Patent Publication Number: US-6340923-B1

Title: High frequency relay

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a high frequency relay. 
     2. Disclosure of the Prior Art 
     In the past, high frequency relays have been used to switch high frequency signals. For example, Japanese Patent Early Publication [KOKAI] No. 1-274333 discloses that a high frequency relay comprises a base, on which fixed contacts of gold-plated pins are mounted, a card having contact springs, a shield case having earth terminals manufactured by working a sheet metal, an electromagnet for moving the contact springs to open and close a pair of the fixed contacts by the contact spring, and a shield cover. 
     However, in this kind of high frequency relay, there are problems that variations in high frequency characteristic of the high frequency relay such as such as insertion loss, isolation loss and V.S.W.R. (reflection) occurs due to errors in working and assembling the relay components. On the other hand, when working and assembling the relay components with high accuracy, there is another problem of increasing the production cost of the high frequency relay in a large amount. In particular, as the relay becomes smaller in size, there is a limitation of working and assembling the relay components with high accuracy. 
     SUMMARY OF THE INVENTION 
     Therefore, a primary object of the present invention is to provide a high frequency relay capable of improving electromagnetic shield effect for preventing signal leakage and minimizing variations in high frequency characteristic resulting from steps of working and assembly the relay components. 
     That is, in the high frequency relay comprising a contact base block having at least one pair of fixed contacts, at least one contact member with a movable contact, and an electromagnet for moving the contact member to open and close the pair of fixed contacts by the movable contact, the contact base block comprises a base having at least one pair of projections on its top surface, which is an injection-molded article of an electrical insulating material; first metal films formed as the fixed contacts on top surfaces of the projections; second metal films formed as connection terminals for outside devices on the base, each of which corresponds to one of the first metal films; connecting means for making an electrical connection between each of the first metal films and the corresponding second metal film; and a third metal film at least formed on the top surface of the base to provide electrical isolation from the first and second metal films, which works as electromagnetic shield means. 
     By the way, to stabilize the high frequency characteristic of the high frequency relay, it is important to keep the assembly accuracy of relay components constant. In particular, it is required to accurately determine a distance between each of the fixed contacts and the corresponding connection terminal. In the past, when the relay components including the fixed contacts and the connection terminals are provided as separate parts, it is required to work and assemble each of the relay components with high accuracy, so that there is another problem of increasing the production cost. 
     In the present invention, since the first, second and the third metal films, which respectively function as the fixed contacts, connection terminals, and the electromagnetic shield means for preventing the leakage of the high frequency signals, are integrally formed on the injection-molded base, it is possible to readily and accurately control the distance between each of the fixed contacts and the corresponding connection terminal, and sharply reduce the total number of the relay components. According to these advantages, the present invention can stably provide the high frequency relay having a constant high frequency characteristic. In particular, as the high frequency relay becomes smaller in size, the present invention becomes to be more effective. Moreover, since the first metal films that are the fixed contacts are formed on the top surfaces of the projections, the movable contact can open and close the fixed contacts with reliability without contacting the third metal film. 
     In a preferred embodiment of the present invention, the high frequency relay further comprises a contact sub block for movably supporting the contact member, which comprises a subbase that is an injection-molded article of an electrical insulating material, and a fourth metal film formed on a surface of the subbase in a face to face relation with the top surface of the base when the contact sub block is mounted on the contact base block, so that the pair of fixed contacts are opened and closed by the movable contact in an electromagnetic shield space surrounded by the third and fourth metal films. 
     It is preferred that each of the second metal films is formed on a bottom surface of the base at a position opposed to the corresponding one of the first metal films. In this case, it is preferred that the connecting means is through holes each having a conductive layer on its inner surface, each of which is formed in the base to electrically connect one of the first metal films with the corresponding second metal film in the shortest distance. 
     It is further preferred that each of the projections has a first projection jutting from the top surface of the base and a second projection jutting from the first projection, and wherein each of the first metal films is formed on a top of the second projection and the third metal film is formed on side surfaces of the first projections. In addition, it is preferred that each of the projections has a rounded top, on which the first metal film is formed. 
     In addition, it is preferred that the high frequency relay comprises a first contact set of a first pair of fixed contacts and a first contact member used to switch a high frequency signal and a second contact set of a second pair of fixed contacts and a second contact member used to switch another high frequency signal, and wherein a shield wall for isolating the first contact set from the second contact set is integrally-molded with at least one of the base and the subbase. 
