Multilayer gasket

Abstract

The present disclosure relates to a gasket (100) for electromagnetic shielding wherein the gasket comprises a first layer (1) and a second layer (2) wherein the resistance of the first layer is lower than the resistance of the second layer and wherein the permeability of the second layer is higher than the permeability of the first layer. The present disclosure further relates to a method for manufacturing such a gasket.

Description

Technical Field

[0001] The present disclosure generally relates to a gasket for electromagnetic shielding. The gasket comprises at least two layers, wherein the first layer has a lower electrical resistance than the second layer, and the second layer has a higher magnetic permeability than the first layer. Furthermore, the present disclosure relates to a method for manufacturing such a gasket for electromagnetic shielding. Background Art

[0002] As the demand for electronic devices, such as computers, mobile phones, and other wireless devices, increases, the need for efficient and optimized components for building such electronic devices also grows.

[0003] Electromagnetic interference (EMI) is a common problem when developing electronic devices. EMI, which may be present in the environment or emitted by the electronic device itself, may interrupt or disrupt, for example, electrical systems and equipment within the electronic device, thereby damaging them.

[0004] A common approach is to enclose EMI-emitting or EMI-sensitive components in a conductive housing, thereby creating a Faraday cage around the components. If the conductive housing consists of two or more mating surfaces, the gap or joint between the mating surfaces must be effectively sealed by an EMI shielding gasket. However, the sealing gasket must also be conductive to ensure a functioning Faraday cage.

[0005] The proposed solution is to join two surfaces using a gasket, which includes a carrier material and a conductive material dispersed within the carrier material. Traditionally, gaskets are manufactured by, for example, dispensing a viscous material including the conductive material onto a first substrate and then treating it to render the viscous material non-adhesive and thereby assume a fixed shape. The gasket acts as a conductive sealing joint between the first and second substrates, as well as an EMI shield. Other methods used in industry to manufacture gaskets include extrusion, injection molding, and die casting.

[0006] Since conductive materials can be expensive, there is a need in the industry to reduce the use of expensive materials while still ensuring good EMI shielding properties of the gasket.

[0007] Another important requirement for gaskets used for electromagnetic shielding is their ability to maintain EMI shielding properties over time. Needless to say, if the shielding ability of a gasket degrades significantly over time, the overall functionality of the electronic device in which the gasket is included will be compromised.

[0008] As discussed above, it may be required to shield the device from EMI in the environment (i.e., protect the device inside the housing from external EMI) or to prevent EMI emitted by components inside the device from interfering with other sensitive components in the device (i.e., prevent EMI from leaking from the housing). For some applications, both requirements are desirable.

[0009] Examples of gaskets for electromagnetic shielding are proposed in GB2049718A and WO03037057. However, neither of these documents discloses a solution for improving the aging characteristics of the disclosed gaskets.

[0010] Thus, it would be desirable to provide a gasket for electromagnetic shielding that has improved EMI shielding characteristics and preferably maintains the EMI shielding characteristics over time, i.e., to provide a gasket with improved aging resistance. Further, it would also be preferable to reduce the use of expensive conductive materials while maintaining good EMI shielding characteristics of the gasket. Summary of the Invention

[0011] An object of the present disclosure is to provide a gasket for electromagnetic shielding that exhibits improved aging.

[0012] Another object of the present disclosure is to provide a gasket for electromagnetic shielding that has a reduced amount of expensive conductive particles.

[0013] Another object of the present disclosure is to provide a gasket for electromagnetic shielding that includes at least two layers, wherein the gasket exhibits maintained or improved shielding ability compared to a single-layer gasket for electromagnetic shielding that includes any one of the at least two layers.

[0014] Another object of the present disclosure is to provide a gasket for electromagnetic shielding that can be customized to optimize shielding characteristics depending on the placement of the EMI source relative to the gasket for electromagnetic shielding.

[0015] Another object of the present disclosure is to provide a method for manufacturing a gasket for electromagnetic shielding.

