Patent Application
20160118346
The present invention relates to a device embedded substrate in which an electrical or electronic device is embedded, and a manufacturing method thereof.
Conventionally, research and development has been performed for reducing a size, a thickness, and a weight, and increasing functions of various electrical and electronic equipment. Particularly, in consumer products such as mobile phones, notebook computers, and digital cameras, there is a strong demand for the reduction in size, thickness, and weight while increasing functions. Also, in various types of electrical and electronic equipment, a frequency and a speed of a transmission signal have been increased, and it is also required to prevent a corresponding increase in signal noise.
In order to meet such demands, a device embedded substrate having a structure in which various electrical or electronic devices, which have been conventionally mounted on a substrate surface, are embedded in an insulating base material that is an insulating layer of a substrate, and a device embedded multilayer circuit board obtained by laminating the device embedded substrates have been conventionally researched, developed, and manufactured as a circuit board incorporated in electrical and electronic equipment. For example, Patent Document 1 discloses a device embedded substrate and a manufacturing method thereof.
In the method for manufacturing a device embedded substrate disclosed in Patent Document 1, a conductive thin film layer made of a copper foil is formed on a support body, and an adhesive is applied onto the conductive thin film layer. Subsequently, an electrical or electronic device to be embedded (an embedded device) is mounted via the adhesive, and an insulating layer (an insulating base material) is then formed so as to cover the embedded device. In the device embedded substrate formed through manufacturing steps as described above, a thickness of the substrate itself is smaller than that of a conventional device embedded substrate, and more electrical or electronic devices can be embedded than those mounted on a substrate surface. Thus, the device embedded substrate can be used for electrical and electronic equipment for various purposes.
Also, in a case in which an IC device such as a metal-oxide-semiconductor field-effect transistor (MOSFET) or an integrated circuit (IC) is used as the embedded device, it is necessary to form a conductive via that extends to the embedded device from an outer portion of an insulating layer in which the embedded device is embedded. The conductive via extends within the insulating layer so as to penetrate metal layers formed on both surfaces of the insulating layer and an adhesive made of an insulating material for fixing the embedded device to the metal layer, and electrically connect the outer portion of the insulating layer to a connection terminal of the embedded device.
Patent Document 1: Japanese Patent No. 4874305
In recent years, since there exist a variety of types of electrical and electronic equipment, a variety of types of device embedded substrates have been developed corresponding to the types of the electrical and electronic equipment. For example, a device embedded substrate in which a plurality of IC devices are embedded in an insulating layer, and a device embedded substrate in which one IC device is embedded in an insulating layer have been developed. Here, in a case in which only one IC device is embedded, it is necessary to decrease the insulating layer such that the IC device occupies a large portion of the device embedded substrate in order to reduce a size of the device embedded substrate. In order to surely fix the IC device to a metal layer, a formation area of an adhesive layer becomes equal to or larger than an area of a mounting surface of the IC device.
However, if the formation area of the adhesive layer is increased, a pressure applied to the adhesive layer in a vacuum heating step after forming the metal layer is increased, while a stress is applied to an insulating material forming the insulating layer in a direction different from that of the pressure due to a cure shrinkage. Thus, the metal layer is detached from a support body. Due to the detachment of the metal layer as described above, wrinkles are induced in the metal layer, and reliability of the device embedded substrate itself is deteriorated.
Here, it is considered that generation of the above wrinkles can be suppressed by decreasing the formation area of the adhesive layer. However, the adhesive layer and the insulating layer having different properties are located in a region where the conductive via is formed, and there occurs a problem that materials forming the respective layers remain due to a difference in etching rate when the conductive via is formed, thereby causing a connection failure of the conductive via.
The present invention has been made in view of the problems as described above, and an object of the present invention is to provide a device embedded substrate in which a metal layer located on an insulating layer is not detached, and a connection failure of a conductive via is not caused, and a manufacturing method thereof.
