JP2004221388A - Multilayer circuit board for mounting electronic component and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer circuit board for mounting an electronic component, which has high reliability even if the electronic component is directly joined to a via hole having no connection pad, and to provide its manufacturing method. <P>SOLUTION: In the multilayer circuit board 10 for mounting the electronic component, a through hole 12 is provided in an insulator 11 as at least one uppermost layer of a plurality of the insulators 11, and an electronic component 16 is mounted outside the via hole 15 formed by charging a conductive metal 14 in the through hole 12. A tapered part 13 which has a larger internal diameter of the through hole 12 than an external diameter thereof as viewed in cross section is formed, and moreover in the outside of and a peripheral part of the outside of the via hole 15, the electronic component 16 is directly joined to the outside of the via hole 15 through a joining material 18 without having the connection pad for mounting the electronic component 16. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２１】
ビアホールの引っ張り強度は、実施例のテーパ角度が１．８°以上のサンプル１、２、３の場合には、１３．８３Ｎ程度より大きい強度を有し、比較例のテーパ角度が１．８°を下まわるサンプル４、５の場合には、１０．５９Ｎ程度より小さい強度を有している。ビアホールは、実施例のテーパ角度１．８°以上において十分な引っ張り強度が得られることが確認できた。
【００２２】
【発明の効果】
請求項１及びこれに従属する請求項２記載の電子部品搭載用多層基板は、貫通孔の壁面に、貫通孔の外部側の径よりも内部側の径のほうが大きい断面視してテーパ部が形成されており、しかも、ビアホールの外部側及び外部側周辺部には、電子部品を実装するための接続用パッドを有さないで電子部品がビアホールの外部側に接合材を介して直接接合されるので、導体金属は、貫通孔から抜けにくくなり、半導体素子や、コンデンサ等の電子部品をビアホールに直接接合しても接続信頼性を向上することができる。
【００２３】
特に、請求項２記載の電子部品搭載用多層基板は、テーパ部が貫通孔の垂直方向に対するテーパ角度として１．８°以上に形成されているので、導体金属が抜け出す方向に抵抗する効果が十分に発揮でき、確実に接続信頼性を向上させることができる。なお、テーパ角度が１．８°を下まわると、導体金属が貫通孔から抜けやすくなるのを防止する効果が小さくなる。
【００２４】
請求項３記載の電子部品搭載用多層基板の製造方法は、絶縁基体の一方の主面にレーザー光を照射し、レーザー光が当接する側の貫通孔の径を大きく、レーザー光が抜ける側の貫通孔の径を小さく穿孔して貫通孔の側壁にテーパ部を形成する工程と、貫通孔内に導体金属を充填して、ビアホールを形成する工程と、ビアホールの小径側が少なくとも一方の最表層の絶縁基体の外部側になるように複数の絶縁基体を積層する工程を有するので、レーザーによって１枚の絶縁基体の中にテーパ部を形成でき反りや変形が発生しない電子部品搭載用多層基板にすることができる。また、絶縁基体にフィルム付を用いる必要がないので、絶縁基体にフィルムの滓を付着させるような問題を防止することができる。
【図面の簡単な説明】
【図１】本発明の一実施の形態に係る電子部品搭載用多層基板の説明図である。
【図２】（Ａ）〜（Ｃ）はそれぞれ同電子部品搭載用多層基板の製造方法の説明図である。
【図３】（Ａ）、（Ｂ）はそれぞれ従来の電子部品搭載用多層基板の貫通孔の形成方法の説明図である。
【図４】従来の電子部品搭載用多層基板に電子部品を接合する説明図である。
【符号の説明】
１０：電子部品搭載用多層基板、１１：絶縁基体、１２：貫通孔、１３：テーパ部、１４：導体金属、１５：ビアホール、１６：電子部品、１７：電極パッド、１８：接合材、１９：配線パターン[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a multilayer board for mounting electronic components, in which electronic components such as semiconductor elements and capacitors are mounted in via holes provided in an outermost insulating substrate, and a method of manufacturing the same.
[0002]
[Prior art]
In recent years, a multilayer substrate for mounting electronic components formed by laminating a plurality of insulating substrates made of ceramic green sheets or plastic substrates, for example, includes a semiconductor element directly on a via hole of the outermost insulating substrate, such as soldering. In this case, a multi-layer substrate for mounting electronic components whose outer dimensions are substantially equal to those of a semiconductor element is used. This makes it possible to reduce the size of the entire device incorporating the electronic component mounting multilayer substrate, and at the same time, to shorten the wiring length of the electronic component mounting multilayer substrate mounting the electronic components, thereby improving the electrical characteristics. be able to. Also, electronic parts such as capacitors are directly joined to the via holes to shorten the wiring length.