[0016] In a first aspect, the present disclosure relates to a gasket for electromagnetic shielding, wherein the gasket comprises:

[0017] a) a first gasket layer comprising a first carrier material and a first type of conductive particles, wherein the first gasket layer has a first resistance value R1 and a first permeability value P1;

[0018] b) a second gasket layer comprising a second carrier material and a second type of conductive particles, wherein the second gasket layer has a second resistance value R2 and a second permeability value P2;

[0019] wherein R1 < R2 and P2 > P1.

[0020] The carrier material may be an elastic material in a non-tacky state. The carrier material acts as a carrier matrix for the conductive particles. [[ID= 38]]

[0021] Surprisingly, it was discovered that by combining at least two layers, wherein the first layer has a lower electrical resistance than the second layer, and wherein the second layer has a higher magnetic permeability than the first layer, the EMI shielding performance of the gasket is improved. Without wishing to be bound by theory, it is believed that by combining at least two different layers having the aforementioned properties, the shielding properties within the gasket will differ. As such, EMI encountering the gasket according to the present disclosure will be subject to different EMI shielding properties, and thereby different EMI shielding mechanisms. It is believed that the layer with the lower electrical resistance and lower magnetic permeability values will act as a reflective barrier to EMI, while the layer with the higher electrical resistance and higher magnetic permeability values will act as an absorptive barrier to EMI. As such, a synergistic effect is created when combining at least two layers having different electrical resistance and magnetic permeability values, resulting in surprisingly good overall functionality of the gasket.

[0022] In the context of this disclosure, the "resistance value" of a layer should be interpreted as the measured resistance value of the layer when evaluated alone (ie, as a single-layer shim). When evaluating the ratio between the resistance values of two layers, the thickness of the two layers should be the same.

[0023] In the context of the present disclosure, a "permeability value" of a layer should be interpreted as a measure of the magnetization that a material acquires in response to an applied magnetic field.

[0024] The resistance value can be calculated using Ohm's law. For example, resistance can be measured by placing a pad on a conductive surface, applying square electrodes to the pad, and measuring the voltage recorded by the applied electrodes.

[0025] Furthermore, it has been found that by combining at least two layers having different properties according to the teachings disclosed herein, the amount of conductive particles having low resistance values can be reduced while still maintaining and / or improving EMI shielding properties compared to using a single layer of gaskets comprising the same conductive particles having low resistance values. Since particles having low resistance values are generally expensive, this reduces the manufacturing cost of the gasket.

[0026] The spacer can be in the shape of a longitudinally extending bead. The bead can also be, for example, rectangular, triangular, tapered, or D-shaped. However, those skilled in the art will appreciate that other shapes are also possible.

[0027] The gasket according to the present disclosure can be used to shield electronic devices and equipment, such as, for example, base stations for mobile phones. In such cases, the gasket is placed on a substrate, which is then enclosed with a suitably designed mating substrate. The substrate can be a housing. The gasket ensures good electrical contact between the two substrates and also provides EMI shielding between the interior and exterior of the gasket.

[0028] In one embodiment, the ratio between the first resistance value R1 of the first layer and the second resistance value R2 of the second layer is less than 0.5, more preferably less than 0.4.

[0029] With this ratio, each layer is capable of conducting current, thus ensuring that a functioning Faraday cage is formed when the two surfaces are joined by the gasket, while exhibiting different EMI shielding mechanisms between the at least two layers. As previously stated, it is important that the gasket is capable of conducting current in order to function as a gasket in a Faraday cage. Thus, each of the at least two layers must be capable of conducting current. A ratio of less than 0.5, and more preferably less than 0.4, between the first resistance value of the first layer and the second resistance value of the second layer ensures that each layer is capable of conducting current, while also ensuring that each layer is sufficiently different to have different EMI shielding properties.

[0030] In an embodiment, the first layer is configured to receive direct electromagnetic interference, and the second layer is configured to receive electromagnetic interference that has passed through the first layer.

[0031] In the context of the present disclosure, the term "direct electromagnetic interference" should be interpreted as electromagnetic interference emitted from a primary EMI source that should be shielded by the gasket. For example, the primary EMI source can be the environment (external or internal to the electronic device) or an EMI-emitting electronic device. Therefore, the gasket according to the present disclosure is configured in such a way that the first layer (i.e., the layer with the lowest resistance value) encounters the electromagnetic interference to be shielded from the primary EMI source before the second layer. In this way, the second layer receives EMI that has passed through the first layer.

