JP2018207083A - Printed wiring board and manufacturing method therefor - Google Patents

Abstract

To improve heat radiation characteristics of a printed wiring board.SOLUTION: A printed wiring board 1 according to one embodiment includes an insulating layer having a first surface 10B and a second surface 10F opposite to the first surface 10B, a second conductor layer 21 laminated at a second surface 10F side of the insulating layer, and a first conductor layer 11 laminated at a first surface 10B side of the insulating layer, which is thicker than the second conductor layer 21. The first conductor layer 11 includes a radiation fin 11f.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a printed wiring board and a manufacturing method thereof.

  Patent Document 1 describes a printed wiring board with a radiation fin in which a base surface of a radiation fin made of a metal material is attached to the lower surface of an insulating layer that supports a conductor metal part on the upper surface.

JP-A-8-204294

  In the printed wiring board of Patent Document 1, the heat of the mounted electronic component is released from the heat radiating fins through the conductor metal part and the insulating layer, so that the heat radiating effect may not be sufficient. In addition, it is considered that the radiating fin may be peeled off from the insulating layer.

  The printed wiring board of the present invention includes an insulating layer having a first surface and a second surface opposite to the first surface, a second conductor layer laminated on the second surface side of the insulating layer, and the insulation A first conductor layer that is laminated on the first surface side of the layer and is thicker than the second conductor layer. The first conductor layer includes heat radiating fins.

  The method for manufacturing a printed wiring board according to the present invention includes preparing an insulating layer having a metal foil on each of a first surface and a second surface opposite to the first surface, and a conduction hole penetrating the insulating layer. Forming a first conductor layer including a radiation fin on the first surface of the insulating layer, and forming a second conductor layer on the second surface of the insulating layer.

  According to the embodiment of the present invention, it is considered that the heat generated in the mounted electronic component is efficiently radiated from the radiation fin. Moreover, according to the embodiment of the present invention, it is not necessary to previously form the heat radiating fins in accordance with the printed wiring board. It is considered that the degree of freedom of arrangement of the radiation fins with respect to the printed wiring board is also high.

Sectional drawing of the printed wiring board of one Embodiment of this invention. The top view which shows an example of one surface of the printed wiring board of one Embodiment of this invention. The top view which shows the other example of one surface of the printed wiring board of one Embodiment of this invention. The enlarged view which shows an example of the radiation fin of the printed wiring board of one Embodiment of this invention. The figure which shows an example of the manufacturing method of the printed wiring board of one Embodiment of this invention. The figure which shows an example of the manufacturing method of the printed wiring board of one Embodiment of this invention. The figure which shows an example of the manufacturing method of the printed wiring board of one Embodiment of this invention. The figure which shows an example of the manufacturing method of the printed wiring board of one Embodiment of this invention. The figure which shows an example of the manufacturing method of the printed wiring board of one Embodiment of this invention. The figure which shows an example of the manufacturing method of the printed wiring board of one Embodiment of this invention. The figure which shows an example of the manufacturing method of the printed wiring board of one Embodiment of this invention. The figure which shows an example of the manufacturing method of the printed wiring board of one Embodiment of this invention. The figure which shows an example of the manufacturing method of the printed wiring board of one Embodiment of this invention. The figure which shows an example of the manufacturing method of the printed wiring board of other embodiment of this invention. The figure which shows an example of the manufacturing method of the printed wiring board of other embodiment of this invention. The figure which shows an example of the manufacturing method of the printed wiring board of other embodiment of this invention. The figure which shows an example of the manufacturing method of the printed wiring board of other embodiment of this invention. The figure which shows an example of the manufacturing method of the printed wiring board of other embodiment of this invention. The figure which shows an example of the manufacturing method of the printed wiring board of other embodiment of this invention. The figure which shows an example of the manufacturing method of the printed wiring board of other embodiment of this invention. The figure which shows an example of the manufacturing method of the printed wiring board of other embodiment of this invention. The figure which shows the other example of the manufacturing method of the printed wiring board of other embodiment of this invention. The figure which shows the other example of the manufacturing method of the printed wiring board of other embodiment of this invention. The figure which shows the other example of the manufacturing method of the printed wiring board of other embodiment of this invention. The figure which shows the other example of the manufacturing method of the printed wiring board of other embodiment of this invention. The figure which shows the other example of the manufacturing method of the printed wiring board of other embodiment of this invention. The figure which shows the other example of the manufacturing method of the printed wiring board of other embodiment of this invention. The figure which shows the other example of the manufacturing method of the printed wiring board of other embodiment of this invention. The figure which shows the other example of the manufacturing method of the printed wiring board of other embodiment of this invention. The figure which shows the other example of the manufacturing method of the printed wiring board of other embodiment of this invention. Sectional drawing of an example of the printed wiring board manufactured by the manufacturing method of the printed wiring board of further another embodiment of this invention.

  A printed wiring board 1 according to an embodiment of the present invention will be described with reference to the drawings. 1, 2A and 2B respectively show a cross-sectional view and a plan view of an example of the printed wiring board 1 of the embodiment. FIG. 1 is a cross-sectional view at the position indicated by line I-I in FIGS. 2A and 2B. The printed wiring board 1 includes a first insulating layer 10, a first surface 10B that is one surface of the first insulating layer 10, and a first conductor layer 11 that is stacked on a second surface 10F opposite to the first surface 10B, and And a second conductor layer 21. The first conductor layer 11 is formed thicker than the second conductor layer 21. The thick first conductor layer 11 forms heat radiating fins 11f. It is considered that an excellent heat dissipation effect can be obtained.

