JP2002299514A - Electronic part mounting board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic part mounting board where an external connection pad of an electronic part is accurately mounted on a wiring conductor of an external electric circuit board with no electrical shorting between external connection pads. SOLUTION: The thickness of the external connection pad on the lower surface of an insulation board is 15-30 μm. A cross section which is vertical to a side opposed to the external connection pad is trapezoidal. The flatness P in an equation P=D/W×100 (%) is 65-85%, where the length of a lower base of the trapezoid is W (μm), height of the trapezoid is h (μm), width of a part whose height is h-5 μm is D (μm).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component mounting board for mounting electronic components such as a semiconductor element and a piezoelectric vibrator.

[0002]

2. Description of the Related Art Conventionally, electronic component mounting substrates for mounting electronic components such as semiconductor elements and piezoelectric vibrators are, for example,
An electronic component connection pad to which each electrode of the electronic component is electrically connected is adhered on the upper surface of an insulating substrate made of an electrically insulating material such as alumina ceramics and having a mounting portion on which the electronic component is mounted. In addition, external connection pads for electrically connecting the electrodes of the electronic component to the wiring conductors of the external electric circuit board are formed on the lower surface. In addition,
The electronic component connection pad and the external connection pad are electrically connected to each other by a through conductor penetrating the insulating substrate, and the electronic component connection pad, the external connection pad, and the through conductor are, for example, tungsten ( W) and molybdenum (Mo).

In this electronic component mounting board, the electronic component is mounted on the mounting portion on the upper surface of the insulating substrate, and the electrodes of the electronic component are electrically connected to the electronic component connection pads via bonding wires or metal bumps. Then, the electronic component device as a product is obtained by covering and fixing a resin sealing material such as a potting resin and a resin lid so as to cover the electronic component on the upper surface of the insulating substrate. And
By connecting the external connection pads of the electronic component device to the wiring conductors of the external electric circuit board via solder, the electronic component device is mounted on the external electric circuit board and the electrodes of the mounted electronic component are connected to the external electric circuit. Is electrically connected to the

[0004] Such an electronic component mounting board is
Manufactured from ceramic green sheets, specifically,
In addition to drilling through holes for providing through conductors in the ceramic green sheet, electronic component connection pads, external connection pads and metallization paste for through conductors are printed and coated on the upper and lower surfaces of the ceramic green sheet and in the through holes. It is manufactured by filling and firing them at high temperature.

In such an electronic component mounting board, the thickness of the external connection pad is generally 10 to 5 mm.
It is about 0 μm.

[0006]

However, in the above conventional example, when the thickness of the external connection pad exceeds 30 μm, the metallization paste for the external connection pad is printed and applied to the ceramic green sheet for the insulating substrate. However, since the central portion of the thickly printed metallized paste is greatly raised due to surface tension, it has been difficult to print the paste at a constant thickness. Therefore, the thickness variation between the external connection pads becomes large, and the electronic component device is inclined with respect to the external electric circuit board when connecting each external connection pad to the wiring conductor of the external electric circuit board via solder. It will be implemented in the state. As a result, there has been a problem that a displacement occurs between the external connection pad of the electronic component device and the wiring conductor of the external electric circuit board.

On the other hand, the thickness of the external connection pad is 30 μm.
In the following cases, when connecting the external connection pads to the wiring conductors of the external electric circuit board via solder, the gap between the insulating substrate and the external electric circuit board becomes narrow, and therefore, the electronic component device The solder has a problem that the protruding solder is crushed and protrudes due to its own weight, so that protruding solders are contacted between adjacent external connection pads and adjacent external connection pads are likely to be electrically short-circuited. .

Accordingly, the present invention has been completed in view of the above-mentioned conventional problems, and an object of the present invention is to accurately mount an external connection pad of an electronic component device to a wiring conductor of an external electric circuit board without displacement. It is another object of the present invention to provide an electronic component mounting substrate which can be formed without causing an electrical short circuit between the external connection pads.

