Patent Publication Number: US-2021167046-A1

Title: Surface-emitting light source and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Japanese Patent Application No. 2019-219175, filed on Dec. 3, 2019, and Japanese Patent Application No. 2020-116723, filed on Jul. 6, 2020, the contents of which are hereby incorporated by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to a surface-emitting light source and a method of manufacturing the same. 
     2. Description of Related Art 
     In a known method, electroless or electrolytic copper plating is performed in via holes in a base member to dispose via-conductors (for example, see Japanese Unexamined Patent Application Publication No. 2006-237232). When forming via-conductors inside the via-holes by plating, the plating is performed in a wet process, so that large-scale devices may be used and manufacturing steps may be complicated. Meanwhile, a dry-process technique is also known in which a wiring board and a light-emitting module are connected by pressing while heating. 
     SUMMARY 
     An object of certain embodiments according to the present disclosure is to provide a surface-emitting light source in which reliability of connection using a dry process can be increased and a method of manufacturing the same. 
     A surface-emitting light source according to one embodiment of the present disclosure includes a plurality of light-emitting modules; a wiring substrate including a base member having a surface at a light-emitting modules side and a rear surface opposite to the surface at the light-emitting modules side, a wiring layer disposed on the rear surface of the base member and including wiring pads which are portions of the wiring layer, electrically-conductive members each supplied across corresponding two or more of a plurality of vias, the plurality of vias formed in each of the wiring pads, and a covering layer covering the wiring layer and defining openings in each of which a portion of a corresponding one of the wiring pads is exposed; and an adhesive layer between the plurality of light-emitting modules and the wiring substrate. Each of the light-emitting modules has an array of a plurality of light emitting devices. The covering layer defines the openings at locations corresponding to the wiring pads with an area dimension smaller than respective area dimensions of the wiring pads. 
     A surface-emitting light source according to another embodiment of the present disclosure includes: a plurality of light-emitting modules; a wiring substrate including a base member having a surface at a light-emitting modules side and a rear surface opposite to the surface at the light-emitting modules side, a wiring layer disposed on the rear surface of the base member and including wiring pads as portions of the wiring layer, electrically-conductive members each supplied into a respective one of vias each formed in a corresponding one of the wiring pads, and a covering layer covering the wiring layer and defining openings in each of which a portion of a corresponding one of the wiring pads is exposed; and an adhesive layer between the wiring substrate and the plurality of light-emitting modules. Each of the light-emitting modules has an array of a plurality of light emitting devices. The covering layer defines the openings at locations corresponding to the wiring pads with an area dimension smaller than respective area dimensions of the wiring pads. 
     A method of manufacturing a surface-emitting light source according to still another embodiment of the present disclosure includes: providing a wiring substrate, the wiring substrate including a base member having a front surface and a rear surface opposite to the front surface, a wiring layer disposed on the rear surface of the base member and including wiring pads which are portions of the wiring layer, and a covering layer covering the wiring layer to define openings in each of which a portion of a corresponding one of the wiring pads is exposed, such that the covering layer defines the openings at locations corresponding to the wiring pads with an area dimension smaller than respective area dimensions of the wiring pads in a plan view; disposing an adhesive layer on a front surface side of the base member and forming through-holes in the wiring pad through the opening to extend through the wiring substrate and the adhesive layer; temporarily connecting a plurality of light emitting modules each having an array of a plurality of light emitting devices to the front surface side of the base member, covering openings of the plurality of through holes formed in the front surface side of the base member by the plurality of light emitting devices, creating a plurality of vias from the plurality of through holes; supplying an electrically-conductive material into the vias; and pressing and heating to obtain an electrically-conductive member and to bond the wiring substrate and the light-emitting modules through the adhesive layer. 
     Certain embodiments according to the present disclosure allows for providing a wiring substrate having higher reliability of connection. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic enlarged view illustrating a portion of a surface-emitting light source according to one embodiment viewed from a rear surface side of a wiring substrate. 
         FIG. 2  is a schematic plan view of light-emitting modules of the surface-emitting light source according to one embodiment. 
         FIG. 3A  is a schematic cross-sectional view taken along a line IIIA-IIIA of  FIG. 1 . 
         FIG. 3B  is a schematic cross-sectional view taken along a line IIIB-IIIB of  FIG. 1 . 
         FIG. 3C  is a schematic cross-sectional view taken along a line IIIC-IIIC of  FIG. 1 . 
         FIG. 4  is a schematic enlarged view illustrating a relationship between an opening formed in a first covering layer and a wiring pad of the surface-emitting light source according to one embodiment. 
         FIG. 5  is a schematic cross-sectional view taken along a line V-V of  FIG. 4 . 
         FIG. 6  is a schematic cross-sectional view taken along a line VI-VI of  FIG. 5 . 
         FIG. 7  is a flowchart illustrating a method of manufacturing the surface-emitting light source according to one embodiment. 
         FIG. 8A  is a schematic view illustrating a cross-section of a wiring substrate provided in a step of providing a wiring substrate in the method of manufacturing the surface-emitting light source according to one embodiment. 
         FIG. 8B  is a schematic view illustrating a state in which the wiring substrate is bonded to an adhesive layer and through-holes are formed in a step of forming through-holes in the method of manufacturing the surface-emitting light source according to one embodiment. 
         FIG. 8C  is a schematic view illustrating a state in which vias are created in a step of creating vias in the method of manufacturing the surface-emitting light source according to one embodiment. 
         FIG. 8D  is a schematic view illustrating a state in which an electrically-conductive material is supplied into the vias in a step of supplying in the method of manufacturing the surface-emitting light source according to one embodiment. 
         FIG. 8E  is a schematic cross-sectional view illustrating a step of pressing in the method of manufacturing the surface-emitting light source according to one embodiment. 
         FIG. 8F  is a schematic view illustrating a state in which a protective member is formed in a step of forming a protective member in the method of manufacturing the surface-emitting light source according to one embodiment. 
         FIG. 9A  is a schematic enlarged plan view of an opening of a first covering member in a first variation of the surface-emitting light source according to one embodiment. 
         FIG. 9B  is a schematic enlarged plan view of an opening of a first covering member in a second variation of the surface-emitting light source according to one embodiment. 
         FIG. 9C  is a schematic enlarged plan view of an opening of a first covering member in a third variation of the surface-emitting light source according to one embodiment. 
         FIG. 9D  is a schematic enlarged plan view of an opening of a first covering member in a fourth variation of the surface-emitting light source according to one embodiment. 
         FIG. 10  is a schematic cross-sectional view illustrating another configuration of the wiring substrate in the surface-emitting light source according to one embodiment. 
         FIG. 11A  is a schematic view illustrating a first variation of the step of pressing in the method of manufacturing the surface-emitting light source according to one embodiment. 
         FIG. 11B  is a schematic view illustrating a second variation of the step of pressing in the method of manufacturing the surface-emitting light source according to one embodiment. 
         FIG. 12  is a flowchart illustrating another method of manufacturing the surface-emitting light source according to one embodiment. 
         FIG. 13A  is a schematic enlarged view illustrating a relationship between an opening formed in a first covering layer and a wiring pad in the another method of manufacturing the surface-emitting light source according to one embodiment. 
         FIG. 13B  is a schematic cross-sectional view taken along a line XIIIB-XIIIB of  FIG. 13A . 
         FIG. 13C  is a schematic cross-sectional view taken along a line XIIIC-XIIIC of  FIG. 13A . 
         FIG. 13D  is a schematic cross-sectional view taken along a line XIIID-XIIID of  FIG. 13A . 
         FIG. 14A  is a schematic enlarged view illustrating a relationship between an opening, formed on a first covering layer, in another shape and a wiring pad in the another method of manufacturing the surface-emitting light source according to one embodiment. 
         FIG. 14B  is a schematic cross-sectional view taken along a line XIVB-XIVB of  FIG. 14A . 
         FIG. 14C  is a schematic cross-sectional view taken along a line XIVC-XIVC of  FIG. 14A . 
         FIG. 14D  is a schematic cross-sectional view taken along a line XIVD-XIVD of  FIG. 14A . 
         FIG. 15A  is a schematic plan view illustrating a first variation of supplied state of the electrically-conductive member, which is a variation of the supplied state of the electrically-conductive member in  FIG. 4 . 
         FIG. 15B  is a schematic plan view illustrating a second variation of supplied state of the electrically-conductive member, which is a variation of the supplied state of the electrically-conductive member in  FIG. 9A . 
         FIG. 15C  is a schematic plan view illustrating a third variation of supplied state of the electrically-conductive member, which is a variation of the supplied state of the electrically-conductive member in  FIG. 9B . 
         FIG. 15D  is a schematic plan view illustrating a fourth variation of supplied state of the electrically-conductive member, which is a variation of the supplied state of the electrically-conductive member in  FIG. 9C . 
