JP2013207549A - Piezoelectric device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric device which reduces a temperature difference between a temperature of a crystal element and a temperature set on the basis of temperature information obtained by a temperature-sensitive electrode and properly conducts temperature correction at an oscillatory frequency.SOLUTION: The piezoelectric device includes: a package 110 having a recessed part K formed by a substrate part 110a and a frame part 110b provided on the substrate part 110a; a pair of electrode pads 111 provided on the substrate part 110a in the recessed part K; a piezoelectric element 120 mounted on the pair of electrode pads 111; a pair of via conductors provided in the substrate part 110a and connected with the pair of electrode pads 111; and a temperature-sensitive electrode 140 that is provided in the substrate part 110a and is provided between the pair of via conductors in a plane view so as to be spaced away from the pair of via conductors.

Description

  The present invention relates to a piezoelectric device used in electronic equipment and the like.

  A conventional piezoelectric device uses a piezoelectric effect of a piezoelectric element to generate a specific frequency. Piezoelectric elements have the property that the frequency to be generated varies depending on temperature conditions, and development of a technique for sensing the temperature of the piezoelectric element and adjusting the frequency of the piezoelectric element is underway. Currently, a piezoelectric device including a piezoelectric element and a temperature-sensitive element that senses the temperature of the piezoelectric element in a package has been proposed (see, for example, Patent Document 1 below). The package is set in a vacuum state.

JP-A-9-98023

  In the above-described piezoelectric device, since the inside of the recess is maintained in a vacuum state, it is difficult for the temperature-sensitive element to accurately detect the temperature of the piezoelectric element, and the actual temperature of the piezoelectric element and the temperature information obtained by the temperature-sensitive element are used. There may be a large temperature difference from the base temperature. Therefore, the above-described piezoelectric device has a problem that even if temperature correction is performed at the oscillation frequency of the piezoelectric element, there is a possibility that appropriate correction cannot be performed.

  The present invention has been made in view of the above problems, and by correcting the temperature difference at the oscillation frequency of the piezoelectric element by reducing the temperature difference between the actual temperature of the piezoelectric element and the temperature based on the temperature information obtained by the temperature sensitive element. An object of the present invention is to provide a piezoelectric device capable of appropriately performing the above.

  A piezoelectric device according to one aspect of the present invention includes a package having a recess formed by a substrate portion and a frame portion provided on the substrate portion, and a pair of electrode pads provided on the substrate portion in the recess. A piezoelectric element mounted on the pair of electrode pads, a pair of via conductors provided in the substrate portion and connected to the pair of electrode pads, and provided in the substrate portion between the pair of via conductors in plan view. A pair of via conductors and a temperature-sensitive electrode provided with a space therebetween.

  The piezoelectric device according to one aspect of the present invention can reduce the difference between the actual temperature of the piezoelectric element and the temperature based on the temperature information obtained by the temperature sensing electrode, and the accuracy of temperature compensation regarding the oscillation frequency of the piezoelectric element. Can be improved.

It is a disassembled perspective view which shows the piezoelectric device in embodiment of this invention. (A) is the longitudinal cross-sectional view in AA of the piezoelectric device shown by FIG. 1, (b) is the longitudinal cross-sectional view in BB of the piezoelectric device shown by FIG. It is a disassembled perspective view which shows each layer of the package which comprises the piezoelectric device in embodiment of this invention. (A) is the plane perspective view which looked at the package which comprises the piezoelectric device in embodiment of this invention from the upper surface, (b) is the plane which looked at the board | substrate part which comprises the piezoelectric device in embodiment of this invention from the upper surface. It is perspective drawing, (c) is the plane perspective view which looked at the inner layer of the board | substrate part which comprises the piezoelectric device in embodiment of this invention from the upper surface. (A) is the plane perspective view which looked at the board | substrate part which comprises the piezoelectric device in embodiment of this invention from the upper surface, (b) is the plane which looked at the package which comprises the piezoelectric device in embodiment of this invention from the lower surface. FIG.

  Hereinafter, the present embodiment will be described with reference to the drawings. A case where a crystal element is used as the piezoelectric element will be described.

  As shown in FIGS. 1 and 2, the piezoelectric device includes a package 110, a crystal element 120, and a lid 130. This piezoelectric device has a structure in which a crystal element 120 is mounted in a recess K formed in a package 110 and the recess K is hermetically sealed by a lid 130. In addition, a temperature-sensitive electrode 140 is provided inside the substrate portion 110 a of the package 110.

  As shown in FIGS. 1 and 2, the package 110 includes a substrate portion 110a and a frame portion 110b provided on the upper surface of the substrate portion 110a. A recess K is formed by the upper surface of the substrate portion 110a and the inner surface of the frame portion 110b.

