JP2024065119A - Piezoelectric vibrator and method for manufacturing the same - Google Patents

Abstract

[Problem] To provide a piezoelectric vibrator and a method for manufacturing a piezoelectric vibrator that can achieve both a reduction in the elastic modulus of a conductive holding member and an improvement in conductivity. [Solution] A piezoelectric vibrator includes a piezoelectric vibration element having an excitation electrode and a connection electrode electrically connected to the excitation electrode, a base member having an electrode pad, and a conductive holding member that connects the connection electrode and the electrode pad, the conductive holding member being a cured product of a conductive adhesive, the conductive adhesive including polydimethylsiloxane having vinyl groups at both ends, the polydimethylsiloxane having vinyl groups at both ends including a component having a molecular weight of 644 or more and 2500 or less, and the content of the component is 1 mol % or less. [Selected Figure] Figure 1

Description

The present invention relates to a piezoelectric vibrator and a method for manufacturing a piezoelectric vibrator.

Piezoelectric vibrators are widely used as signal sources for reference signals used in oscillators, bandpass filters, and the like. For example, a piezoelectric vibrator has a vibrating arm bonded to a base package via a conductive holding member. The conductive holding member is, for example, a cured conductive adhesive.

Patent Document 1 discloses a silicone elastic adhesive composition for airbags that contains (A) 100 parts by mass of an alkenyl group-containing organopolysiloxane, (B) an organohydrogenpolysiloxane having three SiH groups and no alkenyl groups, and (C) a catalytic amount of a platinum group metal catalyst, in which the number of hydrogen atoms bonded to silicon atoms contained in component (B) is an amount of 0.3 to 5.0 per alkenyl group bonded to silicon atoms contained in component (A).

Patent Document 2 discloses a conductive adhesive composition that contains: (A) an organopolysiloxane that contains two or more silicon atoms in one molecule and has an alkenyl group bonded to the silicon atom; (B) an organopolysiloxane that contains two or more silicon atoms in one molecule and has at least one hydrogen atom per silicon atom; (C) a catalytic amount of a platinum-based hydrosilylation catalyst; and (D) a conductive powder in an amount sufficient to exhibit conductivity.

Patent Document 3 discloses an adhesion promoter that includes (A) an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in the molecule, (B) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms in the molecule, and (C) a catalyst for hydrosilylation reactions, and has a weight average molecular weight in the range of 150 to 10,000, preferably in the range of 200 to 5,000, and the weight average molecular weight Mw/number average molecular weight Mn of component (A) is 2.0 or less, preferably 1.8 or less.

JP 2013-112722 A JP 2004-119254 A JP 2017-88644 A

However, in conventional technology, it is desirable to simultaneously reduce the elastic modulus of the conductive retaining member and improve its conductivity.

The present invention was made in consideration of these circumstances, and aims to provide a piezoelectric vibrator and a method for manufacturing a piezoelectric vibrator that can simultaneously reduce the elastic modulus of the conductive holding member and improve the conductivity.

A piezoelectric vibrator according to one aspect of the present invention comprises a piezoelectric vibration element having an excitation electrode and a connection electrode electrically connected to the excitation electrode, a base member having an electrode pad, and a conductive holding member connecting the connection electrode and the electrode pad, the conductive holding member being a cured product of a conductive adhesive, the conductive adhesive including polydimethylsiloxane having vinyl groups at both ends, the polydimethylsiloxane having vinyl groups at both ends including a component having a molecular weight of 644 or more and 2500 or less, and the content of the component being 1 mol% or less.

A method for manufacturing a piezoelectric vibrator according to one aspect of the present invention includes the steps of providing a conductive adhesive containing polydimethylsiloxane having vinylated ends between a connection electrode of a piezoelectric vibrator element and an electrode pad of a base member, and bonding the connection electrode and the electrode pad with a conductive retaining member formed by hardening the conductive adhesive, wherein the polydimethylsiloxane having vinylated ends contains 1 mol % or less of a component having a molecular weight of 644 or more and 2500 or less.

According to the present invention, it is possible to reduce the elastic modulus of the conductive retaining member while improving its conductivity.

