Process development for chip-size package mounting

Chip Scale Packages provide an opportunity to achieve miniaturisation in IC packaging. The ChipArray BGA (CABGA) is a type of CSP which consists of a wire-bonded die on a rigid organic substrate. This package type can accommodate a relatively high number of I/O. For small dice with a low number of I/O, there is a trend towards wafer-level CSP. These are made while the dice are still in a wafer, which is very costeffective.

These pack-age types offer the same level of miniaturisation as in flip-chip technology. The UltraCSP is a wafer-level CSP that consists of a rerouted flip-chip. Within Philips, the process for mounting CABGAs and UltraCSPs on FR4 substrates is being developed. Components with eutectic solder-bumps at pitches of 0.5 and 0.4 mm are included in the test programme. Successful mounting results have been obtained: a soldered joint defect level of 0-97 ppm (on joint level, 95% confidence) has been demonstrated for the CABGAs with bump pitches of 0.5 mm, and the intrinsic lifetime in a temperature-cycle test meets the requirement for mobile communication equipment. The mounting process for components with a bump pitch of 0.4 mm is much more critical compared to a pitch of 0.5 mm, especially with re-spect to placement accuracy and placement force.

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