JP2020181899A - Circuit board and electronic apparatus including the same - Google Patents

Abstract

To provide a circuit board excellent in heat radiation property, and to provide an electronic apparatus including a device on the circuit board.SOLUTION: A circuit board of the present disclosure comprises: a substrate having a first surface; a first metal layer located on the first surface; a device mounting part connected with and located on the first metal layer; a glass layer located on the first metal layer; and a second metal layer located on the glass layer. An electronic apparatus of the present disclosure comprises: the above-described circuit board and a device located on the circuit board.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a circuit board and an electronic device including the circuit board.

An LED (light emitting diode) is used as a light emitting element with low power consumption. In order to mount such a light emitting element, an insulating substrate, a metal layer located on the substrate, an element mounting portion located connected to the metal layer, and a wiring layer for forming a circuit are used. (See, for example, Patent Document 1).

The light emitting element generates heat during operation. In order to maximize the performance (luminance) of the light emitting element, the circuit board needs to have excellent heat dissipation characteristics.

Japanese Unexamined Patent Publication No. 2005-347355

In order to improve the heat dissipation characteristics of the circuit board, the area of the metal layer located directly under the light emitting element may be increased, but on the insulating substrate, not only the metal layer but also the wiring layer for forming the circuit Since a placement area is also required, the area of the metal layer cannot simply be increased.

Further, if a through hole is provided in the insulating substrate, a via conductor is formed, and the surface opposite to the side on which the light emitting element is mounted is used, the heat dissipation characteristics can be improved, but the hole for the via is formed. , Via filling, and printing of the metal layer on the opposite surface requires a manufacturing cost including workability.

The present disclosure has been devised in view of such circumstances, and an object of the present invention is to provide a circuit board having excellent heat dissipation characteristics and an electronic device provided with the circuit board.

The circuit board of the present disclosure includes a substrate having a first surface, a first metal layer located on the first surface, an element mounting portion located connected to the first metal layer, and the first metal. A glass layer located on the layer and a second metal layer located on the glass layer are provided.

Further, the electronic device of the present disclosure includes the circuit board and an element located on the circuit board.

The circuit board of the present disclosure has excellent heat dissipation characteristics.

Further, the electronic device of the present disclosure can fully exhibit the performance of the element.

It is a top view which shows an example of the electronic device of this disclosure schematically. It is sectional drawing in line ii-ii of FIG. It is sectional drawing which shows the other example of the electronic device of this disclosure. It is sectional drawing which shows the other example of the electronic device of this disclosure. It is sectional drawing which shows the other example of the electronic device of this disclosure. It is sectional drawing which shows the other example of the electronic device of this disclosure.

Hereinafter, the circuit board and the electronic device of the present disclosure will be described with reference to the respective drawings. In the following description, a light emitting element will be described as an element and a light emitting device will be described as an example of the device. FIG. 1 is a plan view schematically showing an example of a light emitting device which is an electronic device of the present disclosure. FIG. 2 is a cross-sectional view taken along the line ii-ii of FIG. 3 to 6 are cross-sectional views showing another example of the configuration of the light emitting device, and the cut portion is the same as the line ii-ii shown in FIG.

In addition, in FIGS. 3 to 6, the constituent members having a portion different from FIG. 2 are shown with alphabets. Further, in FIGS. 3 to 6, the reference numerals attached to the circuit boards are also changed.

The light emitting device 20 of the present disclosure includes a circuit board 10 and a light emitting element 7 located on the circuit board. In addition, in the plan view of FIG. 1, in order to clearly show the members constituting the circuit board 10 of the present disclosure, the members other than the members constituting the circuit board 10 of the present disclosure (for example, a power supply path, a resistor, etc.) are omitted. doing.

The circuit board 10 of the present disclosure includes a substrate 1 having a first surface 1a, a first metal layer 2 located on the first surface 1a, an element mounting portion 3 located connected on the first metal layer 2, and the like. A glass layer 4 located on the first metal layer 2 and a second metal layer 5 located on the glass layer 4 are provided. Here, the light emitting element 7 is mounted on the element mounting portion 3 and is electrically connected to the second metal layer 5 by the bonding wire 6. In other words, the second metal layer 5 is a wiring layer for forming a circuit. The first metal layer 2 is a portion where heat is transferred during operation of the light emitting element 7 via the element mounting portion 3, and heat is released, so that it can be said to be a heat dissipation layer. The element mounting portion 3 may be a portion on which the element is mounted and may be made of a material different from that of the first metal layer 2, but is the same material as the first metal layer 2 and is the first material. It may be a convex portion protruding from the metal layer 2.

