JP2003198091A - Circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board having a capacitor layer not having uneven ness in permittivity by preventing the efficiency from decreasing due to reductions in size and thickness of an insulation sheet. <P>SOLUTION: The circuit board 100 comprises an insulation layer 1 and conductor layers 2, 3 on both surfaces of the layer 1 to constitute the capacitor layer. The layer 1 contains a nonwoven glass fiber in an epoxy resin. Further, the layer 1 is obtained by compressing glass paper 1 having a thickness of 150 μm or more to a thickness of 100 μm or less. The anchoring surfaces of the layers 2, 3 are opposed. Thus, the workability of a manual work in the manufacturing steps and an electrostatic capacity of a large capacitance per unit area as the board 100 are made compatible. Since the layer 1 contains the nonwoven fiber not having stitches, the unevenness of the permittivity is small, and its breakdown voltage is high. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a wiring board formed by laminating a conductor layer and an insulating layer. More specifically, the present invention relates to a wiring board having an interlayer capacitor structure using a conductor layer and an interlayer insulating layer.

[0002]

2. Description of the Related Art In recent years, the thickness of each layer of a laminated wiring board has become extremely thin due to a demand for thinning and weight reduction of the laminated wiring board. Lighter materials are used for each layer. In addition, the laminated wiring board has an inter-layer capacitor structure (hereinafter, referred to as an insulating layer and a conductor layer on both sides sandwiching the insulating layer).
"Capacitor layer". ) Has a part that constitutes. As a technology related to this capacitor layer, there is Japanese Patent No. 2738590. Further, in this capacitor layer, it is necessary to particularly thin the insulating layer in order to obtain a larger capacitance.

[0003]

However, the above-mentioned conventional wiring board has the following problems. That is, the thickness of the prepreg forming the insulating layer in the capacitor layer is reduced to 100 μm or less. Therefore, it is difficult to handle the wiring board during the manufacturing process. In particular, it is difficult to carry out manual work such as holding by hand.

Further, a normal prepreg is, as shown in FIG. 6, a glass cloth of a reinforcing material impregnated with a thermosetting resin. Therefore, we have stitches everywhere,
There are a high density portion and a low density portion of the glass. As a result, the workability differs between the part with the stitches and the part without the stitches at the time of drilling, and as a result, it is difficult to uniformly drill with a laser or the like. In addition, there are some variations in the dielectric constant of the entire capacitor layer.

Further, when a thin prepreg is sandwiched between the anchor surfaces of the conductor foil, there is a fear of dielectric breakdown due to irregularities such as stitches in the glass cloth. That is, when the convex portion of the anchor surface is in the gap between the stitches of the glass cloth, it may be too close to another conductor foil. In order to prevent this, it is essential that the thin prepreg used as the insulating layer of the capacitor layer be sandwiched between the flat surfaces of the conductor foil as shown in FIG. As a result, the prepreg and the conductor foil were laminated directly on the capacitor layer.
It is difficult to form a capacitor layer having more than one conductor layer. This is because at least one surface of the conductor foil is the anchor surface. Therefore, in order to obtain a large capacitance, it is necessary to stack a plurality of capacitor layers inside the wiring board or to separately arrange a plurality of capacitor layers inside the wiring board. Therefore, the laminated wiring board cannot be made thin and lightweight.

The present invention has been made to solve the problems of the above-described conventional wiring board. That is, it is an object of the invention to provide a wiring board having a capacitor layer in which the work efficiency is prevented from decreasing due to the thinning and lightening of the insulating sheet and the dielectric constant does not vary.

[0007]

A wiring board made for the purpose of solving this problem is a wiring board in which an insulating layer and a conductor layer are laminated, and an interlayer capacitor including an insulating layer and conductor layers on both sides of the insulating layer. The insulating layer of the inter-layer capacitor portion has a non-woven fabric made of insulating fibers inside the resin. That is, since the non-woven fabric is included in the insulating layer, it is possible to make uniform holes with a laser or the like. In addition, there is little variation in dielectric constant and high withstand voltage. Furthermore, it is lighter in weight and has a higher glass transition point than general prepregs.

