Patent ID: 12224390

DESCRIPTION OF EMBODIMENTS

Some exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings.

First Embodiment

An electronic component mounting substrate1according to the present embodiment includes: a metal substrate11having a first surface11a; an insulation substrate21having a second surface21aon which a first metal layer22having a frame shape is provided; and a bonding material31that bonds the first surface11aand the first metal layer22. The bonding material31is located in a region that includes the first metal layer22and is surrounded by the first metal layer22in a plane perspective. In the plane perspective, the second metal layer23is located in a region surrounded by the first metal layer22of the second surface21a. A wiring layer24is located on a surface of the insulation substrate21, opposite to the second surface21a. InFIGS.1A to5, the upward direction refers to the positive direction of an imaginary z-axis. It should be noted that the distinction between upper and lower in the following description is for convenience only and is not intended to limit the upper and lower directions when the electronic component mounting substrate1or the like is actually used.

The metal substrate11includes the first surface11a(upper surface inFIGS.1A to5), a third surface (lower surface inFIGS.1A to5) opposite to the first surface11ain the thickness direction, and side surfaces. As the metal substrate11, a material having high thermal conductivity, for example, a metal material such as copper (Cu), copper-tungsten (Cu—W), or aluminum (Al) can be used. When the electronic component mounting substrate1is applied to a headlamp or the like of an automobile, aluminum may be used as the metal substrate11in view of its light weight.

The insulation substrate21includes the second surface21a(lower surface inFIGS.1A to5), a fourth surface (upper surface inFIGS.1A to5) opposite to the second surface21ain the thickness direction, and side surfaces. The insulation substrate21is composed of a single insulation layer or a plurality of insulation layers, and has a square shape in plan view, that is, when viewed from a direction perpendicular to the second surface21a. The first surface11aof the metal substrate11and the second surface21aof the insulation substrate21are located opposite to each other. The insulation substrate21functions as a support for supporting an electronic component2. The insulation substrate21includes the wiring layer24for mounting the electronic component2on the side of the fourth surface in plan view, and the first metal layer22and the second metal layer23for joining with the metal substrate11on the side of the second surface21ain plan view.

As the insulation substrate21, for example, a ceramic such as an aluminum oxide sintered body (alumina ceramic), an aluminum nitride sintered body, a silicon nitride sintered body, a mullite sintered body or a glass ceramic sintered body can be used. As the insulation substrate21, for example, a ceramic such as an aluminum oxide sintered body (alumina ceramic), an aluminum nitride sintered body, a silicon nitride sintered body, a mullite sintered body or a glass ceramic sintered body can be used. When the insulation substrate21is, for example, an aluminum nitride sintered body, a slurry is prepared by adding and mixing a suitable organic binder and a solvent to raw material powders such as aluminum nitride (AlN), erbium oxide (Er2O3), and yttrium oxide (Y2O3). A ceramic green sheet is produced by molding the slurry into a sheet by employing a conventionally known doctor blade method, calender roll method, or the like. As required, a plurality of ceramic green sheets are laminated and fired at a high temperature (about 1800° C.) to produce the insulation substrate21consisting of a single insulation layer or a plurality of insulation layers. To achieve the electronic component mounting substrate1having excellent heat dissipating properties, an aluminum nitride sintered body or a silicon nitride sintered body may be used for the insulation substrate21.

The first metal layer22is located on the second surface21aof the insulation substrate21. The second metal layer23is located on the second surface21aof the insulation substrate21. The first metal layer22and the second metal layer23are used as bonding portions of the bonding material31or the like to bond the metal substrate11and the insulation substrate21.

The wiring layer24is located on the fourth surface of the insulation substrate21. The wiring layer24is used as a connecting portion of a connecting member3such as a bonding wire, and is used for electrically connecting the electronic component2to connection pads of a module substrate.

