JP2004179171A - Wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board which is hardly warped when semiconductor elements are mounted on it and superior in rigidity, wherein through-holes uniform in diameter can be formed by fine laser processing, and solder bumps are hardly damaged when semiconductor elements are mounted on the board. <P>SOLUTION: The wiring board is formed through such a manner that warp threads 1a and weft threads 1b are woven into a glass cloth 1, a plurality of glass cloths 1 are stacked up into the laminated glass cloths 1, the laminated glass cloths 1 are impregnated with thermosetting resin 2 for the formation of an insulating layer 3, a wiring conductor 4 is provided on the top surface and undersurface of the insulating layer 3, and the wiring conductors 4 sandwiching the insulating layer 3 between them are electrically connected together through the through-hole 6 bored in the insulating layer 3 for the formation of the wiring board. In the glass cloth 1, the total area of the openings 7b of gaps 7a surrounded with the warp threads 1a and the weft threads 1b amounts to 0.10 to 2% of the area of the glass cloth 1, and the glass cloths 1 are stacked up so as not to make the openings 7b overlap each other in the vertical direction. <P>COPYRIGHT: (C)2004,JPO

Description

【００５１】
表１に示すように、ガラスクロス１の開口７ｂの全面積の比率が0.01％未満の場合（試料No.１）、絶縁層３の絶縁抵抗値が10¹³Ω未満となり絶縁性が低下することがわかった。また、２％より大きい場合（試料No.６）、均一な径の貫通孔が形成できず、貫通導体５の導通抵抗が10ｍΩ以上と高くなることがわかった。それに対して、ガラスクロス１の開口７ｂの全面積の比率を0.01〜２％の場合（試料No.２〜５）、絶縁層３の絶縁抵抗値が10¹³Ω以上、貫通導体５の導通抵抗が10ｍΩ未満となり絶縁抵抗性に優れ、導通抵抗が低い配線基板となることがわかった。
【００５２】
また、ガラスクロス１を上側の縦糸１ａの軸方向と下側の縦糸１ａの軸方向とのなす角度が０〜90度となるように積層して、上記と同様にして試料を製作した。次に、配線基板の実装電極11ａ上に半田バンプを形成し、その半田バンプを介して上面に半導体素子を実装した。実装後の半導体素子と配線基板との剥れの有無を超音波探傷機で測定した。また別途、絶縁層３のみを加熱プレスして絶縁層３の縦糸１ａの軸方向とこれと45度をなす方向の弾性率を測定した。その結果を表２に示す。
【００５３】
【表２】

【００５４】
表２に示すように、上側の縦糸１ａの軸方向と下側の縦糸１ａの軸方向とのなす角度が15度未満および75度を超えた場合（試料No.７、８、14、15）、絶縁層３の縦糸方向とその45度方向の弾性率の差が20％以上と大きな値となることがわかった。それに対して、上側の縦糸１ａの軸方向と下側の縦糸１ａの軸方向とのなす角度が15〜75度の場合（試料No.９〜13）、絶縁層３の縦糸方向１ａとその45度方向の弾性率の差が10％以下と小さな値となることがわかった。
【００５５】
【発明の効果】
本発明の配線基板によれば、ガラスクロスを複数積層するとともにこの積層したガラスクロスに熱硬化性樹脂を含浸させて成る絶縁層の上下面に配線導体を形成し、絶縁層を挟んで上下に位置する配線導体同士を絶縁層に設けた貫通導体を介して電気的に接続して成ることから、絶縁層の厚みが厚い場合においてもガラスクロスを構成する撚糸の径を大きなものとする必要はなく、その結果、ガラスクロスの隙間の開口の全面積が大きくなることはなく、撚糸の密な部分と疎な部分との疎密差が大きなものとなることはない。
【００５６】
また、ガラスクロスの隙間の開口の全面積がガラスクロスの面積の0.01〜２％であり、かつ開口が上下に重ならないように積層されていることから、撚糸の密な部分と疎な部分との疎密差がより小さなものとなり、配線基板にレーザを用いて貫通孔を穿孔する際、均一な内部径や出射径を有する貫通孔を穿孔することができ、貫通孔に導電性材料を充填して貫通導体を形成した場合に、貫通導体の抵抗が部分的に高くなったり、断線してしまうということはない。
【００５７】
さらに、絶縁層はガラスクロスを複数積層するとともにこの積層したガラスクロスに熱硬化性樹脂を含浸させたて成ることから、絶縁層が薄い場合でも複数のガラスクロスを積層したほうが絶縁層の剛性の低下を減少させることができ、その結果、大型のＬＳＩ等の半導体素子を配線基板に実装した際、半導体素子の動作時に半導体素子と配線基板との熱膨張係数の相違に起因して大きな応力が発生しても、半導体素子が配線基板から剥がれてしまう、あるいは半導体素子が破壊されてしまうことはない。
【００５８】
本発明の配線基板によれば、ガラスクロスの縦糸および横糸の軸方向の弾性率と、縦糸および横糸の交点間を結ぶ方向の弾性率との差が大きいが、積層したガラスクロスのうち上下に接するものは、上側の縦糸の軸方向と下側の縦糸の軸方向とのなす角度を15〜75度となるように積層した場合には、絶縁層の方向毎の弾性率の差異を小さくすることでき、その結果、配線基板に大型のＬＳＩ等の半導体素子を実装した時に発生する応力による配線基板の変形を抑制でき、半導体素子が配線基板から剥がれてしまう、あるいは半導体素子が破壊されてしまうということを有効に防止することができる。
【図面の簡単な説明】
【図１】本発明の配線基板の実施の形態の一例を示す断面図である。
【図２】図１に示すガラスクロスの平面図である。
【符号の説明】
１・・・・・・・ガラスクロス
１ａ・・・・・縦糸
１ｂ・・・・・横糸
２・・・・・・・熱硬化性樹脂
３・・・・・・・絶縁層
４・・・・・・・配線導体
５・・・・・・・貫通孔
６・・・・・・・貫通導体
７ａ・・・・・・隙間
７ｂ・・・・・・開口[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wiring board for mounting electronic components such as a semiconductor element and a resistor.
[0002]
[Prior art]
