Device, electrical device, and substrate

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

Devices, electrical devices and substrates

[0001] The present disclosure relates to devices, electrical devices, and substrates.

[0002] Devices carrying electronic components are mounted on mounting boards of electrical devices by soldering.

[0003] For example, the acoustic wave device described in Patent Document 1 includes a pad (electrode) provided on a piezoelectric substrate, and an under-bump metal provided on the pad to facilitate bonding with solder.

[0004] International Publication No. WO2015 / 022931

[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 joint located on the electrode, the joint including, in order from the electrode side, a barrier layer, a joint layer, and a solder layer, the barrier layer containing Mo as a main component, and the joint layer containing at least one of Ni, Ag, Au, and Cu.

[0006] 3 is a cross-sectional structural view of a device according to embodiment 1 of the present disclosure; FIG. 4 is a cross-sectional structural view showing an electronic module according to embodiment 1 of the present disclosure; FIG. 5 is a micrograph of a joint according to embodiment 1 of the present disclosure; FIG. 6 is an enlarged view of region R in FIG. 3; FIG. 7 is a cross-sectional structural view of an elastic wave device according to embodiment 2 of the present disclosure; FIG. 8 is a micrograph of a joint of electronic modules of an example and a comparative example; FIG. 9 is a graph showing the results of evaluation of the joint strength of the comparative example; FIG. 10 is a graph showing the results of evaluation of the joint strength of the comparative example; FIG. 11 is a graph showing the results of evaluation of the joint strength of the example;

[0007] When high-temperature processes such as reflow bonding are repeatedly performed, or when the equipment is used at high temperatures for long periods of time, various metallic materials, including under-bump metal, react with the metals contained in the solder, which can deteriorate the mechanical properties of the solder and reduce the interfacial strength of the solder joint.

[0008] According to one aspect of the present disclosure, sufficient interfacial strength can be ensured at the solder joint even after undergoing high-temperature processes such as reflow bonding.

[0009] First Embodiment Hereinafter, one embodiment of the present disclosure will be described in detail.

[0010] <Configuration of Device and Electronic Module> The following describes the configuration of device 200 as an exemplary device according to the present disclosure. The device according to the present disclosure may be, for example, an electronic device including a substrate and electronic components such as electronic elements mounted on the substrate.

[0011] Fig. 1 is a cross-sectional structural view showing a portion of a device 200 according to a first embodiment of the present disclosure. Fig. 1 is an enlarged cross-sectional structural view of one electrode 21 included in the device 200, and does not show electronic components included in the device 200.

[0012] The device 200 includes a substrate 110 and a solder layer 33. The substrate 110 includes a base 11, an electrode 21, a barrier layer 31, and a bonding layer 32. The base 11 has the electrode 21 on its first surface 11a. In the device 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 device 200, the barrier layer 31, the bonding layer 32, and the solder layer 33 are referred to as a 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 each elements that constitute the bonding portion 30.

[0013] Fig. 2 is a cross-sectional structural view showing a portion of an electronic module 300 including a device 200. As shown in Fig. 2, the device 200 can be mounted on a mounting substrate (module substrate) 120 to form the electronic module 300. The electronic module 300 is an example of an electric device according to the present disclosure.

[0014] In the electronic module 300, the substrate 110 of the device 200 and the mounting substrate 120 are bonded via a solder layer 33. The mounting substrate 120 includes a base 12, an electrode 22, a barrier layer 31, and a bonding layer 32. The base 12 has the electrode 22 on its first surface 12a. The barrier layer 31 is located on the electrode 22, and the bonding layer 32 is located on the barrier layer 31. The barrier layer 31, the bonding layer 32, and the solder layer 33 included in the electronic module 300 are each elements that constitute a bonding portion 30. In other words, the bonding portion 30 is located on the electrode 22.

[0015] (Substrate, base) The substrate 110 and the mounting substrate 120 are examples of the substrate 100 according to the present disclosure. In the following, content common to the substrate 110 and the mounting substrate 120 may be described as the substrate 100, which is a general term for the substrate 110 and the mounting substrate 120.

