Patent Publication Number: US-2022217879-A1

Title: Electronic device and method for manufacturing the same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of PCT/JP2020/037708 filed Oct. 5, 2020, which claims priority to Japanese Patent Application No. 2020-038332, filed Mar. 6, 2020, the entire contents of each of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an electronic device configured with a circuit substrate and an electronic component mounted on the circuit substrate, and a method for manufacturing the electronic device. 
     BACKGROUND 
     In general, an electronic device can be configured with an electronic component having a base material and a terminal electrode formed on the base material, and a circuit substrate on which a pad for mounting the electronic component is formed. 
     For example, an electronic circuit module configured by mounting various chip components on a module substrate is mounted on a main circuit substrate or a circuit substrate having a relatively large area, so that various electronic devices are configured. 
     As one specific example, a radio frequency identifier (RFID) tag to be attached to an article includes an RFIC module configured by mounting an RFIC on a module substrate on which an impedance matching circuit is formed, and a substrate on which an antenna pattern is formed, and is configured by mounting the RFIC module on the substrate. 
     WO 2016/084658 A (hereinafter “Patent Literature 1”) discloses an RFID tag including a conductor that acts as an antenna, and an RFIC module coupled to the conductor. Such an RFID tag includes an RFIC chip that stores predetermined information and processes a predetermined wireless signal, and an antenna element (e.g., a radiator) that transmits and receives a high-frequency signal, and is used by being affixed to various articles (or packaging materials therefor) to be managed. 
     When an electronic component configured with a module substrate is mounted on a circuit substrate, a terminal electrode formed on a lower surface of the electronic component is soldered to a pad formed on the circuit substrate. For the soldering, solder paste printing and reflow soldering are performed. However, the production throughput thereof is not high, which is a problem in terms of improving the mass productivity. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an electronic device configured with an electronic component having a base material and a terminal electrode formed on the base material, and a circuit substrate on which a pad for mounting the electronic component is formed, in which manufacturing efficiency is improved, and a method for manufacturing the electronic device. 
     In an exemplary aspect, an electronic device is provided that includes an electronic component having a base material and a terminal electrode formed on a first surface of the base material; and a circuit substrate in which a pad for mounting the electronic component is formed on a first surface. Moreover, a hole for light transmission is formed in the pad, and the pad and the terminal electrode are electrically and mechanically connected to each other with a cured product of optical firing paste obtained by receiving light from a second surface that is a surface opposite to the first surface of the circuit substrate. 
     In another exemplary aspect, an electronic device is provided that includes an electronic component having a base material and a terminal electrode formed on a first surface of the base material; and a circuit substrate in which a pad for mounting the electronic component is formed on a first surface. Moreover, the electronic component has a through hole extending from the first surface of the base material of the electronic component to a second surface that is a surface opposite to the first surface of the base material of the electronic component, including the terminal electrode, and the pad and the terminal electrode, which are electrically and mechanically connected to each other with a cured product of optical firing paste obtained by receiving light from the second surface of the base material of the electronic component. 
     In another exemplary aspect, an electronic device is provided that includes an electronic component having a base material and a terminal electrode formed on a first surface of the base material; and a circuit substrate in which a pad for mounting the electronic component is formed on a first surface. Moreover, the base material is configured with a light transmissive material that transmits ultraviolet light, a hole for light transmission is formed in the terminal electrode, and the pad and the terminal electrode are electrically and mechanically connected to each other with a cured product of optical firing paste obtained by receiving light from the second surface of the base material of the electronic component. 
     In yet another exemplary aspect, a method is provided for manufacturing an electronic device by mounting on a circuit substrate an electronic component having a base material and a terminal electrode formed on a first surface of the base material. In this aspect, the method includes forming a pad having a hole for light transmission on a first surface of the circuit substrate; applying optical firing paste to the pad; mounting the electronic component on the circuit substrate in a state where the terminal electrode of the electronic component faces the pad via the optical firing paste; and emitting ultraviolet light from a second surface that is a surface opposite to the first surface of the circuit substrate to cause photocuring of the optical firing paste. 
