ELECTRONIC ELEMENT MOUNTING SUBSTRATE

To reduce the occurrence of scratches in a wide range of a surface of a protruding portion. Solder is firmly fixed to a first metal film. The first metal film has a surface inclined with respect to a first lower surface.

TECHNICAL FIELD

The present disclosure relates to an electronic element mounting substrate.

BACKGROUND OF INVENTION

Recently, an electronic element mounting substrate is known. The electronic element mounting substrate includes a substrate having a protruding portion on a lower surface thereof. One example of such an electronic element mounting substrate is disclosed in Patent Document 1.

CITATION LIST

Patent Literature

Patent Document 1: JP 2002-299514 A

SUMMARY

An electronic element mounting substrate according to an aspect of the present disclosure includes a substrate including an upper surface, a first lower surface, a mounting region located on the upper surface and on which an electronic element is to be mounted, and a plurality of protruding portions located on the first lower surface; and at least one first metal film located on a second lower surface that is a lower surface of the plurality of protruding portions, wherein the first metal film comprises a surface inclined with respect to the first lower surface.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments for implementing the present disclosure will be described. For convenience of description, members having the same functions as those described above are denoted by the same reference signs, and the description thereof is not repeated in some cases.

Configuration of Electronic Device

Hereinafter, some exemplary embodiments of the present disclosure will be described with reference to the drawings. In the following description, an electronic device is formed by mounting an electronic element on an electronic element mounting substrate. In the electronic device, any direction may be vertically upward or vertically downward, but for convenience, an orthogonal coordinate system XYZ is defined, and the positive side in the Z direction is defined as upward.

In the present disclosure, a “surface” refers not only to a surface on the front side but also a side surface and a surface on the back side. When only the surface on the front side is referred to, the term “upper surface” is used. When only the surface on the back side is referred to, the term “lower surface” is used.

First Embodiment

Hereinafter, an electronic device201according to the first embodiment of the present disclosure will be described.

FIG.1Ais a bottom view illustrating the appearance of the electronic device201according to the first embodiment of the present disclosure,FIG.1Bis a vertical cross-sectional view corresponding to a line X1-X1inFIG.1A, andFIG.1Cis a variation ofFIG.1B.

The electronic device201includes an electronic element mounting substrate101, an electronic element102, a connection material103, a lid body104, a lid bonding material105, and a bonding wire106. The electronic element mounting substrate101includes a substrate1, first electrode pads (protruding portions)2ato2e, first metal films3ato3e, second electrode pads4aand4b, and second metal films5aand5b.

For the purpose of simplifying the description, the second electrode pads4aand4b, the second metal films5aand5b, and the bonding wire106will be collectively described in the latter half section (second metal film) of the embodiment of the present disclosure. Therefore, in the description of each embodiment before that section, the description of the second electrode pads4aand4b, the second metal films5aand5b, and the bonding wire106will be omitted.

The substrate1is a base for mounting the electronic element102, and has an upper surface11and a lower surface (first lower surface)12. The substrate1has a mounting region13on which the electronic element102is to be mounted. The mounting region13is located on the upper surface11of the substrate1. Examples of the material of the substrate1include an electrically insulating ceramic and a resin (e.g., a plastic). Examples of the electrically insulating ceramic include an aluminum oxide sintered body, a mullite sintered body, a silicon carbide sintered body, an aluminum nitride sintered body, a silicon nitride sintered body, and a glass ceramic sintered body. Examples of the resin include an epoxy resin, a polyimide resin, an acrylic resin, a phenol resin, and a fluorine-based resin. Examples of the fluorine-based resin include a polyester resin and a tetrafluoroethylene resin.

The substrate1is not limited to a single layer, but can be a layered structure with a plurality of layers. When the substrate1has a layered structure with a plurality of layers, each of the plurality of layers may be made of the above-described material. InFIG.1B, the substrate1has a layered structure having six layers. However, the number of layers of the substrate1is not limited to six, and may be one or more and five or less, or may be seven or more. InFIG.1B, an opening14in which the electronic element102and the like are accommodated is formed in the substrate1. However, the substrate1may have a shape (for example, a flat plate) in which the opening14is not formed.

The size of the substrate1in a plan view is, for example, from 0.3 mm to 10 cm. Examples of the shape of the substrate1in a plan view include a square and a rectangle. The thickness of the substrate1is, for example, 0.2 mm or more.

An electrode may be provided on the surface of the substrate1. The electrode may electrically connect the electronic element mounting substrate101to an external circuit board, or may electrically connect the electronic device201to an external circuit board.

Inside the substrate1, internal wiring formed between a plurality of layers and a through-hole conductor vertically connecting the internal wiring may be provided. The internal wiring and the through-hole conductor may be exposed on the surface of the substrate1. An electrical connection between the electrode and another member may be realized by the internal wiring and the through-hole conductor.

