Patent Publication Number: US-11037741-B2

Title: Switch and method of manufacturing switch

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is based upon and claims priority to Japanese Patent Application No. 2019-022996, filed on Feb. 12, 2019, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     An aspect of this disclosure relates to a switch. 
     2. Description of the Related Art 
     Japanese Laid-Open Patent Publication No. 2018-014276, for example, discloses a switch including a chip resistor attached to a metal plate by reflow soldering. 
     In a process for manufacturing the switch, a component formed of a synthetic resin material and including a metal plate embedded by insert molding is placed in a reflow furnace. For this reason, the synthetic resin material needs to have a heat resistance property to withstand a reflow temperature. However, the use of such a heat-resistant synthetic resin material increases the cost for manufacturing a switch. 
     Accordingly, there is a demand for a switch that can be manufactured at a lower cost. 
     SUMMARY OF THE INVENTION 
     In an aspect of this disclosure, there is provided a switch including a housing, a switching mechanism that is housed in the housing and configured to switch a state of connection between at least two terminals exposed out of the housing by using a common contact and two switching contacts, and an electronic component that is disposed in the housing and electrically connects the at least two terminals to each other. The switching mechanism includes a first metal plate that is connected to a first contact, which is one of the common contact and the two switching contacts, and includes a first exposed part to which a first electrode of the electronic component is soldered by laser irradiation, and a second metal plate that is connected to a second contact, which is another one of the common contact and the two switching contacts, and includes a second exposed part to which a second electrode of the electronic component is soldered by laser irradiation. The first exposed part includes a first electrode mounting part on which the first electrode is placed, a first soldering part on which solder is placed, and a first peripheral part disposed along an edge of the first soldering part; the second exposed part includes a second electrode mounting part on which the second electrode is placed, a second soldering part on which solder is placed, and a second peripheral part disposed along an edge of the second soldering part; and each of the first peripheral part and the second peripheral part has a U-shape. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a switch; 
         FIGS. 2A and 2B  are a top perspective view and a bottom perspective view of the switch; 
         FIGS. 3A and 3B  are a perspective view and a front view of the switch from which a case and a lever are removed; 
         FIGS. 4A and 4B  are perspective views of the switch from which some components are removed; 
         FIGS. 5A-5C  are a front view, a rear view, and a right-side view of a holding part; 
         FIG. 6  is a bottom perspective view of a case; 
         FIG. 7  is a front view of a metal plate; 
         FIG. 8  is a front view of a metal plate; 
         FIG. 9  is a drawing illustrating a laser soldering device; 
         FIGS. 10A and 10B  are enlarged views of exposed parts to which a resistor is soldered; 
         FIG. 11  is a diagram of a detection circuit of the switch; 
         FIG. 12  is a flowchart illustrating a process of manufacturing the switch; 
         FIGS. 13A and 13B  are front views of a metal plate before and after being punched; 
         FIG. 14  is a front view of a metal plate after a molding step; 
         FIG. 15  is a front view of a metal plate after a solder applying step; and 
         FIGS. 16A and 16B  are front views of a metal plate before and after a laser soldering step. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the present invention is described below with reference to the accompanying drawings.  FIG. 1  is an exploded perspective view of a switch  100 .  FIG. 2A  is a top perspective view of the switch  100 , and  FIG. 2B  is a bottom perspective view of the switch  100 .  FIG. 3A  is a top perspective view of the switch  100  from which a case K 1  and a lever LV are removed, and  FIG. 3B  is a front view of the switch  100  from which the case K 1  and the lever LV are removed.  FIG. 4A  is a top perspective view of the switch  100  from which a cover C 2  and a moving part  2  are further removed, and  FIG. 4B  is a top perspective view of the switch  100  from which a biasing part  3  and a resistor R 9  are further removed. Each of  FIGS. 2A, 2B, 3A, 3B, and 4A  illustrates the switch  100  in an initial state where an operation part  2   t  is not pressed. 
     The switch  100  includes a housing  1  having a box-like outer shape, a switching mechanism MC that switches the state of connection between at least two terminals T 8  extending out of the housing  1  by using a common contact and two switching contacts, and electronic components (resistors R 9 ) that are disposed in the housing  1  and electrically connect the terminals T 8  to each other. 
     The switching mechanism MC is partially housed in the housing  1  and includes a moving part  2  that moves when the operation part  2   t  is pressed, a biasing part  3  that causes the pressed moving part  2  to return to the initial state where the moving part  2  is not pressed, a movable contact  4  that moves along with the movement of the moving part  2 , and a metal plate M that provides the common contact and the two switching contacts. 
     The metal plate M includes a common fixed contact G 5  used as a common contact that is continuously in contact with the movable contact  4 , a first switching fixed contact  15  and a second switching fixed contact  25  used as switching contacts that contact and move away from the movable contact  4  according to operations of the operation part  2   t , and the terminals T 8  extending out of the housing  1 . 
     In the present embodiment, the electronic components are resistors R 9  for providing resistance between the two terminals T 8 . The resistors R 9  include a first resistor R 9   a  and a second resistor R 9   b.    
     The switch  100  further includes a lever LV for operating (pressing) the operation part  2   t  and a cover C 2  disposed on the upper side of the housing  1  (on the Z1 side in  FIG. 2 ). 
     Next, components of the switch  100  are described in more detail.  FIG. 5A  is a front view of a holding part H 1  seen from the Y2 side in  FIG. 1 .  FIG. 5B  is a rear view of the holding part H 1  seen from the Y1 side in  FIG. 1 , and  FIG. 5C  is a right-side view of the holding part H 1  seen from the X1 side in  FIG. 1 .  FIG. 6  is a bottom perspective view of the case K 1 .  FIGS. 7 and 8  are front views of the metal plate M that is partially embedded in the holding part H 1 . 
     The housing  1  of the switch  100  is formed of a synthetic resin material and includes the holding part H 1  in which the metal plate M is embedded as illustrated in  FIG. 4B  and the case K 1  shaped like a box whose bottom is open as illustrated in  FIG. 6 . Also, in the housing  1 , as illustrated in  FIG. 2B , the holding part H 1  is disposed to close the bottom of the case K 1 , and the holding part H 1  and the case K 1  are joined together. 
     As illustrated in  FIGS. 4A through 6 , the holding part H 1  of the housing  1  includes a bottom wall  11  that closes the bottom of the case K 1  (see  FIG. 2B ) and a holding wall  51  provided above the bottom wall  11 . 
     As illustrated in  FIG. 4B , the holding part H 1  is formed by injection molding of a first synthetic resin material, and a part of the metal plate M is embedded in the holding part H 1  by insert molding. The first synthetic resin material is, for example, a polybutylene terephthalate (PBT) resin containing glass fibers and having a heat distortion temperature between about 120 and about 220 degrees Celsius. 
     The heat distortion temperature is a temperature at which the amount of deflection of a sample of a synthetic resin material reaches a predetermined value when the temperature of the sample is increased while applying a predetermined load defined in a test method standard to the sample. The heat distortion temperature may also be referred to as a load deflection temperature. Here, because the melting temperature of a typical solder (lead-free solder) is between 217 and 220 degrees Celsius, the reflow temperature for reflow soldering is generally between 220 and 250 degrees Celsius. 
     As described later, the resistors R 9  used as electronic components are bonded to the metal plate M by laser soldering. For this reason, the first synthetic resin material need not have a heat resistance property to withstand the reflow temperature. That is, the first synthetic resin material may be a thermoplastic synthetic resin material having a heat distortion temperature lower than the reflow temperature. For example, the first synthetic resin material may be a polyacetal resin (POM, polyoxymethylene) that does not contain glass fibers and have a heat distortion temperature between about 90 and 130 degrees Celsius, or a polyacetal resin (POM) containing glass fibers and having a heat distortion temperature between about 110 and 170 degrees Celsius. Also, the first synthetic resin material may be a thermoplastic synthetic resin material such as an acrylonitrile butadiene styrene (ABS) copolymer resin, a polycarbonate (PC) resin, or a polyethylene terephthalate (PET) resin. The synthetic resin to be used may be selected taking into account the environment where a product is to be used. 
