The MEMs resonator technology employed by Analog Devices is developed in standard CMOS fabrication. This offers advantages in meeting targeted frequency responses based on the shape and sizes of device elements established at the photolithographic stage of development. Since MEMs is a silicon technology, the benefits of repeatability and sustainability apply in the manufacturing of MEMs wafers. The manufacturing temperatures reached in the processing of MEMs wafers can exceed 700ºC. The capability of the MEMs resonator to be subjected to multiple reflow temperatures of 260ºC without degradation in its performance can be attributed the characteristics of it material makeup, design, and wafer processing flow. In contrast, crystal assembly is a less robust process and prone to sizeable variations in product-to-product output. Frequency tuning and trimming generally requires the deposition or removal of material from the crystal electrode to achieve the desired frequency. Additionally, a vacuum must be established in the barrel for crystal to vibrate once voltage is applied to the device. For the quality of devices manufactured by Analog Devices, special materials are required for attachment of the crystal to its leads. These materials aid in the crystal being able to survive high temperature (~260ºC) reflow operations. However, care must be taken when subjecting crystals to multiple high temperature reflow cycles. Frequency shifts can be attributed to aging of “crystal-attach” material, quality of the vacuum, and imperfections in the crystal blank. In the final assembly and manufacturing flow of the RTC, four important drivers give the MEMs-based RTC advantage over their crystal counterparts. First, because MEMs is effectively an integrated circuit, when combined with the control-die/RTC, standard IC packaging technologies apply and can be used. With crystal assemblies custom manufacturing flows are required to attach and affix the crystal and die in the same package. Second, wire-bonding operations pertain and are used as the method of electrically connecting the control die to the MEMs resonator. Crystal assemblies either use more complicated and less robust solder attachment or welding of the crystal leads to connect the control die to the crystal resonator. Third, highly efficient wire-bonding operations and standard packaging assembly flows lend themselves well to high volume, less costly assembly, and manufacturing operations. Finally, the vast difference in size, between MEMs and crystals, offers lower-cost, smaller sized packaging options,  including chip-scale assemblies that are not possible with crystals. MEMs based RTC products have proven and demonstrable performance advantages based on environmental criteria and observation. In reflow operations (3x at 260ºC) that replicate customer attachment, MEMs devices demonstrate frequency shifts of less than ±1ppm. Crystal based products facing the same regimen of reflow temperature exposure demonstrate shifts as high as ±5ppm. MEMs based RTCs have been subjected to shock and vibration testing through AEC-Q100 qualification, and can sustain mechanical shock in excess of 2900g (x5) (JESD22-B104-C  Condition-H), and variable frequency vibration in excess of 20g (JESD22-B103B Condition-1). The newly introduced high temperature version of the DS3231MZA+ will allow operating temperatures to extend to 105ºC without degradation in frequency accuracy or stability than the ±5ppm specification. The end-user experience with a MEMs-based RTC will be captured in distinct ways. First, frequency accuracy over lifetime will be less than ±5ppm. Second, frequency accuracy over temperature and after reflow will still be less than ±5ppm.