The electronic element mounting substrate101may have a metallized layer. For example, the metallized layer is provided on the surface of the substrate1, and more specifically, is provided in the mounting region13of the substrate1. The metallized layer can be electrically connected to the electronic element102.

When the substrate1is made of an electrically insulating ceramic, the metallized layer is made of, for example, any one of tungsten (W), molybdenum (Mo), manganese (Mn), silver (Ag), and copper (Cu), or an alloy containing at least one of them. When the substrate1is made of a resin, the metallized layer is made of, for example, any one of copper, gold (Au), aluminum (Al), nickel (Ni), molybdenum, and titanium (Ti), or an alloy containing at least one of these metals. The same applies to the electrode, the internal wiring, the through-hole conductor, and the first electrode pads2ato2e.

The first electrode pads2ato2ecorrespond to a plurality of protruding portions according to the present disclosure. The first electrode pads2ato2eare located on the lower surface12of the substrate1. and more specifically, are provided on a surface of the substrate1on the opposite side to the mounting region13. The number of first electrode pads provided on the electronic element mounting substrate101is not limited to five in the same row, and may be two or more and four or less in the same row, or may be six or more in the same row.

The first metal films3ato3eare located on lower surfaces (second lower surfaces) of the first electrode pads2ato2e, respectively, and more specifically, are provided on the lower surfaces of the first electrode pads2ato2e. That is, the first electrode pads2ato2eand the first metal films3ato3ehave a one-to-one correspondence.

At least two of the first metal films3ato3emay be connected to each other. As long as the electronic element mounting substrate101includes at least one of the first metal films3ato3e, the other films may be omitted. From these forms, the number of first metal films may be one. Of course, the number of first metal films may be two or more.

FIG.2Ais a cross-sectional view illustrating the layered structure in the first metal film3, andFIG.2Bis a cross-sectional view illustrating the layered structure in a second metal film5. The first metal film3is any one of the first metal films3ato3e, and the second metal film5is any one of the second metal films5aand5b.

As illustrated inFIG.2A, the first metal film3includes a nickel coating31and a gold coating32. The nickel coating31contains nickel as a main component, and is provided on the substrate1side with respect to the gold coating32. The film thickness of the nickel coating31is, for example, from 0.03 μm to 3.0 μm. The gold coating32contains gold as a main component, and is provided on the opposite side to the substrate1with respect to the nickel coating31and covers at least a part of the nickel coating31. That is, the gold coating32may cover the entirety of the nickel coating31, or may cover a part of the nickel coating31. The film thickness of the gold coating32is, for example, from 0.03 μm to 0.30 μm. The first metal film3preferably has a layered structure, but may have a single-layer structure. The same applies to the second metal film5described below.

The electronic element102is fixed on the mounting region13. Examples of the electronic element102include a CCD-type imaging element, a CMOS-type imaging element, a light emitting element such as an LED or an LD, and an integrated circuit. CCD is an abbreviation of “Charge Coupled Device”. CMOS is an abbreviation of “Complementary Metal Oxide Semiconductor”. LED is an abbreviation of “Light Emitting Diode”. LD is an abbreviation of “Laser Diode”. The electronic element102is connected to the mounting region13via the connection material103. Examples of the material of the connection material103include silver epoxy and thermosetting resin.

The lid body104is fixed to the upper surface of the substrate1and covers the electronic element102. In a case where the electronic element102is any one of the imaging element and the light emitting element exemplified above, as an example of a material of the lid body104, a material having high transparency such as a glass material is exemplified. In the case where the electronic element102is the integrated circuit exemplified above, examples of the material of the lid body104include a metal material and an organic material.

A frame-shaped body surrounding the electronic element102and supporting the lid body104may be provided on the upper surface of the electronic element mounting substrate101. The frame-shaped body need not be provided in the electronic element mounting substrate101. The material of the frame-shaped body and the material of the substrate1may be the same or different.

The lid bonding material105bonds the substrate1and the lid body104. Examples of the material of the lid bonding material105include a thermosetting resin, low-melting-point glass, and a brazing material made of a metal component. When a frame-shaped body made of a material different from that of the substrate1is provided on the electronic element mounting substrate101, the lid bonding material105may be made of the same material as that of the frame-shaped body. At this time, by providing the lid bonding material105to be thick, the lid bonding material105can have a function of bonding the substrate1and the lid body104and can function as a frame-shaped body that supports the lid body104. In a case where a frame-shaped body made of the same material as the substrate1is provided in the electronic element mounting substrate101, the frame-shaped body and the lid body104may be configured as the same member.

Production Method

An example of a method for manufacturing the electronic element mounting substrate101and the electronic device201of the present embodiment will be described. An example of the manufacturing method described below is a method of manufacturing the substrate1using a multi-piece wiring substrate.