     As illustrated in  FIGS. 5A-5C , the holding wall  51  of the holding part H 1  includes an insulation part  51   r  that extends outward from a frame-shaped part. As illustrated in  FIG. 4B , the insulation part  51   r  is disposed between the first switching fixed contact  15  and the second switching fixed contact  25 . This arrangement ensures insulation between the first switching fixed contact  15  and the second switching fixed contact  25 . The Y1-side surface of the insulation part  51   r  and the Y1-side surfaces of the first switching fixed contact  15  and the second switching fixed contact  25  are aligned on the same plane. The same applies to the Y2-side surfaces of these components. Thus, there is no step between the first switching fixed contact  15  and the insulation part  51   r  and between the insulation part  51   r  and the second switching fixed contact  25 . Accordingly, the movable contact  4  (contacts  4   p  described later) can move smoothly on the first switching fixed contact  15 , the insulation part  51   r , and the second switching fixed contact  25 . 
     As illustrated in  FIG. 5A , a frame-shaped inner portion of the holding wall  51  includes a first bar  51   t  and a second bar  51   u  are arranged to partition four exposed parts EP (see  FIG. 7 ) to which the resistors R 9  are soldered. 
     As illustrated in  FIG. 4B , the bottom wall  11  of the holding part H 1  includes a base  11   b  that is shaped like a rectangular flat plate and forms the bottom surface of the housing  1 , a pedestal  11   d  inserted into a recess K 1   s  (see  FIG. 6 ) of the case K 1 , and an attaching part  11   t  having a conical trapezoidal shape and formed on the pedestal  11   d.    
     Parts of the terminals T 8  of the metal plate M are embedded in the base  11   b  and the pedestal  11   d  of the bottom wall  11 , and the biasing part  3  is attached to the attaching part  11   t  of the bottom wall  11  as illustrated in  FIG. 3B . 
     The case K 1  of the housing  1  is formed by injection molding of the first synthetic resin material and is shaped like a box having the recess K 1   s  that can house the moving part  2 , the biasing part  3 , and the movable contact  4  illustrated in  FIG. 1 . 
     In the present embodiment, the case K 1  is formed using the same material as the holding part H 1  (bottom wall  11 ) and is bonded to the holding part H 1  by laser welding. This bonding method makes it possible to easily join the holding part H 1  and the case K 1  together, and also makes it possible to increase the adhesion and the bonding strength between the holding part H 1  and the case K 1 . The bonding method can also increase the airtightness between the holding part H 1  and the case K 1 . 
     As illustrated in  FIG. 6 , inside of the recess K 1   s  of the case K 1 , guides K 1   g  for guiding the moving part  2  are provided so that the moving part  2  can be reciprocated in the vertical direction (the Z direction in  FIG. 2 ). 
     Also, as illustrated in  FIG. 1 , a through hole K 1   h , into which an operation shaft  2   j  of the moving part  2  is inserted, is formed in the upper surface of the case K 1 . The operation shaft  2   j  is configured to protrude upward from the through hole K 1   h  of the case K 1 . 
     As illustrated in  FIG. 2A , the cover C 2  for covering the protruding operation shaft  2   j  is disposed above the through hole K 1   h . As illustrated in  FIG. 1 , a groove K 1   m  that engages with a lower part (a flange C 2   v ) of the cover C 2  is provided around the through hole K 1   h . The cover C 2  is hermetically coupled to the groove K 1   m.    
     As described above, the housing  1  is formed by joining the case K 1  and the holding part H 1  together, and the holding wall  51  is disposed in a sealed space formed by the case K 1  and the bottom wall  11 . Thus, the switch  100  is configured such that the holding wall  51  is not exposed out of the housing  1 . 
     Next, the moving part  2  of the switch  100  is described. As illustrated in  FIG. 1 , the moving part  2  of the switch  100  includes an operation base  2   k  that holds the movable contact  4  in the housing  1 , the operation shaft  2   j  protruding from the upper surface of the operation base  2   k , and the operation part  2   t  formed at an end of the operation shaft  2   j . The moving part  2  is configured to move in the vertical direction (in the Z-axis direction) when the operation part  2   t  is pressed by the lever LV. 
     The operation base  2   k  includes a recess  2   r  for housing the movable contact  4 , and a connecting base  4   r  of the movable contact  4  is joined to the ceiling of the recess  2   r  by, for example, swaging. Steps  2   d  protruding outward are formed on the side surfaces of the operation base  2   k . The steps  2   d  engage with the guides K 1   g  (see  FIG. 6 ) provided in the recess K 1   s  of the case K 1  such that the moving part  2  can move in the vertical direction. 
     As illustrated in  FIG. 1 , the operation shaft  2   j  of the moving part  2  has a substantially cylindrical shape. The operation shaft  2   j  is inserted into the through hole K 1   h  of the case K 1  and protrudes upward from the case K 1 . 
     The operation part  2   t  of the moving part  2  is formed at an end of the operation shaft  2   j  and is exposed through the top part of the cover C 2  as illustrated in  FIG. 2A . A joint portion between the operation shaft  2   j  and the operation part  2   t  is indented, and the top part of the cover C 2  is hermetically coupled to the joint portion. The operation part  2   t , which is the tip of the moving part  2 , is pressed by, for example, an actuator (not shown) via the lever LV. The moving part  2  is formed by injection molding of a synthetic resin such as an acrylonitrile butadiene styrene (ABS) copolymer resin, a polycarbonate (PC) resin, or a polyacetal resin (POM, polyoxymethylene). Typically, the operation base  2   k , the operation shaft  2   j , and the operation part  2   t  are formed as a monolithic component. 
     Next, the cover C 2  of the switch  100  is described. The cover C 2  of the switch  100  is formed of a flexible elastic material such as silicone rubber. As illustrated in  FIG. 1 , the cover C 2  includes the flange C 2   v  that is fitted into the groove K 1   m  of the case K 1 , a dome C 2   d  formed seamlessly with the flange C 2   v , and a through hole C 2   h  formed in substantially the center of the dome C 2   d.    
     The cover C 2  is disposed on the upper surface of the case K 1  to cover the through hole K 1   h , the flange C 2   v  is fitted into the groove K 1   m , and the joint portion between the operation shaft  2   j  and the operation part  2   t  is fitted into the through hole C 2   h . With this configuration, the operation part  2   t , which is an end portion of the operation shaft  2   j , is exposed through the through hole C 2   h  of the cover C 2 . The case K 1  may be configured such that the flange C 2   v  can be firmly fixed to the case K 1  by deforming a ring-shaped resin wall provided around the groove K 1   m  of the case K 1  inward with a swage. 
     The dome C 2   d  of the cover C 2  is thin and configured to be smoothly inverted or deformed according to the vertical movement of the operation part  2   t  (the operation shaft  2   j ), and is therefore does not adversely affect the movement of the moving part  2 . With this configuration, the cover C 2  can prevent the entry of, for example, dust and moisture into the interior of the switch  100 . 
     As illustrated in  FIG. 4A , the biasing part  3  of the switch  100  is implemented by a common coil spring. One end of the biasing part  3  is attached to and supported by the attaching part  11   t  of the holding part H 1 , and the other end of the biasing part  3  is in contact with the connecting base  4   r  of the movable contact  4 . Thus, the biasing part  3  is configured to elastically bias the moving part  2  and the movable contact  4  upward. 
     The biasing part  3  is disposed between the common fixed contact G 5  and the first and second switching fixed contacts  15  and  25 . With this arrangement, the biasing part  3  can hold the movable contact  4  in a well-balanced manner, and enables the movable contact  4  to stably contact the common fixed contact G 5 , the first switching fixed contact  15 , and the second switching fixed contact  25 . 
     When the operation part  2   t  is pressed by, for example, an actuator (not shown) via the lever LV, the coil spring used as the biasing part  3  is compressed along with the movement of the moving part  2  and the movable contact  4 . When the pressure on the operation part  2   t  is released, the moving part  2  and the movable contact  4  are pushed upward by the force stored in the compressed coil spring and returned to the initial state. The biasing part  3  may be implemented by a component other than a coil spring as long as the component has a function to return the moving part  2  to the initial state before the operation. For example, the biasing part  3  may be implemented by a leaf spring or a rubber part. 
     As illustrated in  FIG. 4A , the movable contact  4  of the switch  100  is formed by bending an elastic conductive metal plate. Specifically, the movable contact  4  includes the connecting base  4   r  shaped like a flat plate, four elastic arms  4   a  connected to each other via the connecting base  4   r , and contacts  4   p  provided at the ends of the elastic arms  4   a . The conductive metal plate is formed of, for example, copper, iron, or an alloy including copper or iron as a major component. The surface of the metal plate is plated with, for example, nickel or silver. 
