JP2002359475A - Multilayer circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer circuit board, the whole body of which can be mounted to high density and in which a cavity can be sealed airtightly. SOLUTION: This multilayer circuit board 10 is composed of a multilayered substrate 1 on the surface of which surface wiring layers 2 are formed, and at the same time, in which a cavity 7, having an opening on the surface of the substrate 1, is formed and a metal lid body 6 which seals the opening of the cavity 7 housing an electronic component element or an IC chip 5. On the surface of the lid body 6, an insulation layer 61 is formed to adhere to the surface and a surface circuit pattern 62 is formed on the layer 61.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer circuit board in which a cavity for an electronic component provided in the multilayer board is covered with a metal cover.

[0002]

2. Description of the Related Art For example, a multilayer circuit board containing an electronic component element such as a surface acoustic wave filter or an IC chip in a cavity is provided with an insulating cover to protect the electronic component element and the IC chip from dust and moisture. And a metal lid.

[0003] Such a multilayer circuit board is generally provided with a cavity having an opening in the surface of the surface of the multilayer board,
Electronic components such as surface acoustic wave filters and IC chips are mounted on the bottom surface of the cavity and hermetically sealed.
Moreover, other circuit components such as ICs and capacitors are mounted on the surface around the cavity opening. Then, the cavity opening is simply sealed with an insulating lid or a metal lid with a lid. For this reason, on the surface of the multilayer substrate, the lid portion hinders the mounting of circuit components, and as a result, there is a limit to the high-density mountability of the multilayer circuit substrate.

Conventionally, as shown in FIGS. 4 and 5, the insulating lid 46 is formed of a single-plate substrate or a multilayer substrate made of an insulating material, and the surface of the insulating lid 46 is provided with a predetermined surface circuit pattern. 42 was formed. Further, other circuit components 60 such as an IC and a capacitor are mounted on the surface circuit pattern 42 (Japanese Patent No. 2682477).

[0005]

However, according to the multilayer circuit board 40, the connection between the surface circuit pattern 42 on the insulating lid 46 and a predetermined circuit network of the multilayer board 2 is made on the back surface of the insulating lid 46. I was going. That is, the electrode pad 74 connected to the internal wiring layer 4 is formed in the step 7a of the cavity 7, and is electrically connected to the electrode pad 74.

With such a structure, it has been difficult to achieve a sufficient function as a lid for hermetically sealing the opening of the cavity 7. That is, the opening of the cavity 7 is completely sealed on the back surface of the lid 46, and the circuit on the lid side and the circuit on the multilayer substrate side cannot be electrically connected with high reliability on the back surface of the lid. Was.

First, the connection state between the connection pad 44 on the back surface of the lid 46 and the electrode pad 74 which is the contact portion between the circuit on the multilayer substrate side cannot be visually confirmed. Also, the lid 4
This is because, when the sealing is to be performed simultaneously on the back surface of No. 6, a short circuit may occur in the above-described connection portion, or an open state may occur. If the above-described electrical connection and the sealing of the lid 46 are to be performed simultaneously at the step of the cavity 7, the width of the step must be increased.
As a result, the entire multilayer substrate becomes large.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a multilayer circuit board capable of high-density mounting of the entire multilayer circuit board and capable of hermetically sealing a cavity. Is to provide.

[0009]

According to the present invention, there is provided a multilayer circuit board having a surface wiring layer formed on a surface thereof and a cavity formed therein for accommodating an electronic component element or an IC chip having an opening on the surface. A multilayer circuit board comprising a metal lid for sealing the opening of the cavity,
The metal lid is a multilayer circuit board having a surface circuit pattern formed on the surface thereof with an insulating layer interposed therebetween.

Further, the surface wiring layer and the surface circuit pattern are electrically connected.

Further, the electrical connection between the surface wiring layer and the surface circuit pattern is made by bonding wires.

Further, a step is provided around the inner wall of the cavity, and a metal cover is placed on the step, and at least one pair of the metal cover and the multi-layer substrate is straddled. A chip-shaped electronic component having terminal electrodes is arranged, and one terminal electrode is electrically connected to the surface wiring layer, and the other terminal electrode is electrically connected to the surface circuit pattern.