(a) First, a ceramic green sheet constituting the substrate1is formed. For example, in order to obtain the substrate1made of an aluminum oxide (Al2O3)-based sintered body, a powder of, for example, silica (SiO2), magnesia (MgO), or calcia (CaO) is added as a sintering aid to Al2O3powder. Further, a suitable binder, solvent, and plasticizer are added, and then a mixture thereof is kneaded to form a slurry. Then, multi-piece ceramic green sheets are obtained by a formation method, such as a doctor blade method or a calendar roll method.

When the substrate1is made of, for example, a resin, the substrate1can be formed by a transfer molding method, an injection molding method, pressing with a mold, or the like, using a mold that can be molded into a predetermined shape. The substrate1may be made of a base material made of glass fibers impregnated with a resin, such as a glass epoxy resin. In this case, the substrate1can be formed by impregnating a base material made of glass fibers with a precursor of an epoxy resin and thermally curing the epoxy resin precursor at a predetermined temperature.

(b) Next, by a screen printing method or the like, a metal paste is applied to or made to fill portions of the ceramic green sheet obtained in the step (a) where the electrode pads, the internal wiring electrical conductor and/or the internal through-hole conductor are to be formed. This metal paste is created so as to have appropriate viscosity by adding a suitable solvent and binder to a metal powder formed of the above-described metal materials, and kneading the mixture. The metal paste may contain glass or ceramics in order to increase the bonding strength with the substrate1.

When the substrate1is made of a resin, the electrode pads, the internal wiring electrical conductor and/or the internal through-hole conductor can be formed by a sputtering method, a vapor deposition method, or the like. The above may be manufactured by using a plating method after providing a metal film on the surface.

(c) Next, the above-described green sheet is processed by using a die or the like. Here, in a case where the substrate1has an opening portion, a notch, or the like, the opening portion, the notch, or the like may be formed at a predetermined position on the green sheets to be the substrate1.

(d) Next, the ceramic green sheets to be the respective insulating layers of the substrate1are layered and pressed. In this manner, green sheets to be the insulating layers may be layered to fabricate a ceramic green sheet layered body to be the substrate1. At this time, by using a die, punching, a laser, or the like. an opening portion may be provided at a predetermined position on the ceramic green sheets of a plurality of layers that have been layered

(e) Next, the ceramic green sheet layered body is fired at a temperature of about 1500° C. to 1800° C. to obtain a multi-piece wiring substrate in which a plurality of substrates1are arrayed. In this step, the above-described metal paste is fired simultaneously with the ceramic green sheets to be the substrate1to form the electrode pads, the internal wiring electrical conductor, and/or the internal through-hole conductor.

(f) Next, the multi-piece wiring substrate obtained by firing is divided into a plurality of substrates1. For this division, a method in which a dividing groove is formed in the multi-piece wiring substrate along a portion to be the outer edge of the substrate1, and the multi-piece wiring substrate is broken and divided along the dividing groove can be used, or a method in which the multi-piece wiring substrate is cut along a portion to be the outer edge of the substrate1by a slicing method or the like can be used. The dividing grooves can be formed by cutting into the multi-piece wiring substrate to a depth smaller than the thickness of the multi-piece wiring substrate by using a slicing device after firing. The dividing grooves may be formed by pressing a cutter blade against the ceramic green sheet layered body for the multi-piece wiring substrate or by cutting the ceramic green sheet layered body with a slicing device to a depth smaller than the thickness of the ceramic green sheet layered body. Before or after the multi-piece wiring substrate is divided into the plurality of substrates1, the electrode pads, the internal wiring electrical conductor, and the internal through-hole conductor may be plated thereon.

(g) Next, the electronic element102is mounted on the mounting region13of the substrate1. The electronic element102is electrically bonded to the substrate1by a connection member such as wire bonding. At this time, the electronic element102or the substrate1is provided with the connection material103or the like and fixed to the substrate1. Alternatively, the lid body104may be bonded after the electronic element102is mounted on the substrate1.

the electronic device201can be fabricated by fabricating the substrate1and mounting the electronic element102as in the steps (a) to (g) described above. The order of the steps (a) to (g) is not specified as long as it is a workable order.

All the steps for obtaining the electronic element mounting substrate101from the multi-piece wiring substrate have been described above, and the plating method will be described in detail below.FIG.3is a view illustrating an example of a method of providing the gold coating32on the surface of the nickel coating31, and is a perspective view illustrating a step of packing an intermediate body301of the electronic element mounting substrate101in a jig302.FIG.4is a view illustrating an example of a method of providing the gold coating32on the surface of the nickel coating31, and is a front view illustrating a step of plating the intermediate body301packed in the jig302. The intermediate body301includes the nickel coating31similarly to the electronic element mounting substrate101, and, unlike the electronic element mounting substrate101, does not include the gold coating32.

