JP2004356308A - Insulating layer for wiring board, wiring board using the same, and method of manufacturing the same - Google Patents

Abstract

An insulating layer for a wiring board which can transfer a fine wiring circuit layer made of a metal foil to a surface of an insulating sheet, reduces a difference in thermal expansion with a semiconductor element, and has a low dielectric constant and excellent high-frequency characteristics. And a wiring board using the same and a method for manufacturing the same.
A non-spherical inorganic powder is contained in a resin, and at least one main surface of an uncured or semi-cured main insulating layer (11) having vacancies has an inorganic powder content of 20% by volume or less in the resin. Or a coating layer 13 containing no inorganic powder.
[Selection diagram] FIG.

Description

【０１０１】
【表２】

【０１０２】
表１、２の結果から、主絶縁層に球状のシリカ粉末を用い、空孔を含まない本発明の範囲外の試料Ｎｏ．１では、熱膨張係数が２７×１０^−６／℃と大きくなり、また、誘電率も３．６と大きくなった。
【０１０３】
一方、本発明の試料Ｎｏ．２〜２３では、いずれの試料も熱膨張係数が２５×１０^−６／℃以下となり、誘電率も３．５以下となった。
【０１０４】
主絶縁層の無機粉体充填率を変化させた試料Ｎｏ．２〜６では、無機粉体充填率の増加に伴い、熱膨張係数が低下する傾向にあり、４０体積％以上の試料Ｎｏ．４〜６では、２３×１０^−６／℃以下の熱膨張係数となった。また、ビア加工形状、配線基板の凹凸も良好であった。
【０１０５】
主絶縁層の空孔の体積％を変化させた試料Ｎｏ．７〜１１では、空孔量の増加に伴い、誘電率、熱膨張係数ともに減少し、また、ビア加工形状、配線基板の凹凸も良好であった。
【０１０６】
被覆層厚さ、銅箔厚さを変化させた試料Ｎｏ．１２〜１５では、ｔ２（被覆層の厚み）／ｔ１（配線回路層の厚み）が０．１５未満の試料Ｎｏ．１５で配線基板の凹凸が若干大きくなった。ｔ２／ｔ１が０．１５以上の試料では、いずれも配線基板の凹凸が良好であった。
【０１０７】
主絶縁層の無機粉末粒径を変化させた試料Ｎｏ．１６〜１８では、主絶縁層の無機粉末粒径が１μｍ以下の試料Ｎｏ．１６において良好なビア加工形状が得られた。なお、他の試料では、実用上問題はないものの、若干ビア形状がいびつになった。
【０１０８】
被覆層の無機粉末粒径を変化させた試料Ｎｏ．１９〜２１では、被覆層の無機粉末粒径が１μｍ以下の試料Ｎｏ．１９において良好なビア加工形状が得られた。なお、他の試料では、実用上問題はないものの、若干ビア形状がいびつになった。
【０１０９】
被覆層の粉体充填率を変化させた試料Ｎｏ．２２〜２５では、被覆層の粉体充填率が２０体積％以下の試料Ｎｏ．２２、２３では良好な銅箔転写強度が得られたが、本発明の範囲外である被覆層の粉体充填率が２０体積％を超える試料Ｎｏ．２４、２５では、銅箔転写強度が０．２ｋｇｆ／ｃｍ以下となり、良好な銅箔転写強度が得られなかった。また、積層性も劣っていた。
【０１１０】
【発明の効果】
空孔を有する主絶縁層と、無機粉末量が２０体積％以下である被覆層の積層体である配線基板用絶縁層を用いることで、積層性に優れ、熱膨張係数が小さく、かつ誘電率の小さな配線基板を得ることができる。
【図面の簡単な説明】
【図１】本発明の配線基板の製造方法を示す概略図である。
【図２】本発明の配線基板の製造方法を示す概略図である。
【図３】本発明の配線基板の製造方法を示す概略図である。
【図４】本発明の配線基板を示す断面図である。
【符号の説明】
１１・・・絶縁シート
１３・・・被覆層
１５・・・配線基板用絶縁層
２５・・・配線回路層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wiring board insulating layer for manufacturing a wiring board, and a method for manufacturing a wiring board suitable for an electric element storage package, a multilayer wiring board, and the like using the same.
[0002]
[Prior art]
The insulating layer of a conventional wiring board is composed of a resin component and glass cloth, and has a thermal expansion coefficient larger than that of a semiconductor element mounted on the wiring board, and the bonding reliability between the two is not sufficient. In order to make the thermal expansion coefficient of the insulating layer close to that of the semiconductor element, it is sufficient to add a large amount of inorganic powder having a lower thermal expansion coefficient than that of the resin, but for example, in the case of the copper foil transfer method, the resin required for the transfer is insufficient. Therefore, there is a problem that the wiring circuit is difficult to be transferred to the insulating sheet, so that the amount of the inorganic powder added is limited, and it has been difficult to sufficiently reduce the thermal expansion coefficient of the insulating layer.
[0003]
To solve this problem, by optimizing the melt viscosity of the resin, the shape and particle size of the inorganic powder, the open porosity, etc., the thermal expansion coefficient of the insulating layer is reduced, and the thermal expansion difference with the semiconductor element is reduced. It has been reported that a wiring board having excellent moisture resistance can be manufactured (see Patent Document 1).