[0009]

According to the present invention, there is provided a board for mounting an electronic component, wherein an electrode of the electronic component is provided on a lower surface of an insulating substrate having a mounting portion for the electronic component on an upper surface via solder to a wiring conductor of an external electric circuit board. 15 to 3 thickness for electrical connection
An electronic component mounting board having a substantially square external connection pad of 0 μm formed thereon, wherein the external connection pad has a trapezoidal shape in a cross section perpendicular to an opposite side,
When the length of the lower base of the trapezoid is W (μm), the height of the trapezoid is h (μm), and the width of the portion of the trapezoid having a height of h-5 μm is D (μm). , P = D / W × 100 (%)
Is 65 to 85%.

According to the present invention, since the thickness of the external connection pads on the lower surface of the insulating substrate is 15 to 30 μm, the metallized paste of the external connection pads is printed when printed on the ceramic green sheet for the insulating substrate. The printed metallized paste can be printed at a constant thickness without a large swelling, and the thickness variation of each external connection pad can be reduced. Therefore, when connecting each external connection pad to the wiring conductor of the external electric circuit board via the solder, the electronic component device is not mounted in a state inclined with respect to the external electric circuit board.

The external connection pad has a trapezoidal shape in a cross section perpendicular to the opposite side. The length of the bottom of the trapezoid is W (μm), and the height of the trapezoid is h (μm). When the width of a trapezoidal portion having a height of h-5 μm is D (μm), the flatness P expressed by P = D / W × 100 (%)
Is 65 to 85%, when each external connection pad is connected to the wiring conductor of the external electric circuit board via solder, stress is equally applied to each connection portion, and the There is no displacement between each external connection pad and the wiring conductor of the external electric circuit board, and the electronic component device can be accurately mounted on the external electric circuit board.

In the present invention, preferably, an insulating layer having a thickness of 15 to 50 μm is provided on a lower surface of the insulating substrate so as to partition between the external connection pads.

According to the present invention, when the electronic component device using the electronic component mounting board of the present invention is mounted on an external electric circuit board, the solder is crushed by the weight of the electronic component device. Even so, a short circuit due to contact between solders between adjacent external connection pads is effectively prevented by this insulating layer.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS The invention is explained in more detail below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an example of an embodiment of an electronic component mounting board according to the present invention.
FIG. 2 is a bottom view of the electronic component mounting board shown in FIG. 1. In these figures, 1 is an insulating substrate, 4 is an electronic component connection pad, 5 is a through conductor, 6 is an external connection pad, 7 is an insulating layer, and these components are used to mount an electronic component 2. Substrate is mainly configured.

The insulating substrate 1 is made of an electrically insulating material such as alumina ceramics, and has a mounting portion 1a for mounting an electronic component 2 on its upper surface. Is mounted. Insulating substrate 1
Is made of alumina ceramics, for example, an appropriate organic resin binder and a solvent are added to raw material powders such as aluminum oxide, silicon oxide, calcium oxide, and magnesium oxide to form a slurry, and a sheet forming method such as a doctor blade method is used. A plurality of ceramic green sheets are obtained by forming a sheet by adopting the above method. Thereafter, the ceramic green sheets are subjected to appropriate punching and fired at a temperature of about 1600 ° C. in a reducing atmosphere. You.

On the upper surface of the insulating substrate 1, there are formed electronic component connection pads 4 to which respective electrodes of the electronic component 2 are electrically connected. External connection pads 6 for electrically connecting to an external electric circuit board (not shown) are formed on the lower surface of the insulating substrate 1. Further, the insulating substrate 1 has a through conductor 5 for connecting the electronic component connection pad 4 on the upper surface and the external connection pad 6 on the lower surface. These electronic component connection pads 4, external connection pads 6, and through conductors 5
Functions as a conductive path for electrically connecting each electrode of the electronic component 2 mounted on the insulating substrate 1 to an external electric circuit board. Each electrode of the electronic component 2 is connected to the electronic component connection pad 4 through, for example, a bonding wire 3, and the external connection pad 6 is connected to a wiring conductor of an external electric circuit board (not shown) by a conductive adhesive material such as solder 9. Connected via

