Using a magnetic field to increase the bonding area of ​​adhesive joints

Abstract

The invention is entitled "Use of a magnetic field to increase the joining area of ​​an adhesive joint". This patent application relates to an assembly technique for connecting components using a magnetic adhesive. A liquid adhesive comprising magnetic particles is provided, the liquid adhesive having sufficient properties to allow the adhesive to flow under the influence of a magnetic field before curing. The method for connecting components comprises the following steps: applying an adhesive to a substrate at a position corresponding to the joint; placing a magnetic element close to the joint to generate a magnetic field, the magnetic field interacting with the magnetic particles in the adhesive to cause the adhesive to flow in a direction corresponding to the magnetic field; and curing the magnetic adhesive under the influence of the magnetic field. An assembly fixture for connecting components comprises a magnetic element and an optional induction heating element. The assembly technique can be used to form a housing for an electronic device from two or more components.

Description

[0001] Related application citations

[0002] This application is a divisional application of the invention patent application with Chinese national application number 201910447396.7, application date May 27, 2019, and invention name “Using magnetic field to increase the bonding area of ​​adhesive joints”. Technical Field

[0003] The embodiments generally relate to magnetic adhesives. More specifically, embodiments of the present invention relate to magnetic particles dispersed within an adhesive and techniques related to using a magnetic field to affect the distribution of the adhesive during assembly of two or more components. Background Art

[0004] Various techniques are employed when assembling components to form a device. For example, mechanical fasteners, welding, mechanical interference, or adhesives may be used to assemble components. Extensive research has been conducted on various adhesives. Engineers expend significant effort selecting the appropriate adhesive to provide the optimal qualities for a specific application. For example, strength, color, viscosity, flexibility, cure time, and other properties may be considered when selecting the appropriate adhesive for a given application.

[0005] However, in some cases, applying adhesive during assembly can prove difficult. Assemblers may have difficulty applying adhesive evenly from one unit to the next in a particular joint. Low-viscosity adhesives may tend to run away from the intended joint, resulting in a poor bond. High-viscosity adhesives may be difficult to dispense. Improvements in techniques related to applying adhesives are desirable. Summary of the Invention

[0006] Various embodiments are described herein involving techniques for influencing the flow of liquid substances using magnetic fields. Magnetic particles are dispersed in a liquid having properties such that the motion applied to the magnetic particles causes the liquid to flow along with the magnetic particles. The specific properties of the liquid can depend on a variety of factors, including particle size and shape and the viscosity of the liquid. The magnetic properties of the liquid substance can then be exploited during the assembly of various products utilizing these substances.

[0007] A method for applying an adhesive to a joint formed between a substrate and a component is disclosed. The method includes the following steps: applying an adhesive including magnetic particles dispersed therein to a location on the substrate corresponding to the joint; placing a fixture including a magnetic element near the joint to generate a magnetic field that interacts with the magnetic particles in the adhesive to cause the adhesive to flow in a direction corresponding to the magnetic field; and curing the adhesive under the influence of the magnetic field.

[0008] In some embodiments, once the adhesive reaches the gel point, the clamp can be removed. In other embodiments, the clamp can be removed after a period of time sufficient to allow the adhesive to transition from a liquid state to a solid state.

[0009] In some embodiments, the strength of the magnetic field generated by the magnetic element is adjusted to select the desired shape of the adhesive at the joint. For example, the strength of the magnetic field can be adjusted to change the shape (e.g., radius) of the fillet formed by the adhesive at the joint on one or both sides of the component.

[0010] In some embodiments, the magnetic element is a permanent magnet. In other embodiments, the magnetic element is an electromagnet.

[0011] In some embodiments, the fixture includes an induction heating element. In such embodiments, curing the adhesive can include heating the magnetic particles in the adhesive using the induction heating element.

[0012] In some embodiments, the substrate and the component are ferromagnetic. In other embodiments, the substrate is non-ferromagnetic and the component is ferromagnetic. In other embodiments, neither the substrate nor the component is ferromagnetic.

[0013] Adhesive bonding can be used to connect at least two components to form a housing for an electronic device. The housing may include a first component and a second component, the second component being bonded to the first component via a magnetic adhesive to form a joint between the first and second components. The shape of the magnetic adhesive cured at the joint is based on a magnetic field applied to the joint during assembly as the magnetic adhesive cures.

[0014] An assembly jig is described for bonding two components to form a housing for an electronic device. The assembly jig includes a magnetic element configured to be placed proximate a joint between a first component and a second component. The magnetic element generates a magnetic field at a location corresponding to the joint. The joint includes a magnetic substance in a liquid state, such that the magnetic substance flows relative to at least one of the first component or the second component under the influence of an attractive force exerted by the magnetic element on the magnetic substance.

[0015] In some embodiments, the magnetic element is a permanent magnet. In other embodiments, the magnetic element is an electromagnet comprising a coil of wire wrapped around a ferromagnetic core. In some embodiments, the assembly fixture further comprises an induction heating element that is activated under the influence of a magnetic field to solidify the magnetic substance.

[0016] Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the described embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present disclosure will be more readily understood through the following detailed description in conjunction with the accompanying drawings, in which like reference numerals represent like structural elements.

[0018] Figure 1 Adhesives according to some embodiments are shown.

[0019] Figures 2A to 2D An assembly process for adhesively bonding a component to a substrate is shown, according to some embodiments.

[0020] Figures 3A to 3B Techniques for adjusting the shape of an adhesive around a joint are shown, according to some embodiments.

[0021] Figure 4 Techniques for forming bonded joints according to some embodiments are shown.

