Devices, electrical devices, and circuit boards

Abstract

According to the present invention, sufficient interfacial strength is ensured in a solder joint portion even after undergoing a high-temperature process, such as reflow junction, and the like. This device has a base, an electrode containing Ni and Cu, and a joint part positioned on the electrode. The joint part includes a barrier layer, a joint layer, and a solder layer in order from the electrode side. The barrier layer contains Mo as a main component, and the joint layer contains at least one among Ni, Ag, Au, and Cu.

Description

【Technical Field】 【0001】 The present disclosure relates to an apparatus, an electrical device, and a substrate. 【Background Art】 【0002】 An apparatus for mounting electronic components is mounted on a mounting substrate of an electrical device by solder. 【0003】 For example, the surface acoustic wave device described in Citation 1 includes a pad (electrode) provided on a piezoelectric substrate and an under bump metal provided on the pad to facilitate bonding with solder. 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 International Publication WO2015 / 022931 【Summary of the Invention】 【0005】 An apparatus according to one aspect of the present disclosure includes a substrate having a first surface, an electrode located on the first surface of the substrate and containing Ni and Cu, and a bonding portion located on the electrode. The bonding portion includes a barrier layer, a bonding layer, and a solder layer in this order from the electrode side. The barrier layer contains Mo as a main component, and the bonding layer contains at least one of Ni, Ag, Au, and Cu. 【Brief Description of the Drawings】 【0006】 [Figure 1] It is a cross-sectional structure diagram of an apparatus according to Embodiment 1 of the present disclosure. [Figure 2] It is a cross-sectional structure diagram showing an electronic module according to Embodiment 1 of the present disclosure. [Figure 3] It is a micrograph of a bonding portion according to Embodiment 1 of the present disclosure. [Figure 4] It is an enlarged view of region R in FIG. 3. [Figure 5]This is a cross-sectional structural diagram of an elastic wave apparatus according to Embodiment 2 of the present disclosure. [Figure 6] These are micrographs of the junctions of electronic modules in the examples and comparative examples. [Figure 7] This graph shows the results of evaluating the joint strength for the comparative example. [Figure 8] This graph shows the results of evaluating the joint strength for the comparative example. [Figure 9] This graph shows the results of evaluating the joint strength for the comparative example. [Figure 10] This graph shows the results of evaluating the bonding strength for each example. [Modes for carrying out the invention] 【0007】 When high-temperature processes such as reflow bonding are repeatedly performed, or when equipment is used at high temperatures for extended periods, various metal materials, including underbump metal, react with the metals contained in the solder. This can degrade the mechanical properties of the solder and reduce the interfacial strength of the solder joint. 【0008】 According to one aspect of this disclosure, sufficient interfacial strength can be ensured at the solder joint even after undergoing high-temperature processes such as reflow bonding. 【0009】 [Embodiment 1] One embodiment of this disclosure will be described in detail below. 【0010】 <Configuration of the device and electronic modules> The configuration of apparatus 200 as an exemplary apparatus relating to this disclosure will be described below. The apparatus relating to this disclosure may be, for example, an electronic apparatus comprising a substrate and electronic components such as electronic elements mounted on the substrate. 【0011】 Figure 1 is a cross-sectional view showing a part of the apparatus 200 according to Embodiment 1 of the present disclosure. Figure 1 is an enlarged cross-sectional view of one electrode 21 portion of the apparatus 200, and electronic components and the like of the apparatus 200 are not shown. 【0012】 The apparatus 200 comprises a substrate 110 and a solder layer 33. The substrate 110 comprises a base body 11, an electrode 21, a barrier layer 31, and a bonding layer 32. The base body 11 has the electrode 21 on its first surface 11a. In the apparatus 200, the barrier layer 31, the bonding layer 32, and the solder layer 33 are layered in this order from the electrode 21 side. In the apparatus 200, the barrier layer 31, the bonding layer 32, and the solder layer 33 are referred to as the bonding portion 30. In other words, the bonding portion 30 is located on the electrode 21. The barrier layer 31, the bonding layer 32, and the solder layer 33 are elements that constitute the bonding portion 30. 