Molded part for a mobile terminal device with transmitter and / or receiver made of carbon fiber reinforced plastic

Description

[0001] The invention relates to a molded part for a mobile terminal with a transmitting and / or receiving device made of carbon fiber reinforced plastic.

[0002] To manufacture mobile devices with transmitting and / or receiving devices, such as mobile phones or tablet computers, it is common practice to produce the housing of the mobile device from carbon fiber reinforced plastic. The carbon fiber reinforced plastic has similar strength values ​​to current molded parts made of aluminum / magnesium cast. A special feature of carbon fiber reinforced plastic is that it can absorb impacts, as sometimes happens when a device is dropped from hand height, with the absorbed kinetic energy being dissipated in the carbon fiber composite and not passed on to other components. Another advantage of housings made of carbon fiber reinforced plastic is its low weight. Current mobile phones, which are known asSmartphones, as they are known, often weigh 200 g or more, which, when carried in the inside pocket of a suit jacket, leads to undesirable distortion of the suit. The one-sided weight of the smartphone is also perceived as distracting. With the expected arrival of clamshell smartphones—i.e., smartphones with foldable displays—the weight will increase considerably, because each molded part weighs approximately the same as a single smartphone today.

[0003] International patent application WO 2017 / 202751 A1 discloses polycarbonate compositions containing fillers, a carboxylic acid, and its glycerol or diglycerol esters, wherein the fillers are carbon fibers. Such a composite material is presented for use in constructing a thin-walled application such as so-called ultrabooks or smartphones. Furthermore, document US2015 / 0024811 A1 discloses an electronic device with a cover element made of fiber-reinforced plastic, and document KR20140004336A discloses a mobile terminal in which an inlay antenna is formed with a rear cover of the mobile terminal to achieve a low antenna thickness.

[0004] Typically, applications of carbon fiber composites are characterized by their mechanical properties and their weight. A rather fashionable side effect of carbon fiber composites is the visibility of the carbon fiber fabric.

[0005] The use of carbon fiber composites has a surprising side effect. Due to the high electrical conductivity of carbon fibers, the casing wall for a mobile phone, tablet computer, or smartphone acts like a Faraday cage. This effect is more pronounced the more directions the carbon fiber filaments are regularly arranged. There are unidirectional

[0006] Carbon fiber composites, often referred to as UD composites. With unidirectional fabrics, the Faraday cage effect is less pronounced, and the shielding depends heavily on the direction of the fabric in relation to the orientation of the antenna within the mobile device. Other influencing factors are the frequency of the electromagnetic radiation and the propagation of the electromagnetic radiation as a dipole antenna. Even with a bidirectional fabric or a multi-layer fabric with different filament directions, the Faraday cage effect increases significantly. In fabrics with just a few filaments, around 1,000 per strand, the shielding effect is so strong that transmission and reception is no longer possible. Compared to other plastic composite materials, carbon fiber composites have the advantage of providing strong shielding against electromagnetic radiation from the mobile phone.The shielding performance or attenuation of electromagnetic radiation is comparable to the attenuation of a housing made of aluminum and / or magnesium.

[0007] To operate a transmitting and receiving antenna in a mobile device, it is common practice for aluminum and / or magnesium housings to galvanically isolate one edge of the housing from the rest of the housing. The galvanically isolated edge serves as an antenna for the mobile device's transmitting and receiving signals. Such galvanic isolation of an edge of a mobile device is externally recognizable by apparent design stripes. In reality, however, the strips are made of plastic or glass to provide the galvanic isolation.

[0008] A comparable construction of a housing made of carbon-reinforced plastic is not possible.

[0009] The object of the invention is therefore to provide a molded part for mobile devices made of carbon fiber-reinforced plastic, which enables the operation of a transmitting and receiving antenna within the mobile device. The object of the invention is achieved by forming an antenna window as a recess into which an insert antenna is inserted, which is connected to the molded part via an electrical insulation body, wherein the insert antenna protrudes from the molded part. Further advantageous embodiments are specified in the subclaims to claim 1.

[0010] According to the concept of the invention, unlike conventional molded parts for transmitting mobile devices, an antenna window is incorporated into the molded part. The molded part thus consists of at least two different materials, with the material of the antenna window also advantageously being a fiber composite material. Fiber-reinforced plastics exhibit a pronounced anisotropy with regard to fracture propagation within their structure.To prevent a mechanical shock wave from building up at the connection between the different materials due to an abrupt change in mechanical properties, such as local elastic modulus or shear modulus, in the event of a mechanical impact on the housing of the mobile device, for example, due to a drop, and causing a crack to form at the connection line between the different materials, the antenna window can be made of glass fiber reinforced plastic. The glass fibers can be laid in the same direction as the carbon fibers or woven with the same pattern. Although the mechanical properties of carbon fiber reinforced plastic and glass fiber reinforced plastic differ, the anisotropy of the local mechanical properties of the various fiber-reinforced materials is comparable.A mechanical shock wave propagates more evenly at the transition from one material to the second. If this is designed as an antenna window opening into which an inlay antenna is inserted, the inlay antenna forms the second material of the antenna window.

