JP2017084913A - Printed wiring board and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board having a build-up layer formed of an insulation material having high thermal conductivity, in which a through hole can be formed easily in the build-up layer containing a high thermal conductivity filler, and a lamination void is not generated during lamination, and to provide a method of manufacturing the same.SOLUTION: A printed wiring board includes a core layer 10 where a conductor circuit 2 is formed in an insulator 1, a build-up layer 30 formed of an insulation material, having a heat conductivity of 3 W/mK or more, on at least one surface of the core layer 10, and a through hole 5 penetrating the build-up layer 30 and core layer 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a printed wiring board having a hybrid structure using a plurality of types of materials having different electrical characteristics, mechanical characteristics, and processability, and a method for manufacturing the same.

2. Description of the Related Art In recent years, with the increase in functionality and performance of electronic devices, there has been a demand for high-density mounting and thinning of printed wiring boards used therefor. Therefore, development and commercialization of high-performance build-up substrates suitable for semiconductor mounting using a combination of a high heat-resistant and low thermal expansion base material and a high heat conductive base material are progressing.
As such a printed wiring board, a hybrid structure board using a plurality of kinds of materials having different electrical characteristics, mechanical characteristics, and workability is preferable, and examples of the hybrid structure board include the following.

  For example, Patent Document 1 relates to a printed wiring board having two or more layers, and a manufacturing method of a thin multilayer printed wiring board in which a through hole land of an inner shield plate is used as a connection pad for forming an outer via hole and a taper angle is provided. Have been described. According to this method of manufacturing a printed wiring board, no conduction failure occurs in the via hole, and the thickness can be reduced.

Patent Document 2 describes a multilayer printed wiring board in which a through hole is formed so as to penetrate the core substrate and the lower interlayer resin insulation layer, and a via hole (via hole) is formed immediately above the through hole. . In this multilayer printed wiring board, the through hole and via hole are linear and the wiring length is shortened, so that the signal transmission speed can be increased and the through hole and the solder bump (conductive connection) Since the via hole connected to the pin) is directly connected, it is said that the connection reliability is excellent.
At this time, in the printed wiring board shown in Patent Document 2, a core material on which a substrate material (resin film) containing an alumina filler that provides high thermal conductivity is attached is processed by a drill and penetrates the core material. Prepare the through hole for the through hole.

However, since the alumina filler is very hard, drilling with a general drill causes rapid wear of the drill, so mass production with a general drill is impossible.
Accordingly, a carbide blade drill or a diamond coating drill is used as a drill for preparing a through hole for such a through hole. However, even a carbide blade drill is worn in about 100 hits, and the drilling cannot be performed. In addition, the diamond coating drill is expensive, has a low processing diameter accuracy, and has a problem that it is difficult to form a component mounting through hole.

Further, in drilling, the inner layer conductor may be spilled and adhered to the inner wall of the through hole pilot hole due to the worn blade. The photograph shown in FIG. 5 (a) shows a carbide blade drill having a drill diameter of φ1.3 mm with respect to a printed wiring board 101 having a resin layer 9 filled with a large amount of alumina as a thermal conductivity improving filler in the outermost layer ( This shows a state in which a through-hole lower hole 91 penetrating the printed wiring board 101 is opened for 800 hours using a not-shown). The carbide drill is not a coating drill such as DLC (Diamond Like Carbon).
At this time, as shown in the partial enlarged view of FIG. 5A, it can be seen that the inner layer conductor 92 of the printed wiring board 101 has fallen and is attached to the inner wall of the through hole lower hole 91. For this reason, there was a problem that the layers are short-circuited.

Furthermore, the resin used for the outermost layer (build-up layer) of the printed wiring board has a problem that a lamination void (void) is generated due to insufficient resin flow of the resin during lamination, resulting in poor conductor embedding.
6A is an overall photograph showing the layer structure of the conventional printed wiring board 102, and FIGS. 6B and 6C are enlarged views showing laminated voids generated around the conductor of the outermost insulating layer 93. FIG. It is a photograph. 6B and 6C, as indicated by circles in the drawing, the resin cannot be embedded around the conductor 94 of the outermost insulating layer 93, and a laminated void (resin void) 95 is generated.