[0003]
As shown in FIGS. 3A and 3B, a through-hole 51 for a via hole of an insulating base 50 used for a conventional multilayer substrate for mounting electronic components is insulated by a punching method including a pin 52 and a die 53, for example. The base 50 is mounted on a die 53 and formed by punching with a pin 52. Alternatively, in the case of the through hole 51 of the insulating base 50 made of a plastic substrate, the through hole 51 can be formed by a rotation method using a drill (not shown) instead of the pin 52. Each of the through holes 51 is formed in a straight line substantially perpendicular to the thickness direction. The electronic component mounting multilayer substrate made of ceramic is formed by filling a through hole 51 formed in the ceramic green sheet with a conductive metal paste by screen printing or the like to form a via hole 54 (see FIG. 4). After lamination, they are fired. In addition, a multilayer board for mounting electronic components made of a plastic substrate is formed by forming a conductor on the wall of the through-hole formed in the plastic substrate, for example, by plating, and then screen-printing a thermosetting conductive metal resin paste. The via hole 54 is formed by filling with a material and the like, and the via hole 54 is formed by heating.
[0004]
As shown in FIG. 4, a semiconductor element and a capacitor are provided on the outer side of the via hole 54 in which the through-hole 51 of the outermost insulating base 50 is filled with the conductive metal and at the periphery thereof, as shown in FIG. A connection pad 58 using a conductive metal is formed in order to join an electrode pad 56 of an electronic component 55 such as an electronic component through a joining material 57 such as solder. When the through-hole 51 is straight and the conductor metal filled in the through-hole 51 has a void or the like when the through-hole 51 is straight, the conductor metal is easily removed due to thermal stress or vibration, and is mounted. This prevents problems such as the detachment of the electronic component 55 that has come off.
[0005]
In order to prevent the mounted semiconductor element from coming off, a step is provided so as to have a boundary surface in the horizontal direction in the middle of the through hole of the insulating substrate on the outermost layer. It has been proposed that the diameter of the inner side is made larger than the diameter of the side, and a semiconductor element is mounted in a via hole formed by filling a through hole with a conductive metal (for example, see Patent Document 1).
[0006]
Further, the method of forming the through hole is a method of irradiating a laser beam to the ceramic green sheet side of the ceramic green sheet with a film to form a through hole in the ceramic green sheet, and further forming a recess to a depth halfway through the film. Has been proposed. The formation of the conductor metal in the through-hole is performed by filling the conductor metal halfway into the recess and then peeling off the film. Thus, it has been proposed to suppress the generation of the residual conductive metal on the film side (for example, see Patent Document 2).
[0007]
[Patent Document 1]
Japanese Patent No. 3102287 (pages 1-5, FIG. 1)
[Patent Document 2]
JP 2001-148570A (pages 1-4, FIG. 1)
[0008]
[Problems to be solved by the invention]
However, the conventional multilayer board for mounting electronic components and the method of manufacturing the same as described above have the following problems.
(1) Providing connection pads in via holes in order to join electronic components such as semiconductor elements to via holes in which conductive metal is filled into straight through holes can improve connection reliability, and can provide thermal stress and vibration. It has the effect of preventing the conductor metal from easily coming off due to such factors as the like.However, with the recent miniaturization of the device, the miniaturization of the multilayer board for mounting electronic components is also required, and it is necessary to provide connection pads. Are becoming more difficult in design.
(2) The provision of through-holes having different diameters in an insulating base made of a single ceramic green sheet is because, when the through-hole is formed, an extreme load is partially applied to the step portion, and the local density of the ceramic green sheet is partially increased. Due to the difference, after firing, the electronic component mounting multilayer substrate is warped or deformed.
(3) When a ceramic green sheet with a film is perforated by a laser, the quality of the film and the yield are reduced because the residue of the film melted by the laser adheres to the ceramic green sheet. In particular, since no through-hole is formed in the film, the molten film residue easily adheres to the peripheral portion of the through-hole of the ceramic green sheet.
The present invention has been made in view of the above circumstances, and provides a multilayer board for mounting electronic components having high connection reliability even when electronic components are directly bonded to via holes having no connection pads, and a method of manufacturing the same. The purpose is to do.
