Proactive Verification of Strip Y-Index to Mitigate Gross Misaligned Cut due to Mismatched Unit Pitching

Abstract

Shopfloor practices that when the first cut line was aligned with the hairline, actual blade cut, and saw street of the strip, the succeeding cut lines will automatically follow with the same alignment. Considering various factors that affect the condition of the strip, it was recommended to verify the succeeding cut lines of the strip to project if the hairline will still be aligned with the saw street as cutting goes on. Unfortunately, verification of succeeding cut lines was usually skipped and refer only with the first cut alignment as reference. Thus, end up risking the units for possible cutting misalignment. Cutting misalignment can be encountered when the programmed unit pitching measurement was mismatched with the actual unit pitch of the strip. However, mismatching of the unit pitch can be anticipated through y-indexing where the saw street of the strip will be verified for alignment with the hairline along the succeeding cut lines. Frequent occurrence of mismatched unit pitching was brought about by the strip condition after series of assembly processes that expands and retracts the strip. With the mentioned scenario which has been encountered from different semiconductor assembly plants, it was best to verify the y-indexing of the strip on top of verification on the first cut line alignment. Application of y-indexing verification is essential for the entrapment and correction of mismatched unit pitching. Rejection of units due to misaligned cuts can also be prevented. Assistance of operators to adjust and monitor the hairline to compensate the actual pitching was also avoided as early as first cut line verification.