JP-A-11-251746 JP 2001-127434 A

  The present invention relates to a printed wiring board in which a build-up layer is formed of an insulating material having high thermal conductivity, and a printed wiring board that can easily form a through hole in the build-up layer and that does not generate a laminated void during lamination, and its manufacture. It is an object to provide a method.

The present invention has been completed in order to solve the above problems, and has the following configuration.
(1) A core layer in which a conductor circuit is formed on an insulator, a buildup layer formed of an insulating material having a thermal conductivity of 3 W / mK or more on at least one surface of the core layer, and the buildup layer and the core A printed wiring board comprising a through hole penetrating the layer (2) The through hole penetrating the buildup layer and the core layer is connected to the via hole of the core layer and the via hole of the buildup layer The printed wiring board according to (1).
(3) The printed wiring board according to (1) or (2), wherein the insulating material of the buildup layer contains an alumina filler.
(4) The printed wiring board according to any one of (1) to (3), wherein a minimum melt viscosity of the insulating material of the buildup layer is 77 Pa · s or more.
(5) The printed wiring board according to any one of (1) to (4), wherein the buildup layer has higher thermal conductivity than the core layer.
(6) forming a conductor circuit on an insulator and forming a core layer; forming a through-hole penetrating the front and back surfaces of the core layer; and a surface with a thermal conductivity of 3 W / forming a build-up layer with an insulating material of mK or more, forming a via-hole pilot hole serving as an extension of the through-hole with a laser in the build-up layer immediately above the through-hole in the core layer, and the via hole A method of manufacturing a printed wiring board, comprising: plating a pilot hole to form a through hole that is directly connected to and through the through hole from the front surface to the back surface of the outer layer of the printed wiring board.

According to the present invention, since the insulating material having high thermal conductivity forming the buildup layer has a high minimum melt viscosity, it does not flow during the laminating press, and therefore does not block the core layer through hole.
Furthermore, although the build-up layer is formed of an insulating material having high thermal conductivity, the workability by laser processing is not inferior to that of general materials, so that a through hole can be easily formed.

It is explanatory drawing which shows one Embodiment of the printed wiring board which concerns on this invention. (A)-(e) is process explanatory drawing which shows one Embodiment of the manufacturing method of the printed wiring board concerning this invention. (F)-(i) is process explanatory drawing which shows one Embodiment of the manufacturing method of the printed wiring board concerning this invention. FIG. 4 is a partially enlarged top view of FIG. (A) is a photograph focusing on a polished surface of a cross section showing a state where a through hole is provided by drilling a resin layer filled with a large amount of alumina filler, and a partial photograph focusing on the drilled surface. (B) is the photograph which focused on the grinding | polishing surface of the cross section which shows the state after a desmear process of (a), and the partial photograph which focused on the drilling surface. (A) is a whole photograph which shows the layer structure of the conventional printed wiring board, (b) And (c) is an enlarged photograph which shows the laminated void produced | generated around the conductor of the outermost insulating layer of (a). .

As shown in FIG. 1, the printed wiring board 100 includes a core layer 10 in which a conductor circuit 2 is formed on an insulator 1, and a build formed of an insulating material having high thermal conductivity on at least one surface of the core layer 10. The up layer 30 and the through hole 5 penetrating the core layer 10 and the buildup layer 30 are included.
The through hole 5 is formed by connecting a through hole 6 in a core layer, which will be described later, and a via hole 7 in a buildup layer, and does not fill with resin inside, and penetrates the front and back surfaces of the printed wiring board 100.

  The insulator 1 will not be specifically limited if it is formed with the raw material which has insulation. Examples of such an insulating material include organic resins such as epoxy resin, bismaleimide-triazine resin, polyimide resin, and polyphenylene ether (PPE) resin. These organic resins may be used in combination of two or more. When using an organic resin as the insulator 1, it is preferable to mix and use a reinforcing material in the organic resin. Examples of the reinforcing material include glass fiber, glass nonwoven fabric, aramid nonwoven fabric, aramid fiber, and polyester fiber. Two or more of these reinforcing materials may be used in combination. The insulator 1 is preferably formed from an organic resin containing a glass material such as glass fiber. Furthermore, the insulator 1 may contain inorganic fillers such as silica, barium sulfate, talc, clay, glass, calcium carbonate, and titanium oxide.