  The substrate portion 110a functions as a support member for supporting the crystal element 120, and a pair of electrode pads 111 for bonding the crystal element 120 are provided on the upper surface. In addition, external connection electrode terminals G are provided at the four corners of the lower surface of the substrate portion 110a. The external connection electrode terminal G includes a pair of crystal element electrode terminals G1 and a pair of temperature information electrode terminals G2.

  The substrate part 110a is formed by laminating a plurality of insulating layers made of a ceramic material such as alumina ceramics or glass-ceramics. A pair of vias for electrically connecting the pair of electrode pads 111 on the top surface of the substrate portion 110a and the external connection electrode terminal G (crystal element electrode terminal G1) on the bottom surface are provided on and inside the substrate portion 110a. A conductor 113 is provided. Further, a crystal element wiring pattern 114 and a crystal element via conductor 115 are provided on the surface and inside of the substrate portion 110a. One of the plurality of insulating layers constituting the substrate portion 110a is provided with a temperature-sensitive electrode 140 between the pair of via conductors 113 and the pair of via conductors 113 in a plan view.

  The distance between the pair of via conductors 113 and the temperature sensitive electrode 140 is about 15 to 20 μm. By keeping this interval, the pair of via conductors 113 can be prevented from being short-circuited with the temperature-sensitive electrode 140. The heat applied to the crystal element 120 is transmitted in the order of the pair of conductive adhesives DS in contact with the connection electrode 123 of the crystal element 120, the pair of electrode pads 111, and the pair of via conductors 113. The temperature is transmitted to the temperature-sensitive electrode 140 at the shortest distance through the insulating layer on the same plane. The temperature of the crystal element 120 is hardly different from the temperature of the pair of electrode pads 111. Between the pair of via conductors 113 connected immediately below the pair of electrode pads 111, the temperature of the crystal element 120 is indirectly applied to the temperature-sensitive electrode 140 through a part of the insulating layer having excellent thermal conductivity. It is transmitted. Therefore, the actual temperature of the crystal element 120 and the temperature information obtained by the temperature-sensitive electrode 140 can be approximated.

  The temperature-sensitive electrode 140 has an electrical resistance that shows a significant change due to a temperature change, and the voltage is changed by the change in the resistance value. The temperature sensing electrode 140 can obtain temperature information from the converted voltage by converting the output resistance value into a voltage based on the relationship between the resistance value and the voltage and the relationship between the voltage and the temperature. it can. The temperature sensing electrode 140 outputs a resistance value output from a main IC (not shown) such as an electronic device by outputting a resistance value to the outside of the piezoelectric device via the temperature information electrode terminal G2. Temperature information can be obtained by converting the voltage. According to the temperature information of the crystal element 120 obtained in this way, a voltage for correcting the oscillation frequency of the crystal element 120 can be controlled by the main IC, and so-called temperature compensation can be performed.

  2 and 3, the temperature-sensitive electrode 140 is provided on one of the plurality of insulating layers, and between the pair of via conductors 113 in a plan view, The conductor 113 is spaced from the conductor 113. The temperature sensing electrode 140 has a strip shape or a line shape, and a first temperature sensing via conductor 116 and a second temperature sensing conductor via conductor 118 are provided at both ends. The temperature-sensitive electrode 140 is made of, for example, a metal material containing any of platinum, silver, palladium, chromium, and titanium, or a metal oxide of molybdenum or manganese. It is formed on one of the constituent insulating layers.

  For example, when the substrate portion 110a is made of glass-ceramics, the temperature-sensitive electrode 140 is integrally formed with the substrate portion 110a by firing. Since the temperature-sensitive electrode 140 is formed integrally with the package 110, for example, compared to a case where a pre-manufactured temperature-sensitive element is mounted on the package with a conductive adhesive, there is no need to generate from the conductive adhesive. The amount of gas is reduced. Therefore, by using the temperature-sensitive electrode 140, the possibility that the electrode portion of the crystal element 120 is oxidized by unnecessary gas can be reduced, and the oscillation frequency of the crystal element 120 is maintained at a desired value over a long period of time. Can be easier.

  Further, the temperature sensing electrode 140 formed inside the substrate portion 110a and the temperature information electrode terminal G2 formed on the lower surface of the substrate portion 110a are formed on the package 110 as shown in FIGS. The temperature sensing wiring pattern 117, the first temperature sensing via conductor 116, and the second temperature sensing via conductor 119 formed inside the substrate portion 110 a are connected. That is, the temperature sensing electrode 140 is connected to one end of the temperature sensing wiring pattern 117 through the first temperature sensing via conductor 116 as shown in FIGS. The other end of the temperature sensing wiring pattern 117 is connected to the temperature information electrode terminal G2 via the second temperature sensing via conductor 119, as shown in FIGS. Therefore, the temperature-sensitive electrode 140 is electrically connected to the temperature information electrode terminal G2.