         FIG. 15E  is a schematic plan view illustrating a fifth variation of supplied state of the electrically-conductive member, which is a variation of the supplied state of the electrically-conductive member in  FIG. 9D . 
         FIG. 15F  is a schematic plan view illustrating a sixth variation of openings of a covering layer and supplied state of the electrically-conductive member. 
         FIG. 16A  is a schematic cross-sectional view taken along a line XVIA-XVIA of  FIG. 15A . 
         FIG. 16B  is a schematic cross-sectional view taken along a line XVIB-XVIB of  FIG. 15A . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Drawings referred to in the descriptions below schematically illustrate certain embodiments of the present disclosure. 
     Scales, distances, positional relationships, and the like of members may be exaggerated, or illustration of some members may be omitted. Scales of members and distances between members are not necessarily the same. In the descriptions below, the same terms or reference numerals generally represent the same member or a member made of the same or similar material, and its detailed description may be appropriately omitted. In a configuration of a wiring substrate, the directions indicated by terms “upper”, “lower”, “left”, and “right” are interchangeable in accordance with the circumstances. In the present specification, the terms “upper”, “lower”, etc., are intended to represent a relative position between the components in the drawing that is referenced for description, but is not intended to represent an absolute position unless specifically stated otherwise. 
     Surface-Emitting Light Source 
     A surface-emitting light source  100  will be described referring to  FIGS. 1 to 6 . 
     The surface-emitting light source  100  includes a wiring substrate  20 , a plurality of light-emitting modules  10 , and an adhesive layer (an adhesive sheet)  30  disposed between the wiring substrate  20  and the plurality of light-emitting modules  10 . The wiring substrate  20  includes a base member  11 , a wiring layer (a first wiring layer)  17  disposed on a rear surface of the base member  11  opposite to a surface at a light-emitting modules  10  side, electrically-conductive members  13  each supplied across corresponding two or more vias  16  of a plurality of vias  16  each formed for a corresponding one of wiring pads  18 , the wiring pads  18  being portions of the wiring layer (the first wiring layer)  17 , a covering layer (a first covering layer)  12  covering the wiring layer (the first wiring layer)  17  and defining openings H in each of which a corresponding portion of a corresponding one of the wiring pads  18  is exposed, each of the openings H overlapping at least a portion of a corresponding one of the vias  16 . Each of the light-emitting modules  10  has an array of a plurality of light emitting devises  1 . The first covering layer  12  defines openings H at locations corresponding to the wiring pads  18  with an area dimension smaller than respective area dimensions of the wiring pads  18  in a plan view. 
     Configurations of the surface-emitting light source  100  will be described below. 
     Wiring Substrate 
     The wiring substrate  20  includes the base member  11  and the first wiring layer  17  disposed on the base member  11  and including the wiring pads  18  each defining corresponding two or more of the plurality of vias  16 . The vias are through-holes formed in the wiring pads  18  and the base member  11 . In the example herein, in the wiring substrate  20 , the wiring layer (hereinafter may be referred to as the first wiring layer)  17 , the covering layer (hereinafter may be referred to as the first covering layer)  12  covering the first wiring layer  17 , and the electrically-conductive members  13  each supplied into corresponding ones of the vias  16  each formed in a corresponding one of the wiring pads  18 , which are portions of the first wiring layer  17 , are disposed at a rear surface side of the base member  11 . Further, protective members  19  may be disposed to protect respective corresponding ones of the electrically-conductive members  13  as described below. In the wiring substrate  20 , a wiring layer (hereinafter referred to as a second wiring layer)  14  and a covering layer (hereinafter referred to as a second covering layer)  15  covering the second wiring layer  14  are formed on a front surface side of the wiring substrate  20 . The wiring substrate  20  includes the plurality of light-emitting modules  10  at the front surface side of the wiring substrate  20  through the adhesive layer  30 . 
     A material having a low elasticity is used for the base member  11  of the wiring substrate  20 . Examples of such a material include insulating resin materials such as phenolic resins, epoxy resins, polyimide resins, polyethylene terephthalate, polyethylene naphthalate, silicone resins, BT resins, and polyphthalamide. The base member  11  may have a structure in which a layer made of an insulating member is disposed on a surface of a metal member. A rigid substrate or a flexible substrate can be used for the base member  11 . The wiring substrate  20  may have a structure in which a plurality of base members  11  are layered. When a plurality of base members  11  are layered and vias are for respective corresponding ones of the layered base members, the vias in different layers of the layered base members may be formed at the same position or slightly different positions in a plan view. 
     The first wiring layer  17  is disposed on the rear surface of the base member  11  in a predetermined circuit pattern. The first wiring layer  17  includes the wiring pads  18  each of which has a rectangular shape, and narrow wirings  18   c  each connecting corresponding ones of the wiring pads  18 . The wiring pads  18  includes positive wiring pads  18 A and negative wiring pads  18 B arrayed in a matrix of rows and columns at respective predetermined intervals. The wirings  18   c  that are connected to the positive wiring pads  18 A are located at a predetermined distance from the positive wiring pads  18 A of adjacent rows. Alternatively, the wirings  18   c  that are connected to the negative wiring pads  18 B are located at a predetermined distance from the negative wiring pads  18 B of adjacent rows. Increase of areas occupied by the wirings in the first wiring layer  17  allows for reducing unevenness in a thickness of the wiring substrate  20 , so that adhesion of the wiring substrate  20  and the light-emitting modules  10  in a step S 15  of pressing described below can be enhanced. 
     Each of the wiring pads  18  has a rectangular region with a width larger than the narrow wiring  18   c . In the example herein, the positive wiring pads  18 A have a rectangular shape of a predetermined size and are disposed at a predetermined interval from one side of the narrow wiring  18   c . Each of the negative wiring pads  18 B is disposed between adjacent ones of the positive wiring pads  18 A at a predetermined interval to have a rectangular shape. That is, each positive wiring pad  18 A is disposed adjacent to a corresponding one of the negative wiring pads  18 B. In the example herein, a single positive wiring pad  18 A and a single negative wiring pad  18 B form a pair, and are connected to element electrodes of a single light emitting device  1 . The wiring pad  18  has an area larger than the area dimension of vias  16  even in the case in which two or four vias  16  are formed. 
     The second wiring layer  14  is disposed on the front surface side of the base member  11 . The second wiring layer  14  is provided together with the first wiring layer  17  to supply electric power to the light emitting device  1  from an external component. The second wiring layer  14  has a narrow-linear shape or a rectangular shape and is disposed on the front surface side of the base member  11  to have a predetermined circuit pattern. It is desirable that a portion of the second wiring layer  14  without the wirings does not overlap a portion of the first wiring layer  17  without the wirings. When the portion of the second wiring layer  14  without the wirings is formed at a position that does not overlap the portion of the first wiring layer  17  without the wirings, in a thickness direction of the wiring substrate  20 , a metal material of the second wiring layer  14  and/or the first wiring layer  17  is disposed in a layering direction. This allows for reducing unevenness in the thickness of the wiring substrate  20  at the time of pressing the wiring substrate  20  together with the light-emitting modules  10  as described below, so that bonding state can be improved. 
     For the first wiring layer  17  and the second wiring layer  14 , a metal material can be used, and for example, a single metal such as Ag, Al, Ni, Rh, Au, Cu, Ti, Pt, Pd, Mo, Cr, and W, or an alloy of these metals can be preferably used. A single metal having high light reflectivity such as Ag, Al, Pt, and Rh, or an alloy of these metals can be more preferably used. 
     In this example, two holes are formed in each wiring pad  18  and is continuous to holes in the base member  11  to create the vias  16 . The vias  16  are created by covering through-holes  160  extending through the adhesive layer  30  and the base member  11 , as described below. The vias  16  reaches a wiring layer  6  of the light-emitting module to be described below to form a hole formed with a bottom defined by the wiring layer  6  of the light-emitting module. The via  16  has a diameter of for example, 0.1 mm or more, more preferably 0.3 mm or more to reduce unevenness in connection resistance and to stabilize the luminance. Each of the vias  16  preferably has an aspect ratio of the diameter to the depth of 0.75 or less, more preferably 0.5 or less to easily supply the electrically-conductive member  13  into the via  16 . Also, having a gap G 01  of 0.1 mm or more and 0.3 mm or less between two vias  16  in each wiring pad  18  allows for reducing the connection resistance, and thus is preferable. The via  16  has an opening having a shape of, for example, a circular shape, an oval shape, a rectangular shape, a rhombus shape, a triangular shape, or a cross shape. One or more vias are formed in the wiring pads  18 . 
     In the example herein, two vias each having an opening of a circular shape are formed in each wiring pad  18 . 