[0016] The substrate 110 is a substrate on which electronic components are mounted, and may include internal wiring located inside the substrate 110 and through conductors that vertically connect the internal wirings to each other.

[0017] The substrate 110 has a base 11 that may be composed of a single layer or multiple layers. The base 11 has a first surface 11a and a second surface 11b located on the opposite side of the first surface 11a. An electronic component such as an electronic element may be mounted on either the first surface 11a or the second surface 11b.

[0018] The base 11 may have insulating properties. In this case, the material of the base 11 may be 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, the material of the base 11 may be epoxy resin, polyimide resin, acrylic resin, phenolic resin, or fluorine-based resin. Examples of the fluorine-based resin include polyester resin and tetrafluoroethylene resin.

[0019] The mounting board 120 is a circuit board mounted on an electronic module, and may include electrical circuits inside and / or outside the mounting board.

[0020] (Electrode) The electrodes 21 and 22 are examples of the electrode 20 according to the present disclosure. Regarding content common to the electrodes 21 and 22, the electrodes 21 and 22 may be described as the electrode 20, which is a general term for the electrodes 21 and 22.

[0021] The electrode 21 of the substrate 110 electrically connects the device 200 to the circuit board. The electrode 21 is located on the first surface 11a of the base 11. The substrate 110 may have 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 11 in addition to the electrodes 21. The metallized layer includes, for example, a metallized layer that is provided in a mounting region of the base 11 where an electronic component is mounted and that can be electrically connected to the electronic component.

[0023] When the base 11 is made of an electrically insulating ceramic, the metallization layer is made of, for example, any one of W (tungsten), Mo (molybdenum), Mn (manganese), Ag (silver), Ni, and Cu, or an alloy containing at least one of these. When the base 11 is made of a resin, the metallization layer is made of, for example, any one of Cu, Au (gold), Al (aluminum), Ni, Mo, and Ti (titanium), or an alloy containing at least one of these. The internal wiring and through conductors also have the same composition as the alloy of the metallization layer.

[0024] The electrodes 22 of the mounting substrate 120 electrically connect the mounting substrate 120 to an electronic device, etc. The electrodes 22 are located on the first surface 12 a of the base 12 .

[0025] The electrode 20 may be made of an alloy containing Ni (nickel) and Cu (copper). The electrode 21 may contain metals other than Ni and Cu.

[0026] (Barrier Layer) The barrier layer 31 is a layer containing Mo as a primary component. The manufacturing process of the device 200 and the electronic module 300 includes a soldering process, which is a high-temperature process. Without the barrier layer 31 and the bonding layer 32, for example, flow soldering is performed, in which molten, high-temperature solder is applied to the electrodes 21. When reflow soldering is performed, the device 200 or the electronic module 300, with solder applied to the electrodes, is heated in a reflow furnace. Furthermore, during use of the electronic module 300, the soldered joints may be repeatedly or continuously exposed to high temperatures due to heat generation from the module. In such cases, electrode metals such as Cu and Ni contained in the electrodes 20 melt and react with metals such as Sn (tin) and Cu contained in the solder, forming metal compounds. Because these metal compounds are hard and brittle, they are prone to becoming the starting point for cracks.

[0027] The barrier layer 31 located between the electrode 20 and the solder layer 33 can reduce the possibility of a reaction between the electrode metal contained in the electrode 20 and the metal contained in the solder layer. In other words, the diffusion of the electrode metal into the solder layer can be reduced. This can reduce the formation of metal compounds. The thickness of the barrier layer 31 may be, for example, 0.1 μm or more. By making the barrier layer 31 have a thickness of 0.1 μm or more, the possibility of a reaction between the electrode metal and the metal of the solder layer can be significantly reduced.

[0028] (Bonding Layer) The bonding layer 32 is a layer that is located between the solder layer 33 and the barrier layer 31 and contains 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 contain Ni, a Ni—Sn compound, Cu, or a Cu—Sn compound as a main component. Ni and Cu have excellent wettability with solder, which can further improve the interfacial strength.

[0030] In the state of the substrate 100 before solder bonding, the thickness of the bonding layer 32 may be smaller 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 may be 0.1 μm.

