Piezoelectric devices and packages

Abstract

To ensure the bonding strength of IC chips and improve the durability and reliability of piezoelectric devices. [Solution] A piezoelectric device comprising a rectangular base in plan view, a piezoelectric vibrator mounted in the inner region of the base, and an IC chip mounted on the base by welding with an ultrasonic horn, wherein the base has a plurality of mounting portions on its bottom surface, including mounting pads corresponding to the terminals of the IC chip, and the height from the surface opposite to the bottom surface on which the plurality of mounting portions are provided to the top surface of each of the plurality of mounting portions is higher in the center of the vibration direction of the ultrasonic horn than at both ends of the vibration direction.

Description

Technical Field

[0001] The present disclosure relates to a piezoelectric device, a piezoelectric vibrating piece, and a package on which an IC chip is mounted.

Background Art

[0002] In various electronic devices such as mobile phones and personal computers, in order to easily obtain a stable frequency required for information processing or communication processing, etc., it is known to use a crystal oscillator that combines a crystal resonator and an integrated circuit (IC) chip. As the IC chip mounted on the crystal oscillator, there are those for wire bonding (W / B) that connect the electrode terminals of the IC chip and the electrode terminals of the package via wires, and those for flip chip bonding (FCB) in which the electrode terminals of the IC chip are mounted on the electrode terminals of the package via bumps.

[0003] For example, Patent Document 1 discloses a piezoelectric oscillator in which an IC chip is mounted by FCB. In the piezoelectric oscillator, a semiconductor element (IC chip) is joined to a ceramic package by load and ultrasonic waves.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, in a crystal oscillator (piezoelectric oscillator), the means of joining the IC chip and package using ultrasound involves pressing an ultrasonic horn provided in the ultrasonic bonding device against the IC chip and applying ultrasonic vibrations, thereby generating frictional heat between the electrode terminals and bumps. This frictional heat then melts the bumps, thereby joining the IC chip and package.

[0006] However, because the ultrasonic horn vibrates like a pendulum rather than horizontally, the outward-facing parts are vibrated more strongly than the center. As a result, ultrasonic vibrations are transmitted more strongly to the ends located on the outside of the vibration direction than to the center of the IC chip, and consequently, the bonding strength of the central part of the IC chip is lower than that of the parts located on the ends.

[0007] Furthermore, in ultrasonic bonding devices, if the suction nozzle that holds the IC chip is integrated with the ultrasonic horn, the load applied to the central part of the IC chip, which is the part that is held by the suction nozzle, will be smaller than the load applied to both ends of the IC chip. As a result, the bonding strength of the central part of the IC chip will be even lower than that of the parts located at both ends.

[0008] As described above, if the bonding strength in the central part of the IC chip is low, it becomes difficult to ensure uniform bonding strength throughout the entire IC chip, which may lead to a decrease in the durability and reliability of the crystal oscillator.

[0009] This disclosure has been made in view of these challenges, and its purpose is to provide a piezoelectric device and package that can improve the durability and reliability of the piezoelectric device by ensuring the bonding strength of the IC chip. [Means for solving the problem]

[0010] According to one aspect of the present disclosure, a piezoelectric device is provided, comprising a rectangular base in plan view, a piezoelectric vibrator mounted in the inner region of the base, and an IC chip mounted on the base by welding with an ultrasonic horn, wherein the base has a plurality of mounting portions on its bottom surface, including mounting pads corresponding to the terminals of the IC chip, and the height from the surface opposite to the bottom surface on which the plurality of mounting portions are provided to the upper surface of each of the plurality of mounting portions is higher in the center of the vibration direction of the ultrasonic horn than at both ends of the vibration direction.

[0011] According to one aspect of the present disclosure, "a package on which an IC chip is mounted by welding with an ultrasonic horn is provided, comprising a rectangular base in plan view, and a plurality of mounting portions provided on the bottom surface of the base and having mounting pads corresponding to the terminals of the IC chip, wherein the height from the surface opposite to the bottom surface on which the plurality of mounting portions are provided to the top surface of each of the plurality of mounting portions is higher in the center of the vibration direction of the ultrasonic horn than at both ends in the vibration direction of the ultrasonic horn." [Effects of the Invention]

[0012] According to this disclosure, it is possible to provide a piezoelectric device and package that can improve the durability and reliability of the piezoelectric device by ensuring the bonding strength of the IC chip.