【0013】 Figure 2 is a cross-sectional view showing a part of an electronic module 300 comprising the device 200. As shown in Figure 2, the device 200 can constitute the electronic module 300 by being mounted on a mounting substrate (module substrate) 120. The electronic module 300 is an example of an electrical device according to this disclosure. 【0014】 In the electronic module 300, the substrate 110 of the device 200 and the mounting substrate 120 are joined via a solder layer 33. The mounting substrate 120 comprises a base body 12, electrodes 22, a barrier layer 31, and a bonding layer 32. The base body 12 has electrodes 22 on its first surface 12a. The barrier layer 31 is located on the electrodes 22, and the bonding layer 32 is located on the barrier layer 31. The barrier layer 31, bonding layer 32, and solder layer 33 of the electronic module 300 are elements that constitute the joint 30. In other words, the joint 30 is located on the electrodes 22. 【0015】 (substrate, base) The substrate 110 and the mounted substrate 120 are examples of the substrate 100 according to this disclosure. In the following, when referring to aspects common to the substrate 110 and the mounted substrate 120, the substrate 110 and the mounted substrate 120 together may be described as the substrate 100. 【0016】 The substrate 110 is a substrate on which electronic components are mounted, and may include internal wirings located inside the substrate 110 and through conductors that connect the internal wirings vertically to each other. 【0017】 The substrate 11 included in the substrate 110 may be composed of a single layer or a plurality of layers. The substrate 11 has a first surface 11a and a second surface 11b located on the opposite side of the first surface 11a. Electronic components such as electronic elements may be mounted on the first surface 11a or the second surface 11b. 【0018】 The substrate 11 may have insulating properties. In this case, the material of the substrate 11 may be, for example, a ceramic such as an aluminum nitride sintered body, an aluminum oxide sintered body (alumina ceramics), a silicon nitride sintered body, a mullite sintered body, or a glass-ceramic sintered body. Alternatively, examples of the material of the substrate 11 include epoxy resin, polyimide resin, acrylic resin, phenol resin, and fluorine-based resin. As an example of the fluorine-based resin, resins such as polyester resin and tetrafluoroethylene resin may be used. 【0019】 The mounting substrate 120 is a circuit board mounted on an electronic module, and may include an electric circuit inside and / or outside the mounting substrate. 【0020】 (Electrode) The electrodes 21 and 22 are examples of the electrode 20 according to the present disclosure. Regarding the contents common to the electrodes 21 and 22, they may be described as the electrode 20 that collectively refers to the electrodes 21 and 22. 【0021】 The electrode 21 included in the substrate 110 electrically connects the device 200 and the circuit board. The electrode 21 is located on the first surface 11a of the substrate 11. The substrate 110 may include a plurality of electrodes 21 on the first surface 11a. 【0022】 The substrate 110 may have a metallized layer on the surface of the base body 11 in addition to the electrodes 21. This metallized layer may include, for example, a metallized layer provided in a mounting area on the base body 11 where electronic components are mounted, and which can be electrically connected to the electronic components. 【0023】 If the substrate 11 is made of an electrically insulating ceramic, the metallized layer is made of an alloy containing, for example, W (tungsten), Mo (molybdenum), Mn (manganese), Ag (silver), Ni, and Cu, or at least one of these. If the substrate 11 is made of a resin, the metallized layer is made of an alloy containing, for example, Cu, Au (gold), Al (aluminum), Ni, Mo, and Ti (titanium), or at least one of these. The internal wiring and through conductors have a similar composition to the alloy of the metallized layer. 【0024】 The electrodes 22 on the mounting substrate 120 electrically connect the mounting substrate 120 to electronic devices and the like. The electrodes 22 are located on the first surface 12a of the substrate 12. 【0025】 Electrode 20 may be made of an alloy containing Ni (nickel) and Cu (copper). Electrode 21 may contain other metals in addition to Ni and Cu. 