  The first conductor layer 11 protrudes downward in FIG. 1 from the base portion 11b serving as a base portion with respect to the heat radiating fin 11f and the surface of the base portion 11b opposite to the first insulating layer 10, and is adjacent to each other. Radiating fins 11f composed of the fins. As shown in FIG. 1, in the printed wiring board 1 according to an embodiment, the first conductor layer 11 includes a first metal foil 12 formed on the first surface 10 </ b> B of the first insulating layer 10, and a first metal layer 12. It is formed of a plating film 13 formed on the metal foil 12 and forming the base portion 11b together with the first metal foil 12, and a conductor layer 15 forming the radiation fins 11f. The first metal foil 12 and the plating film 13 are directly joined. The plating film 13 and the conductor layer 15 are directly joined. That is, on the first surface 10B side of the first insulating layer 10, the layers constituting the first conductor layer 11 are joined to each other without an adhesive layer or the like interposed therebetween. According to the present embodiment, an adhesive layer, a bonding material, or the like with low thermal conductivity for attaching the radiation fin to the substrate is not included in the first conductor layer 11. Therefore, according to the present embodiment, the heat generated from the electronic and electrical components mounted on the printed wiring board is conducted to the radiating fin without going through the adhesive layer having a low thermal conductivity, and is released to the outside. . It is considered that a high heat dissipation wiring board can be obtained.

  Furthermore, the same metal material excellent in thermal conductivity may be used for forming the plating film 13 and the conductor layer 15. The base part 11b and the radiation fin 11f can be formed seamlessly. Further, the first metal foil 12 may be formed of the same material as that of the plating film 13 and the conductor layer 15. An example of this is shown in FIG. That is, in the example of FIG. 1, the metal foil, the plating film, and the heat radiation fin that form the first conductor layer are all formed of the same material. The first conductor layer 11 including the radiation fins can be formed seamlessly. It is thought that a wiring board excellent in heat dissipation can be obtained.

  In the present embodiment, the substrate from the electronic component mounting board to the heat radiating fin is formed without interposing different materials such as an adhesive or a resin material at the interface. For this reason, even if stress occurs during the manufacturing process or use of the printed wiring board 1, peeling or breakage occurs at the interface between the first metal foil 12 and the plating film 13 or the interface between the plating film 13 and the conductor layer 15. It seems difficult. Problems such as mounting defects and falling off of the radiation fins that may occur when the radiation fins are attached to the manufactured substrate do not occur. Moreover, it is thought that the thermal stress which arises in each interface part is also small. It is considered that a highly reliable printed wiring board 1 having heat radiation fins can be obtained.

  The 1st metal foil 12, the plating film 13, and the conductor layer 15 of the 1st conductor layer 11 may be formed with copper, for example. However, the materials of the first metal foil 12, the plating film 13, and the conductor layer 15 are not limited to copper, and may be other metals such as nickel. The material of the first metal foil 12, the plating film 13 and the conductor layer 15 may be a metal material having a high thermal conductivity.

  In the printed wiring board 1 of the embodiment, the conductor layer 15 is formed on the plating film 13 by, for example, electrolytic plating as described later. The plating film 13 and the conductor layer 15 can be formed seamlessly. The thickness of the base portion 11b made of the first metal foil 12 and the plating film 13 is, for example, 12 μm or more and 50 μm or less.

  The thickness of the conductor layer 15 is the height H of the radiating fin 11f, that is, the length of the protruding portion of the radiating fin 11f toward the first surface 10B, for example, 80 μm or more and 1000 μm or less. Preferably, the height H of the heat dissipating fins 11f is 200 μm or more and 1000 μm or less. In one embodiment, the radiation fins 11f are formed by electrolytic plating. It is easy to appropriately design and form the thickness, spacing, area, etc. of the radiating fins according to the use conditions. For example, as will be described later, the conductor layer 15 constituting the heat radiation fin 11f can be formed stepwise by a plurality of times of electrolytic plating. Furthermore, fine pitch processing in the formation of the radiation fins is also possible. The radiating fins 11f are preferably formed so that the fin interval S between the fins of the radiating fins 11f is small and the fin height H is large. The surface area of each fin is increased, and the heat radiation area of the heat radiation fin 11f is expanded. The heat radiation fin 11f having high heat radiation performance is obtained. For example, the ratio (tongue ratio) of the height H of the radiation fins 11f to the spacing S between adjacent fins of the radiation fins 11f of the embodiment can be set to 0.4 or more. For example, the interval S between the fins is 100 μm or more and 500 μm or less. The thickness D of each fin of the radiating fin 11f is, for example, 200 μm or more and 500 μm or less. The spacing S between the fins and the thickness D of the fins can be selected so that the heat radiation amount and fin efficiency of the heat radiation fin 11f are optimized.

