Patent Publication Number: US-2013250576-A1

Title: Wiring board device, luminaire and manufacturing method of the wiring board device

Description:
INCORPORATION BY REFERENCE 
     The present invention claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2012-068332 filed on Mar. 23, 2012. The content of the application is incorporated herein by reference in their entirety. 
     FIELD 
     Embodiments described herein relate generally to a wiring board device including a wiring pattern, a luminaire and a manufacturing method of the wiring board device. 
     BACKGROUND 
     Hitherto, for example, in an LED module used in a luminaire, a wiring board device in which a wiring pattern is formed on one surface of a board is used. An LED element is electrically connected to the wiring pattern of the wiring board device. Lighting power from a lighting device is supplied to the LED element through the wiring pattern, and the LED element is turned on. 
     Besides, in the LED module, the output thereof is increased, and the board is required to have high heat resistance and high heat radiation property as the output increases. In order to satisfy this request, a ceramic board is often used. Also in the ceramic board, similarly to a general printed wiring board, a wiring pattern is generally formed on one surface of the ceramic board by printing. 
     In order to increase the output of the LED module, a large current is made to flow to the LED element through the wiring pattern, and the amount of heat generated in the LED element is increased since the large current is made to flow. Accordingly, a high heat radiation property is required to be secured. 
     However, in the related art wiring board device, although the ceramic board is used, since the wiring pattern on the ceramic board is formed by printing, it is difficult to cause a large current to flow through the wiring pattern. This is because, since the thickness of the wiring pattern formed by printing is thin and the cross section through which current flows is small, when a large current is made to flow through the wiring pattern, the wiring pattern is melted by Joule heat and is broken. Besides, although the width of the wiring pattern is widened and the cross section through which current flows can be increased, unless the width of the wiring pattern is widened very widely, the wiring pattern can not resist a large current. Thus, the ceramic board must be made large. 
     Further, even if a large current can be made to flow through the wiring pattern, since the amount of heat generation of the LED element increases, a required heat radiation property can not be obtained, and consequently, it becomes difficult to cause a large current to flow through the LED element. 
     As stated above, it is required that the wiring board device can allow a large current to flow through the wiring pattern in a limited size of the ceramic board, and can secure a high heat radiation property. 
     Exemplary embodiments described herein provide a wiring board device, a luminaire and a manufacturing method of the wiring board device, in which a large current can be made to flow through a wiring pattern in a limited size of a ceramic board, and a high heat radiation property can be secured. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a wiring board device of an embodiment. 
         FIG. 2  is an enlarged sectional view of a part of the wiring board device. 
         FIG. 3  is an explanatory view of a first copper plated layer (wiring pattern) of the wiring board device. 
         FIG. 4  is a front view of the wiring board device. 
         FIGS. 5(   a ) to  5 ( f ) are sectional views showing a manufacturing method of the wiring board device. 
         FIGS. 6(   a ) and  6 ( b ) show wiring patterns according to different manufacturing methods, in which  FIG. 6(   a ) is a sectional view of a wiring pattern formed by copper plating, and  FIG. 6(   b ) is a sectional view of a wiring pattern formed by etching. 
         FIG. 7  is a perspective view of a luminaire using the wiring board device. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, a wiring board device includes a ceramic board including a first surface and a second surface. A first electrode layer is formed on the first surface of the ceramic board, and a second electrode layer is formed on the second surface of the ceramic board. The first electrode layer and the second electrode layer are not electrically connected to each other. A first copper plated layer as a wiring pattern is formed on the first electrode layer, and a second copper plated layer is formed on the second electrode layer. The first copper plated layer and the second copper plated layer are not electrically connected to each other. A heat spreader is thermally connected to the second copper plated layer. 
     According to this structure, since the wiring pattern is formed of the first copper plated layer on the first surface side of the ceramic board, the thickness of the wiring pattern can be easily increased. Further, the second copper plated layer is formed on the second surface side of the ceramic board, and the heat spreader is thermally connected to the second copper plated layer. Accordingly, heat is efficiently conduced from the ceramic board to the heat spreader and can be radiated. Accordingly, a large current can be made to flow through the wiring pattern in the limited size of the ceramic board, and a high heat radiation property can be secured. 