[0013] The effects described above are merely illustrative for the sake of explanation, and the effects relating to this disclosure are not limited to those described above. In addition to the effects described above, any other effects described herein may be achieved. [Brief explanation of the drawing]

[0014] [Figure 1] This is a perspective view of a crystal oscillator according to the first embodiment. [Figure 2] Figure 2(a) is an end view along the dashed line AA in Figure 1, and Figure 2(b) is a top view of the crystal oscillator package according to the first embodiment. [Figure 3] This is an enlarged view of region A in Figure 2, and is a schematic diagram showing the bonding process of the IC chip according to the first embodiment. [Figure 4] This is a top view of the package of a crystal oscillator according to a modified example of the first embodiment. [Figure 5] This is a schematic diagram showing the bonding process of an IC chip according to a modified example of the first embodiment, similar to Figure 3. [Figure 6] This is an end view of a crystal oscillator according to the second embodiment, similar to Figure 2. [Modes for carrying out the invention]

[0015] The following description will detail a crystal oscillator, an example of a piezoelectric oscillator according to this disclosure, and the package used therein, with reference to the drawings. Note that this disclosure is not limited to the content described below, and can be modified and implemented as such without altering its essence. Furthermore, the drawings used in each embodiment and its modified form are schematic representations of the crystal oscillator and package according to this disclosure, and may include partial emphasis, enlargement, reduction, or omission to enhance understanding, and may not accurately represent the scale or shape of each component. Additionally, some numerical values ​​used in each embodiment and its modified form are examples only and can be changed as needed. Common components in the drawings are denoted by the same reference numerals.

[0016] (First Embodiment) First, the basic structure of the crystal oscillator according to this disclosure will be described with reference to Figures 1 and 2. Figure 1 is a perspective view of the crystal oscillator according to this embodiment. Figure 2(a) is an end view along the dashed line AA in Figure 1, and is in particular an end view of the long side of the crystal resonator. Figure 2(b) is a top view of the package of the crystal oscillator according to this embodiment.

[0017] As can be seen from FIGS. 1 and FIGS. 2(a) and (b), a crystal oscillator 1, which is an example of a piezoelectric device, includes a package 2, a crystal vibrating piece 3 and an IC chip 4 mounted in a concave mounting space 2a formed in the inner region of the package 2, and a metal cover (lid) 5 for sealing the mounting space 2a. The crystal oscillator 1 is an electronic component in which the crystal vibrating piece 3 and the IC chip 4 are packaged together, and can generate a stable frequency and generate a regular reference signal. That is, the crystal oscillator 1 includes a crystal resonator as an oscillation element.

[0018] In addition, as the oscillation element, in addition to the crystal resonator, for example, a surface acoustic wave (SAW) resonator, other piezoelectric oscillators, micro electro mechanical systems (MEMS) oscillators, etc. may also be used. In other words, the piezoelectric oscillator is not limited to the crystal resonator as in this embodiment, and may be an oscillator including other members (piezoelectric vibrating pieces such as ceramics and silicon) having resonance characteristics, or a MEMS oscillator, etc. Further, regarding the crystal vibrating piece 3, the type of cutting from the crystal raw material is not limited to the AT cut, and may be by other cuts such as the Z cut or the SC cut, which are two-rotation cuts.

[0019] The package 2 is a ceramic package in which a plurality of ceramics with a desired metal pattern formed on the surface are laminated. Specifically, the package 2 has a laminated structure in which a first frame wall 11 having an opening of a predetermined dimension, a second frame wall 12 having an opening smaller than the first frame wall 11, and a rectangular base 13 are laminated. With such a structure, the package 2 forms a concave and stepped mounting space 2a for mounting the crystal vibrating piece 3 and the IC chip 4. Further, the shape of the package 2 is a rectangular parallelepiped shape and is rectangular in a top view. In the following, the thickness direction of the crystal oscillator 1 and the package 2 is defined as the vertical direction, and the direction orthogonal to the vertical direction is defined as the horizontal direction. Also, regarding the horizontal direction, it may be distinguished as the longitudinal direction (the direction of the long side) and the short side direction (the direction of the short side) of the crystal oscillator 1 and the package 2.

