Method for manufacturing gasket for electromagnetic shielding

Abstract

The present disclosure relates to a method of manufacturing a gasket for electromagnetic shielding wherein the method comprises the steps of: a) providing a composition comprising i) a viscous material and ii) particles having electrical and ferromagnetic and / or ferrimagnetic properties; the invention relates to a method for manufacturing a substrate, comprising a) applying a composition to the substrate by applying the composition in the form of a gasket having a length, a width and a height, c) applying a magnetic field on the gasket resulting in a change in the geometry of the gasket, preferably the change resulting in an increase in the height of the gasket, where the applied magnetic field is in the range of 750 to 2500 gauss. The present disclosure further relates to gaskets manufactured by the method and uses thereof.

Description

Technical Field

[0001] The present disclosure generally relates to a method of manufacturing a gasket for electromagnetic shielding. Further, the present disclosure relates to a gasket for electromagnetic shielding produced by such a method and its use. Background Art

[0002] With the increasing demand for electronic devices such as computers, mobile phones, and other wireless devices, the demand for efficient and optimized components for constructing such electronic devices is growing.

[0003] A common problem in the development of electronic devices is electromagnetic interference EMI (electromagnetic interference) present in the environment. EMI can damage or destroy, for example, the electrical systems and equipment present in an electronic device, rendering it inoperative. In addition, many electronic devices include components that generate EMI themselves, and these EMI must be shielded to protect other sensitive components present in the electronic device. Therefore, it is important to effectively shield sensitive components from the effects of EMI in order to ensure the proper operation of the electronic device.

[0004] A common solution is to encapsulate EMI-emitting or EMI-sensitive components in a conductive housing, thereby creating a Faraday cage around the components. If the conductive housing is composed of two or more mating surfaces, the gaps or joints between the mating surfaces must be effectively sealed by an EMI shielding gasket. However, the sealing gasket must be conductive at the same time to ensure the operation of the Faraday cage.

[0005] One solution proposed is to join two surfaces by a gasket comprising a viscous material and a conductive material dispersed within the viscous material. Conventionally, the gasket is manufactured by dispensing a viscous material containing a conductive material onto a first substrate and then processing it such that the viscous material assumes a non-viscous state and thus assumes a fixed shape. The gasket serves as a conductive sealing joint between the first substrate and the second substrate.

[0006] Since the conductive materials used in such gaskets are expensive, different alternatives have been developed to reduce the amount of conductive material required. One proposed solution to such a problem is given in WO 03037057, which discloses the use of particles having electrical and conductive properties.

[0007] However, in recent years, the industry has been striving to manufacture smaller and smaller electronic devices. This places higher mechanical requirements on the gaskets used.

[0008] To ensure a good sealing effect, the gasket must be compressed between the surfaces of the first substrate and the second substrate to effectively connect the two surfaces. If properly connected, the gasket will ensure electrical conductivity between the first substrate and the second substrate and EMI shielding between the inside and the outside of the gasket, i.e., electromagnetic interference will not pass through the gasket.

[0009] If the compression force required to effectively connect the two surfaces through the gasket and achieve electrical conductivity is too high, the substrates used may be damaged. This is especially a problem in the development of small electronic devices because smaller and thus more vulnerable components are required to manufacture these devices. High compression force requires, for example, the use of a thicker cover and a shorter distance between the screws, thus resulting in an increase in the product-related costs for manufacturing the electronic devices.

[0010] Although the solution proposed in WO 03037057 reduces the amount of expensive particles required compared to previously known solutions in the art, it does not mention specific key product parameters such as the achieved electromagnetic shielding, the electrical conductivity of the gasket material, and the compression force of the gasket.

[0011] Therefore, there is still a need to provide a gasket for electromagnetic shielding that exhibits sufficiently good EMI shielding and electrical conductivity while exhibiting a low compression force and compression set compared to previously known solutions. Summary of the Invention

[0012] An object of the present disclosure is to provide an improved method for manufacturing a gasket for electromagnetic shielding.

[0013] Another object is to provide a method for manufacturing a gasket for electromagnetic shielding that produces such a gasket that exhibits good electromagnetic shielding performance, good electrical conductivity performance, and low compression force and compression set compared to the prior art.

[0014] Another object of the present invention is to provide a gasket for electromagnetic shielding.