     In addition, it is preferred that the high frequency relay comprises a coil block for housing the electromagnet comprises an armature disposed between the contact member and the electromagnet and driven by energizing the electromagnet, and a motion of the armature is transferred to the contact member through a first spring member held by a spring holding portion integrally molded with the subbase. 
     Moreover, it is preferred that a coil block supporting portion for supporting the coil block and the spring holding portion are provided on a surface opposed to the surface having the fourth metal film of the subbase, and the contact member is attached to a through hole formed in the subbase with a second spring member such that the contact member receives a spring bias of the second spring member in a direction of spacing the movable contact from the fixed contacts, and the contact member can be moved against the spring bias of the second spring member by the first spring member pushed by the armature to close the fixed contacts by the movable contact. 
     It is also preferred that the high frequency relay comprises fifth metal films formed as coil electrodes for supplying electric power to the electromagnet on the base so as to provide electrical isolation from the first, second and third metal films. 
     Another object of the present invention is to provide a high frequency relay having the following structure. That is, in the high frequency relay comprising a contact base block having at least one pair of fixed contacts, at least one contact member with a movable contact, a contact sub block for movably supporting the contact member, and an electromagnet for moving the contact member to open and close the pair of fixed contacts by the movable contact, the contact base block comprises a base that is an injection-molded article of an electrical insulating material; first metal films formed as the fixed contacts on a top surface of the base; second metal films formed as connection terminals for outside devices on the base, each of which corresponds to one of the first metal films; connecting means for making an electrical connection between each of the first metal films and the corresponding second metal film; and a third metal film at least formed on the top surface of the base to provide electrical isolation from the first and second metal films, which works as electromagnetic shield means. In addition, the contact sub block comprises a subbase that is an injection-molded article of an electrical insulating material, and a fourth metal film formed on a surface of the subbase in a face to face relation with the top surface of the base when the contact sub block is mounted on the contact base block, so that the pair of fixed contacts are opened and closed by the movable contact in an electromagnetic shield space surrounded by the third and fourth metal films. 
     In the present invention, since the first, second and the third metal films, which respectively function as the fixed contacts, connection terminals, and the electromagnetic shield means for preventing the leakage of the high frequency signals, are integrally formed on the injection-molded base, and the fourth metal film is integrally formed as the electromagnetic shield means on the injection-molded subbase, there is an advantage that the electromagnetic shield space having a remarkable effect of preventing the signal leakage can be stably obtained in the high frequency relay by the third and fourth metal films even when the high frequency relay is small-sized. 
     These and still other objects and advantages will become apparent from the following detailed description of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a high frequency relay according to a preferred embodiment of the present invention; 
     FIG. 2 is an exploded view of the high frequency relay; 
     FIGS. 3A to  3 F are a front view, cross-sectional view taken along the line L, side view, rear view, cross-sectional view taken along the line M, and a side view of a contact base block of the high frequency relay, respectively; 
     FIGS. 4A to  4 F are a front view, a cross-sectional view taken along the line P, side view, rear view, cross-sectional view taken along the line Q, and a side view of an injection-molded base of the contact base block, respectively; 
     FIG. 5A is a partially perspective view of the contact base block, and FIG. 5B is a partially perspective view showing a modification of FIG. 5A; 
     FIGS. 6A to  6 E are a front view, cross-sectional view taken along the line R, side view, rear view and a side view of a contact sub block of the high frequency relay, respectively; 
     FIG. 7A is a top view of a first spring member, and FIG. 7B is a cross-sectional view of a subbase with the first spring members; 
     FIG. 8A is a schematic view illustrating how to attach a contact member to a second spring member, and FIGS. 8B to  8 D are a front view, back view and a side view of the assembly of the contact member and the second spring member, respectively; 
     FIGS. 9A and 9B are side views illustrating how to attach a coil block to the contact sub block, respectively; 
     FIGS. 10A to  10 C are a front view, cross-sectional views taken along the lines S and T of a modification of the contact base block; 
     FIGS. 11A and 11B are schematic cross-sectional views illustrating an insertion of a metal pin into a through hole of the contact base block; 
     FIGS. 12A and 12B are schematic cross-sectional views illustrating a charge of a sealing compound into a through hole of the contact base block; 
     FIGS. 13A to  13 D are a front view, side view, rear view and a side view of an injection-molded base of a contact base block according to another embodiment of the present invention, respectively; 
     FIGS. 14A to  14 D are a front view, side view, rear view and a side view of the contact base block, respectively; 
     FIG. 15 is a partially perspective view of the contact base block; 
     FIGS. 16A to  16 D are a front view, cross-sectional view taken along the line V, rear view and a cross-sectional view taken along the line W of an injection-molded subbase of a contact sub block according to another embodiment of the present invention, respectively; 
     FIGS. 17A to  17 D are a front view, cross-sectional view taken along the line X, rear view and a cross-sectional view taken along the line Y of the contact sub block, respectively; 
     FIGS. 18A to  18 F are schematic diagrams illustrating a method of manufacturing a contact base block of the high frequency relay according to a preferred embodiment of the present invention; 
     FIG. 19 is a plan view illustrating electrode members used for electroplating; 
     FIG. 20 is a wiring diagram for the electroplating; 
     FIG. 21 is another wiring diagram for the electroplating; and 
     FIGS. 22A to  22 K are schematic diagrams illustrating a method of manufacturing a contact base block of the high frequency relay according to a further preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A high frequency relay according to a preferred embodiment of the present invention is explained in detail referring to the attached drawings. 
