Axis 7100 Installationsanleitung PDF herunterladen (Seite 178)

Workpiece Alignment

Advanced Dicing Technologies Ltd.

6.1-16

spiral search starts from the model situated after the third model. The

search ending positions are the same as for the second model.

In case both directional spiral searches for the second model fail, the

system starts the whole alignment procedure again, on the upper

of the

wafer. This includes finding the first model again, and searching for the

second and the third models using index spiral search and directional

search if needed.

If the system still fails to find the second model, the alignment procedure is

repeated again on the lower

of the wafer. If finding the second model

still fails, the whole alignment procedure fails and the user assistance is

required.

The algorithm for finding the third model is identical to that for finding the

second model, given above.

The directional search areas are limited by the align area of the wafer. The

search is never performed outside the Align Area (parameter defined in

the Align category).

This limitation may cause any of the directional spiral searches not to take

place.

6.1.3.3.2 Main Model Detection

Once the low models have been found, the system starts looking for the

main model to perform the fine alignment. If the main model is not found,

the system performs an index spiral search.

If the index spiral search fails, the system performs one directional spiral

search, starting from the model situated next to the first model, in the

direction of the second model on the X-Axis, as long as the distance from

the second model is more than ½ of the align area.

Unlike the search for low models, the search for main models is carried out

in the direction from the workpiece periphery to the center as shown in

Figure 6-14.

In case this search fails, the system begins the fine (main) alignment over

again on the upper

of the wafer. This includes a spiral search and a

Note: The search for the second model is performed in the direction from the

center to the edge and the search for the third model is performed from the

edge towards the center.

Figure 6-14: Main Model Search

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Axis 7100 Installationsanleitung Seite 178