     Two of the four elastic arms  4   a  are disposed at one end (the X1 end) of the connecting base  4   r  to face the common fixed contact G 5 , and the other two of the four elastic arms  4   a  are disposed at another end (the X2 end) of the connecting base  4   r  to face the first switching fixed contact  15  and the second switching fixed contact  25 . Each elastic arm  4   a  has a substantially U-shape when seen from the Y2 side, and the end of the elastic arm  4   a  extends upward. 
     In the initial state of the moving part  2  where the operation part  2   t  is not pressed, two of the four contacts  4   p  (first contacts  4   p ) are disposed to contact the common fixed contact G 5 , and the other two of the four contacts  4   p  (second contacts  4   p ) are disposed to contact the first switching fixed contact  15  but not to contact the second switching fixed contact  25 . 
     In a switched state of the moving part  2  where the operation part  2   t  is pressed, the first contacts  4   p  are disposed to contact the common fixed contact G 5 , and the second contacts  4   p  are disposed to contact the second switching fixed contact  25  but not to contact the first switching fixed contact  15 . 
     Next, the metal plate M is described. The metal plate M is formed of, for example, a conductive metal such as iron, copper, or an alloy including iron or copper as a major component. In the present embodiment, the metal plate M is formed of phosphor bronze. The first switching fixed contact  15 , the second switching fixed contact  25 , the common fixed contact G 5 , and the terminals T 8  are formed as parts of the metal plate M. As illustrated in  FIG. 7 , the first switching fixed contact  15 , the second switching fixed contact  25 , and the common fixed contact G 5  are formed by punching one plated metal plate M such that these components become separate contacts. Alternatively, the metal plate M may be plated after being punched. The first switching fixed contact  15 , the second switching fixed contact  25 , and the common fixed contact G 5  are embedded in the holding part H 1  by insert molding before they are separated. Because the first switching fixed contact  15 , the second switching fixed contact  25 , and the common fixed contact G 5  are made from the same metal plate M, they are arranged substantially in the same plane. 
     In the initial state of the moving part  2  where the operation part  2   t  is not pressed, the first switching fixed contact  15  is in contact with the second contacts  4   p  of the movable contact  4 . When the operation part  2   t  is pressed and the moving part  2  changes to the switched state, the second contacts  4   p  move away from the first switching fixed contact  15 . 
     In the initial state of the moving part  2 , the second switching fixed contact  25  is not in contact with the second contacts  4   p . When the operation part  2   t  is pressed and the moving part  2  changes to the switched state, the second contacts  4   p  contact the second switching fixed contact  25 . 
     The common fixed contact G 5  is in contact with the first contacts  4   p  of the movable contact  4  regardless of whether the moving part  2  is in the initial state or the switched state. 
     Specifically, as illustrated in  FIG. 7 , the metal plate M includes a first metal plate M 1 , a second metal plate M 2 , a third metal plate M 3 , and a fourth metal plate M 4 . The first metal plate M 1  includes the common fixed contact G 5  and a common terminal  58  that is one of the terminals T 8 . The second metal plate M 2  includes the second switching fixed contact  25 . The third metal plate M 3  includes a normally-open terminal  18  that is another one of the terminals T 8 . The fourth metal plate M 4  includes the first switching fixed contact  15 . 
     The first metal plate M 1  includes a first exposed part EP 1  to which a first electrode R 9   e   1  (see  FIG. 3B ) of the first resistor R 9   a  is soldered. In  FIG. 7 , the first exposed part EP 1  is surrounded by a bold dotted line. The first exposed part EP 1  is exposed through the frame-shaped inner portion of the holding wall  51  even after the first metal plate M 1  is partially embedded in the holding part H 1  by insert molding. The same applies to a second exposed part EP 2 , a third exposed part EP 3 , and a fourth exposed part EP 4 . 
     The second metal plate M 2  includes the second exposed part EP 2  to which a second electrode R 9   e   2  (see  FIG. 3B ) of the first resistor R 9   a  is soldered and the fourth exposed part EP 4  to which a fourth electrode R 9   e   4  (see  FIG. 3B ) of the second resistor R 9   b  is soldered. 
     The third metal plate M 3  includes the third exposed part EP 3  to which a third electrode R 9   e   3  (see  FIG. 3B ) of the second resistor R 9   b  is soldered. 
     The holding wall  51  of the holding part H 1  is configured to hold each of the first metal plate M 1 , the second metal plate M 2 , and the third metal plate M 3  such that the four exposed parts EP (the first through fourth exposed parts EP 1 -EP 4 ) are exposed. 
     The terminals T 8  are configured to extend downward (in the Z2 direction) from the bottom wall  11 . Specifically, the terminals T 8  includes the normally-open terminal  18  that is electrically connected to the second switching fixed contact  25  via the second resistor R 9   b , and the common terminal  58  that is electrically connected to the second switching fixed contact  25  via the first resistor R 9   a . With this configuration, the normally-open terminal  18  is electrically connected to the common terminal  58  via the first resistor R 9   a  and the second resistor R 9   b.    
     In the present embodiment, each of the exposed parts EP includes an electrode mounting part EA on which the electrode R 9   e  of the resistor R 9  is placed, a soldering part SD on which solder is placed, and a peripheral part CF disposed along the edge of the soldering part SD. In  FIG. 7 , a rectangular area corresponding to the electrode mounting part EA is indicated by a dotted line, a circular area corresponding to the soldering part SD is indicated by a dashed-dotted line, and a U-shaped area corresponding to the peripheral part CF is indicated by dark (fine) dot hatching. 
     Specifically, the first exposed part EP 1  includes a first electrode mounting part EA 1  on which the first electrode R 9   e   1  of the first resistor R 9   a  is placed, a first soldering part SD 1  on which solder for bonding the first electrode R 9   e   1  of the first resistor R 9   a  to the first exposed part EP 1  is placed, and a first peripheral part CF 1  disposed along the edge of the first soldering part SD 1 . The second exposed part EP 2  includes a second electrode mounting part EA 2  on which the second electrode R 9   e   2  of the first resistor R 9   a  is placed, a second soldering part SD 2  on which solder for bonding the second electrode R 9   e   2  of the first resistor R 9   a  to the second exposed part EP 2  is placed, and a second peripheral part CF 2  disposed along the edge of the second soldering part SD 2 . The third exposed part EP 3  includes a third electrode mounting part EA 3  on which the third electrode R 9   e   3  of the second resistor R 9   b  is placed, a third soldering part SD 3  on which solder for bonding the third electrode R 9   e   3  of the second resistor R 9   b  to the third exposed part EP 3  is placed, and a third peripheral part CF 3  disposed along the edge of the third soldering part SD 3 . The fourth exposed part EP 4  includes a fourth electrode mounting part EA 4  on which the fourth electrode R 9   e   4  of the second resistor R 9   b  is placed, a fourth soldering part SD 4  on which solder for bonding the fourth electrode R 9   e   4  of the second resistor R 9   b  to the fourth exposed part EP 4  is placed, and a fourth peripheral part CF 4  disposed along the edge of the fourth soldering part SD 4 . 
     The soldering part SD is disposed to partially overlap the electrode mounting part EA. This arrangement indicates that a portion of the solder placed on the soldering part SD covers a portion of the electrode of the resistor R 9  placed on the electrode mounting part EA. 
     In the present embodiment, the peripheral part CF has a U-shape. Specifically, the peripheral part CF is disposed along the semicircle of the outer side of the substantially circular soldering part SD (i.e., the side of the soldering part SD opposite the side on which the electrode mounting part EA is located). The outer shape of the peripheral part CF substantially corresponds to a part of a concentric circle of the circle indicating the area of the soldering part SD. That is, the peripheral part CF is configured to include a portion that has a shape similar to the outer shape of the soldering part SD such that no portion of the peripheral part CF is distant from the soldering part SD. Typically, the peripheral part CF has a curved shape without any corner. 
     With the U-shaped peripheral part CF, heat supplied to the exposed part EP by laser irradiation during laser soldering can be efficiently transferred to the entire exposed part EP. Thus, this configuration makes it possible to quickly increase the temperature of the entire exposed part EP to a desired temperature and to maintain the desired temperature for a desired time period. This in turn makes it possible to stably and efficiently solder the electrodes of the resistor R 9  to the exposed part EP. 
