Patent Grant
8669480
The present invention relates to a wiring board formed by combining at least two boards each having a different size mounting area, and a method of manufacturing such a wiring board.
Japanese Unexamined Patent Publication H5-152693 discloses technology to solve insufficient rigidity in a wiring board. The technology relates to a wiring board having a reinforced section formed by making an extended portion of a flexible substrate and folding the extended portion.
Further, technology to provide wiring structures with high flexibility is described, for example, in WO 05/029934. This publication discloses a printed wiring board having a first substrate and a second substrate laminated on the first substrate, where the contour of the second substrate is different from the contour of the first substrate. The entire content of each of H5-152693 and WO 05/029934 is incorporated herein by reference.
A first aspect of the invention relates to a wiring board including a first substrate, a second substrate having a smaller mounting area than that of the first substrate; and a base substrate laminated between the first substrate and the second substrate such that the first substrate extends beyond an edge of the second substrate. An IVH (Interstitial Via Hole) penetrates the base substrate and vias are formed in at least one of the first substrate or the second substrate.
Another aspect of the invention relates to a method of manufacturing a wiring board including forming a base substrate, forming a first insulation layer on a first surface and of the base substrate and a second insulating layer on a second surface of the substrate opposing the first surface. Also included is forming an IVH (Interstitial Via Hole) that penetrates the base substrate, and forming vias in at least one of the first substrate or second substrate. Also included is cutting the first insulating layer in a first area and cutting the second insulating layer in a second area offset from said first area to form a first substrate laminated to a second substrate with the base layer interposed therebetween, the second substrate having a smaller mounting area than that of the first substrate such that the first substrate extends beyond an edge of the second substrate.
In still another aspect of the invention relates to a wiring board including a first substrate, a second substrate having a smaller mounting area than that of the first substrate; and a base substrate laminated between the first substrate and the second substrate such that the first substrate extends beyond an edge of the second substrate. A through hole penetrates the base substrate and vias are formed in at least one of the first substrate or the second substrate.
A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
In the following, an embodiment of a wiring board according to a specific example of the present invention is described with reference to the drawings.
As shown in
As shown in
On the surfaces (mounting surfaces) of first substrate 1 and second substrate 2, connecting pads to connect electronic components are formed; on the surfaces (mounting surfaces) and inner surfaces of first substrate 1 and second substrate 2, wiring patterns to structure electrical circuits are formed.
On the mounting surfaces of first substrate 1 and second substrate 2, electronic components 7, 8 are placed and connected to connecting pads according to their requirements. Electronic components 7, 8 are connected with each other through connecting pads and wiring patterns.
Wiring board 19 is placed, for example, in the casing of a cell phone device. Under such circumstance, electronic component 7 placed in fewer-layer section 14 is structured, for example, with the keypad of a keyboard; and electronic component 8 placed in multi-layer section 13 is structured with an electronic chip, IC module, functional components and others. Also, in the step portion formed by multi-layer section 13 and fewer-layer section 14, for example, a thin-type battery is placed.
Next, a detailed structure of wiring board 19 having the above overall structure is described in reference to
Base substrate 3 is formed to be shorter than second substrate 2, and between first substrate 1 and second substrate 2, groove (hereinafter referred to as “interlayer groove section”) 11 is formed. Interlayer groove section 11 is an aperture. The groove may be filled with elastic material such as silicon gel and silicon oil, or viscous material or others. When wiring board 19 receives an impact from being dropped, the groove aperture or silicon gel or silicon oil that is filled in the interior portion of the groove cushions the impact as a shock-absorbing layer. Therefore, by being structured in this way, tolerance to impact from being dropped may be improved.
First substrate 1 has a structure of laminated multiple insulation layers (1a, 1b, 1c). Each insulation layer is made of epoxy resin or the like with a thickness approximately 10 μm-60 μm. On the upper surface of insulation layer (1a), between epoxy-resin layers (1a) and (1b), between insulation layers (1b) and (1c) and on the lower surface of insulation layer (1c), wiring patterns (111a, 111b, 111c, 111d) are each formed. Each wiring pattern (111a, 111b, 111c, 111d) electrically connects required portions inside the circuit substrate.