[0015] Another object is to provide a gasket for electromagnetic shielding that exhibits good electromagnetic shielding performance, resistance performance, and low compression force compared to the prior art.

[0016] Another object of the present disclosure is to provide a gasket for electromagnetic shielding that is used for electromagnetic shielding in products such as electronic devices.

[0017] In a first aspect, the present disclosure relates to a method for manufacturing a gasket for electromagnetic shielding, wherein the method comprises the following steps:

[0018] a. Providing a composition, the composition comprising i) a viscous material and ii) particles having electrical conductivity and ferromagnetic and / or ferrimagnetic properties;

[0019] b. Applying the composition to a substrate by applying the composition in the form of a spacer having a length, a width, and a height.

[0020] c. Applying a magnetic field to the spacer, causing a change in the geometry of the spacer. Preferably, the change causes an increase in the height of the spacer, and

[0021] wherein the applied magnetic field is in the range of 750 gauss to 2500 gauss.

[0022] The composition can be applied to the substrate by any one of a dispersion process, a jet dispensing process, or a screen printing process.

[0023] By applying a magnetic field in the range of 750 gauss to 2500 gauss to the composition, a spacer for electromagnetic shielding is manufactured having sufficiently good EMI shielding performance and electrical resistance, as well as compressive force and compression set. The magnetic field can be applied in one direction so as to act perpendicular to the spacer along its longitudinal extension.

[0024] Compressive force refers to the force required to compress the spacer by 50%. This value represents the force required to compress the spacer in order to effectively connect two substrates, thereby ensuring EMI shielding between the inside and the outside of the spacer and electrical conductivity between the two connected substrates. Compression set refers to the permanent deformation of the spacer remaining after the force applied to the spacer is removed.

[0025] Importantly, the applied magnetic field is strong enough such that the particles present in the composition can interact with the magnetic field. Due to the ferromagnetic and / or ferrimagnetic nature of the particles, the particles will be affected by the magnetic field and will orient themselves in the same direction as the magnetic field. If strong enough, the interaction of the particles with the magnetic field as the particles move with the applied magnetic field will cause a change in the geometry of the spacer. Preferably, the change in geometry causes an increase in the height of the spacer, which means that the spacer changes its shape from a D-shape to a triangular geometry having a shape that tapers from the base to the apex. The tapered shape is desirable because this reduces the compressive force of the spacer. In one embodiment of the present disclosure, the applied magnetic field causes an increase in the height of the spacer and a decrease in the width.

[0026] In order to produce the desired tapered shape, it is therefore important that the applied magnetic field is strong enough to be able to change the geometry of the spacer. However, it has been found that too strong a magnetic field will adversely affect some of the properties of the formed spacer. For example, the inventors have found that too strong a magnetic field will cause the electrical resistance performance to be impaired, which means a reduction in the electrical conductivity. Good electrical conductivity is a key parameter for spacers used in electronic devices.

[0027] In addition, too strong a magnetic field can also lead to a reduction in shielding performance. If the applied magnetic field excessively changes the geometry of the gasket, the shielding performance will be impaired because the gasket becomes too thin for electromagnetic waves to penetrate, or too thin to be tilted during assembly when joining two substrates through the gasket, thus leaving a gap opening.

[0028] The gasket manufactured according to the method of the present disclosure can be used to shield electronic devices and equipment, such as, for example, the base stations for mobile phones. In such a case, the gasket is arranged on a substrate, and then the substrate is enclosed with a properly designed mating substrate. The substrate can be a housing. The gasket will ensure good electrical contact between the two substrates and also provide electromagnetic shielding between the inside and the outside of the gasket.

[0029] In an exemplary method, the applied magnetic field is in the range of 750 gauss to 2250 gauss.

[0030] In an exemplary method, the applied magnetic field is in the range of 1000 gauss to 2000 gauss.

[0031] Through such an exemplary method, a gasket for electromagnetic shielding is manufactured, wherein the gasket has optimized EMI shielding performance and resistance, as well as compressive force and compression set. As described above and as demonstrated in the present disclosure, it has been found that the strength of the applied magnetic field greatly affects these four properties, and when using the magnetic field strength according to the present disclosure, the optimization of these properties is achieved.

