Module manufacturing method and piezoelectric device

Abstract

To provide a method for manufacturing a module in which the risk of IC chip joints being broken or the IC chip peeling off is reduced, and to provide a piezoelectric device used therein. [Solution] A manufacturing method for a module in which a first mounting space for mounting a piezoelectric vibrator and a second mounting space for mounting an IC chip are arranged back to back, and a piezoelectric device having a base that is rectangular in plan view is mounted between the first mounting space and the second mounting space, the method comprising: a piezoelectric device mounting process for mounting the piezoelectric device on a circuit board; and an IC chip molding process for covering the periphery of the IC chip with only one type of resin material.

Description

[Technical Field]

[0001] The present disclosure relates to a piezoelectric device in which an integrated circuit chip and a piezoelectric vibrator are mounted, and a method for manufacturing a module using the same. [Background technology]

[0002] In various electronic devices such as mobile phones and personal computers, piezoelectric devices are mounted with a piezoelectric vibrator and an integrated circuit (IC) chip mounted in a single package to easily obtain the stable frequencies required for information processing, communication processing, etc. From the perspective of miniaturization of piezoelectric devices, it is widely known to use a so-called H-structure piezoelectric device in which the piezoelectric vibrator and the IC chip are mounted in separate compartments.

[0003] In H-structure piezoelectric devices, a resin material called underfill is filled between the IC chip and the base to ensure the bonding strength between them. Epoxy resin, which has a relatively low viscosity and excellent fluidity, is commonly used as the underfill material.

[0004] For example, Patent Document 1 discloses a crystal oscillator with an H-type structure. In this crystal oscillator, in order to reinforce the fixing strength of the IC chip in the second recess of the crystal oscillator, an underfill material made of resin or the like is filled into the second recess, and each component arranged on the circuit board is covered with a mold made of resin or the like (paragraph 0027, Figure 1(b)). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-050778 Summary of the Invention [Problem to be solved by the invention]

[0006] However, if different resins are used for the underfill and molding materials, stress will be generated when the crystal oscillator is placed on the circuit board and reflowed due to the difference in thermal expansion coefficients between the underfill and molding materials, which could result in damage (cracks) at the IC chip joint and lead to the IC chip peeling.

[0007] The present disclosure has been made in consideration of these problems, and its purpose is to provide a method for manufacturing a module that suppresses the occurrence of damage to IC chip joints and peeling of IC chips, and a piezoelectric device used therein. [Means for solving the problem]

[0008] According to one aspect of the present disclosure, there is provided "a method for manufacturing a module in which a first mounting space for mounting a piezoelectric vibrator and a second mounting space for mounting an IC chip are arranged back to back, and a piezoelectric device having a base that is rectangular in plan view is mounted between the first mounting space and the second mounting space, the method comprising: a piezoelectric device mounting process for mounting the piezoelectric device on a circuit board; and an IC chip molding process for covering the periphery of the IC chip with only one type of resin material."

[0009] According to one aspect of the present disclosure, there is provided a "piezoelectric device mounted on a circuit board and molded with a resin material, the piezoelectric device having a base that is rectangular in plan view and an IC chip mounted on the bottom surface of the base, the IC chip being molded with only one type of resin material." [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a method for manufacturing a module in which the occurrence of breakage of IC chip joints and separation of IC chips is suppressed, and a piezoelectric device used therein.

[0011] It should be noted that the above effects are merely examples for the sake of convenience of explanation, and the effects of the present disclosure are not limited to these. In addition to the above effects, the present disclosure can achieve any of the effects described herein. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of a crystal oscillator according to an embodiment. [Figure 2] 2(a) is an end view taken along the dashed line AA in FIG. 1, and FIG. 2(b) is an end view taken along the dashed line BB in FIG. 2(a). [Figure 3] FIG. 1 is a schematic diagram illustrating a module according to an embodiment. [Figure 4] 10 is a table showing simulation results of the thermal expansion coefficients and stresses of an underfill material and a molding material. [Figure 5] FIG. 3 is an end view of a crystal oscillator 1 according to a modified example of the embodiment, similar to FIG. 2(a). [Figure 6] 4 is a schematic diagram showing a module according to a modified example of the embodiment, similar to FIG. 3. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] Below, with reference to the drawings, a module manufacturing method according to the present disclosure and a crystal oscillator, which is an example of a piezoelectric device, will be described in detail. Note that the present disclosure is not limited to the content described below and can be implemented with any modifications within the scope of the present disclosure. Furthermore, the drawings used in each embodiment are schematic illustrations of the module manufacturing method and crystal oscillator according to the present disclosure, and may be partially emphasized, enlarged, reduced, or omitted to facilitate understanding, and may not accurately represent the scale or shape of each component. Furthermore, some numerical values ​​used in the embodiments and their variations are merely examples and can be modified in various ways as necessary. The same reference symbols are used to designate common components in the drawings.