     Next, the metal plate M is further described with reference to  FIG. 8 .  FIG. 8  is a front view of the same metal plate M illustrated in  FIG. 7 . Different from  FIG. 7 ,  FIG. 8  illustrates the metal plate M such that protruding parts PR also included in the exposed parts EP are distinguishable from connecting parts CP that connect the exposed parts EP to other parts (parts other than the exposed parts EP) of the metal plate M. In  FIG. 8 , a rectangular area corresponding to the electrode mounting part EA is indicated by a dotted line, an area corresponding to the protruding part PR is indicated by a light (coarse) dot hatching, and an area corresponding to the connecting part CP is indicated by dark (fine) dot hatching. 
     Specifically, the first exposed part EP 1  includes a first protruding part PR 1  protruding from the first electrode mounting part EA 1  in a direction (the Z2 direction) away from the second electrode mounting part EA 2 , and the second exposed part EP 2  includes a second protruding part PR 2  protruding from the second electrode mounting part EA 2  in a direction (the Z1 direction) away from the first electrode mounting part EA 1 . The third exposed part EP 3  includes a third protruding part PR 3  protruding from the third electrode mounting part EA 3  in a direction (the Z2 direction) away from the fourth electrode mounting part EA 4 , and the fourth exposed part EP 4  includes a fourth protruding part PR 4  protruding from the fourth electrode mounting part EA 4  in a direction (the Z1 direction) away from the third electrode mounting part EA 3 . 
     The first metal plate M 1  includes a first connecting part CP 1  that connects the first exposed part EP 1  to other parts (another part, or a remaining part) of the first metal plate M 1 . The second metal plate M 2  includes second connecting parts CP 2  that connect the second exposed part EP 2  to other parts (another part, or a remaining part) of the second metal plate M 2 , and fourth connecting parts CP 4  that connect the fourth exposed part EP 4  to other parts (another part, or a remaining part) of the second metal plate M 2 . The third metal plate M 3  includes a third connecting part CP 3  that connects the third exposed part EP 3  to other parts (another part, or a remaining part) of the third metal plate M 3 . 
     In the switch  100 , the first connecting part CP 1  is disposed closer to the second exposed part EP 2  than the first protruding part PR 1 . That is, a distance DS 1  in the Z-axis direction between the second exposed part EP 2  and the first connecting part CP 1  is less than a distance DS 2  in the Z-axis direction between the second exposed part EP 2  and the first protruding part PR 1 . 
     Similarly, the second connecting parts CP 2  are disposed closer to the first exposed part EP 1  than the second protruding part PR 2 , the third connecting part CP 3  is disposed closer to the fourth exposed part EP 4  than the third protruding part PR 3 , and the fourth connecting parts CP 4  are disposed closer to the third exposed part EP 3  than the fourth protruding part PR 4 . 
     In other words, the first protruding part PR 1  protrudes in a direction away from the first connecting part CP 1 , the second protruding part PR 2  protrudes in a direction away from the second connecting parts CP 2 , the third protruding part PR 3  protrudes in a direction away from the third connecting part CP 3 , and the fourth protruding part PR 4  protrudes in a direction away from the fourth connecting parts CP 4 . Also, the first protruding part PR 1  and the second protruding part PR 2  protrude in directions away from each other, and the third protruding part PR 3  and the fourth protruding part PR 4  protrude in directions away from each other. 
     The first exposed part EP 1  and the second exposed part EP 2  are preferably arranged symmetrically with respect to the first resistor R 9   a  used as an electronic component, and the third exposed part EP 3  and the fourth exposed part EP 4  are preferably arranged symmetrically with respect to the second resistor R 9   b  used as an electronic component. This arrangement makes it possible to prevent a so-called Manhattan effect where one of two soldered joints is pulled apart from the exposed part EP and one end of the electronic component is lifted due to the tension of the other one of the two soldered joints resulting from unbalanced melting of solder at the two soldered joints, and also makes it possible to suppress damage on the electronic component or the holding part H 1  that is caused by the reflection of a laser beam from the surface of the exposed part EP. 
       FIG. 9  is a drawing illustrating an example of a configuration of a laser soldering device DV used for laser soldering.  FIG. 9  illustrates a state where the soldering of the first electrode R 9   e   1  of the first resistor R 9   a  to the first exposed part EP 1  and the soldering of the second electrode R 9   e   2  of the first resistor R 9   a  to the second exposed part EP 2  are performed simultaneously by the laser soldering device DV. Specifically, the laser soldering device DV irradiates a solder paste HDP 1  applied to a portion of the first exposed part EP 1  and a portion of the first electrode R 9   e   1  with a laser beam LS 1  while irradiating a solder paste HDP 2  applied to a portion of the second exposed part EP 2  and a portion of the second electrode R 9   e   2  with a laser beam LS 2 . The power of the laser beam LS 1  is the same as the power of the laser beam LS 2 . As described above, the first exposed part EP 1  and the second exposed part EP 2  are arranged symmetrically. The same applies to the positional relationship between the first electrode R 9   e   1  and the second electrode R 9   e   2  of the first resistor R 9   a , the positional relationship between the solder paste HDP 1  and the solder paste HDP 2 , and the positional relationship between a circular spot of the laser beam LS 1  and a circular spot of the laser beam LS 2 . Therefore, the manner in which heat supplied by the irradiation of the laser beam LS 1  is transferred through the first exposed part EP 1  is substantially the same as the manner in which heat supplied by irradiation of the laser beam LS 2  is transferred through the second exposed part EP 2 . That is, the laser soldering device DV can melt the solder contained in the solder paste HDP 1  and the solder contained in the solder paste HDP 2  at the same timing and in the same manner. Thus, with the laser soldering device DV, the substantially circular shape of the solder can be maintained even after the solder is melted. Also, the laser soldering device DV can suppress the movement (displacement) of the first resistor R 9   a  caused by the melted solder, and thereby suppress or prevent the occurrence of the Manhattan effect. Further, the laser soldering device DV can suppress the unbalanced melting of the solder and thereby suppress or prevent the surface (coating) of the exposed part EP covered with the solder paste HDP from being exposed. This in turn makes it possible to suppress or prevent the electronic component or the holding part H 1  from being damaged by the laser beam reflected from the surface of the exposed part EP. 
     Thus, the exposed part EP has such a shape that the heat supplied by laser irradiation (or heat stored in the exposed part EP) is less likely to escape from the exposed part EP. 
     In the present embodiment, the connecting part CP is positioned as far as possible from the exposed part EP where heat is to be stored. Specifically, the first connecting part CP 1  is positioned closer to the second exposed part EP 2  than the first protruding part PR 1 . More specifically, the first connecting part CP 1  is disposed on the X1 side of the first electrode mounting part EA 1 . However, the first connecting part CP 1  may instead be disposed on the X2 side or the Z1 side of the first electrode mounting part EA 1 . 
     The second connecting parts CP 2  are positioned closer to the first exposed part EP 1  than the second protruding part PR 2 . More specifically, the second connecting parts CP 2  are disposed on the X1 side and the X2 side of the second electrode mounting part EA 2 . However, the second connecting part(s) CP 2  may instead be disposed on the Z2 side of the second electrode mounting part EA 2 . 
     The third connecting part CP 3  is positioned closer to the fourth exposed part EP 4  than the third protruding part PR 3 . More specifically, the third connecting part CP 3  is disposed on the X2 side of the third electrode mounting part EA 3 . However, the third connecting part CP 3  may instead be disposed on the X1 side or the Z1 side of the third electrode mounting part EA 3 . 
     The fourth connecting parts CP 4  are positioned closer to the third exposed part EP 3  than the fourth protruding part PR 4 . More specifically, the fourth connecting parts CP 4  are disposed on the X1 side and the X2 side of the fourth electrode mounting part EA 4 . However, the fourth connecting part(s) CP 4  may instead be disposed on the Z2 side of the fourth electrode mounting part EA 4 . 
     The first exposed part EP 1  is connected to the other parts only via the first connecting part CP 1 . In the present embodiment, the third exposed part EP 3  is connected to the other parts only via the third connecting part CP 3 . The width of the connecting part CP is less than the width of the exposed part EP. Also, the width of the connecting part CP is less than the diameter of the soldering part SD (see  FIG. 7 ). 