     Hereinafter, embodiments will be described with reference to  FIG. 1  to  FIG. 7 . 
       FIG. 7  shows a luminaire  10 . The luminaire  10  is, for example, a floodlight used for lighting-up. The luminaire  10  includes an equipment main body  11 , and a floodlight window is provided in the equipment main body  11 . Plural light-emitting modules  13  facing the floodlight window  12  are housed in the equipment main body  11 . A lighting device  14  to supply lighting power to the light-emitting modules  13  is housed at a lower part in the equipment main body  11 . The lighting device  14  supplies the lighting power to the plural light-emitting modules  13 , so that the plural light-emitting modules  13  are turned on, and light is emitted from the floodlight window  12 . 
       FIG. 1  to  FIG. 4  show the light-emitting module  13 . The light-emitting module  13  includes a wiring board device  20 . 
     The wiring board device  20  includes a square ceramic board  21 . A front side of the ceramic board  21  is a first surface  21   a,  and a back side thereof is a second surface  21   b . A first electrode layer  22   a  is formed on the first surface  21   a , and a first copper plated layer  23   a  is formed on the first electrode layer  22   a.  A wiring pattern  24  having a specific shape is formed of the first electrode layer  22   a  and the first copper plated layer  23   a.  On the other hand, a second electrode layer  22   b  is formed on substantially the whole area of the second surface  21   b,  and a second copper plated layer  23   b  is formed on the second electrode layer  22   b.  Further, metal plated layers  25  to protect the copper plated layers  23   a  and  23   b  are formed on the surfaces of the copper plated layers  23   a  and  23   b.    
     The electrode layers  22   a  and  22   b  are formed by sputtering of a metal such as titanium. The copper plated layers  23   a  and  23   b  are formed by copper plating, and the metal plated layers are formed of, for example, nickel/gold plating or nickel/lead/gold plating. A DPC (Direct Plated Copper) board  26  is formed of the ceramic board  21 , the electrode layers  22   a  and  22   b,  the copper plated layers  23   a  and  23   b,  and the metal plated layers  25 . 
     The first electrode layer  22   a  and the second electrode layer  22   b  are formed to have the same thickness, and the first copper plated layer  23   a  and the second copper plated layer  23   b  are formed to have the same thickness. As shown in  FIG. 3 , the thickness A of the first electrode layer  22   a  is about 1 μm, the minimum width B of the first copper plated layer  23   a  (the wiring pattern  24  through which current flows) is 50 to 75  82  m, and the thickness C thereof is 35 to 100 μm (preferably, 50 to 75 μm). Incidentally, if the wiring pattern is formed by printing, the thickness of the wiring pattern is at most about 10 μm. 
     As shown in  FIG. 4 , the wiring pattern  24  includes a pair of electrode parts  27  to receive lighting power from the outside, and plural wiring parts  28  are formed in parallel between the pair of electrode parts  27 . Plural LED elements  29  are mounted on the adjacent wiring parts  28 . 
     As shown in  FIG. 1 , the plural LED elements  29  are of a type, such as a flip chip type, in which a pair of electrodes are provided on the back side. The pairs of electrodes of the plural LED elements  29  are electrically connected to the first copper plated layer  23   a  by solder die bond layers  30 . Incidentally, the LED element may be such that an electrode is provided on the front surface side as in a face-up type, and the electrode of the LED element and the wiring pattern  24  are connected by wire bonding. 
     As shown in  FIG. 2 , an organic resist layer  31  is formed on the first surface  21   a  side including the first copper plated layer  23   a,  and the organic resist layer is spaced from the plural LED elements  29  by a first distance L 1 . An inorganic resist ink layer  32  is formed on the organic resist layer  31 , and the inorganic resist ink layer is spaced from an end of the organic resist layer  31  facing the plural LED elements  29  by a second distance L 2 . The surfaces of the organic resist layer  31  and the inorganic resist ink layer  32  are formed as a reflecting surface  33  to reflect light emitted from the plural LED elements  29 . 