[0014] (Embodiment) First, the basic structure of a crystal oscillator according to the present disclosure will be described with reference to Figures 1 and 2. Figure 1 is a perspective view of a crystal oscillator according to an embodiment. Figure 2(a) is an end view taken along dashed line AA in Figure 1, particularly an end view of the long side of the crystal oscillator. Figure 2(b) is an end view taken along dashed line BB in Figure 2(a), particularly an end view of the short side of the crystal oscillator.

[0015] As can be seen from FIGS. 1, 2(a), and 2(b), a crystal oscillator 1, which is an example of a piezoelectric device, includes a crystal oscillator package 2 (hereinafter simply referred to as package 2), a crystal vibrating piece 3 mounted in a recessed first mounting space 2a of the package 2, and a metal cover (lid) 5 for sealing the first mounting space 2a. The package 2 also includes a second mounting space (second chamber) 2b on the opposite side of the first mounting space (first chamber) 2a, in which an IC chip 4 is mounted. The crystal oscillator 1 is an electronic component that integrates a crystal vibrating piece 3, which is an example of a piezoelectric vibrator, and an IC chip 4, which is an oscillation circuit, in a single package. The crystal oscillator 1 is capable of generating a stable frequency and a regular reference signal. In other words, the crystal oscillator 1 includes a crystal resonator as an oscillation element. In addition to a crystal resonator, other oscillator elements, such as a surface acoustic wave (SAW) resonator, other piezoelectric resonators, or a microelectromechanical systems (MEMS) resonator, may also be used as the oscillation element. In other words, the piezoelectric vibrator is not limited to the quartz vibrating piece 3 as in this embodiment, but may be other materials having resonance characteristics (piezoelectric vibrating pieces made of ceramics, silicon, etc.), or a substrate or base for piezoelectric vibration used in MEMS vibrators, etc.

[0016] The package 2 is a ceramic package formed by laminating multiple ceramics with desired metal patterns formed on their surfaces. Specifically, the package 2 has a laminated structure in which a frame-shaped first frame wall 11 with an opening of a predetermined size, a frame-shaped second frame wall 12 with an opening smaller than that of the first frame wall 11, and a rectangular base 13 are laminated. In the package 2, the first frame wall 11 is laminated on the front surface 13a of the base 13, and the second frame wall 12 is laminated on the back surface 13b of the base 13. Due to this laminated structure with an H-shaped cross section, the package 2 has a first recessed mounting space 2a for mounting the quartz crystal vibrating piece 3 and a second recessed mounting space 2b for mounting the IC chip 4. This structure allows the quartz crystal vibrating piece 3 and the IC chip 4 to be mounted in separate mounting spaces.

[0017] Here, the shape of the package 2 is a substantially rectangular parallelepiped, and rectangular when viewed from above. In the following, the thickness direction of the crystal oscillator 1 and the package 2 is referred to as the vertical direction, and the direction perpendicular to the vertical direction is referred to as the horizontal direction. The horizontal direction may also be distinguished as the long side direction (longitudinal direction) and the short side direction (transverse direction) of the crystal oscillator 1 and the package 2. Furthermore, the surface of each component located above in the vertical direction may also be referred to as the front surface, and the surface located below may also be referred to as the back surface.

[0018] A sealing conductor pattern 15 is formed on the surface (the surface located on the upper side in the vertical direction) of the first frame wall 11 of the package 2. The planar shape of the conductor pattern 15 is frame-like, just like the first frame wall 11. A cover (lid) 5 is bonded onto the conductor pattern 15 by known metal bonding. This seals the first mounting space 2a of the package 2, and the first mounting space 2a is sealed using a vacuum or a gas such as nitrogen.

[0019] Two crystal resonator element mounting terminals 16, which are adhesive pads, are formed on the surface 13a of the base 13 of the package 2. In particular, the crystal resonator element mounting terminals 16 are provided on one end of the long side in the inner area surrounded by the first frame wall 11. The crystal resonator element 3 is mounted on the crystal resonator element mounting terminals 16 via a conductive adhesive 18. Meanwhile, four external connection terminals 20a, 20b, 20c, and 20d, which will be described later, are formed on the back surface of the second frame wall 12 of the package 2. Each of the crystal resonator element mounting terminals 16 is electrically connected to one of the external connection terminals 20a to 20d via connection wiring (not shown) provided inside the package 2.