In addition, a seal conductor film is formed on the step, and the back surface of the metal lid is joined to the seal conductor film.

In addition, a seal conductor film is formed around the opening of the cavity, and the back surface of the metal lid is joined to the seal conductor film.

In the present invention, a surface wiring layer is formed on the surface of the multilayer substrate, a surface insulating layer is formed on the surface of the metal cover, and a surface circuit pattern is formed on the insulating layer. ing. Accordingly, since a predetermined circuit can be formed on the entire surface of the multilayer circuit board, the density of the surface wiring and circuit components can be increased, and the size can be reduced.

Further, since the connection between the surface circuit pattern of the metal cover and the surface wiring layer of the multilayer board is made on the front side of the insulating cover, the electrical connection state can be visually confirmed. Connection reliability is improved. By connecting the connection between the surface wiring layer and the surface circuit pattern to the circuit function of the chip-like component, a predetermined circuit is formed and at the same time, the connection between the two is performed.

Further, the back surface of the metal lid can be used as it is in a region for hermetically sealing the cavity. That is,
Hermetically sealing can be performed without performing any processing on the back surface of the metal lid. For example, when low-melting glass or thermosetting resin is used for the sealing member, no special treatment is required on the multilayer substrate side. When solder or the like is used for the seal member, a seal conductor film is formed on the multilayer substrate side. In any case, the hermetic sealing in the cavity can be easily performed by a very simple operation, and it is particularly suitable for a multilayer substrate that accommodates a surface acoustic wave element whose characteristics fluctuate greatly with changes in environment.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a multilayer circuit board according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is an external perspective view of a multilayer circuit board according to the present invention. FIG. 2 is a sectional view of the multilayer circuit board of FIG.

FIG. 1 is an external perspective view of a multilayer circuit board according to the present invention. FIG. 2 is a sectional view of the multilayer circuit board of FIG.

In the figure, a multilayer substrate 1 is made of ceramic,
Insulating layers 1a to 1f made of glass-ceramic material or the like are laminated, and an internal wiring layer 4 forming a predetermined circuit network is arranged between the insulating layers 1a to 1f. The internal wiring layer 4 has a predetermined function other than the wiring network, such as a counter electrode that forms a capacitance component, a coil pattern that forms an inductance, and a microstrip line. Also, via-hole conductors 3 are formed in the insulating layers 1a to 1f so as to penetrate the layers in the thickness direction.

Further, a surface wiring layer 2 is formed on the surface of the multilayer substrate 1, and a circuit component 8 constituting a predetermined circuit is mounted thereon. The surface wiring layer 2, the via-hole conductor 3, and the internal wiring layer 4 are made of an Ag-based material (Ag alone, Ag-P
d, an Ag alloy such as Ag-Pt) as a main component.

The multilayer substrate 1 has a cavity 7 having a surface opening. An electronic component element such as a surface acoustic wave filter 5 and I
A C chip is mounted. On the inner wall of the cavity 7, a step portion 7a is provided around the entire circumference. The step 7a is a portion that supports the metal lid 6. Then, the metal lid 6 is placed on the step 7a, and the opening of the cavity 7 is sealed. For example, a seal conductor film 64 made of a conductor such as Ag is formed on the step 7 a of the cavity 7, and a seal such as solder is provided between the seal conductor film 64 and the lower surface of the metal lid 6. The inside of the cavity 7 is kept airtight by being sealed by the member 73. In addition, the back surface of the metal lid 6 may be covered with the resin coating layer 65 except for the portion to which the solder adheres, if necessary, so that the solder does not spread.

A surface insulating layer 61 is formed on the surface of the metal lid 6.
A predetermined surface circuit pattern 62 is formed.

The surface insulating layer 61 is made of a resin having a low relative dielectric constant, such as an amine resin or an epoxy resin, in order to improve high-speed electric signal propagation characteristics. Surface insulating layer 61
Has a thickness of several μm to several tens μm. The surface circuit pattern 62 on the surface insulating layer 61 is desirably made of Cu, which is an inexpensive and low-resistance material. In order to increase the formation density of the surface circuit pattern 62, the surface insulating layer 61 and the surface circuit pattern 62 may have a multilayer structure.