     As shown in FIGS. 1 and 2, the high frequency relay is mainly composed of a contact base block  1  having plural pairs of fixed contacts, a contact sub block  2  for movably supporting contact members  21  with movable contacts  22 , an electromagnet  3  for moving the contact members to open and close the fixed contacts by the movable contacts, coil block  4  for supporting the electromagnet, and a relay case  5 . 
     As shown in FIGS. 3A to  3 F and  4 A to  4 F, the contact base block  1  comprises a base  10 , first metal films  70  formed as the fixed contacts on the base, second metal films  80  formed as connection terminals for outside devices on the base, each of which corresponds to one of the first metal films, and a third metal film  90  formed as a part of electromagnetic shield means on the base to provide electrical isolation from the first and second metal films. 
     The base  10  is an injection-molded article of an electrical insulating material having a rectangular case shape composed of a bottom wall  11 , side walls  12  jutting on the periphery of the bottom plate, and a top opening. The base  10  has a plurality of first projections  13  jutting from the bottom wall  11 , each of which is of a rectangular shape, and second projections  14  jutting from the top surfaces of the first projections, each of which is of a smaller rectangular shape. Each of the second projections has a through hole  16  extending from the top surface of the second projection to the rear surface of the base  10 . In this embodiment, the high frequency relay has a first contact set of the fixed contacts (upper  3  fixed contacts of FIG. 3A) and the contact members used to switch a high frequency signal and a second contact set of the fixed contacts (lower  3  fixed contacts of FIG. 3A) and the contact members used to switch another high frequency signal. 
     The numeral  17  designates through-holes extending from the front surface to the rear surface of the bottom wall  11  of the base  10 . The numeral  18  designates guide projections jutting from the top of side walls  12 , which are used to readily and accurately mount the contact sub block on the contact base block. Thus, since the base having the first and second projections  13 ,  14 , through holes  16 ,  17 , and guide projections  18  is formed by injection molding, it is possible to stably supply the base having a constant dimensional accuracy and reduce the number of the relay components. The through holes  16 ,  17  may be formed by drilling after the injection molding. 
     Each of the first metal films  70  is formed on the top and side surfaces of the second projection  14 , as shown in FIG.  3 A. Since the first metal films  70  that are the fixed contacts are formed on the top surfaces of the second projections  14 , the movable contact  22  can open and close the fixed contacts with reliability without contacting the third metal film  90 . In this embodiment, the second projection  14  has a rounded rectangular top shown in FIG. 5A to prevent the occurrence of arc discharge between the fixed contacts, i.e., the first metal films  70  and the movable contact  22 . Alternatively, as shown in FIG. 5B, a cylindrical projection having a dome-shaped top may be adopted as the second projection  14 . In this case, it is preferred that the first and second projections are formed such that a center axis of the first projection  13  is in agreement with that of the second projection  14 . 
     Each of the second metal films  80  is formed on the rear surface of the base  10 , as shown in FIG. 3D, at a position opposed to the corresponding one of the first metal films  70 . In addition, a part of the second metal film  80  extends to the side wall  12 , to which desired outside devices such as printed wiring boards can be readily connected by soldering. 
