Patent Publication Number: US-2015084087-A1

Title: Light Emitting Module and Lighting Device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priorities from Japanese Patent Application No. 2013-198901 filed on Sep. 25, 2013; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate to a light emitting module and a lighting device. 
     BACKGROUND 
     LED (Light Emitting Diode) lighting is introduced into facilities and general households at an accelerating pace as an environmentally friendly light source from the viewpoints of long life, power saving, and the like. Currently, a chip on board (COB) type in which plurality of LED chips are mounted on a board to increase brightness is a mainstream. As the board, in terms of productivity and the like, an organic board of resin or the like formed by applying silver plating to a reflecting layer and a mounting pad is often used. 
     Plating requires extremely advanced know-how and is high in costs. Residues due to stain or the like of plating liquid sometimes adhere to the surface of a plated metal film. When the residues adhere to the surface of the reflecting layer, the reflectance of light of the reflecting layer deteriorates. Therefore, when a lighting device is configured using such a board, light emitting efficiency of lighting as a whole is sometimes deteriorated. 
     In recent years, a technique for forming a metal film through printing is also developed. However, the metal film formed by the printing has low density. Therefore, when a component is joined on the metal film by solder, the solder erodes the metal film and the component tends to peel together with the metal film. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing an example of a lighting device according to a first embodiment; 
         FIG. 2  is a sectional view showing the example of the lighting device according to the first embodiment; 
         FIG. 3  is a conceptual diagram showing an example of an electrical connection relation of the lighting device according to the first embodiment; 
         FIG. 4  is a diagram showing an example of the configuration of a light emitting module according to the first embodiment; 
         FIG. 5  is a diagram showing an example of mounting pads provided on a board according to the first embodiment; 
         FIG. 6  is a top view showing an example of a light emitting unit according to the first embodiment; 
         FIG. 7  is an A-A sectional view of the light emitting unit shown in  FIG. 6 ; 
         FIG. 8  is a conceptual diagram for explaining an electric component mounted on the mounting pads; 
         FIG. 9  is a top view showing an example of a light emitting unit according to a second embodiment; and 
         FIG. 10  is a B-B sectional view of the light emitting unit shown in  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION 
     It is an object of the present invention to prevent deterioration in light emitting efficiency and prevent peeling of a component. 
     According to one embodiment, there is provided a light emitting module including: a board; an LED, which is an example of a semiconductor light emitting element; an electronic component; a first pad provided on the board, the surface of the first pad being covered with a metal film and the LED being mounted on the first pad; and a second pad provided on the board, the surface of the second pad being covered with a metal film and the electric component being mounted on the second pad. The LED is wire-bonded on the first pad covered with the metal film. The electric component is joined by solder on the second pad covered with the metal film. The metal film covering the first pad has a film structure lower in density than the metal film covering the second pad. With the light emitting module having such a configuration, it can be expected to prevent deterioration in light emitting efficiency and prevent peeling of a component. 
     In the light emitting module according to the embodiment, the metal film covering the first pad may be formed on the surface of the first pad by printing. The metal film covering the second pad may be formed on the surface of the second pad by plating. Consequently, it can be expected to prevent deterioration in light emitting efficiency and prevent peeling of a component at low costs. 
     In the light emitting module according to the embodiment, the metal film covering the first pad may be formed of gold or silver on the surface of the first pad. The metal film covering the second pad may be formed of gold, silver, or rhodium on the surface of the second pad. 
     In the light emitting module according to the embodiment, the board may be formed of ceramic. Consequently, it can be expected to improve light emitting efficiency of the light emitting module at low costs. 
     According to another embodiment, there is provided a lighting device including: the light emitting module; and a lighting-on device configured to supply electric power to the light emitting module. 
     A light emitting module and a lighting device according to embodiments are explained below with reference to the drawings. In the embodiments, components having the same functions are denoted by the same reference numerals and signs and redundant explanation of the components is omitted. The light emitting module and the lighting device explained in the embodiments are only an example and do not limit the present invention. The embodiments may be combined as appropriate to the extent that the embodiments do not contradict each other. 
     First Embodiment 
     A straight tube type lamp and a lighting device including the straight tube type lamp, for example, a lighting apparatus according to a first embodiment are explained below with reference to  FIGS. 1 to 4 . 
