Induction-based systems and methods for joining substrates

An example method of joining a first substrate with a second substrate includes applying a filler material between respective portions of the first substrate and the second substrate, the filler material including an electrically conducting and/or magnetic material, wherein the filler material and the respective portions define a joint; applying an alternating magnetic field to the joint to heat the electrically conducting material to a reaction temperature; in response to heating the electrically conducting material to the reaction temperature, energizing the joint using energy released from the electrically conducting material; cooling the joint to join the first substrate with the second substrate.

FIELD

The specification relates generally to systems for joining two substrates together, and more particularly to induction-based systems and methods for joining substrates together.

BACKGROUND

Welding is a fabrication process that joins materials together, including metals, plastics, and other materials. Welding involves using heat or pressure or both to melt parts of the materials and allowing the melted parts to fuse together upon cooling. The heat used in a welding process may be generated by a heat source such as a gas flame, an electric arc, a laser, an electron beam, or ultrasound. Welding often has high temperature requirements to melt the base materials and the heating method may therefore be inefficient.

SUMMARY

According to an aspect of the present specification, a method of joining a first substrate with a second substrate is provided. The method includes: applying a filler material between respective portions of the first substrate and the second substrate, the filler material including an electrically conducting and/or magnetic material, wherein the filler material and the respective portions define a joint; applying an alternating magnetic field to the joint to heat the electrically conducting material to a reaction temperature; in response to heating the electrically conducting material to the reaction temperature, energizing the joint using energy released from the electrically conducting material; cooling the joint to join the first substrate with the second substrate.

According to another aspect of the present specification, an induction-based apparatus to join substrates is provided. The apparatus includes: a housing; an inlet to receive a filler material including an electrically conducting material; an induction heating assembly housed in the housing configured to: receive the filler material from the inlet; and apply an alternating magnetic field to inductively energize the electrically conducting material of the filler material; and a nozzle to expel the energized filler material for joining the two substrates.

DETAILED DESCRIPTION

The present disclosure describes induction-based systems and methods for joining two substrates together. A filler material includes an electrically conducting and/or magnetic material and is applied between respective portions of a first and second substrate. Together, the respective portions and the filler material define a joint of the two substrates. The electrically conducting and/or magnetic material is heated to a reaction temperature via induction. In response to heating the electrically conducting and/or magnetic material to the reaction temperature, the joint is energized using energy released from the electrically conducting and/or magnetic material. Upon cooling, the two substrates are joined together. The filler material, and in particular, the electrically conducting and/or magnetic material may be specifically selected based on its heating properties (e.g., reaction temperature, energy release profile, and the like) to allow thermal control of the joining operation.

FIG.1depicts an example system100for joining two substrates according to the present disclosure. The system100includes an induction-based apparatus104(also referred to as simply the apparatus104) for joining a first substrate108-1with a second substrate108-2(referred to collectively as the substrates108and generically as a substrate108—this nomenclature may be used elsewhere herein). The substrates108can be plastics, metals, alloys, thermoplastics, composites, combinations of the above, and the like. In some examples, the substrates108may be dissimilar materials. For example, the first substrate108-1may include a metal material, while the second substrate108-2may include a plastic material.

The substrates108are to be joined together at a joint120defined by respective portions110-1and110-2. The portions110may be end portions, such as to form a corner joint, or the portions110may be overlapping portions respective surfaces of the substrates108. For example, in the present example, the portions110are substantially planar. In other examples, the portions110may be curved or otherwise non-planar and the portions110may conform to each other to form the joint120.

The substrates108are joined together using a filler material112. The filler material112includes an electrically conducting and/or magnetic material. In particular, the filler material112is applied between the respective portions110of the substrates108. Together, the portions110and the filler material112define the joint120. The joint120may be substantially planar, as in the present example, or the joint120may be otherwise shaped based on the portions110and their arrangement.

