JP2009105804A - Quartz crystal vibrator and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a quartz crystal vibrator which uses a conductive adhesive of excellent characteristics, and to provide a method of manufacturing the same. <P>SOLUTION: A quarts crystal vibrator includes: a quartz crystal vibrating chip 10 including a base 16 and a vibrating arm 18 extending from the base 16; an excitation electrode 32 formed in the vibrating arm 18; a connection electrode 40 formed in the quartz crystal vibrating chip 10 and electrically connected to the excitation electrode 32; a package 42 housing the quartz crystal vibrating chip 10 inside; a fixed electrode 50 formed on an inner surface of the package 42; and a conductive adhesive 54 for electrically and mechanically bonding the connection electrode 40 and the fixed electrode 50. The connection electrode 40 and the fixed electrode 50 include a surface constituted of Au. The conductive adhesive 54 contains a binder containing a bismaleimide resin and a conductive filler diffused in the binder, and the binder is constituted by excluding a polymer compound other than the bismaleimide resin. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a crystal resonator and a manufacturing method thereof.

  A crystal resonator having a structure in which an electrode of a crystal vibrating piece and an electrode of a package are bonded with a conductive adhesive is known. The electrode has a surface layer made of Au on a base film such as Cr or Ni, and is electrically conductive. The adhesive binder is a silicone resin. In this structure, since the adhesion between the silicone resin and Au is poor, the resistance value at the connection interface between the conductive adhesive and the electrode is high. Alternatively, since the curing speed of the silicone resin precursor is slow on the Au surface, a silicone film may remain as an insulating layer on the Au surface.

  As a countermeasure, it is conceivable to use a resin other than a silicone resin as a binder (see Patent Document 1). However, for example, an epoxy resin is hard when cured, so it cannot absorb the impact applied to the package, and does not satisfy the necessary conditions for heat resistance. Similarly, the polyimide resin does not satisfy the necessary condition for impact resistance, and the urethane resin does not satisfy the necessary condition for heat resistance.

Alternatively, Patent Document 2 discloses the use of an organic binder selected from a synthetic rubber, a silicone resin, and a thermoplastic polyester resin, but these materials do not satisfy the necessary conditions for heat resistance. Alternatively, Patent Document 3 describes that a binder is composed of a bismaleimide resin, an epoxy resin, and a conductive powder. However, the inclusion of an epoxy resin makes it necessary for impact resistance and heat resistance. Does not meet.
JP 2003-224444 A JP 2005-166322 A JP-A-4-369908

  An object of the present invention is to provide a crystal resonator using a conductive adhesive having excellent characteristics and a method for manufacturing the crystal resonator.

(1) The crystal resonator according to the present invention is
A quartz crystal resonator element including a base and a vibrating arm extending from the base;
An excitation electrode formed on the vibrating arm;
A connection electrode formed on the quartz crystal resonator element and electrically connected to the excitation electrode;
A package for accommodating the quartz crystal vibrating piece therein;
A fixed electrode formed on the inner surface of the package;
A conductive adhesive for electrically and mechanically joining the connection electrode and the fixed electrode;
Including
The connection electrode and the fixed electrode have a surface made of Au,
The conductive adhesive includes a binder containing a bismaleimide resin and a conductive filler dispersed in the binder, and the binder is configured by removing a polymer compound other than the bismaleimide resin. According to the present invention, since the high molecular compound constituting the binder is only bismaleimide resin, it has excellent adhesion to Au, heat resistance and flexibility, and good electrical and mechanical properties between the crystal vibrating piece and the package. Can be obtained.
(2) In the crystal unit,
The binder may further include an additive made of a low molecular compound.
(3) A method for manufacturing a crystal resonator according to the present invention includes:
A quartz crystal resonator element comprising a base and a vibrating arm extending from the base and having an excitation electrode formed on the vibration arm and electrically connected to the excitation electrode, and a fixed electrode on the inner surface Including inside the formed package, and electrically and mechanically joining the connection electrode and the fixed electrode with a conductive adhesive,
The connection electrode and the fixed electrode have a surface made of Au,
The conductive adhesive includes a binder containing a bismaleimide resin precursor and a conductive filler dispersed in the binder, and the binder is configured by excluding a polymer compound precursor other than the bismaleimide resin precursor. ing. According to the present invention, since the polymer compound precursor constituting the binder is only the bismaleimide resin precursor, it has excellent adhesion to Au, heat resistance and flexibility, and good electrical connection between the quartz crystal vibrating piece and the package. And mechanical and mechanical joints can be obtained.