     The third metal film  90  is formed the base  10  to extend from the front surface to the rear surface of the bottom wall  11  through the side walls  12 . The third metal film  90  is also formed on the side surfaces of the first projection  13 , so that the signal leakage can be more effectively prevented when the high frequency signal is transmitted through the through-hole connection between the fixed contact  70  and the corresponding connection terminal  80 . To electrically isolating the third metal film  90  from the first and second metal films  70 ,  80 , an isolation area  50  having no metal film is formed around the first and second metal films. That is, each of the first metal films  70  is electrically isolated from the third metal film  90  by the isolation area  50  formed on the top surface of the first projection  13  around the second projection  14 . 
     Each of the first metal films  70  is electrically connected to the corresponding one of the second metal films  80  by a conductive layer plated on the inner surface of the through hole  16  in the shortest distance. Since a signal-flow path is shortened by the through-hole connection, it is effective to improve noise immunity. In this case, it is preferred that a center axis of the through hole  16  is substantially in agreement with that of the fist and second projections  13 ,  14 . In addition, the third metal film  90  on the front surface of the bottom wall  11  is electrically connected to the third metal film on the rear surface of the bottom wall by conductive layers plated on the inner surfaces of the through holes  17  in the shortest distance. Since the electrical connection between the third metal films of the front and rear surfaces of the bottom wall  11  of the base  10  by the through holes  17  in the shortest distance provides the same potential at every position of the third metal film  90 , it is effective to further improve the high frequency characteristic of the relay. These through holes  16 ,  17  are filled with a sealing material  62 ,  64  such as conductive materials and synthetic resins to prevent the occurrence of condensation therein. 
     The numeral  100  designates fifth metal films formed on the opposite side walls  12 , which are used as coil electrodes for supplying electric power to the electromagnet  3  of the high frequency relay. The fifth metal films  100  are electrically isolated from the third metal film by the isolation area  50 . Since an electrical connection between the electromagnet  3  and the coil electrodes  100  formed on the base  10  can be achieved by use of wires and so on, it is useful to provide a further simplification of the assembly task for the high-frequency relay. 
     By the way, it is preferred that each of the first, second and third metal films  70 ,  80 ,  90  is composed of a copper layer as an undercoat, nickel layer as an intermediate layer, and a gold layer as an outer layer. In this case, it is particularly preferred that a thickness of the outer layer of the first metal films is greater than that of the second and third metal films. Alternatively, the second and third metal films may essentially consist of a copper layer as the undercoat, and a nickel layer as the outer layer. By reducing the amount used of gold, it is possible to improve cost performance of the high frequency relay. 
     As shown in FIG. 2, the contact sub block  2  comprises a subbase  30 , the contact members  21  with the movable contacts  22 , a fourth metal film  92  formed on a rear surface of the subbase, first spring members  42  for transferring a motion of an armature  52  driven by energizing the electromagnet  3  to the contact members  21 , and second spring members  45  each applying a spring bias to the contact member in a direction of spacing the movable contact  22  from the fixed contacts  70 . 
     As shown in FIGS. 6A to  6 E, the subbase  30  is an injection-molded article of an electrical insulating material, and has four rectangular through holes  32 , a pair of side walls  34  projecting from its front surface of the subbase and having bearing portions  35  for movably supporting the armature  52  in a seesaw fashion, spring holders  36  projecting from the front surface of the subbase, each of which is used to catch one end of the first spring member  42 , and stoppers  37  projecting from the front surface of the subbase between adjacent rectangular through-holes  32 , each of which restricts an excessive motion of the first spring member. The numeral  38  designates concaves formed in a rear surface of the subbase, into which the guide projections  18  are fitted when the contact sub block  2  is mounted on the contact base block  1 . 
     The fourth metal film  92  on the subbase  30  makes an electromagnetic shield space in cooperation with the third metal film  90  of the contact base block  1 . In this electromagnetic shield space, each of the pairs of fixed contacts  70  is opened and closed by the corresponding movable contact  22 . The formation of the electromagnetic shield space presents a remarkable effect of preventing the leakage of high frequency signal to the outside as well as an improvement in noise immunity. In this embodiment, when the pair of fixed contacts  70  is opened by the movable contact  22 , the movable contact comes into contact with a required region  94  of the fourth metal film  92 . The required region  94  of the fourth metal film  92  is composed of a copper layer as an undercoat, nickel layer as an intermediate layer and a gold layer as an outer layer. The remainder of the fourth metal film  92  other than the required region  94  is composed of a copper layer as the undercoat and a nickel layer as the outer layer. 