[0004]
In addition, the insulating sheet has a two-layer structure consisting of a high-concentration powder sheet in which the amount of inorganic powder is increased and a low-concentration powder sheet in which the amount of inorganic powder is smaller than that of the high-concentration powder sheet. An insulating sheet capable of transferring a fine wiring pattern satisfactorily and a method for producing the same, and a wiring board having a surface multilayer wiring layer excellent in dimensional accuracy by using such an insulating sheet and a method for producing the same have been reported (Patent Documents). 2).
[0005]
[Patent Document 1]
JP 2001-68802 A
[0006]
[Patent Document 2]
JP 2003-110246 A
[0007]
[Problems to be solved by the invention]
However, in the prior art, when a large amount of inorganic powder is added to reduce the coefficient of thermal expansion, the dielectric constant increases depending on the type of the resin and the inorganic powder (for example, ε = 2.5 in the case of APPPE and silica in the case of inorganic powder). Ε = 4.5), the more the inorganic powder is added, the more the dielectric constant of the entire wiring board increases, and there is a problem that the high-frequency characteristics deteriorate.
[0008]
The present invention solves the above-mentioned conventional problems. In addition to being able to satisfactorily transfer a fine wiring circuit layer made of metal foil to the surface of an insulating sheet, the present invention reduces the difference in thermal expansion from an electric element, and has a low dielectric constant. It is an object of the present invention to provide a wiring board insulating layer having excellent high-frequency characteristics, a wiring board using the same, and a method of manufacturing the same.
[0009]
[Means for Solving the Problems]
The insulating layer for a wiring board according to the present invention includes a non-spherical inorganic powder in a resin, and at least one main surface of an uncured or semi-cured main insulating layer having vacancies, having a volume of 20 vol. % Or less of an inorganic powder or a coating layer containing no inorganic powder.
[0010]
In the main insulating layer of such an insulating layer for a wiring board, since the inorganic powder is non-spherical, the filling property is low, and the main insulating layer has a form containing holes. Since air having a dielectric constant lower than that of the resin or the inorganic powder (dielectric constant: 1.0) is present in these holes, a main insulating layer having a low dielectric constant can be provided after curing.
[0011]
In the main insulating layer including such a resin, the non-spherical inorganic powder, and the pores, the non-spherical inorganic powder forms a skeleton, and the resin and the pores are formed between the skeletons formed by the inorganic powder. Is present.
[0012]
In such a form, even if the main insulating layer is heated, the volume expansion of the resin is consumed in reducing the volume of the pores, and therefore, the theoretical expansion coefficient and the ratio of the volume of the material forming the main insulating layer indicate a theoretical value. The actual coefficient of thermal expansion of the main insulating layer is smaller than the coefficient of thermal expansion of the main insulating layer, which is locally derived. Therefore, in such a mode, a main insulating layer having a small thermal expansion coefficient can be obtained. In a wiring board including such a main insulating layer, the wiring board has a small thermal expansion coefficient. It is possible to improve the reliability of bonding with an electric element mounted on the substrate.
[0013]
In addition, since the main insulating layer has a small amount of resin, it is difficult to transfer a wiring circuit to the main insulating layer, and it is difficult to laminate the main insulating layers. By providing a coating layer containing 20% by volume or less of inorganic powder in the resin or containing no inorganic powder, that is, a coating layer containing 80% by volume or more of resin on the surface of the coating layer, A wiring circuit can be transferred, and by laminating so that a coating layer is arranged between main insulating layers, a strong wiring substrate can be manufactured. Such a wiring board has a low dielectric constant and a low coefficient of thermal expansion, and has excellent electrical characteristics and connection reliability with an electric element.
[0014]
Further, in the insulating layer for a wiring board according to the present invention, it is preferable that the main insulating layer contains 40% by volume or more of non-spherical inorganic powder.
[0015]
As described above, when the main insulating layer contains 40% by volume or more of the non-spherical inorganic powder, the resin is almost present in the gap between the skeletons formed by the inorganic powder, and the skeleton formed by the inorganic powders Becomes immobile to the heat and pressure applied to the sheet. In addition, since the amount of resin is relatively reduced, the coefficient of thermal expansion of the main insulating layer is close to the coefficient of thermal expansion of the inorganic powder, so that the reliability of bonding to an electric element or the like can be further improved.
[0016]
According to the insulating layer for a wiring board of the present invention, it is desirable that the porosity of the main insulating layer is 5% by volume or more.
[0017]
By setting the pores of the main insulating layer to 5% by volume or more, the amount of air having a low dielectric constant can be increased, and the dielectric constant of the main insulating layer obtained by curing the main insulating layer can be increased. Can be reduced, and the dielectric constant of the entire wiring board can be reduced.
[0018]
Further, in the wiring board insulating sheet of the present invention, the thickness of the coating layer is preferably 2 μm or more, and the total thickness of the wiring board insulating layer formed by overlapping the main insulating layer and the coating layer is preferably 50 μm or less. .
[0019]
By setting the thickness of the coating layer to 2 μm or more, the adhesiveness between the wiring circuit layer and the coating layer can be sufficiently ensured, and the wiring circuit layer can be satisfactorily transferred to the surface of the coating layer.
