This disclosure relates to electrostatic discharge (ESD) mitigation devices that may be used, for example, in fluid handling systems, and more specifically, for use in ultra-pure fluid handling systems benefitting from electrostatic discharge mitigation.
Electrostatic discharge (ESD) is an important technical issue for fluid handling systems in the semiconductor industry and in other technology applications. Frictional contact between fluids and surfaces of various operational components (e.g. tubing or piping, valves, fittings, filters, etc.) in the fluid system can result in generation and buildup of static electrical charges. The extent of charge generation depends on various factors including, but not limited to, the nature of the components and the fluid, fluid velocity, fluid viscosity, electrical conductivity of the fluid, pathways to ground, turbulence and shear in liquids, presence of air in the fluid, and surface area. These properties, and ways to mitigate the undesired static electrical charge caused by these properties, are discussed, and reported in NFPA 77, “Recommended Practice on Static Electricity,” pp. 77-1 to 77-67, 2014.
Further, as the fluid flows through the system, the charge can be carried downstream in a phenomenon called a streaming charge, where charge may buildup beyond where the charge originated. Sufficient charge accumulations can cause ESD at the tubing or pipe walls, component surfaces, or even onto substrates or wafers at various process steps.
In some applications, semiconductor substrates or wafers are highly sensitive to static electrical charges and such ESD can result in damage or destruction of the substrate or wafer. For example, circuits on the substrate can be destroyed and photoactive compounds can be activated prior to regular exposure due to uncontrolled ESD. Additionally, built up static charge can discharge from within the fluid handling system to the exterior environment, potentially damaging components in the fluid handling system (e.g. tubing or piping, fittings, components, containers, filters, etc.), that may lead to leaks, spills of fluid in the system, and diminished performance of components. In these situations, such discharge, may lead to potential fire or explosion when flammable, toxic and/or corrosive fluids are used in the compromised fluid handling system.
Often the weak link in an electrical system is the integrity of the ground. In some fluid handling systems, to reduce the buildup of static charges, certain metal or conductive components in fluid handling system are grounded to mitigate the buildup of static charge in the system as it continually disperses from the metal or conductive components to ground. In some systems, a conductive cable tie or “zip-tie” composed of a conductive polymer is sometimes used for connecting components to ground. Such polymeric cable ties are prone to creep, movement, breakage, environmental effects or sensitivity, deterioration, wear, etc., and have many drawbacks in practice.
It would be desirable to improve ESD mitigation and grounding devices for use in ultra-pure fluid handling systems that gives improved component reliability, stability, performance, and reduction in potentially damaging ESD events.
One or more embodiments of this disclosure are related to electrostatic discharge (ESD) mitigation devices. In particular, embodiments are directed to an electrostatic discharge mitigation device comprising an electrically conductive insert to transfer static charge from electrically conductive polymer tubing to an electrically conductive polymer operative component to facilitate grounding of a fluid circuit.
Some embodiments of this disclosure comprise a tubing connector to connect two or more electrically conductive tubing segments in a fluid circuit, the tubing connector comprising an electrically conductive polymer connector body with two or more attachment portions, two or more attachment fittings, an electrically conductive polymer insert electrically contacting the electrically conductive connector body, and an electrically conductive bracket configured to attach and interface with the connector body to electrically connect the connector body to ground.
In various embodiments of the tubing connector, the tubing connector includes a straight connector, a T-connector, or an elbow connector. In certain embodiments of the tubing connector, the tubing connector is a straight connector having a fluid passageway to connect two tubing segments. In certain embodiments of the tubing connector, the tubing connector is an elbow connector having a fluid passageway to connect two tubing segments. In certain embodiments of the tubing connector, the tubing connector is a T-connector having fluid passageways to connect three tubing segments. In certain embodiments of the tubing connector, the connector body attachment portions include a threaded region and a nipple region to receive a tubing segment. In certain embodiments of the tubing connector, the attachment fittings include compression nuts to attach tubing segments to the threaded and nipple regions of the tubing connector.
In some embodiments of this disclosure comprise a fluid circuit for a predetermined fluid flow passageway having at least one inlet and at least one outlet, the fluid circuit including:
Another embodiment of this disclosure is an electrostatic discharge mitigation fluid pathway comprising an electrically conductive polymer insert to transfer static charge from electrically conductive polymer tubing to an electrically conductive polymer operative component.
Still another embodiment of this disclosure is an electrically conductive fluid circuit comprising electrically conductive polymer tubing, an electrically conductive polymer operative component, an electrically conductive polymer insert, and an electrically conductive bracket dissipating static charge to ground.