1 is an exploded perspective view showing a schematic configuration of a quartz crystal resonator according to an embodiment; 1 is a cross-sectional view illustrating a schematic configuration of a quartz crystal resonator according to an embodiment. 1 is a plan view illustrating a schematic structure of an evaluation substrate used for measuring the resistance value of a conductive adhesive. 1 is a cross-sectional view showing a schematic structure of an evaluation substrate used for measuring the resistance value of a conductive adhesive. 1 is a graph showing the resistance value of the conductive adhesive of Example 1. 1 is a graph showing the elastic modulus of the conductive adhesive of Example 1. 13 is a graph showing the resistance value of the conductive adhesive of Example 2. 13 is a graph showing the elastic modulus of the conductive adhesive of Example 2. 13 is a graph showing the elastic modulus of the conductive adhesive of Example 3. 13 is a graph showing the hysteresis characteristics of the conductive adhesive of Example 3.

The configuration of a quartz crystal vibrator, which is an example of a piezoelectric vibrator according to an embodiment of the present invention, will be described below with reference to the drawings. In each figure, the X-axis, Y'-axis, and Z'-axis correspond to the crystallographic axes of the quartz crystal piece 11 described below. The X-axis corresponds to the electrical axis (polarity axis), the Y-axis corresponds to the mechanical axis, and the Z-axis corresponds to the optical axis. The Y'-axis and Z'-axis are axes that are rotated around the X-axis by a predetermined angle in the direction from the Y-axis to the Z-axis.

As shown in Figures 1 and 2, the quartz crystal vibrator 1 includes a quartz crystal vibrator element 10, which is an example of a piezoelectric vibrator element, a base member 30, a cover member 40, and a bonding member 50.

The quartz crystal vibration element 10 is an element that converts electrical energy into mechanical energy and vibrates the quartz crystal by the piezoelectric effect. The quartz crystal vibration element 10 includes a thin quartz crystal piece 11, a first excitation electrode 14a, a second excitation electrode 14b, a first extraction electrode 15a, a second extraction electrode 15b, a first connection electrode 16a, and a second connection electrode 16b.

The quartz crystal piece 11 is, for example, an AT-cut quartz crystal piece. The AT-cut quartz crystal piece 11 is formed so that in an orthogonal coordinate system consisting of an X-axis, a Y'-axis, and a Z'-axis that intersect with each other, the main surface is a plane parallel to the plane specified by the X-axis and the Z'-axis (hereinafter referred to as the "XZ' plane"; the same applies to planes specified by the other axes), and the thickness is in the direction parallel to the Y'-axis. For example, the AT-cut quartz crystal piece 11 is formed by etching a quartz crystal substrate (for example, a quartz crystal wafer) obtained by cutting and polishing a crystal of synthetic quartz crystal.

When an AT-cut type quartz crystal vibration element 10 uses an AT-cut type quartz crystal piece 11, the quartz crystal vibration element 10 has high frequency stability over a wide temperature range. The AT-cut type quartz crystal vibration element 10 uses a thickness shear vibration mode as the main vibration. The cut angle of the quartz crystal piece 11 may be, for example, a BT cut, a GT cut, or an SC cut. The quartz crystal vibration element may also be a tuning fork type quartz crystal vibration element that uses a quartz crystal piece with a cut angle called a Z-cut.

The quartz crystal piece 11 is, for example, rectangular plate-shaped and has an excitation portion 17 and peripheral portions 18, 19 adjacent to the excitation portion 17. The quartz crystal piece 11 may have a so-called flat plate structure, or may have a so-called mesa structure as shown in FIG. 1. In the quartz crystal piece 11 having a mesa structure, the excitation portion 17 protrudes from the peripheral portions 18, 19 on both sides of the first main surface 11A and the second main surface 11B. In the following description, the first main surface 11A includes the main surfaces of the excitation portion 17 and the peripheral portions 18, 19 when the Y' axis of the quartz crystal piece 11 is viewed from above, and the second main surface 11B includes the main surfaces of the excitation portion 17 and the peripheral portions 18, 19 when the Y' axis of the quartz crystal piece 11 is viewed from below.

The first excitation electrode 14a and the second excitation electrode 14b are provided on the excitation portion 17. The first excitation electrode 14a is provided on the first main surface 11A of the crystal piece 11, and the second excitation electrode 14b is provided on the second main surface 11B of the crystal piece 11. When the first main surface 11A of the crystal piece 11 is viewed in plan, the first excitation electrode 14a and the second excitation electrode 14b each have a rectangular shape and overlap each other substantially entirely.