  The heat radiating fins 11f formed by the conductor layer 15 are formed in, for example, a pin type or a comb type so that each fin protrudes outward on the first surface 10B side of the first insulating layer 10. Examples of pin fins and comb fins are shown in FIGS. 2A and 2B, respectively. Although FIG. 2A shows a pin-type fin in which the planar shape of each fin is circular, the planar shape of the fin is not limited to this, and an arbitrary shape can be selected. For example, the planar shape of the fin may be a triangle, a rectangle or a rhombus, a polygon such as a hexagon, a cross, or an ellipse. FIG. 2A shows an example in which all fins are arranged in a regular lattice shape. However, the pin-type fins may be arranged in a so-called zigzag pattern in which two adjacent patterns are shifted by 1/2 pitch. With such an arrangement, turbulent flow may occur in the heat radiating fins, and the heat radiating effect may be enhanced. In the example shown in FIG. 2A, the thickness D of each fin corresponds to the diameter D1 of the pin-type fin, and the fin diameter D1 is, for example, 200 μm or more and 500 μm or less. The spacing S between the fins is, for example, 100 μm or more and 500 μm or less. For convenience, the term “diameter” is used, which means the maximum value of the distance between two points belonging to the outer periphery of the fin. By using pin-type fins, the surface area of the fins may be increased, and the heat dissipation performance of the heat dissipation fins may be further enhanced.

  FIG. 2B is an example of a comb fin in which a plurality of blade fins arranged in parallel at equal intervals in the left-right direction in FIG. 2B are formed by the conductor layer 15. In the example of FIG. 2B, comb-shaped fins made of straight blades are shown. In the case of such a fin, the thickness D of each fin corresponds to the thickness D2 of the blade fin, and the thickness D2 of the blade fin is, for example, 200 μm or more and 500 μm or less. The spacing S between the blade fins is, for example, 100 μm or more and 500 μm or less. By adopting the shape of a comb fin instead of the pin fin, a straight flow path may be formed in the heat radiating fin and high heat radiating performance may be obtained. In addition, a waving fin that undulates the fin, or an offset fin that is arranged by dividing the fin in the longitudinal direction and adding an offset in the lateral direction may be formed. Heat dissipation performance may be improved.

  As described above, the conductor layer 15 that forms the heat radiating fins 11f is, for example, a plating film formed by electrolytic plating. Therefore, the radiation fin of the embodiment can be manufactured by using a circuit forming process of a normal wiring board. Further, it is considered that it is easy to form a thin and narrow pitch blade fin, an ultra-fine pin type fin, or the like.

  FIG. 3 shows an enlarged cross-sectional view of an example of a fin having a height H of, for example, 80 μm or more. In this example, the conductor layer 15 forming the pin-type fin is formed by three times of electrolytic plating. High-fins that cannot be formed by a single electrolytic plating can be formed. In the example shown in FIG. 3, electrolytic plating is performed so that the diameter of the pin-type fin becomes smaller for each electrolytic plating. For this reason, the pin-type fin has a shape that tapers in steps toward the tip. That is, the diameter D3 of the end surface of the pin-type fin opposite to the plating film 13 is smaller than the diameter D1 on the plating film 13 side. Each portion formed by one-time electroplating of the pin-type fin has a side surface substantially perpendicular to the plating film 13. Thus, even if the pin-type fin is formed by a plurality of times of electrolytic plating, since the respective plating layers are directly bonded to each other, even if stress is applied to the radiating fins 11f, Problems such as cracks are unlikely to occur. Furthermore, in this embodiment, since the fin of a thin diameter is formed by plating on the fin which has a thicker diameter, it is thought that the alignment for performing plating is easy. In addition, since the pin-type fin has a tapered shape, air movement between the fins in the vicinity of the fin tip may be facilitated even in a heat radiating fin having a small fin pitch.

  The heat dissipating fins of the printed wiring board according to the embodiment are not limited to the example of FIG. 3, and can be formed into fins having a desired height by repeating a desired number of times of electrolytic plating. Further, the side surfaces of the fins do not need to be formed in a tapered shape like the example shown in FIG. 3, and may be formed to have a certain taper angle, for example. Further, instead of the tapered shape, a fin having a shape in which the diameter D1 of the end surface facing each plating film 13 of each fin is equal to the diameter of the end surface opposite to the plating film 13 is formed by multiple times of electrolytic plating. May be. In addition, the fin formed by such multiple times of electroplating is not limited to a pin-type fin, but may be a blade fin.

  The printed wiring board 1 includes the first insulating layer 10 between the first conductor layer 11 and the second conductor layer 21 as described above. The first insulating layer 10 is not limited to a single layer, and may be an insulating layer having a plurality of layers stacked via a conductor layer. That is, the first insulating layer 10 may be an insulating layer having a stacked body in which one or more insulating layers and conductor layers are alternately stacked. The insulating material to be the first insulating layer 10 may be, for example, an epoxy resin formed in a film shape or a prepreg formed by impregnating a reinforcing material such as glass fiber with an epoxy resin. The thickness of the first insulating layer 11 is, for example, 10 μm or more and 100 μm or less.