     Configuration of a Lighting Device  1   
       FIG. 1  is a perspective view illustrating an example of the lighting device according to the first embodiment.  FIG. 2  is a cross-sectional view of the lighting apparatus illustrated in  FIG. 1 . In  FIGS. 1 and 2 , a numeral  1  illustrates a direct-mounted type lighting device. 
     The lighting device  1  includes a device body (an apparatus body)  2 , a lighting-on device  3 , a pair of first socket  4   a  and second socket  4   b,  a reflection member  5 , a straight tube type lamp  11  that is an example of a light source device, and the like. 
     The body  2  illustrated in  FIG. 2  is, for example, made of a metal plate having an elongated shape. The body  2  extends in a front and back direction of a paper on which  FIG. 2  is drawn. The body  2  is, for example, fixed to a ceiling in a room by using a plurality of screws (not illustrated). 
     The lighting-on device  3  is fixed to a middle section of the body  2  in a longitudinal direction. The lighting-on device  3  generates a DC output by receiving a commercial AC power supply and supplies the DC output to the straight tube type lamp  11  described below. 
     Moreover, the body  2  has a power supply terminal stand (not illustrated), a plurality of member support fittings, a pair of socket support members, and the like. A power supply line of the commercial AC power supply drawn from a ceiling is connected to the power supply terminal stand. Further, the power supply terminal stand is electrically connected to the lighting-on device  3  through a wiring (not illustrated) in the apparatus. 
     The socket  4   a  and the socket  4   b  are disposed in both end sections of the body  2  in the longitudinal direction by being respectively connected to the socket support members. The socket  4   a  and the socket  4   b  are mounted by rotation. For example, the socket  4   a  and the socket  4   b  are sockets suitable for G13 type mouthpieces  13   a  and  13   b,  respectively, which are included in the straight tube type lamp  11  described below. 
       FIG. 3  is a conceptual view illustrating an example of an electrical connection relationship of the lighting device according to the first embodiment. As illustrated in  FIG. 3 , the socket  4   a  and the socket  4   b  have a pair of terminal fittings  8  and terminal fittings  9  to which lamp pins  16   a  and  16   b  (described below) are respectively connected. In order to supply the power supply to the straight tube type lamp  11  described below, the terminal fittings  8  of the first socket  4   a  are connected to the lighting-on device  3  through the wiring in the apparatus. 
     As illustrated in  FIG. 1  or  2 , for example, the reflection member  5  has a bottom plate section  5   a,  a side plate section  5   b  and an end plate  5   c,  which are made of metal and has a trough shape of which an upper surface is opened. The bottom plate section  5   a  is flat. The side plate section  5   b  is bent obliquely upward from the both ends of the bottom plate section  5   a  in a width direction. The end plate  5   c  closes an end surface opening formed by ends of the bottom plate section  5   a  and the side plate section  5   b  in the longitudinal direction. 
     A metal plate forming the bottom plate section  5   a  and the side plate section  5   b  is made of a color steel plate of which a surface has a white-based color. Thus, the surfaces of the bottom plate section  5   a  and the side plate section  5   b  are reflection surfaces. Socket holes (not illustrated) are formed on respective ends of the bottom plate section  5   a  in the longitudinal direction. 
     The reflection member  5  covers the body  2  and each component that is mounted on the body  2 . The state is held by detachable decorative screws  6  (see  FIG. 1 ). The decorative screw  6  is screwed upwardly into the member support fitting through the bottom plate section  5   a.  The decorative screw  6  may be operated by hand without using any tool. The socket  4   a  and the socket  4   b  protrude downward from the bottom plate section  5   a  through the socket holes. 
     In  FIG. 1 , the lighting device  1  supports one straight tube type lamp  11  described below, but, for example, may include two pairs of sockets to support two straight tube type lamps  11  as another form. 
     The straight tube type lamp  11  that is detachably supported by the socket  4   a  and the socket  4   b  is described below with reference to  FIGS. 2 and 3 . The straight tube type lamp  11  has dimensions and an outer diameter similar to those of the existing fluorescent lamp. The straight tube type lamp  11  includes a pipe  12 , a first mouthpiece  13   a  and a second mouthpiece  13   b  which are mounted in both ends of the pipe  12 , a beam  14  and a light emitting module  15 . 