Another wiring board of the present invention is a wiring board in which an insulating layer and a conductor layer are laminated, and which has an interlayer capacitor portion formed by the insulating layer and conductor layers on both sides of the insulating layer. The insulating layer is obtained by compressing an insulating film having a thickness of 150 μm or more to a thickness of 100 μm or less by pressing. As a result, since the thickness of the insulating film is 150 μm or more, the workability by hand in the manufacturing process is good. Moreover, since the thickness of the insulating layer is 100 μm or less, a large capacitance per area can be secured. The insulating film before pressing is 150 μm to 2 μm.
Those having a thickness in the range of 20 μm are used, and generally the thickness is in the range of 180 μm to 220 μm. The insulating layer after pressing is approximately 40 μm to 1
Used in thicknesses within the range of 00μm, typically 40μ
The thickness is in the range of m to 50 μm.

The insulating layer in the interlayer capacitor portion preferably has a ratio of the coefficient of thermal expansion in the thickness direction to the coefficient of thermal expansion in the in-plane direction within 1.5. As a result, the isotropy with respect to thermal expansion is relatively good, and distortion due to thermal history is small. Either of the coefficient of thermal expansion in the thickness direction and the coefficient of thermal expansion in the in-plane direction may be larger.

Further, at least one of the conductor layers of the interlayer capacitor portion may face the other conductor layer on the anchor surface. As a result, a wiring board can be manufactured without considering the surface properties of the conductor layer. Further, it is possible to form a constituent portion having three or more conductor layers in which an insulating layer and a conductor layer are laminated on the upper layer of the constituent portion. Therefore, the large-capacity capacitor layer can be formed inexpensively, thinly and lightly.

Further, the second conductor layer from the surface layer, the third conductor layer, and the insulating layer between them may form an interlayer capacitor portion. As a result, the wiring distance between the mounted component and the capacitor is short, and the wiring inductance is small.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments embodying the present invention will be described in detail below with reference to the accompanying drawings.

[First embodiment] Wiring board 1 according to the first embodiment
00 has the sectional structure shown in FIG. Specifically, wiring board 100 is a five-layer wiring board having conductor layers 2, 3, 7, 8, 9 and insulating layers 1, 4, 5, 6. The wiring board 100 has a capacitance between the conductor layers 2 and 3 with the insulating layer 1 interposed therebetween. That is, the conductor layer 2, the insulating layer 1, and the conductor layer 3 form a capacitor layer by using the conductor layer 2 as a ground layer and the conductor layer 3 as a power supply layer. In addition, the conductor layers 2 and 3 have their anchor surfaces adhered to the insulating layer 1. Although the anchor surfaces of the conductor layers 2 and 3 face each other in FIG. 1, the invention is not limited to this. The flat surfaces may face each other. Also, one flat surface and the other anchor surface may face each other. That is, the orientation of the conductor layer does not matter.

The conductor layers 2, 3, 7, 8 and 9 are conductors such as copper foil. The thickness of the conductor layers 2 and 3 is in the range of 5 μm to 35 μm. On the other hand, the insulating layer 1 is an insulator in which a glass non-woven fabric is contained inside the epoxy resin. The thickness of the insulating layer 1 is in the range of 40 μm to 50 μm. It is assumed that the conductor layers 7, 8 and 9 are appropriately patterned. The insulating layers 4, 5 and 6 may be the same base material as the insulating layer 1 or may be a normal base material such as prepreg.

Next, the manufacturing process of the capacitor layer in the wiring board 100 will be described. As shown in FIG. 2, the capacitor layer uses copper foils 2 and 3 and glass paper 1 as starting materials. First, as the starting materials, the respective materials are arranged in the order of the copper foil 2, the glass paper 1, and the copper foil 3. Further, the copper foils 2 and 3 are arranged so that the anchor surface faces the glass paper 1. However, as mentioned above, this is not essential. The copper foils 2 and 3 correspond to the conductor layers 2 and 3 in FIG. The glass paper 1 corresponds to the insulating layer 1 in FIG.

This glass paper 1 is not a woven glass cloth impregnated with an epoxy resin as shown in FIG. 6, but a glass nonwoven fabric impregnated with an epoxy resin. That is, there are no irregularities such as stitches on the surface of the glass paper 1, and the glass paper 1 has good flatness. For this reason,
There is no risk of dielectric breakdown even if it is bonded to the copper foil anchor surface.
Furthermore, the epoxy resin of the glass paper 1 has a sponge shape, and has minute bubbles everywhere. The thickness of the glass paper 1 is 180 μm to 22 μm.
Within the range of 0 μm. In other words, it is several times thicker than the prepregs used so far. Therefore, manual workability is good. Specifically, since it has a sufficient thickness, it is easy to hold one by one. Furthermore, there is little concern that the glass paper 1 itself will bend.