This disclosure further describes an embodiment of a method of making an electrostatic discharge mitigation fluid pathway having at least one inlet and at least one outlet including: a) connecting a plurality of electrically conductive polymer tubing segments to a plurality of operative components, each operative component comprising an electrically conductive polymer body portion with an internal fluid flow passageway and a plurality of tubing connector fittings and electrically conductive polymer inserts, the operative components connecting the plurality of electrically conductive tubing segments at selected tubing connector fittings, the plurality of tubing segments and operative components providing the fluid flow passageway through the fluid circuit; wherein each electrically conductive insert and electrically conductive body portion comprises an electrically conductive fluoropolymer, and wherein each of the tubing connector fittings electrically conductively connects the respective conductor of the body portion to the electrically conductive insert; and b) connecting the electrostatic discharge mitigation fluid circuit to ground.
The above summary is not intended to describe each illustrated embodiment or every implementation of the present disclosure.
The drawings included in this disclosure illustrate embodiments of the present disclosure and, along with the description, serve to explain the principles of the disclosure. The drawings are only illustrative of certain embodiments and do not limit the disclosure.
The embodiments of this disclosure are amenable to various modifications and alternative forms, and certain specifics have been shown, for example, in the drawings and will be described in detail. It is understood that the intention is not to limit the disclosure to the particular embodiments described; the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure.
The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The detailed description and the drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention. The illustrative embodiments depicted are intended only as exemplary. Selected features of any illustrative embodiment may be incorporated into an additional embodiment unless clearly stated to the contrary.
This disclosure reports embodiments of electrostatic discharge (ESD) mitigation devices for use with a fluid handling system having a fluid flow passageway from a fluid supply to one or more downstream process stages. Embodiments of this system include a fluid circuit including conductively connected operative components and ESD mitigation tubing segments. Conventional and some ESD mitigation fluid circuits are reported, for example, in International patent application, WO 2017/210293, which is incorporated herein by reference, except for express definitions or patent claims contained therein. Other ESD mitigation fluid circuits are reported, for example, in an Entegris brochure, FLUOROLINE Electrostatic (ESD) Tubing, 2015-2017. Other U.S. patent applications owned by Applicant, U.S. patent application Ser. No. 16/287,847 filed Feb. 27, 2019 and U.S. Provisional Patent Application No. 62/851,667,783, filed May 23, 2019, are both hereby incorporated by reference for all purposes.
Materials used to make the conductive inserts as described herein according the various embodiments are substantially inert to solvents, acid solutions, base solutions, or mixtures thereof. Such solvents include but are not limited to, cyclohexanone, isopropyl alcohol, propylene glycolmonomethyl ether, propylene glycol monomethyl ether acetate, n-butanol, octane, acetone, heptane, hexane, or mixtures thereof. A variety of materials may be used to make the conductive insert including both intrinsically conductive polymers, conductive-filled polymers, and metallic materials. Exemplary conductive-filled polymers include conductive-filled fluoropolymers including perfluoroalkoxy alkane (PFA) and polychlorotrifluoroethylene (PCTFE). The fluoropolymers can be filled with carbon fiber, nickel coated graphite, carbon powder, carbon nanotubes, graphene, or mixtures thereof. In some cases, the PFA can be filled with, metal particles or steel fiber in addition to or instead of a carbon material. In one embodiment, the electrically conductive insert 1 is fabricated from PFA filled with carbon fiber.
Suitable conductive metallic materials include, for example, stainless steel, titanium, nickel, or alloys thereof, or mixtures thereof. Exemplary commercially available metallic materials include, for example HASTELLOY®, INCONEL®, or MONEL®. HASTELLOY® is used to refer to various nickel-molybdenum alloys INCONEL® is used to refer to a family of austenitic nickel-chromium-based superalloys. MONEL® refers to a group of nickel alloys, primarily composed of nickel and copper, with small amounts of iron, manganese, carbon, and silicon.
Those skilled in the art would readily appreciate the variety of manufacturing process that are available to make the conductive insert including, but limited to, molding, casting, or machining processes.
Several types of connector fittings are contemplated herein, made from various polymers, are available and are known, such as PRIMELOCK® fittings, PILLAR® fittings, FLARETK® fittings, flared fittings, and other fittings. Exemplary fittings, for example, are illustrated in U.S. Pat. Nos. 5,154,453; 6,409,222; 6,412,832; 6,601,879; 6,758,104; and 6,776,440; which are hereby incorporated by reference.