     The pipe  12  is formed of a resin material having translucency, for example, in an elongated shape. As the resin material forming the pipe  12 , a polycarbonate resin in which a light diffusion member is mixed can be preferably used. Diffuse transmittance of the pipe  12  is preferably 90% to 95%. As illustrated in  FIG. 2 , the pipe  12  has a pair of convex sections  12   a  on an inner surface of a portion that is an upper section when being used. 
     The first mouthpiece  13   a  is mounted on one end section of the pipe  12  in the longitudinal direction and the second mouthpiece  13   b  is mounted on the other end section of the pipe  12  in the longitudinal direction. The first mouthpiece  13   a  and second mouthpiece  13   b  are detachably connected to the socket  4   a  and the socket  4   b,  respectively. The straight tube type lamp  11  that is supported on the socket  4   a  and the socket  4   b  is disposed directly below the bottom plate section  5   a  of the reflection member  5  by the connection. A part of light that is emitted from the straight tube type lamp  11  to the outside is reflected from the side plate section  5   b  of the reflection member  5 . 
     As illustrated in  FIG. 3 , the first mouthpiece  13   a  has two lamp pins  16   a  protruding to the outside thereof. The lamp pins  16   a  are electrically insulated from each other. In addition, leading ends of the two lamp pins  16   a  have L-shapes which are bent substantially at a right angle so as to separate from each other. 
     As illustrated in  FIG. 3 , the second mouthpiece  13   b  has one lamp pin  16   b  protruding to the outside thereof. The lamp pin  16   b  has a cylindrical shaft section and a leading end section which is provided in a leading end section of the cylindrical shaft section, and of which a shape of a front surface (not illustrated) has an elliptical shape or an oval shape, and a side surface of the lamp pin  16   b  has a T-shape. 
     The lamp pins  16   a  of the first mouthpiece  13   a  are connected to the terminal fittings  8  of the socket  4   a  and the lamp pin  16   b  of the second mouthpiece  13   b  is connected to the terminal fittings  9  of the socket  4   b  so that the straight tube type lamp  11  is mechanically supported on the socket  4   a  and the socket  4   b.  In a state of being supported, power is supplied to the straight tube type lamp  11  by the terminal fittings  8  inside the socket  4   a  and the lamp pins  16   a  of the first mouthpiece  13   a  connected thereto. 
     As illustrated in  FIG. 2 , the beam  14  is accommodated in the pipe  12 . The beam  14  is a bar member having excellent mechanical strength and, for example, is formed of an aluminum alloy or the like for weight reduction. Both ends of the beam  14  in the longitudinal direction are connected to the first mouthpiece  13   a  and the second mouthpiece  13   b  by being electrically insulated. For example, the beam  14  has a plurality of substrate support sections  14   a  (one is illustrated in  FIG. 2 ) having rib shapes. 
       FIG. 4  is a diagram showing an example of the configuration of the light emitting module according to the first embodiment. As shown in  FIG. 4 , in the light emitting module  15 , on a board  21  formed in an elongated substantially rectangular tabular shape, a plurality of light emitting units  54  are arranged side by side in a longitudinal direction of the board  21 . 
     Various electric components  57  such as resistors and connectors are arranged on the board  21 . Not to prevent lights emitted by the light emitting units  54 , the electric components  57  are arranged close to a corner on the board  21  or on the rear surface of the surface of the board  21  on which the light emitting units  54  are provided. 
     In this embodiment, the board  21  is, for example, a glass epoxy board formed using resin. The front surface of the board  21  is covered with a resist layer containing synthetic resin having high electric insulation properties except a surface on which mounting pads mounted with the light emitting units  54  and the electric components  57  are provided. The resist layer is, for example, white and also functions as a reflecting layer having high light transmittance. 
     The length of the board  21  is substantially equal to the total length of the beam  14 . The board  21  is fixed by not-shown screws screwed into the beam  14 . In this embodiment, the light emitting module  15  includes one board  21 . However, as another form, the light emitting module  15  may include a plurality of the boards  21 . 
     The light emitting module  15  is housed in the pipe  12  together with the beam  14 . In this supported state, both ends in the width direction of the light emitting module  15  are placed on the convex sections  12   a  of the pipe  12 . Consequently, the light emitting module  15  is disposed substantially horizontally further on the upper side than a maximum width section in the pipe  12 . 