The first metal layer22, the second metal layer23, and the wiring layer24each include a thin film layer and a plating layer. The thin film layer includes, for example, an adhesion metal layer and a barrier layer. The adhesion metal layer constituting the thin film layer is formed on the second surface21aor the fourth surface of the insulation substrate21. The adhesion metal layer is made of, for example, tantalum nitride, nickel-chromium, nickel-chromium-silicon, tungsten-silicon, molybdenum-silicon, tungsten, molybdenum, titanium, or chromium, and is deposited on the second surface21aor the fourth surface of the insulation substrate21by employing a thin film forming technique such as a vapor deposition method, an ion plating method, or a sputtering method. For example, in the case of forming the adhesion metal layer by the vacuum deposition method, the insulation substrate21is set in the deposition chamber of the vacuum deposition apparatus, and a metal piece to be the adhesion metal layer is disposed at the deposition source in the deposition chamber. Thereafter, the deposition chamber is brought into a vacuum state (pressure of 10−2Pa or less), the metal piece disposed at the deposition source is heated and deposited, and molecules of the deposited metal piece are deposited on the insulation substrate21to form a thin film metal layer to be the adhesion metal layer. After a resist pattern is formed by photolithography on the insulation substrate21on which the thin film metal layer has been formed, the excess thin film metal layer is removed by etching to form the adhesion metal layer. A barrier layer is deposited on the upper surface of the adhesion metal layer. The barrier layer has good wettability and bonding properties with the adhesion metal layer and the plating layer and serves to firmly bond the adhesion metal layer and the plating layer and to make the adhesion metal layer and the plating layer less likely to interdiffuse. The barrier layer is composed of, for example, nickel-chromium, platinum, palladium, nickel, or cobalt, and is deposited on the surface of the adhesion metal layer by a thin film forming technique such as a vapor deposition method, an ion plating method, or a sputtering method.

The thickness of the adhesion metal layer is preferably about from 0.01 to 0.5 μm. When the thickness is less than 0.01 μm, it tends to be difficult to firmly adhere the adhesion metal layer on the insulation substrate21. When the thickness exceeds 0.5 μm, the adhesion metal layer is more likely to peel off due to internal stress at the time of forming the adhesion metal layer. The thickness of the barrier layer is preferably about from 0.05 to 1 μm. When the thickness is less than 0.05 μm, defects such as pinholes are generated, and the barrier layer is less likely to function as intended. When the thickness exceeds 1 μm, the barrier layer is more likely to peel off due to internal stress at the time of forming the barrier layer.

The plating layer is deposited on an exposed surface of the thin film layer by an electroplating method or an electroless plating method. The plating layer is made of a metal such as nickel, copper, gold or silver which has excellent corrosion resistance and excellent connection performance with the connecting member3. For example, a nickel plating layer having a thickness of about from 0.5 to 5 μm and a gold plating layer having a thickness of about from 0.1 to 3 μm are sequentially deposited. Thus, the first metal layer22, the second metal layer23, and the wiring layer24can be effectively prevented from corroding, and the bonding between the wiring layer24and the connecting member3and the bonding between the first metal layer22, the second metal layer23and the metal substrate11can be strengthened.

Further, a metal layer such as copper (Cu) or gold (Au) may be arranged on the barrier layer so that the plating layer is satisfactorily formed. The metal layer is formed by the same method as the thin film layer.

Between the metal substrate11and the insulation substrate21, the first surface11aof the metal substrate11and the first metal layer22and the second metal layer23located on the second surface21aof the insulation substrate21are bonded by the bonding material31. The bonding material31is located in a region surrounded by the first metal layer22in a plane perspective. The outer edge (outer surface) of the bonding material31has a meniscus shape. The bonding material31is bonded to the entire region of the first surface11aof the metal substrate11in a plane perspective in the region surrounded by the first metal layer22. In the region surrounded by the first metal layer22, the bonding material31is not bonded to the second surface21aof the insulation substrate21, except for the first metal layer22and the second metal layer23in a plane perspective. The bonding material31may be located from the region surrounded by the first metal layer22to the outside of the region surrounded by the first metal layer22in a plane perspective. In the above case, the bonding material31may be located inward of the outer edge of the insulation substrate21in a plane perspective.

An electronic device can be manufactured by mounting the electronic component2on the fourth surface of the insulation substrate21of the electronic component mounting substrate1. The electronic component2mounted on the electronic component mounting substrate1is a light emitting element such as a laser diode (LD) or a light-emitting diode (LED), or a light receiving element such as a photo diode (PD). For example, when the electronic component2is a wire-bonding type light emitting element, the light emitting element is fixed on the insulation substrate21by a bonding member such as a low-melting point brazing material or an electrically conductive resin, and then is mounted on the electronic component mounting substrate1by electrically connecting an electrode of the light emitting element and the wiring layer24via a connecting member3such as a bonding wire. Thus, the electronic component2is electrically connected to the wiring layer24.