[0032] As previously explained, it is believed that the first layer (the layer with the lower resistance value) shields EMI primarily through a reflection mechanism, while the second layer (the layer with the higher resistance value) shields EMI primarily through an absorption mechanism. The combination of the two different shielding mechanisms can result in improved aging resistance and EMI shielding properties of the gasket.

[0033] In one embodiment, the first layer has a resistance value less than 4 ohms, and the second layer has a resistance value less than 10 ohms. In one embodiment, the resistance value of the first layer is lower than the resistance value of the second layer.

[0034] This exemplary gasket provides a two-layer gasket with different EMI shielding mechanisms. The combination of the two different shielding mechanisms enables a reduction in the amount of low-conductivity conductive particles while maintaining or improving shielding properties compared to a single-layer gasket containing the same low-conductivity conductive particles. Since low-conductivity conductive particles can be expensive, reducing their amount in the gasket significantly reduces manufacturing costs.

[0035] In one embodiment, provided that the resistance of the first layer is lower than that of the second layer, the first layer has a resistance of 0.1 MΩ to 100 MΩ, and the second layer has a resistance of 50 MΩ to 150 MΩ.

[0036] In an embodiment, the gasket further comprises one or more additional layers comprising a carrier material and conductive particles.

[0037] By means of such an exemplary gasket, a gasket for electromagnetic shielding is provided with an additional layer having specific shielding properties or conductive properties. In this way, the function of the gasket can be further improved and customized depending on the desired use of the gasket.

[0038] In one embodiment, the gasket further comprises an anti-intrusion (IP) layer, preferably, the IP layer comprises one or more of silicone rubber and / or thermosetting polymer. Preferably, the anti-intrusion layer is arranged in contact with the second layer.

[0039] The anti-intrusion layer provides the gasket with a layer that protects against the intrusion of liquids (e.g., water) and solid objects (e.g., dust). Although this layer does not contribute to the EMI shielding properties, it further improves the overall functionality of the gasket by protecting the electronic device using the gasket from liquid and solid intrusion.

[0040] In one embodiment, the first carrier material and the second carrier material are each independently selected from at least one of silicone rubber and / or thermosetting polymer.

[0041] The carrier material must be suitable for forming a gasket for electromagnetic shielding. To ensure a good seal and shielding effect, the gasket must be compressed between the surfaces of the first and second substrates to effectively bond the two surfaces. If properly bonded, the gasket ensures electrical conduction between the first and second substrates and provides EMI shielding between the interior and exterior of the gasket, meaning that electromagnetic interference does not pass through the gasket.

[0042] Furthermore, the carrier material comprising the conductive particles needs to exhibit a suitable viscosity for dispersion, injection molding, extrusion, screen printing and / or compression molding. Preferably, both the first carrier material and the second carrier material have a viscosity of 20 Pas to 300 Pas.

[0043] In one embodiment, both the first conductive particles and the second conductive particles are metal particles.

[0044] In one embodiment, the first layer comprises conductive particles comprising silver, copper, gold and / or aluminum. Preferably, the first layer comprises conductive particles comprising silver.

[0045] Silver, copper, gold and / or aluminum are known to exhibit low electrical resistance values. Thus, without being bound by theory, it is believed that the first layer comprising conductive particles comprising silver, copper, gold and / or aluminum will act as an EMI reflective shield.

[0046] Furthermore, due to silver's antioxidant properties, the first layer comprising silver particles (as conductive particles) can improve the gasket's aging resistance. Thus, the silver particles in the first layer can act as a protective layer for the second layer, thereby improving the gasket's overall aging resistance compared to gaskets for electromagnetic shielding according to the present disclosure that include only one of the first or second layers.

[0047] In one embodiment, the second layer comprises conductive particles comprising nickel, ferrite, iron and / or cobalt. Preferably, the second layer comprising conductive particles comprises nickel.