Conventionally, as a wiring board used to mount electronic components such as semiconductor elements and resistors, a glass cloth formed by weaving a warp yarn and a weft yarn, which are twisted yarns, in such a manner that the angle between both the axial directions is a right angle direction. 2. Description of the Related Art There is known a printed circuit board formed by alternately laminating a plurality of insulating layers impregnated with a curable resin and wiring conductors formed of a copper foil. In such a printed circuit board, first, a copper foil adhered on the surface of the insulating layer is etched to form a wiring conductor of a predetermined pattern, and then the insulating layer on which the wiring conductor is formed is coated with an adhesive made of a thermosetting resin. A multilayer board is manufactured by laminating and pressing multiple sheets in between, and then a drill is used to form a through hole that penetrates the front and back of the multilayer board, and then copper plating is applied to the inner surface of the through hole and vertically It is manufactured by forming through-hole conductors that electrically connect the wiring conductors located.
[0003]
Normally, each insulating layer is formed by impregnating a thermosetting resin into one glass cloth, and by selecting twisted yarns of various diameters, a glass cloth having a desired thickness is obtained and the thermosetting resin is added thereto. Impregnation results in a desired thickness.
[0004]
2. Description of the Related Art In recent years, in electronic devices, semiconductor elements have been highly integrated year by year with the increase in density, and the demand for higher density of wiring conductors on a wiring board on which the semiconductor elements are mounted has been increasing. However, the above-described printed circuit board has a problem that it is difficult to improve the density of wiring conductors because the printed circuit board has a through-hole structure that penetrates the front and back sides of the laminated board.
[0005]
In order to solve such a problem, an inner via hole structure in which a through hole is formed in each insulating layer instead of a through hole structure, and a conductor is filled in the through hole and the upper and lower wiring conductors are connected to each other. Has been put to practical use. In such an inner via hole structure, the diameter of the through hole is required to be fine processing of 200 μm or less, and it is difficult to drill a small diameter of 200 μm or less with a drill. Therefore, it is generally performed to drill the through hole with a laser. .
[0006]
However, the glass cloth constituting the insulating layer has a structure in which twisted yarns are woven vertically and horizontally, and when the glass cloth is viewed from above, the portion where the vertical and horizontal twisted yarns overlap, and either one of them A portion where a twisted yarn exists and a portion where no twisted yarn exists, that is, three types of gaps surrounded by vertical and horizontal twisted yarns are mixed, and the entire area of the opening of the gap is the area of the glass cloth. When a laser is used to penetrate through holes in an insulating layer formed by impregnating such a glass cloth with a thermosetting resin, vertical and horizontal twisted yarns are overlapped. It is said that the inner diameter and the emission diameter of the through-hole are small in the dense part, and the inner diameter and the emission diameter of the through-hole are large in the gap where there is no twisted yarn, so that the through-hole having a uniform inner diameter and the emission diameter cannot be drilled. There was a problem.
[0007]
In order to solve such a problem, when manufacturing a substrate by laminating a plurality of insulating layers, the insulating layers are arranged so that the weave positions of the glass cloth included in each of the insulating layers located above and below are different from each other. Lamination has been proposed (see Patent Document 1).
