JP2015195593A - crystal oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crystal oscillator where a frequency characteristic of a vibrator can be easily measured irrespective of thickness of the vibrator, a wide variable width can be achieved, the crystal oscillator is hardly influenced by ESD, and cost reduction is enabled.SOLUTION: A crystal oscillator includes an IC chip juxtaposed on a bottom face of a package 5, a measurement substrate 7 and a crystal vibrator 1 supported by the measurement substrate 7. Connection electrodes 73 and 74 are formed on the measurement substrate 7, where the connection electrode includes a bonding pad portion and a connection portion. Wires 31 and 32 connect the connection electrodes of the IC chip 2 to the bonding pad portions of the connection electrodes 73 and 74. In an assembly method, the connection electrodes of the IC chip are directly bonded to an electrode of the crystal vibrator, thereby, parasitic capacitance can be reduced. A crystal vibration test performed before package mounting reduces a frequency adjustment width to be performed after mounting, thereby, parameter change of the crystal vibrator is reduced and variations in a variable characteristic are reduced.

Description

  The present invention relates to a crystal oscillator housed in a package.

An oscillator using a piezoelectric vibrator such as a crystal vibrator is used for a reference frequency generation source or a filter of communication equipment such as a mobile phone or electronic equipment such as a computer. For example, a crystal oscillator in which a crystal resonator is hermetically sealed together with an integrated circuit (IC chip) in a package is disposed at the bottom of a package body such as ceramic, the crystal resonator is accommodated on the crystal oscillator, and an opening is formed. It is hermetically sealed with a metal lid or the like.
FIG. 6 is a cross-sectional view of a conventional voltage controlled crystal oscillator.

  The surface-mounted oscillator shown in the figure contains an IC chip 102 and a crystal resonator 103 in a container body 101, and is covered with a cover 104 and sealed. The container body 101 is made of a laminated ceramic having a bottom wall 101a, an intermediate frame 101b, and an upper wall 101c, and has a concave shape with inner wall step portions on both ends. On the inner bottom surface of the container main body 101, for example, a first crystal terminal and a circuit terminal 105 serving as a power source, an output, an earth, and a standby terminal are provided.

The first crystal terminal among the circuit terminals 105 is connected to the second crystal terminal 106 on the inner wall step portion formed by the intermediate frame 101 via the wiring 112, and the other circuit terminals 105 other than this are connected via the wiring. It connects with the external terminal 107 of the outer bottom face which the bottom wall 101a of the container main body 101 forms. The IC chip 102 integrates at least an oscillation circuit, and an IC terminal (not shown) on the circuit function surface is flip-chip bonded to the inner bottom surface of the recess by ultrasonic thermocompression using the bump 108. The quartz crystal vibrator 103 has excitation electrodes on both main surfaces, and both ends of the extended end portion of the extraction electrode are fixed to the inner wall step on one end side of the container body 101 by the conductive adhesive 111. The other end portion of the crystal unit 103 is positioned above the inner wall step on the other end side to reduce the amplitude fluctuation width at the time of impact or the like.

  A conventional crystal oscillator assembly method is described in FIG. First, a package in which the multilayer wiring and connection electrodes shown in FIG. 6 are formed is prepared. Each wiring of the multilayer wiring is formed by electrolytic plating on the laminated insulating layer. The electrode 112 a for performing electrolytic plating is formed as a part of the wiring 112 constituting the multilayer wiring, and its end is exposed on the side surface of the package 101. After the wiring is formed, the electrode 102a for electroplating is not necessary, but is used as it is after the product is shipped. Next, the IC chip 102 is mounted on the package 101, and then the crystal resonator 102 is mounted and sealed. After that, a product test is performed, non-defective products are shipped, and defective products are discarded.

Patent Document 1, Patent Document 2 and Patent Document 3 are examples of conventional oscillators.
Patent Document 1 discloses a piezoelectric oscillator having a structure in which a package main body is hermetically sealed with a metal lid in a state in which a crystal resonator element and a circuit component that are not hermetically sealed are housed in the package main body. There has been disclosed a piezoelectric oscillator capable of performing an annealing process, a cleaning process, and a metal film deposition process for fine frequency adjustment on a crystal resonator element while reducing the height and cost. The piezoelectric oscillator includes a package body having a concave portion on the upper surface, a circuit component mounted on a wiring pattern on the inner bottom surface of the concave portion, and an inner portion mounted on a step formed at a position higher than the inner bottom surface of the concave portion. A package, a piezoelectric vibrator mounted in a recessed portion on the inner package, and a metal lid fixed to the upper surface of the outer frame of the package body and sealing the recessed portion.