[0011] To increase the electromagnetic damping of the material in the area of ​​the carbon fiber-reinforced plastic and simultaneously to even out the isotropy of mechanical shock wave propagation, the carbon fiber-reinforced plastic can be designed as a multiaxial carbon fabric. In contrast, the antenna window can be made of glass fiber-reinforced plastic to adjust the shock wave propagation.

[0012] In order to increase the stability in the area of ​​the transition between the carbon fiber reinforced plastic and the antenna window and to reduce the tendency to fracture along the connecting line in the event of an impact, it can be provided that the connection between the carbon fiber reinforced plastic and the antenna window is designed as an undercut, wherein a negative shape of the undercut in the carbon fiber reinforced plastic corresponds to a positive shape of the undercut on the antenna window, and wherein the connection between the carbon fiber reinforced plastic and the antenna window is covered on at least one side with an overmolding.

[0013] The undercut ensures that the different materials interlock tightly. The overmolding, which can be applied to the molded part during the injection molding process, secures the positive connection between the positive mold and the negative mold of the undercut, preventing lateral breakage.

[0014] To further stabilize the connection between the carbon fiber-reinforced plastic and the antenna window, the connection between the carbon fiber-reinforced plastic and the antenna window can be designed as an overlap. For this purpose, the carbon fiber-reinforced plastic can be reduced to approximately half its wall thickness by milling. The antenna window can be formed by applying a prepreg and pressing it under heat, or by applying a thermoplastic and glass fiber-reinforced plastic to the milled surface.

[0015] As an alternative to a window permeable to electromagnetic radiation throughout the entire wall, an antenna window can also be incorporated into one wall of the molded part, extending only approximately halfway through the wall thickness. To utilize the antenna window, an antenna can be incorporated into the window, which has an electrical connection through the carbon fiber-reinforced wall to connect the antenna to electronics located within the molded part.

[0016] In a particular embodiment of the invention, the antenna window can be embedded in the surface of the molded part made of carbon fiber-reinforced plastic, with a coil antenna made of carbon fibers being present within the antenna window. Carbon fibers have a specific electrical conductivity comparable to that of metallic electrical conductivity; in some cases, the conductivity of carbon fibers is even higher. Carbon fibers are typically coated with a thermoplastic material to bond them to the plastic connecting them during heat-pressing. This coating provides good electrical insulation for the individual carbon fibers.If the carbon fibers are laid out in the embedded antenna window like a coil antenna, and the ends of the carbon fibers are passed through the woven or non-woven carbon fiber fabric to reinforce the plastic, the organic carbon antenna can be used like a metallic antenna. The use of an organic carbon fiber antenna has the further advantage that the organic casing is completely transparent to X-rays. This makes it easier to screen mobile phones, smartphones, and tablet computers during routine checks at airports or in other security areas. To construct the molded part, it can be provided that the molded part has a multi-axial carbon fabric (fabric made of carbon fibers) into which a coil is inserted as a coil antenna made of carbon fibers, with the ends of the carbon fibers of the coil antenna being passed through the multi-axial carbon fabric.The multi-layer carbon fabric shields the electronics within the molded part from the transmission power of the antenna.

[0017] In a further, alternative embodiment of the molded part, an inlay antenna can be arranged in the area of ​​the antenna window, which is connected to the molded part by overmolding the carbon fiber-reinforced plastic. According to this optional embodiment of the invention, the molded part is equipped with an inlay antenna, which can transmit and receive through the antenna window.

[0018] The density of the carbon fibers and the density of the mesh of the fabric influence the shielding effect against electromagnetic radiation in the range from 800 MHz to 4 GHz. Fabrics woven with 1,000 fibers per strand, 3,000 fibers per strand, and 12,000 fibers per strand have proven advantageous. Such carbon fiber fabrics are commercially available as 1K (1,000 fibers / filaments), 3K (3,000 fibers / filaments), and 12K (12,000 fibers / filaments). The molded part can be produced by pressing a prepreg in a mold or by hot-forming a thermoplastic and carbon fiber-reinforced plastic, or from fibers already coated with a thermoplastic.