【0026】 (Barrier layer) The barrier layer 31 is a layer mainly composed of Mo. The manufacturing process of the apparatus 200 and the electronic module 300 includes a high-temperature soldering process. If the barrier layer 31 and the bonding layer 32 are not present, for example, when flow soldering is performed, molten, high-temperature solder is applied to the electrode 21. When reflow soldering is performed, the apparatus 200 or electronic module 300 with solder applied to the electrode portion is heated in a reflow oven. In addition, due to heat generated by the module during use of the electronic module 300, the solder joint may be repeatedly or continuously exposed to high temperatures. In such cases, electrode metals such as Cu and Ni contained in the electrode 20 dissolve and react with metals such as Sn (tin) and Cu contained in the solder to form a metal compound. Because this metal compound is hard and brittle, it is prone to becoming a crack initiation point. 【0027】 The presence of the barrier layer 31 between the electrode 20 and the solder layer 33 reduces the possibility of reaction between the electrode metal in the electrode 20 and the metal in the solder layer. In other words, it reduces the diffusion of the electrode metal into the solder layer. This reduces the formation of metal compounds. The thickness of the barrier layer 31 may be, for example, 0.1 μm or more. Having a barrier layer 31 with a thickness of 0.1 μm or more significantly reduces the possibility of reaction between the electrode metal and the metal in the solder layer. 【0028】 (Joining layer) The bonding layer 32 is located between the solder layer 33 and the barrier layer 31 and is a layer containing at least one of Ni, Ag, Au, and Cu. The presence of the bonding layer 32 ensures the wettability of the solder, thereby improving the interfacial strength of the solder interface. 【0029】 The bonding layer 32 may mainly contain Ni, Ni-Sn compounds, Cu, or Cu-Sn compounds. Since Ni and Cu have excellent wettability with solder, the interfacial strength can be further improved. 【0030】 In the state of the substrate 100 before soldering, the thickness of the bonding layer 32 may be less than the thickness of the electrode 20. For example, the thickness of the bonding layer 32 may be 0.1 μm or more and 1 μm or less, or it may be 0.1 μm. 【0031】 Under high-temperature conditions such as soldering, the metal contained in the bonding layer 32 may react with the metal contained in the solder to form a metal compound. By setting the thickness of the bonding layer 32 to the aforementioned thickness, the amount of metal leaching from the bonding layer 32 during soldering can be reduced, thereby reducing the amount of metal compound formed. Furthermore, since the amount of metal leaching from a sufficiently thin bonding layer 32 is small, coarse particles of metal compound are less likely to form, making the joint less brittle. In other words, it is possible to achieve a joint 30 with excellent interfacial strength while ensuring solder wettability. 【0032】 (Solder layer) The solder layer 33 is a layer containing metals such as Sn, Ag, and Cu. 【0033】 (Regarding bonding layers in devices or electronic modules) Figure 3 is a micrograph of the joint 30 in the electronic module 300 shown in Figure 2. Figure 4 is a magnified view of region R in Figure 3. The micrographs shown in Figures 3 and 4 are photographs of the electronic module 300 after soldering in a reflow oven. In the apparatus 200 and the electronic module 300, the solder layer 33 melts due to heating during soldering in the manufacturing process. At this time, at least some of the metal in the joint layer 32 reacts with the metal contained in the solder layer 33 to form one or more compounds. Region C in Figure 4 is a region containing a large amount of this compound. This one or more compounds include, for example, Ni-Sn compounds and Cu-Sn compounds. 【0034】 For example, if the bonding layer 32 before soldering is mainly composed of Ni, then region C contains at least one compound from among Ni3Sn4, Ni3Sn2, Ni3Sn, (Cu,Ni)3Sn4, and (Cu,Ni)6Sn5. 【0035】 Based on the above, in the apparatus 200 or electronic module 300, the bonding layer 32 may mainly contain Ni, a Ni-Sn compound, Cu, or a Cu-Sn compound. 【0036】 The bonding layer 32 may be a layer defined between the upper surface of the barrier layer 31 and a surface that is substantially parallel to the upper surface of the barrier layer 31 and located at the top of region C, as shown in Figure 4. Alternatively, it may be a layer defined between the upper surface of the barrier layer 31 and the solder layer-side boundary of region C. In this case, the bonding layer 32 may be a layer with irregularities and may have holes in part of it. 