The first extraction electrode 15a and the second extraction electrode 15b are provided on the peripheral portion 18. The first extraction electrode 15a is provided on the first main surface 11A of the crystal piece 11, and the second extraction electrode 15b is provided on the second main surface 11B of the crystal piece 11. The first extraction electrode 15a electrically connects the first excitation electrode 14a and the first connection electrode 16a. The second extraction electrode 15b electrically connects the second excitation electrode 14b and the second connection electrode 16b. For example, one end of the first extraction electrode 15a is connected to the first excitation electrode 14a, and the other end of the first extraction electrode 15a is connected to the first connection electrode 16a via a side electrode provided on a side surface connecting the first main surface 11A and the second main surface 11B of the crystal piece 11. In addition, one end of the second extraction electrode 15b is connected to the second excitation electrode 14b, and the other end of the second extraction electrode 15b is connected to the second connection electrode 16b via a side electrode provided on the side surface connecting the first main surface 11A and the second main surface 11B of the crystal piece 11.

The first connection electrode 16a and the second connection electrode 16b are provided on the peripheral portion 18. The first connection electrode 16a is provided on the first main surface 11A of the crystal piece 11, and the second connection electrode 16b is provided on the second main surface 11B of the crystal piece 11. The first connection electrode 16a is an electrode for electrically connecting the first excitation electrode 14a to the base member 30, and the second connection electrode 16b is an electrode for electrically connecting the second excitation electrode 14b to the base member 30. The first connection electrode 16a and the second connection electrode 16b are electrodes whose main component is gold (Au). The surfaces of the first connection electrode 16a and the second connection electrode 16b are composed of, for example, a metal layer whose main component is gold (Au).

The base member 30 is made of a sintered material such as insulating ceramic (alumina) and holds the quartz crystal vibration element 10 in an excitable state. The quartz crystal vibration element 10 is mounted on the upper surface 31A of the base member 30, and an external circuit board (not shown) is bonded to the lower surface 31B of the base member 30.

The base member 30 includes a first electrode pad 33a and a second electrode pad 33b. The first electrode pad 33a and the second electrode pad 33b are provided on the upper surface 31A of the substrate 31. The first electrode pad 33a and the second electrode pad 33b are terminals for electrically connecting the crystal vibration element 10 to the base member 30. The first electrode pad 33a and the second electrode pad 33b are electrodes mainly composed of Au (gold). The surfaces of the first electrode pad 33a and the second electrode pad 33b are composed of a metal layer mainly composed of gold (Au), for example. The surface of the first electrode pad 33a is in contact with the first conductive holding member 36a, and the surface of the second electrode pad 33b is in contact with the second conductive holding member 36b.

The base member 30 includes a first external electrode 35a, a second external electrode 35b, a third external electrode 35c, and a fourth external electrode 35d. The first external electrode 35a to the fourth external electrode 35d are provided on the lower surface 31B of the base 31. The first external electrode 35a and the second external electrode 35b are terminals for electrically connecting an external substrate (not shown) to the crystal unit 1. The first electrode pad 33a is electrically connected to the first external electrode 35a via a first through electrode 34a that penetrates the base 31 along the Y'-axis direction. The second electrode pad 33b is electrically connected to the second external electrode 35b via a second through electrode 34b that penetrates the base 31 along the Y'-axis direction. The third external electrode 35c and the fourth external electrode 35d are dummy electrodes to which electrical signals are not input or output, but may be ground electrodes that improve the electromagnetic shielding function of the cover member 20 by grounding the cover member 40. The third external electrode 35c and the fourth external electrode 35d may be omitted.

The base member 30 includes a first conductive holding member 36a and a second conductive holding member 36b. The first conductive holding member 36a is bonded to the first electrode pad 33a and the first connection electrode 16a, and electrically connects the first electrode pad 33a and the first connection electrode 16a. The second conductive holding member 36b is bonded to the second electrode pad 33b and the second connection electrode 16b, and electrically connects the second electrode pad 33b and the second connection electrode 16b. The first conductive holding member 36a and the second conductive holding member 36b hold the quartz crystal vibration element 10 at a distance from the base member 30 so that the excitation portion 17 can be excited.