[0019] In a special embodiment of the molded part according to the invention, it can be provided that a side wall of the molded part comprises a metallic high-performance antenna, wherein the material of the antenna window galvanically separates the metallic high-performance antenna from the carbon fiber reinforced plastic.

[0020] The invention is explained in more detail with reference to the following figures. They show: Fig. 1 shows a molded part of a smartphone from the PRIOR ART, here as a one-piece mold of a shell, Fig. 2 shows a molded part according to the invention made of carbon fiber composite material with an embedded antenna window, Fig. 3 shows a representation of a connection between carbon fiber composite material and an inserted antenna window, Fig. 4 shows a molded part according to the invention with an embedded antenna window and a carbon fiber antenna, Fig. 5 shows a section of an enlarged view of the section line AA in Figure 4, Fig. 6 a view of the inside of another alternative embodiment of a molded part according to the invention with a left-out antenna window, Fig. 7 an insert antenna, Fig. 8 the insert antenna from Figure 7 in a perspective view, Fig. 9 a view of the inside of the molded part according to the invention from Figure 6 with an insert antenna molded by overmolding, Fig. 10 a view of the outside of the molded part according to the invention from Figure 6 with an insert antenna molded in by overmolding, Fig. 11 a detail of the side wall of the molded part according to the invention with an undercut, Fig. 12 the detail from Figure 10 , in which the undercut has been avoided by overmolding, Fig. 13 a further embodiment of the molded part according to the invention made of carbon fiber composite material with an inserted antenna window and a high-performance antenna.

[0021] In Figure 1A molded part of a smartphone casing from the prior art is shown. The molded part has a monocoque structure, meaning it is single-shell and has only a single wall material. The molded part was produced by the well-known method of pressing a prepreg in a mold. Prepregs are fabric mats impregnated with a partially polymerized plastic. The partially polymerized plastic is epoxy resin or a vinyl ester. These are flexible when cold and can be laid in a mold. During hot pressing in a mold, the connecting plastic polymerizes, forming a solid shape with a generally thin wall.

[0022] In Figure 2A molded part 100 according to the invention for use in a smartphone or a tablet computer is shown. This molded part 100 consists of two materials. The predominant portion of the molded part consists of carbon fiber-reinforced plastic 101, which has been produced in a known manner by pressing a prepreg with epoxy resin, with melamine resin, or with a vinyl ester resin. Thermoplastic materials are also used, with the individual carbon fibers being coated with a thermoplastic material. The carbon fiber-reinforced molded part is only formed when the fabric is pressed in a mold under heat, with the coatings of adjacent carbon fibers fusing together. In this inventive embodiment of the molded part, it is provided that an antenna window 102 comprising the entire wall thickness is introduced into the molded part 100. The antenna window 102 can, for example, be made of glass fiber-reinforced epoxy resin.The antenna window 102 is preferably located at one end of a vertical housing. This is where an antenna for transmitting and receiving radio waves for communication with remote transmission and reception masts is located in known smartphones, mobile phones, and / or tablet computers. To match the local mechanical properties of the carbon fiber-reinforced plastic 101 and the glass fiber-reinforced epoxy resin of the antenna window 102, the orientation of the fabric fibers of both plastics can be synchronized.

[0023] In Figure 3 is a connection between the carbon fiber reinforced plastic 101 and the antenna window 102 in Figure 2shown along the connecting edge between the carbon fiber reinforced plastic 101 and the antenna window 102. In this embodiment, the carbon fiber reinforced plastic 101 consists of three layers A, B and C, which are equipped with carbon fiber fabrics of different bidirectional mesh densities. The different layers A, B and C are connected to one another via a thermoplastic material TP. The innermost layer A consists, for example, of a carbon fiber reinforced plastic with a carbon fiber fabric with 12,000 carbon fibers per woven strand, a so-called 12K fabric. The middle layer B consists, for example, of a carbon fiber reinforced plastic with a carbon fiber fabric with 3,000 carbon fibers, a so-called 3K fabric, and the outermost layer C consists, for example, of a carbon fiber reinforced plastic with a carbon fiber fabric with 1.000 carbon fibers per woven strand, a so-called 1K fabric. To connect the carbon fiber-reinforced plastic 101 to the antenna window 102, which in this example consists of a glass fiber-reinforced plastic, the molded part is removed in the area of ​​the edge of the carbon fiber-reinforced plastic 101 to such an extent that the layer thickness corresponds to only approximately half the total wall thickness of the molded part 100, although a portion of the thermoplastic material TP connecting layers A and B remains. This thermoplastic material TP connecting layers A and B serves as the connecting surface between the carbon fiber-reinforced plastic and the glass fiber-reinforced plastic of the antenna window 102. In this example, a glass fiber-reinforced plastic rests on the tongue of the carbon fiber-reinforced plastic 101 that is approximately half the wall thickness.This has individual undercuts 104 that protrude like pegs from the glass-fiber-reinforced plastic of the antenna window 102 and, when a prepreg is pressed, mold into corresponding and milled negative molds of the undercuts 104. When the prepreg of the glass-fiber-reinforced plastic for the antenna window 102 is pressed, the epoxy resin of the glass-fiber-reinforced plastic of the antenna window 102 bonds with the carbon-fiber-reinforced plastic 101 of the molded part. To prevent the undercuts from breaking out of the negative molds, an overmolding 103 is provided, which is applied to the connecting edge of the two different materials by an injection molding system during the pressing process.