[0020]
Further, when the thickness of the insulating layer for a wiring board formed by overlapping the main insulating layer and the coating layer is set to 50 μm or less, for example, the number of shots required for laser processing can be reduced, and the tact of processing can be shortened. . Further, by reducing the thickness of the wiring board insulating layer, the wiring length of the wiring board can be shortened, and a malfunction due to signal delay or noise can be reduced.
[0021]
The insulating layer for a wiring board of the present invention is characterized in that the average particle size of the inorganic powder contained in the main insulating layer and the coating layer is 1 μm or less.
[0022]
The via shape formed by via processing changes depending on the shape of the inorganic powder contained in the main insulating layer and the coating layer. By using finer inorganic powder, a clean via shape can be obtained. By setting the average particle size of the inorganic powder contained in the layer to 1 μm or less, the via shape can be formed neatly, and even if the particles fall out of the via hole, the via particle shape is small due to the small particle size of the inorganic powder. Impact on the system can be minimized.
[0023]
Further, in the insulating layer for a wiring board of the present invention, it is desirable that the aspect ratio of the non-spherical inorganic powder contained in the main insulating layer is 2 or more.
[0024]
As described above, by setting the aspect ratio of the non-spherical inorganic powder included in the main insulating layer to 2 or more, the main insulating layer can contain more vacancies, and the inorganic powders can form particles and particles. Since slippage at the interface is reduced, rearrangement of particles due to temperature or pressure fluctuations is suppressed, the thermal expansion coefficient of the main insulating layer can be reduced, and the thermal expansion coefficient of the main element can be approximated.
[0025]
Further, since a large number of holes can be formed in the main insulating layer with a smaller amount of inorganic powder, the main insulating layer can contain many holes having a low dielectric constant, and the dielectric constant of the main insulating layer can be reduced. Can be reduced.
[0026]
Further, the wiring board according to the present invention is a wiring board formed by laminating a plurality of insulating layers containing a resin and forming a wiring circuit layer on the surface and / or inside the insulating layer, wherein the insulating layer is formed of a non-spherical inorganic material. It is preferable to include a main insulating layer containing powder and having pores, and a coating layer containing 20% by volume or less of inorganic powder in a resin or containing no inorganic powder.
[0027]
Such a wiring board has a low filling rate of the main insulating layer and contains voids in the main insulating layer. Since the resin is sufficiently present at the interface between the wiring circuit layer and the interface between the coating layer and the main insulating layer, the coating layer and the wiring circuit layer and between the coating layer and the main insulating layer are firmly adhered to each other. A wiring substrate can be manufactured.
[0028]
Further, in the wiring board of the present invention, it is desirable that the main insulating layer contains a non-spherical inorganic powder of 40% by volume or more.
[0029]
In such a wiring substrate, the main insulating layer contains 40% by volume or more of non-spherical inorganic powder, so that the resin has almost no gaps between the inorganic powders. Since the layer is immovable with respect to the heating and pressure applied to the layer, deformation of the wiring board due to heat and stress is suppressed. In addition, since the amount of resin relatively decreases, the thermal expansion coefficient of the main insulating layer approaches and becomes smaller than that of the inorganic powder, and the thermal expansion coefficient of the wiring board can be reduced. It is possible to improve the reliability of bonding with an element or the like.
[0030]
Further, in the wiring board of the present invention, it is desirable that the pores of the main insulating layer be 5% by volume or more. In such a wiring board, the ratio of holes having a low dielectric constant contained in the wiring board increases, and the dielectric constant of the wiring board can be reduced.
[0031]
In the wiring board of the present invention, it is desirable that the average particle size of the inorganic powder in the main insulating layer and the coating layer is 1 μm or less.
[0032]
In such a wiring board, the via shape can be formed close to the design, and the number of particles of the inorganic powder is small. Therefore, the via shape is constant, the via resistance and the like are uniform, and the impedance of the substrate can be easily controlled.
[0033]
Further, in the wiring board of the present invention, it is desirable that the aspect ratio of the non-spherical inorganic powder contained in the main insulating layer is 2 or more.
[0034]
As described above, by setting the aspect ratio of the non-spherical inorganic powder included in the main insulating layer to 2 or more, the rearrangement of the inorganic powder in the main insulating layer is less likely to occur. In addition to the above, it is possible to introduce more holes into the main insulating layer with respect to the content of the inorganic powder, so that the dielectric constant can be reduced.
[0035]
In the wiring board of the present invention, it is preferable that t2 / t1 ≧ 0.15, where t1 is the thickness of the wiring circuit layer and t2 is the thickness of the covering layer.
[0036]
As described above, by setting the relationship between the thickness t1 of the wiring circuit layer and the thickness t2 of the coating layer to be t2 / t1 ≧ 0.15, the thickness of the coating layer having a thickness equal to or greater than a certain value with respect to the thickness t1 of the wiring circuit layer is obtained. The thickness is secured, the adhesiveness between the wiring circuit layer and the covering layer can be secured, and the wiring circuit layer can be easily embedded in the insulating layer. Therefore, the adhesiveness between the insulating layer and the wiring circuit layer can be further improved. it can.