     Each of the electrically-conductive members  13  is supplied into corresponding ones of the vias  16  to conduct electricity such that current from an external component is supplied to the arrayed light emitting devices  1 . In the present embodiment, each electrically-conductive member  13  is supplied across two corresponding vias  16 . Each of the wiring pads  18  may define a plurality of vias  16 , and electrically-conductive members  13  may be respectively supplied into the plurality of vias  16 . When each of the wiring pads  18  defines a plurality of vias  16 , each electrically-conductive member  13  may be supplied across corresponding two or more vias  16  of the plurality of vias  16 . The electrically-conductive members  13  are supplied from the rear surface side of the wiring substrate  20  into respective corresponding ones of the vias  16  such that each electrically-conductive member  13  is supplied across corresponding ones of the vias  16 . That is, each electrically-conductive member  13  is supplied into two corresponding vias  16  of the plurality of vias  16 , and is also disposed on a portion of a surface of a corresponding wiring pad  18  between the two corresponding vias  16 . The expression “a portion of a surface of a corresponding wiring pad  18 ” as used herein refers to a portion of a peripheral part of the via  16 . That is, each electrically-conductive member  13  is disposed to have a supplied portion that is supplied into two vias  16  and an intermediate portion that is disposed across the supplied portions on a portion of a surface of a corresponding wiring pad  18 . The intermediate portion of each electrically-conductive member  13  has a predetermined thickness of, for example, equal to or smaller than a thickness of the first covering layer  12 . While the supplied portion of the electrically-conductive member is preferably supplied into an entirety of corresponding vias  16 , it is sufficient that the supplied portion of the electrically-conductive member is disposed in the corresponding vias  16  at least at an amount that allows for establishing electrical connection. 
     Examples of the electrically-conductive member  13  include a mixture of a filler such as flaky, scaly, or barky silver or copper powder and a thermosetting binder resin can be used. For the electrically-conductive member  13 , a material with as small a volume resistance as possible and small contents of the binder resin and a solvent component is preferably used. In one example, as will be described below in description of a method of manufacturing, the electrically-conductive members  13  are disposed by screen printing through opening holes of a mask such that each electrically-conductive member  13  has supplied portions that are supplied into two vias  16  and an intermediate portion that is disposed across the supplied portions on a portion of a surface of a corresponding wiring pad  18 . 
     The protective members  19  made of an insulating resin and the like may be disposed to cover respective corresponding ones of electrically-conductive members  13 . Each protective member  19  protects a corresponding wiring pad  18  and a corresponding electrically-conductive member  13 . A phenyl silicone resin and a dimethyl silicone resin may be used for the protective members  19 . The protective members  19  may contain a pigment to be an opaque protective member. 
     The first covering layer  12  has a predetermined thickness and covers a predetermined region to protect the first wiring layer  17  and the like on the wiring substrate  20 . A resin that is the same as a resin used for the protective members  19  may be used for the first covering layer  12 , or polyimide may be used as a base material of the first covering layer  12 . The first covering layer  12  is disposed on the wiring pad  18  to form openings H each of which has an area smaller than the area of a corresponding wiring pad  18 . Accordingly, a portion of the first covering layer  12  covers a portion of a corresponding one of the wiring pads  18  and a portion of the rest of the corresponding wiring pad  18  is exposed from the first covering layer  12  through a corresponding one of the openings H. In one example, the openings H of the first covering layer  12  has a rectangular shape. In a plan view, openings of two vias  16  are formed at an approximately center region inside each rectangular opening H of the first covering layer  12 . 
     That is, each opening H has a size that allows a plurality of vias  16  in a corresponding wiring pad  18  to be exposed from a single opening H of the first covering layer  12 . Each opening H has an opening periphery apart from opening peripheries of the vias  16 . The opening H may be formed at a location corresponding to the wiring pad  18  at the center of the wiring pad  18  or along any of sides of the rectangular wiring pad  18  within the wiring pad  18 . The opening H may have a bilaterally symmetric shape with respect to the center or the center line of corresponding vias  16  in a plan view. The opening H in an example herein is formed to have an elongated rectangular shape (a rectangular shape) such that the center line passing through the center of the rectangular shape substantially corresponds to a center line passing through the centers of the vias  16 . 
     The adhesive layer  30  bonds the light-emitting modules  10  and the wiring substrate  20 . 
     A low elasticity material is used for the adhesive layer  30 . In particular, the light-emitting modules  10  contain different materials and physical properties, such as a light-emitting element  2 , a light guide plate  7 , and a light-reflective member  8 . Accordingly, an adhesive layer having a low elasticity is a preferable component for connection with the wiring substrate  20 . The adhesive layer  30  preferably has an elasticity lower than the elasticity of the base member  11 . 
     In general, in a wiring substrate as described in Japanese Unexamined Patent Application Publication No. 2006-237232, the greater the number of coverlay openings formed in a coverlay, which is a covering layer to protect the wirings, the smaller the diameter of the coverlay openings. The coverlay opening of the wiring substrate to be used in the dry process has a size greater than a width of wirings. Accordingly, in the coverlay opening, height differences between the wiring and the base member surface of the wiring substrate and between the coverlay and the base member surface of the wiring substrate occur, which generates spaces. At the time of pressing, a predetermined pressure is not easily applied to such spaces inside the coverlay opening, and the smaller the coverlay opening is, the less easily the pressure is conveyed. Further, at the time of pressing the wiring substrate having an elasticity of 2 Gpa or more and 5 Gpa or less and light-emitting modules including a hard polycarbonates through a low-elastic adhesive sheet having an elasticity of 100 Mpa or more and 1 Gpa or less, the low-elastic adhesive sheet flows in a direction toward the space having a smaller pressure due to the height differences. Accordingly, a portion of insufficient adhesion may be generated between the adhesive layer and the light-emitting modules. In the portion of insufficient adhesion, an air gap may be generated due to thermal expansion of a resin material. This may adversely affect the connection of vias, so that reliability of connection may be decreased. 
     On the other hand, the first covering layer  12  in the present embodiment defines the openings H of the present embodiment on or above the wiring pad  18 . 
     Thus, height difference due to difference in the thicknesses of the first wiring layer  17  and the base member  11  in the thickness direction of the base member  11  does not occur around the wiring pad  18 . Accordingly, when the base member  11  has an elasticity of 2 Gpa or more and 5 Gpa or less and the adhesive layer  30  has an elasticity of 100 Mpa or more and 1 Gpa or less, at the time of pressing the wiring substrate  20  and the light-emitting modules  10 , unevenness in the thickness of the wiring substrate  20  can be reduced, which can improve bonding state. While a configuration in which a single opening H having a rectangular shape is formed for a plurality of vias  16  on a single wiring pad  18  is described above in one example, the openings H may have any appropriate shapes, and any appropriate number of the openings H may be formed. In another example of configuration as will be described below, the opening may be defined corresponding to the wiring pad  18  to partially overlap a portion of the vias  16  with an area dimension smaller than respective area dimensions of the wiring pad  18 . 
     Light-Emitting Module, Light Emitting Device, Light-Emitting Element 
     As shown in  FIGS. 1 to 6 , each light emitting device  1  includes, for example, a light-emitting element  2 , a light-transmissive member  3  disposed on a light-extracting surface side of the light-emitting element  2 , a covering member (a white resin)  4  directly or indirectly disposed on lateral surfaces of the light-emitting element  2 , a light guide plate  7  including an optical function portion  7   a  and disposed on the light-transmissive member  3 , and a light-reflective member  8  covering a lower surface of the light guide plate  7 , lateral surfaces of the light-transmissive member  3 , and lateral surfaces of the covering member  4 . The element electrodes  5  of the light-emitting element  2  in the light emitting device  1  are connected to the wiring layer  6  of the light-emitting module formed opposite to the light guide plate  7 . When a single light emitting device  1  corresponds to a single cell SL (see  FIG. 2 ), a plurality of cells are arrayed adjacently in the longitudinal and lateral directions to form the light-emitting module  10 . The light-emitting module  10  is composed of, for example, 16 cells in a matrix of four by four cells. In the surface-emitting light source  100 , for example, 76 light-emitting modules  10  are arrayed. 
     For the light-emitting element  2 , a known semiconductor light-emitting element can be used, and for example, a light-emitting diode element may be used for the light-emitting element  2 . A light source configured to emit blue light can be used for the light-emitting element  2 . Alternatively, a plurality of light-emitting elements configured to emit different colors can be used to emit white light by mixing the lights of, for example, red, blue, and green colors. An element configured to emit light with any appropriate wavelength can be selected for the light-emitting element  2 . The composition, emission color, size, number, and the like of the light-emitting elements to be used can be selected appropriately according to the purpose. Examples of elements configured to emit blue and green light include a light-emitting element including a nitride semiconductor (In X Al Y Ga 1-X-Y N, 0≤X, 0≤Y, X+Y≤1) or GaP. A light-emitting element containing a semiconductor such as GaAlAs or AlInGaP can be used for an element configured to emit red light. A semiconductor light-emitting element made of materials other than material described above can be used. 