  The first insulating layer 10 is formed with a plurality of via conductors that connect the first conductor layer 11 and the second conductor layer 21. Among the plurality of via conductors, the first via conductor 31 can function as a so-called thermal via that thermally connects the first conductor layer 11 and the second conductor layer 21 with high thermal conductivity. . Therefore, it is preferable that the first via conductor 31 has good conductivity at least with respect to heat. On the other hand, since the first via conductor 31 electrically connects the first conductor layer 11 and the second conductor layer 21, respectively, it is preferable that the first via conductor 31 is an electrically good conductor.

  As shown in FIG. 1, a second conductor layer 21 is provided on the second surface 10 </ b> F side of the first insulating layer 10. The second conductor layer 21 is formed with an arbitrary conductor pattern including a land portion for component mounting. The land portion and the first conductor layer 11 are connected by a first via conductor 31 having a thermal via function. An external electronic component E1 is mounted on the land portion by a flip chip method or the like with a bonding material E2 such as solder. That is, in the printed wiring board 1, the second surface 10F side is a component mounting surface. Examples of the electronic component E1 include an active component such as a semiconductor device and a passive component such as a resistor and an inductor.

  In the printed wiring board 1 of the embodiment, the heat generated by the electronic component spreads outward at the land portion and is dissipated by radiation from the surface, and efficiently the first conductor layer 11 via the first via conductor 31. Heat is dissipated by conduction. Since the printed wiring board 1 includes the heat dissipating fins 11f that are excellent in heat dissipation as the first conductor layer 11 in the outer layer on the first surface 10B side of the first insulating layer 10, the first wiring layer 1 has the first via the first via conductor 31. The heat conducted to the conductor layer 11 is efficiently radiated from the radiation fins 11f. Therefore, the printed wiring board 1 is considered to be particularly suitable when an electronic component that generates heat during operation, for example, a power semiconductor, a power resistor, and a light emitting diode are mounted on the printed wiring board. For example, the printed wiring board 1 can be satisfactorily used as a substrate having improved heat dissipation for LED mounting with a large calorific value. In such a printed wiring board 1, the component mounting land is a light emitting element mounting pad for mounting a light emitting element such as an LED.

  The first via conductor 31 that functions as a thermal via can be formed of a metal having high thermal conductivity such as copper, as will be described later. It is considered that heat can be efficiently conducted from the component mounting land portion on the second surface 10F side of the first insulating layer 10 to the heat radiation fins 11f of the first conductor layer 11 through the first via conductors 31. For example, the first via conductor 31 is formed of a copper plating film.

  As described above, the second conductor layer 21 can include a predetermined conductor pattern in addition to the land portion for component mounting. The second conductor layer 21 is formed of, for example, a metal foil and a plating film. In the example of FIG. 1, the second conductor layer 21 is formed from a metal foil 22 and a plating film 23. The conductor pattern of the second conductor layer 21 can be formed by any method such as a subtractive method or an additive method. Examples of the material of the second conductor layer 21 include copper and nickel. However, the material of the second conductor layer 21 is not limited to these. The thickness of the second conductor layer 21 is, for example, 10 μm or more and 70 μm or less.

  In the example of FIG. 1, the printed wiring board 1 further includes a cover lay 51 formed on the second conductor layer 22. The coverlay 51 has an opening that exposes a component mounting land portion of the second conductor layer 22. The coverlay 51 can function as an insulating protective film. As a material of the coverlay 51, a material having high heat resistance is preferable. Moreover, a cover circuit film for protecting a conductor circuit having a high reflectance in the visible light region may be preferable. Further, by forming the coverlay 51, the migration resistance of the printed wiring board 1 can be improved. By forming the coverlay 51, it is considered that insulation and protection of a conductor circuit in a printed wiring board on which a light emitting element such as one or more LEDs is mounted is preferably performed.

  In the printed wiring board 1 of the embodiment, the heat radiating fins 11f are formed integrally with the first insulating layer 10 and the conductor layer on the second surface 10F side of the first insulating layer 10. And the land part for component mounting of the 2nd conductor layer 21 and the radiation fin 11f of the 1st conductor layer 11 are directly joined to the via conductor which mutually connects. Therefore, it is considered that the heat conduction path can be simplified and the thinning of the semiconductor device can be promoted.

  Next, taking the printed wiring board 1 shown in FIG. 1 as an example, an example of a method for manufacturing a printed wiring board according to an embodiment will be described with reference to FIGS. 4A to 4I are not intended to show the exact ratios of the thicknesses of the components.

As shown in FIG. 4A, a first insulating layer 10 having a first surface 10B and a second surface 10F opposite to the first surface 10B is prepared. Metal foils 12 and 22 are provided on both the first surface 10B and the second surface 10F of the first insulating layer 10, respectively. As the insulating member constituting the first insulating layer 10, for example, an insulating resin such as an epoxy resin is used. Preferably, the insulating member constituting the first insulating layer 10 is a so-called prepreg formed by impregnating a reinforcing material such as glass fiber with an epoxy resin. The material of the first insulating layer 10 may be bismaleimide triazine resin (BT resin), phenol resin, or the like. The material of the first insulating layer 10 may include an inorganic filler such as silica (SiO ₂ ). The first insulating layer 10 is not a single insulating layer as shown in FIG. 4A, but one or more conductor layers and insulating layers are alternately arranged on the second surface 10F side of the first insulating layer 10. An insulating layer made up of a plurality of layers may be used. In this case, the metal foil 12 is provided on the first insulating layer 10 of the insulating layer composed of a plurality of layers, and the metal foil is formed on the insulating layer forming the surface opposite to the first insulating layer 10 of the insulating layer composed of the plurality of layers. 22 may be provided.