[0032] As disclosed above, the gasket includes particles having conductivity and ferromagnetic and / or ferrimagnetic properties. In an exemplary method, the particles include an inner layer containing nickel, graphite, iron, cobalt, or an alloy containing two or more of these. The particles can further include an outer layer containing silver or nickel. In one embodiment, the particles include a first layer containing nickel and an outer layer containing silver. In one embodiment, the particles include an inner layer containing graphite and an outer layer containing nickel. In one embodiment, the particles include an inner layer containing graphite, an intermediate layer containing nickel, and an outer layer containing silver.

[0033] Through such an exemplary method, particles with improved magnetic properties and conductive properties can be provided, which means that the amount of particles required to achieve sufficiently good conductivity is reduced, thus reducing costs.

[0034] In an exemplary method, the particles have a diameter in the range of 15 μm to 180 μm, preferably between 30 μm and 90 μm, more preferably between 40 μm and 80 μm, and preferably have an average diameter of about 60 μm. The particles need to be large enough to be able to make electrical contact with each other and thus conduct electricity. However, if they are too large, the particles will cause production difficulties, including needle clogging and production stoppages during dispensing, and dispensing requires the use of fine dispensing needles to create the desired spacer height and width.

[0035] In an exemplary method, the method further includes a curing step d), wherein the curing step results in a cured spacer in an elastic, non-sticky state. Preferably, the curing is carried out by temperature treatment at 10 °C to 250 °C, preferably by temperature treatment at 60 °C to 200 °C for at least 15 minutes, or by temperature treatment at 15 °C to 60 °C for at least 6 hours. By curing the spacer, it is ensured that a spacer with a fixed shape is formed.

[0036] In an exemplary method, the spacer after the curing step d) contains 10 wt% to 50 wt% of a viscous material and 50 wt% to 90 wt% of particles. As mentioned before, the spacer needs to contain a sufficient amount of particles to conduct electricity while having a viscosity suitable for applying the composition for forming the spacer in an industrially feasible manner.

[0037] In an exemplary method, the spacer after the curing step d) contains 20 wt% to 40 wt% of a viscous material and 60 wt% to 80 wt% of particles.

[0038] In an exemplary method, the composition further contains a viscosity reducer, preferably selected from toluene, xylene, petroleum distillates with a boiling point between 50 °C and 250 °C, or silicone oils with a boiling point between 50 °C and 250 °C. By including a viscosity reducer, a composition that is easier to dispense is achieved. Preferably, the viscosity reducer evaporates during the curing step d).

[0039] In an exemplary method, the composition contains 5 wt% to 50 wt% of a viscous material, 50 wt% to 90 wt% of particles, and 2 wt% to 20 wt% of a viscosity reducer. Increasing the amount of particles and thus increasing the conductivity can lead to an increase in the viscosity of the composition. This may be undesirable because a composition with too high a viscosity may be difficult to apply on a substrate.

[0040] In an exemplary method, the composition contains 15 wt% to 40 wt% of a viscous material, 60 wt% to 80 wt% of particles, and 5 wt% to 15 wt% of a viscosity reducer.

[0041] In an exemplary method, a magnetic field is applied for a period of 5 to 15 seconds. This time interval ensures that the gasket is subjected to the magnetic field for a long enough time to change the geometry of the gasket and thus provide excellent electromagnetic sealing performance and electrical conductivity for the gasket.

[0042] In an exemplary method, the adhesive material is selected from silicone rubber, polyurethane, and thermoplastic elastomer.

[0043] In an exemplary method, the composition has a viscosity of 20 Pas to 120 Pas. To ensure good dispensability, it is important that the composition has a low viscosity. At the same time, the viscosity must be high enough so that the composition retains its shape (height and width) after being applied to the substrate and does not flow out before it hardens or cures. The inventors have found that the optimal viscosity to achieve the above two requirements is between 20 Pas and 120 Pas. In an exemplary method, the viscosity of the composition is between 40 Pas and 100 Pas.

[0044] The viscosity is measured using a Haake Rotovisco rheometer equipped with a plate - to - plate system at a shear rate of 10 s -1 The distance between the two plates is 0.5 mm. The measurement is carried out at 23 °C and the result is given in the unit Pas.

[0045] In a second aspect, the present disclosure relates to a gasket for electromagnetic shielding produced by any of the methods according to the first aspect.