The circuit board 10 satisfying the above configuration covers the first metal layer 2 on the first surface 1a of the substrate 1, where at least the arrangement regions of the first metal layer 2 and the second metal layer 5 have been required so far. Since the arrangement region of the second metal layer 5 can be provided on the glass layer 4 and the arrangement region of the first metal layer 2 can be provided on the first surface 1a, the arrangement region of the first metal layer 2 is widened. be able to. Therefore, the circuit board 10 of the present disclosure has excellent heat dissipation characteristics. Specifically, the area occupancy rate of the first surface 1a of the substrate 1 with respect to the area may be 50 area% or more, 70 area% or more, or 90 area% or more.

Further, also in the second metal layer 5, since the arrangement region can be set on the glass layer 4, the degree of freedom in circuit design is improved. If there is a region on the glass layer 4 that does not require the arrangement of the second metal layer 5, the third metal layer is arranged on the glass layer 4 and connected to the first metal layer 2 via the via conductor. If this is the case, the heat dissipation characteristics will be further enhanced.

In the circuit board 10 of the present disclosure, if the first metal layer 2 is widely arranged on the first surface 1a of the substrate 1, the first metal layer 2 and the second metal can be seen in a plan view toward the first surface 1a. The layer 5 and the layer 5 exist in an overlapping manner. In the above plane perspective, when all of the second metal layer 5 overlaps with the first metal layer 2, at least the arrangement regions of the first metal layer 2 and the second metal layer 5 are required on the first surface 1a. It is an effective arrangement and has excellent heat dissipation characteristics compared to when it was.

Further, the circuit board 10 of the present disclosure has only a configuration on the first surface 1a of the substrate 1 without drilling holes for vias, filling vias, printing a metal layer on the surface opposite to the first surface 1a, and the like. Since it has excellent heat dissipation characteristics, it has good workability and low manufacturing cost.

Further, the first metal layer 2 may have an R-shaped end portion in a cross section intersecting the first surface 1a. Here, the cross section intersecting the first surface 1a is a cross section as shown in FIGS. 2 to 6. In FIG. 3, in order to clarify the difference in shape from FIG. 2, the first metal layer 2a and the circuit board 11 are described. The R-shape referred to here is a convex R-shape. When the end shape is R-shaped as in the first metal layer 2a shown in FIG. 3, the circuit board 11 has high reliability because it has excellent heat dissipation characteristics and is less likely to crack due to the difference in thermal expansion.

Further, the glass layer 4 may contain a metal. When the glass layer 4 contains a metal, the thermal conductivity is improved, so that the heat dissipation characteristics are improved. The metal contained in the glass layer 4 may be one contained from the stage of the glass paste forming the glass layer 4 or diffused from the first metal layer 2 at the time of firing. Good. When the metal is diffused from the first metal layer 2, it is present in the portion of the glass layer 4 close to the first metal layer 2. As described above, when the metal is contained in the portion close to the first metal layer 2, the glass layer 4 and the first metal layer 2 are less likely to be peeled off in addition to improving the heat dissipation characteristics.

Further, the element mounting portion 3 may have a diameter increasing toward the substrate 1. In FIG. 4, in order to clarify the difference in shape from FIG. 2, the element mounting portion 3a and the circuit board 12 are described. As shown in FIG. 3, the fact that the diameter increases toward the substrate 1 means that the diameter gradually increases in all the thicknesses from the portion where the light emitting element 7 is mounted to the portion connected to the first metal layer 2. Not exclusively. For example, the diameter may be widened from the position of half the thickness to the portion connected to the first metal layer 2. When the diameter is widened toward the substrate 1 as in the element mounting portion 3a, the heat generated by the light emitting element 7 is easily transferred to the first metal layer 2, and the heat transfer rate is improved. , Has even higher heat dissipation characteristics.