The first conductive holding member 36a and the second conductive holding member 36b are cured products of a conductive adhesive containing a thermosetting resin, a photocurable resin, etc., and the main component of the first conductive holding member 36a and the second conductive holding member 36b is a silicone resin. The first conductive holding member 36a and the second conductive holding member 36b contain conductive particles. The conductive particles are, for example, metal particles containing silver (Ag). The elastic modulus of silicone resin is more stable than that of epoxy resin over a wide temperature range. By using silicone resin as the main component of the first conductive holding member 36a and the second conductive holding member 36b, the frequency-temperature characteristics of the quartz crystal vibration element 10 are improved compared to when epoxy resin is used as the main component.

The conductive adhesive is a silicone conductive adhesive and contains polydimethylsiloxane having vinylated ends. Specifically, the conductive adhesive contains, for example, polydimethylsiloxane having vinylated ends, organohydrogenpolysiloxane, silver powder, a petroleum solvent, an epoxy compound, and a platinum catalyst. The polydimethylsiloxane having vinylated ends contains a low molecular weight component having a molecular weight of 644 or more and 2500 or less, and the content of the component is 1 mol% or less. The polydimethylsiloxane having vinylated ends preferably has a number average molecular weight of 6200 or more. The polydimethylsiloxane having vinylated ends preferably has a number average molecular weight of 12700 or less.

When the synthesis procedure for polydimethylsiloxane having vinyl ends is different, the molecular weight distribution of the resulting polydimethylsiloxane having vinyl ends will also be different. Therefore, the inventors have discovered that the synthesis procedure shown below can be used to obtain polydimethylsiloxane having vinyl ends with a narrow molecular weight distribution and a content of low molecular weight components having a molecular weight of 644 or more and 2500 or less suppressed to 1 mol % or less. Note that the method for suppressing the content of low molecular weight components shown below is an example, and the conductive adhesive according to the present invention is not limited to the synthesis procedure shown below.

That is, first, a water/tetrahydrofuran (THF) mixed solution (1/99 (v/v), 92.9 μL, 5.16 mmol) was added to a methylene chloride (84 mL) solution of hexamethylcyclotrisiloxane (D3, 33.4 g, 150 mmol). Next, a THF solution of 1,3-trimethylene-2-propylguanidine (TMnPG) (1.06 mL, 100 mg mL ⁻¹ , 753 μmol) was added to initiate polymerization of hexamethylcyclotrisiloxane. After 6 hours and 50 minutes, dehydrated pyridine (2.49 mL, 30.9 mmol) and chlorodimethyl(vinyl)silane (2.78 mL, 20.6 mmol) were added to the reaction solution in that order to terminate the polymerization. After concentrating the crude product, unnecessary substances were removed from the resulting liquid by extraction with acetonitrile (100 mL) five times. After removing the acetonitrile phase, the mixture was concentrated under reduced pressure to obtain 28.5 g of the target polydimethylsiloxane having vinylated ends at both ends as a colorless oily liquid (number average molecular weight 6200). Furthermore, by changing the molar ratio of hexamethylcyclotrisiloxane to water using the same synthesis procedure, polydimethylsiloxanes having vinylated ends at both ends with number average molecular weights of 3600 and 12700 were obtained.

The process of providing the first conductive retaining member 36a and the second conductive retaining member 36b includes the process of providing a conductive adhesive containing polydimethylsiloxane having vinylated ends between the connection electrodes 16a, 16b of the quartz vibration element 10 and the electrode pads 33a, 33b of the base member 30, and the process of joining the connection electrodes 16a, 16b of the quartz vibration element 10 to the electrode pads 33a, 33b with the conductive retaining member formed by hardening the conductive adhesive. The polydimethylsiloxane having vinylated ends contains 1 mol% or less of a component having a molecular weight of 644 or more and 2500 or less. The process of providing the conductive adhesive between the connection electrodes 16a, 16b of the quartz crystal vibration element 10 and the electrode pads 33a, 33b of the base member 30 includes, for example, a coating process in which the conductive adhesive, the viscosity of which has been adjusted to form a paste, is applied onto the electrode pads 33a, 33b; a placement process in which the quartz crystal vibration element 10 is placed on the conductive adhesive and the conductive adhesive that has spread over the surfaces of the connection electrodes 16a, 16b supports the quartz crystal vibration element 10; and a curing process in which the conductive adhesive is cured.