  As the metal foils 12 and 22, for example, a copper foil having a thickness of 3 μm or more and 12 μm or less is used. However, the material of the metal foils 12 and 22 is not limited to this. The metal foils 12 and 22 may be, for example, film-like bodies or foil-like bodies made of other metals.

  When the insulating member constituting the first insulating layer 10 is a prepreg or the like, the first insulating layer 10 and each of the metal foils 12 and 22 are pressurized toward each other and further heated. As a result, the prepreg is fully cured, and the first insulating layer 10 and each of the metal foils 12 and 22 are joined.

  Next, as shown in FIG. 4B, a conduction hole 31a penetrating the first insulating layer 10 is formed. The conduction hole 31a is formed by irradiating the formation position of the first via conductor 31 (see FIG. 4C) of the first insulating layer 10 with laser light from the surface on the metal foil 12 side until the metal foil 22 is exposed. The When laser light is irradiated from the surface on the metal foil 12 side, a conductive hole 31a that is wide on the metal foil 12 side and narrow on the metal foil 22 side is formed. Examples of the laser light include, but are not limited to, a carbon dioxide laser and a YAG laser.

  Subsequently, a copper film (not shown) is formed in the conduction hole 31a by, for example, electroless plating of copper. This film may be formed by sputtering, vacuum deposition, or the like. The material for the coating is preferably copper, but is not limited to copper. For example, the thickness of the copper coating is 0.05 μm or more and about 1.0 μm or less.

  Subsequently, an electrolytic plating film is formed by electrolytic plating using the copper coating as a seed layer. As shown in FIG. 4C, an electrolytic plating film is embedded in the conduction hole 31a. The first via conductor 31 is formed by a plated film made of a copper film and an electrolytic plated film in the conduction hole 31a. Along with the formation of the first via conductor 31, a plating film 13 made of a copper coating and an electrolytic plating film is formed on the metal foil 12 on the first surface 10B side of the first insulating layer 10, and the metal on the second surface 10F side A plating film 23 made of a copper coating and an electrolytic plating film is formed on the foil 22. The metal foil 12 and the plating film 13 constitute a base portion 11b (see FIG. 1) for the heat radiating fins.

  As shown in FIG. 4D, the metal foil 22 and the plating film 23 are patterned to form the second conductor layer 21. For example, an etching resist film (not shown) is formed on the plating film 23, exposed through a mask formed according to the conductor pattern of the second conductor layer 21, and then developed. Etching is performed in a state where the portions of the metal foil 22 and the plating film 23 to be the conductor pattern of the second conductor layer 21 are covered with the etching resist. The portion of the plating film 23 exposed from the etching resist and then the portion of the metal foil 22 are sequentially removed, so that the second conductor layer 21 including the metal foil 22 having a predetermined conductor pattern and the plating film 23 is formed. The A land portion for component mounting is formed on the second conductor layer 21.

  As shown in FIG. 4E, a cover lay 51 having an opening on the component mounting land is formed on the second conductor layer 21. For example, a part for mounting a part on the coverlay film is subjected to window cutting. The processed cover lay film is laminated on the second conductor layer 21. Note that the window cutting method is not particularly limited, and a method using a big die, a laser processing method, or the like can be used. As the coverlay film, for example, a resin film having high heat resistance such as polyimide resin can be used. The resin film is attached to the second conductor layer 21 with an adhesive, for example.

  Subsequently, heat radiation fins 11 f (see FIG. 1) are formed on the plating film 13. As shown in FIG. 4F, a plating resist 41 for forming a radiation fin is formed on the plating film 13. The plating resist 42 is also formed on the second surface 10F side of the first insulating layer 10, that is, on the cover lay 51 and on the second conductor layer 21 constituting the component mounting land exposed from the cover lay 51. The The thickness of the plating resist 41 on the plating film 13 may be approximately the same as or slightly thicker than the height H (see FIG. 1) of the radiation fin 11f. Next, as shown in FIG. 4G, the opening 41a is provided in the plating resist 41 on the plating film 13 at the position where the radiation fins 11f are formed, for example, by photolithography. The plating film 13 is exposed on the bottom surface of the opening 41a.

  Subsequently, as shown in FIG. 4H, a thick conductor layer 15 to be the heat radiation fin 11f is formed in the opening 41a by electrolytic plating using the plating film 13 as a seed layer. The conductor layer 15 is preferably formed of the same material as that of the plating film 13, and is preferably formed of copper. The formation of the conductor layer 15 in the opening 41a may be performed not by electrolytic plating but by filling with a conductive paste. As the conductive paste, a conductive paste containing one or more metal particles selected from silver, copper, gold, nickel and the like can be used. As the metal particles, copper is preferable. After filling the conductive paste, the conductive paste is heated and cured. That is, the inside of the opening 41a is filled with the solidified material of the conductive paste. The conductor layer 15 is formed in the opening 41a.

