Dxl USA Inc.

Dxl International, Inc.

Hamid Saghatchi

Charles F Drexel

Daniel Thomas Mudd

An assembly for measuring the mass flow and flow rate of gases such as are used in semiconductor fabrication processes. The assembly includes an axial flow passage, viz., a capillary tube with a bore of about 0.050 inch diameter and a wall thickness of about 0.002 inch, having a downstream end connected to a diffuser section having an axially symmetric, diverging passage. Gas exiting the diffuser section has a low pressure drop because the gas has expanded at a low, controlled rate, converting velocity head into pressure head, and because the tube and diffuser section passage are in-line, eliminating right-angle turns. The assembly also includes two resistance thermometers, coils of iron-nickel alloy wire about 0.0004 inch in diameter, providing a differential temperature measurement with a time constant of less than 4 seconds. When incorporated into a mass flow controller admitting arsine gas from a storage container into a vacuum chamber, the assembly can maintain a flow rate of 5 sccm when the residual gas pressure in the container is as low as 5 Torr. The assembly can also be incorporated into a mass flowmeter.

Mass flow measuring assembly having low pressure drop and fast response time

A split path mass flowmeter includes a housing having a longitudinally extending bore within which a flow splitter is positioned. The flow splitter includes a tapered portion having a taper corresponding generally to that of a tapered portion of the bore. The tapered portion of the flow splitter is nested within the tapered portion of the bore, the tapered portions of these elements thereby forming a self-holding retention section for non-adjustably retaining the flow splitter within the bore. The retention section may taper outwardly or inwardly in the direction of fluid flow. A calibration section may precede or follow the retention section or may be combined into the retention section. Further, a recovery section may be separately disposed downstream of the retention and calibration sections or may be combined along with the calibration function in the retention section.

Mass flowmeter having non-adjustable flow splitter

A flow meter has an elongate housing with a fluid inlet, a fluid outlet and an axial passage therebetween. The fluid passage contains a flow sensor assembly operationally connected in parallel to a flow splitter section. The flow sensor assembly has a flow tube forming an axial passage therethrough and the flow tube has a thermally diffusive sensor region. An upstream resistance thermometer and a downstream resistance thermometer are in thermal contact with the sensor region. The sensor region can additionally contain an electrically insulating coating on its outside surface and resistance thermometers formed by winding a single layer of a fine, uninsulated wire around its outside surface. The sensor assembly can be surrounded by inner and outer housings made of electrically and thermally conductive material connected to the flow tube near the ends of the sensor region and grounded to a printed circuit board.

Flow sensor

A disconnectable flow connector is formed of (a) a frusto-conical taper pin having a longitudinal bore through which the end portion of a flow tube of a mass flow sensor is inserted and secured and (b) a connector base containing a matched frusto-conical taper bore. The taper pin can be press-fit into the taper bore to form a fluid flow passage having a leakage level less than about 10.sup.-9 scc/sec helium.

Flow sensor connector

A disconnectable flow connector is formed of (a) a frusto-conical taper pin having a longitudinal bore through which the end portion of a flow tube of a mass flow sensor is inserted and secured and (b) a connector base containing a matched frusto-conical taper bore. The taper pin can be press-fit into the taper bore to form a fluid flow passage having a leakage level less than about 10.sup.-9 scc/sec helium. with a series of spaced apart, transverse grooves separated by lands in sealing engagement with the matched taper bore.

A hermetically sealed, precision fluid valve assembly including a ball valve element is disclosed. The assembly includes a valve element retainer comprising a thin, flexible member having a first portion operatively associated with the valve element and a second portion, extending from the first, secured to the body of the valve assembly. The valve element retainer guides the motion of the valve element and is designed to reduce friction and eliminate the generation and entrapment of contaminants, thereby minimizing hysteresis in the operation of the valve.

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Orange, CA, United States of America

Hamid Saghatchi