  A conductor circuit 2 is formed on at least one surface of the insulator 1. The conductor circuit 2 is not particularly limited as long as it is a conductive circuit that is electrically connected to other components or a substrate, and examples thereof include conductive resin and metal plating. Particularly preferred is copper plating. The copper plating may be chemical copper plating (electroless copper plating), but is preferably electrolytic copper plating.

  The conductor circuit 2 is formed by forming a hole 2a in the insulator 1 by drilling or laser processing, and providing a conductor in the hole 2a by plating. After plating, the inside of the hole is filled with resin as necessary.

In the present embodiment, the core layer 10 may have a multilayer structure, or may be a laminated plate 20 in which a plurality of insulating layers 11 are laminated. Similar to the core layer 10, the insulating layer 11 includes an insulator 1 ′ having an insulating cloth material 4 ′ and a via 3 electrically connected to the conductor circuit 2. The core layer 10 and the insulating layer 11 may be formed of the same member. The via 3 is formed by filling the hole 3a with a conductive material. However, the via 3 may be formed by providing a conductor layer on the inner wall surface of the hole 3a.
In addition, from the viewpoint of workability as a whole printed wiring board, the core layer 10 should have a lower thermal conductivity than the buildup layer 30, specifically 0.3 to 0.7 W / mK. There should be. Furthermore, the core layer 10 may have a glass transition temperature (Tg> 175 ° C.) and a low thermal expansion of 6 ppm (x, y) / K or less.

  The laminated plate 20 including the core layer 10 is provided with a through hole 6 in the core layer that penetrates the core layer 10 and the insulating layer 11 laminated thereon. The through hole 6 in the core layer is a part of the through hole 5 described later, and a conductor layer 60 made of metal plating such as copper plating is formed on the inner wall surface thereof.

A buildup layer 30 is provided on at least one side of the laminate 20. The build-up layer 30 is formed of an insulating resin having high thermal conductivity, and is a via hole 3 ′ that is electrically connected to the conductor circuit 2 of the lower laminate 20 and a via hole that is connected to the through hole 6 of the core layer 10. 7.
A solder resist 8 is provided on the outer layer of the buildup layer 30. The solder resist 8 is provided around the through hole 5 and the conductor layer 70 at the periphery of the opening.

  In order for the insulating resin forming the buildup layer 30 to have high thermal conductivity, a high thermal conductive filler may be contained. The high thermal conductive filler is preferably an inorganic filler such as an alumina filler, a silicon nitride filler, or a sapphire filler, and the high thermal conductive filler content relative to the insulating resin is preferably 50 vol% or more, for example. This high thermal conductive filler may be one kind or a combination of plural kinds.

  The insulating resin of the buildup layer 30 may have a minimum melt viscosity of 77 pa · s or more. Therefore, the build-up layer 30 is less likely to flow due to heat or pressure during lamination by known press processing (heating / pressurization) to the laminated plate 20, and when forming the via hole 7 connected to the through hole 6 of the core layer, Even if the insulating resin forming the build-up layer 30 is melted by the heat at the time of lamination, the resin of the build-up layer 30 flows into the through-hole 6 of the core layer already formed in the lower core layer 10 or the insulating layer 11. There is nothing.

  The printed wiring board 100 in which the buildup layer 30 is laminated on the laminated board 20 is provided with through-holes 5 that penetrate the front and back surfaces of the printed wiring board 100. The through hole 5 is formed by connecting the through hole 6 in the core layer and the via hole 7 in the buildup layer 30. A conductor made of metal plating such as copper plating is formed on the inner wall surface of the through hole 5 and connected to a wiring pattern (not shown) on the front and back surfaces of the printed wiring board 100.

