Electronic device

The disclosure herein relates to electronic devices.

Patent Document 1 discloses an electronic device. The contents of the prior art documents are incorporated by reference as descriptions of technical elements in this specification.

<p><patcit num="1"><text>JP 2016-122813 A</text></patcit></p>

<p>Patent document 1 provides an electronic device in which two members are bonded by a metal bonding layer. In Patent Document 1, a semiconductor element is arranged on the upper surface of a substrate. The bottom surface of the substrate and the top surface of the heat radiating member are bonded by a metal bonding layer made of gold or gold alloy. The upper surface of the heat dissipation member faces the entire lower surface of the substrate. In such a configuration, stress such as thermal stress and vibration from the outside concentrates on the end portion of the opposing region between the substrate and the heat radiating member. In view of the above, or in other aspects not mentioned, there is a need for further improvements in electronic devices.</p><p>One object of the disclosure is to provide an electronic device capable of suppressing corrosion.</p>

<p>The electronic device disclosed herein includes a metal member (211) containing any one of copper, copper alloy, aluminum, and aluminum alloy, and a cover having an upper surface disposed on the lower surface side of the metal member and facing the entire lower surface. At least a joining member (212) and metal films (213a, 213b) made of gold or gold alloy are included, and the lower surface of the metal member and the upper surface of the member to be joined are joined together.<u style="Single">metal to</u>A bonding layer (213), and an antirust film (217) provided in a predetermined range from the boundary with the metal bonding layer on at least the surface connected to the lower surface of the metal member.<u style="Single">、</u>metal member<u style="Single">underside of</u>and the member to be joined<u style="Single">top surface of</u>in the area opposite to<u style="Single">of the metal bonding layer in</u>Thickness<u style="Single">、</u>Underside of metal member<u style="Single">flatness of</u>and is smaller than the flatness of the upper surface of the member to be joined.<u style="Single">ing</u>。</p><p>According to the disclosed electronic device, since the thickness of the metal bonding layer is smaller than the flatness of the bottom surface of the metal member and the top surface of the member to be bonded, stress such as thermal stress and vibration from the outside can be applied to the metal member and the member to be bonded. can be accepted. The stress is concentrated at the end of the facing region between the metal member and the member to be joined. An antirust film is provided on the surface that continues to the lower surface of the metal member. Corrosion due to concentration of stress can be suppressed by the antirust film.</p><p>The multiple aspects disclosed in this specification employ different technical means to achieve their respective objectives. Reference numerals in parentheses described in the claims and this section are intended to exemplify the correspondence with portions of the embodiments described later, and are not intended to limit the technical scope. Objects, features, and advantages disclosed in this specification will become clearer with reference to the following detailed description and accompanying drawings.</p>

<figref num="1">1 is a cross-sectional view of an electronic device according to a first embodiment; FIG.</figref><figref num="2">FIG. 4 is a cross-sectional view showing a connection structure between a metal member and a member to be joined;</figref><figref num="3">FIG. 10 is a cross-sectional view showing a connection structure in an electronic device according to a second embodiment;</figref><figref num="4">FIG. 10 is a cross-sectional view showing a connection structure in an electronic device according to a third embodiment;</figref><figref num="5">FIG. 11 is a cross-sectional view showing a connection structure in an electronic device according to a fourth embodiment;</figref>

A plurality of embodiments will be described below based on the drawings. In several embodiments, functionally and/or structurally corresponding and/or related parts may be labeled with the same reference numerals or with reference numerals differing in the hundreds place. For corresponding and/or associated parts, reference can be made to the description of other embodiments.

(First Embodiment) First, a schematic configuration of an electronic device will be described with reference to FIG.

&lt;Electronic Apparatus&gt; As shown in FIG. Housing 5 accommodates electronic component 10 and semiconductor module 110 . The housing 5 is formed using a metal material or a resin material.

Electronic component 10 has leads 11 protruding from the component body. The lead 11 is an external connection terminal. The busbar 12 is a plate-like wiring member. Leads 11 and busbars 12 are made of a highly conductive metal material such as copper. Leads 11 are connected to busbars 12 via metal bonding layers 13 . Metal bonding layer 13 electrically connects lead 11 and bus bar 12 . Metal bonding layer 13 contains at least a gold or gold alloy film, and lead 11 and bus bar 12 are bonded at room temperature.