[0022] Figure 5 Techniques for curing magnetic adhesives according to some embodiments are shown.

[0023] Figures 6A to 6B A multi-layer adhesive joint is shown according to some embodiments.

[0024] 7A to 7B An application for moving a magnetic adhesive into a joint is shown according to some embodiments.

[0025] Figure 8 A portable electronic device according to some embodiments is shown.

[0026] Figures 9A to 9B A laptop computer utilizing a fastener-less securing mechanism is shown in accordance with some embodiments.

[0027] Figure 10 is a flow chart of a method for forming an adhesive bond at a joint between components of a housing for an electronic device, according to some embodiments.

[0028] Figure 11 is a flow chart of a method for influencing magnetic matter using a magnetic field, according to some embodiments. DETAILED DESCRIPTION

[0029] This section describes representative applications of the methods and apparatus according to the present application. These examples are provided solely to add context and aid in understanding the described embodiments. Therefore, it will be apparent to those skilled in the art that the embodiments may be practiced without some or all of these specific details. In other cases, well-known processing steps have not been described in detail to avoid unnecessarily obscuring the embodiments. Other applications are possible, such that the following examples should not be considered limiting.

[0030] In the following detailed description, reference is made to the accompanying drawings which form a part of the specification and in which are shown by way of illustration specific embodiments in accordance with the described embodiments. Although these embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, it is to be understood that these examples are not limiting; other embodiments may be used and modifications may be made without departing from the spirit and scope of the described embodiments.

[0031] A liquid adhesive is disclosed that includes ferromagnetic particles dispersed therein. The size and geometry of the ferromagnetic particles are carefully selected and matched to a given adhesive so that the adhesive flows toward a magnetic field source under the influence of a magnetic field. In some embodiments, a magnetic field is provided to pull the adhesive onto the side of a component bonded to a substrate. Under the influence of the magnetic field and gravity, the adhesive forms natural rounded corners that provide a strongly bonded joint after the adhesive cures. The shape of the cured adhesive formed using the magnetic field is not naturally achievable using conventional adhesives or application techniques.

[0032] Other applications that may benefit from magnetic adhesives such as those described herein are joining hard-to-reach joints or filling gaps between components to form a seal near an opening in the housing of an electronic device, such as by using a magnetic adhesive to form a cosmetic seal or seam. Another application is the use of magnetic adhesives for staking large components (such as capacitors) to a printed circuit board (PCB). Another application is the use of magnetic adhesives for potting (e.g., waterproofing electronic components). Some magnetic adhesives may include a significant percentage of conductive particles, making the adhesive conductive. Such adhesives can then be used in electromagnetic interference (EMI) shielding applications or for connecting electronic components to contacts on a PCB.

[0033] References below Figures 1 to 9B These and other embodiments will be discussed in detail; however, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for illustrative purposes only and is not to be construed as limiting.

[0034] Figure 1An adhesive 100 according to some embodiments is shown. The adhesive 100 includes a liquid adhesive 110 in an uncured state. In various embodiments, the liquid adhesive 110 may be, but is not limited to, one of the following types of adhesives: epoxy resins (single-component and multi-component), cyanoacrylates, polyurethanes, or acrylic adhesives. The liquid adhesive 110 has various properties, including viscosity, cohesive strength, elastic modulus, and curing conditions (e.g., thermosetting properties, hardener requirements, curing time, etc.). In some embodiments, the liquid adhesive 110 may be referred to as a non-magnetic liquid polymer. The adhesive properties can be adjusted to achieve the desired properties for a given application. For example, a low viscosity adhesive can be used in one application, and a high viscosity adhesive can be used in another application.

[0035] The adhesive 100 also includes magnetic particles 120 dispersed within the liquid adhesive 110. In some embodiments, the magnetic particles 120 are ferromagnetic particles, such as 410 series stainless steel particles. It should be understood that the magnetic particles 120 can be made of any ferromagnetic material such as steel, ferrite, neodymium alloy (e.g., NdFeB) or other rare earth alloys that exhibit magnetic qualities, as well as other ferrous metals or their alloys. In other embodiments, the magnetic particles 120 can be made of any paramagnetic or diamagnetic material rather than a ferromagnetic material. In the case of a paramagnetic material, its magnetic force will be weaker than that of a ferromagnetic material. In the case of a diamagnetic material, its magnetic force will repel the magnetic particles 120 rather than attract them. Although the remainder of this specification may refer exclusively to ferromagnetic materials, other embodiments may alternatively implement the magnetic particles 120 as a paramagnetic or diamagnetic material.

[0036] In some embodiments, the shape of the magnetic particles 120 is irregular. For example, the first dimension (e.g., length) of the magnetic particles 120 can be many times larger than the second dimension (e.g., width). For example, the length of the magnetic particles 120 can be greater than 100 microns and the thickness can be less than 25 microns. These irregularly shaped particles can be referred to as metal flakes. The shape of the metal flakes can be advantageous for moving together with the liquid adhesive 110 under the influence of a magnetic field. More specifically, the metal flakes have a large surface area for cohesively bonding with the polymer in the liquid adhesive 110, making it difficult for the metal flakes to move through the fluid, and the large cross-section of the flakes in at least one direction is beneficial for applying momentum to the liquid adhesive 110.

[0037] In some embodiments, the shape of magnetic particles 120 is substantially spherical. In other embodiments, magnetic particles 120 may include a non-magnetic core coated with a ferromagnetic material, such as glass or ceramic. In some embodiments, magnetic particles 120 may have a hollow core, such as a hollow glass bead coated with a ferromagnetic material.