[0037]
In the wiring board of the present invention, it is desirable that the thickness of the covering layer is 2 μm or more, and the thickness of the insulating layer formed by overlapping the main insulating layer and the covering layer is 50 μm or less.
[0038]
By setting the thickness of the coating layer to 2 μm or more, sufficient resin is secured between the wiring circuit layer and the coating layer, and the adhesive strength between the wiring circuit layer and the coating layer becomes strong.
[0039]
In addition, when the thickness of the insulating layer formed by overlapping the main insulating layer and the covering layer is set to 50 μm or less, the via processability is improved and the via shape is stabilized, so that the circuit impedance is stabilized. In addition, as the thickness of the insulating layer is reduced, the wiring length is reduced, and malfunction due to signal delay and noise is reduced.
[0040]
The method for producing an insulating layer for a wiring board according to the present invention comprises an insulating slurry containing at least a resin and a non-spherical inorganic powder; and a coating slurry containing a resin and containing 20% by volume or less of an inorganic powder or containing no inorganic powder. And forming a main insulating layer by a sheet forming method using the insulating slurry of the two slurries; and forming a sheet using the coating slurry on the surface of the main insulating layer. And laminating a coating layer by a method.
[0041]
With such a manufacturing method, an insulating sheet having a coating layer formed on at least one main surface of the main insulating layer can be easily manufactured. Further, using this insulating sheet, a wiring board having excellent bonding reliability with an electric element and having a low dielectric constant can be easily manufactured.
[0042]
Further, the method for manufacturing a multilayer wiring board of the present invention,
(A) forming a core laminate formed by forming a conductor wiring layer on at least a surface of an insulating base material containing at least a resin;
(B) a step of thermocompression bonding the insulating layer for a wiring board according to any one of claims 1 to 6 on a surface of the core laminate;
(C) irradiating a predetermined portion of the insulating layer for a wiring board with a laser beam to form a through hole;
(D) filling a through-hole formed in (c) with a conductive paste containing a metal powder and an organic component to form a via conductor;
(E) forming a finely processed wiring circuit layer on the wiring board insulating layer on which the via conductor is formed, and forming a conductor wiring layer having a roughened upper surface side;
(F) repeating steps (b) to (e) to form a multilayer.
[0043]
In such a manufacturing method, first, since a large amount of a resin component is present on at least one main surface of the wiring board insulating layer, only the main insulating layer is transferred when the wiring circuit layer is transferred to the wiring board insulating layer. As compared with the case, the wiring circuit layer miniaturized under relatively low temperature and low pressure can be easily transferred to the wiring board insulating layer. In addition, the resin enters the uneven portion on the surface of the wiring circuit layer, and the anchor effect is enhanced, so that the wiring circuit layer and the insulating layer can be firmly bonded.
[0044]
In addition, since a large amount of resin is present on at least one main surface of the wiring board insulating layer, the wiring board insulating layers are firmly adhered to each other even after the wiring circuit layer is formed on the wiring board insulating layer. it can.
[0045]
In addition, by increasing the amount of resin on at least one main surface of the wiring board insulating layer forming the wiring circuit layer, the transferability of the wiring circuit layer is increased and the amount of resin in the main insulating layer is reduced. Since the mechanical strength and Young's modulus of the insulating layer can be increased, and the deformation of the insulating layer can be suppressed even under pressure and heating during transfer and lamination, a wiring board having a wiring circuit layer with high dimensional accuracy can be easily manufactured. Can be manufactured.
[0046]
BEST MODE FOR CARRYING OUT THE INVENTION
The insulating layer for a wiring board according to the present invention includes at least one of an uncured or semi-cured main insulating layer 11 having non-spherical inorganic powder in a resin and having pores as shown in FIG. And a coating layer 13 containing 20% by volume or less of inorganic powder in the resin or containing no inorganic powder in the resin.
[0047]
The shape of the inorganic powder contained in the main insulating layer 11 is non-spherical because the rearrangement of the particles is prevented, the coefficient of thermal expansion is reduced, the number of pores is formed, the dielectric constant and the dielectric loss are reduced. It is necessary to be.
[0048]
Further, in order to reduce the coefficient of thermal expansion of the main insulating layer 11, it is preferable that the main insulating layer contains 40% by volume or more of non-spherical inorganic powder. In order to improve mounting reliability, it is desirable to contain 50% by volume or more of non-spherical inorganic powder.
[0049]
As the inorganic powder used, SiO 2 ₂ , Al ₂ O ₃ , AlN, SrTiO ₃ The average particle size of the inorganic powder contained in the main insulating layer 11 and the coating layer 13 is desirably 1 μm or less, in particular, 0.7 μm or less in order to form the via hole in a shape close to the design. Inorganic powder is used. By using such a fine inorganic powder, even when a fine via hole for interlayer connection is formed in the thin insulating layer 15 for a wiring board having a thickness of 50 μm or less, the inorganic powder does not become an obstacle, and the via hole having a good shape is formed. Can be easily formed.
[0050]
The aspect ratio of the non-spherical inorganic powder contained in the main insulating layer 11 is desirably 2 or more in order to prevent rearrangement of the particles and stably increase the coefficient of thermal expansion.
[0051]
Further, in order to reduce the dielectric constant and the dielectric loss of the main insulating layer 11, the main insulating layer 11 desirably contains many holes having a low dielectric constant or the like. It is desirable to include holes.