For example, when the electronic component2is a flip-chip type electronic component2, the electronic component2is mounted on the electronic component mounting substrate1by electrically and mechanically connecting an electrode of the electronic component2and the wiring layer24via a connecting member3such as a solder bump, a gold bump or a conductive resin (anisotropic conductive resin or the like).

A plurality of the electronic components2may be mounted on the fourth surface of the electronic component mounting substrate1and, as required, a small electronic component such as a resistive element or a capacitative element, or other components, may be mounted around the electronic component2. When a plurality of the electronic components2are mounted on the fourth surface of the electronic component mounting substrate1, the region surrounding the plurality of electronic components2in plan view may be regarded as a mounting portion11a. The electronic component2is encapsulated with an encapsulation member made of resin, glass or the like, or with a lid made of resin, glass, ceramic, metal or the like, as required. As in the example illustrated inFIG.5, a heat dissipation member4such as a heat sink may be mounted on the electronic device.

The electronic component mounting substrate1according to the present embodiment includes: a metal substrate11including a first surface11a; an insulation substrate21including a second surface21aon which a first metal layer22having a frame shape is provided; and a bonding material31that bonds the first surface11aand the first metal layer22, where the bonding material31is located in a region that includes the first metal layer22and that is surrounded by the first metal layer22in a plane perspective. According to the above configuration, since the bonding material31is located in the region surrounded by the first metal layer22, even when there is a difference in thermal expansion between the metal substrate11and the insulation substrate21, the bonding material located in the region surrounded by the first metal layer22distributes stress due to the difference in thermal expansion between the metal substrate11and the insulation substrate21, so that strain on the entire electronic component mounting substrate1is reduced. As a result, the electronic component mounting substrate1can have excellent reliability.

Even when the insulation substrate21is a thin substrate having a thickness of 0.3 mm or less, since the bonding material is located below the electronic component2when the electronic component2is mounted on the fourth surface of the insulation substrate21, deflection of the insulation substrate21can be reduced when mounting the electronic component2, the electronic component2can be mounted satisfactorily, and the electronic component mounting substrate1can have excellent reliability.

As in the example illustrated inFIG.2, the insulation substrate21includes a second metal layer23located inside the first metal layer22in a front view of the second surface21a. According to the above configuration, even when a difference in thermal expansion occurs between the metal substrate11and the insulation substrate21while operating the electronic component2, the compressive stress between the first metal layer22and the second metal layer23is distributed by the bonding material31located between the first metal layer22and the second metal layer23to reduce the stress applied to the insulation substrate21, and reduce the strain of the insulation substrate21. As a result, the electronic component mounting substrate1can have excellent reliability.

In a vertical cross-sectional view, the bonding material31has a height in the region surrounded by the first metal layer22equal to a height in a region bonding the first metal layer22or the second metal layer23. With the above configuration, the compressive stress between the first metal layer22and the second metal layer23is well distributed by the bonding material31located between the first metal layer22and the second metal layer23to reduce the stress on the insulation substrate21and to further reduce the strain of the insulation substrate21. As a result, the electronic component mounting substrate1can have excellent reliability.

As in the example illustrated inFIGS.3A and3B, the bonding material31has a height in the region surrounded by the first metal layer22that is higher than a height in a region bonding the first metal layer22or the second metal layer23in a vertical cross-sectional view. That is, in the region surrounded by the first metal layer22, the interval between the second surface21aof the insulation substrate21and the bonding material31is smaller than the thickness of the first metal layer22or the thickness of the second metal layer23. With the above configuration, the compressive stress between the first metal layer22and the second metal layer23is well distributed by the bonding material31located between the first metal layer22and the second metal layer23to reduce the stress on the insulation substrate21and further reduce the strain of the insulation substrate21. As a result, the electronic component mounting substrate1can have excellent reliability.