In order to achieve the above object, a device embedded substrate of the present invention includes: an insulating layer that is made of an insulating material; a first metal layer and a second metal layer that are formed such that the insulating layer is sandwiched therebetween; an electrical or electronic device that is embedded in the insulating layer, and in which a connection terminal non-formation surface where a connection terminal is not formed is located on a side close to the first metal layer; an adhesive layer that is embedded in the insulating layer, and is located on the connection terminal non-formation surface of the device; and a conductive via that extends within the insulating layer, and electrically connects the second metal layer and the connection terminal of the device, wherein an area of the adhesive layer on a surface side in contact with the device is smaller than an area of the connection terminal non-formation surface of the device.
In the above device embedded substrate, the area of the adhesive layer on the surface side in contact with the device is preferably within a range of 13% to 40% of the area of the connection terminal non-formation surface of the device.
In any of the above device embedded substrate, the area of the adhesive layer on the surface side in contact with the device is preferably within a range of 7% to 25% of an area of the device embedded substrate on a surface side where the first metal layer is formed.
In any of the above device embedded substrate, a plane shape of the adhesive layer is preferably a circular shape.
Also, in order to achieve the above object, a method for manufacturing a device embedded substrate of the present invention includes: a preparation step of preparing a support plate where a first metal layer is formed on a surface; a mounting step of mounting an electrical or electronic device on a surface of the first metal layer via an adhesive layer such that a connection terminal non-formation surface where a connection terminal is not formed is located on a side close to the first metal layer; an insulating layer formation step of forming an insulating layer in which the device is embedded by laminating an insulating material so as to cover the first metal layer and the device; a metal layer formation step of forming a second metal layer on the insulating layer; and a conductive via formation step of forming a conductive via that extends within the insulating layer so as to electrically connect the second metal layer and the connection terminal of the device, wherein in the mounting step, an area of the adhesive layer on a surface side in contact with the device is made smaller than an area of the connection terminal non-formation surface of the device.
In the mounting step in the above method for manufacturing a device embedded substrate, the area of the adhesive layer on the surface side in contact with the device is preferably set to 13% to 40% of the area of the connection terminal non-formation surface of the device.
In the mounting step in any of the above method for manufacturing a device embedded substrate, the area of the adhesive layer on the surface side in contact with the device is preferably set to 7% to 25% of an area of the device embedded substrate on a surface side where the first metal layer is formed.
In the mounting step in any of the above method for manufacturing a device embedded substrate, the adhesive layer is preferably formed such that a plane shape of the adhesive layer is a circular shape.
In the device embedded substrate and the manufacturing method according to the present invention, since the connection terminal non-formation surface of the device is arranged close to the first metal layer, and the formation area of the adhesive layer is made smaller than the area of the connection terminal non-formation surface of the device, it is possible to prevent detachment of the first metal layer from the insulating layer, and a connection failure of the conductive via.
In the device embedded substrate and the manufacturing method according to the present invention, since the circular shape is employed as the plane shape of the adhesive layer, bubbles, air gaps or the like are not generated in the adhesive layer when the adhesive layer is formed, and the device can be firmly fixed.
In the following, an exemplary embodiment of the present invention is described in detail based on an embodiment by reference to the drawings. Note that the present invention is not limited to contents described below, and can be optionally modified and carried out without departing from the scope. Also, in the drawings used for describing the embodiment, all of which schematically show a device embedded substrate and its constituent members according to the present invention, the device embedded substrate and the constituent members are partially emphasized, enlarged, reduced, or omitted for the purpose of developing an understanding. Thus, the drawings do not accurately show scales, shapes or the like of the device embedded substrate and the constituent members in some cases. Furthermore, various numerical values used in the embodiment are merely examples, and can be variously changed if necessary.
First, a structure of a device embedded substrate according to the present embodiment of the present invention is described in detail by reference to
As shown in
The IC device 2 includes a connection terminal 2a that electrically connects an inner portion and an outer portion of the IC device 2 so as to guide a power, a current, a voltage, or an electrical signal supplied from the outer portion to the inner portion of the IC device 2 on a first surface 2b (a connection terminal formation surface)-side. Also, in the IC device 2, the connection terminal 2a is not formed on a second surface 2c located on an opposite side to the first surface 2b. That is, the second surface 2c is a connection terminal non-formation surface. Moreover, as shown in
Although the IC device 2 is employed as a device embedded in the device embedded substrate 1 in the present embodiment, the device embedded in the device embedded substrate 1 is not limited thereto. For example, another electrical or electronic device such as a resistor and a capacitor may be embedded in the insulating layer 3.