[0038] In some embodiments, the size of the magnetic particles 120 is substantially uniform. For example, the diameter of the magnetic particles 120 may be 50 microns and the tolerance may be ± 5 microns. In other embodiments, the size of the magnetic particles 120 is non-uniform. For example, some magnetic particles 120 have a major diameter of 250 microns, and other magnetic particles 120 have a minor diameter of 100 microns—less than half the major diameter. In some embodiments, the ferromagnetic particles are doped with additional non-ferromagnetic particles of a different material (such as aluminum or copper) interspersed. The non-ferromagnetic particles can help improve the electrical conductivity of the adhesive, while the ferromagnetic particles help promote the flow of the adhesive under the influence of the magnetic field.

[0039] The adhesive 100 comprising a liquid adhesive 110 and magnetic particles 120 may be referred to as a magnetic adhesive 100 in this article. It should be understood that the magnetic particles 120 can act under the influence of a magnetic field. The magnetic particles 120 will align with the magnetic field and be subject to an attractive force based on the magnetic field. This attractive force will result in movement in the magnetic particles 120, which will cause the adhesive 100 to flow according to the magnetic field and any other force acting on the liquid adhesive 110 (e.g., gravity, capillary force, pressure difference, etc.). The effectiveness of the flow rate will depend on properties such as the viscosity of the liquid adhesive 110, the cohesive strength (e.g., the degree of engagement between the liquid adhesive 110 and the magnetic particles 120), the size of the magnetic particles 120, and the concentration of the magnetic particles 120 in the liquid adhesive 110, and the intensity and shape of the applied magnetic field. These properties can be adjusted so that the adhesive can flow predictably in response to the applied magnetic field, and the flow and resulting shape of the cured adhesive 100 can increase the bonding strength and / or structural strength of certain adhesive joints.

[0040] In some exemplary embodiments, the size of the magnetic particles 120 is less than 150 microns in diameter and the viscosity of the liquid adhesive is between 10,000 and 30,000 centipoise (cP). It should be understood that exemplary sizes and shapes of the particles and / or the viscosity of the liquid can be determined by applying Stokes' law. The aforementioned properties are provided as exemplary properties for some applications only, and magnetic adhesives outside of these limiting properties are contemplated to be within the scope of the present disclosure. The concentration of magnetic particles 120 in the magnetic adhesive 100 may be less than 20% by weight. In other exemplary embodiments, the concentration of magnetic particles 120 may be sufficient to make the adhesive 100 conductive. For example, a concentration of 80% by weight or more by weight may be sufficient to make the adhesive 100 conductive while still maintaining sufficient adhesive bonding strength.

[0041] In some embodiments, the size of the magnetic particles 120 is selected to be larger than the minimum bond length associated with the liquid adhesive 110. More specifically, the adhesive may require a minimum spacing between the two surfaces being bonded in order for the polymer to form an adhesive bond. The diameter of the magnetic particles 120 can be selected to be larger than the minimum bond length to ensure that the spacing between the two surfaces bonded by the liquid adhesive 110 is larger than the diameter of the magnetic particles 120.

[0042] In some embodiments, the techniques described herein can be practiced with any liquid having properties that promote the flow of the liquid in response to the movement of magnetic particles 120. For example, the techniques described herein can be practiced with silicone (e.g., polysiloxane) having magnetic particles 120 dispersed therein. Any liquid that will move with the magnetic particles 120 and can be caused to transform into a semi-solid or solid state can be utilized in the manner described below.

[0043] Figures 2A to 2D 2 shows an assembly process 200 for adhesively bonding a component to a substrate according to some embodiments. In a first step 200-1 of the process 200, as shown in FIG. Figure 2A As shown, a substrate 210 and a component 220 are provided to form an adhesive bond at a joint 230 between the substrate 210 and the component 220. In some embodiments, the joint 230 is a T-joint, but in other embodiments, the joint 230 can be a butt joint, a lap joint, or any other type of technically feasible joint.

[0044] The substrate 210 and the component 220 adhesively connected to the substrate 210 can be similar materials or different materials. In some embodiments, one or both of the substrate 210 and the component 220 can be a ferromagnetic material such as steel. In other embodiments, neither the substrate 210 nor the component 220 is ferromagnetic. Examples of non-ferromagnetic materials include metals (e.g., aluminum alloys, 300 series stainless steel, copper, etc.), plastics (e.g., PE, PTFE, etc.), ceramics (e.g., glass, enamel, etc.), or composite materials such as carbon or glass fibers encapsulated in resin, plastic-coated metal, metal with embedded plastic or glass, etc.

[0045] In the second step 200-2 of the process 200, as Figure 2B As shown, magnetic adhesive 100 is dispensed near joint 230. Although magnetic adhesive 100 includes magnetic particles 120 dispersed therein, during this step in the process, magnetic particles 120 are not magnetized. Therefore, magnetic particles 120 (and therefore adhesive 100) are not attracted to substrate 210 or component 220.

[0046] The liquid adhesive 110 in the magnetic adhesive 100 will flow due to natural forces such as gravity, capillary forces, and pressure differentials to spread onto the substrate 210 in and / or around the joint 230. It should be understood that the adhesive 100 can be dispensed manually or automatically. For example, an assembly technician can manually apply the magnetic adhesive 100 to the substrate 210 by brush, or an assembly technician can manually dispense the magnetic adhesive 100 onto the substrate 210 via a syringe. Alternatively, a robot can automatically dispense the magnetic adhesive 100 via a nozzle, screen printing process, etc.