  1 is a cross-sectional view showing a crystal resonator according to an embodiment of the present invention, FIG. 2 is a plan view of the crystal resonator shown in FIG. 1, and FIG. 3 is a crystal resonator shown in FIG. FIG. FIG. 4 is a plan view showing a crystal vibrating piece (tuning fork type crystal vibrating piece) used in the crystal resonator according to the embodiment of the present invention.

  The crystal resonator has a crystal resonator element 10. The bottom view of the quartz crystal vibrating piece 10 shown in FIG. 4 appears symmetrically with the plan view. The quartz crystal resonator element 10 has first and second surfaces 12 and 14 that define thicknesses facing each other and are made of quartz. The quartz crystal vibrating piece 10 includes a base portion 16 and a pair of vibrating arms 18 extending from the base portion 16.

  FIG. 5 is an enlarged cross-sectional view taken along line VV of the quartz crystal vibrating piece 10 shown in FIG. The resonating arm 18 includes first and second surfaces 12 and 14 and first and second side surfaces 20 and 22 that connect the first and second surfaces 12 and 14 on both sides. The first side surface 20 of one (left side in FIG. 5) vibrating arm 18 and the second side surface 22 of the other (right side in FIG. 5) vibrating arm 18 are arranged in parallel. The first side surface 20 is formed to have a mountain shape that increases in the center direction of the thickness of the vibrating arm 18 defined by the distance between the first and second surfaces 12 and 14.

  In the vibrating arm 18, first and second grooves 24 and 26 extending in the longitudinal direction are formed on the first and second surfaces 12 and 14, respectively. The first and second grooves 24 and 26 make the vibrating arm 18 easy to move and vibrate efficiently, so the CI value can be lowered.

  The quartz crystal vibrating piece 10 includes a pair of support arms 28. The pair of support arms 28 extend in directions opposite to the direction in which the pair of vibrating arms 18 extend from the base portion 16, and extend in opposite directions, and further bend and extend in the direction in which the pair of vibrating arms 18 extend. By bending, the support arm 28 is downsized. The support arm 28 is a portion that is attached to the package 42, and the attachment of the support arm 28 causes the vibrating arm 18 and the base portion 16 to float from the package 42.

  A pair of cuts 30 are formed in the base portion 16 so as to face each other so that a shape confined on the same side as the first and second surfaces 12 and 14 of the vibrating arm 18 appears. The pair of cuts 30 are formed in the base 16 adjacent to the pair of support arms 28 on the side where the pair of support arms 28 extends from the base 16 and bends. Since the transmission of the vibration of the vibrating arm 18 is blocked by the notch 30, it is possible to suppress the vibration from being transmitted to the outside (vibration leakage) through the base 16 and the support arm 28, and to prevent the CI value from increasing. . As the length (depth) of the cuts 30 is longer (deeper) within a range in which the strength of the base portion 16 can be secured, the vibration leakage suppressing effect is larger. The width between the pair of cuts 30 (the width of the portion sandwiched between the pair of cuts 30) may be smaller than the distance between the first and second side surfaces 20 and 22 of the pair of vibrating arms 18 facing each other. However, the distance may be smaller or larger than the distance between the first and second side surfaces 20 and 22 of the pair of vibrating arms 18 facing each other.