As an example of a method of providing the gold coating32on the surface of the nickel coating31(covering at least a part of the nickel coating31), a method including the steps illustrated inFIGS.3and4is considered.

In the step illustrated inFIG.3, the intermediate body301is packed in a jig302. The outline of the jig302may be a rectangular parallelepiped as illustrated inFIG.3. At this time, in the jig302, a large number of spaces are formed along the normal direction of a pair of surfaces303and304(seeFIG.4) having the largest area among the surfaces constituting the rectangular parallelepiped. Each of the plurality of spaces is filled with the intermediate body301. The number of spaces is, for example, about 250.

In the step illustrated inFIG.4, first, the jig302filled with the intermediate body301and gold electrodes305and306are placed in a gold complex bath307. Then, the surfaces303and304are made to oppose the gold electrodes305and306, respectively, and the intermediate body301packed in the jig302is subjected to plating to provide the gold coating32on the intermediate body301.

After the step illustrated inFIG.4, the intermediate body301provided with the gold coating32is subjected to cleaning. At this time, the intermediate body301provided with the gold coating32may be removed from the jig302and cleaned; however, the intermediate body301is preferably cleaned while the intermediate body301is packed in the jig302. In other words, it is preferable that the intermediate body301provided with the gold coating32be cleaned together with the jig302(without removing the intermediate body301provided with the gold coating32from the jig302). Thus, a step of packing the intermediate body301provided with the gold coating32in a jig different from the jig302can be omitted, whereby the number of manufacturing steps of the electronic element mounting substrate101can be reduced.

FIG.5is a top view illustrating a trend308, which is rough, of the film thickness distribution of the gold coating32provided on the intermediate body301in the step illustrated inFIG.4. The trend308indicates a trend that the film thickness of the gold coating32provided on the intermediate body301increases as the thickness from the intermediate body301increases. In the step illustrated inFIG.4, the intermediate body301is disposed such that a normal direction309of the upper surface and the lower surface of the intermediate body301is substantially perpendicular to the direction in which the gold electrode305and the gold electrode306are arranged (the horizontal direction in the drawing). According to the step illustrated inFIG.4, the trend308includes two components (1) and (2) to be described below.

As another method of fabricating the first metal film3of the electronic element mounting substrate101of the present embodiment, for example, a method of fabricating the first metal film3by coating plating by an electrolytic plating method is exemplified. In the formation of the plating film by the electrolytic plating method, changing the resistance of the electrolytic plating pattern through which a current is passed can be contemplated. For example, the first metal film3may be fabricated by decreasing the electrical resistance of the electrolytic plating pattern on a side where the plating film is thickened and increasing the electrical resistance of the other side. For example, in the formation of the plating film by the electrolytic plating method, the first metal film may be fabricated by increasing the current on the side where the plating film is thickened.

(1) The film thickness of the gold coating32provided on the intermediate body301tends to monotonically decrease with increasing distance to the gold electrode305.

(2) The film thickness of the gold coating32provided on the intermediate body301tends to monotonically decrease with increasing distance to the gold electrode306.

In the electronic element mounting substrate101, the first metal films3ato3ehave surfaces33ato33einclined with respect to the lower surface12of the substrate1, respectively.

The surfaces33ato33eare not planes substantially parallel to the lower surface12of the substrate1. Accordingly, the occurrence of scratches in a wide range of the surfaces33ato33edue to contact of an object in the wide range of the surfaces33ato33ecan be reduced.

The surface area of the first metal films3ato3eis increased. Therefore, the solder can be firmly fixed to the first metal films3ato3e.

In the first metal film3a, the thickness of the first metal film3amonotonically decreases in a direction D1from the peak thickness portion34ahaving a maximum thickness toward the inside of the substrate1in a plan view of the substrate1. A specific example of the component from which the monotonic decrease is derived is any one of the components (1) and (2). The direction D1is merely a direction, and the start point of the monotonic decrease is the peak thickness portion34a, but an end point thereof may be anywhere up to the end portion of the first metal film3aon the opposite side to the peak thickness portion34a.

The peak thickness portion34amay have not only a dotted shape but also a linear shape. When the peak thickness portion34ahas a linear shape, the direction D1may be different depending on which point on the peak thickness portion34ais selected. When the peak thickness portion34ahas a linear shape, a plurality of directions D1different from each other may be defined for a plurality of points on the peak thickness portion34a, and the thickness of the first metal film3amay monotonically decrease in the plurality of directions D1.

As a result, the components (1) and/or (2) in the example illustrated inFIGS.3and4can be effectively utilized to realize the surface33a.