The second metal layer23is connected to the first metal layer22in a front view, as in the example illustrated inFIG.2. With the above configuration, the compressive stress between the first metal layer22and the second metal layer23in a direction orthogonal to the direction connected to the second metal layer23is well distributed by the bonding material31located between the first metal layer22and the second metal layer23to reduce the stress on the insulation substrate21and to further reduce the strain of the insulation substrate21. As a result, the electronic component mounting substrate1can have excellent reliability.

In the above case, the second metal layer23is formed in a strip shape in the region surrounded by the first metal layer22and is connected to the first metal layer22, as in the example illustrated inFIG.2.

The second metal layer23is separated from the first metal layer22in a front view, as in the example illustrated inFIGS.6A and6B. With the above configuration, the compressive stress between the first metal layer22and the second metal layer23is well distributed by the bonding material31located between the first metal layer22and the second metal layer23to reduce the stress on the insulation substrate21and to further reduce the strain of the insulation substrate21. As a result, the electronic component mounting substrate1can have excellent reliability.

In the above case, the second metal layer23is formed as one or more metal layers in the region surrounded by the first metal layer22, as in the example illustrated inFIGS.6A and6B. The second metal layer23is formed as a circular shape, or a polygonal shape having a quadrilateral shape in a plane perspective. When a plurality of metal layers are used for the second metal layer23, the compressive stress between the respective second metal layers23is distributed by the bonding material31located between the respective second metal layers23to reduce the stress on the insulation substrate21and to further reduce the strain of the insulation substrate21. As a result, the electronic component mounting substrate1can have excellent reliability.

When a light emitting element is used as the electronic component2, the electronic component mounting substrate1can be an electronic component mounting substrate1for mounting a compact light emitting element of high brightness for a long period of time.

According to the electronic device of the present embodiment, since the electronic component mounting substrate1having the above configuration and the electronic component2mounted on the electronic component mounting substrate1are provided, the electronic device can be used satisfactorily over a long period of time.

The wiring layer24of the electronic device is electrically connected to a wiring conductor of an external device.

Further, as in the example illustrated inFIG.5, the heat dissipation member4made of Al or the like is bonded to the lower surface of the electronic device. With the above configuration, the heat of the electronic device can be dissipated by the heat dissipation member4more satisfactorily, and the electronic device can be used satisfactorily over a long period of time.

In the heat dissipation member4, for example, a through hole is formed outside the bonding portion between the electronic device and the heat dissipation member4in a plane perspective, the electronic device is held in an external device by screwing a screw inside the through hole, and the wiring layer of the electronic device and the wiring conductor of the external device are electrically connected by a connecting material.

Second Embodiment

Next, the electronic component mounting substrate1according to a second embodiment will be described with reference toFIGS.7to8B.

The electronic component mounting substrate1according to the second embodiment differs from the electronic component mounting substrate1according to the above-described embodiment in that the first metal layer22and the second metal layer23located on the second surface21aof the insulation substrate21have different thicknesses in a vertical cross-sectional view.

According to the electronic component mounting substrate1of the second embodiment, as in the case of the electronic component mounting substrate1of the above-described embodiment, since the bonding material31is located in the region surrounded by the first metal layer22, even when there is a difference in thermal expansion between the metal substrate11and the insulation substrate21, the bonding material located in the region surrounded by the first metal layer22distributes stress due to the difference in thermal expansion between the metal substrate11and the insulation substrate21, so that the strain of the entire electronic component mounting substrate1is reduced and the electronic component mounting substrate1can have excellent reliability.

In the electronic component mounting substrate1according to the second embodiment, the second metal layer23may be, similar to that of the electronic component mounting substrate1according to the first embodiment, connected to the first metal layer22in a front view, or may be separated from the first metal layer22in a front view.

The electronic component mounting substrate1according to the second embodiment can otherwise be manufactured by the same manufacturing method as the electronic component mounting substrate1according to the above-described embodiment.

The present disclosure is not limited to the examples of the above-described embodiments, and various modifications can be made. For example, the insulation substrate21may have a rectangular shape having notches or chamfers on the side surfaces or corners in a plan view.

REFERENCE SIGNS LIST

1Electronic component mounting substrate11Metal substrate11aFirst surface21Insulation substrate21aSecond surface22First metal layer23Second metal layer24Wiring layer31Bonding material2Electronic component3Connecting member4Heat dissipation member