JP2007115809A - Wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board capable of easy microfabrication of a wiring pattern and prevention of curvature even in a case of using a thin-foil core board. <P>SOLUTION: Metallic foil 2 is inserted between foil core boards 5. Both core insulating layers 3 and 4 comprise a composite material impregnated with a synthetic resin for strengthening a substrate, such as a glass fiber. With such a structure, even if the thickness of the foil core board 5 is thin (0.2-0.6 mm), it is made possible to suppress the curvature of a wiring board 1 on the whole. Furthermore, wiring laminates L1 and L2 wherein a conductive layer and an insulating layer are laminated alternately are formed in both the main surfaces CP1 and CP2 of the foil core boards 5. Since a glass fiber or the like is not contained in this insulating layer, it is easy to form a fine via. It becomes easy to form a fine wiring pattern by using a semi additive method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wiring board.

  In recent years, due to the demand for higher functionality and lighter, thinner and smaller electronic devices, high-density integration has rapidly progressed in electronic components such as IC chips and LSIs. There is a demand for higher-density wiring and multi-terminals than ever before.

  As such a package substrate, a build-up multilayer wiring substrate is employed. The build-up multilayer wiring board uses a rigid property of an insulating core substrate (glass epoxy substrate such as FR-4) in which a reinforcing fiber is impregnated with a resin, and is made of a polymer material on both main surfaces thereof. Insulator layers and conductor layers are alternately laminated. In such a build-up multilayer wiring board, high-density wiring is realized in the build-up layer, while the core board plays a reinforcing role. For this reason, the core substrate is configured to be very thick compared to the build-up layer, and the wiring (called a through-hole conductor) for establishing electrical conduction between the build-up layers arranged on the respective main surfaces is thick inside the core substrate. It penetrates in the vertical direction. However, at the present time when the signal frequency to be used has become a high frequency band exceeding 1 GHz, there is a problem that the wiring passing through such a thick core substrate contributes as a large inductance.

Therefore, it has been considered to make the core substrate thin. However, if the core substrate is too thin, rigidity cannot be ensured, and there arises a problem that it becomes difficult to manufacture a wiring substrate due to warping and a problem that it is difficult to assemble an IC chip. . In order to solve this problem, for example, in the wiring substrate disclosed in Patent Document 1 below, a copper plate (metal plate) having a thickness of about 100 μm is used as the core substrate. By using a metal plate, the rigidity of the entire wiring board can be secured, and the warpage can be reduced.
JP 2000-101245 A

  However, in the above wiring board, a prepreg obtained by impregnating epoxy resin into continuous porous PTFE or glass fiber is used as the insulating layer constituting the wiring laminated portion (build-up layer), so that a fine via is formed. Was relatively difficult. Therefore, there has been a demand for a wiring board in which the wiring pattern can be easily miniaturized.

  The present invention has been made in the background as described above. In particular, it is an object of the present invention to provide a wiring board that is less likely to warp even when a thin core board is used and the wiring pattern can be easily miniaturized.

Means for Solving the Problems and Effects of the Invention

This invention
A foil-type core substrate including a metal foil, and a first core insulating layer and a second core insulating layer which are disposed on both main surfaces of the metal foil and are composed of a composite material in which a reinforced base material is impregnated with a synthetic resin; ,
A first wiring laminated portion and a second wiring formed by alternately laminating an insulating layer made of a non-composite material not containing a reinforced base material and a conductive layer made of a conductive material on both main surfaces of the core substrate A laminated part;
A wiring board comprising:

  According to the said invention, the foil type core board | substrate which pinched | interposed metal foil (for example, copper foil of thickness 25-100 micrometers) with the 1st and 2nd core insulating layer is used. The first and second core insulating layers are composed of a composite material obtained by impregnating a reinforcing resin such as glass fiber with a synthetic resin. Since the metal foil is located at the center of the foil-type core substrate, relatively high rigidity can be ensured even if the thickness of the entire foil-type core substrate is thin, and warping of the wiring board can be suppressed. As a result, it becomes easy to manufacture the wiring board. Further, the assembly of the IC chip is facilitated, and it is possible to cope with the further narrowing of the solder bumps.

  On the other hand, on both main surfaces of the foil-type core substrate, a wiring laminated portion in which conductor layers and insulating layers are alternately laminated is formed. This insulating layer is made of a non-composite material that does not contain glass fibers or the like. Is done. Therefore, relatively fine vias can be formed in this insulating layer, and a well-known semi-additive method can be used in the process of forming the wiring laminated portion, thereby facilitating the miniaturization of the wiring pattern.