     Different from a case where an electronic component is soldered to a printed circuit board, when two electrodes of the resistor R 9  used as an electronic component are soldered simultaneously to the metal plate M having a high thermal conductivity as in the present embodiment, it is important to control the manner of heat transfer in the metal plate M and the temperature distribution in the metal plate M. In the present embodiment, the U-shaped peripheral part CF is provided in the exposed part EP of the metal plate M so that heat is transferred in the exposed part EP in a desired manner and a desired temperature distribution is achieved in the exposed part EP. 
     Effects of the U-shaped peripheral part CF are described in detail with reference to  FIGS. 10A and 10B .  FIG. 10A  is an enlarged view of the third exposed part EP 3  including the U-shaped third peripheral part CF 3 , and  FIG. 10B  is an enlarged view of a third exposed part EP 3   x  including a third peripheral part CF 3   x  with a square-bracket shape. The outer edge of the third peripheral part CF 3  has a curved shape including curved parts RP (a first curved part RP 1  and a second curved part RP 2 ). On the other hand, the outer edge of the third peripheral part CF 3   x  has an angular shape including corners CN (a first corner CN 1  and a second corner CN 2 ). 
       FIG. 10A  illustrates the temperature distribution in the third exposed part EP 3  observed when the third exposed part EP 3  is irradiated with a laser beam whose spot center is at a center point CT for a predetermined time period, and  FIG. 10B  illustrates the temperature distribution in the third exposed part EP 3   x  observed when the third exposed part EP 3   x  is irradiated with a laser beam whose spot center is at a center point CT for the predetermined time period. In  FIGS. 10A and 10B , the temperature distribution is indicated by differences in the density (or fineness) of the dot hatching. The darker (or finer) hatching indicates a higher temperature. 
     The temperature distribution of the third exposed part EP 3  is described below. However, the descriptions below also apply to the first exposed part EP 1 , the second exposed part EP 2 , and the fourth exposed part EP 4 . 
     As is apparent from  FIGS. 10A and 10B , the temperature of the third exposed part EP 3  is higher than the temperature of the third exposed part EP 3   x . Specifically, in  FIG. 10A , the temperature at the center point CT is 230 degrees Celsius, the temperature at an edge point ED is 214 degrees Celsius, and the temperature at a point NC on the third connecting part CP 3  is 204 degrees Celsius. On the other hand, in  FIG. 10B , the temperature at the center point CT is 223 degrees Celsius, the temperature at an edge point ED is 202 degrees Celsius, and the temperature at a point NC on the third connecting part CP 3  is 197 degrees Celsius. 
     The differences in temperature are due to the presence or absence of the corners CN. As illustrated in  FIG. 10A , in the case of the third exposed part EP 3  that does not include the corners CN, heat supplied by laser irradiation is not transferred to the corners CN. On the other hand, as illustrated in  FIG. 10B , in the case of the third exposed part EP 3   x  having the corners CN, heat supplied by laser irradiation is transferred also to the corners CN. For this reason, the size of a portion of the third exposed part EP 3   x  with a relatively high temperature (i.e., the portion with the darkest dot hatching) is significantly smaller than the size of a portion of the third exposed part EP 3  with a relatively high temperature (i.e., the portion with the darkest dot hatching). That is, in the third exposed part EP 3   x , because the heat supplied by laser irradiation is unnecessarily transferred to the corners CN, the temperature of the third soldering part SD 3  (see  FIG. 7 ), which needs to be maintained at a high temperature, becomes lower than the temperature of the third soldering part SD 3  of the third exposed part EP 3 . 
     Also, with the third exposed part EP 3   x  that includes the corners CN as illustrated in  FIG. 10B , molten solder flows into the corners CN, and the surface of the third exposed part EP 3   x  that needs to be covered by the solder may be exposed. On the other hand, with the third exposed part EP 3  that does not include the corners CN as illustrated in  FIG. 10A , the molten solder does not flow into the corners CN, and the surface of the third exposed part EP 3  that needs to be covered by the solder is not exposed. For the above reasons, the configuration of the third exposed part EP 3  can suppress or prevent the surface (or coating) of the third exposed part EP 3 , which needs to be covered with solder, from being exposed. This in turn makes it possible to suppress or prevent an electronic component or the holding part H 1  from being damaged by a laser beam reflected from the surface of the third exposed part EP. 
     Thus, compared with the configuration of the third exposed part EP 3   x  including the corners CN, the configuration of the third exposed part EP 3  including the third peripheral part CF 3  having a shape formed by removing the corners CN makes it possible to efficiently supply heat to the third soldering part SD 3  and maintain the third soldering part SD 3  at a relatively high temperature. Also, compared with the configuration of the third exposed part EP 3   x , the configuration of the third exposed part EP 3  can suppress or prevent the surface of the third exposed part EP 3   x , which needs to be covered with solder, from undesirably being exposed. That is, compared with the configuration of the third exposed part EP 3   x , the configuration of the third exposed part EP 3  can suppress or prevent an unbalanced change of the shape of molten solder. Therefore, the configuration of the third exposed part EP 3  having a curved shape including the curved parts RP makes it possible to stably solder the third electrode R 9   e   3  of the second resistor R 9   b  to the third exposed part EP 3 . Also, because the third exposed part EP 3  has a shape formed by removing the corners CN, it is possible to prevent the amount of molten solder flowing toward the left side (X2 side) of the third electrode R 9   e   3  of the second resistor R 9   b  from being greatly different from the amount of molten solder flowing toward the right side (X1 side) of the third electrode R 9   e   3 . Accordingly, the configuration of the third exposed part EP 3  makes it possible to prevent the second resistor R 9   b  from being moved due to the difference in tension between the molten solder on the right side and the molten solder on the left side of the third electrode R 9   e   3 . 
     As described above, the metal plate M is held by the holding wall  51  such that the exposed parts EP are exposed through the frame-shaped inner portion of the holding wall  51 . When the electrodes of the resistors R 9  are placed on and soldered to the exposed parts EP, laser soldering is used instead of reflow soldering. Therefore, it is not necessary to place the holding part H 1 , in which the metal plate M is embedded and held, in a reflow furnace. Accordingly, the holding part H 1  can be formed of, for example, a first synthetic resin material that is less expensive than a synthetic resin material that has a heat resistance property to withstand a reflow temperature. 
     In the switch  100 , as illustrated in  FIG. 2B , the entire perimeter of the base of the terminal T 8  is surrounded by the first synthetic resin material forming the bottom wall  11 . That is, the switch  100  is configured such that the entire perimeter of the base of the terminal T 8  is in close contact with the bottom wall  11 . This configuration makes it possible to prevent, for example, water from entering the switch  100  through a gap between the terminal T 8  and the bottom wall  11 . Further, the switch  100  is configured such that the holding wall  51  is disposed in an enclosed space formed by the case K 1  and the bottom wall  11 . This configuration also improves the waterproof property. 
     In the present embodiment, the resistors R 9  are implemented by inexpensive general-purpose chip resistors. Also, the first resistor R 9   a  and the second resistor R 9   b  are selected to have different resistance values. The first electrode R 9   e   1  of the first resistor R 9   a  is bonded to the first exposed part EP 1  by laser soldering, and the second electrode R 9   e   2  of the first resistor R 9   a  is bonded to the second exposed part EP 2  by laser soldering. As a result, the second switching fixed contact  25  and the common terminal  58 , which are separate from each other, are electrically connected to each other via the first resistor R 9   a . The third electrode R 9   e   3  of the second resistor R 9   b  is bonded to the third exposed part EP 3  by laser soldering, and the fourth electrode R 9   e   4  of the second resistor R 9   b  is bonded to the fourth exposed part EP 4  by laser soldering. As a result, the second switching fixed contact  25  and the normally-open terminal  18 , which are separate from each other, are electrically connected to each other via the second resistor R 9   b . The resistors R 9  may also be implemented by electronic components other than chip resistors, such as substrates on which carbon resistors are printed. 
     Next, a detection circuit of the switch  100  is described.  FIG. 11  is a diagram of a detection circuit of the switch  100 .  FIG. 11  illustrates a state of the detection circuit while the moving part  2  is in the initial state. 