  An excitation electrode 32 is formed on the vibrating arm 18. The excitation electrode 32 is formed separately on the first side surface 20, the second side surface 22, the inner surface of the first groove 24, and the inner surface of the second groove 26 of the vibrating arm 18. Excitation electrodes 32 formed on the first and second side surfaces 20, 22 are electrically connected on the tip of the vibrating arm 18, and are formed on the inner surfaces of the first and second grooves 24, 26. The electrode 32 is electrically connected on the side surface of the base portion 16 and on the side surface of the support arm 28. The excitation electrode 32 on the first and second side surfaces 20 and 22 of one vibrating arm 18 and the excitation electrode 32 on the inner surfaces of the first and second grooves 24 and 26 of the other vibrating arm 18 are on the base 16. Are electrically connected to each other to form the first pattern 33, and the excitation electrode 32 on the inner surface of the first and second grooves 24, 26 of one vibrating arm 18 and the first and second of the other vibrating arm 18. The excitation electrodes 32 on the two side surfaces 20 and 22 are electrically connected on the base 16 to form a second pattern 35.

  The electrode film 34 that electrically connects the excitation electrodes 32 formed on the first and second side surfaces 20 and 22 on the vibrating arm 18 serves as a weight of the vibrating arm 18, and a part of the electrode film 34 is used. The weight can be adjusted by removing the weight. The heavier the tip of the vibrating arm 18, the lower the vibration frequency of the vibrating arm 18, and the lighter the vibration frequency of the vibrating arm 18 becomes. This can be used to adjust the frequency. Therefore, first and second electrode film removal portions 36 and 38 are formed on the electrode film 34. The first and second surfaces 12 and 14 of the vibrating arm 18 are exposed from the first and second electrode film removal portions 36 and 38.

  A connection electrode 40 is formed on the crystal vibrating piece 10. The connection electrode 40 is formed on the support arm 28, is formed at least on the first and second surfaces 12, 14 of the support arm 28, and is also formed on the side surface of the support arm 28. The connection electrode 40 is electrically connected to the excitation electrode 32. Specifically, the connection electrode 40 formed on one support arm 28 is electrically connected to the excitation electrode 32 that forms part of the first pattern 33 described above, and the connection electrode 40 formed on one support arm 28. Is electrically connected to the excitation electrode 32 forming a part of the second pattern 35 described above.

  At least the connection electrode 40 has a surface made of Au. For example, an underlying Cr film having a thickness of 100 to 300 mm, and an Au film having a thickness of 200 to 500 mm formed on the Cr film, The multilayer structure may be included. The Cr film has high adhesion to the crystal, and the Au film has low electrical resistance and is difficult to oxidize.

  In the present embodiment, a voltage is applied between the excitation electrode 32 formed on the inner surface of the first and second grooves 24 and 26 and the excitation electrode 32 formed on the first side surface 20, A voltage is applied between the excitation electrode 32 formed on the inner surfaces of the second grooves 24 and 26 and the excitation electrode 32 formed on the second side surface 22. The applied voltage generates an electric field as shown by the arrow in FIG. The excitation electrode 32 is connected to an AC power supply by a cross wiring, and is applied with an alternating voltage as a drive voltage. As a result, the vibrating arms 18 are excited and bent to vibrate so that the vibration arms 18 are in opposite-phase vibrations (the tip sides of the vibrating arms 18 approach and separate from each other). Further, the alternating voltage as the drive voltage is adjusted so as to vibrate in the basic mode.

  The crystal resonator includes a package 42 that houses the crystal resonator element 10 therein. The package 42 includes a bottom portion 44 to which the crystal vibrating piece 10 is fixed, and a frame wall portion 46 surrounding the bottom portion 44. A vent hole 48 for evacuation is formed in the bottom 44, and the vent hole 48 is closed with a seal portion 49 made of a brazing material (AuGe or the like).

  A fixed electrode 50 is formed on the inner surface of the package 42 (bottom 44). The fixed electrode 50 has a surface made of Au. External terminals 52 are formed on the outer surface of the package 42 (bottom 44). The fixed electrode 50 and the external terminal 52 are electrically connected by a wiring (not shown). The crystal vibrating piece 10 has two support arms 28, two external terminals 52 are formed on the package 42, and the connection electrode 40 on one support arm 28 is electrically connected to one external terminal 52. The connection electrode 40 on the other support arm 28 is electrically connected to the other external terminal 52. The external terminals 52 are mounted on a circuit board wiring pattern (not shown) by solder or the like.