[0009]
[Means for Solving the Problems]
A multilayer board for mounting electronic components according to the present invention, which meets the above object, has a via hole formed by filling a through hole in an insulating substrate that is an outermost layer of at least one of a plurality of insulating substrates and filling the through hole with a conductive metal. In a multilayer board for mounting electronic components on which electronic components are mounted on the outside, a tapered portion is formed on the wall surface of the through hole in a cross-sectional view where the diameter of the inside of the through hole is larger than the diameter of the outside of the through hole. In addition, the electronic component is directly bonded to the outside of the via hole via a bonding material without having a connection pad for mounting the electronic component on the outer side and the outer peripheral portion of the via hole. As a result, the conductive metal filled in the through hole can be prevented from easily coming off from the through hole by the tapered portion formed in the through hole, so that electronic components such as a semiconductor element and a capacitor can be directly transferred to the via hole. Even if they are joined, the connection reliability can be improved.
[0010]
Here, in the multilayer board for mounting electronic components, the tapered portion is preferably formed to have a taper angle of 1.8 ° or more with respect to the vertical direction of the through hole. Thus, if the taper portion has a taper angle of 1.8 ° or more with respect to the vertical direction of the through hole, the effect of resisting the direction in which the conductive metal comes out can be sufficiently exhibited, and the connection reliability can be reliably improved. it can. If the taper angle is less than 1.8 °, the via hole becomes too close to vertical, and the force of resisting the direction in which the conductive metal comes out becomes small, so that the conductive metal easily comes out of the through hole.
[0011]
A method for manufacturing a multilayer board for mounting electronic components according to the present invention, which meets the above object, comprises forming a through-hole in an insulating substrate that is the outermost layer of at least one of a plurality of insulating substrates, and filling the through-hole with a conductive metal. In a method of manufacturing an electronic component mounting multilayer substrate for mounting an electronic component on the outside of a via hole, a laser beam is irradiated on one main surface of the insulating base, and the diameter of the through hole on the side where the laser beam contacts is increased. A step of forming a tapered portion on the side wall of the through-hole by drilling a small diameter of the through-hole on the side from which the laser light exits, a step of filling the through-hole with a conductive metal and forming a via hole, and a small-diameter side of the via hole. A step of laminating a plurality of insulating bases so as to be on the outer side of at least one outermost insulating base. As a result, a tapered portion can be formed in one insulating substrate by a laser. For example, even when the insulating substrate is a ceramic green sheet, there is no difference in green density in the sheet, so that warpage or deformation occurs. A multilayer board for mounting electronic components, which does not generate any, can be obtained. Further, even when the insulating substrate is a ceramic green sheet, there is no need to use a ceramic green sheet with a film, so that there is no problem of adhering film residue to the ceramic green sheet.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention.
FIG. 1 is an explanatory diagram of a multilayer board for mounting electronic components according to an embodiment of the present invention, and FIGS. 2A to 2C are diagrams illustrating a method of manufacturing the multilayer board for mounting electronic components. is there.
[0013]
As shown in FIG. 1, a multilayer substrate 10 for mounting an electronic component according to an embodiment of the present invention is obtained by laminating a plurality of insulating bases 11 of ceramic green sheets made of, for example, alumina or low-temperature fired ceramic. It is formed by firing. The electronic component mounting multilayer substrate 10 can also be formed by laminating a plurality of insulating substrates 11 made of a plastic substrate in multiple layers using a prepreg or the like. A through hole 12 is provided in the insulating substrate 11, which is the outermost surface of at least one of the plurality of insulating substrates 11, and a diameter A on the outer side of the through hole 12 The tapered portion 13 is formed in a cross-sectional view where the relationship with the diameter B on the side satisfies A <B. For example, when the insulating base 11 is made of alumina, the through-hole 12 is filled with a conductive metal 14 made of a high melting point metal such as tungsten or molybdenum. When the insulating base 11 is made of a plastic substrate, the conductive metal 14 made of a metal paste made of a metal paste such as silver or copper is used. The via hole 15 is formed by filling.
[0014]
A general multilayer board for mounting electronic components, for example, when mounting a semiconductor element in a via hole by a flip chip method, has a semiconductor element connection pad on the surface of the insulating base on the outer side of the via hole and on the outer peripheral part. ing. However, on the outer side of the via hole 15 of the electronic component mounting multilayer substrate 10 according to one embodiment of the present invention, and on the surface of the insulating base 11 around the outer side, an electronic component 16 such as a semiconductor element or a capacitor is provided. Does not have connection pads for connection. Thus, the electronic component mounting multilayer substrate 10 can cope with high-density design, and thus can cope with miniaturization of external dimensions. The electronic component 15 is directly bonded to an electrode pad 17 provided on the electronic component 15 via a bonding material 18 such as solder outside the via hole 15 of the electronic component mounting multilayer substrate 10.
