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Board-level and package-level drop reliability is of critical importance for RF MEMS packages. In this paper, we present a numerical study of reliability of RF MEMS packages during board-level and package-level drop testing. The RF MEMS package consists of a 3.8 mm × 2.5 mm × 0.5 mm RF MEMS die flip-chip assembled on a 5.2 mm × 5.2 mm × 0.4 mm LTCC substrate using lead-free solder balls and a metal lid soldered down on the LTCC substrate to cover the RF MEMS die. The board-level and package-level drop modeling were conducted in accordance with JEDEC standards JESD22-B111 and JESD22-B110A, respectively. The support excitation method was employed to investigate the transient response of the packages. With board-level drop modeling, it was found that the maximum peeling stress in the land grid array (LGA) on the test board side was approximately 170 MPa when the package was mounted on the test board center, and LGA stress reduced to approximately 80 MPa when the package was mounted on the test board edge. As high peeling stress may cause fracture of the intermetallic compound in the solder, the modeling result suggests that the RF MEMS package be placed near the board edge or pins in handheld electronic products. A parametric study of the impact, peak acceleration and pulse duration, was also conducted. It was observed that the maximum stress increased with higher peak acceleration. The maximum stress, however, did not vary monotonically with pulse duration. Package-level drop modeling revealed that the failure of the RF MEMS package would be primarily driven by the inertial force. The transient response of the package synchronized with the drop impact. The maximum stress in the package did not appear in the solder balls but in the seal ring that connects the metal lid to the LTCC substrate. The modeling result indicates that it is important to carry out hermeticity tests before and after package-level drop tests to ensure the package integrity.Copyright © 2009 by ASME |