[0008]
[Patent Document 1]
JP 2002-76548 A
[0009]
[Problems to be solved by the invention]
However, in the conventional glass cloth, the total area of the openings in the gap is 5 to 12% of the area of the glass cloth, which is a large ratio of the total area of the openings. Even if the weave positions are laminated so as to be different from each other, there are still dense parts and sparse parts of the twisted yarn, and when drilling through holes using a laser on the substrate, it has a uniform internal diameter and emission diameter It is difficult to form the through-hole, and when the through-hole is filled with a conductive material to form the through-conductor, there is a problem that the resistance of the through-hole conductor is partially increased or the through-hole is disconnected. Was.
[0010]
In addition, since each insulating layer is formed by impregnating one glass cloth with a thermosetting resin, when the thickness of the insulating layer is large, the diameter of the twisted yarn constituting the glass cloth becomes large, and the entire area of the opening is reduced. There is also a problem that as the size increases, the difference in density between the dense portion and the sparse portion of the twisted yarn becomes larger. Further, when the thickness of the insulating layer is thin, the rigidity of only one glass cloth is reduced, and when a semiconductor element such as a large-sized LSI is mounted on a wiring board, the semiconductor element and the wiring board are not connected during operation of the semiconductor element. There is also a problem that a large stress is generated due to the difference in thermal expansion coefficient of the semiconductor element, and the semiconductor element is peeled off from the wiring board or the semiconductor element is destroyed by the stress.
[0011]
The present invention has been completed in view of the problems of the prior art described above, and an object of the present invention is to form a through hole having a uniform diameter by laser processing on a high-density wiring board having fine through conductors. An object of the present invention is to provide a wiring board which is excellent in electrical connection reliability and in which a semiconductor element can be favorably mounted.
[0012]
[Means for Solving the Problems]
The wiring board according to the present invention is characterized in that a plurality of glass cloths woven by warp and weft are laminated, and the laminated glass cloths are impregnated with a thermosetting resin. The glass cloth is formed by electrically connecting wiring conductors located above and below each other through a through conductor provided in an insulating layer, and the entire area of the opening of the gap surrounded by the warp and the weft is equal to that of the glass cloth. The area is 0.01 to 2% of the area, and the openings are stacked so that the openings do not overlap vertically.
[0013]
According to the wiring board of the present invention, a plurality of glass cloths are laminated, and a wiring conductor is formed on the upper and lower surfaces of the insulating layer formed by impregnating the laminated glass cloth with a thermosetting resin, and the wiring conductors are vertically arranged with the insulating layer interposed therebetween. Since the located wiring conductors are electrically connected via the through conductor provided on the insulating layer, it is not necessary to increase the diameter of the twisted yarn constituting the glass cloth even when the thickness of the insulating layer is large. As a result, the entire area of the opening of the gap of the glass cloth does not increase, and the difference in density between the dense portion and the sparse portion of the twisted yarn does not increase.
[0014]
Further, the glass cloth has a total area of the opening of the gap of 0.01 to 2% of the area of the glass cloth, and is laminated so that the opening does not overlap with the upper and lower sides. The difference in density from the part becomes smaller, and when drilling a through hole using a laser on the wiring board, it is possible to drill a through hole having a uniform internal diameter and emission diameter, and to use a conductive material in the through hole. In the case where the through conductor is formed by filling, the resistance of the through conductor does not partially increase or break.
[0015]
Furthermore, since the insulating layer is formed by laminating a plurality of glass cloths and impregnating the laminated glass cloth with a thermosetting resin, even if the insulating layer is thin, the lamination of a plurality of glass cloths reduces the rigidity of the insulating layer. As a result, when a semiconductor device such as a large LSI is mounted on a wiring board, a large stress is generated due to a difference in thermal expansion coefficient between the semiconductor element and the wiring board during operation of the semiconductor element. However, the semiconductor element does not peel off from the wiring board or the semiconductor element is not destroyed.
[0016]
Further, in the wiring board of the present invention, in the above-mentioned configuration, an angle between an axial direction of the upper warp and an axial direction of the lower warp is 15 to 75, of the laminated glass cloths, which are vertically in contact with each other. It is characterized in that it is laminated so as to have different degrees.