[0020] On the upper surface (the upper surface in the vertical direction) of the first frame wall 11, a conductor pattern 15 for sealing is formed. The planar shape of the conductor pattern 15 is a frame shape similar to that of the first frame wall 11. And a cover 5 is joined to the conductor pattern 15 by a known metal joining method. Thereby, the mounting space 2a of the package is sealed, and the mounting space 2a is sealed using a gas such as vacuum or nitrogen.

[0021] On the upper surface 12a of the second frame wall 12, two rectangular crystal oscillator mounting terminals 16, 17 (only the crystal oscillator mounting terminal 16 is shown in Fig. 2(a)) are formed. And a crystal oscillator 3 is mounted on the crystal oscillator mounting terminals 16, 17 via a conductive adhesive 18.

[0022] On the lower surface 13a of the base 13, four external connection terminals 20a, 20b, 20c, 20d are formed. Each of these external connection terminals is connected to either six mounting pads 21a, 21b, 21c, 21d, 21e, 21f (only the mounting pads 21a - 21c are shown in Fig. 2(a)) as IC chip mounting terminals provided on the upper surface 13b of the base 13 via connection wirings (not shown) provided inside the package 2, or to the crystal oscillator mounting terminals 16, 17 provided on the upper surface 12a of the second frame wall 12.

[0023] An IC chip 4 is mounted on each of the mounting pads via bumps 31 made of gold or the like. That is, in the crystal oscillator 1, a flip - chip type IC chip 4 is mounted by flip - chip bonding. The IC chip has a rectangular shape in top view and has six IC terminals 41, and each of the IC terminals 41 is electrically connected to the corresponding mounting pads 21a - 21f via the bumps 31.

[0024] Here, a base-raising member 51 is formed on the lower surface of the mounting pads 21b and 21e, which correspond to the IC terminal 41 located in the center of the IC chip 4. The base-raising member 51 is a member for raising the position of the mounting pads and is made of molybdenum or ceramic. As a result of providing the base-raising member 51, the position of the mounting pads 21b and 21e is higher than the position of the other mounting pads 21a, 21c, 21d, and 21f.

[0025] As described above, by providing a base-raising member 51 on the underside of the mounting pads 21b and 21e corresponding to the IC terminal 41 located in the center of the IC chip 4, the position of the mounting pads 21b and 21e is raised, and the bonding strength in the center of the IC chip 4 by ultrasonic bonding can be ensured. Details will be described later. In the following, the mounting pads 21a to 21f (and the base-raising member 51 if provided) for mounting the IC chip 4 on the base 13 of the package 2 will also be referred to as the mounting section.

[0026] Next, with reference to Figure 3, the ultrasonic bonding process between the base 13 of package 2 and the IC chip 4 will be described. Figure 3 is an enlarged view of area A in Figure 2(a), and is a schematic diagram showing the bonding process of the IC chip 4 according to this embodiment.

[0027] First, as shown in the upper diagram of Figure 3, bumps 31 are applied to the IC terminals 41 of the IC chip 4. Also, mounting pads 21a to 21f (only mounting pads 21a to 21c are shown in Figure 3) are formed on the upper surface 13b of the base 13, and in addition, a base support member 51 is formed on the lower surface of mounting pads 21b and 21e. Then, the lower surface 4b of the IC chip 4 and the upper surface 13b of the base 13 are placed facing each other.

[0028] Here, the thickness of the base support member 51 is preferably equal to or greater than the thickness of the mounting pads 21b and 21e, and is preferably set considering the melting of the bumps 31, which will be described later. For example, if the thickness of the mounting pads 21b and 21e is 2 μm, the thickness of the base support member is preferably 4 μm. Also, the thickness of the joint portion after melting of the bumps 31 (between the lower surface 4b of the IC chip 4 and the upper surface 13b of the base 13) is preferably 10 μm or more. Furthermore, the area and shape of the base support member 51 in top view are not particularly limited, but from the viewpoint of reducing the risk of damage to the mounting pads 21b and 21e and suppressing the spreading due to the melting of the bumps 31, it is preferable that they be the same as the mounting pads 21b and 21e.

[0029] Next, as shown in the middle diagram of Figure 3, the ultrasonic horn 60 for ultrasonic bonding is pressed against the upper surface 4a of the IC chip 4, and ultrasonic vibrations are applied to the bump 31. At this time, frictional heat is generated between the IC terminals 41 and the bump 31, and between the bump 31 and the mounting pads 21a to 21f, causing the bump 31 to melt, and the pressure from the ultrasonic horn 60 causes the bump 31 to spread outwards.