     The first spring member  42  is of a T-shaped spring having an attachment hole  43  at one end, as shown in FIG.  7 A. To fix the first spring member  42  to the subbase  30 , the spring holder  36  is inserted into the attachment hole  43  of the first spring member, as shown in FIG.  7 B. By use of this spring holder  36  integrally formed with the subbase  30 , it is possible to readily mount the first spring member  42  at a required position on the subbase with accuracy. Since the stopper  37  restricts the excessive motion of the first spring member  42 , it is possible to prevent the occurrence of abnormal contact pressure between the movable contact  22  and the fixed contacts  70 . 
     As shown in FIGS. 8A to  8 D, the contact member  21  is composed of a cylindrical body  23  having a dome-shaped top  24  and the movable contact  22  of a metal plate projecting from the side face of the cylindrical body in the opposite two directions. The second spring member  45  is of a rhombus shape having a first notch  46  for receiving the dome-shaped top and a second notch  47  for receiving the cylindrical body  23  of the contact member  21 . As shown in FIG. 8A, the contact member  21  and the second spring member  45  are assembled by inserting the contact member into the first and second notches  46 ,  47 . The contact member  21  has incisions  26  in the dome-shaped top, to which the first notch  46  of the second spring member  45  is fitted, as shown in FIG.  8 C. 
     The assembly of the contact member  21  and the second spring member  45  is attached to the rectangular through-hole  32  of the subbase  30  such that the contact member receives the spring bias of the second spring member in the direction of spacing the movable contact  22  from the fixed contacts  70  when the contact sub block  2  is mounted on the contact base block  1 , as shown in FIG.  1 . When the first spring member  42  is pushed down by the armature  52 , the contact member  21  is moved against the spring bias of the second spring member  45  to close the fixed contacts  70  by the movable contact  22 . On the contrary, when the armature is released from the motion of the armature  52 , the contact member  21  is pushed upward by the spring bias of the second spring member  45  to leave the movable contact  22  from the fixed contacts  70 . At this time, as described above, the movable contact  22  comes into contact with the required region  94  of the fourth metal film  92 . 
     As shown in FIG. 2, the coil block  4  is an injection-molded article of an electrical insulating material, which houses the electromagnet  3  including a coil, iron core, and a permanent magnet and the armature  52 . When the coil block  4  is mounted on the contact sub block  2 , as shown in FIGS. 9A and 9B, pivot shafts  53  of the armature  52  are supported by the bearing portions  35  of the subbase  30  such that the armature can be driven in the seesaw fashion by energizing the electromagnet  3 . 
     The high frequency relay having the above-explained structure operates as follows. The electromagnet  3  is energized by applying a required voltage thereto, so that the armature  52  is driven in the seesaw fashion. For example, when the armature is driven, as shown in FIG. 1, the motion of the armature  52  is transferred to one of the contact members  21  through the first spring member  42 , so that the contact member is moved against the spring bias of the second spring member  45  to obtain a connection between the fixed contacts  70 ( b ),  70 ( c ) by the movable contact  22 ( b ). On the other hand, since the motion of the armature  52  is not transferred to the other one of the contact members  21 , the contact member receives the spring bias of the second spring member  45 , so that the movable contact  22 ( a ) is spaced from the fixed contacts  70 ( a ),  70 ( b ), and comes into contact with the fourth metal film  92  of the subbase  30 . From the above, the high frequency signals flow between the fixed contacts  70 ( b ),  70 ( c ) with the help of the movable contact  22 ( b ). 
     A modification of the contact base block of the above embodiment is shown in FIGS. 10A to  10 C, which is substantially the same as that of above embodiment except for the following structural features. That is, this contact base block  1  is characterized by comprising a shield wall  25  integrally formed with the base  10  to separate a first contact set of the fixed contacts (upper 3 fixed contacts  70  of FIG. 10A) and the contact members  21  used to switch a high frequency signal from a second contact set of the fixed contacts (lower 3 fixed contacts  70  of FIG. 10A) and the contact members  21  used to switch another high frequency signal. The formation of the shield wall  25  is effective to improve signal isolation performance between the first and second contact sets and prevent the occurrence of signal leakage. Alternatively, the shield wall  25  may be integrally formed with the subbase  30 , or completed by a first shield wall integrally formed with the base and a second shield wall integrally formed with the subbase. 