     Various light emission wavelength can be selected by selecting various materials for the semiconductor layers and various mixing ratios of the materials. 
     The element electrodes  5  of the light-emitting element  2  are disposed at a side opposite to a side at which the light-transmissive member  3  is disposed, and are exposed from the lower surface of the covering member  4  to be described below. The element electrodes  5  include a negative electrode and a positive electrode disposed with a gap therebetween, and may be arranged diagonally or along two opposite sides of the light-emitting element  2  of a rectangular shape in a plan view. 
     The light-transmissive member  3  is made of a light-transmissive material containing a phosphor. A material having a higher refractive index than that of a material of the light-guiding plate  7  is preferably used for the light-transmissive material. Epoxy resins, silicone resins, mixtures of these resins, or glass and the like may be used. In view of resistance to light and ease of formation, silicone resins are preferably selected. 
     The range of wavelength into which a phosphor wavelength-converts varies according to types of phosphors. 
     An appropriate phosphor for the light-transmissive member  3  needs to be selected to convert into a desired wavelength. Examples of the phosphor include YAG phosphors, LAG phosphors, chlorosilicates phosphors, β-SiAlON phosphors, CASN phosphors, SCASN phosphors, and fluoride phosphors such as KSF phosphors. In particular, with a single light-transmissive member  3  containing a plurality of phosphors, more preferably, with the light-transmissive member  3  containing β-SiAlON phosphors adapted to emit green light and fluoride phosphors such as KSF phosphors adapted to emit red light, the color reproduction range of the light-emitting module can be expanded. 
     Further, with the light-transmissive member  3  containing a phosphor adapted to emit light having a predetermined color, light having a specific color can be emitted from the light-transmissive member  3 . Quantum dots may be used for the light-transmissive member  3 . The phosphor may be disposed in appropriate arrangement within the light-transmissive member  3 . An effective arrangement of the phosphor, such as substantially even distribution, uneven distribution, and a layered structure having a plurality of layers each containing a different wavelength conversion material, can be selected. 
     The light-transmissive member  3  may include a diffusing member on the light-extracting surface side. 
     The covering member  4  is disposed directly on the lower surface of the light-transmissive member  3  and the lateral surfaces of the light-emitting element, or disposed on the lateral surfaces of the light-emitting element via the light-transmissive adhesive member. The covering member  4  may have a reflectance of 60% or more, preferably 90% or more, with respect to the light emitted from the light-emitting element  2 . The covering member  4  has an outer periphery similar to the outer periphery of the light-transmissive member  3  in a plan view. The covering member  4  has a length between the lower surface of the light-transmissive member  3  (the upper surface of the covering member  4 ) and the lower surface of the covering member  4  that allows the element electrodes  5  to be exposed from the covering member  4 . 
     The light guide plate  7  is a light-transmissive member on which light emitted from the light source is incident and from which light is surface-emitted. The light guide plate  7  may have the optical function portion  7   a  on a first main surface serving as the light-emitting surface, and may define a recess to accommodate the light-transmissive member  3  or the light emitting device  1  in a second main surface opposite to the first main surface. The light guide plate  7  may define a through-hole extending through the first main surface and the second main surface, the through-hole can accommodate the light-transmissive member  3  or the light emitting device  1 . The light guide plate  7  may include a plurality of optical function portions  7   a  on the first main surface. 
     For the light guide plate  7 , resin materials such as thermoplastic resins including acrylic resins, polycarbonates, cyclic polyolefins, polyethylene terephthalate, and polyesters, and thermosetting resins including epoxy resins and silicone resins, or a light-transmissive material such as glass can be used. In particular, thermoplastic resin materials can be efficiently manufactured using injection molding, and thus is preferably used. Among these materials, polycarbonates, which are highly transparent and inexpensive, are more preferable. When manufacturing the surface-emitting light source  100  in which the wiring layer  6  of the light-emitting module is formed after the light-emitting element  2  is mounted on the light guide plate  7 , a step performed under high temperature such as solder reflow can be omitted. This allows for using a thermoplastic material with a low thermal resistance such as polycarbonates. The light guide plate  7  may be formed using, for example, an injection molding or a transfer molding. 
     The optical function portion  7   a  reflects light emitted from the light-emitting element  2  to spread the light outward in a radial direction to obtain uniform the emission intensity in a plane of the light guide plate  7 . Various configurations, for example, a light-reflective or light-diffusing member, such as lenses, on the light guide plate  7  can serve as the optical function portion  7   a . For example, the optical function portion  7   a  may have an interface with a substance, such as air, having a refractive index different from that of a material of the light guide plate  7 . In the example herein, the optical function portion  7   a  is a recess having an inverted cone shape, and the size and the shape of the recess may be appropriately selected. More specifically, the optical function portion  7   a  may be a recess having a shape of an inverted polygonal pyramid such as an inverted quadrangular pyramid or an inverted hexagonal pyramid. The optical function portion  7   a  in the example herein is such a recess configured to reflect light irradiated to the interface between the substance having a refractive index different from that of a material of the light guide plate  7  and an inclined surface of the recess toward lateral directions of the light-emitting element  2 , that is, in the radial direction with respect to the optical function portion  7   a . The optical function portion  7   a  may have a structure in which, for example, a reflective film made of a metal or the like and a reflective material such as a white resin is disposed in the recess defined by an inclined surface having a linear or curved shape in a cross-sectional view. The optical function portion  7   a  is preferably formed such that optical axis of the light-emitting element  2  and the optical axis, which is the center of the optical function portion  7   a  (the deepest portion of the recess), of the optical function portion  7   a  substantially corresponds on the extended line. 
     The light-reflective member  8  protects the light-emitting element  2  and the light guide plate  7  and reflects light from the lateral surfaces of the light-emitting element  2  toward the light-emitting surface. The light-reflective member  8  is desired to have a reflectance of 60% or more, preferably 90% or more, of light emitted from the light-emitting element  2 . The light-reflective member  8  made of a reflective material can efficiently guide the light emitted from the light-emitting element  2  to the light guide plate  7 . With the light-reflective member  8  serving as both a member that protects the light-emitting element  2  and a reflective member disposed on a surface opposite to the emission surface of the light guide plate  7 , a thickness of the light-emitting module  10  can be reduced. 
     A resin containing a white pigment and the like is preferably used for a material of the light-reflective member  8 . A relatively large amount of a material is used for the light-reflective member  8  to cover a surface of the light guide plate  7 . Accordingly, silicone resins containing titanium oxide, which is inexpensive, are preferably used for the light-reflective member  8  to reduce the cost of the light-emitting module  10 . 
     In one example, the light-emitting element  2  and the light-transmissive member  3  are bonded through the light-transmissive adhesive member. When the light-transmissive adhesive member is disposed between the light-extracting surface of the light-emitting element  2  and the light-transmissive member  3 , the light-transmissive adhesive member is preferably formed into fillets on lateral surfaces of the light-emitting element  2 . For the light-transmissive adhesive member formed into fillets on the lateral surfaces of the light-emitting element  2 , a known adhesive such as silicone resins and the like can be used. 
     The wiring layers  6  of the light-emitting module that are electrically connected to respective ones of the element electrodes  5  of the plurality of light-emitting elements  2  are disposed on the lower surface of the light-reflective member  8 . The wiring layers  6  of the light-emitting module are formed on a surface facing the light-reflective member  8  and the element electrodes  5  of the light-emitting element  2 . The wiring layers  6  of the light-emitting module are connected to the electrically-conductive members  13  in the vias  16  formed to extend through the wiring substrate  20  and the adhesive layer  30  from the rear surface of the wiring substrate  20 . This allows the plurality of light emitting devices  1  to be electrically connected. 
     A covering layer made of an insulating member  9  for the wiring layer  6  of the light-emitting module is preferably disposed at predetermined positions of the wiring layer  6  of the light-emitting module having the same configuration as the first covering layer  12 . The insulating member  9  is n a form of a film defining an opening over the wiring layer  6  of the light-emitting module at a region in contact with the through-hole  160  (see  FIG. 8B ) of the wiring substrate  20 . 