  In the conventional wiring board (for example, Patent Document 1), all of the insulating layers laminated on both surfaces of the metal foil are made of a composite material (a reinforced base material such as glass fiber or continuous porous PT impregnated with a synthetic resin). Was composed. Therefore, the rigidity of the entire wiring board is high, and it is difficult to warp. However, as in the present invention, when the insulating layer constituting the wiring laminated portion does not include a reinforced base material, the overall rigidity is low, so that it is vulnerable to warping stress. Therefore, the effect of increasing the rigidity of the foil-type core substrate by inserting the metal foil is particularly remarkable.

  Note that the thickness of the foil-type core substrate is preferably 0.2 to 0.6 mm. The reason is that if it is less than 0.2 mm, it is too thin, and even if a metal foil is inserted, warpage is likely to occur, and if it exceeds 0.6 mm, the inductance becomes high and becomes unsuitable for high frequencies. A more desirable thickness is 0.25 to 0.55 mm, and further desirably 0.3 to 0.5 mm.

On the other hand, the metal foil can be connected to GND or used as a power supply unit. In that case, the through-hole conductors formed on the foil-type core substrate (to connect the first and second wiring laminated portions). There is a problem that the conductor) contacts the metal foil. In order to solve this problem, the following configuration may be employed. That is,
A metal foil through hole formed in a predetermined position of the metal foil;
It is formed through the foil-type core substrate, electrically connects the first wiring laminated portion and the second wiring laminated portion, and is located inside the metal foil through hole and insulated from the metal foil. Through-hole conductors,
A wiring board comprising:

  In the present invention, even if the foil-type core substrate is thin, warpage is unlikely to occur. Therefore, when forming a through hole in the manufacturing process, a plurality of foil-type core substrates can be stacked and drilled at once. Therefore, there is an effect that the manufacturing cost can be reduced.

  The thickness of the metal foil is preferably 25 to 100 μm. The reason is that warpage is likely to occur when the thickness of the metal foil is less than 25 μm, and when the thickness exceeds 100 μm, it is difficult to etch the metal foil through-holes in the manufacturing process described later. The thickness of metal foil becomes like this. More preferably, it is 25-75 micrometers, More preferably, it is 30-50 micrometers.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a schematic cross-sectional view of a wiring board 1 according to the present invention. As described above, the wiring substrate 1 includes the metal foil 2 and the first core insulating layer 3 and the second core insulating layer 4 disposed on both main surfaces MP1 and MP2 of the metal foil 2, The foil-type core substrate 5 is constituted by the first and second core insulating layers 3 and 4. The entire thickness of the foil-type core substrate 5 is 0.2 to 0.6 mm, and the thickness of the metal foil 2 is 25 to 100 μm. As the metal foil 2, a copper foil is suitably used. The first and second core insulating layers 3 and 4 are both composed of a composite material obtained by impregnating a reinforced base material such as glass fiber, PTFE (fluorine resin), or aramid fiber with a synthetic resin (for example, epoxy resin). Yes.

  On the other hand, the first main surface CP1 of the foil-type core substrate 5 is formed with a first wiring laminated portion L1 in which insulating layers V1 and V2 and conductor layers M1 to M3 are alternately laminated, and the second main surface CP2 has an insulating layer. A second wiring laminated portion L2 in which V11, V12 and conductor layers M11 to M13 are alternately laminated is formed. Both the insulating layers V1 and V2 of the first wiring laminated portion L1 and the insulating layers V11 and V12 of the second wiring laminated portion L2 are made of a synthetic resin (non-composite material) that does not include a reinforced base material such as glass fiber. Yes.

  As will be described later, in the process of manufacturing the wiring substrate 1, a conductor layer and an insulating layer are sequentially laminated on both main surfaces CP1 and CP2 of the foil-type core substrate 5, but heat is applied at this time. When cooled, a difference in thermal shrinkage occurs due to a difference in wiring density between the first wiring laminated portion L1 and the second wiring laminated portion L2, and warping stress is applied to the foil-type core substrate 5. However, in the present invention, since the metal foil 2 is inserted into the foil-type core substrate, even if such warping stress is generated, the entire substrate is hardly warped. Therefore, it is possible to prevent problems such as the substrate warped in the manufacturing process coming into contact with another device. Conventionally, when manufacturing such a thin core product, it has been necessary to use a dedicated line (thin core dedicated line) based on the assumption that warpage occurs. Thus, it is possible to use a line (thick core line) for producing a product that is unlikely to warp, and thus it is possible to increase the operating efficiency of the factory.