The surface wiring layer 2 of the multilayer substrate 1 and the surface circuit pattern 62 of the metal cover 6 are electrically connected via bonding wires 63. In this case,
As shown in FIG. 3, a step is not provided in the cavity 7 and the metal cover 6 is coated on the surface of the multilayer substrate 1, as shown in FIG.
This is effective when a step occurs between the surface of the multilayer substrate 1 and the surface of the metal lid 6. As shown in FIGS. 1 and 2, the metal lid 6 is placed on the step 7a of the cavity 7 so that the surface of the multilayer substrate 1 and the surface of the metal lid 6 are flush with each other. Is to electrically connect the surface wiring layer 2 of the multilayer substrate 1 and the surface circuit pattern of the metal lid 6 using the above-described bonding wires 63, and to extend over the multilayer substrate 1 and the lid 6. The chip-shaped electronic components 70 having at least a pair of terminal electrodes mounted thereon may be electrically connected. That is, one of the at least one pair of terminal electrodes is connected to a part of the surface wiring layer 2 of the multilayer substrate 1, and the other terminal electrode is connected to a part of the predetermined surface circuit pattern 62 on the metal cover 6.

Thus, the surface wiring layer 2 on the side of the multilayer substrate 1 and the surface circuit pattern 62 of the metal cover 6 are electrically connected by the circuit function of the chip-shaped electronic component 70. For example, if the chip-shaped electronic component 70 is a multilayer ceramic capacitor, both can be connected by a capacitor component. In the case of a chip resistor, both can be connected by a resistance component. If it is a chip coil component, both can be connected by a coil component. ball,
If it is a chip jumper part, both can be connected by a simple conductor. Furthermore, this chip-shaped electronic component 70
For example, a transistor or a composite component having three or more terminals may be used.

The inner wall of the cavity 7 has a step 7
a is provided all around. A seal conductor film 64 is provided on the step 7a. Around the back surface of the metal lid 6, it is joined via a seal member 73 such as solder to a seal conductor film 64 provided on the entire periphery of the step 7 a of the cavity 7. In addition, in this step part 7a,
When the seal conductor film 64 is not formed, a low-melting glass material, a thermosetting resin, or the like may be used as the seal member.

Hereinafter, a method for manufacturing a multilayer circuit board according to the present invention will be described.

A green sheet made of an insulating material to be the multilayer substrate 1, for example, a glass-ceramic material is formed. Note that this green sheet is a large green sheet including a plurality of substrate regions serving as the substrate 1. When a capacitance component or a microstrip line is formed inside the multilayer substrate 1, it is necessary to use an insulating material in consideration of dielectric characteristics.

Next, a through-hole serving as a via-hole conductor 3 is formed by punching in each substrate region on the green sheet, and an Ag-based material is screen-printed in each substrate region on the green sheet by screen printing. The conductive paste is filled, and a conductive film or the like to be the internal wiring layer 4 is formed. When forming the through hole, a portion to be the cavity 7 may be punched with a punch. Further, when forming the conductor film to be the internal wiring layer 4, the conductor to be the seal conductor film 64 in the portion to be the step portion 7 a of the cavity 7 and the conductor to be the mounting electrode pad 71 in the portion to be the bottom portion of the cavity 7. Form a film. Further, a conductor film to be the surface wiring layer 2 is formed on the green sheet located at the outermost layer
Conductive films serving as various electrode pads are formed.

The green sheets on which the respective conductor films are formed are stacked and integrated in the stacking order to form an unfired large-sized multilayer substrate including a plurality of substrate regions. Then, if necessary, depending on the shape of each multilayer circuit board,
A dividing groove is formed.

Next, the large-sized multilayer substrate in the unfired state is fired in an air atmosphere or a neutral atmosphere. The firing conditions are determined by the internal wiring material and the insulating material.

In this step, a large multilayer circuit board is obtained in which the internal wiring layer 4 and the via-hole conductor 3 are formed in each substrate region to be the multilayer substrate 1 and the surface wiring layer 2 is formed on the surface. Become. Further, a cavity 7 is formed on the surface of the multilayer substrate 1, a step 7 a is formed on the inner wall of the cavity 7, and a seal conductor film 64 is formed on the step 7 a and an electrode pad 71 is formed on the bottom of the cavity 7. .