[0030] Here, as a premise, the tip of the ultrasonic horn 60 vibrates in a pendulum-like trajectory, so the outward side of the vibration direction is shaken more than the center. Therefore, the magnitude P of the ultrasonic vibration transmitted from the ultrasonic horn 60 is not uniform, and the magnitude P of the ultrasonic vibration transmitted is greater at the bumps 31 located at both ends than at the bump 31 located at the center of the IC chip 4. As a result, the bump 31 located at the center of the IC chip 4 tends to melt less than the bumps 31 located at both ends.

[0031] Furthermore, although not shown in Figure 3, if the ultrasonic horn 60 is equipped with a mechanism for attracting and holding the IC chip 4, this mechanism is often located in the center of the ultrasonic horn 60. As a result, the load applied to the central part of the IC chip 4 by the ultrasonic horn 60 is likely to be smaller than that applied to both ends of the IC chip 4.

[0032] Therefore, the height of the mounting portion at the center of the vibration direction of the ultrasonic horn 60 (the center of the IC chip 4) is increased. In other words, in this embodiment, the height of the mounting portion is adjusted to correspond to the mounting area of ​​the IC chip 4, so that the height of the mounting portion facing the center of the IC chip 4 is higher than the height of the mounting portions facing both ends of the IC chip 4. Here, the mounting area is the area where the IC chip 4 is actually mounted. As a result, as shown in the lower part of Figure 3, when the bumps 31 melt and weld to the IC terminals 41 and mounting pads 21a to 21f to join the IC chip 4 and the base 13, the degree of melting of the bumps 31 corresponding to the mounting pads 21b and 21e is made sufficiently large, and the load applied by the pressing of the ultrasonic horn 60 can also be made sufficient. As a result, the bonding strength between the center of the IC chip 4 and the base 13 can be ensured, the risk of connection failure or damage to the IC chip 4 can be suppressed, and the durability and reliability of the crystal oscillator 1 can be improved.

[0033] Furthermore, the bottom-raising member 51 does not necessarily need to be laminated on the base 13 as a separate member, but may be formed integrally with the base 13 of the package 2. Specifically, a protrusion may be formed as the upper surface 13b of the base 13 during the molding of the package 2. In such a case, the protrusion will serve the role of the bottom-raising member 51, making the bottom-raising member 51 unnecessary.

[0034] Furthermore, in this embodiment, the following steps are taken as a method for manufacturing the crystal oscillator 1. First, a package 2 is prepared, which has a rectangular base 13 in plan view and a plurality of mounting sections provided on the bottom surface 13b of the base 13 and equipped with mounting pads 21a to 21f corresponding to the terminals 41 of the IC chip 4, wherein the height from the surface opposite to the bottom surface (i.e., the top surface 13b of the base) where the plurality of mounting sections are provided (i.e., the bottom surface 13a of the base) to the top surface of each of the plurality of mounting sections is higher in the center of the vibration direction of the ultrasonic horn 60 than at both ends of the vibration direction (preparation step). Next, the IC chip 4 is placed on the mounting pads 21a to 21f, and the IC chip 4 is pressed by the ultrasonic horn 60 and mounted by welding with ultrasonic vibration (IC chip mounting step). Next, the crystal vibrator 3 is mounted on the crystal vibrator mounting terminals 16, 17 (piezoelectric vibrator mounting step). Finally, the package 2 is sealed with a cover 5 (sealing step).

[0035] This completes the crystal oscillator 1 according to this embodiment. Because the package 2 has the structure described above, the load and ultrasonic vibrations applied by the ultrasonic horn 60 during the IC chip mounting process can be sufficiently transmitted. As a result, the bonding strength between the central part of the IC chip 4 and the base 13 can be ensured, the risk of connection failure or damage to the IC chip 4 can be suppressed, and the durability and reliability of the crystal oscillator 1 can be improved.