Next, the manufacturing method of one Embodiment of the printed wiring board concerning this invention is demonstrated. The method for producing a printed wiring board according to the present invention includes the following steps (I) to (VIII).
(I) A step of preparing an insulator including an insulating cloth material and providing a conductor circuit on the insulator to form a core layer.
(II) A step of laminating an insulating layer on the surface of the core layer to form a laminate, and providing a via in the insulating layer.
(III) The process of forming the through-hole pilot hole which penetrates a laminated board by drill processing or laser processing.
(IV) After forming a conductor layer (plating treatment) with a conductor material on the opening peripheral edge and inner wall surface of the through hole pilot hole, an etching resist is formed, exposed and developed, and portions other than the circuit portion of the conductor layer are formed. Etching to form through holes in the laminate (V) Forming a build-up layer on the surface of the laminate with an insulating material having high thermal conductivity.
(VI) A step of forming a via hole for conductor circuit and a via hole pilot hole connected to the through hole by laser processing in a buildup layer immediately above the through hole of the laminated plate, and performing a desmear process.
(VII) After forming a conductor layer (plating treatment) with a conductor material on the opening peripheral edge and inner wall surface of the via hole pilot hole, an etching resist is formed, exposed and developed, and portions other than the circuit portion of the conductor layer are etched. And a step of forming a through hole in which the through hole of the laminate is connected to the via hole of the buildup layer.
(VIII) A step of forming a solder resist on the surface of the build-up layer.

  A method for manufacturing a printed wiring board according to the present invention will be described with reference to FIGS. In addition, the description about the member mentioned above is abbreviate | omitted.

FIG. 2A shows the insulator 1 including the above-described insulating cloth material 4 on which a conductive metal foil 1a such as a copper foil has been formed.
This insulator 1 is penetrated by drilling to form a hole 2a for forming a conductor circuit (FIG. 2B).
Further, after a conductor material such as copper plating is formed in the hole 2a, a dry film (not shown) is attached to the surface of the insulator 1 by a known method, exposed and developed, and after etching, the conductor circuit 2 When the dry film other than the place where the film is formed is peeled, the core layer 10 having the conductor circuit 2 as shown in FIG.

  Next, an insulating layer 11 made of an insulator 1 'including an insulating cloth material 4' is laminated on at least one surface of the core layer 10 to form a laminated plate 20, and then a conductor circuit of the core layer 10 is formed by laser processing. A through hole lower hole 6a for forming a through hole 6 in the core layer that penetrates the front and back surfaces of the laminated plate 20 is formed by laser processing or drilling. .

Next, a conductor layer is formed with a conductor material in each hole (hole) of the hole 3a and the through-hole lower hole 6a and on both surfaces of the laminated plate 20 (plating treatment). The conductor material is preferably the same as that on which the conductor circuit 2 is formed. For example, copper plating may be used, and the copper plating may be chemical copper plating (electroless copper plating) or electrolytic copper plating. The method for forming the via 3 is the same as that of the conductor circuit 2 and is omitted.
After plating the hole 3a and the through-hole lower hole 6a, a dry film is applied to the formation position of the hole 3a and the through-hole lower hole 6 on the surface of the laminate 20 by a known method, exposed and developed, When the dry film in the place where the conductor circuit is formed after the etching is peeled off, as shown in FIG. 2 (e), the conductor layer 60 is formed on the inner wall surface, and the core layer through-hole 6 penetrating the front and back surfaces of the laminate 20 Thus, the conductor circuit 2 formed with the conductor material and the via 3 electrically connected can be obtained.
The insulating layer 11 can be formed by stacking an arbitrary number, and the via 3 is formed every time the insulating layer 11 is formed.

  Next, as shown in FIG. 3 (f), a buildup layer 30 is formed on at least one side of the laminate 20. This buildup layer 30 contains a high thermal conductivity filler (for example, alumina filler) in the resin of the insulating material and has a thermal conductivity of 3 W / mK or more, more preferably 5 W / mK or more. Become. As an insulating material for forming the build-up layer 30, for example, CD-7200TY (manufactured by Risho Kogyo Co., Ltd.), which is a resin-coated copper foil obtained by integrating an insulating adhesive resin and a copper foil, may be used.

  Next, as shown in FIG. 3G, in the buildup layer 30, a via hole pilot hole of a via hole 7 that is an extended portion of the through hole 6 of the core layer is directly above the through hole 6 of the core layer of the laminate 20. 7a and hole 3a 'for connecting to via 3 are formed by laser processing.