Thereafter, if necessary, a thick-film resistance element connected to the surface wiring layer 2 and an insulating protective film having a predetermined shape are formed.

Next, the circuit component 8 is mounted on the surface wiring layer 2 formed around the cavity 7 on the surface of the multilayer substrate 1 by soldering or the like.

Next, an electronic component element such as a surface acoustic wave filter 5 and an IC chip are mounted in the cavity 7. For example, bumps 51 are formed on the mounting surface side electrode portion of the surface acoustic wave filter 5 and are bonded by ultrasonic thermocompression so that the bumps 51 abut on the electrode pads 71 of the cavity 7.

As the metal lid 6, a substrate having a surface insulating layer 61 formed on its surface and a surface circuit pattern 62 formed on its surface by a thick film technique or a thin film technique is used. If necessary, a resin coating layer 65 may be formed on the back surface of the metal lid 6 so as to expose the periphery.

Next, the opening of the cavity 7 is hermetically sealed using the metal lid 6 described above. That is, the metallic lid 6
Are placed on the stepped portion 7a of the cavity 7 with a sealing conductor film 64 provided around the stepped portion and a sealing member 73 such as solder interposed therebetween.

Next, another circuit component 60 is connected to the metal cover 6.
Mounted on the surface circuit pattern 62 by soldering or the like,
At the same time, the surface circuit pattern 62 on the metal lid 6 and the substrate 1
The upper surface wiring layer 2 is connected with a bonding wire 63 such as an Au wire or an Al wire to form a metal cover 6.
The surface circuit pattern 62 on the side and the surface wiring layer 2 on the multilayer substrate 1 are electrically connected.

As another electrical connection, the surface circuit pattern 62 of the metal cover 6 and the surface wiring layer 2 of the multilayer substrate 1 are used.
And a chip-like electronic component 7 having two terminal electrodes
0, and the surface circuit pattern 62 and the surface wiring layer 2 are electrically connected.

Finally, the large-sized substrate is separated (divided or cut) for each substrate region, and the multilayer circuit board 10 is obtained.

As the above-described electrical connection method, FIGS. 1 and 2 show a state of connection using the bonding wire 63 and the chip-shaped electronic component 70. A method may be used.

As the sealing structure, in the above-described manufacturing method, the seal conductor film 64 is formed on the stepped portion 7a and the back surface of the metal lid 6 is joined by solder. May be omitted, and a low-melting glass or a thermosetting resin may be used for the seal member 73.

According to the multilayer circuit board 10 of the present invention, the metal lid 6 is used as the lid for sealing the cavity 7.
On the surface of the metal lid 6, a surface insulating layer 61 is formed by adhesion.
Further, a surface circuit pattern 62 is formed on the surface insulating layer 61. For this reason, the predetermined circuit pattern 62 and the circuit component 60 can be mounted also on the surface of the metal cover 6, and the mounting efficiency of component mounting on the entire surface of the multilayer circuit board 10 is improved, and the surface density is increased. Multilayer circuit board 1
It becomes 0.

Since the lid 6 is made of metal, the lid 6
Even if the insulating layer 61 and the surface circuit pattern 62 are formed on the surface, the overall thickness can be reduced to 10 to 100 μm. Therefore, the multilayer circuit board 10 can be made thinner.

The surface wiring layer 2 on the multilayer substrate 1 side and the surface circuit pattern 62 on the metal lid 6 side are electrically connected by bonding wires 63 or a chip-shaped electronic component 70 extending over the multilayer substrate 1 and the lid 6. Connected. That is,
Since the electrical connection between the surface wiring layer 2 on the side of the multilayer substrate 1 and the surface circuit pattern 62 on the side of the metal lid 6 is made on the surface portion, the electrical connection between the two can be visually confirmed. The reliability is dramatically improved. Further, since the opening of the cavity 7 of the metal lid 6 can be uniformly sealed around the back surface of the metal lid 6, the hermetic sealing of the cavity 7 is improved.