The monotonic decrease is the same for the first metal films3bto3e. The monotonic decrease is the same even when the first metal films3ato3eare regarded as one first metal film.

The electronic element mounting substrate101includes a plurality of first metal films3ato3ehaving surfaces33ato33einclined substantially parallel to each other in a cross-sectional view (a cross-sectional view in the thickness direction of the substrate). The surfaces33ato33eof the plurality of first metal films3ato3eare inclined on the straight line L1(on the same straight line) in the cross-sectional view. Here, “substantially parallel” means that the surfaces33ato33eare preferably strictly parallel to each other, but a part of the surfaces33ato33emay be slightly inclined with respect to the rest. Here, the “straight line L1” is a straight line along each of the surfaces33ato33e. At this time, in a case where each of the surfaces33ato33eis not a straight line in the cross-sectional view, for example, a straight line connecting at least the peak thickness portions of the surfaces33ato33emay be the “straight line L1”.

As a result, the components (1) and/or (2) in the example illustrated inFIGS.3and4can be effectively utilized to realize the surfaces33ato33e.

In a cross-sectional view in the thickness direction of the substrate1, the shape of the first metal film3ais substantially trapezoidal. In this case, since the first metal film3ais not sharp, the likelihood that an object in contact with the first metal film3ais greatly damaged can be reduced. The same applies to the first metal films3bto3e.

On the other hand, as illustrated inFIG.1C, the shape of the first metal film3amay be substantially triangular in a cross-sectional view in the thickness direction of the substrate1. In this case, since the inclination angle of the surface33awith respect to the lower surface12of the substrate1can be made steep, the occurrence of scratches in a wide range of the surface33acan be further reduced. The same applies to the first metal films3bto3e.

The thickness T1, which is the maximum value of the thickness of the first metal film3a, is from 0.06 μm to 3.30 μm. Specifically, the maximum value of the film thickness of the nickel coating31in the first metal film3ais from 0.03 μm to 3.0 μm, and the maximum value of the film thickness of the gold coating32in the first metal film3ais from 0.03 μm to 0.30 μm. The same applies to the first metal films3bto3e.

The thickness T2, which is the minimum value of the thickness of the first metal film3e, may be, for example, 50 to 99% of the thickness T1, which is the maximum value of the thickness of the first metal film3a.

As illustrated inFIG.1B, points Ta and Tb of the first metal film3aare defined from the upstream side of the direction D1described above. At this time, the film thickness of the first metal film3asatisfies the relation of point Tb<point Ta.

When the first metal films3ato3eare regarded as one first metal film, as illustrated inFIG.1B, points Ta to Tj of the first metal film are defined from the upstream side of the direction D1described above. At this time, the film thickness of the first metal film satisfies the relation of point Tj<point Ti<point Th<point Tg<point Tf<point Te<point Td<point Tc<point Tb<point Ta.

Second Embodiment

Hereinafter, the electronic device201according to a second embodiment of the present disclosure will be described.

FIG.6Ais a bottom view illustrating an appearance of the electronic device201according to the second embodiment of the present disclosure, andFIG.6Bis a vertical cross-sectional view corresponding to the line X1-X1inFIG.6A.

The electronic element mounting substrate101of the electronic device201according to the second embodiment of the present disclosure includes a plurality of first metal films3ato3ehaving surfaces33ato33einclined at positive and negative opposite inclinations with respect to the normal line15of the substrate1in a cross-sectional view in the thickness direction of the substrate1. InFIG.6B, the inclination angle of the surfaces33ato33ewith respect to the normal line15is less than 90°, the clockwise inclination with respect to the normal line15is a positive inclination, and the counterclockwise inclination with respect to the normal line15is a negative inclination. The surfaces33ato33eof the plurality of first metal films3ato3eare inclined on two straight lines L2and L3that are substantially line-symmetrical to each other with respect to the normal line15of the substrate1in the cross-sectional view. Here, the term “substantially line-symmetrical” means that the straight line L2and the straight line L3are preferably strictly line-symmetrical to each other, but the straight line L2may be slightly deviated from the line symmetry with respect to the straight line L3. Here, the “straight line L2” and the “straight line L3” are straight lines along the respective surfaces of the plurality of first metal films3ato3e, which are inclined in positive and negative directions opposite to each other with respect to the normal line15. At this time, if the “straight line L2” and the “straight line L3” are not straight lines, they may be straight lines connecting at least the thickest portions. The normal line15of the substrate1is a straight line orthogonal to the upper surface and the lower surface of the substrate1, and is a straight line in the Z direction because the upper surface and the lower surface of the substrate1can be approximated by the XY plane.

In the electronic device201according to the second embodiment of the present disclosure, it can be said that the direction D1defined in the first metal films3aand3band the direction D1defined in the first metal films3dand3eare opposite to each other in the cross-sectional view. It can be said that the direction D1defined in the left half of the first metal film3cis the same direction as defined in the first metal films3aand3b, and the direction D1defined in the right half of the first metal film3cis the same direction as defined in the first metal films3dand3e.