[0036] (Modification of the first embodiment) In the first embodiment, there were six mounting pads, and two of the central mounting pads were provided with raised base members. However, the number of mounting pads and raised base members is not limited to these. For example, the number of mounting pads may be greater than six, and the number of raised base members may be greater than two. Furthermore, the height of multiple mounting sections may be set to increase in stages from both ends towards the center. Such cases will be described as modifications of the first embodiment with reference to Figures 4 and 5. Here, Figure 4 is a top view of the crystal oscillator package according to a modification of the first embodiment. Figure 5 is a schematic diagram showing the bonding flow of the IC chip according to a modification of the first embodiment, similar to Figure 3. Note that components identical to those in the first embodiment are denoted by the same reference numerals, and their descriptions are simplified or omitted.

[0037] As shown in the upper diagram of Figure 5, the modified IC chip 104 is provided with 10 IC terminals 141, each coated with a bump 131. Also, as shown in Figure 4, mounting pads 121a to 121j (only mounting pads 121a to 121e are shown in Figure 5) are formed on the upper surface 113b of the base 113, and in addition, a base support member 151 is formed on the lower surface of mounting pads 121b to 121d and 121g to 121i. Here, the thickness of the base support member 151 corresponding to mounting pad 121c is greater than the thickness of the base support member 151 corresponding to mounting pads 121b and 121d. In other words, the height of the mounting portion provided on the upper surface 113b of the base 113 increases in stages from those located at both ends to those located in the center.

[0038] Next, as shown in the middle diagram of Figure 5, the ultrasonic horn 60 is pressed against the upper surface 4a of the IC chip 4, and ultrasonic vibrations are applied to the bump 131. The pressure from the ultrasonic horn 60 causes the bump 131 to spread outwards.

[0039] Then, as shown in the lower diagram of Figure 5, the IC chip 104 and the base 113 are joined together. Here, the height of the mounting section increases in stages from those located at both ends to those located in the center, making it possible to perform joining while taking into account the non-uniformity of the load applied by the ultrasonic horn 60 and the magnitude P of the ultrasonic vibration. As a result, uniformity of the joining strength between the IC chip 104 and the base 113 can be ensured, the risk of connection failure or damage to the IC chip 104 can be suppressed, and the durability and reliability of the crystal oscillator 101 can be improved.

[0040] In this modified example, the bottom-raising member 151 does not necessarily need to be laminated on the base 113 as a separate member, but may be formed integrally with the base 113 of the package 102. Specifically, a protrusion may be formed as the upper surface 113b of the base 113 during the molding of the package 102. In such a case, the protrusion will serve the role of the bottom-raising member 151, making the bottom-raising member 151 unnecessary.

[0041] (Second Embodiment) In the first embodiment, the crystal oscillator 3 and the IC chip 4 were mounted in the mounting space 2a of the package 2, but the crystal oscillator 3 and the IC chip 4 may be mounted in different mounting spaces. This case will be described as the second embodiment with reference to Figure 6. Figure 6 is an end view of the crystal oscillator 101 according to the second embodiment, shown in the same way as Figure 2(a). Components identical to those in the first embodiment are denoted by the same reference numerals, and their descriptions are simplified or omitted.

[0042] As shown in Figure 6, the crystal oscillator 201 has a package 202, a crystal diaphragm 3 mounted in the concave first mounting space 202a of the package 202, an IC chip 4 mounted in the second mounting space 202b of the package 202, and a metal cover (lid) 205 for sealing the first mounting space 202a. Similar to the crystal oscillator 1 of the first embodiment, the crystal oscillator 201 is an electronic component that integrates a crystal diaphragm 3, which is an example of a piezoelectric diaphragm, and an IC chip 4, which is an oscillation circuit, into a single package, and can generate a stable frequency and produce a regular reference signal.

[0043] Package 202 is a ceramic package formed by stacking multiple ceramics on which a desired metal pattern is formed on the surface. Specifically, package 202 has a structure in which a first frame wall 211, which is a bank portion with an opening of a predetermined size, a second frame wall 212 having a smaller opening than the first frame wall 211, and a rectangular base 213 are stacked. Package 202 has a so-called H-shaped structure in which the first frame wall 211 is stacked on the upper surface 113a of the base 113 and the second frame wall 212 is stacked on the lower surface 213b of the base 213. With this structure, package 202 realizes a structure in which the quartz crystal oscillator 3 and the IC chip 4 can be mounted in separate mounting spaces.