     Although the organic resist layer  31  contains epoxy resin as a main component and is white, there is a tendency that the color is liable to change. The inorganic resist ink layer  32  contains ceramic as a main component and is white, and has a characteristic that the color is hard to change. However, since the particle diameter of the ceramic is large, there is a tendency that light is liable to pass through. Thus, a two-layer structure is adopted in which the inorganic resist ink layer  32  is formed on the organic resist layer  31 , so that high reflection efficiency can be continuously maintained. 
     Although the organic resist layer  31  can be patterned and formed by using a photoresist, the inorganic resist ink layer  32  is patterned and formed by printing. The patterning size accuracy of the inorganic resist ink layer  32  patterned and formed by printing is low, and the distance between itself and the LED element  29  is not stable. Thus, the second distance L 2  is increased in view of the size accuracy. When the second distance L 2  is large, an area which does not contribute to light reflection becomes large, and reflection efficiency is reduced. Then, the organic resist layer  31  with high patterning accuracy is formed to be close to the LED element  29 , so that high reflection efficiency can be obtained. The first distance L 1  is 25 to 200 μm, the second distance L 2  is 50 to 200 μm, and the relation of the first distance L 1 ≦the second distance L 2  is established. 
     Besides, an annular reflecting frame  34  is formed on the first surface  21   a  side so as to surround a mount area of the plural LED elements  29 . A sealing resin  35  to seal the plural LED elements  29  is filled inside the reflecting frame  34 . The sealing resin  35  contains a phosphor which is excited by the light generated by the plural LED elements  29 . For example, if the light-emitting module  13  emits white light, the LED element  29  emitting blue light and the phosphor mainly emitting yellow light are used. The blue light generated by the LED element  29  is mixed with the yellow light generated by the phosphor which is excited by the blue light generated by the 
     LED element  29 , and the white light is emitted from the surface of the sealing resin  35 . Incidentally, the LED element  29  and the phosphor, which emit lights of colors corresponding to the color of irradiated light, are used. 
     Besides, a heat spreader  37  is fixed to the second copper plated layer  23   b  through a solder layer  38  and is thermally connected thereto. The heat spreader  37  includes a copper plate  39  having a thickness of 0.1 to 3 mm, and a metal plated layer  40  such as a nickel plated layer is formed on the whole surface of the copperplate  39 . Attachment holes  41  for fixing to a heat radiation part of the luminaire  10  using screws are formed at four corners of the heat spreader  37 . 
     Next, a manufacturing method of the DPC board  26  of the wiring board device  20  will be described with reference to  FIGS. 5(   a ) to  5 ( f ). 
     As shown in  FIG. 5(   a ), a metal such as titanium is sputtered on the whole surface of the ceramic board  21 , and an electrode layer  22  including the first electrode layer  22   a  and the second electrode layer  22   b  is formed. 
     As shown in  FIG. 5(   b ), a resist  51  is patterned and formed on the electrode layer  22 . 
     As shown in  FIG. 5(   c ), the ceramic board  21  is immersed in a copper plating solution of a plating apparatus, and electrical power is applied to the electrode layer  22 , so that electrolytic plating is performed on the electrode layer  22  exposed from the resist  51 , and the first copper plated layer  23   a  and the second copper plated layer  23   b  having a specific thickness are simultaneously formed. At this time, since the first copper plated layer  23   a  and the second copper plated layer  23   b  are simultaneously formed, the first copper plated layer  23   a  and the second copper plated layer  23   b  have the same thickness. After the electrolytic plating is completed, the ceramic board  21  is taken out from the plating apparatus. 
     As shown in  FIG. 5(   d ), only the resist  51  is removed from the ceramic board  21  by etching. 
     As shown in  FIG. 5(   e ), the metal plated layer  25  is formed on the surfaces of the copper plated layers  23   a  and  23   b.  That is, the ceramic board  21  is immersed in a metal plating solution of the plating apparatus, and electrical power is applied to the electrode layer  22 , so that electrolytic plating is performed on the copper plated layers  23   a  and  23   b  and the electrode layer  22 , and the metal plated layer  25  is formed. After the electrolytic plating is completed, the ceramic board  21  is taken out from the plating apparatus. 