[0017]
According to the wiring board of the present invention, the difference between the elastic modulus in the axial direction of the warp and the weft of the glass cloth and the elastic modulus in the direction connecting the intersections of the warp and the weft are large, In contact with, when laminated so that the angle between the axial direction of the upper warp and the axial direction of the lower warp is 15 to 75 degrees, the difference in elastic modulus for each direction of the insulating layer is reduced. As a result, the deformation of the wiring board due to the stress generated when a large-sized LSI or other semiconductor element is mounted on the wiring board can be suppressed, and the semiconductor element peels off from the wiring board or the semiconductor element is destroyed. This can be more effectively prevented.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the wiring board of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing an example of an embodiment of a wiring board of the present invention. FIG. 2 is a plan view of a glass cloth constituting the wiring board shown in FIG. The outline of the lower glass cloth is shown by a solid line so that the positional relationship with the above is clear. In these figures, 1 is a glass cloth, 2 is a thermosetting resin, 3 is an insulating layer, 4 is a wiring conductor, 5 is a through hole, 6 is a through conductor, 7a is a gap, and 7b is an opening.
[0019]
In the wiring board of the present invention, a plurality of glass cloths 1 made by weaving the warp yarns 1a and the weft yarns 1b so that their axial directions are substantially perpendicular to each other are laminated, and the laminated glass cloths 1 are impregnated with a thermosetting resin 2. A wiring conductor 4 is formed on the upper and lower surfaces of the insulating layer 3 made of, and the wiring conductors 4 positioned above and below the insulating layer 3 are electrically connected to each other via a through conductor 6 provided on the insulating layer 3. FIG. 1 shows an example of a laminated wiring board formed by laminating four such wiring boards.
[0020]
The insulating layer 3 has a thickness of 50 to 150 μm, and has a function of supporting the wiring conductors 4 and maintaining insulation between the wiring conductors 4 located above and below. It is formed by impregnating a thermosetting resin 2 such as a maleimide triazine resin or a modified polyphenylene ether resin. If the thickness of the insulating layer 3 is less than 50 μm, the rigidity of the wiring board is reduced, and the wiring board tends to be easily bent. If the thickness is more than 150 μm, the thickness of the insulating layer 3 becomes unnecessarily thick, and Lightening tends to be difficult. Therefore, the insulating layer 3 preferably has a thickness of 50 to 150 μm.
[0021]
The glass cloth 1 has a plain weave, a twill weave, a satin weave, and the like depending on the weaving method. FIG. 2 shows a plan view of a plain weave in which the warp and weft yarns 1a and 1b cross each other up and down. I have. The glass cloth 1 has a thickness of 10 to 50 μm, and if the thickness is less than 10 μm, the warp yarns 1a and the weft yarns 1b become extremely thin and it is difficult to weave them uniformly, so that the insulating layer 3 tends to warp after curing. If the thickness is more than 50 μm, the insulating layer 3 becomes unnecessarily thick, and it tends to be difficult to reduce the weight of the wiring board. Therefore, the thickness of the glass cloth 1 is preferably 10 to 50 μm.
[0022]
In the wiring board of the present invention, a plurality of glass cloths 1 are laminated, and a wiring conductor 4 is formed on the upper and lower surfaces of an insulating layer 3 obtained by impregnating the laminated glass cloth 1 with a thermosetting resin 2. The glass cloth 1 is formed by electrically connecting wiring conductors 4 positioned above and below each other via a through conductor 6 provided on the insulating layer 3, and the glass cloth 1 has an opening 7 b of a gap 7 a surrounded by the warp 1 a and the weft. Of the glass cloth 1 is 0.01 to 2% of the area of the glass cloth 1, and the openings 7b are stacked so that they do not overlap each other. In the present invention, the entire area of the opening 7b of the gap 7a of the glass cloth 1 is 0.01 to 2% of the area of the glass cloth 1, and the openings 7b are stacked so that they do not overlap vertically. is important.
[0023]
According to the wiring board of the present invention, a plurality of glass cloths 1 are laminated, and a wiring conductor 4 is formed on upper and lower surfaces of an insulating layer 3 formed by impregnating the laminated glass cloth 1 with a thermosetting resin 2. Since the wiring conductors 4 positioned above and below the insulating layer 3 are electrically connected to each other via the through conductors 6 provided on the insulating layer 1, the glass cloth 1 is formed even when the insulating layer 3 is thick. It is not necessary to increase the diameter of the warp yarn 1a or the weft yarn 1b of the twisted yarn to be formed. As a result, the entire area of the opening 7b of the gap 7a of the glass cloth 1 does not increase, and the dense portion and the sparse portion of the twisted yarn are not increased. The difference between density and density does not become large.