[0052]
The content of the inorganic powder contained in the coating layer 13 must be not more than 20% by volume or not contained in order to improve the transferability of the wiring circuit layer. In order to reduce the size, the content of the inorganic powder is preferably set to 10 to 20% by volume.
[0053]
The thickness of the coating layer 13 is preferably 2 μm or more in order to transfer the wiring circuit layer satisfactorily. The thickness of the wiring board insulating layer 15 formed by overlapping the main insulating layer 11 and the coating layer 13 is In order to shorten the wiring length and improve the hole workability, the thickness is desirably 50 μm or less, and particularly desirably 40 μm or less.
[0054]
Resins used for the main insulating layer 11 and the coating layer 13 include thermosetting PPE (polyphenylene ether), BT resin (bismaleimide triazine), epoxy resin, polyimide resin, fluororesin, phenol resin, and polyaminobismaleimide. At least one selected from the group is suitably used.
[0055]
As shown in FIG. 4, the wiring board of the present invention contains a non-spherical inorganic powder and a main insulating layer 11 having pores, and a resin containing 20% by volume or less of inorganic powder in a resin, or an inorganic powder. Are alternately stacked, and a wiring circuit layer 25 is formed inside and on the surface of the wiring board 24 between the main insulating layers 11 and on the surface of the coating layer 13, and the main insulating layer 11 and the coating layer 13 are formed. , A via conductor 19 is formed, and the wiring circuit layer 25 and the via conductor 19 are electrically connected to each other.
[0056]
In such a wiring board 24, the main insulating layer 11 and the covering layer 13 have a function of electrically insulating the wiring circuit layer 25 and the via conductor 19 of the wiring board 24, and are made of an insulator.
[0057]
The wiring circuit layer 25 and the via conductor 19 form a wiring circuit in the wiring board 24. The wiring circuit layer 25 is made of copper foil or the like, and the via conductor 19 is made of a mixture of metal powder and resin. Things.
[0058]
In such a wiring board 24, the main insulating layer 11 has a role of reducing the coefficient of thermal expansion and the dielectric constant, and reducing the coefficient of thermal expansion of the wiring board 24.
[0059]
The covering layer 13 formed on the main surface of the main insulating layer 11 firmly bonds the main insulating layers 11 to each other and the covering layer 13 to the wiring circuit layer 25.
[0060]
The main insulating layer 11 needs to contain non-spherical inorganic powder and voids in order to reduce the coefficient of thermal expansion and reduce the dielectric constant.
[0061]
The amount of the inorganic powder is desirably 40% by volume or more in order to reduce the thermal expansion coefficient of the main insulating layer 11, and particularly, the connection reliability with an electric element mounted on the wiring board 24, for example, a semiconductor element. In order to improve the density, it is desirable that the content be 50% by volume or more.
[0062]
In addition, the inorganic powder used for the main insulating layer 11 is desirably 1 μm or less, particularly 0.7 μm or less, since the via shape is uniform and impedance control is easy.
[0063]
In addition, the inorganic powder used for the main insulating layer 11 preferably has an aspect ratio of 2 or more, and more preferably 3 or more, from the viewpoint of preventing the main insulating layer 11 from being deformed by heat.
[0064]
The pores of the main insulating layer 11 are desirably at least 5% by volume, preferably at least 10% by volume and at least 15% by volume in order to reduce the coefficient of thermal expansion of the main insulating layer 11 and reduce the dielectric constant. With the above values, the coefficient of thermal expansion and the dielectric constant can be further reduced.
[0065]
In addition, the inorganic powder of the coating layer 13 needs to be 20% by volume or less or contains no inorganic powder. By setting the amount of the inorganic powder to 20% by volume or less, the amount of resin increases, and the adhesive strength between the main insulating layer 11 and the coating layer 13 and between the coating layer 13 and the wiring circuit layer 25 can be sufficiently increased.
[0066]
Either spherical particles or non-spherical particles may be used for the inorganic powder of the coating layer 13. However, when the spherical particles are used, the inorganic powder is regenerated when the wiring circuit layer 25 is transferred to the coating layer 13. Since the resin flows easily in the arrangement and the resin easily fills the anchor portion of the wiring circuit layer 25, it is desirable in that the adhesive strength can be increased with the same amount of the inorganic powder added.
[0067]
When the thickness of the wiring circuit layer 25 is t1 and the thickness of the covering layer 13 is t2, it is desirable that t2 / t1 ≧ 0.15. By setting the thickness in such a range, the thickness t2 of the coating layer 13 that is equal to or more than a certain value with respect to the thickness t1 of the wiring circuit layer 25 is ensured, and the adhesion between the wiring circuit layer 25 and the coating layer 13 can be ensured. Since the wiring circuit layer 25 is easily embedded in the coating layer 13, the adhesiveness between the coating layer 13 and the wiring circuit layer 25 can be further improved. Further, when t2 / t1 ≧ 0.8, the deformation of the main insulating layer 11 can be suppressed, and the wiring circuit layer 25 can be embedded and adhered to the coating layer 13 that is relatively easily deformed, which is particularly preferable.
[0068]
By setting t2 / t1 ≦ 2, the thickness of the coating layer 13 that is easily deformed can be suppressed, and the dimensional change of the wiring circuit layer 25 can be prevented.