  The crystal vibrating piece 10 is fixed to the package 42 (bottom 44). The quartz crystal vibrating piece 10 is fixed so that the vibrating arm 18 extends from the base portion 16 toward the frame wall portion 46. The support arm 28 is fixed to the bottom 44, and the vibrating arm 18 is in a state of floating from the package 42. The bottom 44 has a low area facing the tip of the vibrating arm 18 so that the bottom 44 is difficult to contact the bottom 44 even if the vibrating arm 18 is bent.

  The package 42 and the crystal vibrating piece 10 are fixed by the conductive adhesive 54. The conductive adhesive 54 electrically and mechanically joins the connection electrode 40 and the fixed electrode 50. In the present embodiment, only the connection electrode 40 and the fixed electrode 50 are bonded by the conductive adhesive 54, and the material of the crystal vibrating piece 10 (crystal) and the material of the package 42 (ceramics) are not bonded. These may be joined. The conductive adhesive 54 includes a binder containing a bismaleimide resin and a conductive filler dispersed in the binder. Examples of the conductive filler include those formed of Ag, having an average particle size of 5 μm, and granular or flaky. The content of the conductive filler may be 84 wt% (binder: 16 wt%). The binder is configured by excluding polymer compounds other than bismaleimide resin (for example, epoxy resin, urethane resin, polyimide resin, silicone resin, polyester resin). The binder may further include an additive made of a low molecular compound.

  According to the present embodiment, since the high molecular compound precursor constituting the binder is only the bismaleimide resin precursor, adhesion to Au constituting the surfaces of the connection electrode 40 and the fixed electrode 50, heat resistance, and flexibility are improved. It is excellent, and a good electrical and mechanical joining state between the crystal vibrating piece 10 and the package 42 can be obtained.

  The package 42 may be entirely formed of metal, but when it is mainly formed of non-metal such as ceramics, the upper end surface of the frame wall portion 46 is metallized. A Mo (or W) film, a Ni film, and an Au film are sequentially laminated on the non-metal part of the frame wall part 46, and the upper end surface is made of Au. The upper end surface has a shape surrounding the upper portion of the bottom portion 44. A ring 56 is fixed to the upper end surface via a brazing material layer made of an alloy containing Ag, for example. The ring 56 overlaps the upper end surface and surrounds the upper portion of the bottom portion 44 without a break. The ring 56 is for seam welding and has a layer made of, for example, Kovar. A lid is fixed to the ring 56.

  The lid 58 overlaps the package 42 to which the crystal vibrating piece 10 is fixed, and closes the opening of the package 42. The lid 58 has a through hole 60 that penetrates the front surface and the back surface. The through hole 60 has a circular opening shape. The lid 58 includes a light transmissive member 62 made of a material such as glass or resin. The light transmissive member 62 is in close contact with the inner surface of the through hole 60.

  An oscillator or a sensor can be configured using the above-described crystal resonator. When an oscillator is constituted by an oscillation circuit including a crystal resonator, an AC signal with high frequency accuracy can be obtained. A sensor using a crystal resonator is a sensor that detects a physical quantity by utilizing the fact that the frequency of the crystal vibrating piece 10 varies according to the physical quantity. For example, a sensor that detects stress generated by temperature, acceleration, Coriolis force generated by angular velocity, and the like can be given as an example.

  Next, a method for manufacturing a crystal resonator according to an embodiment of the present invention will be described. The method for manufacturing the crystal resonator includes the formation of the crystal resonator element 10. When the quartz crystal vibrating piece 10 is made of quartz, the quartz wafer is cut out by rotating in the range of 0 to 5 degrees clockwise around the Z axis in an orthogonal coordinate system composed of the X, Y, and Z axes. A quartz Z plate obtained by cutting and polishing to a predetermined thickness is used. A plurality of crystal vibrating pieces 10 are cut out from one crystal wafer in a connected state, and finally cut into individual crystal vibrating pieces 10. An excitation electrode 32, a connection electrode 40, and an electrode film 34 are formed on the crystal vibrating piece 10.