     The light-emitting modules  10  are bonded to the wiring substrate  20  through the adhesive layer  30 , so that the surface-emitting light source  100  is obtained. The adhesive layer  30  used in the example herein bonds the light-emitting modules  10  and the wiring substrate  20 , and is desirably made of a material having a low elasticity for reducing warpage of the surface-emitting light source  100  due to the difference of linear expansion coefficients between the light-emitting module  10  and the base member  11 . It is desirable that a sheet-like resin material having a low elasticity such as an acrylic resin, a silicone resin, or a urethane resin is used for the adhesive layer  30 . The elasticity of a material for the adhesive layer  30  is preferably 100 MPa or more and 1 GPa or less. Using such a material allows for ensuring adhesion between the light-emitting module  10  and the wiring substrate  20  and reducing warpage. The adhesive layer  30  needs to have a thickness that allows for absorbing the height differences generated due to presence of the first wiring layer  17  and/or the second wiring layer  14  on the wiring substrate  20 . The adhesive layer  30  preferably has a thickness of two times or more, more preferably four times or more of a thickness of the first wiring layer  17  or the second wiring layer  14 . For example, when a copper foil of 18 μm is used for the second wiring layer  14 , the thickness of the adhesive layer  30  is preferably 36 μm or more, more preferably 72 μm or more. A material for the adhesive layer  30  preferably has a high frame resistance. 
     Next, a method of manufacturing the surface-emitting light source  100  will be described referring to  FIG. 7  and  FIGS. 8A to 8F . 
     A method of manufacturing a surface-emitting light source according to one embodiment of the present disclosure includes: a step S 11  of providing a wiring substrate, a step S 12  of forming through-holes, a step S 13  of creating vias, a step S 14  of supplying, and a step S 15  of pressing. In the step S 11  of providing a wiring substrate, a wiring substrate  20  is provided, the wiring substrate  20  including a base member  11 , a wiring layer (a first wiring layer  17 ) disposed on a rear surface of the base member  11 , wiring pads  18  each of which is a portion of the first wiring layer  17 , and a first covering layer  12  covering the first wiring layer  17  and defining openings H from each of which a portion of a corresponding one of the wiring pads  18  is exposed, each of the openings H having a size smaller than an area of the wiring pad  18  in a plan view. In the step S 12  of forming through-holes, an adhesive layer  30  is disposed on a front surface side of the base member  11  and through-holes are formed on a corresponding one of the wiring pads  18  through the opening H such that the through-holes extend through the wiring substrate  20  and the adhesive layer  30 . In the step S 13  of creating vias, a plurality of light emitting modules  10  each having an array of a plurality of light emitting devices  1  are temporarily connected to the front surface side of the base member  11 , such that openings of the plurality of through holes  160  formed in the front surface side of the base member  11  are covered by the plurality of light emitting devices  1 , such that a plurality of vias  16  are created from the plurality of through holes  160 . In the step S 14  of supplying, the electrically-conductive material  13  is supplied into respective corresponding ones of the vias  16 . In the step S 15  of pressing, the wiring substrate  20  and light-emitting modules  10  are pressed and heated to be bonded using the adhesive layer  30 . 
     In the step S 11  of providing a wiring substrate, the wiring substrate  20  having the first wiring layer  17  and the first covering layer  12  on the rear surface of the base member  11  is provided. In the step of providing a wiring substrate, the wiring pads  18  that are portions of the predetermined wiring pattern disposed on the rear surface of the base member  11 , and narrow wirings  18   c  each connected to corresponding ones of the wiring pads  18  are disposed. The wiring pads  18  are arranged such that a positive wiring pad  18 A and a negative wiring pad  18 B are alternately disposed at predetermined intervals along a straight line and arrayed in a matrix direction. In the first wiring layer  17 , for example, a circuit pattern is formed from a metal layer made of a copper foil. In the case of forming the circuit pattern on the rear surface or the front surface of the base member  11 , for example, the circuit pattern may be a layered structure of metal layers. Examples of a method of forming the metal layers include directly depositing the wiring pads  18  and the narrow wirings  18   c  to form a predetermined wiring pattern using a plating technique or vapor phase film forming techniques (sputtering, ion plating, electron beam evaporation, vacuum deposition, chemical vapor deposition, and the like). In terms of cost and productivity, it is advantageous that the metal layer is bonded to the front surface of the base member  11  by a urethane adhesive. In the step S 11  of providing a wiring substrate, the second wiring layer  14  may be disposed on the front surface of the base member  11  as well as the first wiring layer  17 . 
     Next, the first covering layer  12  is disposed on the base member  11  including a first wiring layer  17  such that the first covering layer  12  defines the openings H at locations corresponding to the wiring pads  18 , which are portions of the first wiring layer  17 . The first covering layer  12  can be disposed, for example, using a printing technique such as screen printing, and other known technique according to the employed material for the covering layer. The first covering layer  12  is disposed on the wiring pads  18  by screen printing using a mask and the like such that the wiring pads  18  are partially exposed through the openings H. The openings H has an area dimension smaller than the area dimensions of respective wiring pads  18 , and each opening H has a size that allows the plurality of vias  16  for each wiring pad  18  to be exposed in a single opening H of the first covering layer  12 . In the case of forming the second wiring layer  14 , a second covering layer  15  is disposed to cover the second wiring layer  14  at predetermined positions using a technique as described above. 
     Next, the step S 12  of forming through-holes is performed. In the step S 12  of forming through-holes, the adhesive sheet serving as the adhesive layer  30  is bonded to the front surface side of the provided wiring substrate  20 . At this time, in an example herein, the adhesive sheet having adhesive surfaces on two opposite sides and provided with a separator (a releasing paper) at a front surface of the adhesive sheet is used, the adhesive sheet configured such that the adhesive surface appears by removing the separator. In the step S 12  of forming through-holes, the through-holes  160  are formed through the openings H for respective wiring pads  18  to extend through the wiring substrate  20  and the adhesive layer  30 . The through-holes  160  are formed through the opening H of the first covering layer  12  to extend through the wiring substrate  20  and the adhesive layer  30  by drilling, punching, or the like. A plurality of the through-holes  160  (in the example herein, two through-holes  160 ) are formed within the area of the wiring pad  18  in a plan view. 
     Next, the step S 13  of creating vias is performed. In the step S 13  of creating vias, the separator (the releasing paper) of the adhesive layer  30  on the other surface to be bonded to the wiring substrate  20  is removed, and the plurality of light-emitting modules  10  are temporarily connected to the other surface of the adhesive layer. The expression “connect” as used in the present embodiment includes not only electrically connecting but also joining the wiring substrate  20  and the light-emitting module  10 ″. The light-emitting module  10  is configured such that the wiring layer  6  of the light-emitting module is exposed from the insulating member  9  at predetermined positions at the lower surface side of the light-emitting module  10 . In the step S 13  of creating vias, the wiring substrate  20  and the light-emitting module  10  are temporarily connected through the adhesive layer  30  such that, in the light-emitting module  10 , the wiring layer  6  of the light-emitting module faces the openings of the through-holes  160  formed in the wiring substrate  20  at the front surface side of the light-emitting module  10 . In the step S 13  of creating vias, the light-emitting module  10  is temporarily connected to the front surface side of the wiring substrate  20  through the adhesive layer  30  to cover one end of each of the through-holes  160 , so that vias  16  are created. 
     In one example, the light-emitting module  10  used in the step S 13  of creating vias is provided by manufacturing steps described below. A light guide plate  7  having provided with the optical function portion  7   a  and defining a recess to accommodate the light-transmissive member  3  is provided. 
     Next, the light-transmissive member  3  is disposed in the recess of the light guide plate  7 , and the light-extracting surface of the light-emitting element  2  is bonded to the light-transmissive member  3  using an adhesive such as a resin. Further, after forming the light-reflective member  8 , the wiring layer  6  of the light-emitting module to which the element electrodes  5  of the light-emitting element  2  are to be connected is formed. The light-emitting module  10  is provided by forming the insulating member  9  made of a protective insulating member is disposed on predetermined portions of the lower surface of the wiring layer  6  of the light-emitting module and the lower surface of the light-reflective member  8 . 
     In the step S 13  of creating vias, the wiring layer  6  of the light-emitting module faces the through-holes  160  extending through the wiring substrate  20  and the adhesive layer  30  to create vias  16  from the through-holes  160  by temporarily connecting each of the plurality of light-emitting modules  10  to the wiring substrate  20  through the adhesive layer  30 . 
     Next, the step S 14  of supplying is performed. In the step S 14  of supplying, an electrically-conductive material  13  such as electroconductive paste is supplied into the vias  16 . In the step S 14  of supplying, the electrically-conductive material  13  is supplied into the vias  16  such that the electrically-conductive material  13  is filled in the vias  16  and further on a portion of a surface of the wiring pad  18 , connecting respective adjacent two vias  16 . In the step S 14  of supplying, for example, a mask defining a plurality of openings is used. In one example, the plurality of openings of the mask are formed in an elongated circular shape corresponding to a shape surrounding the openings of the two vias  16 . In the present embodiment, the elongated circular shape refers to a ring shape having a major axis, a minor axis, and at least two curved lines. Each opening in the mask is formed and disposed for a respective one of the wiring pads  18 . When applying the electroconductive paste by moving a squeegee in an operation of printing such as screen printing, the electrically-conductive material  13  is supplied into the vias  16  through openings of the mask, and is disposed on portions of surfaces of wiring pads  18 . The electrically-conductive member  13  is printed to form the supplied portion supplied into the vias  16  and the intermediate portion disposed on a portion of a surface of the wiring pad  18 . In screen printing, the squeegee may be moved once, or may be reciprocated one or more times. 