  The conductor layer 15 may be formed at a height lower than the surface 41S of the plating resist 41, or may be formed at substantially the same height as the surface 41S. Therefore, the end face 15S of each fin formed from the conductor layer 15 on the side opposite to the plating film 13 can be recessed or substantially flush with the surface 41S of the plating resist 41.

  The end face 15S of each fin can then be polished. Radiating fins 11f are formed in which the heights H of the fins are substantially uniform. Polishing may be performed until the height H of each fin reaches a desired value. As described above, the preferred height H of the heat dissipating fins 11f is, for example, 200 μm or more and 1000 μm or less.

  Electrolytic plating for forming the conductor layer 15 is performed over an appropriate plating time corresponding to the height H and thickness D of the heat dissipating fins 11f. The electrolytic plating process may be performed a plurality of times depending on the characteristics of the plating solution and the plating conditions. As a result, as described above, for example, a fin having a tapered shape shown in FIG. 3 may be formed. By a plurality of times of plating, for example, fins having a fin thickness D of about 200 μm and a height H of about 600 μm can be formed. There is a possibility that a heat radiation fin with improved heat radiation performance can be obtained.

  Thereafter, the plating resists 41 and 42 are removed. As shown in FIG. 4I, the radiation fins 11 f made of the conductor layer 15 are formed on the plating film 13 that constitutes the base portion 11 b together with the metal foil 12. The printed wiring board 1 shown in FIG. 1 in which the first conductor layer 11 is provided with the radiation fins 11f is completed.

  In the above description, the process of forming the radiation fins 11f by forming the thick conductor layer 15 has been described by taking the printed wiring board 1 shown in FIG. 1 as an example. However, the radiation fin provided in the 1st conductor layer 11 is not limited to the structure shown by FIG. For example, in the method for manufacturing a wiring board according to the present embodiment, it is not essential to form the thick conductor layer 15 that becomes the heat radiation fins 11 f on the plating film 13. For example, instead of forming the thick conductor layer 15, the plating film 13 is formed thicker than the thickness of the conductor layer 15 in the example of FIG. 1 and the plating film 13 is etched to form the heat radiation fins 11 f. Also good. Another example of a method for manufacturing a wiring board according to an embodiment using such a thick plating film 13 will be described below with reference to FIGS. 5A to 5H, the same constituent elements as those of the printed wiring board 1 are denoted by the same reference numerals as those in FIG. 1, and the description of the method for forming the same constituent elements is appropriately omitted.

  First, as in FIG. 4A described above, the first insulating layer 10 having the metal foil 12 on the first surface 10B and the metal foil 22 on the second surface 10F opposite to the first surface 10B is prepared. Then, through a process similar to the process shown in FIG. 4B, a conduction hole 31a penetrating the first insulating layer 10 is formed as shown in FIG. 5A. As in the example shown in FIG. 4B, the conduction hole 31a has a shape in which the metal foil 12 side is wide and the metal foil 22 side is narrow. Thereafter, a copper coating (not shown) is formed in the conduction hole 31a.

  As shown in FIG. 5B, a thick plating film 130 is formed on the first surface 10B side of the first insulating layer 10 by electrolytic plating using a copper coating as a seed layer. That is, the first via conductor 31 is formed by embedding an electrolytic plating film in the conduction hole 31a and formed of a plating film made of the copper film and the electrolytic plating film in the conduction hole 31a. Along with the formation of the first via conductor 31, a thick plating film 130 made of a copper coating and a thick electrolytic plating film is formed on the metal foil 12 on the first surface 10 </ b> B side of the first insulating layer 10. In this example, the first conductor layer 11 is composed of a metal foil 12 and a thick plating film 130. In the present embodiment, the total thickness of the metal foil 12 and the plating film 130 is a size obtained by adding the height of the radiation fin 11f (see FIG. 1) to the thickness of the base portion 11b (see FIG. 1). Is approximately equal to That is, the plating film 130 may be formed with a thickness that is thicker than the height of the heat dissipating fins. In this example, unlike the example of FIG. 4C, no plating film is formed on the second surface 10 </ b> F side of the first insulating layer 10. For example, during the formation of the plating film 130, a plating resist (not shown) that covers the second surface 10F is formed.

  As shown in FIG. 5C, patterning similar to the process of FIG. 4D is performed on the metal foil 22. A second conductor layer 210 is formed. Similarly to the example of FIG. 4D, the second conductor layer 210 is provided with a land portion for component mounting. Subsequently, as shown in FIG. 5D, a cover lay 51 similar to the process of FIG. 4E is formed on the second conductor layer 210 so as to expose the land portion for component mounting.

  As shown in FIG. 5E, a resist layer 45 is formed on the plating film 130. Similar to the example of FIG. 4F, on the second surface 10F side of the first insulating layer 10, that is, on the cover lay 51 and on the second conductor layer 210 constituting the component mounting land exposed from the cover lay 51. Also, a resist layer 46 is formed. Next, as shown in FIG. 5F, an opening 45a is formed in the resist layer 45 by, for example, a photolithography technique so that the portion where the heat radiation fin is formed is covered with the resist layer 45 and the other portion is exposed from the resist layer 45. Provided.