[0047] In the third step 200-3 of the process 200, as Figure 2C As shown, magnet 240 is placed near joint 230. The magnetic field 250 generated by magnet 240 causes magnetic particles 120 in magnetic adhesive 100 to align with the magnetic field. Magnetic particles 120 and magnet 240 experience an attractive force that acts to influence the shape of magnetic adhesive 100 in and around joint 230. For example, Figure 2C As shown, the magnetic adhesive 100 creeps along the sides of the component 220 on either side of the joint 230 to form fillets (eg, rounded transitions) of the magnetic adhesive 100 on either side of the joint 230 .

[0048] In such Figure 2C In the example shown, component 220 is ferromagnetic, while substrate 210 is non-ferromagnetic. Thus, ferromagnetic component 220 influences the shape of magnetic field 250 and the shape of magnetic adhesive 100 at joint 230. In other examples, component 220 and substrate 210 are non-ferromagnetic, and thus, the shape and / or strength of magnetic field 250 near joint 230 are different, thereby influencing a different shape of magnetic adhesive 100 at joint 230. In other embodiments, both substrate 210 and component 220 are ferromagnetic, which further influences the shape and / or strength of magnetic field 250 near joint 230.

[0049] In some embodiments, magnet 240 is replaced with a fixture comprising a magnetic element capable of generating a magnetic field near joint 230. For example, the fixture may comprise a conductive coil wound around a ferromagnetic core to form an electromagnet. Current may be applied to the coil to generate a magnetic field similar to Figure 2C The magnetic field of the permanent magnet 240 can be controlled to vary the strength of the magnetic field and, therefore, the shape and / or strength of the magnetic adhesive 100 at the joint 230. Alternatively, the fixture can include the magnet 240 and one or more other components such as a fixture, a locating pin, and / or an induction heating element, as described more fully below.

[0050] In the fourth step 200-4 of the process 200, as Figure 2DAs shown, the magnetic adhesive 100 is allowed to cure. The magnet 240 remains proximate to the joint 230 while the magnetic adhesive 100 cures, thereby maintaining the shape of the magnetic adhesive 100 at the joint 230 until the magnetic adhesive 100 has cured sufficiently to maintain its shape when the magnet 240 is removed. In some embodiments, the magnet 240 remains proximate to the joint 230 until the magnetic adhesive 100 reaches the gel point of the liquid polymer in the liquid adhesive 110, which is sufficient to maintain the shape of the magnetic adhesive 100 without the influence of the magnetic field. In other words, the magnet 240 is held in place proximate to the joint 230 until the liquid adhesive 110 undergoes a state transition from a liquid to a gel or solid, which is characterized by a significant change in the viscosity of the liquid adhesive 110. In some embodiments, curing the liquid adhesive 110 may include waiting a specified time for the liquid adhesive 110 to solidify (e.g., for a chemical reaction between the two components of the adhesive to occur to harden the adhesive). In other embodiments, curing the liquid adhesive 110 may include heating the liquid adhesive 110 or subjecting the liquid adhesive 110 to ultraviolet (UV) light to cure the liquid adhesive 110 .

[0051] It should be understood that the steps of process 200 can be performed in a different order. For example, magnetic adhesive 100 can be applied to substrate 210 before component 220 is introduced to substrate 210. As another example, magnet 240 can be placed near joint 230 before magnetic adhesive 100 is dispensed at joint 230. For example, magnet 240 can be placed near substrate 210 before magnetic adhesive 100 is dispensed onto substrate 210. The magnetic field can cause magnetic adhesive 100 to move before component 220 is introduced to substrate 210, which can be beneficial in guiding magnetic adhesive 100 to the correct position before forming joint 230 between substrate 210 and component 220. This technique can be particularly useful for drawing adhesive into areas that are traditionally difficult to reach with dispensing mechanisms.

[0052] Figures 3A to 3B Techniques for adjusting the shape of the magnetic adhesive around the joint 230 are shown according to some embodiments. Figure 3A As shown, a first adhesive 310 comprising a liquid adhesive and magnetic particles is dispensed at the joint 230 and subjected to a magnetic field from the magnet 240. The first adhesive 310 spreads from the side of the component 220 to a height h1 312. In contrast, as Figure 3B As shown, second adhesive 320 comprising a liquid adhesive and magnetic particles is dispensed at joint 230 and subjected to a magnetic field from magnet 240. Second adhesive 320 spreads from the sides of component 220 to a height h2 322 that is greater than height h1 312.

[0053] It should be understood that the shape of the cured adhesive around joint 230 can be customized by varying the properties of the liquid adhesive. For example, first adhesive 310 can be more viscous than second adhesive 320. The increased viscosity can inhibit the movement of the adhesive under the influence of a particular magnetic field. Other properties that can affect the shape of the adhesive at joint 230 include: adjusting the concentration of magnetic particles in the adhesive; changing the material of the magnetic particles; adjusting the formulation of the adhesive (e.g., different polymers or adhesive types can exhibit different cohesive strengths, viscosities, etc.); and so on.

[0054] In addition to changing the properties of the adhesive, the shape of the adhesive in joint 230 can also be affected by changing the magnetic field near joint 230. For example, where first adhesive 310 and second adhesive 320 are structurally identical adhesives, the shape of the adhesive at the joint can be changed by changing the strength of magnet 240. A weaker magnetic field applied to first adhesive 310 can result in spreading to a first height h1 312, while a stronger magnetic field applied to second adhesive 320 (the same as first adhesive 310) can result in spreading to a second height h2 322.

