Fab integrated packaging (FIP): A new concept for high reliability wafer-level chip size packaging

Wafer Level Packaging has the highest potential for future single chip packages. The package is completed directly on the wafer then singulated by dicing for the assembly in a flip chip fashion. All packaging and testing operations of simulated dice will be replaced by whole wafer fabrication and wafer level testing. The result is a technology which leads the way to Fab Integrated Packaging (FIP). An evaluation of the reliability of a new Wafer-Level Chip Scale Package (WL-CSP) was done in the FIP program, a joint development program between Fraunhofer IZM and Motorola. As a CSP the FIP-CSP eliminates underfill operation during flip-chip bonding using high through-put SMT assembly lines. The technological structure of this FIP-CSP is a pad redistributed die with a solder ball array. A stress compensation layer (SCL) embeds the solder balls before second solder balls are stencil printed or placed on top of embedded balls. The reliability of this wafer-level CSP presented here was simulated and evaluated by test samples. The test chip was a 1 cm×1 cm square chip which was redistributed to an 14×14 ball array with a pitch of 0.5 mm. JEDEC Level 3, 1000 cycles AATC (-55°C/+125°C) and 48 h Autoclave on component level were passed. On board level 1000 hours humidity storage at 85°C (85/85 test) and 1000 cycles -55/+125°C were passed.