Patent Document 2 discloses a surface mount oscillator that eliminates waste of a surface mount container, improves productivity, and has good impact resistance, and a manufacturing method thereof. This oscillator includes a holder-integrated crystal piece having a characteristic detection terminal by electrically and mechanically connecting the outer peripheral portion of a crystal piece with a pair of extraction electrodes extending to one end side, and the holder-integrated crystal piece And a container body for surface mounting having a step portion on the other end side, and the other end portion of the holder-integrated crystal piece faces the step portion of the container body. It has become. In addition, the manufacturing method measures the vibration characteristics of the holder-integrated crystal piece, and then faces the other end of the holder-integrated crystal piece to the stepped portion of the container body, so that the holder-integrated crystal piece Is housed in the container body and the cover is sealed.

  Patent Document 3 discloses a surface-mount crystal oscillator in which an IC chip, a crystal piece, and a circuit element by wire bonding are housed in a concave container body made of a laminated ceramic, and the container body is along the longitudinal direction. While having a pair of inner wall stepped portions opposed to both sides, the pair of inner wall stepped portions have an upper stepped portion and a lower stepped portion having different heights along the longitudinal direction, and the one of the pair of inner wall stepped portions One end of the crystal piece in the length direction is held on at least one of the upper stage portions, and the length direction of the crystal piece is defined as the short direction of the container body, and the container main body includes at least the lower surface of the crystal piece. The circuit element is disposed on the inner bottom surface, and the IC chip is disposed on the inner bottom surface of the container body between the lower step portions of the pair of inner wall step portions. Before Crystal oscillator connected to the lower portion is disclosed. A crystal piece and an IC chip are juxtaposed, and the crystal piece and the circuit element are arranged vertically. Therefore, the planar outer shape is made smaller than the case where three parties (crystal piece, IC chip, circuit element) are arranged in parallel. Further, since the circuit element is arranged on the lower surface of the crystal piece, the height dimension can be made smaller than the case where the IC chip formed by wire bonding is arranged on the lower surface. And since the length direction of a crystal piece is made into the transversal direction of a container main body, the longitudinal direction of a container main body is made small. In this oscillator, unlike the oscillators described in Patent Document 1 and Patent Document 2, the IC chip and the crystal piece are arranged in parallel.

JP 2000-134058 A JP 2001-102868 A Japanese Patent No. 4444740

Conventional piezoelectric oscillators such as quartz, including those described in Patent Document 1 or Patent Document 2, are mounted with an IC chip, and thereafter, after the crystal resonator is mounted, characteristics are confirmed (product test). Therefore, when the oscillator characteristic is poor, not only the vibrator but also the package has to be discarded. In addition, measurement with a single vibrator is difficult to implement because problems such as cracking occur because the vibrator itself is thin. Furthermore, as shown in FIG. 6, in the crystal oscillator, wiring such as multilayer wiring is routed between a terminal that electrically connects an external circuit and the inside, and a crystal resonator or an IC chip. ing. As described in Patent Document 3, the IC chip and the crystal piece are electrically connected by wiring.
Such wiring increases the parasitic capacitance, which makes it difficult for the oscillator to take a wide variable width. Further, in FIG. 6, since the plating electrode used when forming the multilayer wiring is exposed to the outside of the package, the influence of the ESD on the internal circuit is large.
The present invention has been made under such circumstances. The frequency characteristics of the vibrator can be easily measured regardless of the thickness of the vibrator, a wide variable width can be realized, and it is affected by ESD. To provide a crystal oscillator that can reduce cost.

The crystal oscillator according to the present invention includes a package, an IC chip on which an oscillation circuit fixed to the package is formed, a measurement substrate juxtaposed with the IC chip in the package, and supported by and mounted on the measurement substrate. The measurement substrate has one surface bonded to the package and the other surface formed with a pair of connection electrodes. The connection electrodes of the measurement substrate are bonded to each other, respectively. A bonding pad portion to which a wire is bonded and a connection portion to which one of the electrodes of the crystal resonator is connected; and the bonding wire connects the connection electrode of the IC chip and the bonding pad portion, The measurement substrate includes the water crystal in the state before being bonded to the package and the state before being bonded to the package together with the state where the crystal resonator is mounted. To enable frequency adjustment of the vibrator, it is characterized in that the mounting surface to expose said crystal oscillator is open.
The bonding pad portion and the connection portion constituting the connection electrode of the measurement substrate have a portion facing each other at a predetermined interval, and the bonding pad portion and the connection portion are portions of the portions facing each other. You may make it connect only in one part.