The operative components may be constructed from conductive fluoropolymers including, for example, perfluoroalkoxy alkane (PFA), ethylene and tetrafluoroethylene polymer (ETFE), ethylene, tetrafluoroethylene and hexafluoropropylene polymer (EFEP), fluorinated ethylene propylene polymer (FEP), tetrafluoroethylene p[polymer PTFE), or other suitable polymeric materials. For example, in some embodiments the conductive fluoropolymers are PFA loaded with conductive material (e.g. loaded PFA). This loaded PFA includes, but is not limited to, PFA loaded with carbon fiber, nickel coated graphite, carbon fiber, carbon powder, carbon nanotubes, metal particles, and steel fiber. In various embodiments, conductive materials have a surface resistivity level less than about 1×108 ohms per square while non-conductive materials have a surface resistivity level greater than about 1×1010 ohms per square. In certain embodiments, conductive materials have a surface resistivity level less than about 1×109 ohms per square while non-conductive materials have a surface resistivity level greater than about 1×109 ohms per square. When the disclosed fluid handling systems are configured for use in ultra-pure fluid handling applications, both the tubing segments and operational components are typically constructed from polymeric materials to satisfy purity and corrosion resistance standards.
In various embodiments, tubing segments in this disclosure typically refer to any flexible or inflexible pipe or tube that is suitable for containing or transporting fluid. Tubing segments are conductive, providing a conductive pathway along the length of each tubing segment in the fluid circuit. Conductive tubing may be constructed from materials including metal or loaded polymeric material. Loaded polymeric material includes a polymer that is loaded with steel wire, aluminum flakes, nickel coated graphite, carbon fiber, carbon powder, carbon nanotubes, or other conductive material. In some instances, the tubing segments are partially conductive, having a main portion constructed from non-conductive or low conductive material, such as constructed from various hydrocarbon and non-hydrocarbon polymers such as, but are not limited to, polyesters, polycarbonates, polyamides, polyimides, polyurethanes, polyolefins, polystyrenes, polyesters, polycarbonates, polyketones, polyureas, polyvinyl resins, polyacrylates, polymethylacrylates and fluoropolymers. Exemplary fluoropolymers include, but are not limited to, perfluoroalkoxy alkane polymer (PFA), ethylene tetrafluoroethylene polymer (ETFE), ethylene, tetrafluoroethylene and hexafluoropropylene polymer (EFEP), fluorinated ethylene propylene polymer (FEP), and tetrafluoroethylene polymer (PTFE), or other suitable polymeric materials, and having, for example, a secondary co-extruded conductive portion. In certain embodiments the interior fluoropolymer conductive stripe of the tubing segments has a width in the range of about 0.1-1 centimeter. In selected embodiments each tubing segment has a length in a range of about 1-100 feet. In other selected embodiments, the tubing segment has an outside diameter of about ⅛ inch to about 2 inches. In other embodiments the tubing segments have a measured resistance of about 1.2×104-6.7×105 ohm. In still other embodiments the tubing segments have a measured resistance of about 2.5-4.3×104 ohm.
In certain embodiments the interior fluoropolymer conductive stripe of the tubing segments has a width in the range of about 0.15-0.80 centimeter. In selected embodiments each tubing segment has a length in a range of about 1-500 feet (0.3-152.4 meters). In other selected embodiments, the tubing segment has an outside diameter of about ⅛ inch to about 2 inches. In other embodiments the tubing segments have a measured surface resistance of between about 2.7×103-3.94×104 ohms per square. In accordance with this disclosure, the measured surface resistance is determined using the following method:
1) Sample Preparation: Measurements are carried out on test samples prepared by injection molding, compression molding or extrusion, or directly on the final manufactured product.
2) Conditioning Procedure: Before testing, the samples are conditioned at 23° C., 50% RH for 4 hours.
3) Surface Resistance Measurement: Two parallel electrodes of silver paint are applied onto the sample using an adhesive mask. Measurements are carried out at 23° C., 50% RH. The electrical resistance (Ohm) developed between the electrodes is measured.
4) The surface resistance is calculated, taking into account the geometry of the electrode, according the following equation:
Surface resistance=R*L/g;
Having thus described several illustrative embodiments of the present disclosure, those of skill in the art will readily appreciate that yet other embodiments may be made and used within the scope of the claims hereto attached. Numerous advantages of the disclosure covered by this document have been set forth in the foregoing description. It will be understood, however, that this disclosure is, in many respect, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of parts without exceeding the scope of the disclosure. The disclosure's scope is, of course, defined in the language in which the appended claims are expressed.
This application claims the benefit of and priority to U.S. Provisional Application No. 63/011,809 filed on Apr. 17, 2020, which is incorporated herein by reference in its entirety for all purposes.
Number | Date | Country | |
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63011809 | Apr 2020 | US |