MKS 653B-2-50-2 Non-Sealing Flapper Exhaust Throttle Valve for Etch and Deposition Systems

Product Overview

The MKS 653B-2-50-2​ is a high-speed exhaust throttle valve manufactured by MKS Instruments, purpose-built for precision downstream pressure control in vacuum process systems. As a core member of the MKS Type 653B series, the MKS 653B-2-50-2​ installs directly between the process chamber and the vacuum pump, serving as the critical actuation element in a closed-loop pressure control architecture. Its function is elegantly simple in concept yet demanding in execution: by varying the angular position of an internal flapper, it modulates the effective pumping speed seen by the chamber, holding the process pressure precisely on setpoint across a wide dynamic range. The “-2” suffix denotes the non-sealing flapper configuration without an O-ring, making this model particularly suited to applications where absolute shutoff is not required but rapid, repeatable throttling is essential.

What elevates the MKS 653B-2-50-2​ above conventional throttle valves is the integration of a high-speed motor and gear/driver assembly that delivers a full-stroke transit time of just 1.7 seconds, combined with a microstepping drive achieving 1/12,000 positioning resolution. This pairing of speed and precision means the valve can correct pressure disturbances in seconds rather than tens of seconds—a decisive advantage in processes where gas composition or flow changes abruptly between steps. The direct gear drive develops 800 in-oz of output torque, sufficient not only to position its own 48 mm flapper against process gas loads but also to operate contamination-prone valves up to 12 inches in non-sealing configurations, actively working to prevent the clogging and sticking that commonly plague throttle valves in reactive chemistries.

The MKS 653B-2-50-2​ is engineered for the harsh realities of semiconductor and thin-film manufacturing. All wetted surfaces are constructed from 316L stainless steel with Viton seals as standard, providing broad compatibility with aggressive process gases. The valve body can be heated to 150°C with optional sealing materials, a design choice that prevents reactive byproducts from condensing on the flapper—the single most common cause of erratic valve behavior in CVD and PVD applications. With an external leak rate of just 1×10⁻⁸ scc/sec He at the shaft seal, the MKS 653B-2-50-2​ safeguards process purity by minimizing atmospheric contamination ingress. A visible flapper position indicator simplifies troubleshooting by showing valve angle at a glance, while the 9-pin Type D connector and compatibility with MKS 651, 1651, and 652B (Rev B or newer) controllers make integration and autotuning straightforward.

Technical Specifications