Abstract: Embodiments generally relate to methods for bonding a cap to a substrate. In one embodiment, the method comprises first providing a ring-cap assembly, comprising a cap and an interposer ring comprising a ring material transparent at an illumination wavelength. A peripheral portion of the ring projects outwards beyond the overlying cap. The portion of the ring bottom surface underlying the projecting peripheral portion of the ring comprises a plurality of downwardly extending fingers. The method further comprises positioning the ring-cap assembly so that the plurality of fingers directly overlies predetermined portions of the substrate top substrate, creating a first bond between a first one of the plurality of fingers and a corresponding first predetermined portion of the substrate top surface, while illuminating and observing the first predetermined portion at the illumination wavelength through the projecting peripheral portion of the ring to determine a quality measure of that first bond.