     As shown in  FIG. 5(   f ), a portion of the electrode layer  22  in which the copper plated layers  23   a  and  23   b  are not laminated is removed from the ceramic board  21  by etching. 
     In this way, the DPC board  26  of the wiring board device  20  is manufactured. 
     Besides, when the light-emitting module  13  is manufactured by using the DPC board  26  of the wiring board device  20 , as shown in  FIG. 1  and  FIG. 2 , the organic resist layer  31  is patterned and formed on the first surface  21   a  side including the first copper plated layer  23   a  by using a photoresist. Further, the inorganic resist ink layer  32  is patterned and formed on the organic resist layer  31  by printing. 
     The plural LED elements  29  are electrically connected to the wiring pattern  24  (the first copper plated layer  23   a ) by the solder die bond layer  30 . 
     The annular reflecting frame  34  is provided so as to surround the mount area of the plural LED elements  29 , and the sealing resin  35  to seal the plural LED elements  29  is filled inside the reflecting frame  34 . 
     Besides, the heat spreader  37  is fixed to the second copper plated layer  23   b  by the solder layer  38  and is thermally connected thereto. 
     In this way, the light-emitting module  13  is manufactured. 
     Besides, as shown in  FIG. 7 , the plural light-emitting modules  13  are disposed in the equipment main body  11 . In this case, screws are threaded into the attachment holes  41  of the heat spreader  37  to fix the heat spreader to the heat radiation part of the equipment main body  11 , and the heat spreader  37  is thermally connected to the heat radiation part of the equipment main body  11 . Besides, the pair of electrode parts  27  of the wiring pattern  24  are electrically connected to the lighting device  14  by electric wires. 
     The lighting device  14  supplies lighting power to the plural light-emitting modules  13 , so that the lighting power flows through the plural LED elements  29  through the wiring patterns  24  of the respective light-emitting modules  13 . Thus, the plural light-emitting modules  13  are turned on, and the lights from the plural light-emitting modules  13  are emitted from the floodlight window  12 . 
     The heat generated in the plural LED elements  29  at the time of lighting of the light-emitting modules  13  is efficiently conducted to the first copper plated layer  23   a , the ceramic board  21 , the second copper plated layer  23   b  and the heat spreader  37 . Further, the heat is efficiently conducted from the heat spreader  37  to the heat radiation part of the equipment main body  11 , and is radiated from the heat radiation part of the equipment main body  11 . 
     In this embodiment, since the wiring pattern  24  is formed of the copper plated layer  23   a  on the first surface  21   a  side of the ceramic board  21 , the thickness of the wiring pattern  24  can be easily increased. Thus, a large current can be made to flow through the wiring pattern  24 , and high output of the light-emitting module  13  can be ensured. 
     Further, since the second copper plated layer  23   b  is formed on the second surface  21   b  side of the ceramic board  21 , the high heat radiation property from the second copper plated layer  23   b  can be obtained. 
     Accordingly, a large current can be made to flow through the wiring pattern  24  in the limited size of the ceramic board  21 , and the high heat radiation property can be secured. 
     Besides, the first copper plated layer  23   a  and the second copper plated layer  23   b  have the same thickness. That is, the first copper plated layer  23   a  and the second copper plated layer  23   b  can be simultaneously formed at the time of plating, and the manufacturing efficiency can be improved. 
     Besides, since the first electrode layer  22   a  and the first copper plated layer  23   a  are not electrically connected to the second electrode layer  22   b  and the second copper plated layer  23   b,  the reliability can be secured. 
     Besides, since the minimum width of the first copper plated layer  23   a  (the wiring pattern  24  through which current flows) is 50 to 75 μm, and the thickness is 35 to 100 μm, a large current can be made to flow without increasing the width. Incidentally, the thickness of the first copper plated layer  23   a  is preferably 50 μm or more from the viewpoint that a large current is made to flow and is 75 μm or less from the viewpoint of manufacturing efficiency. That is, the more preferable thickness range of the first copper plated layer  23   a  is 50 to 75 μm. 