In the present embodiment, an insulating resin material such as a prepreg is used for the insulating layer 3. Here, a material of the insulating layer 3 preferably has a thermal expansion coefficient close to that of the IC device 2. This is to mitigate a stress on the IC device 2 when the insulating material is cured. Note that the material of the insulating layer 3 is not limited to the insulating resin material, and as long as the IC device 2 can be embedded and there is no problem in electrical properties and reliability etc., another general insulating material may be used.
The first metal layer 4 is formed on a surface of the insulating layer 3 that is close to the second surface 2c of the IC device 2. In the present embodiment, the first metal layer 4 is made of copper. Also, a desired interconnection pattern is formed in the first metal layer 4 by patterning. Note that a material of the first metal layer 4 is not limited to the copper, and as long as there is no problem in electrical properties and reliability etc., another general metal material may be used.
The second metal layer 5 is formed on a surface of the insulating layer 3 that is located on an opposite side to the surface close to the second surface 2c of the IC device 2. In the present embodiment, the second metal layer 5 is made of copper similarly to the first metal layer 4. Also, a desired interconnection pattern is formed in the second metal layer 5 by patterning. Note that a material of the second metal layer 5 is not limited to the copper, and as long as there is no problem in electrical properties and reliability etc., another general metal material may be used.
In the present embodiment, an adhesive made of a general insulating material is used for the adhesive layer 6. As shown in
Also, the adhesive layer 6 is formed so as to be fitted within the second surface 2c of the IC device 2. That is, an area of the adhesive layer 6 on a surface side in contact with the IC device 2 (an application area of the adhesive) is smaller than an area of the second surface 2c of the IC device 2. To be more specific, the area of the adhesive layer 6 on the surface side in contact with the IC device 2 is preferably within a range of 13% to 40% of the area of the second surface 2c of the IC device 2. In the present embodiment, an application dimension of the adhesive is about φ1.5 mm, and the area (about 1.77 mm2) of the adhesive layer 6 on the surface side in contact with the IC device 2 is about 15% of the area (about 11.56 mm2) of the second surface 2c of the IC device 2. Although the adhesive layer 6 having a circular plane shape is formed by setting the application dimension of the adhesive to about φ1.5 mm in the present embodiment, the plane shape of the adhesive layer is not limited to the circular shape, and a polygonal shape or an elliptical shape may be employed.
Furthermore, when compared with the device embedded substrate 1 itself, the area of the adhesive layer 6 on the surface side in contact with the IC device 2 is preferably within a range of 7% to 25% of an area of the device embedded substrate 1 on a surface side where the first metal layer 4 is formed. In the present embodiment, the area of the adhesive layer 6 on the surface side in contact with the IC device 2 is about 10% of the area (about 16 mm2) of the device embedded substrate 1 on the surface side where the first metal layer 4 is formed.
By forming the adhesive layer 6 as described above, a large portion of the second surface 2c of the IC device 2 is covered with the insulating layer 3. The insulating layer 3 is also located around the adhesive layer 6. That is, the adhesive layer 6 is also in an embedded state in the insulating layer 3.
The conductive via 7 is provided to extend within the insulating layer 3 in order to electrically connect each of the connection terminals 2a of the IC device 2 and the second metal layer 5. A conductor such as copper is used as a material of the conductive via 7. Note that the material of the conductive via 7 is not limited to the copper, and as long as there is no problem in electrical properties and reliability etc., another general metal material may be used.