Second substrate 2 also has a structure of laminated multiple insulation layers (2a, 2b, 2c) made of epoxy resin or the like with a thickness approximately 10 μm-60 μm. On the lower surface of insulation layer (2a), between epoxy-resin layers (2a) and (2b), between insulation layers (2b) and (2c) and on the upper surface of insulation layer (2c), wiring patterns (211a, 211b, 211c, 211d) are each formed. Each wiring pattern (211a, 211b, 211c, 211d) electrically connects required portions inside the circuit substrate.
On the exposed portion of the lower surface of first substrate 1 and the exposed portion of the upper surface of the second substrate, adhesion prevention layers 12 as a protective insulation layer are formed. At the step portion created when laminating first substrate 1 and second substrate 2, conductive pattern (111d) is formed. Also, to the right of conductive pattern (111d) formed at the step portion, conductive pattern (111d) is formed as well.
Keypad 7 is placed on the conductive pattern formed on the surface of fewer-layer section 14. Further, using solder 9, electronic chip 8 is anchored and connected to wiring patterns and built-up vias 4 through connecting pads 10. For solder 9, Sn/Ag/Cu was used.
Moreover, through-hole 63 is formed, penetrating base substrate 3, further penetrating first substrate 1 and second substrate 2, and connecting wiring pattern (111a) of first substrate 1 and wiring pattern (211d) of second substrate 2. The inner surface of through-hole 63 is plated so as to electrically connect wiring patterns. The area enveloped by plated through-hole 63 may be filled with resin such as epoxy-resin. The term “through-hole” refers to an electrical connection between conductors using a hole or aperture. In general, a through hole may be referred to as a plated through-hole. A through-hole can provide a conductive connection between a conductor formed on one end of the through-hole to a conductor formed on the other end of the through-hole. For example, a through-hole can provide a conductive connection between outer layers of a multilayer printed circuit board and/or may provide conductive connection to or between inner circuits of a multilayer printed circuit board. In forming a through hole, a penetrating hole is first formed by drilling, and a conductor is formed in the penetrating hole by metal plating (such as copper plating). In addition to providing electrical connection as noted above, a through-hole can receive the terminal of an electronic part for insertion mounting and fixing the electronic part to a printed circuit board.
In first substrate 1 and second substrate 2, multiple built-up vias 4 are formed. Built-up vias 4 are structured by stacking vias 44 formed in each insulation layer (1a-1c, 2a-2c). Built-up vias 4 connect required portions of wiring patterns (111a-111d) and also connect required portions of wiring patterns (211a-211d). On the inner surface of each via 44 forming built-up via 4, a conductive layer made of plated copper or the like is formed. Thus, the term via, as used herein, means an opening formed in a substrate such as an insulating layer. As shown in
Wiring board 19 having the above structure, for example, transmits operational signals from keypad 7 to an IC chip through built-up vias 4, wiring patterns (111a-111d) and through-hole 63, and the signals are then processed at the IC chip. By doing so, varieties of signal processing may be conducted.
Also, as described above, wiring board 19 is structured with multi-layer section 13 and fewer-layer section 14 and has a step portion. And at the lower portion of fewer-layer section 14, a large-volume component such as a cell-phone battery may be placed.
Base substrate 3 is made of highly rigid material such as glass-epoxy resin. Multi-layer section 13, because of base substrate 3 placed there, is highly rigid compared with fewer-layer section 14. On the other hand, fewer-layer section 14 is relatively flexible compared with multi-layer section 13. Thus, it is possible to place electronic components on either sections 13 or 14 according to the reliability level they require.
Also, for example, when the electronic device is dropped and an impact or the like is exerted on wiring board 19, due to the relative flexibility of fewer-layer section 14 compared with multi-layer section 13, fewer-layer section 14 vibrates as shown by arrow 37 in
Also, built-up via 4 is structured as a stacked via made by laminating multiple vias 44. By making such a stacked interlayer connection structure, the wiring length may be shortened, and thus preferable for mounting electronic components requiring large amount of electricity.
Moreover, built-up via 4 has a certain degree of mobility. Therefore, for example, when the electronic device is dropped and an impact is exerted on wiring board 19, the impact may be absorbed at built-up via 4 through the movement of built-up via 4 as shown by arrows 38, 39 in
In addition, through-hole 63, which penetrates base substrate 3 and further penetrates first substrate 1 and second substrate 2, is formed and the inner surface of through-hole 63 is plated (or filled with resin). Thus, as shown in
Further, if solid material or the like is filled in interlayer groove portion 11, when the impact from being dropped is exerted on the wiring board, interlayer groove portion 11 cushions the impact as a shock-absorbing layer. Accordingly, when interlayer groove portion 11 is formed, by improving tolerance to impact from being dropped, the wiring connecting the electronic components mounted on the wiring board may seldom rupture.