【0037】 As described above, by providing the barrier layer 31 and the bonding layer 32, the substrate 100 can ensure the wettability of the solder during solder bonding while reducing the amount of Sn-containing compounds formed near the interface between the solder layer 33 and the bonding layer 32. As a result, the substrate 100 can provide a device or electronic module that has sufficient interfacial strength at the solder joint portion even after undergoing high-temperature processes such as reflow bonding. 【0038】 Furthermore, since the apparatus 200 and the electronic module 300 have a substrate 100 and a joint 30, sufficient interfacial strength can be ensured at the solder joint even after undergoing high-temperature processes such as reflow bonding. 【0039】 [Embodiment 2] Other embodiments of this disclosure are described below. For convenience of explanation, components having the same function as those described in the above embodiments are denoted by the same reference numerals, and their descriptions are not repeated. 【0040】 Embodiment 2 describes an example where the device 200 is an elastic wave device. Figure 5 is a cross-sectional view of the elastic wave device 210 according to Embodiment 2. 【0041】 The elastic wave device 210 comprises a substrate 130 and a solder layer 33. The substrate 130 comprises a base 13, an electrode layer 23, a barrier layer 31, and a bonding layer 32. The elastic wave device 210 can be mounted on a circuit board (mounted board) of a communication device. 【0042】 The substrate 13 comprises a piezoelectric layer 13A and a support substrate 13B that supports the piezoelectric layer 13A. The piezoelectric layer 13A has a first surface 13a located on the opposite side from the surface that is joined to the support substrate 13B. The electrode layer 23 is provided on the first surface 13a of the piezoelectric layer 13A. In the elastic wave apparatus 210, the barrier layer 31, the bonding layer 32, and the solder layer 33 are layered in this order from the electrode layer 23 side. In the elastic wave apparatus 210, the barrier layer 31, the bonding layer 32, and the solder layer 33 are referred to as the joint 30. That is, the joint 30 is located on the electrode layer 23. The barrier layer 31, the bonding layer 32, and the solder layer 33 are elements that constitute the joint 30. The substrate 13 is not limited to the above configuration. For example, the substrate 13 does not have to include a support substrate 13B. In this case, the piezoelectric layer 13A itself also plays the role of the support substrate 13B. 【0043】 Substrate 13 is an example of substrate 10 according to this disclosure, and substrate 130 is an example of substrate 100 according to this disclosure. 【0044】 The electrode layer 23 includes an IDT (Interdigital Transducer) electrode 231 and a pad portion 232. The pad portion 232 includes a first pad 232A and a second pad 232B. The pad portion 232 in this embodiment is an example of the electrode 20 according to the disclosure. The first pad 232A and the second pad 232B are stacked in this order from the substrate 13 side. In other words, the pad portion 232 may include multiple layers. The first pad 232A may have the same thickness as the IDT electrode 231. The stacked structure of the pad portion 232 can reduce electrical resistance. 【0045】 The IDT electrode 231 is a comb-type electrode that generates elastic waves in an elastic wave apparatus. The IDT electrode 231 consists of a pair of electrodes to which an AC voltage is applied. The IDT electrode 231 is electrically connected to the pad portion 232. 【0046】 The elastic wave apparatus 210 has the characteristic of having fewer joints connected via the joint portion 30 compared to other electronic devices. Therefore, ensuring the interfacial strength at the joint portion 30 is considered more important. Because the elastic wave apparatus 210 has a substrate 130 and a joint portion 30, sufficient interfacial strength can be ensured at the solder joint even after undergoing high-temperature processes such as reflow bonding. 【0047】 In Embodiment 2, a Surface Acoustic Wave (SAW) was described as the elastic wave device, but the invention is not limited to this. For example, a Bulk Acoustic Wave (BAW) may also be used. 【0048】 [Demonstration Test] The following describes demonstration tests that demonstrate the effectiveness of the substrate, apparatus, and electrical apparatus of this disclosure. 