[0024]
In addition, since the entire area of the opening 7b of the gap 7a of the glass cloth 1 is 0.01 to 2% of the area of the glass cloth 1 and the openings 7b are stacked so as not to overlap vertically, the dense portion of the twisted yarn The difference in density between the sparse portion and the sparse portion becomes smaller, and when the through hole 5 is drilled using a laser on the wiring board, the through hole 5 having a uniform inner diameter or emission diameter can be drilled. When the through-conductor 6 is formed by filling the conductive material 5 with the conductive material, there is no possibility that the resistance of the through-conductor 6 is partially increased or the wire is disconnected.
[0025]
Furthermore, since the insulating layer 3 is formed by laminating a plurality of glass cloths 1 and impregnating the laminated glass cloth 1 with a thermosetting resin 2, even when the insulating layer 3 is thin, the plurality of glass cloths 1 are laminated. When the semiconductor element (not shown) such as a large-sized LSI is mounted on the wiring board, the rigidity of the insulating layer 3 can be reduced. Even if a large stress is generated due to the difference in the thermal expansion coefficient, the semiconductor element does not peel off from the wiring board or the semiconductor element is not broken.
[0026]
If the entire area of the opening 7b of the gap 7a in the glass cloth 1 is smaller than 0.01% of the area of the glass cloth 1, the glass cloth 1 cannot be impregnated with the thermosetting resin 2 satisfactorily, and the insulating property of the insulating layer 3 decreases. If it exceeds 2%, the probability of piercing the through hole 5 in the gap 7a increases, and it tends to be difficult to pierce the through hole 5 having a uniform diameter. Therefore, it is important that the entire area of the opening 7b of the gap 7a of the glass cloth 1 be 0.01 to 2% of the area of the glass cloth 1.
[0027]
The entire area of the opening 7b is reduced by flattening the glass cloth 1 by a high-pressure water flow treatment, a pressure treatment with a roll, or the like, so that the entire area of the opening 7b of the gap 7a in the glass cloth 1 is equal to the area of the glass cloth 1. It is adjusted to be 0.01 to 2%.
[0028]
The surface of the glass cloth 1 has been subjected to a silane coupling treatment in order to improve the adhesion to the thermosetting resin 2. Further, these glass cloths 1 are usually made of glass called E glass, but may be made of D glass, S glass or high dielectric constant glass.
[0029]
Further, in the wiring board of the present invention, it is preferable that the glass cloths 1 are laminated so that the angle between the axial direction of the upper warp and the axial direction of the lower warp is 15 to 75 degrees.
[0030]
According to the wiring board of the present invention, the difference between the elastic modulus in the axial direction of the warp 1a and the weft 1b of the glass cloth 1 and the elastic modulus in the direction connecting the intersections of the warp 1a and the weft 1b is large. Are laminated so that the angle between the axial direction of the upper warp 1a and the axial direction of the lower warp 1a is 15 to 75 degrees, so that the difference in the elastic modulus in the direction of the insulating layer 3 is reduced. As a result, the deformation of the wiring board due to the stress generated when a large-sized LSI or other semiconductor element is mounted on the wiring board can be suppressed, and the semiconductor element peels off from the wiring board or the semiconductor element is destroyed. This can be effectively prevented.
[0031]
If the angle between the axial direction of the upper warp 1a and the axial direction of the lower warp 1a is less than 15 degrees or more than 75 degrees, the axial direction of the warp 1a and the weft 1b of the glass cloth 1 and the oblique direction thereof The difference in elastic modulus of the wiring board becomes large, and the wiring board is deformed by the stress generated when a large-sized LSI or other semiconductor element is mounted on the wiring board, and the semiconductor element is peeled off from the wiring board or the semiconductor element is broken. There is a tendency for the danger of becoming large. Therefore, it is preferable that the angle between the axial direction of the upper warp and the axial direction of the lower warp be in the range of 15 to 75 degrees.
[0032]
In addition, as the thermosetting resin 2 forming the insulating layer 3, a thermosetting resin 2 such as an epoxy resin, a bismaleimide triazine resin, and a modified polyphenylene ether resin that cures at a temperature of 150 to 200 ° C. is used. In order to favorably impregnate the thermosetting resin 2 into the glass cloth 1, a surfactant or an inorganic filler may be added.
[0033]
Further, a wiring conductor 4 is embedded in the surface of the insulating layer 3. The wiring conductor 4 has a function as a part of a conductive path for electrically connecting each electrode of an electronic component such as a semiconductor element mounted on the wiring board to an external electric circuit board (not shown), and has a width. It has a thickness of 20 to 200 μm and a thickness of 5 to 50 μm, and is made of a metal foil such as copper, aluminum, nickel, silver, or gold, and is preferably made of a copper foil from the viewpoint of workability and low cost. If the width of the wiring conductor 4 is less than 20 μm, deformation and disconnection of the wiring conductor 4 tend to occur, and if it exceeds 200 μm, high-density wiring tends not to be formed. Further, when the thickness of the wiring conductor 4 is less than 5 μm, the strength of the wiring conductor 4 tends to decrease and deformation or disconnection tends to occur, and when it exceeds 50 μm, it tends to be difficult to embed the insulating layer 3. . Therefore, the wiring conductor 4 preferably has a width of 20 to 200 μm and a thickness of 5 to 50 μm.
