Patent Publication Number: US-2012033931-A1

Title: Waveguide

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of PCT International Application No. PCT/JP2010/055905 filed Mar. 31, 2010, which claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2009-099970, filed Apr. 16, 2009. 
    
    
     FIELD OF INVENTION 
     The present invention relates to a waveguide and in particular to a resin waveguide having a metal plating layer. 
     BACKGROUND 
     Generally, there are known resin waveguides made of a metal tube and known resin waveguides formed by plating an internal surface of a tube made of resin with metal used for transmitting radio waves such as microwaves and millimeter waves, 
     The transmission of radio waves by waveguides has advantages in that transmission loss is less than in the transmission of radio waves through a wire such as a shielding wire. Additionally, a transmission loss does not increase depending on a transmission distance, and moreover, there is no influence by external electrical noise. 
     Also, a resin waveguide having a polycarbonate resin as a covering layer, an ABS resin as an adherent layer (internal layer), and a metal plating on an inner surface of the adherent layer (internal layer) has been disclosed. 
     Although metal waveguides may be prepared in various way, for example, by bending, weight reduction of a device in which the waveguide is incorporated is hindered because it is made of metal, and a short circuit due to contact with other electrical components is likely to occur. 
     In contrast, the known resin waveguide contributes to weight reduction of a device in which the waveguide is incorporated, and a short circuit due to contact with other electrical components is unlikely to occur. 
     However, the known resin waveguide is generally formed using a molding die, by pulling the molding die along a longitudinal direction. As a result, the shape of the resin waveguide is limited to a linear shape that can be pulled from the molding die. Therefore, a waveguide that needs to have a U-shaped transmission path as a whole such as a waveguide in which both a transmitting section and a receiving section face in a same direction may not be formed by the known technique. 
     In a millimeter-wave waveguide used when transmitting millimeter waves, the diameter of a transmission path needs to be small. In a case where the known technique is applied to the millimeter-wave waveguide of such a small diameter, a problem may occur, wherein clogging of the transmission path due to plating accumulation occurs when an inner surface of a resin tube (namely, an inner wall of the transmission path) is subjected to metal plating. 
     Also, as for the known resin waveguide, in a plating process in which the inner surface of the tube made of resin is subjected to the metal plating, the greater the length of the waveguide in the longitudinal direction is, the higher the probability of uneven plating occur. Additionally, it is difficult to form an even metal plating layer in the waveguide made of resin that is long in the longitudinal direction. 
     Further, in the known resin waveguide process, the metal plating layer is formed along the inner surface of the known resin waveguide and thus, the metal plating layer may not be visually checked. Therefore, even when, for example, a defect such as a so-called “plating missing” in which plating does not adhere to a resin in a plating process occurs, this defect may be overlooked. 
     SUMMARY 
     In view of the foregoing circumstances, it is an object of the invention, among other objects, to provide a waveguide made of resin in which an even metal plating layer may be formed irrespective of the length in a longitudinal direction and the diameter of a transmission path, such that the formed metal plating layer may be easily inspected. 
     A waveguide according to the invention has a main body, an inner housing, and a wave receiving transmission path. The main body includes a body resin member, a concave groove extending in a longitudinal direction and a body metal plating layer over an entire surface of the concave groove. The inner housing has a resin cover member and an inner housing metal plating layer along an inner wall of the inner housing. The wave receiving transmission path is formed when the inner housing covers the concave groove of the main body when the main body and cover are assembled together. 
