined tip position, as
shown left.
When the pad alignment has finished, Chuck
comes under the wafer alignment camera, where
automatically starts the wafer theta alignment in
reference to the determined probe card theta angle.