       FIG. 5  is a diagram showing an example of mounting pads provided on the board according to the first embodiment. On the board  21 , a plurality of mounting pads  28  on which the light emitting units  54  are mounted and a plurality of mounting pads  58  on which the electric components  57  are mounted are provided. Each of the mounting pads  28  includes a wiring pad  26  and a wiring pad  27 . 
     In this embodiment, the surfaces of the wiring pad  26  and the wiring pad  27  are covered with a metal film having a low density film structure. In this embodiment, the metal film covering the surfaces of the wiring pad  26  and the wiring pad  27  is formed of a material having high reflectance, for example, gold. As another form, the metal film may be formed of silver or the like. In this embodiment, the metal film is formed on the surfaces of the wiring pad  26  and the wiring pad  27  by printing. 
     In this embodiment, the surface of each of the mounting pads  58  is covered with a metal film having a film structure higher in density than the metal film covering the wiring pad  26  and the wiring pad  27 . In this embodiment, the metal film covering the surface of the mounting pad  58  is formed of, for example, silver. As another form, the metal film may be formed of gold, rhodium, or the like. In this embodiment, the metal film is formed on the surface of the mounting pad  58  by plating. 
     Configuration of the Light Emitting Unit  54   
       FIG. 6  is a top view showing an example of the light emitting unit according to the first embodiment.  FIG. 7  is an A-A sectional view of the light emitting unit shown in  FIG. 6 . 
     The light emitting unit  54  includes an LED  45  and a sealing member  53 . The LED  45  includes a base material formed of sapphire or the like and a semiconductor layer (a light emitting layer) including gallium nitride (GaN) formed on the base material. The base material is die-bonded on the wiring pad  27  by, for example, a white or silver adhesive  30  having high reflectance. 
     On the light emitting layer, an anode electrode and a cathode electrode are formed. The anode electrode of the light emitting layer is wire-bonded to the wiring pad  26  by a wire  51  of gold or the like. The cathode electrode of the light emitting layer is wire-bonded to the wiring pad  27  by a metal wire  52  of gold or the like. The wiring pad  26  and the wiring pad  27  are connected to the wiring layer provided on the board  21 . 
     The sealing member  53  is thermosetting transparent resin having high diffusibility such as epoxy resin, urea resin, or silicon resin added with a phosphor. The phosphor is excited by light emitted by the LED  45  to emit light having a color different from a color of the light emitted by the LED  45 . 
     In this embodiment, as the phosphor, a yellow phosphor is used that is excited by blue light emitted by the LED  45  to emit yellow-based light, which is in a complementary color relation with the blue light. Consequently, the light emitting unit  54  can emit white light as output light. 
       FIG. 8  is a conceptual diagram for explaining an electric component mounted on the mounting pads. In the electric component  57  such as a resistor or a connector, for example, as shown in  FIG. 8 , terminals  59  of the electric component  57  are joined to the mounting pad  58  by solder  60 . 
     If the metal film on the surfaces of the mounting pads is formed by plating, residues sometimes remain on the surface of the metal film in a process in which plating liquid dries. When the residues are present on the surface of the metal film, the reflectance of the metal film deteriorates. Therefore, if the metal film is present near the LED  45 , light emitted from the LED  45  is absorbed by the metal film. The light emitting efficiency of the entire light emitting module  15  is sometimes deteriorated 
     If the residues are present on the surface of the metal film, when a metal wire is wire-bonded on the metal film, heat of a capillary is not sufficiently transmitted to the metal film and the mounting pads under the residues. The distal end of the metal wire and the mounting pads are not sometimes joined at sufficient strength. Since an advanced technique and equipment are necessary for the plating, costs are relatively high. 
     On the other hand, in the printing, since it is possible to form a metal film with less stain, it is possible to form a metal film having high reflectance. In the metal film formed by the printing, less dust such as residues remains on the surface. Therefore, when the metal wire is bonded on the metal film, the distal end of the metal wire and the mounting pads can be joined at sufficient strength. The printing can be realized at low costs compared with the plating. 