     In yet another exemplary aspect, a method is provided for manufacturing an electronic device by mounting on a circuit substrate an electronic component having a base material and a terminal electrode formed on a first surface of the base material. In this aspect, the method includes forming a through hole in the electronic component that extends from the first surface of the base material of the electronic component to a second surface that is a surface opposite to the first surface of the base material of the electronic component, including the terminal electrode; forming a pad on a first surface of the circuit substrate; applying optical firing paste to the pad; mounting the electronic component on the circuit substrate in a state where the terminal electrode of the electronic component faces the pad via the optical firing paste; and emitting ultraviolet light from the second surface of the base material of the electronic component to cause photocuring of the optical firing paste. 
     In yet another exemplary aspect, a method is provided for manufacturing an electronic device by mounting on a circuit substrate an electronic component having a base material. In this aspect, the method includes configuring the base material with a light transmissive material that transmits ultraviolet light; forming on a first surface of the base material a terminal electrode having a hole for light transmission; forming a pad on a first surface of the circuit substrate; forming optical firing paste to the pad; mounting the electronic component on the circuit substrate in a state where the terminal electrode of the electronic component faces the pad via the optical firing paste; and emitting ultraviolet light from a second surface that is a surface opposite to the first surface of the base material of the electronic component to cause photocuring of the optical firing paste. 
     According to the exemplary aspects of the present invention, the manufacturing efficiency is improved for manufacturing an electronic device configured with an electronic component having a base material and a terminal electrode formed on the base material, and a circuit substrate on which a pad for mounting the electronic component are formed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1A  is a plan view of an electronic device  201  according to a first embodiment.  FIG. 1B  is a longitudinal sectional view taken along line X-X in  FIG. 1A . 
         FIG. 2  is a plan view illustrating a configuration of pads  71 P and the like. 
         FIG. 3A  is a sectional view illustrating a state before an electronic component  101  is mounted on a circuit substrate  7 , and  FIG. 3B  is a sectional view illustrating a state after the electronic component  101  is mounted. 
         FIG. 4A  is a sectional view illustrating a state before an electronic component  101  is mounted on a circuit substrate  7 , and  FIG. 4B  is a sectional view illustrating a state after the electronic component  101  is mounted. 
         FIGS. 5A and 5B  are diagrams illustrating the manufacturing procedure of an electronic device according to the first embodiment. 
         FIG. 6A  is a plan view of an electronic device  202  according to a second embodiment.  FIG. 6B  is a longitudinal sectional view taken along line X-X in  FIG. 6A . 
         FIG. 7A  is a sectional view illustrating a state before an electronic component  102  is mounted on a circuit substrate  7 , and  FIG. 7B  is a sectional view illustrating a state after the electronic component  102  is mounted. 
         FIG. 8A  is a plan view of an electronic device  203  according to a third embodiment.  FIG. 8B  is a longitudinal sectional view taken along line X-X in  FIG. 8A . 
         FIG. 9A  is a sectional view illustrating a state before an electronic component  103  is mounted on a circuit substrate  7 , and  FIG. 9B  is a sectional view illustrating a state after the electronic component  103  is mounted. 
         FIG. 10  is a plan view of an electronic device  204  that acts as an RFID tag according to a fourth embodiment. 
         FIG. 11  is an equivalent circuit diagram of an electronic component  101  part in the electronic device  204 . 
         FIG. 12  is a diagram illustrating two resonance frequencies to be generated by providing an impedance matching circuit. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, a plurality of exemplary aspects of the present invention will be described using specific examples with reference to the drawings. In the drawings, the same portions are denoted by the same reference signs. In consideration of description of main points or ease of understanding, an embodiment is divided into a plurality of embodiments for convenience of description, though partial replacement or combination of configurations shown in different embodiments is possible. In the second and subsequent embodiments, descriptions of matters common with the first embodiment will be omitted, and only different points will be described. In particular, similar operations and effects by similar configurations will not be sequentially mentioned for each embodiment. 
