Methods for Failure Analysis and Diagnosis of Millimeter-Wave System-in-Packages

This paper presents a sequence of affordable methods applied to diagnose a millimeter-wave system-in-package. The module used in this paper is a 60 GHz transceiver with a waveguide interface, designed to transmit 8 dBm of saturated power. It consists of a flip-chipped RFIC, a multi-layer organic substrate, a metal enclosure with a standard waveguide interface, passive components and a 30-pin connector. The first measured output power was 3 to 6 dB below the desired value over the 60 GHz band. Thus, all parts of the module were thoroughly investigated to detect the cause of power drop. By 3-D electromagnetic simulation of the enclosure, the cavity modes and power leakage in the enclosure were detected, which were verified by measuring the scattering parameters of the back to back configuration. By statistical analysis of the scanning electron microscope images of the cross section of 10 SiP samples, the realized dimensions of the fabricated substrate were measured and applied to the post-fabrication simulation, resulting in a 4 GHz shift in the frequency response. To measure the high frequency performance of the RFIC independent of the enclosure and transition, focused ion beam milling was used to isolate die from waveguide transition, and generate probing pads to directly measure the die output power. Furthermore, the effect of IR-drop, caused by the evaluation board circuits and connector, on the output power as well as the frequency response of the connector were measured. Finally, it is shown that by the full-wave analysis of the layout in HFSS, the resonating traces can be detected and modified to avoid power drop. At the end an algorithm is proposed for the diagnosis and fault detection of mm-wave system-in-packages.