     According to the present invention, there is provided a waveguide made of resin which may support various shapes, in which an even metal plating layer may be formed irrespective of the length in a longitudinal length and the diameter of a transmission path, and in which the formed metal plating layer is readily checked. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features of the present invention will become more apparent by describing in detail embodiments thereof with reference to the accompanying drawings, in which: 
         FIG. 1  is a front perspective view of a waveguide according to the invention with a millimeter-wave module; 
         FIG. 2  is a front perspective view of the waveguide and the millimeter-wave module shown in  FIG. 1  before they are combined with each other; 
         FIG. 3  is an exploded perspective view of the waveguide with a main body and an inner housing are separated from each other; 
         FIG. 4  is a longitudinal sectional diagram taken along lines  4 - 4  shown in  FIG. 3 ; 
         FIG. 5   a  is a plan view of the main body shown in  FIG. 3 ; 
         FIG. 5   b  is a front view of the main body shown in  FIG. 3 ; 
         FIG. 5   c  is a left side view of the main body shown in  FIG. 3 ; 
         FIG. 5   d  is a right side view of the main body shown in  FIG. 3 ; 
         FIG. 5   e  is a bottom view of the main body shown in  FIG. 3 ; 
         FIG. 6   a  is a plan view of the inner housing shown in  FIG. 3 ; 
         FIG. 6   b  is a front view of the inner housing shown in  FIG. 3 ; 
         FIG. 6   c  is a left side view of the inner housing shown in  FIG. 3 ; 
         FIG. 6   d  is a right side view of the inner housing shown in  FIG. 3 ; 
         FIG. 6   e  is a bottom view of the inner housing shown in  FIG. 3 ; 
         FIG. 7  is an exploded perspective view of another embodiment of a waveguide according to the invention, with a main body and an inner housing are separated from each other; 
         FIG. 8  is a longitudinal sectional diagram taken along a line  8 - 8  shown in  FIG. 7 ; 
         FIG. 9  is a longitudinal sectional diagram taken along a line  9 - 9  shown in  FIG. 7 ; 
         FIG. 10   a  is a plan view of the main body shown in  FIG. 7 ; 
         FIG. 10   b  is a front view of the main body shown in  FIG. 7 ; 
         FIG. 10   c  is a left side view of the main body shown in  FIG. 7 ; 
         FIG. 10   d  is a right side view of the main body shown in  FIG. 7 ; 
         FIG. 10   e  is a bottom view of the main body shown in  FIG. 7 ; 
         FIG. 11   a  is a plan view of the inner housing shown in  FIG. 7 ; 
         FIG. 11   b  is a front view of the inner housing shown in  FIG. 7 ; 
         FIG. 11   c  is a left side view of the inner housing shown in  FIG. 7 ; 
         FIG. 11   d  is a right side view of the inner housing shown in  FIG. 7 ; and 
         FIG. 11   e  is a bottom view of the inner housing shown in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of the present invention will be described with reference to the drawings. 
       FIG. 1  shows a waveguide  100  according to the invention combined with a millimeter-wave module  300 , as viewed obliquely from above, while  FIG. 2  shows the waveguide  100  and the millimeter-wave module  300  before they are combined with each other. The millimeter-wave module  300  is, for example, provided in a display panel of a liquid crystal display television (not illustrated). The millimeter-wave module  300  includes a transmitting-side module  310  having a millimeter-wave antenna  311 , and a receiving-side module  320  having a millimeter-wave antenna  321 . And, the waveguide  100  is a waveguide for millimeter waves which is used for millimeter wave communication of 60 GHz, and links the millimeter-wave antenna  311  of the transmitting-side module  310  and the millimeter-wave antenna  321  of the receiving-side module  320 . Also, this waveguide  100  extends in an arrow-A direction which is a longitudinal direction, and has a cross section shaped like a rectangle. 
     It is to be noted that the display panel of the liquid crystal display television which is an object to be provided with the millimeter-wave module  300  is merely an example, and the object may be, for example, a personal computer, a gaming machine, a video recorder, a digital camera, an access point, or the like. 
     As illustrated in  FIG. 3 , the waveguide  100  is a hollow waveguide made of resin, and includes a main body  110  and an inner housing  120 , and has a metal plating layer  130  on an inner surface of a tube made of resin (namely, an inner wall of a transmission path). 