The electronic component connection pads 4, the external connection pads 6, and the through conductors 5 are formed of a metallized layer obtained by applying and firing a paste of a high melting point metal powder such as W or Mo. It is preferable that a nickel (Ni) plating layer having a thickness of about 1 to 10 μm and a gold (Au) plating layer having a thickness of about 0.1 to 3 μm are sequentially applied. This effectively prevents oxidation corrosion of the electronic component connection pad 4 and the external connection pad 6, and also connects the electronic component connection pad 4 to the bonding wire 3 and the external connection pad 6 to the solder 9. Connection is easy and robust.

The pad 4 for connecting electronic parts, the pad 6 for external connection, and the through conductor 5 are formed by insulating a metallized paste obtained by adding a suitable organic binder and a solvent to a refractory metal powder such as W and mixing the same. The ceramic green sheet for the substrate 1 is printed and applied by a screen printing method or the like, and is baked together with the ceramic green sheet to be formed on the upper and lower surfaces and inside of the insulating substrate 1.

In the present invention, the thickness of the external connection pad 6 is set to 15 to 30 μm. This allows
There is an important effect that the thickness variation of the external connection pad 6 can be reduced. That is, the external connection pad 6
Is connected to the wiring conductor of the external electric circuit board via the solder 9, the electronic component device can be accurately mounted on the external electric circuit board without tilting.

The thickness of the external connection pad 6 is 15 μm.
If it is less than m, the bonding strength between the external connection pad 6 and the insulating substrate 1 decreases, and when the external connection pad 6 and the wiring conductor of the external electric circuit board are connected via the solder 9, the external connection pad 6 It becomes easy to peel from the lower surface of the insulating substrate 1. On the other hand,
If the thickness of the external connection pad 6 exceeds 30 μm, when the metallized paste for the external connection pad 6 is applied to the ceramic green sheet for the insulating substrate 1 by printing, the central portion of the thickly printed metallized paste has a surface tension. Therefore, each metallized paste is not printed to a certain thickness. For this reason, the thickness variation of the external connection pads 6 increases, and when mounting the electronic component device using the electronic component mounting board on the external electrical circuit board, the electronic component device is inclined with respect to the external electrical circuit board. In this case, misalignment easily occurs between the external connection pad 6 of the electronic component device and the wiring conductor of the external electric circuit board.

Further, as shown in FIG. 3, the external connection pad 6 has a trapezoidal shape in a cross section perpendicular to the opposite side, and the length of the lower base of the trapezoidal shape is W (μm). When the height is h (μm) and the width of the trapezoidal portion having a height of h−5 μm is D (μm), P = D / W × 100
The flatness P expressed by (%) is 65 to 85%.
If it is less than 65%, thickness variation among the external connection pads 6 occurs, and when connecting the external connection pads 6 to the wiring conductors of the external electric circuit board via solder, the electronic component device is connected to the external electric circuit board. It will be mounted in an inclined state. As a result, the external connection pads 6 of the electronic component device are
And the wiring conductor of the external electric circuit board is likely to be displaced. If it exceeds 85%, the thickness of the external connection pad 6 must be less than 15 μm, and the bonding strength between the external connection pad 6 and the insulating substrate 1 decreases,
When connecting the external connection pad 6 to the wiring conductor of the external electric circuit board via the solder 9, the external connection pad 6 is easily peeled off from the lower surface of the insulating substrate 1.