As a result, the components (1) and (2) in the example illustrated inFIGS.3and4can be effectively utilized to realize the surfaces33ato33e.

When the first metal films3ato3eare regarded as one first metal film, as illustrated inFIG.6B, points Ta to Tj of the first metal film are defined at the same positions as those illustrated inFIG.1B. A point on the normal15to the first metal film3cis defined as a point Tk. At this time, the film thickness of the first metal film satisfies the relations of point Tk<point Te<point Td<point Tc<point Tb<point Ta and point Tk<point Tf<point Tg<point Th<point Ti<point Tj.

Third Embodiment

Hereinafter, the electronic device201according to a third embodiment of the present disclosure will be described.

FIG.7Ais a bottom view illustrating the appearance of the electronic device201according to the third embodiment of the present disclosure,FIG.7Bis a vertical cross-sectional view corresponding to the line X1-X1inFIG.7A, andFIG.7Cis a variation ofFIG.7B.

In the electronic device201according to the third embodiment of the present disclosure, the electronic element mounting substrate101includes a thin film6. The thin film6is located between two adjacent ones of the plurality of first metal films3ato3eat least on the lower surface12of the substrate1. The thin film6is provided covering the lower surface12of the substrate1. Examples of the thin film6include an alumina coat and an inorganic film. Thus, the lower surface12of the substrate1can be protected by the thin film6.

According toFIG.7B, the thin film6protrudes from at least one of two adjacent first metal films3ato3ewith the lower surface12of the substrate1as a reference. The two adjacent ones of the plurality of first metal films3ato3eare any of the first metal films3aand3b, the first metal films3band3c, the first metal films3cand3d, and the first metal films3dand3e. At least one of two adjacent ones of the plurality of first metal films3ato3eis at least one first metal film of the two adjacent ones of the plurality of first metal films3ato3e. InFIG.7B, the thin film6protrudes from all of the plurality of first metal films3ato3ewith the lower surface12of the substrate1as a reference. Here, the fact that the thin film6protrudes from the at least one first metal film with the lower surface12of the substrate1as a reference means that the lower surface of the thin film6is located below the at least one first metal film. The above configuration makes it difficult for objects to come into contact with the first metal films3ato3e.

According toFIG.7C, at least one of two adjacent ones of the plurality of first metal films3ato3eprotrudes from the thin film6with the lower surface12of the substrate las a reference. InFIG.7C, all of the plurality of first metal films3ato3eprotrude from the thin film6with the lower surface12of the substrate1as a reference. Here, the fact that the at least one first metal film protrudes from the thin film6with the lower surface12of the substrate1as a reference means that the lower surface of the at least one first metal film is located below the thin film6. According to the above configuration, when an electronic element or the like is connected to the first metal films3ato3efrom the outside of the electronic element mounting substrate101, the likelihood that the thin film6hinders the connection can be reduced.

According toFIGS.7B and7C, a part of the thin film6is located on a part of the lower surface (third lower surface) of each of the first electrode pads2ato2e. According to the above configuration, a part of the lower surface of each of the first electrode pads2ato2ecan be protected by the thin film6.

The electronic element mounting substrate101of the electronic device201according to the third embodiment of the present disclosure includes a plurality of first metal films3ato3ehaving surfaces33ato33einclined at positive and negative opposite inclinations with respect to the normal line15of the substrate1in a cross-sectional view in the thickness direction of the substrate1. InFIGS.7B and7C, the inclination angle of the surfaces33ato33ewith respect to the normal line15is less than 90°, the clockwise inclination with respect to the normal line15is a positive inclination, and the counterclockwise inclination with respect to the normal line15is a negative inclination. The surfaces33ato33eof the plurality of first metal films3ato3eare inclined on two straight lines L2and L3that are substantially line-symmetrical to each other with respect to the normal line15of the substrate1in the cross-sectional view.

When the first metal films3ato3eare regarded as one first metal film, as illustrated inFIGS.7B and7C, points Ta to Tk of the first metal film are defined at the same positions as those illustrated inFIG.6B. At this time, the magnitude relationship between the points Ta to Tk is the same betweenFIG.6BandFIGS.7B and7C.

Second Metal Film

Hereinafter, the second electrode pads4aand4b, the second metal films5aand5b, and the bonding wire106will be described with reference to the above-described embodiments. As the configuration of each of the electronic element102, the connection material103, the lid body104, the lid bonding material105, the substrate1, the first electrode pads2ato2e, and the first metal films3ato3e, the configuration illustrated in each of the embodiments described above can be appropriately used.