The specific gravity of the glass paper 1 is 1.
It is within the range of 6 to 1.7. Therefore, it is lighter in weight than a general prepreg (specific gravity 1.9 to 2.0).
This weight reduction is very important for mobile products such as mobile phones.

The thermal expansion coefficient of the glass paper 1 is 30 to 40 ppm / ° C in the in-plane direction and 40 to 50 ppm / ° C in the thickness direction. The relative permittivity of the glass paper 1 is 4.10 at 1 MHz and 3.95 at 1 GHz. The dielectric loss tangent is 0.0 at 1MHz.
It is 0.0116 at 043,1 GHz. The glass paper 1 is, for example, GEA- manufactured by Hitachi Chemical Co., Ltd.
679P or AS-5000GP can be used.

Next, vacuum pressing is performed on the glass paper 1 and the like arranged as shown in FIG. The glass paper 1 etc. after pressing becomes a capacitor layer as shown in FIG. By this press, the bubbles in the glass paper 1 are closed by the epoxy resin. As a result, the glass paper 1 becomes a substantially uniform insulating layer as a whole. Furthermore, since the glass paper 1 is a non-woven fabric, it has no stitches. Therefore, it is possible to make a uniform hole with a laser or the like. Further, the thickness of the glass paper 1 becomes thin, and a large capacitance per area can be secured. Further, the insulating layers 4, 5, and 5 are further added to the manufactured capacitor layer.
Wiring board 100 is manufactured by laminating 6 and conductor layers 7, 8 and 9 and patterning them.

As described in detail above, in the wiring board 100 of the first embodiment, the glass paper 1 which is the insulating layer and the copper foils 2 and 3 which are the conductor layers on both surfaces thereof constitute the capacitor layer. . Further, the insulating layer 1 is made by incorporating a glass nonwoven fabric inside the epoxy resin. In addition, the insulating layer 1 was formed from the glass paper 1 having a thickness within the range of 180 μm to 220 μm by 40 μm to 5 μm.
It is supposed to be compressed to a thickness within the range of 0 μm. That is, the glass paper 1 having a thickness of 150 μm or more is compressed by a press to a thickness of 100 μm or less. As a result, both the workability of the manual work in the manufacturing process and the large capacitance per area of the wiring board 100 are compatible. In addition, since the insulating layer 1 includes a non-woven fabric, the variation in dielectric constant is small and the withstand voltage is high. Therefore, it is possible to realize a wiring board having a capacitor layer in which the work efficiency is prevented from being reduced due to the thinning and lightening of the insulating sheet, and the dielectric constant does not vary.

The thermal expansion coefficient of the glass paper 1 in the thickness direction is as small as 40 to 50 ppm / ° C.
Therefore, there is little change in capacitance due to thermal expansion, and stable capacitance is obtained. Further, since the coefficient of thermal expansion in the in-plane direction is 30 to 40 ppm / ° C., the isotropic property regarding thermal expansion is better than that of a general prepreg and the like, and the strain when subjected to thermal history is small.

[Second Mode] Wiring board 2 according to the second mode
00 has the sectional structure shown in FIG. Specifically, the wiring board 200 includes the conductor layers 13, 14, 15, 18,
A five-layer wiring board having 19 and insulating layers 11, 12, 16, and 17.

The insulating layers 11 and 12 are made of the same material as the glass paper 1 according to the first embodiment. In other words, there is no risk of dielectric breakdown even if it adheres to the anchor surface of the conductor layer. In addition, the conductor layers 13 and 15 are the power source layer and the conductor layer 1
4 is used as a ground layer. As a result, the wiring board 200 includes the conductor layers 13, 1 with the insulating layer 11 interposed therebetween.
It has a capacitance between four. In addition, the capacitance is also provided between the conductor layers 14 and 15 that sandwich the insulating layer 12. That is, the wiring member 200 has a large-capacity capacitor layer in which the capacitance between the conductor layers 13 and 14 and the capacitance between the conductor layers 14 and 15 are superposed.

As described in detail above, the wiring board 200 of the second embodiment has the capacitor layer composed of the conductor layers 13, 14 and 15. The insulating layers 11 and 12 of the wiring board 200 include glass non-woven fabric, and there is no fear of dielectric breakdown even if they are adhered to the anchor surfaces of the conductor layers 13, 14 and 15. Therefore, the wiring board 200 has a large-capacity capacitor layer in which the capacitor layer including the conductor layer 13, the insulating layer 11, and the conductor layer 14 and the capacitor layer including the conductor layer 14, the insulating layer 12, and the conductor layer 15 are stacked. Available as As a result, a large-capacity capacitor layer is realized without using a plurality of capacitor layers. Therefore, the laminated wiring board can be made thin and lightweight, and the cost can be suppressed.