     The main body  110  shown in  FIG. 3  to  FIG. 5  is formed by two shot molding of an ABS resin to form an internal layer  111  by adhering to the metal plating layer  130 , and a polycarbonate resin to form an external layer  112  by adhering to the ABS resin without adhering to the metal plating layer  130 . The ABS resin is an example of the first resin according to the invention, and the polycarbonate resin is an example of the second resin according to the present invention. Further, a concave groove  113  is formed in the main body  110 , in an inner part, excluding both end portions  110   a  and  110   b  of the main body  110  in the arrow-A direction and inside these both end portions  110   a  and  110   b , and extending in the arrow-A direction. Furthermore, the main body  110  has the metal plating layer  130  over the entire surface of the concave groove  113 . 
     Similarly to the main body  110 , the inner housing  120  shown in  FIG. 3 ,  FIG. 4  and  FIG. 6  is formed by two shot molding of an ABS resin to form an internal layer  121  that adheres to the metal plating layer  130 , and a polycarbonate resin to form an external layer  122  that adheres to the ABS resin without adhering to the metal plating layer  130 . The ABS resin is an example of the first resin according to the invention, and the polycarbonate resin is an example of the second resin according to the invention. Further, the inner housing  120  covers the concave groove  113  of the main body  110  excluding both end portions  113   a  and  113   b  in the arrow-A direction, this section being inner than the both end portions  113   a  and  113   b  of the concave groove  113  of the main body  110 . A concave groove  123  is formed in the inner housing  120  and has a width equal to a width of the concave groove  113  of the main body  110  and extending in the arrow-A direction. Furthermore, the inner housing  120  has the metal plating layer  130  along a section of an inner wall that defines a wave receiving transmission path (a transmission path) formed by covering the concave groove  113  of the main body  110  with the inner housing  120  and bonding them, namely, over the entire surface of the concave groove  123  of the inner housing  120 . 
     As shown in  FIG. 4 , the metal plating layer  130  has a two-layer structure that protects against corrosion. Specifically, this metal plating layer  130  has: a copper plating layer  131  that adheres to the ABS resin forming each of the internal layers  111  and  121  of the main body  110  and the inner housing  120 , and a nickel plating layer  132  that adheres to and laminated on the copper plating layer  131 . Further, the surface of the ABS resin that adheres to the metal plating layer  130  and forming the internal layers  111  and  121  is roughened in order to increase a degree of adherence to the plating. 
     What is formed by covering the concave groove  113  of the main body  110  with the inner housing  120  and bonding them is the waveguide  100 , and the wave receiving transmission path formed by this becomes the transmission path. Further, the concave groove  113  of the main body  110  is formed inside the both end portions  110   a  and  110   b  of the main body  110 . The inner housing  120  covers the inner part of both end portions  113   a  and  113   b  of the concave groove  113 , and thereby, the waveguide  100  has the transmission path shaped like a letter U as a whole in the embodiment shown. The cross section of the transmission path has a rectangular shape in the embodiment shown, and the waveguide  100  is a waveguide for millimeter waves used for millimeter wave communication of 60 GHz and therefore, the section size of this transmission path is, for example, “0.4 mm×0.4 mm.” It is to be noted that the section size of the transmission path may be larger than or smaller than “0.4 mm×0.4 mm.” 
     In this way, the waveguide  100  of the shown embodiment includes the main body  110  and the inner housing  120 , and the transmission path is the wave receiving transmission path formed by the respective concave grooves  113  and  123  of the main body  110  and the inner housing  120 . Therefore, when the metal plating layer  130  is formed on each of the main body  110  and the inner housing  120 . As a result, the main body  110  and the inner housing  120  may be separated from each other, such that an area where the metal plating layer  130  is to be formed is exposed. Thus, according to the waveguide  100  of the shown embodiment, even if the section size of the transmission path in which the cross section has the rectangular shape is “0.4 mm×0.4 mm” which is extremely small, it is possible to avoid a problem of clogging the transmission path due to plating accumulation. Further, according to the waveguide  100  of the shown embodiment, it is possible to avoid a problem uneven plating. Moreover, according to the waveguide  100  of the sown embodiment, visual inspection of the metal plating layer  130  is easy and thus, a defect in the metal plating layer such as “plating missing” may be removed. As a result, the surface of the metal plating layer  130  may be made even. 