     First Exemplary Embodiment 
       FIG. 1A  is a plan view of an electronic device  201  according to the first exemplary embodiment.  FIG. 1B  is a longitudinal sectional view taken along line X-X in  FIG. 1A . 
     As shown, the electronic device  201  is configured with a circuit substrate  7  and an electronic component  101  mounted on the circuit substrate  7 . The electronic component  101  includes a base material  1  and an IC  2  mounted on the base material  1 . The base material  1  has a first surface MS 1  and a second surface MS 2  opposite to the first surface. Predetermined conductor patterns are formed on the first surface MS 1  and the second surface MS 2  of the base material  1 . An interlayer connection conductor is formed inside the base material  1 . Moreover, a resist film  31  for covering a formation region of a predetermined conductor pattern is formed on the first surface MS 1  of the base material  1 , and a resist film  32  for covering a formation region of a predetermined conductor pattern is formed on the second surface MS 2  of the base material  1 . 
     In an exemplary aspect, the base material  1  is, for example, a flexible substrate having polyimide with a thickness of 20 μm as a base material, and the conductor pattern, an interlayer connection conductor, and the like are formed of copper. 
     As further shown, the IC  2  is mounted on a part of the conductor pattern formed on the second surface MS 2  of the base material  1 . A part of the conductor formed on the first surface MS 1  is terminal electrodes  13 . That is, the electronic component  101  is an electronic component having the terminal electrodes  13  for mounting the electronic component  101  on the circuit substrate  7 . 
     The circuit substrate  7  has a first surface SS 1  and a second surface SS 2  opposite to the first surface SS 1 . A predetermined conductor pattern is formed on the first surface SS 1  of the circuit substrate  7 . Pads  71 P formed on the first surface SS 1  of the circuit substrate  7  are a part of the conductor pattern in the exemplary aspect. 
     The circuit substrate  7  is, for example, a polyethylene terephthalate (PET) film having a thickness of 38 μm, and the conductor pattern is formed by patterning of an aluminum foil. 
     As illustrated in  FIG. 1B , the IC  2  is mounted on the second surface MS 2  of the base material  1  via terminal electrodes  21  of the IC  2 . The terminal electrodes  13  of the electronic component  101  and the pads  71 P of the circuit substrate  7  are electrically and mechanically joined to each other with cured products  5  of optical firing paste. Hereinafter, the structure of the joint portion and the joining method will be described. 
       FIG. 2  is a plan view illustrating a configuration of the pads  71 P and the like. As shown, a plurality of holes  71 H for light transmission are formed in the pads  71 P. Moreover, conductor patterns  71 L are drawn out from the pads  71 P. 
       FIG. 3A  is a sectional view illustrating a state before the electronic component  101  is mounted on the circuit substrate  7 , and  FIG. 3B  is a sectional view illustrating a state after the electronic component  101  is mounted. As illustrated in  FIG. 3A , optical firing paste  5 P is applied and formed on surfaces of the pads  71 P on the circuit substrate  7 . The optical firing paste  5 P is a paste obtained by kneading a conductive filler such as silver with a cuprous oxide paste for optical firing, and is cured by ultraviolet light. The optical firing paste  5 P is printed by a screen mask printing method or with a dispenser. The ultraviolet light UVL is, for example, ultraviolet light having a wavelength of 200 nm to 600 nm in an exemplary aspect. 