On the lower surface of the insulating substrate 1, an insulating layer 7 made of an electrically insulating material such as alumina ceramic is applied so as to partition between the external connection pads 6. The insulating layer 7 is formed, for example, by printing a ceramic paste containing substantially the same ceramic raw material powder as the ceramic green sheet for the insulating substrate 1 on the ceramic green sheet for the insulating substrate 1 in a predetermined pattern by a screen printing method or the like. It is applied and baked together with the ceramic green sheet for the insulating substrate 1 to form an adhered layer. When the external connection pad 6 is connected to the wiring conductor of the external electric circuit board via the solder 9 by the solder 9 crushed by the own weight of the electronic component device, the insulating layer 7 forms the adjacent external connection pad 6. It functions as a dam member for preventing an electrical short circuit between them. Thereby, the mounted electronic component 2 can be operated normally.

The thickness of the insulating layer 7 is preferably 15 to 50 μm. If the thickness is less than 15 μm, the solder 9 crushed by the weight of the electronic component device will run over the insulating layer 7, and there is a high risk that the solder of the adjacent external connection pads 6 will contact and short-circuit. On the other hand, if it exceeds 50 μm, it becomes difficult to form the insulating layer 7 by a screen printing method or the like.

Further, it is preferable that the thickness of the insulating layer 7 is formed thicker than the thickness of the external connection pad 6,
In this case, an electrical short circuit between the external connection pads 6 can be effectively prevented.

The insulating layer 7 also has the effect that it can be used for positioning the mounting height when the external connection pads 6 are mounted on the wiring conductors of the external electric circuit board by soldering.

Thus, according to the present invention, after the electrodes of the electronic component 2 are electrically connected to the electronic component connection pads 4 via the bonding wires 3, a potting resin, a resin lid or the like is formed on the upper surface of the insulating substrate 1. An electronic component device as a product is obtained by covering or fixing the resin sealing material.

The present invention is not limited to the above embodiment, and various changes may be made without departing from the gist of the present invention.

[0028]

According to the present invention, when the thickness of the external connection pad on the lower surface of the insulating substrate is 15 to 30 μm, the metallizing paste for the external connection pad is printed on the ceramic green sheet for the insulating substrate. The printed metallized paste can be printed to a constant thickness without a large swelling, and the thickness variation of the external connection pads can be reduced. The shape of the cross section perpendicular to the opposite side of the external connection pad is trapezoidal, the length of the lower base of the trapezoid is W (μm), and the height of the trapezoid is h (μm).
m), and the width of the trapezoidal portion having a height of h-5 μm is D (μm).
m), the flatness P expressed by P = D / W × 100 (%) is set to 65 to 85%, so that the external connection pads of the electronic component device and the wiring conductors of the external electric circuit board are provided. The electronic component device can be accurately mounted on the external electric circuit board without causing a displacement between the electronic component device and the electronic component device.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an embodiment of an electronic component mounting board of the present invention.

FIG. 2 is a bottom view of the electronic component mounting board of FIG. 1;

FIG. 3 is a cross-sectional view of an external connection pad for explaining flatness P.

[Explanation of symbols]

 1: Insulating board 1a: Mounting section 2: Electronic component 4: Pad for connecting electronic component 5: Through conductor 6: Pad for external connection 7: Insulating layer 9: Solder

Claims (2)

[Claims] An insulating substrate having an electronic component mounting portion on an upper surface has a thickness of 1 for electrically connecting electrodes of the electronic component to wiring conductors of an external electric circuit board via solder on a lower surface of the insulating substrate.
What is claimed is: 1. A substrate for mounting electronic components, comprising a substantially square external connection pad of 5 to 30 μm, wherein the external connection pad has a trapezoidal shape in a cross section perpendicular to an opposite side. When the length of the lower base is W (μm), the height of the trapezoid is h (μm), and the width of a portion of the trapezoid having a height of h-5 μm is D (μm), P = D / W × 100
An electronic component mounting substrate, wherein a flatness P expressed by (%) is 65 to 85%. 2. The electronic component mounting substrate according to claim 1, wherein an insulating layer having a thickness of 15 to 50 μm is provided on a lower surface of the insulating substrate so as to partition between the external connection pads.