[0046] In an exemplary gasket, when measuring the resistance according to the method disclosed in the present disclosure, the gasket has a resistance of less than 1 Ω, preferably less than 0.5 Ω. The resistance is measured by pressing two square electrodes with a force of 7.5 N onto the gasket. Each of the two square electrodes has a size of 10×10 mm. On the gasket, the distance between the two electrodes is set to 10 mm.

[0047] In a third aspect, the present disclosure relates to a gasket according to the second aspect for electromagnetic shielding in an electronic device, such as a mobile communication device, a base station, a computer device, or an electronic enclosure in automotive applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The present disclosure will now be described by way of example with reference to the accompanying drawings, in which:

[0049] Figure 1 Illustrated is a gasket applied to a substrate before applying a magnetic field according to the present disclosure.

[0050] Figure 2 Shown is an embodiment of the present disclosure, illustrating a gasket that has been subjected to a magnetic field according to the present disclosure.

[0051] Figure 3 Illustrates two substrates joined by a gasket according to the present disclosure. Detailed Description

[0052] The detailed description with reference to the disclosed embodiments should be considered as examples of combining the above - specific features. It should be understood that additional examples can be achieved by combining other features and / or fewer / more features compared to the disclosed embodiments. Thus, the drawings disclose exemplary embodiments rather than exclusive combinations. In this case, it should also be noted that, for simplicity, all drawings are disclosed schematically, provided there is no other indication.

[0053] As used herein, "wt%" refers to the weight percentage of the component mentioned in the total weight of the compound or composition mentioned.

[0054] The present disclosure relates to a method of manufacturing a gasket for electromagnetic shielding, which particularly includes the step of applying a magnetic field in the range of 750 Gauss to 2500 Gauss on the gasket. The applied magnetic field according to the present disclosure causes the gasket for electromagnetic shielding to exhibit good electromagnetic shielding performance, electrical conductivity, and compressive force.

[0055] Figure 1 Illustrates a partial cross - sectional view of gasket 1 in a state before the application of a magnetic field according to the present disclosure. As mentioned above, the gasket is manufactured by applying a composition to a substrate 2. Figure 1 In the illustrated embodiment, the gasket is applied such that a length L1, a width W1, and a height H1 are formed. The composition forming gasket 1 includes a viscous material 3 and particles 4 having electrical conductivity and ferromagnetic and / or ferrimagnetic properties.

[0056] The composition can be applied by dispensing the composition from a needle nozzle (not shown), which moves on substrate 2 along a predetermined extension range of the substrate.

[0057] The viscous material 3 is selected from silicone rubber, polyurethane, and thermoplastic elastomer.

[0058] Now turning to Figure 2 , Figure 2 Illustrates gasket 1 that has been subjected to a magnetic field F according to the present disclosure. For clarity, the applied magnetic field is shown by arrow F.

[0059] The magnetic field F is applied to gasket 1 in a direction so as to act perpendicular to gasket 1 and substrate 2. Figure 2 In the illustrated embodiment, the magnetic field F is applied in a direction away from the upper surface 21 of substrate 2, on which gasket 1 is disposed. The magnetic field F can be applied by a magnetic device (not shown) such as an electromagnet.

[0060] When the gasket 1 containing the particles 4 having conductivity and ferromagnetic and / or ferrimagnetic properties is subjected to a magnetic field F, the particles 4 will be affected by the magnetic field F and orient themselves in the same direction as the magnetic field F. Due to the force of the magnetic field, the overall geometry of the gasket 1 will also change to a more conical shape. After applying the magnetic field, the gasket 1 may exhibit different heights, i.e., an increased height. In Figure 2 the illustrated embodiment, the gasket 1 has a substantially triangular geometry that tapers from a base 11 to a vertex 12.

[0061] Now turning to Figure 3 , which shows two substrates 2a and 2b joined by the gasket 1 according to the present disclosure. The gasket 1 ensures good electrical conductivity between the substrates 2a and 2b, thus forming a Faraday cage. Further, due to the electromagnetic shielding properties of the gasket 1, it also inhibits the propagation of electromagnetic waves between the formed seals.