[0024] In Figure 4An alternative embodiment of the molded part according to the invention is shown as a molded part 200. In this molded part, an antenna window 202 is embedded in the surface of the carbon fiber reinforced plastic 101. The layer that does not shield against electromagnetic radiation is only about half as thick as the wall thickness of the molded part 200. The antenna window 202 in this case has an embedded antenna 300, which can also be made of carbon fibers. In the case of the carbon fiber antenna, the ends of the individual fibers are passed through the fabric of the carbon fiber reinforced plastic 101 so that the ends can be connected to corresponding control electronics. To clarify the position of the embedded antenna 300, Figure 5 a view of the section line AA in Figure 4shown. The antenna 300, which may consist of individual carbon fibers, is embedded in the antenna window 202, with the antenna window 202 itself being embedded in the carbon fiber-reinforced plastic 101. The embedding can be achieved by simply combining a prepreg for pressing the carbon fiber-reinforced plastic 101 and an antenna 300. During the pressing of the combined prepregs, the plastic portion of the prepregs of the carbon fiber-reinforced plastic 101 and the antenna 300 wraps around the individual carbon fibers in a correspondingly shaping manner.

[0025] In Figure 6A view of the inside of yet another embodiment of the molded part according to the invention is shown as a molded part 400. The molded part 400 has an antenna window 402, which is itself formed as a recess in the molded part 400. This recess serves to accommodate an insert antenna 500, which is firmly connected to the molded part 400 by overmolding. For this purpose, the insert antenna 500 is placed in the region of the antenna window 402 and connected to the antenna window 402 and the carbon fiber-reinforced plastic 401 by overmolding in an injection mold. The insert antenna 500 protrudes from the molded part 400.

[0026] In Figure 7 The insert antenna 500 is shown in a top view. From above, an electrical connection 501 and an electrical insulation body 502 for receiving the insert antenna 500 and for electrical insulation from the molded part 400 are visible. The same insert antenna 500 is shown in Figure 8shown in perspective, with the perspective view revealing the bulky shape of the insulating body 502. The insert antenna 500 shown here is shown together with the electrical insulating body 502. In fact, the insert antenna 500 is connected to the molded body 400 by overmolding with plastic in the mold, with the electrical insulating body 502 being formed during the overmolding.

[0027] In Figure 8 the antenna is on Figure 7 shown in a perspective view. This insert antenna 500 is inserted with the narrower side into the recess of the antenna window 402 and connected to the molded part 400 by overmolding. The insulating body 502 is formed in the process.

[0028] In Figure 9 a view of the inside of the molded part 400 according to the invention from Figure 6with an overmolded insert antenna 500. The electrical insulation body 502 insulates the insert antenna 500 from the molded part 400. In this view, the insert antenna 500 is shown in dashed lines because the electrical insulation body 502 covers the insert antenna 500.

[0029] In Figure 10 a view of the outside of the molded part 400 according to the invention from Figure 6 with an overmolded insert antenna 500. The electrical insulation body 502 insulates the insert antenna 500 from the molded part 400.

[0030] In Figure 11A section through the molded part 100 according to the invention is shown in the region of a side wall 110. The carbon fiber reinforced plastic 101 is hot-pressed in a mold. In order to connect the surface of the molded part flush with a display 111, it is necessary for the display to be located in a frame 112. This frame 112 can best be formed by a folded wall of the side wall 110 of the molded part, as shown in Figure 10 is shown.

[0031] To avoid the formation of an undercut in the mold, which requires a complex shape for demolding, a border 112' is injected into the edge of the molded part as an overmolding 105. The border 112' rests against the inner wall of the molded part and forms a border 105' for a display 111 in the area of ​​the upper edge of the side wall 110, as shown in Figure 12is shown. The 112' enclosure allows the top edge of the side wall 110 to be pressed into a mold without undercutting and can be easily demolded.