     Next, the step S 15  of pressing is performed. In the step S 15  of pressing, the electrically-conductive material  13  is hardened to obtain electrically-conductive members  13 , and the wiring substrate  20  and the light-emitting module  10  are connected through the adhesive layer  30 . In the step S 15  of pressing, hardening may also be performed with reducing of a thickness of the intermediate portion of the electrically-conductive member  13  to be smaller than a thickness of the intermediate portion when the electrically-conductive member  13  is disposed through the opening of the mask. In the step S 15  of pressing, for example, using upper and lower heating platens HL 1  and HL 2  temperature of which can be controlled, pressing is performed during heating. Pressing may be performed with release films attached to the heating platens HL 1  and HL 2 . In the step S 15  of pressing, pressing is performed with the heating platens HL 1  and HL 2  heated at a predetermined temperature. This hardens the adhesive surface of the adhesive layer  30 , so that the wiring substrate  20  and the light-emitting module  10  are connected through the adhesive layer  30 . 
     In the step S 15  of pressing, when the upper and lower heating platens HL 1  and HL 2  press the wiring substrate  20 , the base member  11  is not exposed outward in a peripheral region of the wiring pad  18 . 
     With this structure, the opening H does not form a gap defined by the base member  11  and the first covering layer  12 . That is, the first covering layer  12  defines openings H at locations corresponding to the wiring pads  18  with an area dimension smaller than respective area dimensions of the wiring pads  18  in a plan view. With this structure, when a portion of the first covering layer  12  at the opening H is pressed using the heating platens HL 1  and HL 2 , the wiring pad  18  is pressed through the first covering layer  12 . Accordingly, in the wiring substrate and the light-emitting module  10 , no portion is pressed through a gap as in a conventional case. This allows for pressing at an appropriate pressure inside the opening H, so that the wiring substrate  20  and the light-emitting module  10  can be connected together on the respective sides of the adhesive layer  30  without air gaps. 
     Subsequently to the step S 15  of pressing, a step S 16  of disposing protective members may be performed. In the step S 16  of forming protective members, protective members  19  made of an insulating resin are disposed over the electrically-conductive member  13  that is pressed in the step S 15  of pressing. In the step S 16  of forming protective members, the protective member  19  made of an insulating resin is supplied from a surface side of the base member  11  so as to cover the wiring pad  18  to be pressed. The protective members  19  have a greater height than the height of the first covering layer  12  to cover respective electrically-conductive members  13 . When the electrically-conductive member  13  is supplied insufficiently to leave a gap inside the via  16 , the protective member  19  is also supplied into the gap in the via  16 . 
     As described above, in the surface-emitting light source  100 , the first covering layer  12  defines openings H at locations corresponding to the wiring pads  18  with an area dimension smaller than respective area dimensions of the wiring pads  18  in a plan view. This allows the wiring substrate  20  and the light-emitting module  10  to be pressed through the adhesive layer  30  such that a predetermined pressure is applied to the whole surface. Accordingly, in the surface-emitting light source  100 , insufficient adhesion can be prevented, which allows for reducing generation of an air gap at an interface between the adhesive layer  30  and the wiring layer  6  of the light-emitting module due to thermal expansion of a resin member, so that adverse effect to the connection through vias can be prevented, and accordingly reliability of connection can be increased. Also, in a manufacturing step of the surface-emitting light source  100 , connecting portions of the wiring substrate  20 , the adhesive layer  30 , and the light-emitting module can be appropriately pressed, and a volatile component of the electrically-conductive member  13  can be released from the opening H, allowing for pressing more appropriately than in a conventional configuration. Further, in the surface-emitting light source  100  and the method of manufacturing the same, adhesion of the adhesive layer  30  can be increased and via-resistance can be reduced. 
     Any appropriate shapes, number, and the like of the openings H may be defines in the first covering layer  12  corresponding to wiring pads  18 , and, for example, the opening H may be formed as shown in  FIGS. 9A to 9D . First to fourth variations of the opening H for each wiring pad  18  will be described below. Also, while an example in which the opening of the via  16  has a circular shape is described above, the opening of the via  16  may have any appropriate shape such as a rectangular shape, an oval shape, a triangular shape, a cross shape, a hexagonal shape, or the like. 
     As shown in  FIG. 9A , openings H 1  each corresponding to a respective one of two (a plurality of) vias  16  may be formed. The openings H 1  include a first rectangular opening H 11  facing one of the vias  16  and having a rectangular shape, and a second rectangular opening H 12  facing the other of the vias  16  and having a rectangular shape, which are arranged vertically adjacent to each other through a portion of the first covering layer  12  in a plan view. The first rectangular opening H 11  has a shape in which a portion of a periphery of an opening of a corresponding via  16  meet an upper end side of the rectangular shape in a plan view. The second rectangular opening H 12  has a shape in which a portion of a periphery of an opening of a corresponding via  16  meet a lower end side of the rectangular shape facing the first rectangular opening H 11 . 
     The first rectangular opening H 11  and the second rectangular opening H 12  are formed adjacent to each other in respective single vias  16  such that a portion of each of the first and second rectangular openings H 11  and H 12 , which is a periphery of a portion of the first covering layer  12 , meets a portion of a periphery of a respective one of the vias  16 . The openings H 1  have a bilaterally symmetric shape with respect to a line that connects the centers of the vias  16  vertically in a plan view. With a structure formed of the first rectangular opening H 11  and the second rectangular opening H 12 , the openings H 1  can correspond to the vias  16  disposed, for example, greatly spaced apart from each other on the wiring pad  18 . In the openings H 1 , one of the vias  16  is located in the first rectangular opening H 11  offset from the center of the first rectangular opening H 11  toward one side, and the other via  16  is located in the second rectangular opening H 12  offset from the center of the second rectangular opening H 12  toward another side. The via  16  is located at the center of the first rectangular opening H 11  or the second rectangular opening H 12 . 
     As shown in  FIG. 9B , openings H 2  that include a first rectangular opening H 21  and a second rectangular opening H 22  having a rectangular shape and formed at a predetermined interval at a left side and a right side of the via  16  that are vertically aligned in a plan view may be formed. A portion of the first rectangular opening H 21  is formed to overlap a portion of each of the plurality of vias  16  at one side (the right side) with respect to the centers of the vias  16 . The second rectangular opening H 22  is formed to overlap a portion of each of the plurality of vertically aligned vias  16  at another side (the left side) with respect to the centers of the vias  16 . The first rectangular opening H 21  and the second rectangular opening H 22  are disposed adjacent to each other through a portion of the first covering layer  12  and a portion of the via  16 . The openings H 2  have a bilaterally symmetric shape with respect to the line that vertically connects the centers of the vias  16  in a plan view. 
     As shown in  FIG. 9C , openings H 3  including a first rectangular opening H 31 , a second rectangular opening H 32 , a third rectangular opening H 33 , and a fourth rectangular opening H 34  that are aligned vertically and laterally to the vertically aligned vias  16  in a plan view. In the openings H 3 , the first rectangular opening H 31  and the second rectangular opening H 32  are formed adjacent to each other to overlap a portion of one of the vias  16 . 
     The third rectangular opening H 33  and the fourth rectangular opening H 34  are formed adjacent to each other to overlap a portion of another one of the vias  16 . Further, in the rectangular openings H 3 , the first rectangular opening H 31  and the third rectangular opening H 33  are disposed adjacent to each other through a portion of the first covering layer  12 , and the second rectangular opening H 32  and the fourth rectangular opening H 34  are disposed adjacent to each other through a portion of the first covering layer  12 . In a plan view, the openings H 3  have a bilaterally symmetric shape with respect to a line that vertically connects the centers of the vias  16 , and also have vertically symmetric in the vertical direction. 
     As shown in  FIG. 9D , a single opening H 4  having a rectangular shape may be formed for a plurality of vias  16  and having protruding side portions h 41 , h 42 , h 43 , and h 44  at upper, lower, left, and right parts of the rectangular opening to narrow the rectangular opening in a plan view. In the opening H 4 , the vias  16  are disposed at upper and lower sides with the left and right protruding portions h 43  and h 44  at the center. In a plan view, the opening H 4  has a bilaterally symmetric shape with respect to a line that vertically connects the centers of the vias  16 , and also has a vertically symmetric shape in the vertical direction. 