Next, a method for manufacturing a device embedded substrate according to the embodiment of the present invention is described in detail by reference to
First, as shown in
Subsequently, as shown in
Here, in the present embodiment, the application dimension of the adhesive forming the adhesive layer 6 is set to about φ1.5 mm, and the area of the adhesive layer 6 on the surface side in contact with the IC device 2 is set to about 15% of the area of the second surface 2c of the IC device 2, and about 10% of the area of the device embedded substrate 1 on the surface side where the first metal layer 4 is formed.
Subsequently, as shown in
Subsequently, as shown in
Here, in the present embodiment, the application dimension of the adhesive forming the adhesive layer 6 is set to about φ1.5 mm, and the area of the adhesive layer 6 on the surface side in contact with the IC device 2 is set to about 15% of the area of the second surface 2c of the IC device 2, and about 10% of the area of the device embedded substrate 1 on the surface side where the first metal layer 4 is formed. Thus, the insulating layer 3 covers a large portion of the second surface 2c of the IC device 2. Accordingly, a pressure applied to the adhesive layer 6 toward the first metal layer 4 when the laid-up insulating resin material such as a prepreg is heated in a vacuum becomes relatively small. Also, in the vacuum heating process, a stress caused by a cure shrinkage is applied to the insulating resin material located around the adhesive layer 6 toward the surface side where the second metal layer 5 is formed, so that the pressure and the stress cancel each other out. Accordingly, detachment of the first metal layer 4 from the support plate 11 is suppressed.
Note that a ratio of the area of the adhesive layer 6 on the surface side in contact with the IC device 2 to the area of the second surface 2c of the IC device 2 or the area of the device embedded substrate 1 on the surface side where the first metal layer 4 is formed is not limited to the above numerical value. Particularly, by setting the area of the adhesive layer 6 on the surface side in contact with the IC device 2 to be within the range of 13% to 40% of the area of the second surface 2c of the IC device 2, and to be within the range of 7% to 25% of the area of the device embedded substrate 1 on the surface side where the first metal layer 4 is formed, the above effect can be sufficiently produced.
In the present embodiment, the circular shape is employed as the plane shape of the adhesive layer 6 by setting the application dimension of the adhesive forming the adhesive layer 6 to about φ1.5 mm. Accordingly, the adhesive is properly melted, and bubbles (voids), air gaps or the like are not formed in the adhesive layer 6. Therefore, the IC device 2 can be firmly fixed onto the first metal layer 4.
Subsequently, as shown in
After the via 12 is formed, a desmear process is performed to remove a resin remaining in the via formation. A soft etching process is also performed on the connection terminal 2a to remove oxides and organic matters on an exposed surface of the connection terminal 2a exposed by the via formation. Accordingly, a fresh metal surface is exposed, and adhesion with metal deposited in a subsequent plating process is improved, resulting in an improvement in electrical connection reliability.
Here, around the connection terminal 2a where the via 12 is formed, only the insulating layer 3 made of the insulating resin material exists, and insulating resin materials having different properties from each other do not exist. Therefore, remaining of the insulating resin materials due to a difference in etching rate, which occurs when a via is formed in the insulating resin materials having different properties from each other, does not occur in an etching process performed when the via 12 is formed in the present embodiment. Accordingly, the device embedded substrate 1 that is finally obtained has excellent electrical properties and reliability with no connection failure of the conductive via 7 being caused.
Subsequently, as shown in
By cutting the insulating layer 3 along a dashed line VII-VII in
As described above, the device embedded substrate 1 and the manufacturing method according to the present embodiment are featured in that the second surface 2c that is the connection terminal non-formation surface of the IC device 2 is arranged close to the first metal layer 4, and the application area of the adhesive that becomes the adhesive layer 6 is made smaller than the area of the second surface 2c of the IC device 2. Because of the configuration, in the device embedded substrate 1 according to the present embodiment, the first metal layer 4 located on the surface of the insulating layer 3 is not detached, and the connection failure of the conductive via 7 is not caused.
1 Device embedded substrate
2 IC device
2
a Connection terminal
2
b First surface
2
c Second surface
3 Insulating layer
4 First metal layer
5 Second metal layer
6Adhesive layer
7 Conductive via
11 Support plate
12 Via
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/063959 | 5/20/2013 | WO | 00 |