  As shown in FIG. 5G, the plating film 130 exposed without being covered with the resist layer 45 is removed to a predetermined depth. However, the portion of the plating film 130 covered with the resist layer 45 is not removed. Radiation fins 11f are formed by portions of the plating film 130 that are covered with the resist layer 45 and are not removed. For the removal of the plating film 130, for example, a method such as etching or sand blasting is used. In the present embodiment, a part of the plating film 130 needs to be removed to a depth substantially equal to the height H of the radiation fin 11f. Therefore, when etching is used for the removal, for example, a method of spraying a chemical solution for etching with a strong momentum and spraying it on a predetermined position of the plating film 130 of the printed wiring board being manufactured can be used. By the removal, the heat radiating fins 11f in which each fin has a height H and the base part 11b formed from the metal foil 12 and a part of the plating film 130 on the metal foil 12 side are formed. Also in this example, even if the side surface of each fin of the heat radiating fin 11f is not substantially perpendicular to the metal foil 12, each fin has a tapered shape or has a diameter that gradually decreases. You may have.

  Subsequently, the resist layers 45 and 46 are removed. As shown in FIG. 5H, the printed wiring having the first conductor layer 11 including the base portion 11 b made of a part of the metal foil 12 and the plating film 130 and the heat radiation fin 11 f made of the remaining part of the plating film 130. The plate 100 is completed.

  Instead of forming the thick plating film 130 as shown in FIGS. 5A to 5H, the first insulating layer 10 in which a thick metal foil is provided on the first surface 10B may be used. Still another example of the method for manufacturing a wiring board according to such an embodiment will be described below with reference to FIGS. 6A to 6I, the same constituent elements as those of the printed wiring board 1 are denoted by the same reference numerals as those in FIG. 1, and descriptions of the method of forming the same constituent elements are appropriately omitted.

  As shown in FIG. 6A, a thick metal foil 120 is provided on the first surface 10B, and the second surface 10F opposite to the first surface 10B has the same thickness as the example shown in FIG. 4A. The 1st insulating layer 10 in which the metal foil 22 thin compared with the metal foil 120 is provided is prepared. In the example of FIG. 6A, the metal foil 120 thicker than the thickness H of the heat radiation fin (see FIG. 6H) is provided on the first insulating layer 10 as the thick metal foil 120. For example, a copper foil is used as the thick metal foil 120. The metal foil 120 may be a metal foil made of other materials. The joining of the metal foils 120 and 22 and the first insulating layer 10 can be performed similarly to the example of FIG. 4A.

  Next, as shown in FIG. 6B, a conduction hole 32a penetrating the first insulating layer 10 is formed. Unlike the example of FIGS. 4B and 5A, in this example in which the thick metal foil 120 is provided on the first surface 10B, the conduction hole 32a is the first via conductor 32 of the first insulating layer 10 (FIG. 6C). Reference) is formed by irradiating laser light from the surface on the metal foil 22 side which is a thin metal foil. Therefore, the conduction hole 32a has a shape in which the metal foil 22 side is wide and the metal foil 120 side is narrow. The metal foil 120 is exposed on the bottom surface of the conduction hole 32a.

  After a copper film (not shown) is formed in the conduction hole 32a, the same process as that shown in FIGS. As shown in FIG. 6C, a second via conductor 32 formed of a plating film made of a copper film and an electrolytic plating film in conduction hole 32a is formed. Along with the formation of the second via conductor 32, a plating film 13 made of a copper film and an electrolytic plating film is formed on the metal foil 120, and a plating film 23 made of a copper film and an electrolytic plating film is formed on the metal foil 22. That is, in this example, the first conductor layer 11 is composed of the thick metal foil 120 and the plating film 13. Next, the metal foil 22 and the plating film 23 are patterned to form the second conductor layer 21 including a land portion for component mounting (see FIG. 6D). Further, a cover lay 51 having an opening on a land portion for component mounting is formed on the second conductor layer 21 (see FIG. 6E).

  Subsequently, a process similar to the process illustrated in FIGS. 5E to 5H is performed, and the heat radiation fins are formed in the first conductor layer 11. First, in a step similar to the step shown in FIG. 5E, a resist layer 45 is formed on the plating film 13, and the resist layer 46 is formed on the cover lay 51 and on the second conductor layer 21 exposed from the cover lay 51. Formed (see FIG. 6F). An opening 45a is provided in the resist layer 45 in the same process as shown in FIG. 5F (see FIG. 6G). Next, as in the step shown in FIG. 5G, a part of the metal foil 120 where the plating film 13 exposed without being covered with the resist layer 45 and the resist layer 45 are not laminated is etched by etching or the like. Removed (see FIG. 6H). In this example, since the plating film 13 and the thick metal foil 120 are laminated in order from the surface 11S, the first conductor layer 11 is removed from the plating film 13 other than the location where the radiation fins 11f are formed, and then thick metal is used. The foil 120 is removed until the depth of etching from the surface 11S is approximately equal to the desired height H of the fin. Thereafter, similar to the example shown in FIG. 5H, the resist layers 45 and 46 are removed. As shown in FIG. 6I, a first conductor including a heat radiating fin 11f made of a part of the plating film 13 and the metal foil 120 and a base part 11b made of a part of the metal foil 120 on the first insulating layer 10 side. The printed wiring board 101 having the layer 11 is completed.