[0062] Examples

[0063] In the following examples, two different compositions were analyzed. The compositions were treated with different magnetic field intensities, and the resulting electromagnetic shielding properties, electrical resistance, compressive force, and compression set were evaluated.

[0064] Materials:

[0065] Composition A: A fluid silicone rubber comprising a hydrocarbon solvent and particles, the particles comprising an inner layer containing nickel and an outer layer containing silver. Composition A includes 15 wt% to 40 wt% of a viscous material, 60 wt% to 80 wt% of particles, and 5 wt% to 15 wt% of a viscous reducing agent.

[0066] Composition B: A fluid silicone rubber comprising a hydrocarbon solvent and particles, the particles comprising an inner layer containing graphite and an outer layer containing nickel. Composition B includes 15 wt% to 40 wt% of a viscous material, 60 wt% to 80 wt% of particles, and 5 wt% to 15 wt% of a viscous reducing agent.

[0067] Example 1: Compressive force analysis

[0068] First, to analyze the compressive force of gaskets made with different magnetic field intensities, two different gaskets made of Composition A or B were dispensed onto thin aluminum sheets. Subsequently, each gasket was treated by applying a magnetic field using an electromagnet for a period of 15 seconds. Four different magnetic field intensities were studied. Finally, the treated gaskets were cured at 150 °C for 30 minutes. The gaskets were dispensed in dimensions such that after the magnetic field application and curing steps, the height of the treated gaskets was 1.6 mm.

[0069] Then the compressive force of the gaskets was analyzed and how the intensity of the applied magnetic field affects the compressive force.

[0070] Measurements were carried out in a tensile testing machine capable of measuring force and deflection. In the present disclosure, a tensile testing machine marked Hounsfield H5K-S was used. Three measurements were made on the gaskets manufactured with Composition A, and six measurements were made on the gaskets manufactured with Composition B. The gaskets were compressed by a probe with a size of 10x10 mm to 50% of the original thickness of the gasket. The compression speed used was 1 mm / min. The results are shown in Table 1.

[0071] Table 1

[0072] Composition – Magnetic field strength (Gauss) Compressive force at 50% compression (N) A – 500 Gauss 81±3 A – 1000 Gauss 64±1 A – 3800 Gauss 44±3 B – 500 Gauss 66±3 B – 2000 Gauss 33±1 B – 3800 Gauss 28±1

[0073] It can be seen that when the strength of the applied magnetic field increases, the compression force required to compress 50% of the gasket made of Composition A or B decreases. If the gasket is used to join two substrates together, this means that a smaller force is required to effectively compress the gasket to join and seal the substrates together. This is a desirable property because the gasket needs to provide good electrical contact between the substrates.

[0074] Example 2: Resistance analysis

[0075] First, in order to analyze the resistance (i.e., conductivity) of the gaskets produced with different magnetic field strengths, two different gaskets made of Composition A or B were placed on thin aluminum sheets. Subsequently, each gasket was treated by applying a magnetic field for a period of 15 seconds using an electromagnet. Four different magnetic field strengths were studied. Finally, the treated gaskets were cured at 150 °C for 30 minutes. The gaskets were sized such that after the application of the magnetic field and the curing step, the height of the treated gaskets was 1.6 mm.

[0076] Then the resistance of the gaskets was analyzed and how the strength of the applied magnetic field affects the resistance of the gaskets.

[0077] The resistance was measured by pressing two square electrodes with a force of 7.5 N onto the gasket, and each of the two square electrodes had a size of 10×10 mm. On the gasket, the distance between the two electrodes was set to 10 mm. Six measurements were made for each material and magnetic strength. The results are shown in Table 2.

[0078] Table 2

[0079] Composition – Magnetic field strength (Gauss) Resistance (mΩ) A – 500 Gauss 200±28 A – 1000 Gauss 63±24 A – 3800 Gauss 120±24 B – 500 Gauss 92±5 B – 2000 Gauss 85±4 B – 3800 Gauss 105±4

[0080] It can be seen that the gaskets produced from Composition A or B show the best resistance at 1000 Gauss and 2000 Gauss respectively. As mentioned before, low resistance is a key parameter for gaskets used in electronic devices. If a gasket with high resistance is used to connect two substrates in an insulating housing, the housing may not effectively protect the components inside the insulating housing from electromagnetic interference, thus disrupting the operation of the components.