The filler material112includes an electrically conducting and/or magnetic material. For example, the filler material112can be a reactive metal compound such as a nano-thermite or a micro-thermite. In particular, the nano- or micro-thermite includes an oxidizer and a reducing agent (e.g., a metal and a metal oxide). The nano- or micro-thermites may be heated or energized via induction. Specifically, application of an alternating magnetic field induces eddy currents and/or hysteresis (as will be described in further detail below) in the nano- or micro-thermites, which in turn induces a reaction with core components, thereby releasing energy. More generally, the electrically conducting material can include various types of fluids (including liquids, gases, combinations, and the like) containing electrically conducting particles or components. The electrically conducting particles or components allow eddy currents and/or hysteresis to be introduced into the electrically conducting material to energize the electrically conducting material. For example, the electrically conducting material can include reactive metal compounds, compounds in gaseous state, in liquid state, in solid state, a slurry of materials involving multiple phases and states, synthetic and non-synthetic polymers, or the like. The electrically conducting material can further include a mixture of layers of materials, multi-coated metals with metamaterials, hybrid mixtures of reactive metal compounds in liquid and inert states, or other suitable combinations of materials. In some examples, the electrically conducting material may be a metallic or other suitable powder for a sintering operation, as will be described further below.

The apparatus104is generally configured to use induction-based techniques to join the substrates108together. The apparatus104therefore includes an induction heating assembly130. The induction heating assembly130is generally configured to heat the joint120via induction. Specifically, the assembly130includes a coil132coupled to a power supplying circuit134. The circuit134is configured to pass a current through the coil132for generating a magnetic field. The circuit134can be an electronic oscillator or other suitable circuitry for passing a high-frequency alternating current through the coil132. Thus, an alternating magnetic field is induced in the coil132. In some examples, the coil132may be oriented adjacent a joining region, for example, to allow large substrates108to be joined together. In other examples, the coil132may be configured to wrap around the joining region, such that the joining region is in the center of the coil to induce a stronger magnetic field in the joining region. In such examples, the size of the substrates108may be limited based on the size of the coil132.

In operation, the power supplying circuit134is configured to pass a current through the coil132, as indicated inFIG.1by arrows. In accordance with Ampere's Law, the current flowing through the coil132induces a magnetic field136around the coil132. In some implementations, the power supplying circuit134is further configured to vary the current passing through the coil132, thereby varying the magnetic field136. In other implementations, the coil132may be configured to move relative to a joining region118to vary the magnetic field136. For example, the coil132may be coupled to a positioning mechanism to move along a length of the joining region118, which is stationary.

The operation of the system100will now be described in conjunction withFIG.2.FIG.2depicts a flowchart of a method200of joining two substrates. The method200will be described in conjunction with its performance in the system100. In other examples, the method200may be performed by other suitable systems.

At block205, a filler material is applied between respective portions110of the first substrate108-1and the second substrate108-2. The filler material includes an electrically conducting material, such as a reactive metal compound (e.g. in liquid state or in gaseous state), a polymer, a thermoplastic, a multi-coated metal with metamaterials, or the like. In some examples, the filler material can include one or more further electrically conducting materials, such as a reactive metal compound (e.g. in liquid state or in gaseous state), a polymer, a thermoplastic, a multi-coated metal with metamaterials, or the like. The electrically conducting materials can include nanorods or nanowires (e.g. composed of gold, silver, copper, or the like), graphene or other suitable composites in addition to nano-thermites, metamaterials, and natural or synthetic polymers and thermoplastics.

More generally, the filler material112can include multiple electrically conducting and/or magnetic materials having different configurations (e.g. particle size, packing structure, such as simple cubic packing, face-centered cubic packing, hexagonal packing or the like), different structures (e.g. nanowires or rods, other particulate matter, liquids or the like), different reaction temperatures, different adhesion properties (e.g. better adhesion to different materials) or otherwise different energy release profiles.

The electrically conducting materials may be combined to form the filler material, for example in different layers, as a homogenous or heterogeneous mixture, or the like, according to the desired energy release profile. In particular, the variance in energy release profiles allows the apparatus104to precisely control the welding operation by controlling which materials are heated, and when they are heated.

The filler material300depicted inFIG.3Aincludes a medium302and nano-thermites304(i.e., the electrically conducting material) dispersed throughout the medium302. The medium302may be, for example, a metal, an alloy, a polymer, combinations of materials, or other suitable material for containing the nano-thermites304. In some examples, the medium302may be substantially fluid to allow the nano-thermites304to be freely dispersed throughout the medium302. In other examples, the medium302may be a gel or a solid to fix the positions of the nano-thermites304in the medium302.