  The step of removing a part of the electrode film 34 to form the first electrode film removal portion 36 is performed before the step of fixing the crystal vibrating piece 10 to the package 42. That is, the first electrode film removing unit before being incorporated into the crystal resonator (before or after individually cutting the plurality of crystal vibrating pieces 10 cut out in a state of being connected from the crystal wafer). The frequency adjustment is performed by forming 36. A part of the electrode film 34 is removed by a laser beam. Since the first electrode film removing unit 36 is closer to the tip of the vibrating arm 18 than the second electrode film removing unit 38, the effect of making the vibrating arm 18 easy to vibrate (increasing the frequency) is great. The frequency adjustment process by forming the first electrode film removal unit 36 is intended for rough adjustment and can be called rough adjustment. Since the frequency adjustment has already been performed before the crystal vibrating piece 10 is attached to the package 42, the removal amount of the electrode film 34 due to the formation of the second electrode film removal portion 38 to be performed next can be reduced.

  In the method for manufacturing a crystal resonator, a package 42 is prepared. A ring 56 is fixed to the frame wall 46 of the package 42 by brazing. Then, the crystal vibrating piece 10 is fixed to the bottom portion 44. A conductive adhesive 54 is used for the fixing. The conductive adhesive 54 before curing includes a binder containing a bismaleimide resin precursor and a conductive filler dispersed in the binder. The binder is constituted by excluding a polymer compound precursor other than the bismaleimide resin precursor. The other details correspond to the self-evident content from the description of the structure of the crystal resonator described above.

  The method for manufacturing the crystal resonator includes disposing the lid 58 so that the lower surface of the light transmissive member 62 faces the electrode film 34 and joining the frame wall portion 46 and the lid 58 together. Joining is performed by seam welding. Thus, the opening of the package 42 is closed by the lid 58. Since the lid 58 is joined by seam joining, local heating is performed but overall heating is not performed. Therefore, since the distortion generated in the crystal vibrating piece 10 due to heat is small, the removal of the electrode film 34 by the formation of the second electrode film removal portion 38 for frequency adjustment is sufficient, and the generation of gas is small. In addition, in order to suppress distortion of the light transmissive member 62 when performing seam bonding, the position of the light transmissive member 62 is separated from the portion where seam bonding is performed.

  After the opening of the package 42 is closed by the lid 58, the inside of the package 42 closed by the lid 58 is evacuated through the air holes 48 formed in the package 42, and then the air holes 48 are closed by a brazing material.

  The method for manufacturing a crystal resonator further includes a step of forming the second electrode film removal unit 38. This step is performed after the opening of the package 42 is closed by the lid 58 (for example, after the evacuation step). This step is performed by irradiating the electrode film 34 with a laser beam through the light transmissive member 62. Since the second electrode film removal unit 38 is farther from the tip of the vibrating arm 18 than the first electrode film removal unit 36, the effect of facilitating the vibration arm 18 to vibrate (increasing the frequency) is small. On the contrary, it can be said that fine adjustment is possible.

  The method for manufacturing a crystal resonator according to the present embodiment includes the above process, and further includes a manufacturing process that is obvious from the configuration of the crystal resonator described above.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same purposes and results). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

  Next, a characteristic test result of the crystal resonator according to the present embodiment will be described. In the following description, “bismaleimide-based conductive adhesive” refers to the conductive adhesive described above.

1. Comparison of occurrence of defective rate due to continuity inhibition or increase in resistance value About bismaleimide conductive adhesive and silicone conductive adhesive, the occurrence of defective products due to electrical continuity inhibition or resistance increase was counted as follows. Results.

  As is clear from this result, it is possible to prevent electrical conduction inhibition or increase in resistance value by using a bismaleimide conductive adhesive.

2. Reflow test When a reflow test was performed on the bismaleimide conductive adhesive and the silicone conductive adhesive, the following results were obtained.

Test conditions JEDEC standard n number: 22pcs

  When the bismaleimide conductive adhesive was used, the number of defective products was zero.