     Besides, a current of 1 to 8 amperes flows through the first copper plated layer  23   a,  and even if a current is large as a current flowing through the wiring pattern  24 , the large current can be allowed to flow through the first copper plated layer  23   a.    
     Besides, further merits obtained when the wiring pattern  24  is formed by copper plating will be described with reference to  FIGS. 6(   a ) and  6 ( b ).  FIG. 6(   a ) shows the embodiment in which the wiring pattern  24  is formed by copper plating, and  FIG. 6(   b ) shows a comparative example in which the wiring pattern  24  is formed by etching. In both cases, the width of the wiring pattern  24  is B, and the interval between the adjacent wiring patterns  24  is D. 
     As shown in  FIG. 6(   b ), in the comparative example in which the wiring pattern  24  is formed by etching, since inclined portions are formed on both sides of the wiring pattern  24 , the pitch of the wiring pattern  24  becomes wide by width E of the inclined portion on both sides, and the size becomes large. 
     On the other hand, as shown in  FIG. 6(   a ), in the embodiment in which the wiring pattern  24  is formed by copper plating, since the resist  51  for patterning the wiring pattern  24  (the first copper plated layer  23   a ) can be removed by etching, an inclined portion is not formed on the side of the wiring pattern  24 , the pitch of the wiring pattern  24  can be shortened, and the size can be reduced. 
     Besides, since the heat spreader  37  is thermally connected to the second copper plated layer  23   b,  heat is efficiently conducted from the ceramic board  21  to the heat spreader  37  and can be radiated, and high output of the light-emitting module  13  can be ensured. 
     Further, since the second copper plated layer  23   b  and the heat spreader  37  are soldered to each other, heat conductivity from the second copper plated layer  23   b  to the heat spreader  37  can be improved. 
     Besides, the plural LED elements  29  are electrically connected to the first copper plated layer  23   a  of the wiring board device  20 , so that the light-emitting module  13  capable of ensuring high output can be provided. 
     Besides, since the organic resist layer  31  is formed on the first copper plated layer  23   a  and the inorganic resist ink layer  32  is formed on the organic resist layer  31 , high reflection efficiency can be continuously maintained. That is, although the organic resist layer  31  contains epoxy resin as a main component and is white, there is a tendency that the color is liable to change. On the other hand, the inorganic resist ink layer  32  contains ceramic as a main component and is white, and has a characteristic that the color is hard to change. However, since the particle diameter of the ceramic is large, there is a tendency that light is liable to pass through. Thus, the two-layer structure is adopted in which the inorganic resist ink layer  32  is formed on the organic resist layer  31 , so that high reflection efficiency can be continuously maintained. 
     Besides, the organic resist layer  31  is formed to be spaced from the LED element  29  by the first distance L 1 , the inorganic resist ink layer  32  is formed to be spaced from the end of the organic resist layer  31  facing the LED element  29  by the second distance L 2 , and the relation of the first distance L 1 ≦second distance L 2  is established. Thus, high reflection efficiency can be obtained. That is, although the organic resist layer  31  can be patterned and formed by using a photoresist, the inorganic resist ink layer  32  is patterned and formed by printing. The patterning accuracy of the inorganic resist ink layer  32  patterned and formed by printing is low, and the distance between itself and the LED element  29  is not stable. Thus, the second distance L 2  is preferably increased in view of the accuracy. When the second distance L 2  is large, an area which does not contribute to the light reflection becomes large, and reflection efficiency is reduced. Then, the organic resist layer  31  with high patterning accuracy is formed to be close to the LED element  29 , so that high reflection efficiency can be obtained. The first distance L 1  is 25 to 200 μm, the second distance L 2  is 50 to 200 μm, and the respective distances L 1  and L 2  can be suitably set according to the foregoing condition. 
     Besides, since the metal plated layer  25  is formed on the first copper plated layer  23   a  between the LED element  29  and the organic resist layer  31 , the first copper plated layer  23   a  is prevented from being corroded and can be protected. 
     Incidentally, the wiring board device  20  is not limited to the wiring board device for mounting the LED elements  29 , and the wiring board device  20  can also be applied to a wiring board device for mounting an integrated circuit, or a wiring board device for mounting electrical parts of a power supply device. 
     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.