The second electrode pads4aand4bare located on the surface of substrate1, and more specifically, are provided on the side of the substrate1on which the electronic element102is to be mounted (upper surface of substrate1). The second electrode pads4aand4bare electrically connected to the electronic element102. In each of the above-described embodiments, the number of the second electrode pads is two, but is not limited thereto, and the number of the second electrode pads may be one, or may be three or more.

An electrode may be provided on the surface of the substrate1. The electrode may electrically connect the electronic element mounting substrate101to an external circuit board, or may electrically connect the electronic device201to an external circuit board.

Inside the substrate1, internal wiring formed between a plurality of layers and a through-hole conductor vertically connecting the internal wiring may be provided. The internal wiring and the through-hole conductor may be exposed on the surface of the substrate1. The electrode may be electrically connected to the second electrode pads4aand/or4bby the internal wiring and the through-hole conductor.

When the substrate1is made of an electrically insulating ceramic, the second electrode pads4aand4bare made of, for example, any one of tungsten, molybdenum, manganese, silver, and copper, or an alloy containing at least one of the aforementioned. When the substrate1is made of a resin, the second electrode pads4aand4bare made of, for example, any one of copper, gold, aluminum, nickel, molybdenum, and titanium, or an alloy containing at least one of the aforementioned. The same applies to each of the electrode, the internal wiring, and the through-hole conductor.

The second metal films5aand5bare located on the surface of the substrate1. To be more specific, the second metal films5aand5bare provided on the surfaces of the second electrode pads4aand4blocated on the surface of the substrate1. The second metal film is provided on the surface of each second electrode pad.

As illustrated inFIG.2B, the second metal film5, which is any one of the second metal films5aand5b, includes a nickel coating51and a gold coating52. The nickel coating51contains nickel as a main component, and is provided on the substrate1side with respect to the gold coating52. The film thickness of the nickel coating51is, for example, from 0.03 μm to 3.0 μm. The gold coating52contains gold as a main component, and is provided on the opposite side to the substrate1with respect to the nickel coating51, covering at least a part of the nickel coating51. That is, the gold coating52may cover the entirety of the nickel coating51, or may cover a part of the nickel coating51. The film thickness of the gold coating52is, for example, from 0.03 μm to 0.30 μm. As described above, the second metal film5preferably has a layered structure, but may have a single-layer structure.

The bonding wire106is wiring for electrically connecting the second electronic element102and the second metal film5(and thus the electrode pad4). Although not illustrated, the second electrode pad4is a convenient representation of one of the second electrode pads4aand4bcorresponding to the second metal film5.

In the above description with reference toFIGS.3to5, the nickel coating31and the gold coating32may be regarded as the nickel coating51and the gold coating52, respectively. Thus, the description with reference toFIGS.3to5can be interpreted as an example of a method of providing the gold coating52on the surface of the nickel coating51(covering at least a part of the nickel coating51).

The second metal films5aand5blocated on the surface of the substrate1have surfaces53aand53binclined with respect to the surface of the substrate1, respectively. The surface of the substrate1refers to, for example, an upper surface of the substrate1or a surface on which an element is to be mounted. Here, it can be said that the surfaces53aand53bbeing inclined with respect to the surface of the substrate1more specifically means that the surfaces53aand53bare inclined with respect to the internal wall surfaces16aand16bof the substrate1, respectively. In the second metal films5aand5b, the thicknesses of the second metal films5aand5bamonotonically decrease in a direction D1′ that is the same as the direction D1from the peak thickness portion34aof the first metal film3ahaving a maximum film thickness in the first metal film3atoward the inside of the substrate1in the plan view of the substrate1.

When the inclination directions of the second metal films5aand5bin the same row are constant, the angle formed with the capillaries is easily kept constant, and wire bonding can be stably performed. Variations in the position of the wire bond contact can be reduced. Therefore, wire bonding defects can be reduced.

Conclusion

An electronic element mounting substrate according to a first aspect of the present disclosure includes a substrate including an upper surface, a first lower surface, a mounting region located on the upper surface and on which an electronic element is to be mounted, and a plurality of protruding portions located on the first lower surface; and at least one first metal film located on a second lower surface that is a lower surface of the plurality of protruding portions, in which the first metal film includes a surface inclined with respect to the first lower surface.

The surface of the first metal film is not a plane substantially parallel to the lower surface of the substrate. Thus, the occurrence of scratches in a wide range of the surface of the first metal film due to contact of an object with the wide range of the surface of the first metal film can be reduced.

The surface area of the first metal film is increased. Therefore, solder can be firmly fixed to the first metal film.

According to an electronic element mounting substrate according to a second aspect of the present disclosure, in the first aspect, in the first metal film, a thickness of the first metal film monotonically decreases in a direction from a peak thickness portion having a maximum thickness toward an inner side of the substrate in a plan view of the substrate.