[0055] It should also be understood that the shape can be varied by changing the concentration of ferromagnetic material in component 220 and / or substrate 210, as this will affect the shape of the resulting magnetic field near joint 230. In other words, any ferromagnetic material placed near joint 230 will affect the magnetic flux around joint 230 and, therefore, the strength and / or orientation of the magnetic field experienced by the magnetic particles in the liquid adhesive.

[0056] Figure 4 2 shows a technique for forming a bonded joint according to some embodiments. It should be understood that multiple bonded joints can be formed substantially simultaneously. For example, two T-junctions can be formed substantially simultaneously by arranging multiple ferromagnetic components 220 to form the equivalent of a horseshoe magnet. Figure 4 As shown, magnet 440 is placed close to component 220, but the polarity of the magnetic dipole of magnet 440 is arranged parallel to the surface of substrate 210. This causes ferromagnetic component 220 to form a magnetic circuit similar to a horseshoe magnet, resulting in a magnetic field 450 that is directed between the two ends of ferromagnetic component 220 near the two T-junctions (junction 410 and junction 420).

[0057] In some embodiments, magnetic adhesive 100 is dispensed on the substrate beneath first joint 410 and second joint 420 before magnet 440 is placed proximate the joints. Magnet 440 then causes the adhesive to spread along component 220 at each joint, as shown in FIG. Figure 4In other embodiments, the magnetic adhesive 100 is dispensed near one joint and allowed to flow to the other joint before applying the magnetic field. Figure 4 , but a second magnet can be placed on the opposite side of substrate 210 relative to magnet 240 near first joint 410 and / or second joint 420 to help flow adhesive 100 from one joint to the other. The second magnet can then be removed, and primary magnet 240 can be placed near the joint to promote movement of adhesive toward the component to increase the strength of the joint.

[0058] It should be understood that the use of a low viscosity adhesive and subsequent application of a magnetic field can achieve bonding of joints that are difficult to reach using conventional techniques. For example, during assembly, it may be possible to reach joint 410 to dispense magnetic adhesive 100, but it may not be possible to reach joint 420 (for example, due to being located in an internal area of ​​the assembly). Conventional means for forming an adhesive bond at joint 420 may include applying the adhesive before bringing component 220 close to substrate 210. However, this technique typically causes the adhesive to flow outward away from the joint before the joint is formed, thereby weakening the adhesive bond between component 220 and substrate 210. The technique of using a magnetic low viscosity adhesive makes it possible to dispense the adhesive at one location (such as joint 410) and then move the adhesive to a second location before the adhesive is affected by the magnetic field to its final position for the bonded joint. Compared to conventional techniques, this technique wastes less adhesive and / or obtains a stronger adhesive bond.

[0059] Figure 5 Techniques for curing a magnetic adhesive according to some embodiments are shown. It should be understood that magnetic adhesive 100 includes a liquid adhesive 110 and magnetic particles 120. Furthermore, some types of adhesives cure at elevated temperatures; such adhesives may be referred to as thermosetting adhesives. However, care may be required when curing these adhesives to avoid damaging substrate 210 and / or component 220.

[0060] In some embodiments, substrate 210 and component 220 are formed from a material such as plastic. Applying heat to the assembly to cure adhesive 100 may cause deformation or discoloration of substrate 210 and / or component 220. Therefore, it is desirable to be able to heat the adhesive without heating surrounding objects. Due to the properties of magnetic particles 120 in magnetic adhesive 100, induction heating technology can be used to heat magnetic particles 120, thereby providing heat to liquid adhesive 110, which causes liquid adhesive 110 to cure (e.g., solidify) without heating substrate 210 and component 220.

[0061] like Figure 5As shown, an induction heating element 510 can be included in the fixture 500 along with the magnet 240. The induction heating element 510 can include a conductive coil capable of transmitting a high current through the coil to generate a fluctuating magnetic field outside the coil. Once the magnetic adhesive 100 is formed under the influence of the magnetic field from the magnet 240, the induction heating element 510 can be activated to heat the magnetic particles 120 in the magnetic adhesive 100, thereby curing the liquid adhesive 110. It should be understood that when the substrate 210 and the component 220 are made of materials that are incompatible with induction heating (e.g., plastics, certain metals, etc.), the induction heating element 510 does not generate heat in the substrate 210 or the component 220.

[0062] Although the heat generated in the magnetic particles 120 is conducted to the substrate 210 and / or component 220 through the liquid adhesive 110, the thermal conductivity of the liquid adhesive 110 may be much lower than the thermal conductivity of the substrate 210 and / or component 220. Therefore, the heat is dissipated in the substrate 210 and / or component 220 at a faster rate than the heat is transferred from the liquid adhesive 110 to the surrounding objects, which prevents the substrate 210 and / or component 220 from experiencing a temperature increase to the point where the substrate 210 and / or component 220 may be damaged.

[0063] In some embodiments, the induction heating element 510 can be utilized independently of the magnet 240. In other words, techniques for utilizing the induction heating element 510 to cure an adhesive including particles dispersed therein that are compatible with generating heat in response to a fluctuating magnetic field can be implemented separately from utilizing a magnetic field to promote movement or flow of the adhesive to affect the shape of the cured adhesive.

[0064] In other embodiments, the clamp 500 can be used during a disassembly process following the assembly process described above. After the adhesive 100 has cured, an induction heating element can be used to heat the magnetic particles 120, thereby breaking the adhesive bonds in the cured adhesive and allowing the joint to be disassembled.