  The frame portion 110b is for forming the recess K on the substrate portion 110a. The frame part 110b is made of a ceramic material such as alumina ceramics or glass-ceramics, and is formed integrally with the substrate part 110a. A sealing conductor pattern 112 is provided on the upper surface of the frame portion 110b.

  The sealing conductor pattern 112 plays a role of improving the wettability of the sealing member 131 when it is bonded to the lid 130 via the sealing member 131. Further, as shown in FIG. 2B, the sealing conductor pattern 112 is connected to the temperature information electrode terminal G2 through the lid via conductor 118 and the second temperature-sensitive via conductor 119. ing. At least one temperature information electrode terminal G2 serves as a ground terminal by being connected to a mounting pad connected to a ground on an external mounting substrate. Therefore, the lid 130 joined to the sealing conductor pattern 112 is connected to the ground, and the shielding performance in the recess K by the lid 130 is improved.

  Here, a method for manufacturing the package 110 will be described. When the substrate part 110a and the frame part 110b are made of alumina ceramics, first, a plurality of ceramic green sheets obtained by adding and mixing an appropriate organic solvent or the like to a predetermined ceramic material powder is prepared. Next, a predetermined conductive paste is applied to the surface of the ceramic green sheet or the through-hole previously punched by punching the ceramic green sheet by screen printing or the like. Further, these green sheets are laminated and press-molded and fired at a high temperature. Finally, it is manufactured by applying nickel plating or gold plating to a predetermined portion of the conductor pattern, specifically, a portion to be the pair of electrode pads 111 and the external connection electrode terminal G. Moreover, the conductor paste is comprised from the sintered compact etc. of metal powders, such as tungsten, molybdenum, copper, silver, or silver palladium, for example.

  The crystal element 120 plays a role of oscillating a reference signal of an electronic device or the like by stable mechanical vibration and a piezoelectric effect. As shown in FIG. 2, the crystal element 120 has a structure in which an excitation electrode 122, a connection electrode 123, and a lead electrode 124 are attached to the upper and lower surfaces of a rectangular crystal base plate 121. Have. The crystal element 120 is bonded to the pair of electrode pads 111 of the substrate part 110a of the package 110 via the conductive adhesive DS. In the present embodiment, the crystal element 120 is mounted on the substrate 110a of the package 110 in a one-piece holding structure in which one end side in the long side direction of the crystal element 120 is a fixed end portion and the other end side in the long side direction is a tip end portion. It is fixed to.

  The pair of electrode pads 111 is connected to a pair of crystal element electrode terminals G1 via a pair of via conductors 113, a crystal element wiring pattern 114, and a crystal element via conductor 115 formed inside the substrate portion 110a of the package 110. Electrically connected. That is, the pair of electrode pads 111 is connected to one end of the crystal element wiring pattern 114 via the pair of via conductors 113. The other end of the crystal element wiring pattern 114 is connected to the crystal element electrode terminal G <b> 1 via the crystal element via conductor 115. Therefore, the pair of electrode pads 111 is electrically connected to the pair of crystal element electrode terminals G1.

  Here, the operation of the crystal element 120 will be described. When an alternating voltage from the outside is applied to the crystal element plate 121 from the connection electrode 123 via the extraction electrode 124 and the excitation electrode 122, the crystal element 120 is excited in a predetermined vibration mode and frequency. Is supposed to wake up.

  Here, a manufacturing method of the crystal element 120 will be described. First, a quartz base plate 121 is obtained by cutting an artificial crystalline lens at a predetermined cut angle and performing external processing. Then, the crystal element 120 is formed by forming the excitation electrode 122, the connection electrode 123, and the extraction electrode 124 by depositing a metal film on both main surfaces of the crystal base plate 121 by a conventionally known sputtering technique or the like. Produced.

  A method for bonding the crystal element 120 to the package 110 will be described. First, the conductive adhesive DS is applied onto the pair of electrode pads 111 by, for example, a dispenser. Then, the crystal element 120 is conveyed onto the conductive adhesive DS in the recess K of the package 110 fixed with a jig. Further, the crystal element 120 is placed on the conductive adhesive DS. The crystal element 120 is bonded to the package 110 by heating and curing the conductive adhesive DS.

  The conductive adhesive DS contains a conductive powder as a conductive filler in a binder. As the conductive powder, one containing aluminum, molybdenum, tungsten, platinum, palladium, silver, titanium, nickel, nickel iron, or a combination thereof is used. As the binder, for example, a silicone resin, an epoxy resin, a polyimide resin, a bismaleimide resin, or the like is used.