[0048] Nickel is known to exhibit higher electrical resistance and higher magnetic permeability values compared to other conductive materials. As previously explained, it is believed that the higher magnetic permeability value produces an EMI absorption effect. Therefore, it is believed that the second layer including conductive particles including nickel will act as an EMI absorption shield.

[0049] In an embodiment, the ratio between the thickness of the first layer and the thickness of the second layer is between 1:20 and 20:1, preferably between 1:1 and 1:4.

[0050] The thickness of the first layer and the thickness of the second layer may be selected depending on, for example, the desired application of the gasket.

[0051] In an embodiment, the first layer and the second layer each comprise 30 wt% to 95 wt% conductive particles, preferably 45 wt% to 80 wt% conductive particles.

[0052] In one embodiment, the first layer includes 50 wt % to 80 wt % conductive particles and 20 wt % to 50 wt % carrier material.

[0053] In one embodiment, the second layer comprises 50% to 80% by weight of conductive particles and 20% to 50% by weight of a carrier material. As previously described, the gasket needs to include a sufficiently high amount of particles to conduct electricity while having a viscosity suitable for applying the gasket-forming composition in an industrially feasible manner. Excessively high amounts of particles may result in excessive viscosity, while excessively low amounts of particles may impair electrical conductivity.

[0054] In a second aspect, the present disclosure relates to a method for manufacturing a gasket for electromagnetic shielding, wherein the method comprises the following steps:

[0055] i) providing a first composition comprising a first viscous material and first conductive particles;

[0056] ii) Provide a second composition comprising a second adhesive material and a second type of conductive particles;

[0057] iii) Apply the first composition and the second composition to a substrate by applying them in the form of a multi-layer gasket, with the first composition as the first layer and the second composition as the second layer;

[0058] iv) Optionally apply an additional composition comprising an adhesive material and / or conductive particles;

[0059] v) Cure the applied compositions, thereby forming a multi-layer gasket, wherein the cured first layer has a first resistance value R1 and a first magnetic permeability value P1, and wherein the cured second layer has a second resistance value R2 and a second magnetic permeability value P2; and

[0060] where R1 < R2 and P2 > P1.

[0061] 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, after which the substrate is subsequently 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 will also provide electromagnetic shielding between the inside and the outside of the gasket.

[0062] Surprisingly, it has been found that by combining at least two layers, where the resistance value of the first layer is lower than that of the second layer and the magnetic permeability value of the second layer is higher than that of the first layer, the EMI shielding performance of the gasket manufactured according to the method is improved. Without being bound by theory, it is believed that by combining at least two different layers with the above characteristics, the shielding characteristics within the gasket will be different. Thus, the EMI encountered by the gasket according to the present disclosure will be subjected to different EMI shielding characteristics and thus different EMI shielding mechanisms. It is believed that the layer with the lowest resistance value and the lowest magnetic permeability value will act as a reflection barrier against EMI, while the layer with the highest resistance value and a relatively high magnetic permeability value will act as an absorption barrier against EMI. Thus, a synergistic effect is produced when combining at least two layers with different resistance values and magnetic permeability values.

[0063] Moreover, it has also been found that by combining at least two layers with different characteristics according to the disclosure herein, compared to using a single-layer gasket comprising the same conductive particles with a low resistance value, the amount of conductive particles with a low resistance value can be reduced while still maintaining and / or improving the EMI shielding characteristics. Since particles with a low resistance are usually expensive, this reduces the manufacturing cost of the gasket.

[0064] In one embodiment, the method is used to manufacture a gasket for electromagnetic shielding according to the first aspect.

[0065] In one embodiment, a ratio between the first resistance value of the first layer and the second resistance value of the second layer is less than 0.5, more preferably less than 0.4.

[0066] With this ratio, each layer is capable of conducting current, thus ensuring that a functioning Faraday cage is formed when the two surfaces are joined by the gasket, while also exhibiting different EMI shielding mechanisms between the at least two layers formed from the at least two compositions. As previously stated, it is important that the gasket is capable of conducting current in order to function as a gasket in a Faraday cage. Thus, each of the at least two layers must be capable of conducting current. A ratio of less than 0.5, and more preferably less than 0.4, between the first resistance value of the first layer and the second resistance value of the second layer ensures that each layer is capable of conducting current, while also ensuring that each layer is sufficiently different to have different EMI shielding properties.