[0044] A sealing conductor pattern 215 is formed on the upper surface of the first frame wall 211. The planar shape of the conductor pattern 215 is frame-shaped, similar to the first frame wall 211. A cover 205 is then joined to the conductor pattern 215 by known metal bonding. This seals the first mounting space 202a of the package, and the first mounting space 202a is sealed using a vacuum or a gas such as nitrogen.

[0045] Two rectangular crystal diaphragm mounting terminals (only crystal diaphragm mounting terminal 216 is shown in Figure 6) are formed on the upper surface 113a of the base 213. Conductive adhesive 18 is applied to each of these crystal diaphragm mounting terminals, and the crystal diaphragm 3 is mounted via these conductive adhesives 18. Each of the crystal diaphragm mounting terminals is also electrically connected to an external connection terminal via connection wiring (not shown) provided inside the package 202.

[0046] Four external connection terminals (only external connection terminals 220c and 220d are shown in Figure 6) are formed on the lower surface of the second frame wall 212. Each of these external connection terminals is connected via connection wiring (not shown) provided inside the package 202 to either of the six mounting pads 221a, 221b, 221c, 221d, 221e, and 221f (only mounting pads 21a to 21c are shown in Figure 6) provided on the upper surface 213b of the base 213, or to the crystal oscillator mounting terminals 216 and 217 provided on the upper surface 213a of the base 213.

[0047] Each mounting pad has an IC chip 104 mounted on it via a bump 31 made of gold or the like, using flip-chip bonding. It also has six IC terminals 241, each of which is electrically connected to the corresponding mounting pad 221a to 221f via the bump 31.

[0048] Here, as in the first embodiment, a base-raising member 251 is formed on the lower surface of the mounting pads 221b and 221e corresponding to the IC terminal 241 located in the central part of the IC chip 204, so that the position of the mounting pads 221b and 221e is higher than the position of the other mounting pads. Note that the process of joining the IC chip 204 and the base 213 according to this embodiment is the same as that shown in Figure 3 of the first embodiment, so its explanation will be omitted.

[0049] Similar to the first embodiment, the number of mounting sections is not particularly limited in this embodiment, and the heights of the multiple mounting sections may be set to increase in stages from both ends toward the center. Furthermore, the bottom-raising member 251 does not necessarily need to be stacked on the base 213 as a separate member, but may be formed integrally with the base 213 of the package 202.

[0050] Similar to the first embodiment, in this embodiment as well, the degree of melting of the bump 31 can be sufficiently large, and the load applied by the ultrasonic horn 60 can also be sufficient, thereby ensuring the bonding strength between the central part of the IC chip 204 and the base 213. As a result, the risk of connection failure or damage to the IC chip 204 can be suppressed, and the durability and reliability of the crystal oscillator 201 can be improved. Furthermore, in this embodiment, since the package 202 adopts an H-shaped structure, the crystal oscillator 201 can be made more space-saving, leading to miniaturization and a lower profile.

[0051] (Embodiments of this disclosure) A first embodiment of the present disclosure is a piezoelectric device comprising a rectangular base in plan view, a piezoelectric vibrator mounted in the inner region of the base, and an IC chip mounted on the base by welding with an ultrasonic horn, wherein the base has a plurality of mounting portions on its bottom surface, including mounting pads corresponding to the terminals of the IC chip, and the height from the surface opposite to the bottom surface on which the plurality of mounting portions are provided to the top surface of each of the plurality of mounting portions is higher in the center of the vibration direction of the ultrasonic horn than at both ends of the vibration direction.

[0052] In this way, by increasing the height of the mounting area in the center of the ultrasonic horn's vibration direction, it becomes possible to ensure the bonding strength of the IC chip, thereby improving the durability and reliability of the piezoelectric device.

[0053] A second embodiment of the present disclosure is that, in the first embodiment, at least a portion of the plurality of mounting portions further have a bottom-up member on the lower surface of the mounting pad. This eliminates the need for special processing during package molding and allows the package according to the present disclosure to be manufactured by reusing other packages.

[0054] A third embodiment of the present disclosure is that, in the first or second embodiment, the base member is made of molybdenum or ceramic. This prevents melting together with the bump during ultrasonic bonding and ensures the height of the mounting portion at the center of the vibration direction of the ultrasonic horn.

[0055] A fourth embodiment of this disclosure is that, in any of the first to third embodiments, the thickness of the base member is equal to or greater than the thickness of the mounting pad. This ensures that the height of the mounting portion at the center of the vibration direction of the ultrasonic horn is maintained.