Example 1
The conductive adhesive of Example 1 includes (A) an organopolysiloxane containing two or more silicon atoms in one molecule and having an alkenyl group bonded to the silicon atom, and (B) an organopolysiloxane containing two or more silicon atoms in one molecule and having at least one hydrogen atom per silicon atom, and 30 parts by weight of polydimethylsiloxane vinylated at both ends is added to the total amount of (A) and (B). In addition, the first sample of the polydimethylsiloxane vinylated at both ends of Example 1 has a distribution of number average molecular weight of 6200, in which the content of low molecular weight components having a molecular weight of 644 or more and 2500 or less is 18 mol % or less. The second sample of the polydimethylsiloxane vinylated at both ends of Example 1 has a distribution of number average molecular weight of 6200, in which the content of low molecular weight components having a molecular weight of 644 or more and 2500 or less is 18 mol % or less. The content of low molecular weight components having a molecular weight of 2500 or less is the ratio of the number of low molecular weight components having a molecular weight of 644 or more and 2500 or less to the total molecular weight of the polydimethylsiloxane having vinylated ends. The weight ratio of the components of the conductive adhesive is 65% conductive particles, 16% polymethylsilsesquioxane, 13% silicone resin, 4% solvent, and 2% epoxy resin. The silicone resin contains a low molecular weight component having a molecular weight of 644 or more and 2500 or less, and the content of this component is 22 mol% or less. The conductive adhesive of the comparative example is the same as the conductive adhesive of Example 1 except that it does not contain polydimethylsiloxane having vinylated ends.

Next, a method for evaluating the resistance value of the cured conductive adhesive will be described.
As shown in Fig. 3, the evaluation substrate B10 is provided with a first electrode pair E10, a second electrode pair E20, a third electrode pair E30, a fourth electrode pair E40, and a fifth electrode pair E50 arranged in this order. The first electrode pair E10 to the fifth electrode pair E50 are provided on an insulating substrate. The first electrode pair E10 has a pair of measurement electrodes E11, E12, and a bridge electrode E13 that connects the measurement electrodes E11 and E12. The second electrode pair E20 has a pair of measurement electrodes E21, E22, and a bridge electrode E23 that connects the measurement electrodes E21 and E22. The third electrode pair E30 has a pair of measurement electrodes E31, E32, and a bridge electrode E33 that connects the measurement electrodes E31 and E32. The fourth electrode pair E40 has a pair of measurement electrodes E41, E42 and a bridge electrode E43 connecting the measurement electrodes E41 and E42. The fifth electrode pair E50 has a pair of measurement electrodes E51, E52 and a bridge electrode E53 connecting the measurement electrodes E51 and E52. The central portions E1, E2, E3, E4, and E5 of the bridge electrodes E13 to E53 are covered with a cured product E9 of a conductive adhesive. The first electrode pair E10 to the fifth electrode pair E50 are electrically connected by the cured product E9 of the conductive adhesive.

The insulating substrate is, for example, an alumina substrate. The first electrode pair E10 to the fifth electrode pair E50 are metal electrodes with a laminated structure having a base layer made of nickel and a surface layer made of gold (Au). The surfaces of the first electrode pair E10 to the fifth electrode pair E50 are composed of a metal layer whose main component is gold (Au).

As shown in FIG. 4, the resistance value of the cured conductive adhesive E9 was evaluated by measuring the changes in resistance value 1-2 between the central portion E1 and the central portion E2, resistance value 1-3 between the central portion E1 and the central portion E3, resistance value 1-4 between the central portion E1 and the central portion E4, and resistance value 1-5 between the central portion E1 and the central portion E5. The resistance value 1-2 is determined by the contact resistance between the central portion E1 and the cured conductive adhesive E9, the resistance of the cured conductive adhesive E9 between the central portion E1 and the central portion E2, and the contact resistance between the cured conductive adhesive E9 and the central portion E2. Similarly, the resistance values 1-3, 1-4, and 1-5 are determined by the resistance of the cured conductive adhesive E9 itself and the contact resistance between the cured conductive adhesive E9 and the central portion of the electrode pair, respectively.