  The lid 130 is made of an alloy containing at least one of iron, nickel, and cobalt, for example. Such a lid 130 is for hermetically sealing the recess K in a vacuum state or the recess K filled with nitrogen gas or the like. Specifically, the lid 130 is placed on the frame 110b of the package 110 in a predetermined atmosphere, and the sealing conductor pattern 112 of the frame 110b and the sealing member 131 of the lid 130 are welded. Thus, the sealing member 131 is joined to the frame part 110b by applying a predetermined current to the lid 130 and performing seam welding.

  The sealing member 131 is provided at a position of the lid 130 facing the sealing conductor pattern 112 provided on the upper surface of the frame 110 b of the package 110. The sealing member 131 is provided by, for example, silver solder or gold tin.

  The piezoelectric device according to the present embodiment is provided in the substrate portion 110a and a pair of via conductors 113 connected to the pair of electrode pads 111 and the pair of via conductors 113 provided in the substrate portion 110a and viewed in plan. A pair of via conductors 113 and a temperature-sensitive electrode 140 provided with a space therebetween are provided. The heat of the crystal element 120 is transmitted from the pair of electrode pads 111 to the temperature sensing electrode 140 from the insulating layer on the same plane constituting the substrate portion 110a through the pair of via conductors 113. Therefore, the difference between the actual temperature of the crystal element 120 and the temperature based on the temperature information obtained by the temperature sensing electrode 140 can be reduced, and the accuracy of temperature compensation regarding the oscillation frequency of the crystal element 120 can be improved. .

  The piezoelectric device according to the present embodiment includes a lid 130 for hermetically sealing the recess K, and one end of the temperature-sensitive electrode 140 is electrically connected to the lid 130, thereby at least one temperature. By connecting the information electrode terminal G2 and the mounting pad to which the ground on the mounting substrate is connected, it plays the role of a ground terminal. Therefore, one end of the temperature sensing electrode 140 is also connected to the ground, and the resistance value can be stably output. Therefore, the actual temperature of the crystal element 120 and the temperature information obtained by the temperature sensing electrode 140 are obtained. The difference from the temperature based on can be reduced.

  Assuming that the lid 130 and one temperature information electrode terminal G2 are not electrically connected to the ground, the ground such as a housing (not shown) approaches the lid 130 from the outside. A stray capacitance is generated between 120 excitation electrodes 122 and a housing (not shown). Therefore, the oscillation frequency of the crystal element 120 cannot be output stably. Therefore, since the lid 130 and one temperature information electrode terminal G2 are electrically connected to the ground, even if the ground such as a housing (not shown) approaches the lid 130 from the outside, the crystal element Since no stray capacitance is generated between the excitation electrode 122 of 120 and the housing (not shown), the oscillation frequency of the crystal element can be stably output.

  In addition, it is not limited to this embodiment, A various change, improvement, etc. are possible in the range which does not deviate from the summary of this invention. In the above embodiment, the case where the frame portion 110b is integrally formed of a ceramic material as in the case of the substrate portion 110a has been described. However, the frame portion 110b may be made of metal. In this case, the frame portion is bonded to the conductor film of the substrate portion via a brazing material such as silver brazing.

  In the above embodiment, the case where the crystal element for AT is used as the crystal element has been described, but a tuning fork type bending having a base and two flat plate-shaped vibrating arms extending in the same direction from the side surface of the base. A crystal element may be used.

DESCRIPTION OF SYMBOLS 110 ... Package 110a ... Substrate part 110b ... Frame part 111 ... Piezoelectric vibration element mounting pad 113 ... Pair of via conductors 120 ... Piezoelectric element 121 ... Crystal element plate 122 ...・ Excitation electrode 123... Connection electrode 124... Extraction electrode 130 .. Lid 140 .. Temperature sensing electrode K .. Recessed DS DS. Conductive adhesive G. Electrode terminal G1... Crystal element electrode terminal G2... Temperature information electrode terminal

Claims (2)

A package having a recess formed by a substrate portion and a frame portion provided on the substrate portion;
A pair of electrode pads provided on the substrate portion in the recess;
A piezoelectric element mounted on the pair of electrode pads;
A pair of via conductors provided in the substrate portion and connected to the pair of electrode pads;
A temperature sensitive electrode provided in the substrate portion and provided between the pair of via conductors in a plan view and spaced from the pair of via conductors. The piezoelectric device according to claim 1,
A lid provided on the frame so as to hermetically seal the recess,
One end of the temperature sensing electrode is electrically connected to the lid body.

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