[0015]
The through hole 12 for forming the via hole 15 of the electronic component mounting multilayer substrate 10 preferably has a taper angle of the angle α with respect to the vertical direction of the through hole of 1.8 ° or more. When the taper angle is 1.8 ° or more, even if thermal stress or mechanical stress such as vibration is generated in the electronic component mounting multilayer substrate 10, the external component on the side to which the electronic component 15 is joined is formed. Since the relationship between the diameter A on the side and the diameter B on the other side on the opposite side is a taper portion where A <B, resistance acts in the direction in which the conductor metal 14 falls off from the through-hole 12, thereby preventing the conductor metal 14 from falling off. it can.
[0016]
Next, with reference to FIGS. 2A to 2C, a method for manufacturing the multilayer board 10 for mounting electronic components according to an embodiment of the present invention will be described.
As shown in FIG. 2A, a YAG laser, a carbon dioxide gas laser, or the like is provided on one main surface of an insulating substrate 11 which is at least one outermost layer made of a plurality of ceramic green sheets, a plastic substrate, or the like. Using a laser beam machine, the insulating substrate 11 is irradiated with a laser beam so that the diameter B of the through hole 12 on the side where the laser beam comes into contact is large and the diameter A of the through hole 12 on the side where the laser beam exits is small. A through hole 12 having a tapered portion 13 is formed on the side wall of the substrate.
[0017]
Next, as shown in FIG. 2B, by using screen printing or the like in the through holes 12 of the insulating base 11, for example, when the insulating base 11 is a high-temperature fired ceramic such as alumina, tungsten or molybdenum is used. A via hole 15 is formed by filling a metal conductor paste made of a high melting point metal such as the above. Further, for example, when the insulating base 11 is a low-temperature fired ceramic, the via hole 15 is formed by filling a conductive metal paste made of a low melting point metal such as silver, a silver alloy, or copper. Further, for example, when the insulating base 11 is a plastic substrate, a via hole 15 is formed by filling a conductive metal paste made of silver, copper, or the like. When the insulating base 11 is a high-temperature fired ceramic or a low-temperature fired ceramic, after forming the via hole 15, a wiring pattern 19 (see FIG. 2C) is formed on the surface of the insulating base 11 as necessary. . When the insulating base 11 is a plastic substrate, the via hole 15 is formed after the wiring pattern 19 is formed by plating, etching, or the like.
[0018]
Next, the plurality of insulating bases 11 are overlapped with each other so that the small diameter side of the via hole 15 is located outside the at least one outermost insulating base 11, for example, when the insulating base 11 is ceramic, Press and laminate under pressure. When the insulating substrate 11 is a plastic substrate, the insulating substrate 11 is laminated by pressing with temperature and pressure with a prepreg or the like interposed therebetween. In the case where the insulating base is a ceramic, after lamination, it is fired to produce a multilayer substrate 10 for mounting a semiconductor element.
[0019]
【Example】
The present inventor uses a ceramic green sheet having a thickness of 0.4 mm (two sheets each having a thickness of 0.2 mm) made of a low-temperature fired ceramic as an insulating base, and using a carbon dioxide laser processing machine, A through hole having a diameter A of the smaller side of φ0.25 mm and taper angles of 1.8 °, 3.9 °, and 6.3 ° is formed, and a conductive metal made of silver is filled in the through hole to form a via hole. Was formed and calcined to produce Samples 1, 2, and 3 of the examples. At the same time, a through hole with a taper angle of 3.9 ° using a carbon dioxide laser beam machine and a taper rate of −3.3 ° with the upper and lower surfaces reversed, and a substantially conventional press machine with a press machine. Samples 4 and 5 of comparative examples each having a straight through-hole having a taper angle of 0.7 ° were produced. In the above samples 1 to 5, the taper ratios of the diameter A on the smaller side of the through hole and the ratio A / B on the larger side are 95%, 90%, 85%, 110%, and 98%, respectively. %Met. The selection of the taper angle by the laser processing machine is determined by the material of the insulating substrate, the aspect ratio (the ratio of the hole diameter to the thickness of the insulating substrate), and the conditions of the processing machine. For the samples of the examples and the comparative examples manufactured as described above, a metal wire was soldered to the via hole, and the sample was pulled in a direction perpendicular to the through hole to measure the strength. Table 1 shows the measurement results.