[0034]
The insulating layer 3 is provided with a plurality of through conductors 6 from the upper surface to the lower surface. The through conductor 6 has a function of electrically connecting the wiring conductors 2 located above and below the insulating layer 1, has a diameter of 30 to 100 μm, and mainly includes tin in the through hole 5 provided in the insulating layer 3. It is formed by embedding and thermosetting a conductive material composed of a metal powder as a component and a triazine-based thermosetting resin or the like. If the diameter of the through conductor 5 is less than 30 μm, the processing tends to be difficult, and if it exceeds 100 μm, high-density wiring tends not to be formed. Therefore, it is preferable that the diameter of the through conductor 4 be 30 to 100 μm.
[0035]
In the wiring board of the present invention, the entire area of the opening 7b of the gap 7a of the glass cloth 1 is 0.01 to 2% of the area of the glass cloth 1, and the openings 7b are stacked so that they do not vertically overlap. Therefore, the through holes 5 having a uniform diameter can be formed in a range of 30 to 100 μm in diameter.
[0036]
Further, the content of the metal powder 5 of the conductive material is preferably 80 to 95% by weight. When the content of the metal powder 5 is less than 80% by weight, the triazine-based thermosetting resin tends to hinder the connection between the metal powders 5 and increase the conduction resistance. Tends to be too high to be satisfactorily embedded. Therefore, the content of the metal powder of the conductive material is preferably 80 to 95% by weight.
[0037]
Further, a part of the wiring conductor 4 formed on one outermost layer surface of the insulating layer 3 is connected to each electrode of the electronic component (not shown) via a solder bump (not shown). Of the wiring conductor 2 formed on the surface of the other outermost layer of the insulating layer 3 is connected to a conductor bump (not shown) on each electrode of an external electric circuit board (not shown). ) To form an external connection mounting electrode 11b.
[0038]
The surfaces of the mounting electrodes 11a and 11b have good wettability with solder and excellent corrosion resistance in order to prevent their oxidative corrosion and improve the connection with solder bumps (not shown). And a plating layer of nickel-gold or the like.
[0039]
The outermost insulating layer 3 and the mounting electrodes 11a and 11b are coated with a solder-resistant resin layer 12 having an opening for exposing the central portion of the mounting electrodes 11a and 11b as necessary. The solder-resistant resin layer 12 has a thickness of 10 to 50 μm. For example, 30 to 70% by weight of an inorganic powder filler such as silica or talc is added to a mixture of a photosensitive resin such as an acrylic-modified epoxy resin and a photoinitiator. To prevent the adjacent mounting electrodes 11a and 11b from being electrically short-circuited by solder bumps (not shown), and to prevent the mounting electrodes 11a and 11b from being in contact with the insulating layer 3. It has the function of improving the bonding strength.
[0040]
Such a solder-resistant resin layer 12 is formed by applying an uncured resin film composed of a photosensitive resin, a photoinitiator, and an inorganic powder filler on the surface of the outermost insulating layer 3 or by forming a thermosetting resin and an inorganic powder. An uncured resin varnish comprising a filler is applied to the surface of the outermost insulating layer 3 and dried, and thereafter, an opening is formed by exposure and development, and the opening is formed by UV curing and heat curing.
[0041]
The wiring board is manufactured by the method described below. First, for example, two prepregs in which a 50 μm-thick glass cloth 1 is impregnated with a thermosetting resin 2 precursor made of an epoxy resin, a modified polyphenylene resin, or the like are attached so that the openings 7 b of the glass cloth 1 do not overlap vertically. An insulating sheet to be the insulating layer 3 is manufactured by press-flattening the insulating sheet, and then a conventionally known method such as a carbon dioxide gas laser or a YAG laser is used at a predetermined position of the insulating sheet to have a diameter of 30 to 100 μm. A through hole 5 is formed.