[0081] Example 3: Electromagnetic shielding analysis

[0082] First, to analyze the electromagnetic shielding performance of gaskets produced with different magnetic field strengths, two different gaskets made from Composition A or B were allocated on a cavity plate made of aluminum. Subsequently, each gasket was treated by applying a magnetic field for a period of 15 seconds using an electromagnet. Four different magnetic field strengths were studied. Finally, the treated gaskets were cured at 150 °C for 30 minutes. The gaskets were allocated in terms of size such that after the application of the magnetic field and the curing step, the height of the treated gaskets was 1.6 mm.

[0083] Then the electromagnetic shielding performance of the gaskets was analyzed, as well as how the strength of the applied magnetic field affects the electromagnetic shielding performance of the gaskets.

[0084] Before testing, a cover was attached to the cavity plate with bolts to enclose the cavity. A spacer was placed between the cavity fixture and the cover such that the gasket was compressed by 37% compared to its original height. The dimensions of the gasket were determined by an optical measuring machine. A short - circuit probe was assembled in each cavity. A network analyzer was connected and used to feed a signal into one of the cavities and measure the interference inside the other cavity. The shielding effect of the gasket was measured in dB as the S21 response in the frequency range from 0.3 GHz to 20 GHz. The results are shown in Table 3.

[0085] Table 3

[0086]

[0087] It can be seen that when a magnetic field of 1000 Gauss is applied, a significantly optimal electromagnetic shielding is achieved for the gaskets made from Composition A. If the magnetic field strength is increased for Composition A, a weakened electromagnetic shielding is achieved. For the gaskets made from Composition B, high electromagnetic shielding values are obtained when the gaskets are treated with a magnetic field of 500 Gauss or 2000 Gauss. However, increasing the magnetic field strength above 3000 Gauss results in a deterioration of the shielding performance.

[0088] Example 4: Compressive set

[0089] First, to analyze the compression set of gaskets made with different magnetic field strengths, two different gaskets made from Composition A or B were dispensed onto thin aluminum sheets. Subsequently, each gasket was treated by applying a magnetic field using an electromagnet for a period of 15 seconds. Four different magnetic field strengths were studied. Finally, the treated gaskets were cured at 150 °C for 30 minutes. The gaskets were dispensed in dimensions such that after the magnetic field application and curing steps, the height of the treated gaskets was 1.6 mm.

[0090] Then the compression set of the gaskets was analyzed.

[0091] Testing was carried out in accordance with ISO 815, with the difference that testing was carried out on the dispensed gaskets rather than on standardized molded cylindrical test specimens.

[0092] After curing, the height was measured using an optical measuring machine. Subsequently, the gaskets were subjected to 25% compression and placed in an oven at 100 °C for 72 hours. After testing, the height of the specimens was measured after 30 minutes of recovery.

[0093] The compression set was calculated using Equation 1.

[0094]

[0095] where h 0 is the initial thickness of the test piece (in millimeters), h 1 is the thickness of the test piece after recovery (in millimeters), and h s is the height of the space (in millimeters).

[0096] The results are shown in Table 4.

[0097] Table 4

[0098] Composition – Magnetic field strength (Gauss) Compressive set (%) A – 500 Gauss 49.6±1.1 A – 1000 Gauss 32.2±4.3 A – 3800 Gauss 31.7±4.7 B – 500 Gauss 24.5±2.4 B – 2000 Gauss 19.4±3.6 B – 3800 Gauss 19.6±3.6

[0099] It can be seen that by utilizing a stronger magnetic field strength, gaskets made from Composition A or B that maintain their shape after long-term compression are achieved, meaning that the gaskets perform better during the lifetime of the gasket.

[0100] Examples 1 to 4 show that when gaskets are manufactured by applying a magnetic field with a strength according to the present disclosure, significantly optimal resistance, electromagnetic shielding, compression force, and compression set can be achieved. It can be seen that treating the gaskets with a strong magnetic field results in softer gaskets, i.e., lower compression force and low compression set values. This can be attributed to the fact that a stronger magnetic field will more significantly change the geometry of the gaskets, thereby increasing the height of the formed triangular gaskets and decreasing their width.