In the measurement of resistance value 1-2, in order to offset the influence of anything other than the central parts E1 and E2 and the cured product E9 of the conductive adhesive, the measurement was performed as follows. That is, the resistance value between measurement electrode E11 and measurement electrode E21, the resistance value between measurement electrode E11 and measurement electrode E22, the resistance value between measurement electrode E12 and measurement electrode E22, and the resistance value between measurement electrode E12 and measurement electrode E21 were measured, and the result of adding them up was determined as A. In addition, the resistance value between measurement electrode E11 and measurement electrode E12, and the resistance value between measurement electrode E21 and measurement electrode E22 were measured, and the result of adding them up and multiplying them by two was determined as B. Then, resistance value 1-2 was calculated by subtracting B from A and dividing by 4. Resistance value 1-3, resistance value 1-4, and resistance value 1-5 were calculated in the same manner.

(Evaluation results)
In the example shown in FIG. 5, the resistance values of the first sample, the second sample in the above-mentioned Example 1, and the conductive adhesive of the comparative example were measured. As shown in the figure, according to the evaluation results of Example 1, when the conductive adhesive contains polydimethylsiloxane having vinylated ends at both ends, the resistance value is higher than when the conductive adhesive does not contain polydimethylsiloxane having vinylated ends at both ends. In addition, in the distribution of the number average molecular weight of 6200, the second sample, which has a relatively small content of low molecular weight components having a molecular weight of 644 or more and 2500 or less, has a smaller resistance value than the first sample, which has a relatively large content of low molecular weight components having a molecular weight of 644 or more and 2500 or less. In other words, the resistance value of the conductive adhesive is reduced by reducing the content of low molecular weight components having a molecular weight of 644 or more and 2500 or less in the distribution of the number average molecular weight of 6200.

In the example shown in FIG. 6, the elastic modulus was measured for each of the conductive adhesives of the first sample, the second sample, and the comparative example in the above-mentioned Example 1. For example, the conductive adhesive was cured to prepare a sample of 5 cm x 1 cm x 0.3 cm, and the elastic modulus of the sample was measured in a temperature range of -40°C to 80°C. As shown in the figure, according to the evaluation results of Example 1, when both ends of the polydimethylsiloxane are vinylated, the elastic modulus is smaller than when both ends of the polydimethylsiloxane are not vinylated. In addition, in the distribution of the number average molecular weight of 6200, the second sample, which has a relatively small content of low molecular weight components with a molecular weight of 644 or more and 2500 or less, has a smaller elastic modulus than the first sample, which has a relatively large content of low molecular weight components with a molecular weight of 644 or more and 2500 or less. In other words, the elastic modulus of the conductive adhesive is reduced by reducing the content of low molecular weight components with a molecular weight of 644 or more and 2500 or less in the distribution of the number average molecular weight of 6200.

Therefore, as shown by comparing Figures 5 and 6, in a distribution with a number average molecular weight of 6200, if the content of low molecular weight components with a molecular weight of 644 or more and 2500 or less is small, it is possible to achieve both a reduction in the elastic modulus of the conductive adhesive and an improvement in its conductivity.

Example 2
The conductive adhesive of Example 2 includes (A) an organopolysiloxane containing two or more silicon atoms in one molecule and having an alkenyl group bonded to the silicon atom, and (B) an organopolysiloxane containing two or more silicon atoms in one molecule and having at least one hydrogen atom per silicon atom, and 60 parts by weight of polydimethylsiloxane vinylated at both ends was added to the total amount of (A) and (B). In the first sample of the polydimethylsiloxane vinylated at both ends of Example 2, the content of molecular weights of 644 or more and 2500 or less in the distribution of the number average molecular weight of 3600 is 31 mol % or less. In the second sample of the polydimethylsiloxane vinylated at both ends of Example 2, the content of molecular weights of 644 or more and 2500 or less in the distribution of the number average molecular weight of 6200 is 1 mol % or less. In the third sample of the polydimethylsiloxane having vinylated ends at both ends of Example 2, the content of molecular weights of 644 or more and 2500 or less is 0 mol % or less in the distribution of the number average molecular weight of 12700. The weight ratio of the components of the conductive adhesive is 65% conductive particles, 16% polymethylsilsesquioxane, 13% silicone resin, 4% solvent, and 2% epoxy resin. The silicone resin contains a low molecular weight component having a molecular weight of 644 or more and 2500 or less, and the content of this component is 22 mol % or less. The conductive adhesive of the comparative example is the same as the conductive adhesive of Example 2 except that it does not contain polydimethylsiloxane having vinylated ends at both ends.