     In the detection circuit of the switch  100 , as illustrated in  FIG. 11 , the common fixed contact G 5  connected to the common terminal  58  via the first metal plate M 1  is connected to the first switching fixed contact  15  via the movable contact  4  when the moving part  2  is in the initial state. In the present embodiment, the first switching fixed contact  15  is a dummy contact that is not in contact with other parts. The common terminal  58  is connected to the normally-open terminal  18  via the first resistor R 9   a  and the second resistor R 9   b . One end of the first resistor R 9   a  is connected to the first exposed part EP 1  of the first metal plate M 1 , and the other end of the first resistor R 9   a  is connected to the second exposed part EP 2  of the second metal plate M 2 . Also, one end of the second resistor R 9   b  is connected to the third exposed part EP 3  of the third metal plate M 3 , and the other end of the second resistor R 9   b  is connected to the fourth exposed part EP 4  of the second metal plate M 2 . 
     When the moving part  2  is in the initial state, the second switching fixed contact  25  is not connected to the common fixed contact G 5  via the movable contact  4 , but is connected to the common terminal  58  via the first resistor R 9   a  and connected to the normally-open terminal  18  via the second resistor R 9   b.    
     When the operation part  2   t  is pressed, the movable contact  4  moves along with the movement of the moving part  2  and is connected to the second switching fixed contact  25 . That is, the moving part  2  changes to the switched state. Then, when the pressure on the operation part  2   t  is released, the moving part  2  is pushed by the biasing part  3  back to the initial state. Thus, the moving part  2  is configured to be switched between the initial state and the switched state. 
     In the detection circuit of  FIG. 11 , when the moving part  2  is in the initial state, a combined resistance value, which is the sum of the resistance value of the first resistor R 9   a  and the resistance value of the second resistor R 9   b , is detected between the normally-open terminal  18  and the common terminal  58 . On the other hand, when the moving part  2  is in the switched state, only the resistance value of the second resistor R 9   b  is detected between the normally-open terminal  18  and the common terminal  58 . The On and Off of the switch  100  are determined based on the difference between the detected resistance values. 
     When, for example, an electric wire of an external device connected to the detection circuit is in an abnormal state (a disconnected state), the voltage from the external device is not applied to the common terminal  58  regardless of whether the moving part  2  is in the initial state or the switched state. In this case, the resistance value of the detection circuit from the viewpoint of the external device becomes infinite. On the other hand, when, for example, the electric wire of the external device is short-circuited, the power supply voltage supplied to the external device is applied to the common terminal  58  regardless of whether the moving part  2  is in the initial state or the switched state. That is, the resistance value of the detection circuit from the viewpoint of the external device becomes zero. 
     When, for example, the electric wire of the external device connected to the detection circuit is in a normal state, different voltages are applied to the common terminal  58  depending on the connection states of the movable contact  4 . That is, when the moving part  2  is in the initial state, a voltage corresponding to a combined resistance value determined by the resistance value of the first resistor R 9   a , the resistance value of the second resistor R 9   b , and the resistance value of the external device is applied to the common terminal  58 ; and when the moving part  2  is in the switched state, a voltage corresponding to a combined resistance value determined by the resistance value of the second resistor R 9   b  and the resistance value of the external device is applied to the common terminal  58 . Accordingly, by detecting the voltage value (the resistance value) of the detection circuit, the switch  100  can determine whether the connection between the external device and the electric wire is in a normal state or an abnormal state. 
     Effects of the switch  100  configured as described above are summarized. First, in the switch  100 , because the resistors R 9  are mounted on the metal plate M by laser soldering, the holding part H 1  holding the metal plate M including the first through fourth exposed parts EP 1 -EP 4  is formed of the first synthetic resin material that is a thermoplastic synthetic resin material having a heat distortion temperature lower than the reflow temperature. For this reason, compared with a case where the holding part H 1  is formed of a thermoplastic resin material having a heat distortion temperature higher than the reflow temperature, the switch  100  can be manufactured at a lower cost. 
     Also, in the switch  100 , because both of the holding part H 1  and the case K 1  are formed of the first synthetic resin material, laser welding can be used to bond the holding part H 1  (the bottom wall  11 ) to the case K 1 . Therefore, the holding part H 1  and the case K 1  can be easily joined together. This in turn makes it possible to further reduce the manufacturing cost of the switch  100 . Further, using laser welding makes it possible to increase the adhesion and the bonding strength between the holding part H 1  and the case K 1 . This in turn makes it possible to improve the airtightness between the holding part H 1  and the case K 1  of the switch  100 . 
     The detection circuit of  FIG. 11  is configured such that the first switching fixed contact  15  serves as a dummy contact. However, the detection circuit may also be configured such that the second switching fixed contact  25  serves as a dummy contact. 
     Next, a method of manufacturing the switch  100  is described.  FIG. 12  is a flowchart illustrating a process of manufacturing the switch  100 .  FIGS. 13A and 13B  are front views of a frame  10  (or the metal plate M) before and after a frame preparation step p 1 . Specifically,  FIG. 13A  is a front view of the frame  10  before the frame preparation step P 1  is started, and  FIG. 13B  is a front view of the frame  10  when the frame preparation step P 1  is completed.  FIG. 14  is a front view of the frame  10  that is partially embedded in the holding part H 1  formed in a molding step P 2 .  FIG. 15  is a front view of the frame  10  to which solder is applied in a solder applying step P 31  of a resistor mounting step P 3 .  FIGS. 16A and 16B  are front views of the frame  10  on which the resistors R 9  are mounted in the resistor mounting step P 3 . Specifically,  FIG. 16A  is a front view of the frame  10  on which the resistors R 9  are mounted in a resistor mount step P 32  of the resistor mounting step P 3 .  FIG. 16B  is a front view of the frame  10  when a laser soldering step P 33  of the resistor mounting step P 3  is completed. In  FIGS. 13A through 16B , for clarity, the frame  10  is illustrated as a separate component for manufacturing one switch  100 . However, the frame  10  may be a hoop-like frame where multiple frames are continuously connected to each other to form a band. 
     As illustrated in  FIG. 12 , the method of manufacturing the switch  100  includes the frame preparation step P 1  of preparing the frame  10  in which the first through fourth metal plates M 1 -M 4  (see  FIG. 7 ) are connected to each other via connecting parts  10   r  (see  FIG. 13B ), the molding step P 2  of forming the holding part H 1  (see  FIG. 14 ), the resistor mounting step P 3  of soldering the resistors R 9  (see  FIG. 15  and  FIGS. 16A and 16B ), a cutting step P 4  of cutting the connecting parts  10   r  (see  FIG. 16B ), an assembling step P 5  of assembling components, and a bonding step S 6  of bonding the holding part H 1  to the case K 1  after the assembling step P 5 . 
     In the frame preparation step P 1 , as illustrated in  FIG. 13A , a conductive metal plate, which is formed of iron, copper, or an alloy including iron or copper as a major component, is prepared. The metal plate is then punched using a metal die. Accordingly, in the frame preparation step P 1 , as illustrated in  FIG. 13B , the frame  10  where the first through fourth metal plates M 1 -M 4  (see  FIG. 7 ) are connected to each other via the connecting parts  10   r  is prepared. 
     In the molding step P 2 , as illustrated in  FIG. 14 , the holding part H 1  is formed by insert molding such that the frame  10  is partially embedded in the first synthetic resin material. Specifically, the frame-shaped holding wall  51  is formed such that the surfaces of the first through fourth exposed parts EP 1 -EP 4  are exposed through the inner portion of the holding wall  51 . Also, the holding wall  51  is formed such that the surfaces of the first switching fixed contact  15  and the second switching fixed contact  25  are exposed outside of the frame-shaped holding wall  51 . Further, the holding wall  51  is formed such that the insulation part  51   r  is disposed between the first switching fixed contact  15  and the second switching fixed contact  25 . 
     The holding wall  51  can be easily formed by insert molding the frame  10  using the first synthetic resin material. When a thermoplastic resin such as a polybutylene terephthalate (PBT) resin containing glass fibers and having a heat distortion temperature between about 120 and about 220 degrees Celsius is used as the first synthetic resin material, the holding part H 1  is formed by injection molding. 
     As illustrated in  FIG. 12 , the resistor mounting step P 3  includes the solder applying step P 31  where solder is applied to the exposed parts EP, the resistor mount step P 32  where the resistors R 9  are placed on the solder applied to the exposed parts EP, and the laser soldering step P 33  where the resistors R 9  are soldered to the exposed parts EP. 