  The printed wiring board manufacturing method of the embodiment is not limited to the method described with reference to FIGS. 4A to 4I, FIGS. 5A to 5H, and FIGS. 6A to 6I. In the printed wiring board manufacturing method of the embodiment, an arbitrary process may be added in addition to the above-described processes, and a part of the processes described in the above description may be omitted. For example, a step of stacking the heat dissipation sheet on the plating film 13 may be added after the step of forming the plating film 13 shown in FIG. 4C. An example is shown in FIG. In this example, after the plating film 13 is formed, a heat radiation sheet 61 is laminated on the plating film 13, and a metal film 62 is laminated thereon, and is heated and pressed. As the heat radiating sheet 61, for example, a heat radiating sheet made of silicone or acrylic having excellent thermal conductivity can be used. For example, a copper foil is used as the metal film 62. However, the materials of the heat dissipation sheet 61 and the metal film 62 are not limited to these. After the formation of the metal film 62, a process similar to the process shown in FIGS. A printed wiring board 200 in which a heat dissipation sheet 61 as shown in FIG. 7 is sandwiched between the first surface 10B side of the first insulating layer 10 may be formed.

DESCRIPTION OF SYMBOLS 1,100,101,200 Printed wiring board 10 1st insulating layer 10B 1st surface of 1st insulating layer 10F 2nd surface of 1st insulating layer 11 1st conductor layer 11b Base part 11f Radiation fin 12, 22, 120 Metal Foil 13, 23, 130 Plating film 15 Conductor layer 21, 210 Second conductor layer 31, 32 First via conductor 41, 42 Plating resist 45, 46 Resist layer 51 Coverlay E1 Electronic component

Claims (15)

An insulating layer having a first surface and a second surface opposite to the first surface;
A second conductor layer laminated on the second surface side of the insulating layer;
A printed wiring board including a first conductor layer that is laminated on the first surface side of the insulating layer and is thicker than the second conductor layer,
The first conductor layer includes radiating fins. The printed wiring board according to claim 1,
The first conductor layer is made of the same material. The printed wiring board according to claim 1,
The radiating fin is formed of a solidified product of a plating film or a conductive paste. The printed wiring board according to claim 1,
The length of the radiation fin is 80 μm or more and 1000 μm or less. The printed wiring board according to claim 1,
The said heat radiating fin becomes a shape which tapers in steps as it goes to the front-end | tip. 2. The printed wiring board according to claim 1, further comprising a coverlay formed on the second conductor layer. The printed wiring board according to claim 1,
A light emitting element mounting pad is formed on the second conductor layer. A method of manufacturing a printed wiring board,
Providing an insulating layer having a metal foil on each of the first surface and the second surface opposite to the first surface;
Forming a conduction hole penetrating the insulating layer;
Forming a first conductor layer including heat dissipating fins on the first surface of the insulating layer;
Forming a second conductor layer on the second surface of the insulating layer. It is a manufacturing method of the printed wiring board according to claim 8,
The formation of the conduction hole is formed from the first surface side, and a via conductor is formed when the first conductor layer is formed. The method for manufacturing a printed wiring board according to claim 9, wherein the first conductor layer is formed by:
Forming a plating film on the first surface of the insulating layer;
Forming a plating resist on the plating film;
Providing the plating resist with an opening exposing the plating film on the bottom surface;
Forming a conductor layer made of a solidified product of a plating film or a conductive paste in the opening;
Removing the plating resist to form the heat dissipating fins in the first conductor layer. The method for manufacturing a printed wiring board according to claim 9, wherein the first conductor layer is formed by:
Forming a plating film thicker than the length of the heat dissipating fin on the first surface of the insulating layer;
Forming a resist layer on the plating film;
Removing the plating film exposed without being covered with the resist layer by etching or grinding;
Removing the resist layer to form the heat dissipating fins in the first conductor layer. It is a manufacturing method of the printed wiring board according to claim 8,
Preparing the insulating layer includes providing a metal foil on the second surface and providing a metal foil on the first surface that is thicker than the metal foil provided on the second surface;
The manufacturing method further includes forming the conduction hole from the second surface side, and forming a via conductor when forming the second conductor layer. The method of manufacturing a printed wiring board according to claim 12, wherein the first conductor layer is formed.
Forming a plating film on the thick metal foil;
Forming a resist layer on the plating film;
Removing the plating film exposed without being covered with the resist layer, and etching or grinding the thick metal foil on which the resist layer is not laminated;
Removing the resist layer to form the heat dissipating fins in the first conductor layer. 9. The method for manufacturing a printed wiring board according to claim 8, further comprising forming a cover lay on the second conductor layer. The method for manufacturing a printed wiring board according to claim 8, wherein the first conductor layer is formed.
Forming a plating film on the first surface of the insulating layer;
Laminating a heat dissipation sheet on the plating film;
Forming a metal film on the heat dissipation sheet;
Forming a plating resist on the metal film;
Providing the plating resist with an opening exposing the metal film on the bottom surface;
Forming a conductor layer made of a solidified product of a plating film or a conductive paste in the opening;
Removing the plating resist to form the heat dissipating fins in the first conductor layer.

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