[0020] A plurality of IC chip electrode terminals 21 are formed on the back surface 13b of the base 13 of the package 2. A conductive adhesive 31 is applied to each of the IC chip electrode terminals 21, and the IC chip 4 is mounted via these conductive adhesives 31. That is, in the crystal oscillator 1, the flip-chip type IC chip 4 is mounted by flip-chip bonding. Each of the IC chip electrode terminals 21 is electrically connected to one of the external connection terminals 20a to 20d via connection wiring (not shown) provided inside the package 2. The number and arrangement of the IC chip electrode terminals 21 can be changed as appropriate depending on the IC chip 4 to be mounted.

[0021] Four external connection terminals 20a to 20d are formed on the back surface of the second frame wall 12 of the package 2. Each of the external connection terminals 20a to 20d is connected to either a crystal vibrating piece mounting terminal 16, which is a piezoelectric vibrator connection terminal, or an IC chip electrode terminal 21, via a connection wiring (not shown) provided inside the package 2.

[0022] The quartz crystal vibrating piece 3 is formed in a rectangular shape in a plan view. As shown in Figures 2(a) and 2(b), the quartz crystal vibrating piece 3 is mounted so that its long and short sides are aligned with those of the quartz crystal oscillator 1. In other words, the long and short sides of the quartz crystal vibrating piece 3 are aligned with those of the quartz crystal oscillator 1, and the short sides of the quartz crystal vibrating piece 3 are aligned with those of the quartz crystal oscillator 1. The type of cutting of the quartz crystal vibrating piece 3 from a quartz crystal raw stone is not limited to AT cut, and other cuts, such as Z cut or SC cut, which are two-turn cuts, may also be used.

[0023] The quartz crystal vibrating piece 3 is fixed in a floating state relative to the quartz crystal vibrating piece mounting terminal 16 without directly contacting the quartz crystal vibrating piece mounting terminal 16 by the conductive adhesive 18 located on one side of the long side direction as described above.

[0024] The IC chip 4 includes an oscillation circuit that excites the crystal vibrating piece 3 and amplifies and outputs the oscillation signal using an inverter or the like, and a temperature characteristic compensation circuit that compensates for the temperature characteristics of the frequency of the crystal vibrating piece 3. The IC chip 4 is mounted in the second mounting space 2b, which is located on the opposite side of the first mounting space 2a in which the crystal vibrating piece 3 is mounted, and is electrically connected to the IC chip electrode terminals 21 via a conductive adhesive 31 by flip-chip bonding.

[0025] Next, a method for manufacturing a module according to the present disclosure will be described with reference to FIG. 3. FIG. 3 is a schematic diagram showing a module according to an embodiment. First, conductive adhesive 32 is applied to external connection terminals 20a to 20d. Then, crystal oscillator 1 is arranged so that a circuit board 61, which has a predetermined circuit pattern formed on a glass epoxy substrate, faces the back surface 13b of the base 13, and crystal oscillator 1 and circuit board 61 are fixed together (piezoelectric device mounting process). At this time, other electronic components 51 and 52 are also fixed to the circuit board 61 via conductive adhesives 33 and 34. For example, electronic components 51 and 52 may be capacitors, resistors, diodes, other crystal devices, etc. Naturally, the number of electronic components is not limited to two, and their arrangement may be changed as appropriate.

[0026] Thereafter, a resin member 41 is applied to the crystal oscillator 1 using a dispenser or the like, thereby coating each component of the crystal oscillator 1 (IC chip molding process). While epoxy resin, silicone resin, urethane resin, or the like can be used as the resin member 41, it is preferable to use an epoxy resin with a relatively low viscosity and excellent fluidity in order to achieve a tight coating. When applying the resin member 41, the resin member 41 penetrates into the second mounting space 2b, and the space (predetermined space) between the IC chip 4 and the base 13 is also filled with the resin member 41. As a result, the periphery of the IC chip 4 (crystal oscillator 1) is coated with only one type of resin member 41.

[0027] By using only one type of resin member 41 for covering, stress due to differences in thermal expansion coefficients does not occur during the subsequent reflow process, as compared to when two or more types of resin members are used. Therefore, according to this embodiment, it is possible to reduce the risk of damage to the conductive adhesive 31 or peeling of the IC chip 4 during module manufacturing. Furthermore, by covering each component of the crystal oscillator 1 with the resin member 41, it is possible to reduce the impact of changes in the external environment and improve reliability.