[0069]
Further, by setting the thickness of the coating layer 13 to 2 μm or more, it is desirable from the viewpoint that the adhesiveness between the wiring circuit layer 25 and the coating layer 13 is improved, and more desirably 5 μm or more. The thickness of the insulating layer 29 formed by overlapping the main insulating layer 11 and the covering layer 13 is desirably 50 μm or less in consideration of impedance characteristics and the like.
[0070]
Next, a method for manufacturing a wiring board 24 using the wiring board insulating layer 15 of the present invention will be described with reference to FIGS.
[0071]
First, an insulating slurry containing at least a resin and a non-spherical inorganic powder, and a coating slurry containing a resin and containing 20% by volume or less of an inorganic powder or containing no inorganic powder are prepared.
[0072]
Next, as shown in FIG. 1A, a main insulating layer 11 is formed from an insulating slurry by a sheet forming method such as a doctor blade method.
[0073]
Next, as shown in FIG. 1B, a coating layer 13 is laminated on one main surface of the main insulating layer 11 by using a coating slurry by a sheet forming method, and an insulating layer 15 for a wiring board is produced.
[0074]
Alternatively, the main insulating layer 11 may be formed in advance from an insulating slurry, the coating layer 13 may be formed from a coating slurry, and both may be laminated by a sheet forming method.
[0075]
The coating layer 13 containing resin and inorganic powder is preferably in an uncured state or a semi-cured state (B stage) before lamination. When cured, the adhesive strength between the wiring board insulating layers 15 decreases, and peeling between layers occurs.
[0076]
When the coating layers 13 are provided on both surfaces of the main insulating layer 11 as shown in FIG. 1C, as another method, first, the coating layers 13a are formed from the coating slurry by a sheet forming method such as a doctor blade method. The main insulating layer 11 is formed from the insulating slurry on the main surface of the coating layer 13a, and the coating layer 13a is formed on the main surface of the main insulating layer 11 from the coating slurry.
[0077]
Next, as shown in FIG. 2D, via holes 17 are formed in the insulating layer 15 for a wiring board manufactured as described above by a punching method, laser processing, plasma etching, or the like.
[0078]
The via diameter of the via hole 17 is preferably used in the range of 30 to 300 μm. If it exceeds 300 μm, the resin is burned by the heat of the laser, and the residue adheres around the via hole 17, which is not desirable. If a larger hole is required, it is better to use a drill.
[0079]
Next, as shown in FIG. 2E, the via hole 17 is filled with a conductive paste to form a via hole conductor 19.
[0080]
The conductor paste to be filled in the via hole 17 is a mixture obtained by adding a resin component such as epoxy or cellulose to a metal powder and kneading the mixture with a solvent such as butyl acetate. , Aluminum, silver, and gold. If desired, after filling the holes, heat treatment may be performed at 60 to 140 ° C. to decompose, volatilize and remove the solvent and resin components in the paste.
[0081]
Next, a wiring circuit layer 25 is provided on the cover layer 13 side of the wiring board insulating layer 15 having the via-hole conductor 19.
[0082]
For example, in the transfer method, as shown in FIG. 2F, the wiring circuit layer 25 of the film 29 with a metal foil in which the wiring circuit layer 25 prepared in advance is laminated on the coating layer 13 side of the insulating layer 15 for the wiring board. After the laminate was heated at 60 to 150 ° C. and pressurized at 1 to 5 MPa for 1 to 10 minutes, as shown in FIGS. By peeling off, the wiring board insulating layers 15a and 15c in which the wiring circuit layer 25 is embedded on the upper surface of the wiring board insulating layer 15 can be manufactured.
[0083]
The coating layer 13 and the wiring circuit layer 25 of the wiring board insulating layer 15 formed by laminating the main insulating layer 11 and the coating layer 13 were heated under pressure, for example, at a temperature of 100 ° C. and a pressure of 2 MPa or more. The bonding strength at that time is desirably 0.2 kgf / cm or more.
[0084]
The adhesion strength is a value obtained by transferring a copper foil of 25 mm × 100 mm produced in the same manner as described above to the coating layer 13 and performing a 180 ° peel test.
[0085]
By setting the adhesive strength between the coating layer 13 and the wiring circuit layer 25 within the above range, the adhesive strength between the wiring circuit layer 25 and the film on which the wiring circuit layer 25 is formed is more than the adhesive strength between the coating layer 13 and the wiring circuit layer 25. Therefore, the transferability of the wiring circuit layer 25 to the coating layer 13 can be improved, and good transferability can be secured.
[0086]
Similarly, the wiring circuit layer 25 is buried on the upper and lower surfaces of the wiring board insulating layer 15 at the same time, and the insulating sheet 15b shown in FIG. As described above, the resin film 29 including the wiring circuit layer 25 is laminated on the upper and lower surfaces of the wiring board insulating layers 15a, 15b, and 15c as necessary, and pressed to form a two-layer wiring circuit on the wiring board 24. The step of transferring the layer 25 can be performed simultaneously.
[0087]
Further, the wiring circuit layer 25 buried in the surface of the wiring board insulating layer 15 manufactured as described above is subjected to a roughening treatment so that the surface roughness (Ra) of the wiring circuit layer 25 is 0.2 μm or more. It is particularly desirable that the thickness be 0.4 μm or more.