     In the surface-emitting light source  100  described above, the wiring substrate  20  includes the first wiring layer  17  and the first covering layer  12  on the rear surface of the base member  11 , and the second wiring layer  14  and the second covering layer  15  on the front surface of the base member  11 . 
     Meanwhile, as shown in  FIG. 10 , a wiring substrate including the first wiring layer  17  and the first covering layer  12  that are disposed on only the rear surface of the base member  11  may be used in the surface-emitting light source  100 . 
     In the method of manufacturing the surface-emitting light source  100 , pressing may be performed as shown in  FIGS. 11A and 11B . 
     As shown in  FIG. 11A , in the step S 15  of pressing, pressing may be performed using the heating platen HL 1 , which is a metal mold, through a sheet Pc 1  having a length L 11  and a thickness L 12  that are similar to the length L 1  and the hole depth L 2 , respectively, of the opening H in a plan view. The sheet Pc 1  for use is preferably an absorptive sheet made of paper and the like adapted to absorb molten binder resin contained in the electrically-conductive member  13  at the time of pressing. As such, in the step S 15  of pressing, removing excessive binder resin using the sheet Pc 1  at the time of hardening the electrically-conductive member  13  allows for reducing via resistance. The sheet Pc 1  for use in the example herein preferably has a thickness L 12  that is determined in consideration of the thickness of the electrically-conductive member  13  across two vias  16  on the wiring pad  18 . 
     As shown in  FIG. 11B , in the step S 15  of pressing, pressing may be performed using a heating platen HL 11  that is a metal mold having protrusions Dp forming a recess-and-protrusion pattern inverted with respect to a recess-and-protrusion pattern including recesses each formed between a surface of a respective wiring pad  18  and a surface of the first covering layer  12 . The protrusions Dp include first protrusions Dp 1  each corresponding to a respective one of the openings H and second protrusions Dp 2  each corresponding to a portion without wirings such as the wiring pads  18 . The first protrusions Dp 1  have a length L 21  and a protrusion height L 22  that are similar to the length L 1  and the hole depth L 2  of respective openings H in a plan view. The first protrusions Dp 1  have the height L 22  that is determined in consideration of a thickness of the electrically-conductive member  13  across two vias  16  on each wiring pad  18 . 
     The second protrusion Dp 2  has a height L 23  that allows for protruding by the thickness of the wirings such as the wiring pad  18 . The second protrusion Dp 2  is formed with an inverted protrusion pattern with respect to the protrusion pattern in which the protrusions from the base member  11  on a surface covered by the first covering layer  12  are formed by the first wiring layer  17  such as the wiring pad  18 . 
     By performing pressing using the metal mold having the protrusion Dp, the binder resin contained in the electrically-conductive member  13  can be extruded and removed, and an appropriate pressure can be applied to the wiring substrate  20 , the adhesive layer  30 , and the light-emitting modules  10 . 
     As shown in  FIGS. 11A and 11B , the wiring substrate  20  and the light-emitting modules  10  are appropriately connected through the adhesive layer  30  by pressing, so that reliability of connection can be further increased. 
     Next, another example of a method of manufacturing the surface-emitting light source will be described referring to  FIG. 12  and  FIGS. 13A to 14D . The steps that have been described above will be indicated by the same reference numeral, and repetitive descriptions thereof will be omitted as appropriate. While the wiring substrate  20  in the description below includes the second wiring layer  14  and the second covering layer  15 , the wiring substrate  20  may be configured without the second wiring layer  14  and the second covering layer  15 . 
     The method of manufacturing the surface-emitting light source includes, as shown in  FIG. 12 , a step S 11   a  of providing a wiring substrate, a step S 12  of forming through-holes, a step S 13  of creating vias, a step S 14  of supplying, a step S 14 A of disposing a first covering layer, a step S 15  of pressing, and a step S 16  of forming a protective member, in this order. 
     The difference from the method of manufacturing shown in  FIG. 7  is that the first covering layer is not disposed in the step S 11   a  of providing a wiring substrate. The first covering layer is disposed after the step S 14  of supplying. 
     In the step S 11   a  of providing a wiring substrate, the first wiring layer  17  is disposed on the rear surface of the base member  11 . In the step S 11   a  of providing a wiring substrate, the first covering layer  12  to cover the first wiring layer  17  is not formed at this time. In the wiring substrate  20  to be provided in the step S 11   a  of providing a wiring substrate, the second wiring layer  14  and the second covering layer  15  are disposed on the front surface of the base member  11 . 
     The step S 12  of forming through-holes is performed and the wiring substrate  20  and the adhesive layer  30 , which is an adhesive layer, are temporarily connected, and the through-holes  160  are also formed in the wiring pad  18  of the first wiring layer  17 . 
     Next, the step S 13  of creating vias is performed, and the step S 14  of supplying is performed. The step S 14  of supplying is performed before the step S 14 A of disposing a first covering layer. This can secure connection between metal members of the electrically-conductive member  13  and the wiring pad  18 . 
     In the step S 14 A of disposing a first covering layer, the first covering layer  12  is disposed on the electrically-conductive member  13  disposed inside the vias  16  and the wiring pad  18 . The first covering layer  12  defines openings H 5  at locations corresponding to the wiring pads  18  with an area dimension smaller than respective area dimensions of the wiring pads  18 . The opening H 5  have the same plan view shape as that of the opening H 2  described above. The opening H 5  of the first covering layer  12  is different from the configuration described above in that the first covering layer  12  is disposed on the electrically-conductive members  13  between a first rectangular opening H 51  and a second rectangular opening H 52  that are adjacent to each other. 
     After the step S 14 A of forming a first covering layer, a step S 15  of pressing is performed. In the step S 15  of pressing, pressing is performed in a manner as in any one of the manners shown in  FIGS. 8E, 11A, and 11B . The electrically-conductive member  13  supplied into the vias  16  is pressed to reduce its height on the wiring pad  18 , and accordingly a portion of the electrically-conductive member  13  located on the wiring pad  18  and covered by the first covering layer  12  has a height smaller than a thickness of the first covering layer  12 . The first covering layer  12  is pressed in a state where the opening H 5  has been formed corresponding to the wiring pad  18 . With this configuration, the volatile component of the electrically-conductive member  13  is released from the opening H 5 . 
     Also, with first covering layer  12  defining the openings H 5  on or above the wiring pad, the determined pressure can be appropriately applied to the wiring substrate  20  and the adhesive layer  30 , and via resistance can be reduced. 
     Next, the step S 16  of disposing a protective member is performed to dispose the protective member  19 , which is an insulating resin, in the opening H 5 . 
     In the method of manufacturing a surface-emitting light source shown in  FIG. 12  and  FIGS. 13A to 13D , the first covering layer  12  may be disposed on the first wiring layer  17  to form an opening H 6  as shown in  FIGS. 14A to 14D . The opening H 6  has the same plan view shape as that of the opening H 3  described above. The configuration shown in  FIGS. 14A to 14D  is obtained through the same steps as the steps described above through which the configuration shown in  FIG. 12  and  FIGS. 13A to 13D  is obtained except a shape of the opening H 6  of the first covering layer  12 . 
     The surface-emitting light source  100  obtained through such steps in the manufacturing method can have high reliability of connection as with the surface-emitting light source described above. 
       FIGS. 15A to 15E  are schematic plan views each illustrating a variation of a supplied state of an electrically-conductive member shown in  FIG. 4  and  FIGS. 9A to 9D , respectively.  FIG. 15F  is a schematic plan view illustrating a variation of the opening of the covering layer and a supplied state of the electrically-conductive member.  FIG. 16A  is a schematic cross-sectional view taken along a line XVIA-XVIA of  FIG. 15A .  FIG. 16B  is a schematic cross-sectional view taken along a line XVIB-XVIB of  FIG. 15A . 
     As shown in  FIGS. 15A to 15F  and  FIGS. 16A to 16B , the electrically-conductive member  13  may be supplied into the vias  16  in the wiring pad  18  such that the electrically-conductive member  13  includes the electrically-conductive members  13 A and  13 B supplied separately into respective single vias  16 . The electrically-conductive members  13 A and  13 B are made of the same material as that of the electrically-conductive member  13  described above. Configurations that are the same as those described above are denoted by the same reference numeral, and its detailed description will be omitted. 
     A surface-emitting light source  100  according to these variations includes a wiring substrate  20 , a plurality of light-emitting modules  10 , and an adhesive layer  30  disposed between the wiring substrate  20  and a plurality of light-emitting modules  10 , the wiring substrate  20  including a base member  11 , a wiring layer (a first wiring layer)  17  disposed on a rear surface of the base member  11  opposite to the surface at a light-emitting modules  10  side, electrically-conductive members  13  each supplied into a corresponding one of vias  16  each formed in a corresponding one of wiring pads  18  that are portions of the wiring layer  17 , a covering layer (a first covering layer)  12  covering the wiring layer  17  and defining openings H in each of which a portion of a corresponding wiring pad  18  is exposed. Each of the light-emitting modules  10  has an array of a plurality of light emitting devices  1 . The first covering layer  12  defines openings H at locations corresponding to the wiring pads  18  with an area dimension smaller than respective area dimensions of the wiring pads  18  in a plan view. 