[0032] In Figure 13A further embodiment of the molded part 600 according to the invention made of carbon fiber composite material is shown, with an inserted antenna window 602 and a high-performance antenna 603. The high-performance antenna 603 can be constructed of metal and can receive signals for communication between the mobile device and a remote transmission tower. In order to galvanically separate the high-performance antenna 603 from the electrically conductive, carbon fiber-reinforced plastic, the material of the antenna window 602 accommodates and encloses the high-performance antenna 603 in a side wall of the molded part. In this example, the antenna window 602 serves for less powerful transmitting and receiving antennas, such as RFID antennas and antennas for near-field and mid-field communication.

[0033] In Figure 14 the molded part 100 from Figure 2, wherein a circuit board 106 is arranged in the molded part 100, which is connected to an antenna 107. The antenna 107 is arranged in the region of the antenna window 102, so that the antenna 107 can transmit and receive without shielding. LIST OF REFERENCE SYMBOLS

[0034] 100 molded part 400 molded part 101 carbon fiber reinforced plastic 401 carbon fiber reinforced plastic 102 Antenna window 402 Antenna window 103 Overspray 404 electrical connection 104 undercut 105 Overspray 500 Insert antenna 105' frame 501 electrical connection 106 circuit board 502 electrical insulation body 107 antenna 110 side wall 600 molded part 111 Display 601 carbon fiber reinforced plastic 112 frame 112' frame 602 Antenna window 603 High-performance antenna 200 molded part 604 side wall 201 carbon fiber reinforced plastic A layer 202 Antenna window TP thermoplastic material 300 Coil antenna B layer C layer

Claims

1. Shaped part (400) for a mobile device having a transmitting and / or receiving device, said shaped part being composed of carbon-fiber-reinforced plastic (101, 401), characterized in that an antenna window (402) is designed as an omission into which an insertion antenna (500) is inserted, said insertion antenna being connected to the shaped part (400) via an electrical insulating body (502), wherein the insertion antenna (500) projects out of the shaped part (400).

2. Shaped part according to claim 1, characterized in that the carbon-fiber-reinforced plastic (101) is designed as a multiaxial carbon fabric.

3. Shaped part according to claim 1 or 2, characterized in that the antenna window (102) consists of glass-fiber-reinforced plastic.

4. Shaped part according to one of claims 1 to 3, characterized in that the connection between the carbon-fiber-reinforced plastic (101) and the antenna window (102) is designed as an undercut (104), wherein a negative shape of the undercut (104) in the carbon-fiber-reinforced plastic (101) corresponds to a positive shape on the antenna window (102), and wherein the connection between the carbon-fiber-reinforced plastic (101) and the antenna window (102) is covered on at least one side by an overmolding (103).

5. Shaped part according to claim 4, characterized in that the connection between the carbon-fiber-reinforced plastic (101) and the antenna window (102) is designed as an overlap.

6. Shaped part according to claim 1, characterized in that the antenna window (202) is embedded into the surface of the shaped part composed of carbon-fiber-reinforced plastic (101), wherein a coil antenna (300) composed of carbon fibers is present within the antenna window (102).

7. Shaped part according to claim 6, characterized in that the shaped part (100) has a multiaxial carbon fabric, into which a coil of a coil antenna (300), composed of carbon fibers, is inlaid, wherein the ends of the carbon fibers of the coil antenna (300), composed of carbon fibers, are guided through the multiaxial carbon fiber.

8. Shaped part according to one of claims 1 to 7, characterized in that an insertion antenna (500) is arranged in a recess of the shaped part in the area of the antenna window (402) and said insertion antenna is connected to the shaped part (400) by the overmolding of the carbon-fiber-reinforced plastic (401).

9. Shaped part according to one of claims 1 to 8, characterized in that the carbon-fiber-reinforced plastic (101) consists of more than one layer (A, B, C), preferably consists of between 2 and 10 layers, particularly preferably consists of three layers, in which the carbon fibers are woven together using a linen weave with 1,000, 3,000, or 12,000 filaments per bundle and adjacent layers have different numbers of filaments per bundle.

10. Shaped part according to one of claims 1 to 8, characterized in that the carbon-fiber-reinforced plastic (101) is produced from a prepreg or from filaments coated with thermoplastic material.

11. Shaped part according to one of claims 1 to 8, characterized in that a side wall (604) of the shaped part (600) comprises a metallic high-performance antenna (603), wherein the material of the antenna window (602) electrically isolates the metallic high-performance antenna (603) from the carbon-fiber-reinforced plastic (601).