[0056] A fifth embodiment of this disclosure is that, in any of the first to fourth embodiments, the height from the surface opposite to the bottom surface on which the plurality of mounting portions are provided to the top surface of each of the plurality of mounting portions is progressively increased from both ends in the vibration direction of the ultrasonic horn toward the center in the vibration direction. This makes it possible to bring the bonding strength of the IC chips at each mounting portion closer together, thereby further improving the durability and reliability of the piezoelectric device.

[0057] A sixth embodiment of the present disclosure is a package on which an IC chip is mounted by welding with an ultrasonic horn, comprising a rectangular base in plan view, and a plurality of mounting portions provided on the bottom surface of the base and having mounting pads corresponding to the terminals of the IC chip, wherein the height from the surface opposite to the bottom surface on which the plurality of mounting portions are provided to the top surface of each of the plurality of mounting portions is higher in the center of the vibration direction of the ultrasonic horn than at both ends in the vibration direction of the ultrasonic horn.

[0058] In this way, by increasing the height of the mounting area at the center of the ultrasonic horn's vibration direction, it becomes possible to provide a package that ensures the bonding strength of the IC chip and improves the durability and reliability of the piezoelectric device.

[0059] A seventh embodiment of the present disclosure is a method for manufacturing a piezoelectric device having a piezoelectric vibrator and an IC chip mounted by welding with an ultrasonic horn, comprising: a preparation step of preparing a package having a rectangular base in plan view and a plurality of mounting portions provided on the bottom surface of the base and having mounting pads corresponding to the terminals of the IC chip, wherein the height from the surface opposite to the bottom surface on which the plurality of mounting portions are provided to the top surface of each of the plurality of mounting portions is higher at the center of the vibration direction of the ultrasonic horn than at both ends of the vibration direction; an IC chip mounting step of placing the IC chip on the mounting pads, pressing the IC chip with an ultrasonic horn and mounting it by welding with ultrasonic vibration; a piezoelectric vibrator mounting step of mounting the piezoelectric vibrator on the mounting terminals of the base; and a sealing step of sealing the package with a cover. [Explanation of Symbols]

[0060] 1. Crystal oscillator (piezoelectric device) 2 packages 3. Crystal vibrating element (piezoelectric vibrating element) 4 IC chips 5 Cover (Lid) 11 Frame wall 13 Bass 13b Top surface (bottom surface) 21a~21f Mounted pads (mounting section) 41 IC terminal 51. Base-raising component (mounting section) 60 Ultrasonic Horns 213 Base 213b Bottom surface (bottom surface)

Claims

1. A rectangular base in plan view, A piezoelectric vibrator mounted in the inner region of the base, The IC chip is mounted on the base by welding using an ultrasonic horn, The base has a plurality of mounting sections on its bottom surface, including mounting pads corresponding to the terminals of the IC chip. A piezoelectric device characterized in that the height from the surface opposite to the bottom surface on which the plurality of mounting parts are provided to the upper surface of each of the plurality of mounting parts is higher in the center of the vibration direction of the ultrasonic horn than at both ends of the vibration direction.

2. The piezoelectric device according to claim 1, characterized in that at least a portion of the plurality of mounting portions further has a bottom-raising member on the lower surface of the mounting pad.

3. The piezoelectric device according to claim 2, characterized in that the base-raising member is molybdenum or ceramic.

4. The piezoelectric device according to claim 2 or 3, characterized in that the thickness of the base-raising member is greater than or equal to the thickness of the mounting pad.

5. The piezoelectric device according to claim 1, characterized in that the height from the surface opposite to the bottom surface on which the plurality of mounting parts are provided to the upper surface of each of the plurality of mounting parts increases in stages from both ends in the vibration direction of the ultrasonic horn toward the center in the vibration direction.

6. A package in which an IC chip is mounted by welding with an ultrasonic horn, A rectangular base in plan view, The base has a plurality of mounting sections provided on its bottom surface, each equipped with mounting pads corresponding to the terminals of the IC chip, A package characterized in that the height from the surface opposite to the bottom surface on which the plurality of mounting parts are provided, to the upper surface of each of the plurality of mounting parts, is higher in the center of the vibration direction of the ultrasonic horn than at both ends of the vibration direction.

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