【0049】 (Verification Test 1: Comparison using microscopic images) Figure 6 is a micrograph of the joint of an electronic module. Reference numeral 6001 in Figure 6 is a micrograph of the joint 30 in an electronic module 300 according to an embodiment of the present disclosure. Reference numeral 6002 in Figure 6 is a micrograph of the joint of an electronic module as a comparative example. In the comparative example's electronic module, a solder layer is located between the electrodes on the electronic device side and the mounting substrate. In other words, it does not have the barrier layer 31 and bonding layer 32 according to the present disclosure. The heating conditions during solder bonding are the same for both the embodiment and the comparative example. 【0050】 In the comparative example shown by reference numeral 6002 in Figure 6, a region C containing a large amount of compounds formed by the reaction between the electrode metal and the metal contained in the solder layer exists as a coarse granular region near the interface of the joint. In addition, a void P is formed at the interface of the joint because a large amount of the electrode metal has dissolved into the solder layer. 【0051】 On the other hand, in the electronic module 300 according to this disclosure, shown by reference numeral 6001 in Figure 6, the region C located near the interface of the joint 30 remains relatively small. Furthermore, the void P observed in the comparative example was not observed. 【0052】 In other words, it has been demonstrated that by having the barrier layer 31 and bonding layer 32 according to this disclosure, the formation of brittle compounds at the solder joint can be significantly reduced even after high-temperature processes such as reflow bonding. Furthermore, it has been demonstrated that the elution of electrode metal into the solder layer is reduced, thereby reducing the possibility of voids occurring at the interface between the electrode and the joint. 【0053】 From the above, it has been demonstrated that the substrate, apparatus, and electrical apparatus according to this disclosure can ensure sufficient interfacial strength at the solder joints even after undergoing high-temperature processes. 【0054】 (Verification Test 2: Joint Strength Test) Figures 7 to 10 are graphs showing the results of evaluating the bonding strength when the metal used in the barrier layer is changed. The bonding strength evaluation tests were conducted in accordance with the JEDEC JESD22-B117 standard for solder ball shear. 【0055】 In Comparative Example 1, a Ni layer was used as the electrode and a TaN (tantalum nitride) layer as the barrier layer on the substrate, with solder balls placed on top. Figure 7 shows the results of tests performed after one reflow process and after three reflow processes for the configuration of Comparative Example 1. 【0056】 In Comparative Example 2, a Ni layer was used as the electrode and a TiN (titanium nitride) layer as the barrier layer on the substrate, with solder balls placed on top. Figure 8 shows the results for Comparative Example 2. 【0057】 In Comparative Example 3, a Ni layer was used as the electrode and a W (tungsten) layer as the barrier layer on the substrate, with solder balls placed on top. Figure 9 shows the results for Comparative Example 3. 【0058】 In the embodiment, a Ni layer was laminated on a substrate as an electrode, and a Mo (molybdenum) layer, the same as the barrier layer 31 of this disclosure, was laminated as a barrier layer, with solder balls placed on top. Figure 10 shows the results for the embodiment. 【0059】 In Comparative Examples 1 and 2, the graphs show a sharp drop in load at relatively small displacements in both the case of one reflow treatment and the case of three reflow treatments. This indicates that the interfacial strength is weak, and delamination occurs at the solder interface at the displacement where the load drops sharply. 【0060】 In Comparative Example 3, the graph does not show a sharp drop in load within the displacement test range after one reflow treatment. The gradual decrease in load indicates that bulk solder failure, not delamination, is occurring. However, in the results after three reflow treatments, the graph still shows a sharp drop in load at small displacements. This indicates that the interfacial strength weakened with repeated reflow treatments. 【0061】 On the other hand, in the embodiment, the graph did not show a sharp drop in load within the displacement test range in either the case of one reflow treatment or three reflow treatments. In other words, it was demonstrated that the interfacial strength was maintained within the displacement test range. 【0062】 The above test results demonstrate that by using the Mo layer as the barrier layer 31, sufficient interfacial strength can be ensured at the solder joint even after undergoing high-temperature processes such as reflow bonding. 