Next, it will be described with reference to FIG. The element mounting portion 3b shown in FIG. 5 includes an element mounting surface A and a peripheral surface B extending over the element mounting surface A or the first metal layer 2. The peripheral surface B includes a portion connected to the element mounting surface A, and has a first portion B1 whose diameter decreases toward the element mounting surface A. Then, at this time, the glass layer 4 may be in contact with the first portion B1. In the circuit board 13 satisfying such a configuration, the adhesion is improved by increasing the contact area between the glass layer 4 and the element mounting portion 3, and the glass layer 4 is less likely to be peeled off. Further, since the diameter of the heat input side generated by the operation of the light emitting element 7 is small and increases toward the first metal layer side, the heat transfer rate is improved and the heat dissipation characteristics are further improved.

Next, it will be described with reference to a figure. The element mounting portion 3c shown in FIG. 6 includes an element mounting surface A and a peripheral surface B extending over the element mounting surface A or the first metal layer 2. The peripheral surface B includes a portion connected to the first metal layer 2 and has a second portion B2 whose diameter becomes smaller toward the first metal layer 2. Then, at this time, the glass layer 4 may be in contact with the second portion B2. The circuit board 14 satisfying such a configuration is excellent in reliability because the glass layer 4 is less likely to be peeled off.

Up to this point, the light emitting element 7 has been described as an example of the element, but the present invention is not limited to this, and for example, an insulated gate bipolar transistor (IGBT) element, an intelligent power module (IPM) element, and a metal oxide film type electric field effect. Transistor (MOSFET) element, freewheeling diode (FWD) element, giant transistor (GTR) element, Schottky barrier diode (SBD), high electron mobile transistor (HEMT) element, complementary metal oxide semiconductor (CMOS) ), A sublimation type thermal printer head, a heat generating element for a thermal inkjet printer head, a Pelche element, or the like can be used.

The light emitting device 20 of the present disclosure includes the circuit boards 10 to 14 and the light emitting elements 7 located on the circuit boards 10 to 14, and the circuit boards 10 to 14 have excellent heat dissipation characteristics. , The performance of the light emitting element 7 can be fully exhibited.

Each component will be described below.

The substrate 1 may be an insulator, and may be made of, for example, ceramics.

Here, examples of the ceramics include aluminum oxide ceramics, zirconium oxide ceramics, composite ceramics of aluminum oxide and zirconium oxide, silicon nitride ceramics, aluminum nitride ceramics, silicon carbide ceramics and mulite ceramics. ..

When the substrate 1 is made of aluminum oxide ceramics, it has excellent workability while having the mechanical strength required for the substrate 1. Further, when the substrate 1 is made of aluminum nitride ceramics, it has excellent heat dissipation.

Here, for example, the aluminum oxide ceramics contain 70% by mass or more of aluminum oxide in 100% by mass of all the components constituting the ceramics. The material of the substrate 1 in the circuit board 10 of the present disclosure can be confirmed by the following method. First, the substrate 1 is measured using an X-ray diffractometer (XRD), and identification is performed using a JCPDS card from the obtained values of 2θ (2θ is a diffraction angle). Next, a quantitative analysis of the contained components is performed using an ICP (Inductively Coupled Plasma) emission spectroscopic analyzer (ICP) or a fluorescent X-ray analyzer (XRF). Then, for example, if the presence of aluminum oxide is confirmed by the above identification and the content converted from the Al content measured by XRF into aluminum oxide (Al ₂ O ₃ ) is 70% by mass or more, the aluminum oxide ceramics Is. It should be noted that other ceramics can be confirmed by the same method.

Next, the first metal layer 2 is mainly composed of metal. When the metal is copper or silver, the electric resistivity is low and the thermal conductivity is high, so that the light emitting element 7 having a large calorific value can be mounted. Further, when the metal is tungsten, firing can be performed at the same time as the substrate 1 made of ceramics. Further, when the metal is molybdenum-manganese, the bonding strength with the substrate 1 made of ceramics is high.

Next, the element mounting portion 3 is mainly composed of metal. As described above, the element mounting portion 3 may be made of a material different from that of the first metal layer 2, or may be made of the same material as the first metal layer 2.