     In the solder applying step P 31 , as illustrated in  FIG. 15 , a solder paste HDP is applied to a portion of each of the exposed parts EP. In  FIG. 15 , the solder paste HDP is indicated by rough cross-hatching. Specifically, the solder paste HDP is applied to a portion of the first exposed part EP 1 , a portion of the second exposed part EP 2 , a portion of the third exposed part EP 3 , and a portion of the fourth exposed part EP 4 . The solder paste HDP is preferably applied using a dispenser. 
     In the resistor mount step P 32 , as illustrated in  FIG. 16A , the first resistor R 9   a  and the second resistor R 9   b  are placed on the exposed parts EP held by the holding wall  51 . Specifically, the first resistor R 9   a  is disposed such that the first electrode R 9   e   1  contacts the first exposed part EP 1  via the solder paste and the second electrode R 9   e   2  contacts the second exposed part EP 2  via the solder paste. Similarly, the second resistor R 9   b  is disposed such that the third electrode R 9   e   3  contacts the third exposed part EP 3  via the solder paste and the fourth electrode R 9   e   4  contacts the fourth exposed part EP 4  via the solder paste. The first resistor R 9   a  and the second resistor R 9   b  are preferably placed on the exposed parts EP using a surface mounter. 
     In the laser soldering step P 33 , a laser beam is emitted toward the solder paste HDP applied to adhere to a portion of each exposed part EP and a portion of an electrode of the corresponding resistor R 9  to heat the solder paste HDP. As a result, as illustrated in  FIG. 16B , the resistors R 9  are soldered and bonded to the exposed parts EP. In  FIG. 16B , solder MS solidified after being heated and melted by laser irradiation is indicated by fine cross-hatching. 
     The above-described manufacturing method does not include a step such as a reflow soldering step where the holding part H 1  is exposed to a high temperature. Therefore, the first synthetic resin material having a heat distortion temperature lower than the reflow temperature can be used as the synthetic resin material for forming the holding part H 1 . This in turn makes it possible to form the switch  100  using a low-price synthetic resin material that does not necessarily withstand the reflow temperature and thereby makes it possible to reduce the manufacturing cost. 
     In the cutting step P 4 , the frame  10  is cut at positions indicated by dotted lines CL illustrated in  FIG. 16B  by, for example, pressing, and components of the switch  100  are detached from the connecting parts  10   r  of the frame  10 . Specifically, the holding part H 1 , in which the metal plate M including the first switching fixed contact  15 , the normally-open terminal  18 , the second switching fixed contact  25 , the common terminal  58 , and the common fixed contact G 5  is embedded, is separated as a composite component from the rest of the frame  10 . 
     Also in the cutting step P 4 , the normally-open terminal  18  and the common terminal  58  are bent at positions indicated by dashed-dotted lines BL in  FIG. 16B  by, for example, a bending process such that the normally-open terminal  18  and the common terminal  58  extend in a desired direction. 
     Because the frame  10  prepared in the frame preparation step P 1  is used until the cutting step P 4  is completed, the insert molding at the molding step P 2  and the soldering at the resistor mounting step P 3  can be easily performed. 
     In the assembling step P 5 , as illustrated in  FIG. 12 , the composite component detached from the frame  10  at the cutting step P 4 , the movable contact  4  prepared at a movable contact preparation step j 1 , the moving part  2  prepared at a moving part preparation step j 2 , the biasing part  3  prepared at a biasing part preparation step j 3 , the case K 1  prepared at a case preparation step j 4 , and the cover C 2  prepared at a cover preparation step j 5  are assembled together. 
     Specifically, one end of the coil spring used as the biasing part  3  is attached to the attaching part  11   t  of the bottom wall  11  of the composite component. Next, the movable contact  4  is placed in the recess  2   r  of the moving part  2 , and the connecting base  4   r  of the movable contact  4  is joined to the ceiling of the recess  2   r  by, for example, swaging. Then, the other end of the coil spring (biasing part  3 ) is positioned to contact the connecting base  4   r . Here, the connecting base  4   r  is combined with the composite component such that a pair of elastic arms  4   a  (second contacts  4   p ) provided at one end of the connecting base  4   r  sandwich the first switching fixed contact  15 , and another pair of elastic arms  4   a  (first contacts  4   p ) provided at the other end of the connecting base  4   r  sandwich the common fixed contact G 5 . 
     Then, the case K 1  is combined with the holding part H 1  to cover the upper side (Z1 side) of the holding part H 1 . At this step, the moving part  2  is combined with the case K 1  such that the operation shaft  2   j  passes through the through hole K 1   h  of the case K 1  and protrudes upward from the case K 1 . 
     In the case preparation step j 4 , the case K 1  is produced using the first synthetic resin material that is also used to produce the holding part H 1 . This is because neither the holding part H 1  nor the case K 1  is exposed to a high temperature such as a reflow temperature. Thus, in the switch  100 , the case K 1  is formed of a thermoplastic synthetic resin material having a heat distortion temperature lower than the reflow temperature. Therefore, compared with a case where the case K 1  is formed of a synthetic resin material having a heat distortion temperature higher than the reflow temperature, the present embodiment makes it possible to reduce the manufacturing cost of the switch  100 . 
     Then, in the assembling step P 5 , the cover C 2  is combined with the operation shaft  2   j  protruding upward from the case K 1 . The cover C 2  is disposed on the upper surface of the case K 1  to cover the through hole K 1   h  of the case K 1 . At this step, the flange C 2   v  of the cover C 2  is fitted into the groove K 1   m  of the case K 1 , and the joint portion between the operation shaft  2   j  and the operation part  2   t  is fitted into the through hole C 2   h . To firmly fix the flange C 2   v  to the case K 1 , the ring-shaped resin wall provided around the groove K 1   m  of the case K 1  may be deformed inward with a swage, or an adhesive may be applied to a position between the flange C 2   v  and the resin wall. 
     Then, in the bonding step P 6 , the bottom wall  11  of the holding part H 1  and the case K 1  are bonded together. This step makes it possible to easily join the holding part H 1  (the bottom wall  11 ) and the case K 1  together, and also makes it possible to increase the adhesion and the bonding strength between the holding part H 1  and the case K 1 . When the holding part H 1  and the case K 1  are formed of the same material (the first synthetic resin material) as in the present embodiment, the adhesion and the bonding strength between the holding part H 1  and the case K 1  are further increased. Also, improving the adhesion and the bonding strength between the holding part H 1  and the case K 1  can improve the airtightness of the housing  1 . 
     The above-described method of manufacturing the switch  100  has the following effects. In the method of manufacturing the switch  100 , the reflow soldering is not used. Therefore, in the molding step p 2 , the holding part H 1  is formed with the first synthetic resin material having a heat distortion temperature lower than the reflow temperature. That is, it is not necessary to use expensive synthetic resin materials having a heat resistance property. In other words, the switch  100  can be manufactured using a relatively inexpensive synthetic resin material. 
     Also, in the method of manufacturing the switch  100 , because the holding part H 1  and the case K 1  are formed of the same material, laser welding can be used to bond the holding part H 1  (the bottom wall  11 ) to the case K 1 . Therefore, the holding part H 1  and the case K 1  can be easily joined together. Further, the airtightness of the housing  1  can be improved by increasing the adhesion and the bonding strength between the holding part H 1  and the case K 1  with a simple configuration. This in turn makes it possible to further reduce the manufacturing cost of the switch  100 . 
     Further, in the method of manufacturing the switch  100 , because laser soldering is used in the laser soldering step P 33  of the resistor mounting step P 3 , the resistors R 9  can be easily and reliably soldered to the exposed parts EP of the metal plate M. 
     In the molding step P 2 , the bottom wall  11  is formed such that the first synthetic resin material surrounds the entire perimeter of the base of the terminal T 8 , and the bottom wall  11  closely contacts the terminal T 8 . This configuration makes it possible to prevent, for example, water from entering the switch  100  through a gap between the terminal T 8  and the bottom wall  11 . 
     In the method of manufacturing the switch  100 , the frame  10  prepared at the frame preparation step P 1  is used from the molding step P 2  to the cutting step P 4 . This makes it easier to perform the insert molding at the molding step P 2 , the soldering at the resistor mounting step P 3 , and the detaching of the composite component at the cutting step P 4 . This in turn improves the manufacturing efficiency of the switch  100 . 