3. Aging test When an aging test was performed on the bismaleimide conductive adhesive and the silicone conductive adhesive, the following results were obtained.

Test conditions After 150 ° C 120H n number: 22pcs

  From this result, it was found that the bismaleimide-based conductive adhesive had a lower ΔCI value than the silicone-based conductive adhesive, and the generated gas was less than that of the silicone-based conductive adhesive.

4). Drop impact resistance The elastic modulus of bismaleimide conductive adhesive, general silicone conductive adhesive, and general epoxy conductive adhesive is as follows.

  The bismaleimide-based conductive adhesive has an elastic modulus that is intermediate between that of a general silicone-based conductive adhesive and a general epoxy-based conductive adhesive. And when the drop test was done about the bismaleimide type conductive adhesive and the silicone type conductive adhesive, the following results were obtained.

Test condition: 1.8m on concrete, 100g load drop 40 drops n number: 22pcs of each resin

  From this result, it was found that the bismaleimide conductive adhesive has the same drop impact resistance as the silicone conductive adhesive.

5). Adhesiveness When the tip of the tuning fork vibrator was pulled and the tensile force when the fracture or peeling occurred was measured, the following results were obtained.

  From this result, the silicone-based conductive adhesive is weak and breaks at the gold-adhesive interface, whereas the bismaleimide-based conductive adhesive is strong and the crystal itself is broken. Thus, it was found that the bismaleimide conductive adhesive had better adhesion than the silicone conductive adhesive, and the interface conductivity was also good.

FIG. 1 is a cross-sectional view showing a crystal resonator according to an embodiment of the present invention. FIG. 2 is a plan view of the crystal resonator shown in FIG. FIG. 3 is a bottom view of the crystal unit shown in FIG. FIG. 4 is a plan view showing the crystal vibrating piece 10 used in the crystal resonator according to the embodiment of the invention. FIG. 5 is an enlarged cross-sectional view taken along line VV of the quartz crystal vibrating piece 10 shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Crystal vibrating piece 12 ... 1st surface 14 ... 2nd surface 16 ... Base part 18 ... Vibrating arm 20 ... 1st side surface 22 ... 2nd side surface 24 ... 1st groove | channel, 26 ... second groove, 28 ... support arm, 30 ... notch, 32 ... excitation electrode, 33 ... first pattern, 34 ... electrode film, 35 ... second pattern, 36 ... first electrode film removal section, 38: Second electrode film removing portion, 40: Connection electrode, 42: Package, 44: Bottom portion, 46: Frame wall portion, 48 ... Vent hole, 49 ... Seal portion, 50 ... Fixed electrode, 52 ... External terminal, 54 ... conductive adhesive, 56 ... ring, 58 ... lid, 60 ... through hole, 62 ... light transmissive member

Claims (3)

A quartz crystal resonator element including a base and a vibrating arm extending from the base;
An excitation electrode formed on the vibrating arm;
A connection electrode formed on the quartz crystal resonator element and electrically connected to the excitation electrode;
A package for accommodating the quartz crystal vibrating piece therein;
A fixed electrode formed on the inner surface of the package;
A conductive adhesive for electrically and mechanically joining the connection electrode and the fixed electrode;
Including
The connection electrode and the fixed electrode have a surface made of Au,
The conductive adhesive includes a binder containing a bismaleimide resin and a conductive filler dispersed in the binder, and the binder is configured by removing a polymer compound other than the bismaleimide resin. The crystal resonator according to claim 1,
The binder is a crystal resonator further including an additive made of a low molecular compound. A quartz crystal resonator element comprising a base and a vibrating arm extending from the base and having an excitation electrode formed on the vibration arm and electrically connected to the excitation electrode, and a fixed electrode on the inner surface Including inside the formed package, and electrically and mechanically joining the connection electrode and the fixed electrode with a conductive adhesive,
The connection electrode and the fixed electrode have a surface made of Au,
The conductive adhesive includes a binder containing a bismaleimide resin precursor and a conductive filler dispersed in the binder, and the binder is configured by excluding a polymer compound precursor other than the bismaleimide resin precursor. A method for manufacturing a crystal unit.