     This concludes the description of one embodiment of the invention, and another embodiment of the invention will be described. 
     As shown in  FIG. 7 , a waveguide  200  according to another embodiment of the invention is a hollow waveguide made of resin and is configured of the main body  210  and the inner housing  220 , and has a metal plating layer  230  on an inner surface of a tube made of resin (namely, an inner wall of a transmission path). Further, the waveguide  200  extends in an arrow-B direction which is a longitudinal direction while curving, and has a rectangular cross section. Furthermore, like the waveguide  100 , waveguide  200  is a waveguide for millimeter waves used for millimeter wave communication of 60 GHz. 
     The main body  210  shown in  FIG. 7 ,  FIG. 8  and  FIG. 10  is formed by molding of an ABS resin. The ABS resin is an example of the resin member according to the invention. Further, a concave groove  211  is formed in the main body  210 , excluding both end portions  210   a  and  210   b  of the main body  210  in the arrow-B direction. Furthermore, the main body  210  has the metal plating layer  230  over the entire surface of the concave groove  211 . Moreover, the main body  210  has, at each of both end portions  211   a  and  211   b  of the concave groove  211  in the arrow-B direction, a wave receiving passageway  212  that penetrates the main body  210  in an arrow-C direction that is a direction intersecting the arrow-B direction and has the metal plating layer  230  over the entire surface. It is to be noted that the concave groove  211  and the wave receiving passageway  212  may be formed by molding, or may be formed by, for example, other modifications such as machining. 
     Similarly to the main body  210 , the inner housing  220  shown in  FIG. 7 ,  FIG. 9  and  FIG. 11  is formed by molding an ABS resin. Further, the inner housing  220  has a flat shape with a width equal to a width of the main body  210 , and covers the entire concave groove  211  of the main body  210 . Furthermore, the inner housing  220  has the metal plating layer  230  over an entire face  221  including a part of an inner wall that defines a wave receiving transmission path (a transmission path) formed by covering the concave groove  211  of the main body  210  with the inner housing  220  and applying ultrasonic welding or heat welding thereto. 
     As shown in  FIG. 8  and  FIG. 9 , the metal plating layer  230  in the embodiment shown has a three-layer structure which protects against corrosion. Specifically, the metal plating layer  230  has a copper plating layer  231  that adheres to the ABS resin forming each of the main body  210  and the inner housing  220 , a nickel plating layer  232  that adheres to and laminated on this copper plating layer  231 , and a gold plating layer  233  that adheres to and laminated on the nickel plating layer  232 . Further, surfaces of each of the concave groove  211  and the wave receiving passageway  212  of the main body  210  as well as the face  221  of the inner housing  220 , each of which includes areas that adhere with the metal plating layer  230  (this area will be hereinafter referred to as a plating area), are roughened to increase an adherence to the plating. Thus, the metal plating layer  230 , which is formed by plating the surface of the ABS resin forming each of the main body  210  and the inner housing  220  with metal after selectively roughening the surfaces, is obtained by masking an area of the surface of the ABS resin excluding the above-described plating area, in a roughening process and a plating process. 
     What is formed by covering the concave groove  211  of the main body  210  with the inner housing  220  and applying ultrasonic welding or heat welding thereto is the waveguide  200  according to the invention, and the wave receiving transmission path formed thereby becomes the transmission path. Further, the concave groove  211  of the main body  210  is formed inside both end portions  210   a  and  210   b  of the main body  210  and furthermore, the wave receiving passageway  212  is provided in each of the both end portions  211   a  and  211   b  of the concave groove  211 , and the inner housing  220  covers the entire concave groove  211  and thereby, the waveguide  200  has transmission path shaped like a letter U in a manner similar to the waveguide  100  of the aforementioned embodiment. Moreover, similar to the waveguide  100 , the cross section of this transmission path is rectangular, and the waveguide  200  is a waveguide for millimeter waves used for the millimeter wave communication of 60 GHz and thus, the section size of this transmission path is, for example, “0.4 mm×0.4 mm.” It is to be noted that the section size of the transmission path may be larger than, or may be smaller than “0.4 mm×0.4 mm.” 