[0031] Under high-temperature conditions, such as during soldering, the metal contained in the bonding layer 32 may react with the metal contained in the solder, forming a metal compound. By setting the thickness of the bonding layer 32 to the above-described thickness, the amount of metal eluted from the bonding layer 32 during soldering or other processes can be reduced, thereby reducing the amount of metal compounds formed. Furthermore, because the amount of metal eluted from a sufficiently thin bonding layer 32 is small, coarse particles of metal compounds are less likely to form, making the layer less brittle. In other words, a bonded portion 30 with excellent interfacial strength can be achieved while maintaining the wettability of the solder.

[0032] (Solder Layer) The solder layer 33 is a layer containing a metal such as Sn, Ag, or Cu.

[0033] (Regarding the bonding layer in the device or electronic module) FIG. 3 is a micrograph of the bonding portion 30 in the electronic module 300 shown in FIG. 2. FIG. 4 is an enlarged view of region R in FIG. 3. The micrographs shown in FIGS. 3 and 4 are of the electronic module 300 after solder bonding has been performed in a reflow furnace. In the device 200 and the electronic module 300, the solder layer 33 melts due to heating during solder bonding in the manufacturing process. At this time, at least a portion of the metal in the bonding layer 32 reacts with the metal contained in the solder layer 33 to form one or more compounds. Region C in FIG. 4 is a region containing a large amount of the compound. The one or more compounds include, for example, a Ni—Sn compound and a Cu—Sn compound.

[0034] For example, when the bonding layer 32 before solder bonding is mainly composed of Ni, the region C contains Ni. ３ Sn ４ , Ni ３ Sn ２ , Ni ３ Sn, (Cu, Ni) ３ Sn ４ , and (Cu, Ni) ６ Sn５ At least one compound among these is included.

[0035] In view of the above, in the device 200 or the electronic module 300, the bonding layer 32 may contain Ni, a Ni--Sn compound, Cu, or a Cu--Sn compound as a main component.

[0036] 4, the bonding layer 32 may be a layer defined between the upper surface of the barrier layer 31 and a surface that is approximately parallel to the upper surface of the barrier layer 31 and is located at the top of the region C. Alternatively, the bonding layer 32 may be a layer defined between the upper surface of the barrier layer 31 and the boundary of the region C on the solder layer side. In this case, the bonding layer 32 may be a layer having irregularities, and may have holes in some parts thereof.

[0037] As described above, by including 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 soldered joints, even after undergoing high-temperature processes such as reflow bonding.

[0038] Furthermore, since the device 200 and the electronic module 300 have the substrate 100 and the 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] Another embodiment of the present disclosure will be described below. For convenience of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0040] In the second embodiment, an example will be described in which the device 200 is an acoustic wave device. Fig. 5 is a cross-sectional structural view of an acoustic wave device 210 in accordance with the second embodiment.

[0041] The acoustic wave device 210 includes a substrate 130 and a solder layer 33. The substrate 130 includes a base 13, an electrode layer 23, a barrier layer 31, and a bonding layer 32. The acoustic wave device 210 can be mounted on a circuit board (mounting board) of a communication device.

[0042] The base 13 includes 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 side opposite to the surface bonded to the support substrate 13B. The electrode layer 23 is provided on the first surface 13a of the piezoelectric layer 13A. In the acoustic wave device 210, a barrier layer 31, a bonding layer 32, and a solder layer 33 are layered in this order from the electrode layer 23 side. In the acoustic wave device 210, the barrier layer 31, the bonding layer 32, and the solder layer 33 are referred to as a bonding portion 30. In other words, the bonding portion 30 is located on the electrode layer 23. The barrier layer 31, the bonding layer 32, and the solder layer 33 are each elements that constitute the bonding portion 30. The base 13 is not limited to the above configuration. For example, the base 13 does not need to include the support substrate 13B. In this case, the piezoelectric layer 13A itself also serves as the support substrate 13B.

[0043] The base 13 is an example of the base 10 according to the present disclosure, and the substrate 130 is an example of the substrate 100 according to the present 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 present disclosure. The first pad 232A and the second pad 232B are laminated in this order from the base 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 pad portion 232 has a laminated structure, which can reduce electrical resistance.