(Evaluation results)
In the example shown in FIG. 7, the resistance values of the first, second and third samples in the second embodiment and the comparative conductive adhesive were measured. As shown in the figure, according to the evaluation results of the second embodiment, the conductive adhesive has a higher resistance value when it contains polydimethylsiloxane having vinylated ends at both ends than when it does not contain polydimethylsiloxane having vinylated ends at both ends. In addition, the second sample in which the number average molecular weight of polydimethylsiloxane having vinylated ends at both ends is 6200 and the third sample in which the number average molecular weight of polydimethylsiloxane having vinylated ends at both ends is 12700 have a lower resistance value than the first sample in which the number average molecular weight of polydimethylsiloxane having vinylated ends at both ends is 3600. That is, the number average molecular weight of polydimethylsiloxane having vinylated ends at both ends is preferably 6200 or more, and the resistance value of the conductive adhesive is reduced by increasing the number average molecular weight of polydimethylsiloxane having vinylated ends at both ends.

In the example shown in FIG. 8, the elastic modulus was measured for each of the first, second, and third samples in the above-mentioned Example 2 and the conductive adhesive of the comparative example. As shown in the figure, according to the evaluation results of Example 2, when both ends are vinylated polydimethylsiloxane is included, the elastic modulus is smaller than when both ends are not included. In addition, the first sample in which the number average molecular weight of both ends are vinylated polydimethylsiloxane is 3600, and the second sample in which the number average molecular weight of both ends are vinylated polydimethylsiloxane is 6200, have a smaller elastic modulus than the third sample in which the number average molecular weight of both ends are vinylated polydimethylsiloxane is 12700. In other words, the number average molecular weight of both ends are preferably 6200 or less, and the elastic modulus of the conductive adhesive is reduced by reducing the number average molecular weight of both ends are vinylated polydimethylsiloxane.

Therefore, as shown by comparing Figures 7 and 8, when the number average molecular weight of the polydimethylsiloxane vinylated at both ends is 6,200 or more, it is possible to achieve both a reduction in the elastic modulus of the conductive adhesive and an improvement in its conductivity.

Example 3
The conductive adhesive of Example 3 includes (A) an organopolysiloxane containing two or more silicon atoms in one molecule and having an alkenyl group bonded to the silicon atom, and (B) an organopolysiloxane containing two or more silicon atoms in one molecule and having at least one hydrogen atom per silicon atom, and 30 parts by weight of polydimethylsiloxane vinylated at both ends was added to the total amount of (A) and (B). In the distribution of the number average molecular weight of 6200, the content of the molecular weight of 644 or more and 2500 or less is 1 mol% or less in the polydimethylsiloxane vinylated at both ends of Example 3. The weight ratio of the components of the conductive adhesive is 65% conductive particles, 16% polymethylsilsesquioxane, 13% silicone resin, 4% solvent, and 2% epoxy resin. The silicone resin includes a low molecular weight component having a molecular weight of 644 or more and 2500 or less, and the molecular weight of the component is 22 mol% or less. The conductive adhesive of the comparative example is the same as the conductive adhesive of Example 2 except that it does not contain polydimethylsiloxane vinylated at both ends.

(Evaluation results)
In the example shown in Fig. 9, the elastic modulus was measured for each of the conductive adhesive of Example 3 and the conductive adhesive of the comparative example. According to the evaluation results shown in the figure, the conductive adhesive has a smaller elastic modulus when it contains polydimethylsiloxane having vinylated ends at both ends than when it does not contain polydimethylsiloxane having vinylated ends at both ends. In other words, the resistance value of the conductive adhesive is reduced by adding polydimethylsiloxane having vinylated ends at both ends.

In the example shown in FIG. 10, the hysteresis characteristics were measured for the conductive adhesive of Example 3 and the conductive adhesive of the comparative example. For the measurement of the hysteresis characteristics, for example, the frequency output of the quartz crystal resonator 1 was measured in the temperature range of -40°C to 85°C. According to the evaluation results shown in FIG. 11, the average value of the hysteresis characteristics of the frequency-temperature characteristics of the quartz crystal resonator 1 was improved by about 40% when the conductive adhesive of Example 3 was used compared to when the conductive adhesive of the comparative example was used. In other words, the elastic modulus of the conductive adhesive was reduced, and the stress on the quartz crystal resonator element 10 due to the deformation of the base member 30 caused by temperature changes was alleviated.