The filler material310depicted inFIG.3Bincludes a medium312, first nano-thermites314and second nano-thermites316. Similarly to the filler material300, the first nano-thermites314and second nano-thermites316are dispersed throughout the medium312. The medium312may be a metal, a polymer, combinations of materials, or other suitable materials for containing the nano-thermites314and316. In some examples, the medium312may be fluid to allow the nano-thermites314and316to be freely dispersed throughout the medium312. In other examples, the medium312may be a gel or a solid to fix the positions of the nano-thermites314and316in the medium312. In the present example, the nano-thermites314and316are evenly distributed throughout the medium312.

In other examples, such as in the filler material320depicted inFIG.3C, first nano-thermites324and second nano-thermites326may be separated. Specifically, medium322may fix the first nano-thermites324at a first surface of the filler material320and the second nano-thermites326at a second surface of the filler material320. In such examples, the medium322may be a gel or a solid to allow separation of the nano-thermites324and326.

In still further examples, the filler material may not include a medium throughout which the electrically conducting material is dispersed. For example, the filler material330depicted inFIG.3Dincludes first nano-thermites334and second nano-thermites336intermixed with each other, but not contained by a medium. For example, the nano-thermites334and336may form a powder for sintering operations. In other examples, the filler material330may contain a single type of nano-thermite (e.g., only the first nano-thermites334or only the second nano-thermites336). The first nano-thermite and second nano-thermite may be heated to form an alloy.

Returning toFIG.2, at block205, the filler material may be selected according to the type of joining operation. For example, for a sintering operation, the filler material330may be utilized, while for a soldering operation, the filler material300may be utilized. To weld together two dissimilar materials, the filler material320may be utilized. The filler material may further be selected according to the energy release profile of the one or more electrically conducting materials contained therein. For example, to join two substrates which utilize relatively higher temperatures to join, the filler material310may be utilized to allow the first nano-thermites314to be heated with lower input energy, and to create a chain reaction to energize the second nano-thermites316to achieve the temperatures for joining the two substrates.

In some examples, at block205, a magnetic insulator may be applied at the joint to restrict the application of the filler material112to certain regions. For example, referring toFIG.4, a filler material412is applied between two substrates408-1and408-2and restricted by a magnetic insulator420.

Returning toFIG.2, at block210, the alternating magnetic field136is applied to the joint120to heat the electrically conducting and/or magnetic material to a reaction temperature. In particular, applying the alternating magnetic field136can include applying an alternating current to the coil132by the power supplying circuit134to induce a magnetic field.

In accordance with Faraday's Law of Induction, the varying magnetic field136induces eddy currents in nearby conductors, and in particular, in the electrically conducting material of the filler material. The induction of eddy currents in the electrically conducting material energizes the electrically conducting material and heats it to its reaction temperature. In some examples, the electrically conducting material may be energized via magnetic hysteresis. In particular, the magnetizing force against the internal friction of the molecules of the magnet produces heat energy. The energy lost due to heat is hysteresis loss. When magnetic force is applied, the molecules of the magnetic material of the filler material112are aligned in a first direction. When the magnetic force is reversed, the internal friction of the molecules of the magnetic material opposes the reversal of magnetism, resulting in magnetic hysteresis, and hence heating of the magnetic material. In some examples, at block210, the method200may employ both magnetic hysteresis and induction heating via eddy currents to energize the electrically conducting and/or magnetic material for the joining operation.

In examples where a magnetic insulator is applied, heating may be restricted to regions of the filler material which are not blocked by the insulator. Thus, application of the magnetic insulator may provide greater control over the joining operation and the regions which are joined together.

At block215, upon reaching its reaction temperature, the electrically conducting material releases energy according to its energy release profile and energize the joint. That is, in response to heating the electrically conducting material to the reaction temperature, the joint may be energized using energy released from the electrically conducting material. In particular, upon reaching its reaction temperature, the electrically conducting material may undergo an exothermic reaction and release energy to energize one or more of the filler material and the portions110.

For example, referring toFIG.5, a sintering operation500is depicted. In particular, energizing the joint may include energizing respective portions of the first and second substrates without liquefaction to sinter the first substrate with the second substrate. In the sintering operation500, a filler material512including an electrically conducting material is applied in between a first substrate508-1and a second substrate508-2. Specifically, the filler material512contacts a first surface510-1of the first substrate508-1and a second surface510-2of the second substrate508-2. When the electrically conducting material is heated to its reaction temperature, the filler material512, the first surface510-1and the second surface510-2are heated without melting to the point of liquefaction. The filler material512fuses with the first surface510-1and the second surface510-2, thus sintering the first substrate508-1with the second substrate508-2. For example, the filler material512may include a metallic powder, such as the filler material330to allow for a compact sintering operation500. In some examples, the sintering operation500may further include applying pressure to the joint, for example, as depicted by the arrows P inFIG.5, to support and assist the sintering of the first substrate508-1with the second substrate508-2.