     Then, as illustrated in  FIG. 3B , the electronic component  101  is mounted on the circuit substrate  7  in a state where the terminal electrodes  13  of the electronic component  101  face the pads  71 P on the circuit substrate  7 , that is, in a state where the pads  71 P on the circuit substrate  7  face the terminal electrodes  13  of the electronic component  101  via the optical firing paste  5 P. Furthermore, in this state, the ultraviolet light UVL is emitted from the second surface SS 2  side of the circuit substrate  7  as illustrated in  FIG. 3B . As a result, the optical firing paste  5 P is cured.  FIG. 1B  illustrates this state. That is, the terminal electrodes  13  of the electronic component  101  and the pads  71 P of the circuit substrate  7  are electrically and mechanically joined to each other with cured products  5  of the optical firing paste. 
     Although the optical firing paste  5 P is formed on the pad  71 P side of the circuit substrate  7  in the example illustrated in  FIGS. 3A and 3B , the optical firing paste  5 P may be formed on the terminal electrode  13  side of the electronic component  101 . An example thereof will be described below.  FIG. 4A  is a sectional view illustrating a state before the electronic component  101  is mounted on the circuit substrate  7 , and  FIG. 4B  is a sectional view illustrating a state after the electronic component  101  is mounted. As illustrated in  FIG. 4A , the optical firing paste  5 P is applied and formed on surfaces of the terminal electrodes  13  of the electronic component  101 . 
     During manufacturing of the electronic component  101 , a plurality of electronic components  101  are manufactured in an aggregate substrate state in which the electronic components  101  are arranged longitudinally and laterally. That is, the optical firing paste  5 P is formed on the large number of terminal electrodes  13  in the aggregate substrate state by a screen mask printing method or with a dispenser. 
     Then, as illustrated in  FIG. 4B , the electronic component  101  is mounted on the circuit substrate  7 . In this state, the ultraviolet light UVL is emitted from the second surface SS 2  side of the circuit substrate  7 , so that the optical firing paste  5 P is cured as illustrated in  FIG. 4B . 
       FIGS. 5A and 5B  are diagrams illustrating the manufacturing procedure of an electronic device according to the first embodiment. In particular, the procedure illustrated in  FIG. 5A  corresponds to the example illustrated in  FIGS. 3A and 3B , and the procedure illustrated in  FIG. 5B  corresponds to the example illustrated in  FIGS. 4A and 4B . 
     In the procedure illustrated in  FIG. 5A , first, for the circuit substrate  7 , a conductor pattern is formed on the circuit substrate  7 , and the optical firing paste  5 P is applied to the pads  71 P. Then, the electronic component  101  is mounted, and ultraviolet light UVL is emitted from the second surface SS 2  side of the circuit substrate  7 . 
     In the procedure illustrated in  FIG. 5B , for the circuit substrate  7 , a conductor pattern is formed on the circuit substrate  7 . For the electronic component, the optical firing paste  5 P is applied to the terminal electrodes  13 . Then, the electronic component  101  is mounted on the circuit substrate  7 , and ultraviolet light UVL is emitted from the second surface SS 2  side of the circuit substrate  7 . 
     Second Exemplary Embodiment 
     In a second embodiment, an electronic device having an emission direction of ultraviolet light during manufacturing different from that in the first embodiment will be described. 
       FIG. 6A  is a plan view of an electronic device  202  according to the second exemplary embodiment.  FIG. 6B  is a longitudinal sectional view taken along line X-X in  FIG. 6A . 
     In the exemplary aspect, the electronic device  202  is configured with a circuit substrate  7  and an electronic component  102  mounted on the circuit substrate  7 . The electronic component  102  includes a base material  1  and an IC  2  mounted on the base material  1 . The base material  1  has a first surface MS 1  and a second surface MS 2  opposite to the first surface. Predetermined conductor patterns are formed on the first surface MS 1  and the second surface MS 2  of the base material  1 . As further shown, through holes  11  having a conductor film formed on the inner peripheral surface thereof are formed inside the base material  1 . Moreover, a resist film  31  for covering a formation region of a predetermined conductor pattern is formed on the first surface MS 1  of the base material  1 , and a resist film  32  for covering a formation region of a predetermined conductor pattern is formed on the second surface MS 2  of the base material  1 . 