Next, the second metal layer 5 is mainly composed of a metal, and examples of the metal include copper and silver. In the first metal layer 2, the element mounting portion 3, and the second metal layer 5, the fact that the metal is the main component means that the first metal layer 2, the element mounting portion 3, and the second metal layer 5 are all formed. It means that metal accounts for 50% by mass or more out of 100% by mass of the component. Each content can be confirmed by measurement using ICP or XRF.

Then, the glass layer 4, as a main _{component, R 2 O-B 2 O} 3 -SiO 2 system (R: alkali metal _{element), SiO 2 -Bi 2 O 3} -B 2 O 3 _system, R 2 O- Any of the SiO _2- B ₂ O _3- Bi ₂ O ₃ systems can be mentioned. Examples of the metal contained in the glass layer 4 include copper and silver. It is preferable that the metal is the same as the main component of the first metal layer 2.

Further, the glass layer 4 may be white. As described above, in order to make the glass layer 4 exhibit white color, a compound containing titanium and oxygen may be contained. When the glass layer 4 exhibits white color, it has a high reflectance in the visible light region. The size of the compound is, for example, 0.2 μm or more and 2.0 μm or less in diameter.

The main component of the glass layer 4 can be confirmed by measuring using ICP or XRF. Further, the presence of the metal contained in the glass layer 4 may be confirmed by using an electron probe microanalyzer (EPMA). With EPMA, it is possible to confirm whether or not the glass layer 4 is located near the first metal layer 2 by checking the entire glass layer 4.

Further, the compound contained in the glass layer 4 may be confirmed by measuring the glass layer 4 using XRD and collating the obtained result with a JCPDS card.

Alternatively, the compounds contained in the glass layer 4 can be confirmed by using an energy dispersive X-ray analyzer (EDS) attached to a scanning electron microscope (SEM). First, the circuit boards 10 to 14 are cut and polished with a cross section polisher (CP). Next, the polished cross section is used as an observation surface and observed at a magnification of 1000 times or more and 10000 times or less using SEM. Next, the EDS attached to the SEM irradiates a portion visually recognized as a particle with X-rays. If the presence of Ti and O is confirmed at this location, it can be considered that a compound containing titanium and oxygen is present.

Hereinafter, an example of the method for manufacturing the circuit board of the present disclosure will be described.

First, as a substrate, ceramics having a first surface such as aluminum nitride ceramics and aluminum oxide ceramics are prepared by a known molding method and firing method. In the production of aluminum oxide ceramics, barium oxide (BaO), zirconium oxide (ZrO ₂ ) and the like may be contained in order to improve the reflectance of the substrate. The thickness of the substrate is, for example, 0.15 mm or more and 1.5 mm or less.

Next, the first metal layer can be formed by screen-printing on the first surface 1a of the substrate 1 and then firing using a metal paste containing copper as a main component. The thickness of the first metal layer is, for example, 10 μm or more and 18 μm or less. According to this method, the shape of the first metal layer is the shape shown in FIG. 3, and the metal paste is repeatedly printed and dried to form a thick portion and fired. Alternatively, the element mounting portion may be formed by repeating printing, drying, and firing of the metal paste. When the element mounting portion is formed in addition to the first metal layer, the total thickness is, for example, 10 μm or more and 200 μm or less.

Next, prepare the glass paste. First, R ₂ O-B ₂ O _3- SiO ₂ system (R: alkali metal element), SiO _2- Bi ₂ O _3- B ₂ O ₃ system, R ₂ O-SiO _2- B ₂ O _3- Bi ₂ one of O ₃ system to prepare a glass powder mainly composed. The average particle size of the glass powder is, for example, 2 μm or more and 4 μm or less.

Further, in order to make the glass layer white, a titanium oxide powder having an average particle size of 0.1 μm or more and 2.0 μm or less is prepared, and 15 parts by mass or more and 25 parts by mass with respect to 100 parts by mass of the glass powder. Titanium oxide powder may be weighed and added as follows.

Next, prepare an organic vehicle. The organic vehicle is obtained by dissolving an organic binder in an organic solvent. For example, the mass ratio of the organic binder to the organic solvent is 2 to 6 with respect to the organic binder 1. Examples of the organic binder include acrylics such as polybutylmethacrylate and polymethylmethacrylate, celluloses such as nitrocellulose, ethylcellulose, cellulose acetate and butylcellulose, polyethers such as polyoxymethylene, polybutadiene, polyisoprene and the like. One kind or two or more kinds selected from the above-mentioned polyvinyls can be mixed and used.