Semiconductor module 110 has a heat dissipation unit including heat sink 111 and insulating plate 112 , semiconductor chip 114 , and sealing resin body 115 . The heat dissipation unit has a pair of heat sinks 111 between which an insulating plate 112 is arranged. Each of heat sinks 111 is connected to insulating plate 112 via metal bonding layer 113 . The metal bonding layer 113 contains at least a gold or gold alloy film, and each of the heat sinks 111 and the insulating plate 112 are bonded at room temperature. Insulating plate 112 electrically isolates heat sink 111 on semiconductor chip 114 side from heat sink 111 away from semiconductor chip 114 . Insulating plate 112 is formed using a ceramic material such as silicon nitride, aluminum nitride, or silicon carbide.

A semiconductor chip 114 is arranged on one of the heat sinks 111 . Semiconductor chip 114 is arranged on the surface of heat sink 111 opposite to insulating plate 112 . Semiconductor chip 114 is fixed to heat sink 111 . A heat sink 111 to which a semiconductor chip 114 is fixed dissipates at least heat generated by the semiconductor chip 114 . The heat sink 111 to which the semiconductor chip 114 is fixed may be used as wiring for the semiconductor chip 114. FIG. In this case, the heat sink 111 to which the semiconductor chip 114 is fixed is electrically connected to another wiring member (not shown). Another one of the heat sinks 111, that is, the heat sink 111 to which the semiconductor chip 114 is not fixed, is fixed to the cooler 120 via a heat conducting member 130 such as heat dissipating gel, heat dissipating grease, or heat dissipating sheet.

The sealing resin body 115 seals the semiconductor chip 114 . In this embodiment, the encapsulating resin body 115 encapsulates the heat sink 111 to which the semiconductor chip 114 is fixed and the semiconductor chip 114 on each side of the insulating plate 112 . Sealing resin body 115 is a molded body made of epoxy resin, for example. The sealing resin body 115 can be formed by transfer molding, potting, or the like.

Cooler 120 is sometimes referred to as a heat exchange section. Inside the cooler 120, a channel is formed through which a coolant flows. As the refrigerant, a phase-change refrigerant such as water or ammonia, or a phase-invariable refrigerant such as an ethylene glycol-based refrigerant can be used. A semiconductor module 110 is arranged on one surface of the cooler 120 with a heat conducting member 130 interposed therebetween.

&lt;Connection Structure Using Metal Bonding Layer&gt; Next, a connection structure of two members using a metal bonding layer will be described with reference to FIG. The connection structure shown here can be applied to a connection structure between lead 11 and bus bar 12 using metal bonding layer 13 and a connection structure between heat sink 111 and insulating plate 112 using metal bonding layer 113 . FIG. 2 illustrates a connection structure between a metal member 211 and a member to be joined 212 by means of a metal joining layer 213. As shown in FIG. The electronic device includes a metal member 211, a member to be joined 212, and a metal joining layer 213 that joins them.

Metal member 211 is made of any one of copper, copper alloy, aluminum, and aluminum alloy. A joined member 212 is arranged on the lower surface 211a side of the metal member 211 . The metal member 211 has a side surface 211b that is continuous with the lower surface 211a, and an upper surface 211c that is the rear surface of the lower surface 211a.

The member to be joined 212 is connected to the metal member 211 via the metal joining layer 213 . As the constituent material of the member to be joined 212, for example, pure metals such as copper and aluminum, alloys such as copper alloys and aluminum alloys, ceramics such as silicon nitride, aluminum nitride, and silicon carbide, semiconductors such as silicon, and resins are used. be able to. The member to be joined 212 may be formed using a material different from that of the metal member 211, or may be formed using the same material.

The joined member 212 has an upper surface 212a facing the lower surface 211a of the metal member 211. As shown in FIG. The lower surface 211a and the upper surface 212a are surfaces facing the metal member 211 and the member 212 to be joined. The upper surface 212a faces the entire area of the lower surface 211a. The member 212 to be joined has a side surface 212b that continues to the top surface 212a. In this embodiment, the area of the upper surface 212a is larger than the area of the lower surface 211a. In plan view in the thickness direction of the metal bonding layer 213, the upper surface 212a includes the entire lower surface 211a. The thickness direction can also be referred to as the direction in which the metal member 211 and the members to be joined 212 are opposed to each other, or the direction in which they are arranged.

In the connection structure of lead 11 and bus bar 12, lead 11 corresponds to metal member 211, and bus bar 12 corresponds to joined member 212, for example. Also, the heat sink 111 corresponds to the metal member 211 and the insulating plate 112 corresponds to the joined member 212 .