     In this exemplary aspect, the base material  1  is, for example, a flexible substrate having polyimide with a thickness of 20 μm as a base material, and the conductor pattern, an interlayer connection conductor, and the like are formed of copper. 
     The IC  2  is mounted on a part of the conductor pattern formed on the second surface MS 2  of the base material  1 . Moreover, a part of the conductor formed on the first surface MS 1  is terminal electrodes  13 . 
     The circuit substrate  7  has a first surface SS 1  with a predetermined conductor pattern formed on the first surface SS 1  of the circuit substrate  7 . Pads  71 P formed on the first surface SS 1  of the circuit substrate  7  are a part of the conductor pattern. The holes  71 H as illustrated in  FIG. 2  in the first embodiment are not formed in the pads  71 P in this exemplary aspect. 
     The circuit substrate  7  is, for example, a polyethylene terephthalate (PET) film having a thickness of 38 μm, and the conductor pattern is formed by patterning of an aluminum foil. 
     The terminal electrodes  13  of the electronic component  102  and the pads  71 P of the circuit substrate  7  are electrically and mechanically joined to each other with cured products  5  of optical firing paste as illustrated in  FIG. 6B . Hereinafter, the structure of the joint portion and the joining method will be described. 
       FIG. 7A  is a sectional view illustrating a state before the electronic component  102  is mounted on the circuit substrate  7 , and  FIG. 7B  is a sectional view illustrating a state after the electronic component  102  is mounted. In the terminal electrodes  13  of the electronic component  102 , holes  13 H for light transmission are formed at positions overlapped with the through holes  11 . As illustrated in  FIG. 7A , optical firing paste  5 P is applied and formed on surfaces of the pads  71 P on the circuit substrate  7 . The optical firing paste  5 P is a paste obtained by kneading a conductive filler such as silver with a cuprous oxide paste for optical firing, and is cured by ultraviolet light. 
     Then, as illustrated in  FIG. 7B , the electronic component  102  is mounted on the circuit substrate  7  in a state where the terminal electrodes  13  of the electronic component  102  face the pads  71 P on the circuit substrate  7 , that is, in a state where the pads  71 P on the circuit substrate  7  face the terminal electrodes  13  of the electronic component  102  via the optical firing paste  5 P. Furthermore, in this state, ultraviolet light UVL is emitted from the second surface MS 2  side of the electronic component  102  as illustrated in  FIG. 7B . The ultraviolet light UVL is emitted to the optical firing paste  5 P through the through holes  11  and the holes  13 H of the terminal electrodes  13 . As a result, the optical firing paste  5 P is cured.  FIG. 6B  illustrates this state. That is, the terminal electrodes  13  of the electronic component  102  and the pads  71 P of the circuit substrate  7  are electrically and mechanically joined to each other with the cured products  5  of the optical firing paste. As described above, the through holes  11  not only make interlayer connection between the conductor pattern formed on the first surface MS 1  of the base material  1  and the conductor pattern formed on the second surface MS 2 , but also act as light transmission paths of the ultraviolet light UVL. 
     Although the optical firing paste  5 P is formed on the pad  71 P side of the circuit substrate  7  in the example illustrated in  FIGS. 7A and 7B , the optical firing paste  5 P can be formed on the terminal electrode  13  side of the electronic component  102  in an alternative aspect. 
     Third Exemplary Embodiment 
     In a third embodiment, an electronic device including an electronic component having a base material that transmits ultraviolet light will be described. 
       FIG. 8A  is a plan view of an electronic device  203  according to the third embodiment.  FIG. 8B  is a longitudinal sectional view taken along line X-X in  FIG. 8A . 