Below, some or all of the embodiments of the present invention will be described, and their effects will be explained. Note that the present invention is not limited to the following notes.

According to one aspect of the present invention, a piezoelectric vibrator is provided that includes a piezoelectric vibration element having an excitation electrode and a connection electrode electrically connected to the excitation electrode, a base member having an electrode pad, and a conductive holding member that connects the connection electrode and the electrode pad, the conductive holding member being a cured product of a conductive adhesive, the conductive adhesive including polydimethylsiloxane having vinyl groups at both ends, the polydimethylsiloxane having vinyl groups at both ends including a component having a molecular weight of 644 or more and 2500 or less, and the content of the component being 1 mol % or less.

According to one aspect of the present invention, a piezoelectric vibrator is provided in which the number average molecular weight of polydimethylsiloxane vinylated at both ends is 6,200 or more.

According to one aspect of the present invention, a piezoelectric vibrator is provided in which the number average molecular weight of polydimethylsiloxane vinylated at both ends is 12,700 or less.

According to one aspect of the present invention, a piezoelectric vibrator is provided in which the electrode pad is an electrode whose main component is Au.

According to one aspect of the present invention, a piezoelectric vibrator is provided in which the piezoelectric vibration element is a quartz crystal vibration element.

According to one aspect of the present invention, a method for manufacturing a piezoelectric vibrator is provided, which includes the steps of providing a conductive adhesive containing polydimethylsiloxane having vinyl ends between a connection electrode of a piezoelectric vibrator element and an electrode pad of a base member, and bonding the connection electrode and the electrode pad with a conductive retaining member formed by hardening the conductive adhesive, in which the polydimethylsiloxane having vinyl ends contains 1 mol % or less of a component having a molecular weight of 644 or more and 2500 or less.

As described above, according to one aspect of the present invention, it is possible to achieve both a reduction in the elastic modulus of the conductive retaining member and an improvement in the conductivity.

The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit of the present invention, and equivalents are also included in the present invention. In other words, designs modified by a person skilled in the art as appropriate are also included within the scope of the present invention as long as they include the characteristics of the present invention. For example, the elements of each embodiment and their arrangement, materials, conditions, shapes, sizes, etc. are not limited to those exemplified, and can be modified as appropriate. Furthermore, the elements of each embodiment can be combined to the extent technically possible, and combinations of these are also included within the scope of the present invention as long as they include the characteristics of the present invention.

REFERENCE SIGNS LIST 1... quartz crystal vibrator 10... quartz crystal vibrator element 11... quartz crystal piece 14a... first excitation electrode 14b... second excitation electrode 15a... first extraction electrode 15b... second extraction electrode 16a... first connection electrode 16b... second connection electrode 30... base member 33a... first electrode pad 33b... second electrode pad 36a... first conductive holding member 36b... second conductive holding member 40... cover member 50... bonding member.

Claims (6)

A piezoelectric vibration element having an excitation electrode and a connection electrode electrically connected to the excitation electrode;
A base member having an electrode pad;
a conductive holding member that connects the connection electrode and the electrode pad;
Equipped with
the conductive holding member is a cured product of a conductive adhesive,
The conductive adhesive includes polydimethylsiloxane having both ends vinylated,
The polydimethylsiloxane having vinyl groups at both ends contains a component having a molecular weight of 644 or more and 2,500 or less, and the content of the component is 1 mol % or less.
Piezoelectric vibrator. The number average molecular weight of the polydimethylsiloxane vinylated at both ends is 6,200 or more.
The piezoelectric vibrator according to claim 1 . The number average molecular weight of the polydimethylsiloxane having vinyl groups at both ends is 12,700 or less.
The piezoelectric vibrator according to claim 2 . The electrode pad is an electrode mainly composed of Au.
The piezoelectric vibrator according to claim 1 . The piezoelectric vibration element is a quartz crystal vibration element.
The piezoelectric vibrator according to claim 1 . providing a conductive adhesive containing polydimethylsiloxane having vinyl ends between a connection electrode of the piezoelectric vibration element and an electrode pad of a base member;
a step of joining the connection electrodes and the electrode pads by a conductive holding member obtained by curing the conductive adhesive;
Including,
The polydimethylsiloxane having vinyl groups at both ends has a content of 1 mol % or less of a component having a molecular weight of 644 or more and 2,500 or less.
A method for manufacturing a piezoelectric vibrator.

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