[0065] Figures 6A to 6B A multi-layer adhesive joint according to some embodiments is shown. In some embodiments, two or more adhesives can be used to form an adhesive bond in the joint. It should be understood that a low-viscosity adhesive is more conducive to filling the joint tightly and forming a bond between the substrate 210 and the component 220. However, a low-viscosity adhesive may not form the correct shape of the adhesive bond around the joint and / or the adhesive bond may interfere with the fit of other components near the joint. Therefore, two or more different adhesives can be used to form a multi-layer adhesive bond at the joint.

[0066] For example, Figure 6AAs shown, a first adhesive 610 having a low viscosity may be applied at the joint. A magnet may be placed proximate to the joint and the first adhesive 610 allowed to cure, thereby forming an adhesive bond at the joint of the first shape. Figure 6B As shown, a second adhesive 620 having a higher viscosity can be applied to the joint. A magnet can be placed near the joint, and the second adhesive 620 can be allowed to cure, thereby forming an adhesive bond at the joint of a second shape that overlays the first shape of the first adhesive 610. It should be understood that different magnets 240 can be used for the first step of forming the adhesive bond with the first adhesive 610 and the second step of forming the adhesive bond with the second adhesive 620, thereby forming different shapes based on two different magnetic fields. Alternatively, an electromagnet can be placed near the joint, and different magnetic field strengths can be induced in the electromagnet by applying different currents to the electromagnet to form the desired shapes of the first adhesive 610 and the second adhesive 620.

[0067] It should be understood that the first adhesive 610 can be used to promote a better adhesive bond between the components, while the second adhesive 620 can be used to provide a final shape to the joint, which provides additional structural strength due to the physical shape of the joint. In some cases where the properties of the adhesive necessary to form the final desired shape of the joint are not conducive to forming a strong adhesive bond between the component and the substrate, utilizing the second adhesive 620 to form the final shape of the joint without using the first adhesive 610 may be problematic.

[0068] 7A to 7B 1 shows an application for moving magnetic adhesive 100 into a joint according to some embodiments. It should be understood that the magnetic field is used not only to form a shaped adhesive bond at the joint (such as by forming fillets on one or both sides of a T-joint), but also to achieve other beneficial results. For example, Figure 7AAs shown, a conventional lap joint is formed between the housing 710 and the display assembly 720 of an electronic device. The housing 710 includes a flange 712 formed near an opening in the housing. The display assembly 720 is designed to be bonded to the flange in an adhesive manner. The adhesive can form a liquid barrier that makes the electronic device waterproof. Conventional techniques for forming an adhesive bond between the housing 710 and the display assembly 720 include dispensing an adhesive 730 on the flange 712 and then pressing the display assembly 720 into the opening to compress the adhesive 730 between the flange 712 and the display assembly 720. However, these techniques are not ideal because the adhesive flow is determined by the pressure differential caused by moving the display assembly 720 into the opening of the housing, and therefore the adhesive flow can be unpredictable. For example, the adhesive may flow out into the internal volume of the electronic device, rather than flowing upward around the display assembly to fill the gap between the display assembly 720 and the edge of the housing 710.

[0069] like Figure 7B As shown, magnetic adhesive 730 can be influenced by a magnetic field to flow upward around display assembly 720 and into the gap between display assembly 720 and housing 710. Rather than pressing display assembly 720 into an opening to cause the adhesive to flow based on a pressure differential, magnet 240 can be placed proximate to the gap between display assembly 720 and housing 710 while more gently moving display assembly 720 into the opening. Magnetic adhesive 730 will then flow upward around display assembly 720 based on the influence of the magnetic field generated by magnet 240. The adhesive bond formed between display assembly 720 and housing 710 using this technique is more uniform than conventional adhesive bonds formed using a pressure differential to cause the adhesive to flow, resulting in less leakage and a more effective seal when the adhesive bond is also used to form a waterproof seal between housing 710 and display assembly 720 of an electronic device.

[0070] It should be understood that 7A to 7B The technology shown is not limited to the joint between the housing and display assembly of an electronic device, but is generally applicable to the joint formed between any two components. In addition, the technology described herein can be used to form any adhesive joint formed by a magnetic field. For example, the technology can be applied to consumer electronic devices, industrial equipment, mechanical components, and circuit components placed on printed circuit boards. For example, magnetic adhesives can be used to improve the strength of adhesive joints used to fix electronic components (such as capacitors or integrated circuit packages) to PCBs in a staked manner. The increase in the strength of these adhesive joints can improve the shock rating or vibration handling of the electronic components of the device.

[0071] Figure 8 A portable electronic device 800 is shown according to some embodiments. Figure 8As shown, portable electronic device 800 includes a housing 802 having an opening on a front surface of housing 802. Display assembly 804 is disposed in the opening in housing 802. Display assembly 804 may include a device for presenting visual information, such as a liquid crystal display (LCD) element layer or an organic light emitting diode (OLED) layer. Display assembly 804 may also include a touch sensor, such as a capacitive touch sensor, for detecting touch input on a surface of display assembly 804.

[0072] In some embodiments, the portable electronic device 800 includes a protective cover that covers the top surface of the display assembly 804. The protective cover can include a glass layer. The portable electronic device can also include an input element 806, such as a button or a touch-sensitive surface. The input element 806 can be accessed through an opening in the protective cover.

[0073] The portable electronic device 800 may take the form of a tablet computer or a mobile phone (e.g., a cellular phone). In some embodiments, the housing 802 of the portable electronic device 800 includes a flange, such as flange 712, within the front opening of the housing 802. Figure 7A and Figure 7B The described technique allows the magnetic adhesive 730 to flow into the gap between the housing 802 and the display assembly 804 to bond the display assembly 804 to the flange.