     However, if the metal film covering the surfaces of the mounting pads is formed by the printing, when a component is joined on the metal film by solder, the solder erodes the metal film. If the solder erodes the metal film, the component tends to peel together with the metal film. 
     This is because the metal film formed by the printing has a film structure lower in density than the metal film formed by the plating. A difference in the density of the film structure can be determined by, for example, photographing the cross section of the metal film with a scanning electron microscope (SEM) and comparing the number and the size of air gaps in a photographed image. In an SEM image of the cross section of the metal film formed by the printing, the number of air gaps is apparently large and the size of the air gaps is large compared with an SEM image of the cross section of the metal film formed by the plating. 
     Therefore, in this embodiment, the surfaces of the mounting pads, on which a component joined by solder is mounted, are covered with a metal film having a high density film structure. The surfaces of the mounting pads required to have high reflectance and the mounting pads bonded by a metal wire are covered with a metal film having a low density film structure. The metal film having the high density film structure is formed by, for example, plating and the metal film having the low density film structure is formed by, for example, printing. 
     Consequently, on the mounting pads  58  mounted using solder, the metal film is formed by the plating as in the past. Therefore, it can be expected to prevent peeling of the electric component  57 . On the mounting pad  28  around the LED  45 , the metal film is formed by the printing. Therefore, it is possible to improve the light emitting efficiency of the light emitting module  15  and it can be expected to reduce manufacturing costs for the light emitting module  15 . 
     The first embodiment is explained above. 
     As it is evident from the above explanation, with the light emitting module  15  in this embodiment, it is possible to improve the light emitting efficiency of the light emitting module  15  and it can be expected to prevent peeling of a component. 
     Second Embodiment 
     A second embodiment is explained with reference to the drawings. The configurations of the lighting device  1 , the straight tube type lamp  11 , and the light emitting module  15  in this embodiment are the same as the configurations of the lighting device  1 , the straight tube type lamp  11 , and the light emitting module  15  in the first embodiment. Therefore, detailed explanation of the configurations is omitted. 
     Configuration of the Light Emitting Unit  54   
       FIG. 9  is a top view showing an example of a light emitting unit according to the second embodiment.  FIG. 10  is a B-B sectional view of the light emitting unit shown in  FIG. 9 . Except points explained below, in  FIG. 9  or  10 , components denoted by reference numerals same as the reference numerals in  FIG. 6  or  7  have functions same as or similar to the functions of the components shown in  FIG. 6  or  7 . Therefore, explanation of the components is omitted. 
     In this embodiment, the board  21  is formed of a material having insulation properties and high reflectance, for example, ceramic. In this embodiment, each of the mounting pads  28  includes the wiring pad  26  and a wiring pad  29 . The surface of the wiring pad  29  is covered with a metal film having a low density film structure. 
     In this embodiment, the metal film covering the surface of the wiring pad  29  is formed of a material having high reflectance, for example, gold. As another form, the metal film may be formed of silver or the like. In this embodiment, the metal film is formed on the surface of the wiring pad  29  by printing. 
     In this embodiment, a base material of the LED  45  is die-bonded on the board  21  by, for example, the white or silver adhesive  30  having high reflectance. An anode electrode of a light emitting layer is wire-bonded to the wiring pad  26  by the wire  51  of gold or the like. A cathode electrode of the light emitting layer is wire-bonded to the wiring pad  29  by the metal wire  52  of gold or the like. The wiring pad  26  and the wiring pad  29  are connected to a wiring layer provided on the board  21 . 
     As the board  21  in this embodiment, ceramic having relatively high reflectance is used. Therefore, it is unnecessary to form a metal film having high reflectance on the surface of the board  21  on which the LED  45  is bonded. Therefore, it is possible to reduce a region where a metal film having high reflectance of gold or the like is formed. It can be expected to suppress costs of the light emitting module  15 . 
     In this embodiment, as in the first embodiment, the metal film of gold or the like is formed on the surfaces of the wiring pad  26  and the wiring pad  29  by printing. A metal film of silver or the like is formed by plating on the surface of a mounting pad on which an electric component is joined by solder. 
     The second embodiment is explained above. 
     As it is evident from the above explanation, in the light emitting module  15  in this embodiment, as in the first embodiment, it is possible to improve the light emitting efficiency of the light emitting module  15  and it can be expected to prevent peeling of a component. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.