The metal bonding layer 213 bonds the bottom surface 211a of the metal member 211 and the top surface 212a of the member 212 to be bonded. The metal bonding layer 213 includes metal films 213a and 213b made of gold or gold alloy. Metal films 213a and 213b are sometimes referred to as metal layers. The metal film 213a is formed over the entire lower surface 211a of the metal member 211. As shown in FIG. The metal film 213b is formed over the entire upper surface 212a of the member 212 to be joined. In plan view in the thickness direction, the metal film 213b includes the entire area of the metal film 213a.

The metal films 213a and 213b are formed by sputtering. The thickness of each of the metal films 213a and 213b is on the order of nm, for example ten and several nm. The lower surface 211a and the upper surface 212a are mirror-finished by CMP (Chemical Mechanical Polishing) or the like, and then metal films 213a and 213b are formed by sputtering. Then, the metal films 213a and 213b are brought into contact with each other at room temperature in the atmosphere. Thereby, the metal films 213a and 213b can be bonded to each other.

The metal bonding layer 213 has metal films 213a and 213b in the opposing regions between the metal member 211 and the member to be joined 212, and has a metal film 213b outside the opposing regions. Therefore, the thickness of the metal bonding layer 213 differs between the facing region and the outside of the facing region. In the facing region, the thickness t1 of the metal bonding layer 213 is smaller than the flatness F1 of the bottom surface 211a of the metal member 211 and the top surface 212a of the member 212 to be bonded. The thickness t1 is on the order of nm, eg several tens of nm. The flatness F1 is on the order of μm, eg 1 to 3 μm. Metal bonding layers 13 and 113 correspond to metal bonding layer 213 . In FIG. 1, the metal bonding layers 13 and 113 (metal films) are illustrated in a simplified manner.

The electronic device further comprises an antirust film 217 . The antirust film 217 is provided on the side surface 211 b of the metal member 211 within a predetermined range from the boundary with the metal bonding layer 213 . The antirust film 217 is provided at the end of the facing area. The antirust film 217 suppresses metal corrosion. Benzotriazole or derivatives thereof, for example, can be used as the material for the antirust film 217 . In this embodiment, the anticorrosive film 217 continuously surrounds the facing area. The antirust film 217 is provided only on a portion of the side surface 211b in the thickness direction from the boundary with the metal bonding layer 213. As shown in FIG.

Antirust film 217 is formed, for example, before the mirror surface treatment is performed. In this case, the metal film 213a is also formed on the end of the antirust film 217. As shown in FIG. In FIG. 1, illustration of the antirust film 217 is omitted.

&lt;Summary of First Embodiment&gt; Stresses such as thermal stress and external vibration act on the connecting structure portion (bonding joint) of two members. Thermal stress is a composite stress of the first thermal stress and the second thermal stress. It is the stress generated by the factor. The second thermal stress is the stress generated by expansion and contraction factors of the entire electronic device that is assembled using a plurality of different materials. A second thermal stress also acts on joints of like materials. In addition to thermal stress, stress such as vibration transmitted from the outside also acts on the joint. When two members are connected using a joining member such as solder, stress is concentrated on the joining member because the joining member is thick. In contrast, in the present embodiment, the thickness t1 of the metal bonding layer 213 is smaller than the flatness F1 of the bottom surface 211a of the metal member 211 and the top surface 212a of the member 212 to be bonded. Since the metal bonding layer 213 is thin, the stress can be borne by the metal member 211 and the member to be bonded 212 near the metal bonding layer 213 . Therefore, concentration of stress on the metal bonding layer 213 can be suppressed. Thereby, it is possible to have high joint strength and high endurance fatigue strength. Also, since the bonding is performed at room temperature, residual stress during bonding can be minimized.

Stresses are concentrated at the edges of the joint of the two members. That is, it concentrates at the ends of the opposing regions of the two members. The stress concentration causes the structure to expand, making cracks and the like more likely to occur. Due to the structure in which the stress is borne by two members, corrosion may occur in the vicinity of the end portion of the opposing region on the side of the metal member made of metal. On the other hand, in the present embodiment, the side surface 211b of the metal member 211 is provided with an anticorrosion film 217 in a predetermined range from the boundary with the metal bonding layer 213, that is, the boundary with the lower surface 211a. The anticorrosion film 217 covers a portion near the end of the opposing region on the side surface 211b, which is the surface to which the metal bonding layer 213 is not bonded. Therefore, the anticorrosive film 217 can suppress stress from concentrating near the ends of the lower surface 211a of the metal member 211 and causing corrosion on the side surfaces 211b near the ends.