[0020]
[Table 1]

[0021]
As for the tensile strength of the via hole, the samples 1, 2, and 3 having a taper angle of 1.8 ° or more in the example have a strength larger than about 13.83 N, and the taper angle in the comparative example is 1.8 °. In the case of Samples 4 and 5 having a strength lower than the above, the strength is smaller than about 10.59 N. It was confirmed that the via hole had a sufficient tensile strength at the taper angle of 1.8 ° or more in the example.
[0022]
【The invention's effect】
In the multilayer board for mounting electronic components according to claim 1 and dependent on claim 2, the wall surface of the through-hole has a tapered portion in a cross-sectional view in which the diameter on the inner side is larger than the diameter on the outer side of the through-hole. In addition, the electronic component is directly bonded to the outside of the via hole via a bonding material without having a connection pad for mounting the electronic component on the outer side and the outer peripheral portion of the via hole. Therefore, the conductive metal is less likely to come out of the through hole, and the connection reliability can be improved even when an electronic component such as a semiconductor element or a capacitor is directly joined to the via hole.
[0023]
In particular, in the electronic component mounting multilayer substrate according to the second aspect, since the tapered portion is formed at a taper angle of 1.8 ° or more with respect to the vertical direction of the through hole, the effect of resisting the direction in which the conductive metal escapes is sufficient. And connection reliability can be reliably improved. When the taper angle is less than 1.8 °, the effect of preventing the conductive metal from easily coming out of the through hole is reduced.
[0024]
According to a third aspect of the present invention, there is provided a method of manufacturing a multilayer substrate for mounting electronic components, wherein one of the main surfaces of the insulating base is irradiated with laser light, the diameter of the through hole on the side where the laser light comes into contact is increased, and Forming a tapered portion on the side wall of the through-hole by drilling a small diameter of the through-hole, filling a conductive metal in the through-hole, and forming a via hole; and forming the via hole on the small diameter side of at least one outermost layer. Since there is a step of laminating a plurality of insulating substrates so as to be on the outer side of the insulating substrate, a tapered portion can be formed in one insulating substrate by a laser so that a multilayer substrate for mounting electronic components which does not warp or deform. be able to. Further, since it is not necessary to use a film attached to the insulating base, it is possible to prevent a problem that film residue is attached to the insulating base.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a multilayer board for mounting electronic components according to an embodiment of the present invention.
FIGS. 2A to 2C are explanatory views of a method of manufacturing the electronic component mounting multilayer substrate. FIGS.
FIGS. 3A and 3B are explanatory views of a method of forming a through hole in a conventional multilayer board for mounting electronic components.
FIG. 4 is an explanatory view for bonding an electronic component to a conventional multilayer board for mounting electronic components.
[Explanation of symbols]
10: multilayer substrate for mounting electronic components, 11: insulating base, 12: through hole, 13: tapered portion, 14: conductive metal, 15: via hole, 16: electronic component, 17: electrode pad, 18: bonding material, 19: Wiring pattern

Claims (3)

An electronic component mounting method in which a through hole is provided in the insulating substrate, which is the outermost layer of at least one of the plurality of insulating substrates, and an electronic component is mounted outside a via hole formed by filling the through hole with a conductive metal. In a multilayer board,
On the wall surface of the through-hole, a tapered portion is formed in a cross-sectional view in which the diameter on the inner side is larger than the diameter on the outer side of the through-hole. A multi-layer substrate for mounting an electronic component, wherein the electronic component is directly bonded to the outside of the via hole via a bonding material without having a connection pad for mounting the electronic component. 2. The electronic component mounting multilayer board according to claim 1, wherein the tapered portion is formed to have a taper angle with respect to a vertical direction of the through hole of 1.8 ° or more. A multilayer board for mounting electronic components, wherein a through-hole is provided in the insulating base, which is the outermost layer of at least one of the plurality of insulating bases, and an electronic component is mounted outside a via hole formed by filling the through-hole with a conductive metal. In the manufacturing method of
One main surface of the insulating base is irradiated with laser light, and the diameter of the through hole on the side contacted with the laser light is increased, and the diameter of the through hole on the side from which the laser light exits is reduced. Forming a tapered portion on the side wall of the hole;
Filling the conductive metal in the through hole to form the via hole;
A method of manufacturing a multilayer board for mounting electronic components, comprising a step of laminating a plurality of insulating bases so that the small diameter side of the via hole is at least one outermost layer outside the insulating base.

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