Also, in certain circumstances, two wiring boards of the present invention may be combined and sold in such a way that each fewer-layer section 14 is closely placed to provide compact shipment of the boards as will be further discussed with respect to
In the following, a method of manufacturing wiring board 19 according to the present invention is described.
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In the First Embodiment, to interconnect wiring patterns in first substrate 1 and second substrate 2, through-hole 63 is formed. However, the present invention is not limited to such embodiment. For example, an Interstitial Via Hole (“IVH”) may be formed to connect conductive layers. As shown in
If a wiring board has IVH 64, as shown in
The method of manufacturing a wiring board according to the Second Embodiment is the same as the method of manufacturing a wiring board according to the First Embodiment in reference to
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Also, if solid material or the like is filled in opening 5, the filled solid material or the like may play a role in decreasing warping at the juncture of multi-layer section 13 and fewer-layer section 14 where the number of layers is reduced. Accordingly, at the juncture of multi-layer section 13 and fewer-layer section 14, cracks may be prevented. Furthermore, if opening 5 is filled, for example, with solid material such as resin, the filled solid material plays a role in protecting conductive pattern (111d) mounted on first substrate 1. Therefore, tolerance to corrosion on conductive pattern (111d) may be improved.
A method of manufacturing a wiring board according to the Third Embodiment is the same as the method of manufacturing a wiring board according to the First Embodiment in reference to
In the First Embodiment, base substrate 3 was made of glass-epoxy resin. However, as shown in
The base material made of resin-impregnated inorganic fiber is formed by setting a prepreg. Prepreg is made by impregnating glass-cloth of inorganic fiber with epoxy-resin, then preliminarily thermosetting the resin to advance the level of setting. Although the resin used to form prepreg is preferred to have low-flow characteristics, those having regular flow characteristics may be used as well. Also, the prepreg may be formed by reducing the amount of epoxy-resin impregnated in the glass-cloth of inorganic fiber.
As for the inorganic fiber, it is not limited to glass-cloth, but may include, for example, alumina fiber, carbon fiber (carbon fiber), silicon carbide fiber or silicon nitride fiber.
In the method of manufacturing a wiring board according to the Fourth Embodiment, referring to
In the above-described First Embodiment, base substrate 3 was made of glass-epoxy resin. First substrate 1 and second substrate 2 were made of epoxy resin. However, the combination of material for base substrate 3 and material for first substrate 1 and second substrate 2 is not limited to the above embodiment. As shown in
Inorganic filler composite resin may be made by combining silica filler or glass filler with epoxy resin. In addition to epoxy resin, or other than epoxy resin, polyimide, polycarbonate, polybutylene-telephtarate or polyacrylate may be used.
For silica filler, fused silica (SiO2) or crystalline silica (SiO2) may be used. Also, for glass filler, aluminum oxide (Al2O3), magnesium oxide (MgO), or boron nitride (BN), aluminum nitride (AlN) may be used. Furthermore, for inorganic filler, it is not limited to silica filler or glass filler, but antimony trioxide, antimony pentaxide or magnesium hydroxide may be used.
In the method of manufacturing a wiring board according to the Fifth Embodiment, referring to
In the above-described First Embodiment, base substrate 3 was made of glass-epoxy resin. And first substrate 1 and second substrate 2 were made of epoxy resin. However, the combination of material for base substrate 3 and material for first substrate 1 and second substrate 2 is not limited to the above embodiment. As shown in
The above-described inorganic material such as inorganic fiber or inorganic filler has small thermo-expansion rates and low coefficient of elasticity compared with resin of organic material. Therefore, when inorganic material such as inorganic fiber or inorganic filler is combined, alignment gaps between connecting lands may be reduced.
In the method of manufacturing a wiring board according to the Sixth Embodiment, referring to
In the Second Embodiment, between first substrate 1 and second substrate 2, IVH 64 was formed. In the Second Embodiment, on the top and bottom ends of IVH 64, vias 44 were formed. However, the configuration of IVH 64 is not limited to the above embodiment. As shown in
In a wiring board having IVH 64 which does not have vias on the top and bottom ends, when shearing force is exerted on the wiring board from a horizontal direction, the shearing force may be countered through an anchoring effect. Accordingly, when an electronic device such as a cell phone receives an impact from being dropped or the like, the wiring connecting electronic components mounted on the wiring board may seldom rupture.