[0088]
Then, as shown in FIG. 3 (h), after laminating and integrating the wiring board insulating layers 15a, 15b, 15c, the thermosetting resin of the main insulating layer 11 and the coating layer 13 is completely cured. By heating at a temperature of 200 to 260 ° C. and a pressure of 2 to 6 MPa for 0.5 to 6 hours, a wiring board as shown in FIG. 4 can be manufactured.
[0089]
The main insulating layer 11 and the coating layer 13 may be formed into a sheet shape by using a doctor blade method, for example, by using a rolling method, an extrusion method, an injection method, or the like, and then laminated. Is also possible.
[0090]
In that case, for example, a composition containing a resin and a non-spherical inorganic powder is sufficiently mixed by means such as a kneader or a three-roll mill, and this is rolled, extruded, injected, doctor bladed, etc. After molding into a sheet by, for example, the resin is semi-cured. For semi-curing, if the resin is a thermoplastic resin, cool the mixture mixed under heating, and in the case of a thermosetting resin, heat to a temperature slightly lower than the temperature sufficient for complete solidification. Good.
[0091]
Also, the coating layer 13 can be formed into a sheet by the above-described method by changing the resin to a composition containing 20% by volume or less of the inorganic powder in the resin, or changing to a composition not containing the inorganic powder.
[0092]
Other methods for forming the wiring circuit layer 25 include a method of screen-printing a conductive paste on the surface of the coating layer 13 and a method of forming a wiring pattern by bonding a metal foil to an insulating sheet and then using a photoresist method or the like. A method of forming the circuit layer 25 is given.
[0093]
Note that the present invention is not limited to the above-described embodiment, and various changes can be made without changing the gist of the present invention.
[0094]
For example, finer wiring may be manufactured on the surface of the wiring board 24 manufactured as described above, for example, using a technique such as build-up.
[0095]
【Example】
The thermosetting PPE resin and the spherical and non-spherical silica powders are weighed and mixed in the ratio of Table 1 to prepare an insulating slurry and a coating slurry, and a coating layer is formed from the coating slurry by using a doctor blade method. did. Further, a main insulating layer was formed on the upper surface of the coating layer using a doctor blade method using an insulating slurry. Further, a coating layer was formed on the upper surface of the main insulating layer of the laminate of the coating layer and the main insulating layer from the coating slurry by using a doctor blade method.
[0096]
Thus, an insulating sheet having a three-layer structure in which the coating layers were laminated on both surfaces of the main insulating layer having the thickness shown in Table 1 was produced.
[0097]
Then, a via hole having a diameter of 0.07 mm was formed in the insulating sheet using a carbon dioxide laser, and the shape of the via hole was observed with a scanning electron microscope (SEM). The via hole was filled with a copper paste containing copper powder plated with silver to form a via-hole conductor, thereby producing an insulating layer for a wiring board.
[0098]
Next, the insulating layer for the wiring board and the copper foil transfer film formed by etching are aligned with an image recognition processing apparatus, and heated and pressed at 130 ° C. for 10 minutes at 2 MPa, and the wiring circuit layer is insulated for the wiring board. It was transferred to a layer and cured at 5 ° C. for 1 hour at 200 ° C., and transferability and flatness were evaluated.
[0099]
Further, the insulating sheet having a three-layer structure was cured without providing a via hole, and the thermal expansion coefficient and the dielectric constant were measured. The coefficient of thermal expansion was measured in the range of 40 to 200 ° C., and the dielectric constant was measured at a frequency of 1 GHz. The measured values are shown in Table 2.
[0100]
[Table 1]

[0101]
[Table 2]

[0102]
From the results shown in Tables 1 and 2, it was found that Sample No. 3 which was not included in the scope of the present invention and did not contain voids, using spherical silica powder for the main insulating layer. In the case of 1, the thermal expansion coefficient is 27 × 10 ^-6 / ° C and the dielectric constant also increased to 3.6.
[0103]
On the other hand, the sample No. In samples 2 to 23, each sample had a thermal expansion coefficient of 25 × 10 ^-6 / ° C or lower, and the dielectric constant is also 3.5 or lower.
[0104]
Sample No. in which the inorganic powder filling ratio of the main insulating layer was changed. In Nos. 2 to 6, the thermal expansion coefficient tends to decrease with an increase in the inorganic powder filling rate. In 4-6, 23 × 10 ^-6 / ° C or lower. Also, the via processing shape and the unevenness of the wiring board were good.
[0105]
Sample No. in which the volume% of the holes in the main insulating layer was changed. In Nos. 7 to 11, both the dielectric constant and the coefficient of thermal expansion decreased with an increase in the amount of vacancies, and the via processed shape and the unevenness of the wiring board were also good.
[0106]
Sample No. in which the thickness of the coating layer and the thickness of the copper foil were changed. In Sample Nos. 12 to 15, t2 (thickness of the covering layer) / t1 (thickness of the wiring circuit layer) was less than 0.15. In No. 15, the unevenness of the wiring board was slightly increased. In each of the samples having t2 / t1 of 0.15 or more, the unevenness of the wiring board was good.