[0067] In one embodiment, step iii) comprises applying the first composition and the second composition to the substrate simultaneously.

[0068] By such an exemplary method, the first composition and the second composition can be applied in a single application step. This results in a faster and more economical manufacturing process.

[0069] In one embodiment, the first composition is applied to receive direct electromagnetic interference, and the second composition is applied to receive electromagnetic interference that has passed through the first composition.

[0070] With such an exemplary method, applying the gasket depends on the location of the primary source of EMI to be shielded relative to the location of the gasket on the substrate to which the gasket is applied. For simplicity, according to such an exemplary method, the first composition is applied so as to face the primary source of EMI to be shielded when the gasket is used.

[0071] As previously explained, it is believed that the first layer (the layer with the lower resistance value) shields EMI primarily through a reflection mechanism, while the second layer (the layer with the higher permeability value) shields EMI primarily through an absorption mechanism. The combination of the two different shielding mechanisms can result in improved aging resistance and EMI shielding properties of the gasket.

[0072] In one embodiment, the first composition and the second composition are applied by dispensing, injection molding, extrusion, screen printing, and / or compression molding.

[0073] In one embodiment, the viscosity of the first composition and the viscosity of the second composition are between 20 Pas and 300 Pas.

[0074] To ensure good applicability, it is important that the composition has a low viscosity. At the same time, the viscosity must be high enough to allow the composition to maintain its shape (height and width) after application to the substrate and not flow out before it has time to harden or solidify. The inventors have found that the optimal viscosity that meets the two requirements mentioned above is between 20 Pas and 300 Pas. In one exemplary method, the viscosity of the composition is between 20 Pas and 150 Pas.

[0075] In one embodiment, the viscosity of the first composition is different from the viscosity of the second composition.

[0076] In one embodiment, the viscosity of the first composition is different from the viscosity of the second composition such that the first composition and the second composition remain separate when applied to a substrate.

[0077] By such an exemplary method, a method for making a gasket is provided wherein the first composition and the second composition do not flow into each other during manufacture. It is important that the compositions remain separate so as to form two distinct layers, as each layer will provide specific shielding properties.

[0078] In one embodiment, the applied composition is cured at a temperature above 15 degrees Celsius, preferably between 120 degrees Celsius and 250 degrees Celsius for a period of at least 1 minute to 30 minutes, or at a temperature between 15 degrees Celsius and 60 degrees Celsius for a period of at least 6 hours.

[0079] By curing the gasket, it is ensured that the gasket has a fixed shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0081] Figure 1 A gasket according to the present disclosure is shown applied to a substrate.

[0082] Figure 2 Two substrates are shown joined by a gasket according to the present disclosure.

[0083] Figure 3 A method for manufacturing a gasket according to the present disclosure is schematically illustrated. DETAILED DESCRIPTION

[0084] The detailed descriptions made with reference to the disclosed embodiments should be considered examples of combinations of the specific features described above. It should be understood that additional examples can be realized by combining features other than those in the disclosed embodiments and / or by combining fewer or more features than in the disclosed embodiments. Thus, the figures disclose exemplary embodiments, not exclusive combinations. In this context, it should also be noted that, for simplicity, all figures are disclosed by way of illustration unless otherwise indicated.

[0085] As used herein, "wt-%" refers to the weight percent of the indicated ingredient based on the total weight of the indicated part, compound, or composition.

[0086] The present disclosure relates to a gasket for electromagnetic shielding, comprising at least two layers, wherein the electrical resistance of the first layer is lower than the electrical resistance of the second layer, and wherein the magnetic permeability of the second layer is higher than the magnetic permeability of the first layer.

[0087] Figure 1 A partial cross-sectional view of a gasket 100 according to the present disclosure is shown. Figure 1 The illustrated gasket 100 is arranged on a substrate 3. The gasket 100 includes a first gasket layer 1 and a second gasket layer 2. The first gasket layer 1 includes a first carrier material 11 and a first type of conductive particles 12 within its structure. The first type of conductive particles 12 are electrically conductive particles. The gasket further includes a second gasket layer 2, which includes a second carrier material 21 and a second type of conductive particles 22 within its structure. The second type of conductive particles 22 are electrically conductive particles.