[0045] The IDT electrode 231 is a comb-shaped electrode that generates an acoustic wave in the acoustic wave device. The IDT electrode 231 is composed of a pair of electrodes to which an AC voltage is applied. The IDT electrode 231 is electrically connected to a pad portion 232.

[0046] Compared to other electronic devices, acoustic wave device 210 has a feature of having fewer joints that are bonded via joints 30. Therefore, it is more important to ensure the interfacial strength of joints 30. Because acoustic wave device 210 has substrate 130 and joints 30, sufficient interfacial strength can be ensured at the solder joints even after high-temperature processes such as reflow bonding.

[0047] In the second embodiment, the acoustic wave device is described as being a surface acoustic wave (SAW) device, but is not limited to this. For example, the acoustic wave device may be a bulk acoustic wave (BAW) device.

[0048] [Demonstration Test] Below, a demonstration test that demonstrates the effects of the substrate, device, and electrical device of the present disclosure will be described.

[0049] (Demonstration Test 1: Comparison by Micrograph) FIG. 6 is a micrograph of a joint of an electronic module. Reference numeral 6001 in FIG. 6 is a micrograph of a joint 30 in an electronic module 300 according to an example of the present disclosure. Reference numeral 6002 in FIG. 6 is a micrograph of a joint of an electronic module as a comparative example. In the electronic module of the comparative example, a solder layer is located between the electrode 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 example and the comparative example.

[0050] 6, a comparative example indicated by reference numeral 6002 has a region C near the interface of the joint that contains a large amount of compounds formed by the reaction between the electrode metal and the metal contained in the solder layer, and this region C is a coarse granular region. In addition, a large amount of the electrode metal has eluted toward the solder layer, forming a void P at the interface of the joint.

[0051] 6, the area C near the interface of the joint 30 is relatively small. Also, the void P observed in the comparative example was not observed.

[0052] In other words, it was demonstrated that the inclusion of the barrier layer 31 and bonding layer 32 according to the present disclosure significantly reduces the formation of brittle compounds in the solder joint, even after high-temperature processes such as reflow bonding. It was also demonstrated that the reduction in elution of the electrode metal into the solder layer reduces 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, device, and electrical device according to the present disclosure can ensure sufficient interfacial strength at the solder joints even after undergoing high-temperature processes.

[0054] 7 to 10 are graphs showing the results of evaluating the bond strength when the metal used in the barrier layer is changed. The bond strength evaluation test was conducted in accordance with the solder ball shear standard of JEDEC JESD22-B117.

[0055] In Comparative Example 1, a Ni layer was laminated on a substrate as an electrode, a TaN (tantalum nitride) layer was laminated as a barrier layer, and a solder ball was placed on top of that. Figure 7 shows the results of tests conducted on the configuration of Comparative Example 1 after performing a reflow treatment once and after performing a reflow treatment three times.

[0056] In Comparative Example 2, a Ni layer was laminated on a substrate as an electrode, a TiN (titanium nitride) layer was laminated on a substrate as a barrier layer, and a solder ball was placed thereon. Figure 8 shows the results for Comparative Example 2.

[0057] In Comparative Example 3, a Ni layer was laminated as an electrode on a substrate, a W (tungsten) layer was laminated as a barrier layer, and a solder ball was placed thereon. Figure 9 shows the results for Comparative Example 3.

[0058] In the example, a Ni layer was laminated on a substrate as an electrode, and a Mo (molybdenum) layer, which is the same as the barrier layer 31 of the present disclosure, was laminated as a barrier layer, and a solder ball was placed thereon. Figure 10 shows the results of the example.

[0059] In Comparative Examples 1 and 2, the graphs show a sudden drop in load at a relatively small displacement in both the cases of one reflow treatment and three reflow treatments. This indicates that the interfacial strength is weak, and peeling occurs at the solder interface at the displacement where the load drops suddenly.

[0060] In Comparative Example 3, when the reflow process was performed once, the load did not drop sharply within the test range of displacement. The gradual drop in load indicates that bulk failure of the solder occurred, rather than peeling. However, when the reflow process was performed three times, the load also dropped sharply at small displacements. This indicates that the interfacial strength was weakened by repeated reflow processes.