[0107]
Sample No. in which the particle diameter of the inorganic powder of the main insulating layer was changed. In Nos. 16 to 18, Sample No. 1 in which the inorganic powder particle size of the main insulating layer was 1 μm or less. In No. 16, a good via processed shape was obtained. In the other samples, although there was no problem in practical use, the via shape was slightly distorted.
[0108]
Sample No. in which the inorganic powder particle size of the coating layer was changed. In Nos. 19 to 21, Sample No. 1 in which the inorganic powder particle size of the coating layer was 1 μm or less. In No. 19, a good via processed shape was obtained. In the other samples, although there was no problem in practical use, the via shape was slightly distorted.
[0109]
Sample No. in which the powder filling rate of the coating layer was changed. In Sample Nos. 22 to 25, the powder filling rate of the coating layer was 20% by volume or less. In Samples Nos. 22 and 23, good copper foil transfer strength was obtained. However, Sample No. 22 having a powder filling rate of the coating layer exceeding 20% by volume was out of the range of the present invention. In Nos. 24 and 25, the copper foil transfer strength was 0.2 kgf / cm or less, and good copper foil transfer strength was not obtained. Moreover, the lamination property was also inferior.
[0110]
【The invention's effect】
By using an insulating layer for a wiring board, which is a laminate of a main insulating layer having pores and a coating layer having an inorganic powder content of 20% by volume or less, excellent laminability, a low coefficient of thermal expansion, and a dielectric constant are obtained. A small wiring board can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic view illustrating a method for manufacturing a wiring board according to the present invention.
FIG. 2 is a schematic view illustrating a method for manufacturing a wiring board according to the present invention.
FIG. 3 is a schematic view illustrating a method for manufacturing a wiring board according to the present invention.
FIG. 4 is a sectional view showing a wiring board of the present invention.
[Explanation of symbols]
11 ... insulating sheet
13 ... Coating layer
15 ... insulating layer for wiring board
25 ... wiring circuit layer

Claims (15)

Non-spherical inorganic powder in the resin, and at least one main surface of an uncured or semi-cured main insulating layer having pores, the resin containing 20% by volume or less of the inorganic powder, or An insulating layer for a wiring board, wherein a coating layer containing no powder is superposed. The insulating layer for a wiring board according to claim 1, wherein the main insulating layer contains 40% by volume or more of non-spherical inorganic powder. 3. The insulating layer for a wiring board according to claim 1, wherein the porosity of the main insulating layer is 5% by volume or more. The thickness of the coating layer is 2 μm or more, and the total thickness of the wiring board insulating layer formed by overlapping the main insulating layer and the coating layer is 50 μm or less. 3. The insulating layer for a wiring board according to item 1. The insulating layer for a wiring board according to any one of claims 1 to 4, wherein the average particle diameter of the inorganic powder contained in the main insulating layer and the coating layer is 1 µm or less. The insulating layer for a wiring board according to any one of claims 1 to 5, wherein the aspect ratio of the non-spherical inorganic powder contained in the main insulating layer is 2 or more. In a wiring board formed by laminating a plurality of insulating layers containing a resin and forming a wiring circuit layer on the surface and / or inside of the insulating layer, the insulating layer contains a non-spherical inorganic powder, and has pores. A wiring board, comprising: a main insulating layer having the same; and a coating layer containing 20% by volume or less of inorganic powder in a resin or containing no inorganic powder. The wiring board according to claim 7, wherein the main insulating layer contains 40% by volume or more of non-spherical inorganic powder. 9. The wiring board according to claim 7, wherein the voids of the main insulating layer are 5% by volume or more. 10. The wiring board according to claim 7, wherein the average particle size of the inorganic powder in the main insulating layer and the coating layer is 1 μm or less. The wiring substrate according to any one of claims 7 to 10, wherein the aspect ratio of the non-spherical inorganic powder contained in the main insulating layer is 2 or more. 12. The wiring board according to claim 7, wherein t2 / t1 ≧ 0.15, where t1 is the thickness of the wiring circuit layer and t2 is the thickness of the covering layer. 13. The method according to claim 7, wherein the thickness of the covering layer is 2 μm or more, and the total thickness of the insulating layer formed by overlapping the main insulating layer and the covering layer is 50 μm or less. Wiring board. An insulating slurry containing at least a resin and a non-spherical inorganic powder,
A step of preparing a coating slurry containing a resin and containing 20% by volume or less of an inorganic powder or containing no inorganic powder, and a main insulating layer formed by a sheet forming method using the insulating slurry among the two slurries. And a step of laminating a coating layer on the surface of the main insulating layer by a sheet forming method using the coating slurry. (A) forming a core laminate formed by forming a conductor wiring layer on at least a surface of an insulating base material containing at least a resin;
(B) a step of thermocompression bonding the insulating layer for a wiring board according to any one of claims 1 to 6 on a surface of the core laminate;
(C) irradiating a predetermined portion of the insulating layer for a wiring board with a laser beam to form a through hole;
(D) filling a through-hole formed in (c) with a conductive paste containing a metal powder and an organic component to form a via conductor;
(E) forming a finely processed wiring circuit layer on the wiring board insulating layer on which the via conductor is formed, and forming a conductor wiring layer having a roughened upper surface side;
And (f) repeating steps (b) to (e) to form a multilayer.

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