     The electronic device  203  is configured with a circuit substrate  7  and an electronic component  103  mounted on the circuit substrate  7 . The electronic component  103  includes a base material  1  and an IC  2  mounted on the base material  1 . The base material  1  has a first surface MS 1  and a second surface MS 2  opposite to the first surface. Moreover, predetermined conductor patterns are formed on the first surface MS 1  and the second surface MS 2  of the base material  1 . A resist film  31  for covering a formation region of a predetermined conductor pattern is formed on the first surface MS 1  of the base material  1 , and a resist film  32  for covering a formation region of a predetermined conductor pattern is formed on the second surface MS 2  of the base material  1 . 
     In the exemplary aspect, the base material  1  is made of a light transmissive material. More particularly, the base material  1  is, for example, a transparent polyimide film. Windows  32 W for light transmission are formed in the pattern of the resist film  32 . 
     The IC  2  is mounted on a part of the conductor pattern formed on the second surface MS 2  of the base material  1 . A part of the conductor formed on the first surface MS 1  is terminal electrodes  13 . 
     The circuit substrate  7  has a first surface SS 1 . A predetermined conductor pattern is formed on the first surface SS 1  of the circuit substrate  7 . Pads  71 P formed on the first surface SS 1  of the circuit substrate  7  are a part of the conductor pattern. 
     The terminal electrodes  13  of the electronic component  103  and the pads  71 P of the circuit substrate  7  are electrically and mechanically joined to each other with cured products  5  of optical firing paste as illustrated in  FIG. 8B . Hereinafter, the structure of the joint portion and the joining method will be described. 
       FIG. 9A  is a sectional view illustrating a state before the electronic component  103  is mounted on the circuit substrate  7 , and  FIG. 9B  is a sectional view illustrating a state after the electronic component  103  is mounted. As further shown, a plurality of holes  13 H for light transmission are formed in the terminal electrodes  13  of the electronic component  103 . As illustrated in  FIG. 9A , optical firing paste  5 P is applied and formed on surfaces of the pads  71 P on the circuit substrate  7 . The optical firing paste  5 P is a paste obtained by kneading a conductive filler, such as silver, with a cuprous oxide paste for optical firing, and is cured by ultraviolet light. 
     Then, as illustrated in  FIG. 9B , the electronic component  103  is mounted on the circuit substrate  7  in a state where the terminal electrodes  13  of the electronic component  103  face the pads  71 P on the circuit substrate  7 , that is, in a state where the pads  71 P on the circuit substrate  7  face the terminal electrodes  13  of the electronic component  103  via the optical firing paste  5 P. Furthermore, in this state, ultraviolet light UVL is emitted from the second surface MS 2  side of the electronic component  103  as illustrated in  FIG. 9B . The ultraviolet light UVL is emitted to the optical firing paste  5 P through the windows  32 W for light transmission and the holes  13 H of the terminal electrodes  13 . As a result, the optical firing paste  5 P is cured.  FIG. 8B  illustrates this state. That is, the terminal electrodes  13  of the electronic component  103  and the pads  71 P of the circuit substrate  7  are electrically and mechanically joined to each other with the cured products  5  of the optical firing paste. 
     Although the optical firing paste  5 P is formed on the pad  71 P side of the circuit substrate  7  in the example illustrated in  FIGS. 9A and 9B , the optical firing paste  5 P may be formed on the terminal electrode  13  side of the electronic component  103  in an alternative aspect. 
     Fourth Exemplary Embodiment 
     In a fourth exemplary embodiment, an RFIC module for an RFID tag, and an RFID tag including the RFIC module will be exemplified. 
       FIG. 10  is a plan view of an electronic device  204  that acts as an RFID tag according to the fourth embodiment. As shown, antenna conductor patterns  71  are formed on a circuit substrate  7 , and the antenna conductor patterns  71  constitute antennas. The circuit substrate  7  is, for example, a polyethylene terephthalate (PET) film, and the antenna conductor patterns  71  are, for example, patterns of a metal foil such as a copper foil. 