【0063】 (summary) (1) An apparatus according to a first aspect of the present disclosure comprises a substrate having a first surface, an electrode located on the first surface of the substrate and comprising Ni and Cu, and a junction located on the electrode, the junction comprising, in order from the electrode side, a barrier layer, a junction layer, and a solder layer, the barrier layer comprising Mo as the main component, and the junction layer comprising at least one of Ni, Ag, Au, and Cu. 【0064】 (2) In the apparatus of the second aspect of the present disclosure, the thickness of the barrier layer is 0.1 μm or more, in the apparatus of the first aspect. 【0065】 (3) The apparatus of the third aspect of the present disclosure is the apparatus of the first or second aspect, wherein the bonding layer mainly comprises Ni, a Ni-Sn compound, Cu, or a Cu-Sn compound. 【0066】 (4) In the apparatus of the fourth aspect of the present disclosure, in the apparatus of any of the first to third aspects, the electrode is provided on a piezoelectric layer and connected to an IDT electrode. 【0067】 (5) An electrical device of the fifth aspect of the present disclosure comprises any device of the first to fourth aspects of the present disclosure. 【0068】 (6) A substrate according to a sixth aspect of the present disclosure comprises a substrate having a first surface, an electrode located on the first surface of the substrate and containing Ni and Cu, a barrier layer located on the electrode, and a bonding layer located on the barrier layer, wherein the barrier layer mainly contains Mo, and the bonding layer contains at least one of Ni, Ag, Au, and Cu. 【0069】 (7) The substrate of the seventh aspect of the present disclosure is the substrate of the sixth aspect, wherein the thickness of the bonding layer is smaller than the thickness of the electrode. 【0070】 (8) In the substrate of the eighth aspect of the present disclosure, the thickness of the bonding layer is 0.1 μm or more and 1 μm or less in the substrate of the sixth or seventh aspect. 【0071】 The inventions described in this disclosure have been explained above based on the drawings and embodiments. However, the inventions described in this disclosure are not limited to the embodiments described above. That is, the inventions described in this disclosure can be modified in various ways within the scope shown in this disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the inventions described in this disclosure. In other words, it should be noted that it is easy for those skilled in the art to make various modifications or alterations based on this disclosure. Furthermore, it should be noted that these modifications or alterations are included in the scope of this disclosure. [Explanation of Symbols] 【0072】 10, 11, 12, 13...Base 20, 21, 22... electrode 30...junction 31. Barrier layer 32...Joining layer 100, 110, 130... circuit boards 120... Mounted circuit board 200...device 210... Elastic wave apparatus (device) 13A... Piezoelectric layer 13B...Support board 23...electrode layer 231...IDT electrode 232... Pad section (electrode) 300... Electronic Modules (Electrical Devices)

Claims

[Claim 1] A substrate having a first surface, An electrode located on the first surface of the substrate, comprising Ni and Cu, It has a joint portion located on the electrode, The aforementioned joint includes, in order from the electrode side, a barrier layer, a bonding layer, and a solder layer. The barrier layer contains Mo as its main component, The apparatus wherein the bonding layer mainly contains Ni, Ni-Sn compounds, Cu, or Cu-Sn compounds. [Claim 2] The apparatus according to claim 1, wherein the thickness of the barrier layer is 0.1 μm or more. [Claim 3] The apparatus according to claim 1, wherein the electrode is provided on a piezoelectric layer and connected to an IDT electrode. [Claim 4] An electrical device comprising the device described in any one of claims 1 to 3. [Claim 5] A substrate having a first surface, An electrode located on the first surface of the substrate, comprising Ni and Cu, A barrier layer located on the electrode, The barrier layer has a bonding layer located on it, The barrier layer contains Mo as its main component, The bonding layer is a substrate mainly composed of Ni, a Ni-Sn compound, Cu, or a Cu-Sn compound. [Claim 6] The substrate according to claim 5, wherein the thickness of the bonding layer is smaller than the thickness of the electrode. [Claim 7] The substrate according to claim 5 or 6, wherein the thickness of the bonding layer is 0.1 μm or more and 1 μm or less.

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