[0074] Figures 9A to 9B A laptop computer 900 utilizing a fastener-free securing mechanism is shown according to some embodiments. Figure 9A As shown, laptop computer 900 includes a top portion 902 and a base portion 904. Top portion 902 includes a housing having an opening. Display assembly 906 is secured in the opening of the housing included in top portion 902. Base portion 904 includes a housing defining an interior volume. Functional components of laptop computer 900 (including but not limited to a processor, memory, antenna, radio frequency transceiver, energy storage device, one or more printed circuit boards, etc.) may be secured within the interior volume. Base portion 904 may also include input devices such as a keyboard and / or a touchpad, which are secured to the housing and accessible through the top surface of base portion 904.

[0075] During assembly, functional components are typically secured within the housing of base portion 904, and a cover is then fastened to the housing to close the opening into the interior volume to protect the functional components disposed therein. The look and feel of a laptop computer can be an important factor in a customer's purchasing decision. Therefore, one goal of laptop computer manufacturers can be to improve the industrial design of their laptop computers. One way to improve the industrial design is to reduce the amount of visible fasteners from the exterior surface of the housing.

[0076] like Figure 9B 9, a fastener-free securing mechanism is shown to secure component 914 to support structure 912 within the interior volume of housing 910 of base portion 904 of laptop computer 900. In some embodiments, support structure 912 comprises ribs formed in housing 910. Conventionally, screws or other mechanical fasteners would be used to secure component 914 to support structure 912 by passing the mechanical fasteners through through-holes formed in component 914 and engaging the mechanical fasteners with support structure 912. In contrast, a fastener-free securing mechanism encapsulates the fastening means on the inside of component 914 so that the fastening means is not visible from the exterior surface of component 914.

[0077] In some embodiments, the fastener-free securing mechanism includes a cured magnetic adhesive 920 that secures the support structure 912 to the component 914. The magnetic adhesive 920, prior to curing, is characterized by ferromagnetic particles dispersed within a liquid adhesive material, the ferromagnetic particles having a size and shape that facilitates the flow of the liquid adhesive material in response to a magnetic field. The magnetic adhesive 920 can be similar to the magnetic adhesive 100 described above. During assembly, magnets 940 placed on a surface of the housing 910 generate a magnetic field proximate to the joint between the component 914 and the support structure 912. The cured magnetic adhesive 920 forms a rounded corner on at least one side of the joint between the component 914 and the support structure 912.

[0078] The joint formed between component 914 and support structure 912 can be displaced, perhaps significantly displaced, from the seam between component 914 and housing 910, which is visible from the outer surface of component 914. Therefore, magnetic adhesive 920 is dispensed on the inner surface of component 914 before component 914 is brought close to housing 910. Magnet 940 can be placed on housing 910 after component 914 is brought close to housing 910. Alternatively, magnet 940 can be held in place before component 914 is brought close to housing 910.

[0079] It should be understood that the cured magnetic adhesive 920 forms a fillet on at least one side of the joint between the component 914 and the support structure 912. The shape of the fillet depends on the strength of the magnetic field generated by the magnet 940, the position of the magnet 940 relative to the joint, and the material of the housing 910, the support structure 912, the component 914, and any other components positioned near the joint (such as the functional component 960). The magnetic field can be adjusted to obtain the desired fillet shape. The desired fillet shape can be designed to accommodate additional components around the joint. For example, the functional component 960 can be a touchpad component that is fixed to the housing 910 near the support structure 912. Therefore, the shape of the fillet should be adjusted to prevent interference with the functional component 960, including preventing the functional component 960 from accidentally adhering to the support structure, which may make it more difficult to repair the laptop computer 900.

[0080] In some embodiments, the seam between component 914 and housing 910 can also be sealed with magnetic adhesive 930. 7A to 7B , magnetic adhesive 930 can be dispensed onto the surface of housing 910 and then forced into the seam by placing magnet 950 proximate the seam and adjacent to the outer surface of component 914 and / or housing 910. Once cured, magnetic adhesive 930 forms a barrier that prevents liquid from entering the interior volume of housing 910.

[0081] It should be understood that in other embodiments, the components 914 secured to the support structure 912 can be enclosed within the interior volume of the housing 910 by a separate cover secured to the housing 910. In other words, the components 914 secured to the support structure 912 can be internal components that are not visible on any exterior surface of the laptop computer 900. In other embodiments, the components 914 can include the display assembly 906 secured to the housing of the top portion 902 of the laptop computer 900.

[0082] Figure 10 1 is a flow chart of a method 1000 for forming an adhesive bond at a joint between components of a housing of an electronic device, according to some embodiments. Method 1000 can be implemented using a fixture that includes a magnetic element and an optional induction heating element. In some embodiments, the fixture can be automated using one or more actuators controlled by a control system.

[0083] At 1002, an adhesive is applied to the substrate at locations corresponding to joints to be formed between the substrate and the component. The adhesive includes magnetic particles dispersed therein. In some embodiments, the adhesive is in a liquid state having a viscosity sufficient to enable the adhesive to flow in response to movement of the magnetic particles under the influence of a magnetic field.

[0084] At 1004, a magnetic element is placed near the joint to generate a magnetic field. The magnetic field interacts with the magnetic particles in the adhesive to cause the adhesive to flow in a direction corresponding to the magnetic field. In some embodiments, the magnetic element is a permanent magnet. In other embodiments, the magnetic element is an electromagnet.