     As described above, the switch  100  of the present embodiment includes the switching mechanism MC that is housed in the housing  1  and configured to switch the state of connection between the normally-open terminal  18  and the common terminal  58  (at least two terminals) exposed out of the housing  1  by using the common fixed contact G 5  (common contact) and the first switching fixed contact  15  and the second switching fixed contact  25  (two switching contacts), and the resistors R 9  that are disposed in the housing  1  and used as electronic components for electrically connecting the normally-open terminal  18  and the common terminal  58 . 
     As exemplified in  FIG. 7 , the switching mechanism MC includes the first metal plate M 1  that is connected to the common fixed contact G 5 , which is an example of a first contact that is one of the common contact and the two switching contacts, and includes the first exposed part EP 1  to which the first electrode R 9   e   1  of the first resistor R 9   a  is soldered by laser irradiation; and the second metal plate M 2  that is connected to the second switching fixed contact  25 , which is an example of a second contact that is another one of the common contact and the two switching contacts, and includes the second exposed part EP 2  to which the second electrode R 9   e   2  of the first resistor R 9   a  is soldered by laser irradiation. 
     The first exposed part EP 1  includes the first electrode mounting part EA 1  on which the first electrode R 9   e   1  is placed, the first soldering part SD 1  on which solder is placed, and the first peripheral part CF 1  disposed along the edge of the first soldering part SD 1 . The second exposed part EP 2  includes the second electrode mounting part EA 2  on which the second electrode R 9   e   2  is placed, the second soldering part SD 2  on which solder is placed, and the second peripheral part CF 2  disposed along the edge of the second soldering part SD 2 . Each of the first peripheral part CF 1  and the second peripheral part CF 2  has a U-shape. 
     From a different viewpoint, as illustrated in  FIG. 8 , the first exposed part EP 1  includes the first electrode mounting part EA 1  on which the first electrode R 9   e   1  is placed, and the second exposed part EP 2  includes the second electrode mounting part EA 2  on which the second electrode R 9   e   2  is placed. The first exposed part EP 1  further includes the first protruding part PR 1  protruding from the first electrode mounting part EA 1  in a direction away from the second electrode mounting part EA 2 , and the second exposed part EP 2  further includes the second protruding part PR 2  protruding from the second electrode mounting part EA 2  in a direction away from the first electrode mounting part EA 1 . The first connecting part CP 1 , which connects the first exposed part EP 1  of the first metal plate M 1  to other parts of the first metal plate M 1 , is positioned closer to the second exposed part EP 2  than the first protruding part PR 1 ; and the second connecting parts CP 2 , which connect the second exposed part EP 2  of the second metal plate M 2  to other parts of the second metal plate M 2 , are positioned closer to the first exposed part EP 1  than the second protruding part PR 2 . 
     With the above configuration and arrangement, each of the exposed parts EP can be appropriately heated during laser soldering. That is, with the above configuration, heat is less likely to escape from the exposed part EP to other parts during laser soldering. 
     Thus, the above configuration of the switch  100  makes it possible to properly bond the first resistor R 9   a  between the first metal plate M 1  and the second metal plate M 2  by laser soldering. Compared with a case where the first resistor R 9   a  is bonded between the first metal plate M 1  and the second metal plate M 2  by a method such as reflow soldering in which the housing  1  is exposed to a temperature higher than the temperature in the laser soldering, the present embodiment can reduce the manufacturing cost of the switch  100 . This is because the housing  1  can be molded using a relatively inexpensive synthetic resin material with a low heat distortion temperature. 
     Similarly to the third peripheral part CF 3  illustrated in  FIG. 10A , the first peripheral part CF 1  preferably includes curved parts RP. This configuration of the first peripheral part CF 1  of the first exposed part EP 1  makes it possible to suppress heat supplied by laser radiation for laser soldering from diffusing from the soldering part SD. Accordingly, the soldering part SD can be quickly heated to a temperature suitable for soldering and can be maintained at the temperature suitable for soldering for an appropriate time period. This in turn makes it possible to reliably bond the first resistor R 9   a  to the first metal plate M 1  and the second metal plate M 2  by laser soldering. However, the first peripheral part CF 1  may instead be configured to include corners CN similarly to those of the third peripheral part CF 3   x  illustrated in  FIG. 10B . 
     As illustrated in  FIG. 7 , the first exposed part EP 1  and the second exposed part EP 2  are preferably arranged symmetrically with respect to the first resistor R 9   a . For example, this arrangement suppresses or prevents the occurrence of the Manhattan effect and damage on an electronic component or the holding part H 1  due to the reflection of a laser beam from the surface of the exposed part EP. This is because when laser soldering is performed as illustrated in  FIG. 9 , the above arrangement makes it possible to melt the solder contained in the solder paste HDP 1  and the solder contained in the solder paste HDP 2  at the same timing and in the same manner. 
     The first exposed part EP 1  of the first metal plate M 1  may be a component different from other parts (another part, or a remaining part) of the first metal plate M 1 , and the second exposed part EP 2  of the second metal plate M 2  may be a component different from other parts (another part, or a remaining part) of the second metal plate M 2 . For example, the first exposed part EP 1  and the other parts (another part, or a remaining part) of the first metal plate M 1  may be formed of different materials, and the second exposed part EP 2  and the other parts (another part, or a remaining part) of the second metal plate M 2  may be formed of different materials. Specifically, the first exposed part EP 1  and the other parts of the first metal plate M 1  may be formed of different types of metals. Alternatively, the other parts may include portions formed of materials other than metals. This configuration makes it possible to make heat less likely to escape from the first exposed part EP 1  to the other parts during laser soldering. This is because the transfer of heat from the first exposed part EP 1  to the other parts is suppressed. 
     Alternatively, the first exposed part EP 1  of the first metal plate M 1  and the other parts (another part, or a remaining part) of the first metal plate M 1  may be formed monolithically (as a single component) with the same material, and the second exposed part EP 2  of the second metal plate M 2  and the other parts (another part, or a remaining part) of the second metal plate M 2  may be formed monolithically (as a single component) with the same material. For example, this configuration makes it possible to easily form the first metal plate M 1  including the first exposed part EP 1 , the common fixed contact G 5 , and the common terminal  58  by a method such as punching. 
     The housing  1  is preferably configured to include the case K 1  and the holding part H 1  for holding the first metal plate M 1  and the second metal plate M 2 . The holding part H 1  is preferably formed of a material having a heat distortion temperature lower than the reflow temperature. Compared with the case where the first resistor R 9   a  is bonded to the first metal plate M 1  and the second metal plate M 2  by reflow soldering, this configuration can reduce the manufacturing cost of the switch  100 . This is because the housing  1  can be molded using a relatively inexpensive synthetic resin material with a heat distortion temperature lower than the reflow temperature. 
     A method of manufacturing the switch  100  according to the present embodiment includes a step of soldering the first electrode R 9   e   1  of the first resistor R 9   a  (which is an example of an electronic component) by laser irradiation to the first metal plate M 1  connected to the common fixed contact G 5  (which is an example of a first contact that is one of a common contact and two switching contacts); and a step of soldering the second electrode R 9   e   2  of the first resistor R 9   a  by laser irradiation to the second metal plate M 2  connected to the second switching fixed contact  25  (which is an example of a second contact that is another one of the common contact and the two switching contacts). Compared with a case where the first resistor R 9   a  is bonded between the first metal plate M 1  and the second metal plate M 2  by a method in which the housing  1  is exposed to a temperature higher than the temperature in the laser soldering, this method can reduce the manufacturing cost of the switch  100 . This is because the housing  1  can be molded using a relatively inexpensive synthetic resin material with a low heat distortion temperature. 
     A switch and a method for manufacturing the switch according to the embodiment of the present invention are described above. However, the present invention is not limited to the specifically disclosed embodiment, and variations and modifications may be made without departing from the scope of the present invention. Features described in the above embodiment may be combined in any appropriate manner unless they are technically inconsistent with each other. 
     For example, although laser welding is used to bond the holding part H 1  to the case K 1  in the bonding step P 6  described above, an adhesive may instead be used for this purpose. 
     Also, in the above embodiment, the switch  100  includes the switching mechanism MC that switches the state of connection between the normally-open terminal  18  and the common terminal  58 . However, the switching mechanism MC may be configured to switch the state of connection among a normally-open terminal, a normally-closed terminal, and a common terminal. 
     The present invention may be applied not only to the switch  100  but also to any other device including a metal plate partially embedded in a synthetic resin component housed in a housing and an electronic component bonded by laser soldering to the metal plate.