[Third Mode] In the wiring board according to the second mode, the capacitor layer is arranged in the core portion of the wiring board, but the present invention is not limited to this. Wiring board 300 according to the third embodiment has a sectional structure shown in FIG.
Specifically, the wiring board 300 includes the conductor layers 23, 24, 2
5, 28 and insulating layers 21, 22, 26, 27. The insulating layers 21 and 22 are made of the same base material as the glass paper 1 according to the first embodiment. In addition, the conductor layer 25 is used as a power layer and the conductor layer 24 is used as a ground layer. As a result, the wiring board 300 has a capacitance between the conductor layers 24 and 25 that sandwich the insulating layer 22. That is, the conductor layers 24, 2
A capacitor layer is formed between the five.

The conductor layer 23, which is the surface layer, is appropriately patterned. Further, the wiring board 300 has vias 30 formed from the surface layer by a laser or the like. This via 30 is an ordinary skip via (hole diameter: 10
In addition to 0 μm to 250 μm, micro vias (hole diameter: 75
μm to 150 μm).

As described in detail above, the wiring board 300 of the third embodiment has the insulating layer 21 immediately below the surface conductor layer 23. Since this insulating layer 21 includes a non-woven fabric, it does not have stitches and the density of the glass is not biased. Therefore, it is possible to form a good via having no variation in shape and hole diameter. Further, the wiring distance between the mounted component and the capacitor is short, and the wiring inductance can be small.

The present embodiment is merely an example and does not limit the present invention. Therefore, naturally, the present invention can be variously improved and modified without departing from the gist thereof. For example, in the second embodiment, a capacitor layer having three conductor layers is used, but the present invention is not limited to this. That is, four or more conductor layers may be used as the capacitor layer.

Further, the bubbles of the glass paper may contain powder of a ferroelectric substance such as barium titanate. Further, the powder of the ferroelectric substance may be dispersed in the epoxy resin. As a result, the wiring board has a more uniform and large-capacity capacitor layer.

[0030]

As is apparent from the above description, according to the present invention, there is provided a wiring board having a capacitor layer which prevents a decrease in work efficiency due to a reduction in thickness and weight of an insulating sheet and has a uniform dielectric constant. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a wiring board according to a first embodiment.

FIG. 2 is a conceptual diagram showing an arrangement of components for manufacturing the wiring board according to the first embodiment.

FIG. 3 is a cross-sectional view showing a capacitor layer in the first mode.

FIG. 4 is a sectional view showing a wiring board according to a second embodiment.

FIG. 5 is a sectional view showing a wiring board according to a third embodiment.

FIG. 6 is a diagram showing a prepreg in a conventional form.

FIG. 7 is an enlarged cross-sectional view of a bonding surface of a wiring board in a conventional form.

[Explanation of symbols]

1 Insulation layer (glass paper) 2 Conductor layer (copper foil) 3 conductor layers (copper foil) 30 vias 100 wiring board

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4E351 AA03 BB03 DD04 DD54 GG06                       GG20                 5E346 AA12 AA13 CC04 CC09 FF45                       HH22

Claims (5)

[Claims] 1. A wiring board in which an insulating layer and a conductor layer are laminated, has an interlayer capacitor portion formed by the insulating layer and conductor layers on both sides thereof, and the insulating layer of the interlayer capacitor portion is insulated inside a resin. A wiring board comprising a non-woven fabric made of a flexible fiber. 2. A wiring board in which an insulating layer and a conductor layer are laminated, having an interlayer capacitor portion formed by the insulating layer and conductor layers on both sides thereof, and the insulating layer of the interlayer capacitor portion has a thickness of 150 μm or more. A wiring board, which is obtained by compressing the insulating film of 1. to a thickness of 100 μm or less by pressing. 3. The wiring board according to claim 1 or 2, wherein the insulating layer of the interlayer capacitor portion has a ratio of the thermal expansion coefficient in the thickness direction to the thermal expansion coefficient in the in-plane direction of 1.
A wiring board characterized by being within 5. 4. The wiring board according to at least one of claims 1 to 3, wherein at least one of the conductor layers of the interlayer capacitor portion faces the other conductor layer at an anchor surface. And a wiring board. 5. The wiring board according to at least one of claims 1 to 4, wherein the second conductor layer from the surface layer, the third conductor layer, and the insulating layer between them are provided. A wiring board comprising the interlayer capacitor portion.