Enhanced Polymer Passivation Layer for Wafer Level Chip Scale ...

Table 2.2 Comparison of Wafer Level Chip Scale Packaging Technologies[6]
2.2.2 WLCSP Process Flow
In the semiconductor industry, front-end corresponds to the wafer fabrication process
while back-end corresponds to product assembly, packaging and testing operations [36]. There
are two types of back-end process flows, one is for wafers with in-situ bump formation and the
other is for wafers requiring the placement of preformed solder balls for larger bumps. Figure 2.5
shows two separate paths for the backend processing of bumped wafers. One processes wafers
with bumps already formed in the bumping front end and the other includes the process steps
required for reflowing preformed solder balls [37].
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