Advanced Packaging Technology Conference Proceedings


BOARD-LEVEL RELIABILITY FOR LEAD-FREE QFP ASSEMBLY

Author: Shan-Pu Yu
Company: ITRI
Date Published: 6/12/2001   Conference: Advanced Packaging Technology


Abstract: A commercial lead-free QFP component with environmentally benign Sn-3.0Ag-0.5Cu solder paste and the conventional 63Sn-37Pb solder pastes was used in this study. The thermal shock and random vibration test were used to investigate the board level reliability. After the reliability test, a pull-off tester on the solder joints of QFP samples was used for measuring the pull-forces of the solder joints.

All samples passed the electrical test after 2500 thermal shock cycles and also passed after random vibration test after twice tests. In this study, both Sn-Pb and lead-free Sn-Ag-Cu solder joints of QFP possesses good board-level reliability.

The failure of the Sn-Pb as-soldered joints occurs at the lead / solder interface results from most thermal stress locates due to CTE mismatch while cool down. The failure of the Sn-Ag-Cu solder joints some occurs at the lead / solder interface like Sn-Pb does, but a few samples fails at the Cu / PCB interface. Both Sn-Pb and Sn-Ag-Cu solder joints fails at the lead / solder interface after thermal shock test. However, more defects and coarsened grains would cause lower pull-forces of the Sn-Pb solder joints. Further investigations on the failure mechanism are still understudy.

Key words : lead-free, QFP, board-level reliability, solder joints.



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