The organic solvent is selected from, for example, carbitol, carbitol acetate, terpineol, metacresol, dimethylimidazole, dimethylimidazolidinone, dimethylformamide, diacetone alcohol, triethylene glycol, paraxylene, ethyl lactate, and isophorone. One type or a mixture of two or more types can be used.

Then, a glass paste is prepared by weighing and mixing a desired amount of glass powder, titanium oxide powder, and organic vehicle. As the blending amount at this time, for example, the amount of the mixed powder of the glass powder and the titanium oxide powder may be 60 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the glass paste, and the balance may be an organic vehicle.

Further, in order to contain the metal in the glass layer 4, a metal powder having an average particle size of 0.1 μm or more and 5 μm or less is prepared, and 0.1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the glass powder. It may be weighed so as to be added to the above glass paste.

Then, the obtained glass paste is printed so as to cover a desired region in the first metal layer, and dried and degreased at a temperature of 80 ° C. or higher and 140 ° C. or lower. Next, a glass layer can be formed by holding the printed glass paste in a nitrogen atmosphere at a maximum temperature of 800 ° C. or higher and 950 ° C. or lower for 2 minutes or longer and 15 minutes or shorter for heat treatment.

When the element mounting portion is not formed when the first metal layer is formed, holes are formed so as to reach the first metal layer after the glass layer is formed, and the metal paste is poured into the formed holes and dried. By firing, the element mounting portion can be formed.

Next, the second metal layer can be formed by screen-printing a circuit pattern on the glass layer using a metal paste containing copper as a main component and then firing it.

By forming up to the second metal layer in this way, the circuit board of the present disclosure can be obtained.

In order to form the element mounting portion shown in FIG. 4, after the printing area is reduced for each layer during recoating by printing the metal paste, or the metal paste is poured into a mask whose diameter expands toward the substrate. It may be dried and fired.

Further, in order to use the element mounting portion shown in FIG. 5, the printing area may be reduced from the area located above the element mounting portion during recoating by printing the metal paste, or the element mounting portion shown in FIG. 5 may be used. After pouring the metal paste into a simple mask, it may be dried and fired.

Further, in order to form the element mounting portion shown in FIG. 6, a glass layer is first formed so as to secure a region to be the element mounting portion, then a metal paste is poured into the secured region, and then the metal paste is dried and fired. Just do it. Alternatively, after forming the glass layer, holes may be formed so as to reach the first metal layer, a metal paste may be poured into the formed holes, and the metal paste may be dried and fired.

Next, the light emitting device, which is an example of the electronic device of the present disclosure, can be obtained, for example, by mounting a light emitting element on the circuit board of the present disclosure.

1: Substrate 2: First metal layer 3: Element mounting part 4: Glass layer 5: Second metal layer 6: Bonding wire 7: Element (light emitting element)
10-14: Circuit board 20: Electronic device (light emitting device)

Claims (7)

A substrate having a first surface and
The first metal layer located on the first surface and
An element mounting portion located connected to the first metal layer and a glass layer located on the first metal layer.
A circuit board comprising a second metal layer located on the glass layer. The circuit board according to claim 1, wherein the first metal layer has an R-shaped end portion in a cross section intersecting the first surface. The circuit board according to claim 1 or 2, wherein the glass layer contains a metal. The circuit board according to any one of claims 1 to 3, wherein the element mounting portion has a diameter that expands toward the substrate. The element mounting portion includes an element mounting surface and a peripheral surface extending from the element mounting surface to the first metal layer, and the peripheral surface includes a portion connected to the element mounting surface and faces the element mounting surface. The circuit board according to any one of claims 1 to 4, which has a first portion having a smaller diameter, and the glass layer is in contact with the first portion. The element mounting portion includes an element mounting surface and a peripheral surface extending from the element mounting surface to the first metal layer, and the peripheral surface includes a portion connected to the first metal layer and is formed on the first metal layer. The circuit board according to any one of claims 1 to 3, wherein the glass layer has a second portion whose diameter becomes smaller toward the second portion, and the glass layer is in contact with the second portion. An electronic device comprising the circuit board according to any one of claims 1 to 6 and an element located on the circuit board.

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