     It is to be noted that the waveguide  200  has been described by taking the example in which “each of the main body and the inner housing is made of one kind of resin having the metal plating layer selectively, and the selective metal plating layer is obtained by masking the area excluding the plating area in the roughening process and the plating process.” However, the way of implementing the selective metal plating layer on the waveguide having the one kind of resin is not limited to this. For example, it may be a way of implementing a selective metal plating layer, in which “each of a main body and an inner housing is made of one kind of resin with copper mixed, and the copper is separated from the resin by irradiating a selected area of the surface of this resin with an infrared laser and exposed at a laser irradiation point, and this is put in a copper plating bath, so that a copper plating layer is selectively formed.” 
     In this way, the waveguide  200  is configured of the main body  210  and the inner housing  220 , and the transmission path is the wave receiving transmission path formed by covering the concave groove  211  of the main body  210  with the inner housing  220  having a flat shape. Thus, when the metal plating layer  230  is formed along each of the main body  210  and the inner housing  220 , in a manner similar to that of the waveguide  100 , and the main body  210  and the inner housing  220  are separate from each other, the metal plating layer  230  is exposed. Therefore, according to the waveguide  200  of the invention, similarly to the waveguide  100 , it is possible to avoid a problem of clogging of the transmission path due to plating accumulation. Further, according to the waveguide  200  of the shown embodiment, it is possible to avoid a problem uneven plating. Moreover, according to the waveguide  200  of the sown embodiment, visual inspection of the metal plating layer  230  is easy and thus, a defect in the metal plating layer such as “plating missing” may be removed. As a result, the surface of the metal plating layer  230  may be made even. 
     Further, in the waveguide  200 , the concave groove  211  is formed only in the main body  210 , of the main body  210  and the inner housing  220  forming the waveguide  200 , and the inner housing  220  has the flat shape and thus, production thereof is easier than that of the waveguide  100  of the first embodiment in which the concave groove is formed in each of both the main body and the inner housing. 
     This completes the description of another embodiment of the invention. 
     As described above, the waveguides  100  and  200  according to the invention provides a waveguide made of resin, which enables even metal plating to be formed irrespective of the length in the longitudinal length and the diameter of the transmission path, and makes inspection of the formed metal plating easy. 
     Further, the waveguide of the invention may support various shapes, such as a shape extending linearly in a longitudinal direction like waveguide  100  or a shape extending in a longitudinal direction while curving like waveguide  200 . 
     It is to be noted that for each of the embodiments described above, the description has been provided by taking the example in which the waveguide of the invention is the millimeter-wave waveguide used for the millimeter wave communication of 60 GHz, but the waveguide of the invention is not limited to these, and may be, for example, a millimeter-wave waveguide used for microwave communication, or may be a millimeter-wave antenna. 
     Furthermore, for each of the embodiments described above, the description has been provided by taking the example in which the metal plating layer according to the invention has the two-layer structure or the three-layer structure, but the metal plating layer according to the invention is not limited to these, and may be a metal plating layer having at least one layer in a case where protection against corrosion is not considered. 
     Moreover, each of the main body  210  and the inner housing  220  of the waveguide  200  may be formed by two shot molding. 
     Also, for each of the embodiments described above, the description has been provided by taking the example in which the waveguide of the invention has the rectangular cross section, but the waveguide of the present invention is not limited to these, and may have, for example, a circular cross section. 
     Further, for each of the embodiments described above, the description has been provided by taking the example in which the wave receiving transmission path (transmission path) is defined by bonding the main body and the inner housing of the invention to each other or applying the ultrasonic welding or the heat welding thereto, but these are not limitations, and, for example, the wave receiving transmission path (transmission path) may be defined by fitting or the like. 
     Furthermore, for each of the embodiments described above, the description has been provided by taking the example in which each of the main body and the inner housing according to the invention is one piece in the longitudinal direction, but each of the main body and the inner housing according to the invention is not limited thereto and may be formed by integrating segments resulting from division in a longitudinal direction. 
     Although certain embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.