Laser processing for forming the via hole prepared hole 7a is performed as shown in FIG. That is, the laser L is irradiated along the inner peripheral surface of the through hole 6 in the core layer (laser trajectory is indicated by L) so that the diameter of the via hole prepared hole 7a is larger than the diameter of the through hole 6 in the core layer. The via hole pilot hole 7a is connected to the upper and lower openings of the through hole 6 in the core layer.
Examples of laser light used in this laser processing include a CO ₂ laser and a UV-YAG laser.
In addition, the residue (not shown) of the insulating materials 1 and 1 ′ at the time of opening may remain in the opening portion, the hole wall, or the like due to the laser processing. In that case, the residue is removed by desmear treatment.

Next, a conductive layer 70 is formed (plating treatment) with a conductive material on the opening peripheral edge and inner wall surface of the via hole pilot hole 7a, and then an etching resist is formed, exposed and developed, and other than the circuit portion of the conductive layer 70 The portion is etched to form a through hole 5 in which the through hole 6 in the core layer of the laminated plate 20 and the via hole 7 in the buildup layer 30 are connected as shown in FIG. This through hole 5 penetrates both the laminate 20 and the buildup layer 30.
At this time, since the conductor layer 60 of the through hole 6 in the core layer of the laminated plate 20 is subjected to the second plating process, the plating thickness is thicker than the conductor layer 70 on the inner wall surface of the via hole 7.
The hole 3a ′ forms the via 3 ′ by the same method as the via 3 described above.

Finally, when the solder resist 8 is formed as an insulating resin layer on the surface of the buildup layer 30, the printed wiring board 100 shown in FIG. 3 (i) is completed.
The structure of the laminated board 20 has been described with the build-up multilayer wiring board. Needless to say, the laminated board 20 can be applied not only to a normal multilayer printed wiring board but also to a multilayer printed wiring board, a laminated multilayer printed wiring board, or the like.

As described above, a via hole can be easily formed in the upper layer (build-up layer) formed of an insulating material having high thermal conductivity by laser processing. Therefore, the via hole and the through hole provided in the lower layer (core layer) And a through hole penetrating the front and back surfaces of the printed wiring board can be formed.
In addition, the resin having high thermal conductivity forming the upper layer (build-up layer) has a minimum melt viscosity as high as 77 Pa · s or higher, so that the resin does not flow during the laminating press and blocks the through hole in the lower layer (core layer). There is nothing.

DESCRIPTION OF SYMBOLS 1,1 'Insulator 1a Conductive metal foil 2 Conductor circuit 3, 3' Via 3a, 3a 'Hole 2a Hole 4, 4' Insulating cloth material 5 Through hole 6 Core layer through hole 6a Through hole lower hole 7 Via hole 7a Via hole pilot hole 8 Solder resist 9 Resin layer 10 Core layer 11 Insulating layer 20 Laminated plate 30 Build-up layer 60, 70 Conductor layer 91 Through hole lower hole 92 Inner layer conductor 93 Outermost insulating layer 94 Conductor 95 Laminated void 100. 101,102 Printed wiring board L Laser

Claims (6)

  A core layer in which a conductor circuit is formed on an insulator, a buildup layer formed of an insulating material having a thermal conductivity of 3 W / mK or more on at least one surface of the core layer, and the buildup layer and the core layer are penetrated Printed wiring board comprising a through-hole   The printed wiring board according to claim 1, wherein the through hole penetrating the buildup layer and the core layer is formed by connecting a through hole in the core layer and a via hole in the buildup layer.   The printed wiring board according to claim 1, wherein the insulating material of the buildup layer contains an alumina filler.   The printed wiring board according to claim 1, wherein a minimum melt viscosity of the insulating material of the buildup layer is 77 Pa · s or more.   The printed wiring board according to claim 1, wherein the buildup layer has higher thermal conductivity than the core layer. Forming a conductor circuit on an insulator and forming a core layer;
Forming a through hole penetrating the front and back surfaces of the core layer;
Forming a buildup layer with an insulating material having a thermal conductivity of 3 W / mK or more on the surface of the core layer;
Forming a via-hole pilot hole, which is an extension of the through-hole, with a laser in a build-up layer immediately above the through-hole of the core layer;
Manufacturing the printed wiring board, comprising: plating the via hole pilot hole to form a through hole that is directly connected to and through the through hole from the front surface to the back surface of the outer layer of the printed wiring board Method.