[0088] The first and second gasket layers 1 and 2 each include a sufficient amount of conductive particles to conduct electric current. The first and second conductive particles 12 and 22 are selected such that the resulting resistance value R1 of the first gasket layer 1 is lower than the resulting resistance value R2 of the second gasket layer 2. Thus, because both layers include conductive particles, each of the first and second gasket layers 1 and 2 is capable of conducting electric current. However, the first gasket layer 1 is more capable of conducting electric current. Preferably, the ratio between R1 and R2 is less than 0.5.

[0089] The first type of conductive particles 12 and the second type of conductive particles 22 are further selected so that the resulting magnetic permeability value P1 of the first shim layer 1 is lower than the resulting magnetic permeability value P2 of the second shim layer 2. Thus, the first shim layer 1 exhibits lower magnetic properties than the second shim layer 2. Therefore, when shielding EMI, the first shim layer 1 is better at reflecting EMI, while the second shim layer 2 is better at absorbing EMI.

[0090] The first conductive particles 12 may be selected from silver, copper, gold and / or aluminum.

[0091] The second conductive particles 22 may be selected from nickel, ferrite, iron and / or cobalt.

[0092] exist Figure 1 In the embodiment shown, the spacer 100 is in the form of a longitudinally extending rectangle. However, the spacer 100 may also be in the form of, for example, a triangular tapered shape or a D-shape.

[0093] Further, in Figure 1 In the embodiment shown, the first layer 1 is applied on top of the second layer 2. However, in Figure 1 In another embodiment not shown in FIG, the first layer may be applied immediately adjacent to the second layer.

[0094] Now go to Figure 2 , which shows two substrates 30a and 30b joined by a gasket 100 according to the present disclosure. Because the first and second gasket layers 1 and 2 forming gasket 100 are capable of conducting electrical current, gasket 100 ensures good electrical conductivity between substrates 30a and 30b, thereby creating a Faraday cage. Furthermore, due to the electromagnetic shielding properties of gasket 100, it also reduces the amount of electromagnetic waves (EMI) that can travel through the seal formed by gasket 100.

[0095] exist Figure 2 , electromagnetic waves EMI are shown as EMI emission sources originating from the first gasket layer 1 positioned toward the gasket 100. Since the first gasket layer 1 and the second gasket layer 2 include different kinds of conductive particles 12 and 22, the electromagnetic waves EMI will experience different EMI shielding mechanisms when interacting with the gasket 100.

[0096] As previously explained, the first gasket layer 1 acts as an EMI reflective barrier due to its lower resistance value R1 and lower magnetic permeability value P1 , and the second gasket layer 2 acts as an EMI absorbing layer due to its higher magnetic permeability value P2 .

[0097] Therefore, the gasket 100 can be oriented depending on the location of the main source of EMI to be shielded. Preferably, the first gasket layer 1 is oriented so that the electromagnetic waves EMI to be shielded interact with the first gasket layer 1 first.

[0098] Furthermore, the aging resistance of the gasket 100 can be improved by any of the following means: orienting the gasket 100 so that the layer including the conductive particles with the best aging resistance is exposed to an open external environment, while the layer including the conductive particles with poor aging resistance is exposed to a sealed environment; or further including an additional anti-intrusion (IP) layer to protect the first layer and / or the second layer.

[0099] Now go to Figure 3, schematically shows the method steps performed when manufacturing the gasket 100 according to the present disclosure. In the first step 101, a first composition including a first viscous material and a first type of conductive particles is provided. In the second step 102, a second composition including a second viscous material and a second type of conductive particles is provided.

[0100] The first composition and the second composition are applied to a substrate in a third step 103. The first composition and the second composition can be applied by dispensing, injection molding, extrusion, screen printing, and / or die pressing. The first composition can be applied to the substrate as a first layer, and the second composition can be applied to the substrate as a second layer, thereby forming a multi-layer structure.