FIG. 3 is a sectional view of another embodiment of the multilayer circuit board of the present invention. In this embodiment, the metal lid 6
Is hermetically sealed around the opening of the cavity 7. That is, the seal conductor film 64 is formed around the opening of the cavity 7, and the entire periphery of the back surface of the metal lid 6 and the seal conductor film 64 are joined by a seal member 73 such as solder. In this case, the cavity 7 is sealed. Thereby, the hermetic sealing can be performed stably without providing a step in the cavity 7. Further, since the structure of the cavity 7 is simplified, the strength of the substrate 1 is improved. In this case, since the metal cover 6 protrudes from the surface of the substrate 1, it is necessary to electrically connect the surface circuit pattern 62 of the metal cover 6 and the surface wiring layer 2 of the multilayer substrate 1 by wire bonding 63. is there.

If the above-mentioned seal conductor film 64 is connected to the ground potential, the entire metal cover 6 can be set to the ground potential, so that external noise can be cut off, for example.

[0049]

According to the multilayer circuit board of the present invention, a surface insulating layer is formed on a metal cover and a surface circuit pattern is formed on the surface insulating layer. The component mounting area increases, high-density mounting becomes possible, and the size of the multilayer circuit board is reduced.

Further, since the lid is a metal lid, even if a surface insulating layer and a surface circuit pattern are formed on the surface of the metal lid, the entire thickness is 10 to 100 μm, and the thickness in the thickness direction of the multilayer circuit board is sufficient. It can also contribute to miniaturization.

Further, since the opening of the cavity can be uniformly sealed at the peripheral portion of the back surface of the metal lid, the airtightness of the cavity can be improved.

Further, since the surface wiring layer of the multilayer circuit and the surface circuit pattern of the metal cover can be electrically connected on the surface of the multilayer substrate via bonding wires or chip-like electronic components, the connection state can be visually checked. And connection reliability can be improved.

[Brief description of the drawings]

FIG. 1 is an external perspective view of a multilayer circuit board according to the present invention.

FIG. 2 is a cross-sectional view of the multilayer circuit board of FIG.

FIG. 3 is a sectional view of another embodiment of the multilayer circuit board of the present invention.

FIG. 4 is a perspective view of a conventional multilayer circuit board before sealing with a cavity portion and a lid.

FIG. 5 is a sectional view of the multilayer circuit board of FIG. 4;

[Explanation of symbols]

 10, 40 Multilayer circuit board 1 Base 1a to 1f Insulating layer 2 Surface wiring layer 3 Via hole conductor 4 Internal wiring layer 5 Electronic component element 6 Metal lid 61 Surface insulating layer 62 Surface circuit pattern 63 Bonding wire 60 Circuit component 70 Chip shape Electronic components 7 cavities

Claims (6)

[Claims] 1. A method for forming a surface wiring layer on a surface,
In a multilayer circuit board comprising: a multilayer substrate having a cavity for accommodating an electronic component element or an IC chip having an opening on a surface thereof; and a metal lid for sealing the opening of the cavity, wherein the metal lid has a surface Wherein a surface circuit pattern is formed via an insulating layer. 2. The device according to claim 1, wherein the surface wiring layer and the surface circuit pattern are electrically connected.
The multilayer circuit board according to the above. 3. The multilayer circuit board according to claim 2, wherein the electrical connection between the surface wiring layer and the surface circuit pattern is made by bonding wires. 4. A stepped portion is provided around the inner wall of the cavity, and a metal cover is placed on the stepped portion, and at least one pair of the metal cover and the multi-layer substrate and the metal cover are provided. While disposing a chip-shaped electronic component having a terminal electrode and one terminal electrode on the surface wiring layer,
2. The multilayer circuit board according to claim 1, wherein the other terminal electrode is electrically connected to the surface circuit pattern. 5. The multilayer circuit board according to claim 4, wherein a seal conductor film is formed on the stepped portion, and the back surface of the metal cover is joined to the seal conductor film. 6. The multilayer circuit board according to claim 1, wherein a seal conductor film is formed around the opening of the cavity, and a back surface of the metal cover is joined to the seal conductor film.