In this embodiment, the area of the upper surface 212a of the member to be joined 212 is larger than the area of the lower surface 211a of the metal member 211. As shown in FIG. A metal film 213b provided on the upper surface 212a encloses the entire area of the lower surface 211a in plan view in the thickness direction. That is, the metal film 213b covers the part of the member 212 to be joined near the end of the opposing region. The metal film 213b is a gold or gold alloy film. Therefore, in a structure in which the member to be joined 212 is made of metal (pure metal or alloy), the metal film 213b can suppress corrosion in the vicinity of the end portion of the opposing region. Especially in this embodiment, since the metal film 213b is provided over the entire upper surface 212a, corrosion can be suppressed over the entire upper surface 212a.

(Second Embodiment) This embodiment is a modification based on the preceding embodiment, and the description of the preceding embodiment can be used.

As shown in FIG. 3, in this embodiment, the antirust film 217 covers the entire surface of the metal member 211 except for the lower surface 211a. That is, it covers the rest of the surface except for the surface on which the metal bonding layer 213 (metal film 213a) is provided. The antirust film 217 covers the entire side surface 211b and the upper surface 211c of the metal member 211. As shown in FIG.

&lt;Summary of Second Embodiment&gt; According to this embodiment, the antirust film 217 covers not only the vicinity of the end of the opposing region where stress is concentrated, but also the entire surface exposed from the metal bonding layer 213. Corrosion can be suppressed over a wide range.

Moreover, since a mask or the like for patterning the antirust film 217 is not required, the formation is easy.

(Third Embodiment) This embodiment is a modification based on the preceding embodiment, and the description of the preceding embodiment can be used.

As shown in FIG. 4, in this embodiment, the metal bonding layer 213 has metal films 213c and 213d in addition to metal films 213a and 213b made of gold or a gold alloy. The metal films 213a and 213b correspond to the first metal films, and the metal films 213c and 213d correspond to the second metal films. Metal films 213a, 213b, 213c, and 213d are sometimes referred to as metal layers. The metal films 213c and 213d are formed using a material having a smaller thermal expansion coefficient than the material (gold or gold alloy) forming the metal films 213a and 213b. The metal film 213c is interposed between the metal film 213a and the lower surface 211a of the metal member 211. As shown in FIG. The metal film 213d is interposed between the metal film 213b and the upper surface 212a of the member 212 to be joined.

Metal films 213c and 213d contain at least one of tantalum, tungsten, titanium, and chromium, for example. These metals have lower coefficients of thermal expansion than gold or gold alloys. Each of metal films 213c and 213d may have a single-layer structure or a multi-layer structure containing any one of tantalum, tungsten, titanium, and chromium, for example. Metal films 213c and 213d are also formed by a sputtering method. The thickness of the metal films 213c and 213d is, for example, equal to or less than that of the metal films 213a and 213b. Therefore, the thickness t1 of the facing region of the metal bonding layer 213 is also on the order of nm (for example, several tens of nm) in this embodiment.

&lt;Summary of Third Embodiment&gt; According to this embodiment, in the configuration in which the metal films 213c and 213d are added, the thickness t1 of the opposing region is equal to the flatness F1 of the lower surface 211a of the metal member 211 and the upper surface 212a of the member 212 to be joined. less than Therefore, stress (for example, thermal stress) can be borne by the metal member 211 and the member to be joined 212 in the vicinity of the metal joining layer 213 .

Furthermore, since the thermal expansion coefficients of the metal films 213c and 213d are small, the concentration of thermal stress on the ends of the opposed regions can be alleviated. As a result, together with the effect of the antirust film 217, corrosion of the metal member 211 can be effectively suppressed.

FIG. 4 shows an example in which the antirust film 217 covers the entire surface of the metal member 211 exposed from the metal bonding layer 213, but the present invention is not limited to this. As shown in the first embodiment (see FIG. 2), a combination with a configuration in which the antirust film 217 is provided only on a partial range of the side surface 211b is also possible.

(Fourth Embodiment) This embodiment is a modification based on the preceding embodiment, and the description of the preceding embodiment can be used.

As shown in FIG. 5, the members to be joined 212 of this embodiment are metal members. The member to be joined 212 is made of any one of copper, copper alloy, aluminum, and aluminum alloy. The member to be joined 212 may be formed using a material different from that of the metal member 211, or may be formed using the same material.

The area of the upper surface 212a of the joined member 212 is equal to the area of the lower surface 211a of the metal member 211. As shown in FIG. In plan view in the thickness direction, the outer contours (ends) of the upper surface 212a and the lower surface 211a substantially match. The antirust film 217 includes an antirust film 217a provided on the metal member 211 and an antirust film 217b provided on the member 212 to be joined. The anticorrosion film 217a is provided on the side surface 211b of the metal member 211 and within a predetermined range from the boundary with the metal bonding layer 213, as in the first embodiment. The anticorrosive film 217b is provided on the side surface 212b of the member 212 to be joined, within a predetermined range from the boundary with the metal joining layer 213. As shown in FIG.