     In the above embodiment, the conductive layer  68  is formed on the inner surface of the respective through holes  16  and then the sealing material  62  is charged into the through holes. As shown in FIGS. 11A and 11B, a metal pin  65  may be inserted into the through hole  16  to make the electrical connection between one of the fixed contacts, i.e., the first metal films  70 , and the corresponding second metal film  80 . In this case, it is preferred to determine the length of the metal pin  65  such that a top end of the metal pin inserted into the through hole slightly projects on the first metal film  70 , as shown in FIG.  11 B. Since the movable contact  22  comes into contact with the top end of the metal pin  65 , it is possible to provide an extended life of the fixed contacts  70 . The metal pin  65  may be press-inserted into the through hole  16  or fixed to the through hole by use of an adhesive. 
     As the sealing material charged into the through hole  16 ,  17  of the base  10 , for example, it is preferred to use an epoxy resin. In this case, since shrinkage of the epoxy resin is caused in the through hole by heating and drying the charged epoxy resin, it is possible to stably perform the sealing operation without allowing the resin to overflow from the through hole. In place of the charge of the sealing material, a synthetic-resin pin may be inserted into the through hole and then melted therein. 
     In place of the formation of the conductive layer in the through hole  16  and the charge of the sealing material  62  into the through hole, a conductive paste material such as silver, nickel and solder pastes may be charged into the through hole  16 . In this case, since electric current flows between the first and second metal films  70 ,  80  through the charged conductive paste material having an increased cross section, it is possible to reduce the electrical resistance and provide an improved shield effect. 
     In case of charging the sealing material or the conductive paste material, it is preferred that the through hole is a countersunk hole  19 , as shown in FIGS. 12A and 12B. That is, FIG. 12A shows a state of the instant following of charging the sealing material  62  into the countersunk hole  19 , and FIG. 12B shows the sealing material  62  cured in the countersunk hole. Since a diameter of the through hole in the vicinity of the first metal film  70  is greater than the diameter of the interior of the through hole, it is possible to effectively prevent the overflow of the sealing material  62  or the paste material from the through hole. 
     Next, a contact base block and a contact sub block of the high frequency relay according to another embodiment of the present invention are explained referring to the attached drawings. 
     FIGS. 13A to  13 D show a base  10  of the contact base block  1  that is an injection-molded article of an electrical insulating material. The base  10  is of a rectangular plate shape having rectangular projections  14  on its front surface. First, second and third metal films  70 ,  80 ,  90  are formed on the base  10 , as shown in FIGS. 14A to  14 D. That is, the first metal films  70  are formed on the projections  14 . Each of the second metal films  80  is formed at a position opposed to the corresponding one of the first metal films  70  on a rear surface of the base. The first metal film  70  is electrically connected to the corresponding second metal film  80  by a sixth metal film  72  formed on side surface of the base  10 , as shown in FIG.  14 B. The third metal film  90  is formed to extend from the front surface to the rear surface through the side surfaces of the base  10 . The first, second and sixth metal films  70 ,  80 ,  72  are isolated from the third metal film  90  by an isolation area  50  having no metal film. Each of the rectangular projections  14  has a pair of rounded sides on its top to prevent the occurrence of arc discharge between the fixed contacts  70  and the movable contact  22 , as shown in FIG.  15 . The numeral  100  designates coil electrodes for supplying electric power to the electromagnet  3  of the high frequency relay, which are electrically isolated from the third metal film  90  by the isolation area  50 . 
     FIGS. 16A to  16 D show a subbase  30  of the contact sub block  2  that is an injection-molded article of an electrical insulating material. The subbase  30  is of a rectangular case shape composed of a bottom wall  31 , side walls  39  jutting from the periphery of the bottom wall, and a top opening. The side walls  39  have concaves  33 , to which the rectangular projections  14  of the base  10  are fitted when the contact sub block  2  is mounted on the contact base block  1 . Therefore, these projections  14  and the concaves  33  also function as guide means for readily and accurately mounting the contact sub block  2  on the contact base block  1 . 
     As shown in FIGS. 17A to  17 D, a fourth metal film  92  is formed on inner surfaces of the rectangular case of the subbase  30 . The third metal film  90  on the base  10  makes an electromagnetic shield space for preventing a leakage of high frequency signal in cooperation with the fourth metal film  92  when the contact sub block  2  is mounted on the contact base block  1 . The numeral  32  designates circular through-holes, to each of which the assembly of the contact member  21  having the movable contact  22  and the first spring member  45  is attached. 