[0101] Preferably, the first composition and the second composition are applied to the substrate simultaneously.

[0102] In a fourth step 104, the applied compositions are cured. After curing, the first composition has a first resistance value R1 and a first magnetic permeability value P1, and wherein, the cured second composition has a second resistance value R2 and a second magnetic permeability value P2. The relationship among R1, R2, P1, and P2 is R1 < R2 and P2 > P1.

[0103] Examples

[0104] In the following examples, 4 different gaskets were analyzed. These gaskets included different compositions, and the resulting electromagnetic shielding characteristics and resistances were evaluated.

[0105] Materials:

[0106] Composition A: 20 wt% to 50 wt% of fluid silicone rubber and 50 wt% to 80 wt% of nickel particles

[0107] Composition B: 20 wt% to 50 wt% of fluid silicone rubber and 50 wt% to 80 wt% of silver particles

[0108] 4 gaskets were manufactured. Gasket G1 includes a single layer of Composition A. Gasket G2 includes a single layer of Composition B. Gaskets G3 and G4 are multi-layer gaskets including a first layer of Composition A and a second layer of Composition B. All gaskets G1 to G4 were manufactured by extrusion.

[0109] Gasket G1 has a resistance of 60 milliohms (mOmh), and gasket G2 has a resistance of 17 mOhm. The resistance was measured by placing the gasket on a conductive surface. A 10X10 mm square electrode was applied to the gasket with a force of 6.5 N. The resistance was measured in mΩ.

[0110] The electromagnetic shielding characteristics of gaskets G1 to G4 are tested. The test equipment has a grooved aluminum bottom plate and an aluminum top plate to encapsulate and compress the gasket placed in the groove. For each test, the gasket is placed in the groove and encapsulated with the top plate. The compression ratio of the gasket is 35%. 2 mm of the height of the gasket is exposed to the signal. Two cavities are located on opposite sides of the groove.

[0111] A short - circuit probe is assembled in each cavity. A network analyzer is connected and used to feed a signal into one cavity and measure the EMI inside the other cavity. The shielding effectiveness of the gasket is measured in dB as the S21 response in the frequency range from 0.3 GHz to 20 GHz. The results of each gasket G1 to G4 are shown in Table 1. For gaskets G3 to G4, the gaskets are oriented such that the layer comprising composition B faces the EMI - emitting probe (inner layer), and the layer comprising composition A faces away from the EMI - emitting probe (outer layer).

[0112] The tests are carried out using unaged gaskets (t0) and gaskets aged for 400 hours (t1) and 1000 hours (t2).

[0113]

[0114] It can be seen that, compared with the single - layer gaskets G1 and G2, the multi - layer gaskets G3 and G4 with an inner layer comprising silver particles facing the EMI - emitting source have improved shielding characteristics and improved aging resistance. As previously explained, it is believed that silver acts as a protective layer for the inner layer and reflects EMI.

[0115] In various exemplary embodiments of a gasket 100 for electromagnetic shielding, the gasket 100 comprises: a first gasket layer 1, which comprises a composition of a first carrier material 11 and a first type of conductive particles 12, wherein the first gasket layer 1 has a first resistance value R1 and a first permeability value P1; a second gasket layer 2, which comprises a composition of a second carrier material 21 and a second type of conductive particles 22, wherein the second layer 2 has a second resistance value R2 and a second permeability value P2; wherein, R1 < R2 and P2 > P1, and wherein the first carrier material and the second carrier material are each independently selected from at least one of silicone rubber and / or thermosetting polymers. The first gasket layer 1 and the second gasket layer 2 form the gasket 100 here. In other exemplary embodiments, additional gasket layers may be present.

Claims

1. A gasket (100) for electromagnetic shielding, wherein: The gasket (100) comprises: a) A first gasket layer (1), comprising a composition of a first carrier material (11) and a first type of conductive particles (12), wherein the first layer (1) has a first resistance value R1 and a first magnetic permeability value P1; b) A second gasket layer (2), comprising a composition of a second carrier material (21) and a second type of conductive particles (22), wherein the second layer (2) has a second resistance value R2 and a second magnetic permeability value P2; wherein R1 < R2 and P2 > P1, and wherein the first carrier material and the second carrier material are each independently selected from at least one of silicone rubber and / or thermosetting polymer.