In some implementations, the filler material can be energized for sintering processes by heat and/or pressure-less or pre-assisted techniques, Through the control of densification and/or grain growth, substrates can fuse and form a weld and/or mold to create different shapes and enhance material properties such as strength, electrical and thermal conductivity, and translucency or the like.

Referring now toFIG.6, a welding operation600is depicted. In particular, energizing the joint may include melting respective surfaces of the respective portions of the first and second substrates to weld the first substrate with the second substrate. In the welding operation600, a filler material612including an electrically conducting material is applied in between a first substrate608-1and a second substrate608-2. Specifically, the filler material612contacts a first surface610-1of the first substrate608-1and a second surface610-2of the second substrate608-2. When the electrically conducting material is heated to its reaction temperature, the first surface610-1and the second surface610-2are melted and may be welded together upon cooling. For example, the welding operation600may utilize the filler material300.

Referring now toFIG.7, a soldering operation700is depicted. In particular, energizing the joint may include energizing a soldering portion of the filler material to solder the first substrate with the second substrate. In the soldering operation700, a filler material712including an electrically conducting material is applied in between a first substrate708-1and a second substrate708-2. Specifically, the filler material712contacts a first surface710-1of the first substrate708-1and a second surface710-2of the second substrate708-2. When the electrically conducting material is heated to its reaction temperature, the filler material712, and in particular, a dispersion medium in which the electrically conducting material is dispersed may be melted to solder together the first substrate708-1and the second substrate708-2. That is, the filler material, and in particular, the dispersion medium may act to join the first and second substrates708.

In still further examples, energizing the joint may include heating a further electrically conductive material to a further reaction temperature. That is, the energy released upon the first electrically conducting material may initiate a chain reaction to heat additional electrically conductive materials to their respective reaction temperatures. For example, a first electrically conductive material may have a relatively lower reaction temperature, while a second electrically conductive material may have a relatively higher reaction temperature. The electrically conductive materials may be heated to the reaction temperature of the first electrically conductive material, which may undergo an exothermic reaction and thus release energy. The energy released may further energize the second electrically conductive material to allow it to reach its relatively higher reaction temperature. The second electrically conductive material may release additional energy. The additional energy may be used to continue a chain reaction of electrically conductive materials, or it may energize other components of the joint. That is, the additional energy released from the second material may be utilized in the sintering operation500, the welding operation600or the soldering operation700in addition to or instead of the energy released from the first electrically conducting material. Such chain reactions may be utilized, for example, to join substrates including materials which are to be joined at relatively high temperatures with lower input requirements.

In other examples, two different electrically conducting materials may be used to join two dissimilar substrates. For example, upon reaching the first reaction temperature of the first electrically conducting material, the first substrate may be bonded to the filler material, and upon reaching the second reaction temperature of the second electrically conducting material, the second substrate may be bonded to the filler material. That is, the joining of the first substrate with the second substrate may be a two-stage process, wherein one of the substrates is bonded to the filler material in the interim.

In still further examples, rather than using the energy from the first electrically conducting material to heat the second electrically conducting material, blocks210and215may be repeated to heat the second electrically conducting material to its reaction temperature. Specifically, the strength of the magnetic field136may be controlled (e.g., by controlling the current supplied to the coil132by the circuit134) to specifically heat the first electrically conducting material to the first reaction temperature and then changing the magnetic field136to heat the second electrically conducing material to the second reaction temperature.

In some examples, at blocks210and215, a secondary technique may be employed to further join the first substrate with the second substrate. The secondary technique may be performed simultaneously or sequentially with the blocks210and215. Example secondary techniques include, but are not limited to: solid-state bonding (e.g. anodic/wafer joining, diffusion bonding, ultrasonic wire bonding, cold bonding, explosive bonding, friction-stir bonding, friction welding, or the like), soldering/brazing (e.g. furnace, laser reflow, resistance, dip, wave, active brazing, flip chip bonding, or the like), fusion welding (e.g. laser beam, electron beam, percussive, plasma, gas tungsten, resistance, glass sealing, or the like), adhesive bonding (e.g. die attachment, flip chip bonding, sealing, or the like), and combinations of the above. Additionally, the method200may further include applying pressure to the joint simultaneously or sequentially with applying the alternating magnetic field to the joint at block210.