     Each antenna conductor pattern  71  is configured with conductor patterns  71 C and  71 L, and a pad  71 P. The antenna conductor pattern  71  constitutes a dipole antenna. An electronic component  101  as an RFIC module is mounted on the pad  71 P as illustrated in  FIG. 1B  in the first embodiment. The conductor pattern  71 L has a meander line shape and acts as a region having a high inductance component. Moreover, the conductor pattern  71 C has a planar shape and acts as a region having a high capacitance component. 
       FIG. 11  is an equivalent circuit diagram of an electronic component  101  part in the electronic device  204 . An IC  2  is an RFIC for an RFID, and has an equivalent capacitance Cp between two terminals. Inductors L 1 , L 2 , L 3 , and L 4  form an impedance matching circuit, and two resonances are generated in a state where the impedance matching circuit and the antenna conductor patterns  71  are connected to the IC  2 . A first resonance is a resonance generated in a current path configured with the antenna conductor patterns  71 , the inductor L 3 , and the inductor L 4 , and a second resonance is a resonance generated in a current path (e.g., a current loop) configured with the inductors L 1  to L 4 . The two resonances are coupled by the inductors L 3  and L 4  shared by the current paths, and two currents i 1  and i 2  respectively corresponding to the two resonances flow as illustrated in  FIG. 11 . 
     Both the frequency of the first resonance and the frequency of the second resonance are affected by the inductors L 3  and L 4 . A difference of several tens MHz (specifically, approximately 5 to 50 MHz) is generated between the frequency of the first resonance and the frequency of the second resonance.  FIG. 12  is a diagram illustrating two resonance frequencies to be generated by providing the impedance matching circuit. The resonance frequency characteristics thereof are expressed by curve A and curve B in  FIG. 12 . By coupling two resonances having such resonance frequencies, a broadband resonance frequency characteristic as indicated by curve C in  FIG. 12  is obtained. 
     Finally, it is noted generally that the above description of the exemplary embodiments is illustrative in all respects and is not restrictive. Modifications and changes can be made as appropriate by those skilled in the art. 
     For example, although the above embodiments have illustrated examples in which ultraviolet light is emitted from the second surface MS 2  of the base material  1  of the electronic component or from the second surface SS 2  of the circuit substrate  7 , ultraviolet light may be emitted from both the second surface MS 2  of the base material  1  of the electronic component and the second surface SS 2  of the circuit substrate  7  by combining the first embodiment and the second embodiment or by combining the first embodiment and the third embodiment as would be appreciated to one skilled in the art. 
     Moreover, although an electronic device including an electronic component having a light non-transmissive resist film has been exemplified in the second embodiment and the third embodiment, a light transmissive resist film may be used. In this case, also in the second embodiment and the third embodiment, as illustrated in  FIGS. 1A and 1B , the resist film  32  may be formed on the entire surface of the second surface MS 2  of the base material  1  except for the region where the IC  2  is mounted. 
     REFERENCE SIGNS LIST 
     
         
         
           
             L 1 , L 2 , L 3 , L 4  inductor 
             MS 1  first surface of base material of electronic component 
             MS 2  second surface of base material of electronic component 
             SS 1  first surface of substrate 
             SS 2  second surface of substrate 
             UVL ultraviolet light 
               1  base material 
               2  IC 
               5  cured product of optical firing paste 
               5 P optical firing paste 
               7  circuit substrate 
               11  through hole 
               13  terminal electrode 
               13 H hole for light transmission 
               21  terminal electrode 
               31 ,  32  resist film 
               32 W window for light transmission 
               71  antenna conductor pattern 
               71 C,  71 L conductor pattern 
               71 H hole 
               71 P pad 
               101 ,  102 ,  103  electronic component 
               201 ,  202 ,  203 ,  204  electronic device