[0028] Here, the difference in thermal expansion coefficient and stress when two types of resin materials are generally used will be explained with reference to Fig. 4. Fig. 4 is a table showing the simulation results of the thermal expansion coefficient and stress of the underfill material and molding material, and shows the results when reflow is performed using different resin materials for the underfill material and molding material.

[0029] In FIG. 4, the "coefficient of thermal expansion (CTE)" is in the unit of "ppm / °C", and the larger the numerical value, the larger the coefficient of thermal expansion (thermal expansion rate). Also, "<Tg" indicates a temperature lower than the glass transition point, and when using a general molding material, the temperature becomes "<Tg". ">Tg" indicates a temperature higher than the glass transition point, and when using a general underfill material, the temperature becomes ">Tg". That is, the numerical value at "<Tg" indicates the coefficient of thermal expansion when using a molding material, and the numerical value at ">Tg" indicates the coefficient of thermal expansion when using an underfill material. Also, the "package interface stress" refers to the "stress related to the space (predetermined space) between the IC chip and the base", and the unit is "Mpa". The larger the numerical value of "Mpa", the greater the stress, and the force to peel the IC chip 4 from the base 13 will act.

[0030] Looking at Comparative Examples 1 to 5 in order, the coefficient of thermal expansion (ppm / °C) of the molding material at "<Tg" is "42" for Comparative Example 1, "35" for Comparative Example 2, "26" for Comparative Example 3, "18" for Comparative Example 4, and "11" for Comparative Example 5. Also, the coefficient of thermal expansion (ppm / °C) of the underfill material at ">Tg" is "120" for Comparative Example 1, "98" for Comparative Example 2, "75" for Comparative Example 3, "54" for Comparative Example 4, and "32" for Comparative Example 5. In addition, the package interface stress (Mpa) is "1907" for Comparative Example 1, "1476" for Comparative Example 2, "1131" for Comparative Example 3, "890" for Comparative Example 4, and "580" for Comparative Example 5.

[0031] In Comparative Example 1, there is a difference of "74" between the coefficient of thermal expansion of the molding material "42" and the coefficient of thermal expansion of the underfill material "120". Similarly, looking at it, in Comparative Example 2, it is a difference of "63", in Comparative Example 3, it is "49", in Comparative Example 4, it is "36", and in Comparative Example 5, it is "21", and gradually the coefficient of thermal expansion and its difference are becoming smaller. Similarly, for the package interface stress, the numerical value is decreasing as we refer from Comparative Example 1 to Comparative Example 5.

[0032] From the above, it can be seen that the smaller the difference in thermal expansion coefficient between the molding material and the underfill material, the smaller the package interface stress. In light of this, it can be inferred that if the difference in thermal expansion coefficient between the molding material and the underfill material is zero (i.e., if the molding material and the underfill material are the same resin), no package interface stress will occur. Therefore, according to this embodiment, it is possible to prevent the risk of damage to the conductive adhesive 31 or peeling of the IC chip 4 due to stress.

[0033] (Modification of the embodiment) In the above embodiment, after mounting the crystal oscillator 1 on the circuit board 61, the crystal oscillator 1 is molded in a single molding operation to manufacture a module. However, this molding operation does not need to be performed for all locations in one operation; it may be performed in multiple steps as long as the same resin is used. Such a case will be described as a modified example of the embodiment with reference to FIGS. 5 and 6. FIG. 5 is an end view of the crystal oscillator 1 according to a modified example of the embodiment, similar to FIG. 2(a), and particularly shows the space (predetermined space) between the IC chip 4 and the base 13 and the state in which the IC chip 4 is covered. FIG. 6 is a schematic diagram of a module according to a modified example of the embodiment, similar to FIG. 3. Note that the same components as those in the above embodiment are designated by the same reference numerals, and their descriptions will be simplified or omitted.

[0034] 5, in this modification, before the crystal oscillator 1 is mounted on the circuit board 61 (before the piezoelectric device mounting process), the periphery of the IC chip 4 is covered with the first resin member 42. Furthermore, as shown in FIG. 6, after the periphery of the IC chip 4 is covered with the first resin member 42, the crystal oscillator 1 is mounted on the circuit board 61, and the crystal oscillator 1 is molded with the second resin member 43 (IC chip molding process).

[0035] In this modification, the space (predetermined space) between the IC chip 4 and the base 13 and the IC chip 4 are simultaneously covered during the first molding operation. However, the predetermined space and the IC chip 4 may be molded separately. That is, only the predetermined space may be filled with the first resin member 42, and after mounting, the IC chip 4 may be covered with the second resin member 42 while molding. In other words, the first resin member 42 may be used as a conventional underfill material. Furthermore, only the predetermined space may be filled with the first resin member 42, and the IC chip 4 may additionally be covered with the first resin member 42, and then the crystal oscillator 1 may be mounted on the circuit board 61.