2. The gasket (100) according to claim 1, wherein The ratio between the first resistance value R1 and the second resistance value R2 is less than 0.5, more preferably less than 0.

4.

3. The gasket (100) according to any one of claims 1 to 2, wherein: The first gasket layer (1) is configured to receive direct electromagnetic interference, and the second gasket layer (2) is configured to receive electromagnetic interference that has passed through the first layer (1).

4. The gasket (100) according to any one of claims 1 to 3, wherein: The first gasket layer (1) has a resistance value R1 less than 4 ohms, and the second gasket layer (2) has a resistance value R2 less than 10 ohms.

5. The gasket (100) according to any one of claims 1 to 4, wherein The gasket further comprises one or more additional layers, the one or more additional layers comprising a carrier material and conductive particles.

6. The gasket (100) according to any one of claims 1 to 5, wherein: The gasket further comprises an intrusion prevention (IP) layer, preferably, the IP layer is selected from silicone rubber and / or thermosetting polymer.

7. The gasket (100) according to any one of claims 1 to 6, wherein Both the first type of conductive particles (12) and the second type of conductive particles (22) are metal particles.

8. The gasket (100) according to any one of claims 1 to 7, wherein The first layer (l) comprises conductive particles, the conductive particles comprising silver, copper, gold, and / or aluminum.

9. The gasket (100) according to any one of claims 1 to 8, wherein The second layer (2) comprises conductive particles, the conductive particles comprising nickel, ferrite, iron, and / or cobalt.

10. The gasket (100) for electromagnetic shielding according to any one of claims 1 to 9, wherein: The ratio between the thickness of the first layer and the thickness of the second layer is between 1:20 and 20:1, preferably between 1:1 and 1:

4.

11. The gasket (100) for electromagnetic shielding according to any one of claims 1 to 10, wherein: The first gasket layer and the second gasket layer each comprise 30% to 95% by weight of conductive particles.

12. A method for manufacturing a gasket for electromagnetic shielding, wherein: The method comprises the following steps: i) Providing a first composition comprising a first adhesive material and a first type of conductive particles; ii) Providing a second composition comprising a second adhesive material and a second type of conductive particles; iii) Applying the first composition as a first gasket layer and the second composition as a second gasket layer to a substrate by applying the first composition and the second composition in the form of a multi-layer gasket; iv) Optionally applying an additional composition comprising an adhesive material and / or conductive particles; v) Curing the applied compositions, thereby forming a multi-layer gasket, wherein the cured first gasket layer has a first resistance value R1 and a first magnetic permeability value P1, and wherein the cured second gasket layer has a second resistance value R2 and a second magnetic permeability value P2; and wherein R1 < R2 and P2 > P1, and wherein the adhesive material is silicone rubber and / or thermosetting polymer.

13. The method according to claim 12, wherein: The ratio between the first resistance value and the second resistance value is less than 0.5, more preferably less than 0.

4.

14. The method according to any one of claims 12 to 13, wherein Step iii) comprises applying the first composition and the second composition to the substrate simultaneously.

15. The method according to any one of claims 12 to 14, wherein The first composition is applied to receive direct electromagnetic interference, and the second composition is applied to receive electromagnetic interference that has passed through the first composition.

16. The method according to any one of claims 12 to 15, wherein The first composition and the second composition are applied by dispensing, injection molding, extrusion, screen printing and / or compression molding.

17. The method according to any one of claims 12 to 16, wherein The viscosity of the first composition and the viscosity of the second composition are both between 20 Pas and 300 Pas.

18. The method according to any one of claims 12 to 17, wherein The viscosity of the first composition is different from the viscosity of the second composition such that the first composition and the second composition remain separate.

19. The method according to any one of claims 12 to 18, wherein The applied composition is cured at temperatures above 15 degrees Celsius, preferably between 120 degrees Celsius and 250 degrees Celsius for a period of at least 1 minute to 30 minutes, or at temperatures between 15 degrees Celsius and 60 degrees Celsius for a period of at least 6 hours.

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