  In the conventional technique (for example, Patent Document 1), since the insulating layers V1 to V12 also use composite materials, the rigidity of the first and second wiring laminated portions L1 and L2 is relatively high. However, since the insulating layers V1 to V12 are made of non-composite materials in the present invention, the rigidity of the first and second wiring laminated portions L1 and L2 is relatively low, and thus the effect of inserting the metal foil 2 is particularly noticeable.

  As described above, the entire thickness of the foil-type core substrate 5 is set to 0.2 to 0.6 mm. The reason is that if it is less than 0.2 mm, it is too thin, and even if the metal foil 2 is inserted, warping is likely to occur, and if it exceeds 0.6 mm, the inductance becomes high, so it is not suitable for high frequencies. is there. Moreover, the thickness of the metal foil 2 is 25-100 micrometers. The reason is that warpage tends to occur when the thickness is less than 25 μm, and when the thickness exceeds 100 μm, it is difficult to form the metal foil through hole 13 by etching in the manufacturing process described later.

  The structure of the wiring board 1 will be described in more detail. Through-holes 6a and 6b are formed through the foil-type core substrate 5 by a drill, a laser, or the like, and through-hole conductors 7a and 7b for connecting the core conductor layers M1 and M11 to each other are formed on the inner wall surfaces thereof. More specifically, the metal foil 2 has a metal foil through hole 13 formed at a predetermined position, and the first through hole 6a passes through the foil core substrate 5 at the position where the metal foil through hole 13 is formed. Is formed. The diameter of the first through hole 6 a is smaller than the diameter of the metal foil through hole 13 so that the inner peripheral surface of the first through hole 6 a does not contact the inner peripheral surface of the metal foil through hole 13. Thereby, the first through-hole conductor 7a can be insulated from the metal foil 2. On the other hand, the second through-hole conductor 7 b is connected to the metal foil 2. That is, the metal foil 2 can be connected to GND or used as a power supply unit. In this case, the second through-hole conductor 7b is fixed at the same potential as the metal foil 2.

  In addition, first insulating layers V1 and V11 made of a non-composite material (for example, epoxy resin) are formed on the core conductor layers M1 and M11, respectively. Further, first conductor layers M2 and M12 constituting a wiring pattern are formed on the surface by Cu plating. The core conductor layers M1 and M11 and the first conductor layers M2 and M12 are interconnected by vias 12, respectively. The via 12 has a via hole 12h, a via conductor 12s provided on the inner peripheral surface thereof, and a via pad 12p provided so as to be electrically connected to the via conductor 12s on the bottom surface side.

  In addition, second insulating layers V2 and V12 made of a non-composite material are formed on the first conductor layers M2 and M12, and pads 9 and 11 are formed on the surface by the second conductor layers M3 and M13. Yes. The surfaces of the second insulating layers V2 and V12 are covered with solder resists SR1 and SR11, and openings 17 for individually exposing the pads 9 and 11 are formed. On the other hand, solder bumps 10 for connection to an IC chip or the like are formed on the pads 9. The pad 11 is used for connecting to a motherboard or the like by a pin grid array (PGA) or a ball grid array (BGA). As shown in FIGS. 2A and 2B, the pads 9 and 11 are arranged in a grid pattern.

  Next, the manufacturing method of the wiring board 1 which concerns on this invention is demonstrated using process drawing of FIGS. First, as shown in FIG. 3A, a metal foil 2 is prepared, a photoresist 14 is applied to one main surface MP1 to form a predetermined pattern, and a protective resin layer 15 is applied to the other main surface MP2 (FIG. 3A). 3B). Thereafter, the metal foil through holes 13 are formed by wet etching, and the photoresist 14 and the protective resin layer 15 are removed (FIGS. 3C and 3D). As described above, since the thickness of the metal foil 2 is 100 μm or less, the etching process can be performed without difficulty. Thereafter, a composite material (prepreg) in which glass fiber is impregnated with an epoxy resin and a copper foil are stacked, and thermocompression bonded by a vacuum hot press machine (not shown), whereby the first and second core insulating layers 3 and 4 and copper The foils Cu1 and Cu2 are formed. The inside of the metal foil through-hole 13 is filled with an epoxy resin that has exuded from the composite material (FIG. 3E).