In the first or second aspect, an electronic element mounting substrate according to a third aspect of the present disclosure includes the first metal film in a plurality and the plurality of first metal films include surfaces inclined substantially parallel to each other in a cross-sectional view in a film thickness direction of the substrate.

According to an electronic element mounting substrate according to a fourth aspect of the present disclosure, in the third aspect, the surfaces of the plurality of first metal films are inclined on the same straight line in the cross-sectional view.

According to each of the above-described configurations, the surface of the first metal film can be realized by effectively utilizing the rough trend of the distribution of the film thickness of the first metal film.

In the first or second aspect, an electronic element mounting substrate according to a fifth aspect of the present disclosure includes the first metal film in a plurality and the plurality of first metal films include surfaces inclined at positive and negative opposite inclinations with respect to a normal line of the substrate in a cross-sectional view in a film thickness direction of the substrate.

According to an electronic element mounting substrate according to a sixth aspect of the present disclosure, in the fifth aspect, the surfaces of the plurality of first metal films are inclined on two straight lines that are substantially line-symmetrical to each other with respect to the normal line of the substrate in the cross-sectional view.

According to each of the above-described configurations, the surface of the first metal film can be realized by further effectively utilizing the rough trend of the distribution of the film thickness of the first metal film.

In any one of the first to sixth aspects, an electronic element mounting substrate according to a seventh aspect of the present disclosure further includes, on the first lower surface, a thin film located between two adjacent ones of the plurality of first metal films.

According to the above configuration, the lower surface of the substrate can be protected by the thin film.

According to an electronic element mounting substrate according to an eighth aspect of the present disclosure, in the seventh aspect, at least one of two adjacent ones of the plurality of first metal films protrudes from the thin film with respect to the first lower surface.

According to the above configuration, when an electronic element or the like is connected to the first metal films from the outside of the electronic element mounting substrate, the likelihood of the thin film hindering the connection can be reduced.

According to an electronic element mounting substrate according to a ninth aspect of the present disclosure, in the seventh aspect, the thin film protrudes from at least one of two adjacent ones of the plurality of first metal films with respect to the first lower surface.

The above configuration makes it difficult for objects to come into contact with the first metal films.

According to an electronic element mounting substrate according to a tenth aspect of the present disclosure, in any one of the seventh to ninth aspects, a portion of the thin film is located on a portion of a third lower surface that is a lower surface of the protruding portion.

According to the configuration, a part of the lower surface of the protruding portion can be protected by the thin film.

According to an electronic element mounting substrate according to an eleventh aspect of the present disclosure, in any one of the first to tenth aspects, a shape of the first metal film is substantially triangular or substantially trapezoidal in a cross-sectional view in a film thickness direction of the substrate.

When the shape of the first metal film is a substantially triangular shape in a cross-sectional view in the film thickness direction of the substrate, the inclination angle of the surface of the first metal film with respect to the lower surface of the substrate can be made steep, and thus the occurrence of scratches in a wide range of the surface of the first metal film can be further reduced. In the case where the shape of the first metal film is a substantially trapezoidal shape in the cross-sectional view, the first metal film is not sharp. Therefore, the likelihood of an object in contact with the first metal film being greatly damaged can be reduced.

According to an electronic element mounting substrate according to a twelfth aspect of the present disclosure, in any one of the first to eleventh aspects, a maximum value of a film thickness of the first metal film is from 0.06 μm to 3.30 μm.

According to an electronic element mounting substrate according to a thirteenth aspect of the present disclosure, in any one of the first to twelfth aspects, the first metal film includes a nickel coating containing nickel as a main component; and a gold coating provided covering at least a part of the nickel coating, the gold coating containing gold as a main component, wherein a maximum value of a film thickness of the gold coating in the first metal film is from 0.03 μm to 0.30 μm. The main component may be, for example, a component which is contained in an amount of 50% or more of the whole, or may be a component which is contained in the largest amount among the all of the components.

According to a fourteenth aspect of the present disclosure, the electronic element mounting substrate according to any one of the first to thirteenth aspects further includes a second metal film located on a surface of the substrate, wherein the second metal film has a surface inclined with respect to the surface of the substrate.

According to an electronic element mounting substrate according to a fifteenth aspect of the present disclosure, in the fourteenth aspect, in the second metal film, a thickness of the second metal film monotonically decreases in the same direction as a direction from a peak thickness portion of the first metal film having a maximum thickness in the first metal film toward an inner side of the substrate in a plan view of the substrate.

The present disclosure is not limited to each of the embodiments described above, and various modifications can be made within the scope indicated by the claims, and an embodiment obtained by appropriately combining technical means disclosed in different embodiments is also included in a technical scope of the present disclosure.

REFERENCE SIGNS