[0036] The same resin is used for the first resin member 42 and the second resin member 43. Therefore, when reflow is performed after the IC chip molding process, the first resin member 42 and the second resin member 43 have the same thermal expansion coefficient, so no stress is generated, and the risk of damage to the conductive adhesive 31 or peeling of the IC chip 4 can be reduced, as in the above embodiment.

[0037] (Embodiments of the present disclosure) A first embodiment of the present disclosure is a method for manufacturing a module having a first housing space for housing a quartz crystal vibrating piece and a second housing space for housing an IC chip, the method including a crystal oscillator mounting process for mounting the crystal oscillator on a circuit board and an IC chip molding process for covering the periphery of the IC chip with only one type of resin material, whereby the module can be manufactured with reduced risk of damage to the conductive adhesive or peeling of the IC chip due to stress caused by differences in the thermal expansion coefficients of the resin materials.

[0038] A second embodiment of the present disclosure is the same as the first embodiment, in that in the crystal oscillator mounting step, the crystal oscillator is mounted on the circuit board while maintaining a predetermined space between the base and the IC chip, and in the IC chip molding step, the predetermined space and the IC chip are molded using only the single type of resin material. This makes it possible to manufacture a module while reducing the risk of damage to the conductive adhesive or peeling of the IC chip due to stress caused by differences in the thermal expansion coefficients of the resin materials.

[0039] A third embodiment of the present disclosure is the first or second embodiment, wherein in the IC chip molding step, the predetermined space, the IC chip, and the crystal oscillator are molded using only the single type of resin material, thereby enabling the module to be manufactured with reduced risk of damage to the conductive adhesive or peeling of the IC chip due to stress caused by differences in the thermal expansion coefficients of the resin materials.

[0040] A fourth embodiment of the present disclosure is the same as the first embodiment, except that, prior to the crystal oscillator mounting step, the periphery of the IC chip is covered with a first resin member, and in the IC chip molding step, the crystal oscillator is molded with a second resin member that is the same as the first resin member. This makes it possible to manufacture a module with reduced risk of damage to the conductive adhesive or peeling of the IC chip due to stress caused by differences in the thermal expansion coefficients of the resin members, even when the molding process is performed in two separate steps.

[0041] A fifth embodiment of the present disclosure is a crystal oscillator mounted on a circuit board and molded with a resin member, the crystal oscillator having a base that is rectangular in plan view and an IC chip mounted on the bottom surface of the base, the IC chip being molded with only one type of resin member. This makes it possible to provide a crystal oscillator that reduces the risk of damage to the conductive adhesive or peeling of the IC chip due to stress caused by differences in the thermal expansion coefficients of the resin members. [Explanation of symbols]

[0042] 1. Crystal oscillator (piezoelectric device) 2 Crystal oscillator package (package) 2a First mounting space 2b Second mounting space 3. Quartz crystal resonator (piezoelectric vibrator) 4 IC chip 5 Cover (lid) 13. Bass 31 Conductive adhesive 41 Resin parts 42 First resin member 43 Second resin member

Claims

1. A method for manufacturing a module in which a first mounting space for mounting a piezoelectric vibrator and a second mounting space for mounting an IC chip are arranged back to back, and a piezoelectric device having a base that is rectangular in plan view is mounted between the first mounting space and the second mounting space, a piezoelectric device mounting step of mounting the piezoelectric device on a circuit board; an IC chip molding step of covering the periphery of the IC chip with only one type of resin material; A method for manufacturing a module, comprising:

2. In the piezoelectric device mounting step, the piezoelectric device is mounted on the circuit board while maintaining a predetermined space between the base and the IC chip, 2. The method for manufacturing a module according to claim 1, wherein in the IC chip molding step, the predetermined space and the IC chip are molded using only the one type of resin material.

3. 3. The method for manufacturing a module according to claim 2, wherein in the IC chip molding step, the predetermined space, the IC chip, and the piezoelectric device are molded using only the one type of resin member.

4. Before the piezoelectric device mounting step, the periphery of the IC chip is covered with a first resin member; 2. The method for manufacturing a module according to claim 1, wherein the IC chip molding step includes molding the piezoelectric device with a second resin member that is the same as the first resin member.

5. A piezoelectric device mounted on a circuit board and molded with a resin member, The piezoelectric device has a base that is rectangular in plan view and an IC chip mounted on a bottom surface of the base, the IC chip is molded using only one type of resin material; A piezoelectric device characterized by:

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