  Subsequently, through holes 6a and 6b are drilled at predetermined positions of the foil-type core substrate 5 using a drill or a laser (FIG. 3F). The diameter of the through hole 6a is made smaller than the diameter of the metal foil through hole 13, and the through hole 6a is positioned so that the metal foil 2 is not exposed from the inner peripheral surface. In this step, since the thickness of the foil-type core substrate 5 is sufficiently thin, a plurality of (for example, two or three) foil-type core substrates 5 can be stacked and punched together. Thereafter, the conductor patterns of the core conductor layers M1 and M11 and the through-hole conductors 7a and 7b are formed by a known subtractive method (FIG. 4G). That is, an electroless copper plating process is performed to form an electroless copper plating layer in the copper foils Cu1, Cu2 and the through holes 6a, 6b, and then a photoresist is applied to form a predetermined pattern by exposure. Then, using the electroless copper plating layer as a common electrode, the opening of the photoresist and the inside of the through hole 6 are subjected to electrolytic copper plating to increase the thickness, and then the photoresist is removed to form an unnecessary electroless copper plating layer. Etch away. Through this series of steps, the copper foils Cu1 and Cu2 are increased in thickness to become the core conductor layers M1 and M2.

  Next, the inside of the through-hole conductors 7a and 7b is filled with a filler 8 made of an epoxy resin, and the main surfaces MP1 and MP2 of the foil-type core substrate 5 are not filled with an epoxy resin (non-composite material). Is applied to form first insulating layers V1 and V11 (FIG. 4H). Thereafter, a via hole 16 is formed at a predetermined position by a laser (FIG. 5I). At this time, if glass fibers or the like are included in the first insulating layers V1 and V11, a large amount of energy is required to cut the glass fibers by the laser, and it becomes difficult to form the fine via holes 16, It may be difficult to finish the inner surface cleanly. However, in the present invention, since the first insulating layers V1 and V11 do not contain glass fiber or the like, such a problem hardly occurs.

  Next, the conductor patterns M2 and M12 and the vias 12 are formed by a known semi-additive method (FIG. 5J). That is, after the surface of the first insulating layers V1 and V11 and the inner surface of the via hole 16 are roughened, an electroless copper plating process is performed to form an electroless copper plating layer. Then, a photoresist is applied to form a predetermined pattern by exposure. After that, using the electroless copper plating layer as a common electrode, the opening of the photoresist and the inner surface of the via hole 16 are subjected to electrolytic copper plating to increase the thickness, and the photoresist is removed to remove the unnecessary electroless copper plating layer by a quick etching method. To remove. Since such a semi-additive method is suitable for a fine pattern, it is easy to miniaturize wiring.

  Thereafter, the second insulating layers V2 and V12 are formed by applying an epoxy resin or the like, a via hole is drilled at a predetermined position using a laser, and then the conductors of the second conductor layers M3 and M13 are again used by using the semi-additive method. A pattern is formed (FIG. 5K). And solder resist S1, S12 is apply | coated and a photo process is performed, and the opening part 17 which exposes the pads 9 and 11 separately is formed. Thereafter, a solder paste is screen-printed on the pad 9 and reflowed to form solder bumps 10. In this way, the wiring board 1 shown in FIG. 1 is manufactured.

1 is a schematic cross-sectional view of a wiring board 1 according to the present invention. The wiring board 1 (A) front view (B) back view. (A)-(E) It is a figure which shows the manufacturing method of the wiring board 1. FIG. (F)-(H) The figure following FIG. (I)-(K) The figure following FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wiring board 2 Metal foil 3 1st core insulating layer 4 2nd core insulating layer 5 Foil type core board 6 Through-hole 7a, 7b Through-hole conductor 8 Resin filler 9 Pad 10 Solder bump

Claims (4)

A foil-type core substrate including a metal foil, and a first core insulating layer and a second core insulating layer which are disposed on both main surfaces of the metal foil and are composed of a composite material in which a reinforced base material is impregnated with a synthetic resin; ,
A first wiring laminated portion and a second wiring formed by alternately laminating an insulating layer made of a non-composite material not containing a reinforced base material and a conductive layer made of a conductive material on both main surfaces of the core substrate A laminated part;
A wiring board comprising: The wiring board according to claim 1, wherein the foil-type core substrate has an overall thickness of 0.2 to 0.6 mm. A metal foil through hole formed in a predetermined position of the metal foil;
It is formed through the foil-type core substrate, electrically connects the first wiring laminated portion and the second wiring laminated portion, and is located inside the metal foil through hole and insulated from the metal foil. Through-hole conductors,
The wiring board according to claim 1, further comprising: The wiring board according to claim 1, wherein the metal foil has a thickness of 25 to 100 μm.

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