     For example, as shown in  FIG. 15A , when two vias  16  are formed in the wiring pad  18  as described referring mainly to  FIG. 4  and a single opening H is formed with an area dimension smaller than the area dimension of the corresponding wiring pad  18  in a plan view, the electrically-conductive members  13 A and  13 B may be formed to be supplied into respective ones of vias  16 . 
     The electrically-conductive members  13 A and  13 B inside the opening H have a height smaller than a height of the first covering layer  12 . The electrically-conductive members  13 A and  13 B are disposed to extend to portions around the vias  16  in the direction (the lateral direction in  FIG. 15A ) different from the direction of a straight line along which two vias  16  are arrayed such that the electrically-conductive members  13 A and  13 B are in contact with portions of the front surface of the wiring pad  18 . Supplying the electrically-conductive members  13 A and  13 B separately into the plurality of vias  16  can be performed using, for example, screen printing through a mask. 
     As shown in  FIG. 15B , in the configuration in  FIG. 9A  described above, the electrically-conductive members  13  may be supplied into respective ones of the vias  16  in respective ones of a first rectangular opening H 11  and a second rectangular opening H 12  to be separate from each other. In each electrically-conductive member  13 , a portion of the first covering layer  12  between the first rectangular opening H 11  and the second rectangular opening H 12  forms a step, and each of the first rectangular openings H 11  and H 12  is formed for a respective one of vias  16 , which facilitates demarcation. 
     Further, as shown in  FIG. 15C , in the configuration in  FIG. 9B  described above, the electrically-conductive members  13  may be supplied into respective vias  16  formed across a first rectangular opening H 21  and a second rectangular opening H 22  to be separate from each other. In the electrically-conductive member  13 , a portion of the first covering layer  12  between the first rectangular opening H 21  and the second rectangular opening H 22  forms a step, which facilitates demarcation. 
     As shown in  FIG. 15D , in the configuration in  FIG. 9C , the electrically-conductive members  13  may be supplied into a respective vias  16 , each formed across corresponding ones of a first rectangular opening H 31 , a second rectangular opening H 32 , a third rectangular opening H 33 , and a fourth rectangular opening H 34 . In the example herein, one of the electrically-conductive members  13  is supplied to a single via  16  across the first rectangular opening  31  and the second rectangular opening  32 . The other of the electrically-conductive members  13  is supplied to another single via  16  across the third rectangular opening H 33  and the fourth rectangular opening H 34 . 
     As shown in  FIG. 15E , in the configuration in  FIG. 9D , the electrically-conductive members  13  may be supplied into one of the vias  16  and the other of the vias  16  inside the opening H 4  to be separate from each other. 
     The electrically-conductive members  13 A and  13 B shown in  FIG. 15A  have a cross-sectional shape of, as shown in  FIG. 16B , a curved convex shape toward a side opposite to a side at which the light-emitting module  10  is disposed such that portions of the electrically-conductive members  13 A and  13 B exposed from the wiring pad  18  is disposed at intervals in a direction of a straight line along which the vias  16  are arrayed (the vertical direction in  FIG. 15A ). In the direction orthogonal to the direction of a straight line along which the vias  16  are arrayed (the lateral direction in  FIG. 15A ), a portion of the electrically-conductive members  13 A and  13 B exposed from the wiring pad  18  and including a portion in contact with the wiring pad  18  around the via  16  have a cross-sectional shape of a elliptic sector shape with a portion in contact with a pad electrode in the via  16  being pressed, as shown in  FIG. 16A . 
     Cross-sectional shapes of each of configurations shown in  FIGS. 15B to 15E  are almost the same as the cross-sectional shapes in  FIGS. 16A and 16B  of a configuration shown in  FIG. 15A . 
     Further, as shown in  FIG. 15F , an opening H 7  formed in the first covering layer  12  includes a first rectangular opening H 71 , a second rectangular opening H 72 , and a third rectangular opening H 73 . The openings H 7  corresponding to each wiring pad  18  have a total area dimension that is smaller than the area dimension of the wiring pad  18  in a plan view. The first rectangular opening H 71 , the second rectangular opening H 72 , and the third rectangular opening H 73  are aligned along a line. The second rectangular opening H 72  disposed at the center of the first to three rectangular openings H 71  to H 73  has a larger area dimension than the area dimension of the first rectangular opening H 71  or the third rectangular opening H 73  disposed upward or downward in  FIG. 15F . The vias  16  are formed such that one of the vias  16  (a first via  16 ) is formed across the first rectangular opening H 71  and the second rectangular opening H 72 , and the other of the vias  16  (a second via  16 ) is formed across the second rectangular opening H 72  and the third rectangular opening H 73 . 
     The electrically-conductive member  13 A is supplied to one via  16  (the first via  16 ) such that the electrically-conductive member  13 A is filled in the vias  16  and further extends across the second rectangular opening H 72  and the third rectangular opening H 73 . The electrically-conductive member  13 B is supplied into the other via  16  (the second via  16 ) such that the electrically-conductive member  13 B is filled in the vias  16  and further extends across the first rectangular opening H 71  and the second rectangular opening H 72 . The electrically-conductive member  13 A and the electrically-conductive member  13 B are disposed with a gap between each other in the second rectangular opening H 72 . As described above, along a direction in which the first rectangular opening H 71  to the third rectangular opening H 73  are arrayed along a single line (the vertical direction in  FIG. 15F ), an upper portion of each of the electrically-conductive members  13 A and  13 B that is exposed outward has a shape elongated along the vertical direction in  FIG. 15F . For example, moving the squeegee in the vertical direction of  FIG. 15F  through the mask for screen printing when the electrically-conductive material  13  is supplied into the vias  16  allows for forming the electrically-conductive members  13 A and  13 B. 
     The electrically-conductive members  13 A and  13 B shown in  FIG. 15F  have substantially the same shapes as the electrically-conductive members  13 A and  13 B, respectively, shown in  FIG. 15A  except that the cross-sectional shape of a portion exposed from the wiring pad  18  differs in orientation. 
     In configurations shown in  FIGS. 15A to 15F , electrical connection is secured at a contact portion between the wiring pad  18  and the electrically-conductive members  13 A and  13 B. Accordingly, in the case in which the first covering layer  12  overlaps an opening periphery of the via  16 , the overlapping ratio of the first covering layer  12  to the opening periphery of the via  16  is preferably 30% or less of the total opening periphery of the via  16 . As long as the wiring pad  18  and the electrically-conductive member  13  are electrically connected through a contact portion, the electrically-conductive member  13  may have any appropriate plan view shape. 
     As described above, in the surface-emitting light source  100  and the method of manufacturing the same, the first covering layer  12  defines the openings H and H 1  to H 7  on or above the wiring pads  18 . This configuration allows for greatly reducing portions to which pressure applied in the pressing is less easily transmitted, so that insufficient adhesion can be avoided. Also, in the manufacturing method, pressure is applied inside the openings H and H 1  to H 7  using the sheet Pc 1  or the protrusion Dp of the metal mold. This allows for removing an excessive binder resin contained in the electrically-conductive member  13 , so that via resistance can be reduced. 
     While the openings H and H 1  to H 7  in the description above have mainly a rectangular shape, the openings H and H 1  to H 7  may have another shape such as a round hole opening. Any appropriate number and any appropriate shape of vias  16  may be formed in the wiring pad  18 . 
     In the surface-emitting light source  100 , the wiring substrate  20  including the first wiring layer  17  and the first covering layer  12  that are on only the rear surface of the base member  11  as shown in  FIG. 10  described above may be used. 
     In the surface-emitting light source and the method of manufacturing the surface-emitting light source, the first covering layer  12  may be formed at the time of either the step shown in  FIG. 7  or the step shown in  FIG. 12 . The openings defined in the first covering layer  12  corresponding to the wiring pads may have any appropriate shape and size, as long as the opening in the first covering layer  12  has an area dimension that is smaller than the area dimension of the wiring pad in a plan view and overlaps at least a portion of the via. 
     That is, various modifications of the surface-emitting light source may be made within the scope of the claims. Also, the method of manufacturing a surface light source device may include another step between the steps described above or before or after the steps described above. 
     While certain embodiments of the surface-emitting light source and the method of manufacturing a surface light source device have been described above, the present invention is not limited the description above, and should be broadly construed on the basis of the claims. The present invention also encompasses variations and modifications that are made on the basis of the description above.