[0061] On the other hand, in the examples, the load did not drop suddenly within the test range of displacement in either the case of one reflow treatment or three reflow treatments, demonstrating that the interfacial strength was maintained within the test range of displacement.

[0062] The above test results demonstrate that by using a Mo layer as the barrier layer 31, sufficient interfacial strength can be ensured at the solder joint even after high-temperature processes such as reflow bonding.

[0063] (Summary) (1) The device of the first aspect of the present disclosure has a substrate having a first surface, an electrode located on the first surface of the substrate and containing Ni and Cu, and a joint located on the electrode, the joint including, in order from the electrode side, a barrier layer, a joint layer, and a solder layer, the barrier layer containing Mo as a main component, and the joint layer containing at least one of Ni, Ag, Au, and Cu.

[0064] (2) A second aspect of the present disclosure is directed to the device of the first aspect, wherein the barrier layer has a thickness of 0.1 μm or more.

[0065] (3) A third aspect of the present disclosure is directed to the device of the first or second aspect, wherein the bonding layer contains Ni, a Ni—Sn compound, Cu, or a Cu—Sn compound as a main component.

[0066] (4) A fourth aspect of the present disclosure provides a device according to any one of the first to third aspects, wherein the electrode is provided on the piezoelectric layer and connected to an IDT electrode.

[0067] (5) An electrical device according to a fifth aspect of the present disclosure includes the device according to any one of the first to fourth aspects of the present disclosure.

[0068] (6) A substrate according to a sixth aspect of the present disclosure includes a base having a first surface, an electrode located on the first surface of the base 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 contains Mo as a main component, and the bonding layer contains at least one of Ni, Ag, Au, and Cu.

[0069] (7) A seventh aspect of the present disclosure provides a substrate according to the sixth aspect, wherein the thickness of the bonding layer is smaller than the thickness of the electrode.

[0070] (8) In an eighth aspect of the present disclosure, in the substrate of the sixth or seventh aspect, the thickness of the bonding layer is 0.1 μm or more and 1 μm or less.

[0071] The invention according to the present disclosure has been described above based on the drawings and examples. However, the invention according to the present disclosure is not limited to the above-described embodiments. In other words, the invention according to the present disclosure can be modified in various ways within the scope of the present disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the invention according to the present disclosure. In other words, it should be noted that a person skilled in the art can easily make various modifications or corrections based on the present disclosure. It should also be noted that these modifications or corrections are included in the scope of the present disclosure.

[0072] DESCRIPTION OF SYMBOLS 10, 11, 12, 13... Base body 20, 21, 22... Electrode 30... Bonding portion 31... Barrier layer 32... Bonding layer 100, 110, 130... Substrate 120... Mounting substrate 200... Device 210... Acoustic wave device (device) 13A... Piezoelectric layer 13B... Support substrate 23... Electrode layer 231... IDT electrode 232... Pad portion (electrode) 300... Electronic module (electrical device)

Claims

1. A substrate having a first surface, an electrode located on the first surface of the substrate and containing Ni and Cu, and a joint portion located on the electrode, wherein the joint portion includes a barrier layer, a joint layer, and a solder layer in this order from the electrode side, the barrier layer contains Mo as a main component, and the joint layer contains at least one of Ni, Ag, Au, and Cu. A device.

2. The device according to claim 1, wherein the thickness of the barrier layer is 0.1 μm or more.

3. The device according to claim 1, wherein the joint layer contains Ni, a Ni—Sn compound, Cu, or a Cu—Sn compound as a main component.

4. The device according to claim 1, wherein the electrode is provided on a piezoelectric layer and is connected to an IDT electrode.

5. An electrical device comprising the device according to any one of claims 1 to 4.

6. 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 joint layer located on the barrier layer, wherein the barrier layer contains Mo as a main component, and the joint layer contains at least one of Ni, Ag, Au, and Cu. A substrate.

7. The substrate according to claim 6, wherein the thickness of the joint layer is smaller than the thickness of the electrode.

8. The substrate according to claim 6 or 7, wherein the thickness of the joint layer is 0.1 μm or more and 1 μm or less.