[0101] However, as shown in Example 2, if the magnetic field strength is increased excessively, the resistance of the gasket will be damaged. In addition, as also shown in Example 2, a weak magnetic field results in a high resistance in the gasket, thereby reducing the conductivity. Since the gasket can be used in a housing to protect sensitive components within such a housing, it is important that the gasket has a low resistance to achieve good conductivity.

[0102] Similarly, as can be seen in Example 3, if the magnetic strength is too strong, the electromagnetic shielding performance of the gasket is also weakened. The applicant has found that, in order to achieve sufficiently good values for all these parameters (resistance, electromagnetic shielding, compressive force, and compression set), and thus obtain a gasket with improved performance compared to the prior art, it is preferred to manufacture the gasket according to the manufacturing method of the present disclosure.

Claims

1. A method for manufacturing a gasket for electromagnetic shielding, wherein, the method comprises the following steps: a) providing a composition comprising i) a viscous material and ii) particles having electrical conductivity and ferromagnetic and / or ferrimagnetic properties; b) applying the composition to a substrate by applying the composition in the form of a gasket having a length, a width and a height, c) applying a magnetic field to the gasket, causing a change in the geometry of the gasket, preferably, the change causes an increase in the height of the gasket, wherein, the applied magnetic field is in the range of 750 Gauss to 2500 Gauss.

2. The method according to claim 1, wherein, the applied magnetic field is in the range of 750 Gauss to 2250 Gauss.

3. The method according to claim 1, wherein, the applied magnetic field is in the range of 1000 Gauss to 2000 Gauss.

4. The method according to any one of claims 1 to 3, wherein, the particles comprise an inner layer comprising nickel, graphite, iron, cobalt or an alloy containing two or more of nickel, graphite, iron, cobalt, preferably, the particles further comprise an outer layer comprising silver or nickel.

5. The method according to any one of claims 1 to 4, wherein, the particles have a diameter in the range of 15 μm to 180 μm, preferably having an average diameter of about 60 μm.

6. The method according to any one of claims 1 to 5, wherein, the method further comprises a curing step d), wherein the curing is carried out by temperature treatment at 10 °C to 250 °C, preferably, by temperature treatment at 60 °C to 200 °C for at least 15 minutes, or by temperature treatment at 15 °C to 60 °C for at least 6 hours.

7. The method according to claim 6, wherein, after the curing step d), the gasket comprises 10 wt% to 50 wt% of the viscous material and 50 wt% to 90 wt% of the particles.

8. The method according to claim 6, wherein, after the curing step d), the gasket comprises 20 wt% to 40 wt% of the viscous material and 60 wt% to 80 wt% of the particles.

9. The method according to any one of claims 1 to 8, wherein, the composition further comprises a viscosity reducing agent, and the viscosity reducing agent is preferably selected from toluene, xylene, petroleum distillates having a boiling point between 50 °C and 250 °C or silicone oils having a boiling point between 50 °C and 250 °C.

10. The method according to claim 9, wherein, the composition comprises 5 wt% to 50 wt% of the viscous material, 50 wt% to 90 wt% of the particles and 2 wt% to 20 wt% of the viscosity reducing agent.

11. The method according to claim 9, wherein, the composition comprises 15 wt% to 40 wt% of the viscous material, 60 wt% to 80 wt% of the particles and 5 wt% to 15 wt% of the viscosity reducing agent.

12. The method according to any one of claims 1 to 11, wherein, the magnetic field is applied during 5 seconds to 15 seconds.

13. The method according to any one of claims 1 to 12, wherein, the adhesive material is selected from silicone rubber, polyurethane, and thermoplastic elastomer.

14. The method according to any one of claims 1 to 13, wherein, the composition has a viscosity of 20 Pas to 120 Pas.

15. The method according to any one of claims 1 to 14, wherein, the composition has a viscosity of 40 Pas to 100 Pas.

16. A gasket for electromagnetic shielding produced by the method according to any one of claims 1 to 15.

17. The gasket for electromagnetic shielding according to claim 16, wherein, when measuring the resistance according to the method disclosed in the present disclosure, the gasket has a resistance of less than 1 Ω, preferably less than 0.5 Ω.

18. Use of a gasket according to any one of claims 16 to 17 for electromagnetic shielding in products of electronic enclosures such as mobile communication devices, base stations, computer devices, or automotive applications.

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