[0085] At 1006, the adhesive is cured under the influence of the magnetic field. The adhesive transforms from a liquid state to a solid state to form an adhesive bond at the joint, the shape of the adhesive bond being determined at least in part by the strength and orientation of the magnetic field proximate the joint.

[0086] Figure 11 is a flow chart of a method 1100 for influencing a magnetic substance using a magnetic field, according to some embodiments. The method 1100 can be practiced with any liquid substance that can be transformed from a liquid state to a solid state and exhibits properties sufficient to facilitate controlled flow of the liquid substance in response to movement of magnetic particles dispersed in the liquid substance.

[0087] At 1102, a substance comprising magnetic particles is dispensed onto a substrate. In some embodiments, the substance is dispensed in a liquid state and exhibits a viscosity of at least 10,000 cP in the liquid state. The substance may include ferromagnetic particles at a concentration of at least 20% by weight, the particles having a major dimension of less than 200 microns in length.

[0088] At 1104, a magnetic field is provided to cause the substance to flow from the first location to the second location. The substance flows toward the source of the magnetic field under the influence of attractive forces experienced by magnetic particles dispersed in the substance, which force the magnetic particles closer to the source of the magnetic field.

[0089] At 1106, the substance undergoes a transition from a liquid state to a solid state under the influence of a magnetic field. In some embodiments, the state transition is induced by the introduction of radiation (e.g., UV light) or heat to the substance. In other embodiments, the state transition occurs over a period of time after exposure to an environment (e.g., air) or in response to a natural chemical reaction between components of the substance. In some embodiments, the magnetic field can be reduced or removed once the substance reaches a gel point (where crosslinking in the polymers of the substance causes a significant increase in the viscosity of the liquid).

[0090] The various aspects, embodiments, implementations, or features of the described embodiments may be used individually or in any combination. The various aspects of the described embodiments may be implemented by software, hardware, or a combination of hardware and software. The described embodiments may also be implemented as computer-readable code on a non-transitory computer-readable medium. A non-transitory computer-readable medium is any data storage device that can store data that can then be read by a computer system. Examples of non-transitory computer-readable media include read-only memory, random access memory, CD-ROM, HDD, DVD, magnetic tape, and optical data storage devices. Non-transitory computer-readable media may also be distributed on network-coupled computer systems so that the computer-readable code is stored and executed in a distributed manner.

[0091] For illustrative purposes, the foregoing description uses specific nomenclature to provide a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that specific details are not required to practice the embodiments. Therefore, the foregoing descriptions of specific embodiments are presented for illustration and description purposes. The foregoing descriptions are not intended to be exhaustive or to limit the embodiments described to the precise forms disclosed. It will be apparent to those skilled in the art that, in light of the above teachings, many modifications and variations are possible.

Claims

1. An electronic device comprising: substrate; a component having a first bonding surface and a second bonding surface, the component being secured to the substrate via a multi-layer adhesive joint; a first magnetic adhesive having: (i) a first ordered arrangement of first magnetic particles, and (ii) a first shape according to the first ordered arrangement such that the first magnetic adhesive is in bonding contact with the first bonding surface and the substrate, and a second magnetic adhesive having: (i) a second ordered arrangement of second magnetic particles, and (ii) a second shape based on the second ordered arrangement, such that the second magnetic adhesive covers the first magnetic adhesive, the substrate, and the second bonding surface and is in bonding contact with the first magnetic adhesive, the substrate, and the second bonding surface.

2. The electronic device according to claim 1, wherein the first magnetic particles and the second magnetic particles comprise ferromagnetic particles, and wherein: (i) the first ordered arrangement comprises the first magnetic particles being linearly arranged and distributed in accordance with the first shape, and (ii) the second ordered arrangement comprises the second magnetic particles being linearly arranged and distributed in accordance with the second shape.

3. An electronic device according to claim 1, wherein when the second magnetic adhesive is in an uncured state and the second magnetic particles are subjected to a magnetic field having magnetic field lines, the second magnetic particles are driven to move according to the magnetic field lines to form the second ordered arrangement, so that the second magnetic adhesive exhibits the second shape.

4. The electronic device according to claim 1, wherein: The first magnetic adhesive comprises a first viscosity, and The second magnetic adhesive includes a second viscosity different from the first viscosity. 5 . The electronic device of claim 3 , wherein the second magnetic adhesive comprises a liquid polymer having a viscosity in a range of 10,000 to 30,000 centipoise in an uncured state. 6 . The electronic device according to claim 1 , wherein the first magnetic adhesive extends along the first bonding surface to a first height, and the second magnetic adhesive extends along the first bonding surface to a second height different from the first height.

7. The electronic device of claim 1 , wherein the first magnetic adhesive comprises magnetic particles dispersed in a non-magnetic liquid polymer, and wherein the shape of the first magnetic adhesive is based on the first magnetic particles (i) being aligned with magnetic field lines and (ii) being distributed according to a magnetic field strength provided by an external magnetic field. 8 . The electronic device according to claim 1 , wherein the first magnetic particles comprise ferromagnetic metal.

9. The electronic device of claim 1, wherein the first magnetic particle comprises a non-ferromagnetic core coated with a ferromagnetic metal.

10. The electronic device of claim 7, wherein the non-magnetic liquid polymer is cured using an induction heating element to generate heat in the magnetic particles.

11. The electronic device of claim 1 , wherein the first magnetic adhesive provides a waterproof seal between the substrate and the component.

12. The electronic device of claim 1, wherein the substrate is disposed within an interior volume of the component. 13 . The electronic device according to claim 1 , wherein the first magnetic adhesive is provided between the component and the substrate.

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