Here, in the present invention, IVHs 64 include those not having vias on top and bottom ends, as well as those having such vias.
The method of manufacturing a wiring board according to the Second Embodiment is the same as the method of manufacturing a wiring board according to the First Embodiment in reference to
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In a wiring board according to the First Embodiment of the present invention, first substrate 1 and second substrate 2 are in a stratum structure having a rectangular outline. However, they are not limited to the above structure, but may be in a stratum structure having a circular, hexagonal or octagonal outline.
Also, in the First Embodiment, first substrate 1 and second substrate 2 are made of epoxy resin. However, first substrate 1 and second substrate 2 are not limited to such, but may be made of polyimide, polycarbonate, polybutylene-telephtarate or polyacrylate. In addition, if first substrate 1 and second substrate 2 are made of epoxy resin, naphthalene-type epoxy resin, dicyclo-penta-diene-type epoxy resin, biphenyle-type epoxy resin or bisphenole-type epoxy resin may be used.
In the First Embodiment, as solder 9, Sn/Ag/Cu was used. However, solder 9 is not limited to such; solder containing antimony, tin, lead, indium or copper may be used. Also, eutectic crystal metals such as Sn/Sb, Sn/Ag, Sn/Pb or Sb/Cu may be used as well. Among such eutectic crystal metals, to avoid having a bad influence on the substrates, using metals having relatively low melting temperatures, 250° C. or lower, is preferred.
In the First Embodiment, interlayer groove portion 11 is filled with silicon gel of viscous silicon. However, filling interlayer groove portion 11 is not limited to such, but solid material may be used. As for the solid material to be filled in interlayer groove portion 11, high-polymer rubber is preferred as a solid material having viscosity and elasticity. Specifically, butyl-rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber or ethylene-propylene rubber may be used. Moreover, interlayer groove portion 11 may be filled with a gas. As the gas to be filled in interlayer groove portion 11, a rare gas such as argon, or nitrogen or oxygen may also be used.
In the Second Embodiment, in opening 5, silicon gel of viscous silicon is filled. However, the material to be filled in opening 5 is not limited to such, but solid material may be used. As solid material to be filled in opening 5, high-polymer rubber as a solid material having viscosity and elasticity is preferred. Specifically, butyl-rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber or ethylene-propylene rubber may be used. As the material to be filled in opening 5, a liquid or solid material is preferred, but a gas may be used. In such a case, as the gas to be filled in opening 5, a rare gas such as argon, or nitrogen or oxygen may be used.
In addition, first substrate 1 may not need to be formed single-layered, but may be formed multi-layered. Namely, first substrate 1 may be structured with a lower-layer insulation layer and an upper-layer insulation layer. Here, a lower-layer insulation layer indicates the insulation layer formed close to base substrate 3; and an upper-layer insulation layer indicates an insulation layer formed on the outer surface of the wiring board. Furthermore, first substrate 1 may be structured with a lower-layer insulation layer, an upper-layer insulation layer and an intermediate insulation layer placed in between. The intermediate insulation layer may be made multi-layered. In the First Embodiment, the lower-layer insulation layer corresponds to epoxy-resin layer (1c), the intermediate insulation layer corresponds to epoxy-resin layer (1b) and the upper-layer insulation layer corresponds to epoxy-resin layer (1a).
Also, the second substrate may not need to be formed single-layered, but may be formed multi-layered. Second substrate 2 may also be structured with a lower-layer insulation layer and an upper-layer insulation layer. Furthermore, second substrate 2 may be structured with a lower-layer insulation layer, an upper-layer insulation layer and an intermediate insulation layer placed in between. In the First Embodiment, the lower-layer insulation layer corresponds to epoxy-resin layer (2a), the intermediate insulation layer corresponds to epoxy-resin layer (2b) and the upper-layer insulation layer corresponds to epoxy-resin layer (2c). On top of the upper-layer insulation layer and lower-layer insulation layer, conductive patterns are formed. And, those conductive patterns may be connected with each other through vias 44.
The present invention may be employed in a wiring board which can mount electronic components, specifically, in a wiring board which can mount electronic components for compact electronic devices.
Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
This application claims the benefit of U.S. Provisional Application Ser. No. 60/938,597, filed May 17, 2007, the entire content of which is incorporated herein by reference.
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