&lt;Summary of Fourth Embodiment&gt; In a structure in which the member to be joined is made of metal, corrosion may occur in the vicinity of the end portion of the facing region on the side of the member to be joined as well. On the other hand, in the present embodiment, the antirust film 217 (rust prevention film 217b ) is provided. The anti-corrosion film 217 covers the portion near the end of the opposing region on the side surface 212b, which is the surface to which the metal bonding layer 213 is not bonded. Therefore, the anticorrosive film 217 can prevent stress from concentrating near the ends of the top surface 212a of the member 212 to be joined and causing corrosion on the side surfaces 212b near the ends. On both sides of the metal member 211 and the member to be joined 212, it is possible to suppress the occurrence of corrosion in the vicinity of the end portions of the opposing regions.

FIG. 5 shows an example in which the antirust films 217 (217a, 217b) are provided only on part of the side surfaces 211b, 212b, but the present invention is not limited to this. As shown in the second embodiment, the antirust film 217 may be provided over the entire surface except for the surface to be bonded with the metal bonding layer 213 . For example, the members to be joined 212 may be provided with an anticorrosion film 217b over the entire surface except for the upper surface 212a. Also, the metal bonding layer 213 may be configured to include the metal films 213c and 213d shown in the third embodiment.

(Other Embodiments) The disclosure in this specification, drawings, etc. is not limited to the illustrated embodiments. The disclosure encompasses the illustrated embodiments and variations thereon by those skilled in the art. For example, the disclosure is not limited to the combinations of parts and/or elements shown in the embodiments. The disclosure can be implemented in various combinations. The disclosure can have additional parts that can be added to the embodiments. The disclosure encompasses omitting parts and/or elements of the embodiments. The disclosure encompasses permutations or combinations of parts and/or elements between one embodiment and another. The disclosed technical scope is not limited to the description of the embodiments. The disclosed technical scope is indicated by the description of the claims, and should be understood to include all changes within the meaning and range of equivalents to the description of the claims.

The disclosure in the specification, drawings, etc. is not limited by the description in the claims. The disclosure in the specification, drawings, etc. encompasses the technical ideas described in the claims, and extends to more diverse and broader technical ideas than the technical ideas described in the claims. Therefore, various technical ideas can be extracted from the disclosure of the specification, drawings, etc., without being bound by the scope of claims.

The spatially relative terms "below" and "above" are utilized herein to facilitate description describing the relationship of one element or feature to other elements or features as shown. ing. Spatially-relative terms can be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the drawings. For example, when the device in the figures is turned over, elements described as "below" other elements or features are oriented "above" other elements or features. Thus, the term "bottom" can encompass both an orientation of up and down. The device may be oriented in other directions (rotated 90 degrees or in other orientations) and the spatially relative descriptors used herein interpreted accordingly. .

An example of room-temperature bonding of the metal member 211 and the member to be bonded 212 in the air has been shown, but the present invention is not limited to this. Room temperature bonding may be performed under vacuum. In the case of bonding under vacuum, both the metal films 213a and 213b may be provided, or only one of the metal films 213a and 213b may be provided. For example, the metal film 213a may not be provided on the lower surface 211a, the metal film 213b may be provided on the upper surface 212a, and room temperature bonding may be performed under vacuum.

Although an example in which the metal film 213c is provided between the metal film 213a and the lower surface 211a and the metal film 213d is provided between the metal film 213b and the upper surface 212a is shown, the present invention is not limited to this. Only one of the metal films 213c and 213d may be provided. For example, in a structure having only metal film 213b, metal film 213d may be provided between metal film 213b and upper surface 212a, and metal film 213c may not be provided on lower surface 211a without metal film 213a.

1...Electronic device, 5...Case, 10...Electronic component, 11...Lead, 12...Bus bar, 13...Metal bonding layer, 110...Semiconductor module, 111 ...heat sink, 112...insulating plate, 113...metal bonding layer, 114...semiconductor chip, 115...sealing resin body, 120...cooler, 130...thermal conduction member , 211...Metal member, 211a...Lower surface, 211b...Side surface, 211c...Top surface, 212...Joined member, 212a...Top surface, 212b...Side surface, 213... Metal bonding layer 213a, 213b... Metal film (first metal film) 213c, 213d... Metal film (second metal film) 217, 217a, 217b... Rust prevention film