At block220, the joint is cooled to join the first substrate108-1with the second substrate108-2. Specifically, upon cooling of the joint, the first and second substrates108may be joined or bonded into a single final product.

Thus, the method200provides an induction-based technique for joining two substrates. The induction-based technique may be combined with other welding and/or bonding techniques to form a hybrid system. The induction-based technique may be used on earth (e.g. on land, air or water applications), in space (e.g. celestial bodies, the Moon, Mars, other planets, moons, asteroids, planetoids, and other celestial bodies or the like). In some examples, the induction-based technique may employ in-situ space resources, such as regolith on the Moon, Mars, materials on other planets, moons, asteroids, planetoids, and other celestial bodies, or the like to supplement the filler material. Further, the induction welding technique localizes energy generation and molten materials in space-limited situations for micro-joining applications.

For example, titanium powder (Ti) may be mixed with Boron (B) or Carbon (C) to form the filler material and pressed between Molybdenum (Mo) surfaces and ignited to form Mo—TiB2—Mo or Mo—TiC—Mo welds. In other examples, Aluminum (Al), Nickel (Ni), and Copper (Cu) mixtures may also be used as a filler material. Furthermore, combinations of metals and metal oxides may be used as filler material to join substrates, and the filler material may be composed of powdered, layered, laminated, and core-shell composites.

Referring now toFIG.8, an example induction-based apparatus800for joining substrates is depicted. The apparatus800includes a housing804to house an induction heating assembly830, a nozzle820and an inlet822. In other implementations, the coils in the induction heating assembly830may also be configured around the nozzle820.

The induction heating assembly830is housed in the housing804and includes a coil832coupled to a power supplying circuit834. The circuit is configured to pass a current through the coil832for generating a magnetic field. The circuit834can be an electronic oscillator or other suitable circuitry for passing a high-frequency alternating current through the coil832. Thus, an alternating magnetic field is induced in the coil832. The coil832is configured to wrap around a heating region818such that the heating region818is in the center of the coil832to induce a stronger magnetic field in the heating region818. The induction heating assembly830may be coupled to a trigger840to control the actuation of the induction heating assembly830. In operation, the power supplying circuit834is configured to pass a current through the coil832, as indicated by arrows. In accordance with Ampere's Law, the current flowing through the coil832induces a magnetic field136around the coil832. In some implementations the power supplying circuit834is further configured to vary the current passing through the coil832, thereby varying the magnetic field836. In other implementations, the coil832may be configured to move relative to a heating region818to vary the magnetic field836. For example, the coil832may be coupled to a positioning mechanism to move along a length of the heating region818, which is stationary. Specifically, application of an alternating magnetic field induces eddy currents and/or hysteresis (as will be described in further detail below) in the nano- or micro-thermites, which in turn induces a reaction with core components, thereby releasing energy.

The heating region818is coupled to the inlet822to receive materials therefrom, and to the nozzle820to expel heated materials from the apparatus800. Specifically, a filler material is fed through the inlet822, is heated by the induction heating assembly830in the heating region818. The filler material may include a dispersion medium and an electrically conducting material dispersed throughout the dispersion medium. The electrically conducting material can be a reactive metal compound such as a nano-thermite or a micro-thermite, and the dispersion medium may be a gel or solid to hold the filler material together to allow it to be fed into the apparatus800. Thus, the induction heating assembly830may energize the filler material from a solid or gel state to an energized fluid or plasma state to be expelled from the nozzle820. The energized fluid or plasma may be applied between two substrates to join the two substrates together.

The present disclosure provides systems and methods for joining two substrates using an induction-based technique, whereby a filler material including an electrically conducting material is energized via induction heating. The two substrates may be dissimilar materials. The induction welding technique can use a slurry of nano-energetic composites, metamaterials and polymers, or reactive metal compounds as the filler material. The properties of the filler material may be selected to control the energy release profile. Further, the use of induction ignition and/or heating allows for a consistent heating across the joint. The joint is therefore not limited to a linear weld or joint, and can be a substantially planar formation.