     Next, an embodiment of a method of manufacturing the contact base block  1  of the high frequency relay of the present invention is explained referring to FIGS. 18A to  18 F. 
     After the base  10  is injection-molded with the electrical insulating resin material (FIG.  18 A), a chromium film  110  is deposited on the base  10  by spattering, as shown in FIG.  18 B. Next, a copper film  120  is deposited on the chromium film  110  by spattering in the atmosphere of argon, as shown in FIG. 18C, to obtain an undercoat. The chromium film  110  is effective to improve adhesion between the base  10  and the copper film  120 . Then, as shown in FIG. 18D, a part of the undercoat is removed from the base  10  by irradiating a laser beam  200  to the undercoat along a required pattern to obtain a patterned undercoat. Next, as shown in FIG. 18E, an intermediate layer  130  of nickel is formed the patterned undercoat by electroplating, and then an outer layer  140  of gold is formed on the intermediate layer  130  by electroplating, as shown in FIG.  18 F. According to the above method, the first, second and third metal films  70 ,  80 ,  90  can be formed at a time on the base  10 . 
     In case of controlling the plating thickness of the gold layer such that the thickness of the gold layer of the first metal film  70  is thicker than that of the third metal film  90 , for example, it is preferred to perform the electroplating by use of electrode members  210  shown in FIGS. 19 and 20. That is, the nickel layers of the first metal films  70  are connected to a power source  220  through electrode members  210 . On the other hand, the nickel film of the third metal film  90  is connected to the same power source  220  through a resistance R. The electrode members  210  are electrically isolated from the third metal film  90 . Since a smaller amount of electric current is supplied to the nickel film of the third metal film  90  due to the presence of the resistance R, it is possible to readily obtain the third metal film  90  having a reduced thickness of the gold layer. 
     In addition, it is possible to form the gold layers on only the nickel layers of the first metal films  70  by electroplating. That is, as shown in FIG. 21, the nickel layers of the first metal films  70  are connected to a first power source  220  through the electrode members  210 . On the other hand, the nickel layer of the third metal film  90  is connected to a second power source  230 . In case of the electroplating of gold, electric current is supplied to only the nickel films of the first metal films  70  from the first power source  220 . On the other hand, when the electroplating of a metal other than gold is required for the third metal film  90 , electric current is supplied to only the nickel film of the third metal film from the second power source  230 . 
     A further preferred embodiment of the method of manufacturing the contact base block of the high frequency relay of the present invention is explained referring to FIGS. 22A to  22 K. 
     After the base  10  is injection-molded with the electrical insulating resin material (FIG.  22 A), a roughing treatment  300  is performed on a surface of the base  10  with use of sodium hydroxide, as shown in FIG.  22 B. Next, a catalyst  310  is applied on the roughed surface  300 , as shown in FIG.  22 C. Then, an undercoat of copper  320  is formed on the roughed surface with the catalyst by electroless plating, as shown in FIG.  22 D. After a photoresist film  330  is formed on the undercoat  320 , as shown in FIG. 22E, a laser beam  340  is radiated to the photoresist film  330  along a required pattern, as shown in FIG.  22 F. By developing this, a patterned resist film is obtained on the undercoat. 
     The exposed undercoat is removed from the base  10  by chemical etching (FIG.  22 G). Since a required region of the undercoat  320  is removed by use of the patterned resist film  330  by the laser beam  340 , it is possible to readily obtain a precision pattern of the undercoat. At this time, since the catalyst remains on the exposed surface of the base  10 , it is preferred to remove the insulating material in the vicinity of the exposed surface of the base together with the remaining catalyst by use of sodium hydroxide, as shown in FIG.  22 H. Thus, a fresh surface  360  of the base  10  is exposed along the required pattern. Next, the patterned resist is removed to obtain a patterned undercoat  320  of copper, as shown in FIG.  221 . Then an intermediate layer  370  of nickel is formed on the patterned undercoat  320  by electroplating, and an outer layer  380  of gold is formed on the intermediate layer  370 , as shown in FIGS. 22J and 22K. If necessary, the step of FIG. 22H may be omitted. 
     From understood from the above embodiments, the present invention provides the high frequency relay with a refined structure having the capability of enhancing the assembly task of the relay and effectively preventing the leakage of high frequency signals.