[0042]
A conventionally known screen printing method is used for the through-holes 5, and a conductive material containing a metal powder containing tin as a main component and a thermosetting resin precursor such as a triazine-based resin is screen-printed (press-fitted). The through conductor 6 is formed by filling. Thereafter, a transfer sheet made of a heat-resistant resin such as polyethylene terephthalate (PET) resin, in which a separately prepared wiring conductor 4 made of copper foil on the surface is applied in a predetermined pattern on the insulating sheet, is used as an insulating sheet. A predetermined through conductor 5 and a wiring conductor 4 are aligned so that they are connected to each other, and are overlapped. These are pressed by a hot press at a temperature of 100 to 150 ° C. for several minutes to press the transfer sheet against the insulating sheet. Then, the wiring conductor 4 is transferred and embedded in an insulating sheet, and finally manufactured by heating at a temperature of 150 to 200 ° C. for several hours.
[0043]
Alternatively, if necessary, a plurality of insulating sheets from which the transfer sheet has been peeled off may be stacked one above the other, and heated and pressed at a temperature of 150 to 200 ° C. for several hours using a hot press to produce a laminated wiring board.
[0044]
Thus, according to the wiring board of the present invention, the entire area of the opening 7b of the gap 7a surrounded by the warp 1a and the weft 1b of the glass cloth 1 is 0.01 to 2% of the area of the glass cloth 1, and the opening 7b is Since a plurality of sheets are stacked so that they do not overlap one another, the probability that the through holes 5 are formed in the openings 7b of the gaps 7a can be reduced, and the through holes 5 do not continue up and down. As a result, the resistance of the through conductor 6 does not increase, and the rigidity of the wiring board is improved because the insulating layer 3 is formed by laminating a plurality of thin glass cloths 1. Even with a thin wiring board, a wiring board with excellent connection reliability without warpage or breakage of solder bumps can be obtained.
[0045]
Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the wiring board of the present invention has four layers. Although an example of a laminated wiring board formed by lamination has been described, a wiring board of five or more layers may be laminated.
[0046]
【Example】
In order to evaluate the wiring board of the present invention, a wiring board described below was manufactured, and the insulation resistance of the insulating layer and the conduction resistance of the through conductor were evaluated.
[0047]
First, a prepreg obtained by impregnating a glass cloth 1 having a total area of the openings 7b of 0.008 to 3% of the area of the glass cloth and a thickness of 50 μm with a thermosetting resin composition 2 made of an epoxy resin, a modified polyphenylene resin, or the like, An insulating sheet was manufactured by bonding two sheets and flattening them by pressing such that the openings 7b of the glass cloth 1 do not overlap vertically.
[0048]
Next, through holes 5 having a diameter of 30 to 100 μm were formed at predetermined positions of the insulating sheet by using a conventionally known method such as a carbon dioxide gas laser or a YAG laser. A conventionally known screen printing method is adopted for the through-holes 5, and a conductive material containing a metal powder containing tin as a main component and a thermosetting resin precursor such as a triazine-based resin is screen-printed (press-fitted). The through conductor 6 was formed by filling. Then, a separately prepared transfer sheet made of a heat-resistant resin such as polyethylene terephthalate (PET) resin, in which a wiring conductor 4 made of copper foil on the surface is formed in a predetermined pattern on the insulating sheet, is added to the insulating sheet. The transfer sheet is pressed against the insulating sheet by pressing them at a temperature of 100 to 150 ° C. for several minutes using a hot press machine so that the through conductor 5 and the wiring conductor 4 are aligned and connected so as to be connected. Then, the wiring conductor 4 was transferred and embedded in the insulating sheet.
[0049]
After that, the transfer sheet is peeled off from the insulating sheet, and the insulating sheets from which the transfer sheet is peeled are stacked one on top of the other and heated and pressed at 150-200 ° C for several hours using a hot press machine to produce a wiring board did. The insulation resistance value of the insulating layer 3 and the conduction resistance value of the through conductor 5 were measured by four-terminal measurement. Table 1 shows the results.
[0050]
[Table 1]

[0051]
As shown in Table 1, when the ratio of the total area of the openings 7b of the glass cloth 1 was less than 0.01% (Sample No. 1), the insulation resistance of the insulating layer 3 was 10%. ¹³ It turned out that it was less than Ω, and the insulating property was lowered. In addition, when it was more than 2% (Sample No. 6), it was found that a through hole having a uniform diameter could not be formed, and the conduction resistance of the through conductor 5 was as high as 10 mΩ or more. On the other hand, when the ratio of the total area of the openings 7b of the glass cloth 1 is 0.01 to 2% (Sample Nos. 2 to 5), the insulation resistance of the insulating layer 3 is 10%. ¹³ Ω or more, the conduction resistance of the through conductor 5 was less than 10 mΩ, and the wiring substrate was found to be excellent in insulation resistance and low in conduction resistance.
[0052]
Further, the glass cloth 1 was laminated so that the angle between the axial direction of the upper warp 1a and the axial direction of the lower warp 1a was 0 to 90 degrees, and a sample was produced in the same manner as described above. Next, solder bumps were formed on the mounting electrodes 11a of the wiring board, and a semiconductor element was mounted on the upper surface via the solder bumps. The presence or absence of peeling between the mounted semiconductor element and the wiring board was measured by an ultrasonic flaw detector. Separately, only the insulating layer 3 was heated and pressed to measure the elastic modulus of the warp 1a of the insulating layer 3 in the axial direction and the direction at an angle of 45 degrees with the axial direction. Table 2 shows the results.
[0053]
[Table 2]

[0054]
As shown in Table 2, when the angle between the axial direction of the upper warp yarn 1a and the axial direction of the lower warp yarn 1a is less than 15 degrees and exceeds 75 degrees (samples No. 7, 8, 14, 15). It was found that the difference between the elastic modulus of the insulating layer 3 in the warp direction and that in the 45-degree direction was as large as 20% or more. On the other hand, when the angle between the axial direction of the upper warp 1a and the axial direction of the lower warp 1a is 15 to 75 degrees (sample Nos. 9 to 13), the warp direction 1a of the insulating layer 3 and its 45 It was found that the difference in elastic modulus in the degree direction was a small value of 10% or less.
[0055]
【The invention's effect】
According to the wiring board of the present invention, a plurality of glass cloths are laminated, and a wiring conductor is formed on the upper and lower surfaces of the insulating layer formed by impregnating the laminated glass cloth with a thermosetting resin, and the wiring conductors are vertically arranged with the insulating layer interposed therebetween. Since the located wiring conductors are electrically connected via the through conductor provided on the insulating layer, it is not necessary to increase the diameter of the twisted yarn constituting the glass cloth even when the thickness of the insulating layer is large. As a result, the entire area of the opening of the gap of the glass cloth does not increase, and the difference in density between the dense portion and the sparse portion of the twisted yarn does not increase.
[0056]
Further, since the entire area of the opening of the gap of the glass cloth is 0.01 to 2% of the area of the glass cloth, and the openings are laminated so as not to overlap vertically, the dense portion and the sparse portion of the twisted yarn are used. When the through hole is drilled using a laser on the wiring board, a through hole having a uniform inner diameter and an emission diameter can be drilled, and the through hole is filled with a conductive material. When the through conductor is formed in this manner, there is no possibility that the resistance of the through conductor is partially increased or the wire is disconnected.
[0057]
Furthermore, since the insulating layer is formed by laminating a plurality of glass cloths and impregnating the laminated glass cloth with a thermosetting resin, the rigidity of the insulating layer is better when the plurality of glass cloths are laminated even when the insulating layer is thin. As a result, when a semiconductor device such as a large LSI is mounted on a wiring board, a large stress due to a difference in the thermal expansion coefficient between the semiconductor element and the wiring board during operation of the semiconductor element is obtained. Even if it occurs, the semiconductor element does not peel off from the wiring board or the semiconductor element is not destroyed.
[0058]
According to the wiring board of the present invention, the difference between the elastic modulus in the axial direction of the warp and the weft of the glass cloth and the elastic modulus in the direction connecting the intersections of the warp and the weft are large, In contact with, when laminated so that the angle between the axial direction of the upper warp and the axial direction of the lower warp is 15 to 75 degrees, the difference in elastic modulus for each direction of the insulating layer is reduced. As a result, the deformation of the wiring board due to the stress generated when a large-sized LSI or other semiconductor element is mounted on the wiring board can be suppressed, and the semiconductor element peels off from the wiring board or the semiconductor element is destroyed. This can be effectively prevented.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an example of an embodiment of a wiring board of the present invention.
FIG. 2 is a plan view of the glass cloth shown in FIG.
[Explanation of symbols]
1 ... Glass cloth
1a ····· Warp
1b ... weft
2 ···· Thermosetting resin
3 ... Insulating layer
4 .... Wiring conductor
5 ... Through-hole
6 ····· Through conductor
7a ... gap
7b Opening

Claims (2)

A plurality of glass cloths formed by weaving warp yarns and weft yarns are laminated, and the laminated glass cloths are impregnated with a thermosetting resin. Wiring conductors are formed on upper and lower surfaces of an insulating layer. The wiring conductors are electrically connected to each other via a through conductor provided on the insulating layer, and the glass cloth has an area corresponding to the entire area of the opening of the gap surrounded by the warp and the weft. Wherein the openings are stacked so that the openings do not overlap vertically. Among the laminated glass cloths, those that are in contact with the upper and lower sides are laminated such that the angle between the axial direction of the upper warp and the axial direction of the lower warp is 15 to 75 degrees. The wiring board according to claim 1, wherein

Images