  In the crystal oscillator according to the present invention, since the crystal resonator is supported by the measurement substrate, characteristics such as the frequency of the crystal resonator can be easily measured regardless of the thickness of the resonator. In addition, since the connection electrode (pad) of the IC chip and the electrode of the crystal resonator are directly bonded, the parasitic capacitance can be reduced, so that a wide variable width can be realized. Further, since unnecessary metal is not exposed on the side of the package, the influence of ESD is reduced.

2 is a cross-sectional view and a plan view of a crystal oscillator in a state where a lid according to Embodiment 1 is removed. FIG. FIG. 2 is a process cross-sectional view illustrating a method for assembling the crystal oscillator of FIG. 1. FIG. 2 is a flowchart for explaining an assembly method until the crystal oscillator of FIG. 1 is shipped. Sectional drawing explaining the process of attaching a crystal oscillator to the measurement board | substrate of the crystal oscillator which concerns on Example 2. FIG. Sectional drawing explaining the process of attaching a crystal oscillator to the measurement board | substrate of the crystal oscillator which concerns on Example 2. FIG. Sectional drawing of the conventional crystal oscillator. The flowchart explaining the assembly method until product shipment of the conventional crystal oscillator.

  Hereinafter, embodiments of the invention will be described with reference to examples.

The first embodiment will be described with reference to FIGS.
As shown in FIG. 1, the crystal oscillator includes a package 5 made of ceramic, an IC chip 2 in which an oscillation circuit fixed to the bottom surface of the package 5 is formed, and a measurement in which the IC chip 2 is placed on the bottom surface of the package 5. And a crystal resonator 1 supported and mounted on the measurement substrate 7. One surface of the measurement substrate 7 is bonded to the bottom surface of the package 5, and a pair of connection electrodes 73 and 74 are formed on the other surface. The connection electrodes 73 and 74 of the measurement substrate 7 include a bonding pad portion to which the bonding wires 31 and 32 are bonded and a connection portion to which the electrodes 11 and 12 of the crystal resonator 1 are respectively connected. The bonding wire 31 connects the connection electrode 21 of the IC chip 2 and the bonding pad portion of the connection electrode 73 of the measurement substrate 7, and the bonding wire 32 connects the connection electrode 22 of the IC chip 2 and the connection electrode of the measurement substrate 7. 74 bonding pad portions are connected. The opening of the package 5 is covered with, for example, a metal lid 6 and hermetically sealed using a seam ring or the like. A plurality of oscillator terminals 8 and 9 are formed on the back surface of the package 5. The plurality of terminals 8 and 9 are electrically connected to the IC chip 2 and the connection electrodes 73 and 74 of the measurement substrate 7 through contacts (not shown) formed on the back surface of the package 5.

The crystal unit 1 includes a main surface electrode 11 and a back surface electrode 12. The main surface electrode 11 has a main portion formed on the main surface, and a part of the tip portion extends beyond the main surface and is formed on the back surface via the side surface. It is formed. The back surface portion of the tip portion becomes a connection portion. The main part of the back electrode 12 is formed on the back surface, and a part of the tip part is formed on the main surface through the side surface beyond the back surface. This main part becomes a connection part. The back surface portion of the main surface electrode 11 is bonded to the connection electrode 73 of the measurement substrate 7 with a conductive adhesive, and the back surface portion of the back electrode 12 is bonded to the connection electrode 74 of the measurement substrate 7 with a conductive adhesive. ing.
In this embodiment, since the crystal unit is supported by the measurement substrate, the characteristics such as the frequency of the crystal unit can be easily measured regardless of the thickness of the unit. Can do. Further, since the connection electrode of the IC chip and the electrode of the crystal resonator are directly bonded, it is not necessary to interpose multilayer wiring, and the parasitic capacitance can be reduced. Therefore, a variable width with a wide frequency can be realized. Further, since the multilayer wiring is not used, there is no plating electrode for forming the multilayer wiring, so that unnecessary metal is not exposed on the side surface of the package, and therefore, the influence of ESD is reduced.

Next, a method for assembling a crystal oscillator will be described with reference to FIGS.
(1) First, the electrodes 11 and 12 of the crystal unit 1 are bonded to the connection electrodes 73 and 74 of the measurement substrate 7 using the conductive adhesive 4 respectively. Next, the crystal resonator 1 attached to the measurement substrate 7 is tested (frequency measurement) to select non-defective products. A defective product that does not have a predetermined frequency value is discarded or frequency-adjusted to be a non-defective product. (2) The IC chip 2 is tested to prepare a non-defective product having predetermined characteristics. (3) The measurement substrate 7 to which the crystal unit 1 is attached is bonded to the package 5 (FIG. 2A). Further, the IC chip 2 is bonded to the package 5 (FIG. 2B). Next, the connection electrode of the IC chip 2 and the connection electrode (74) of the measurement substrate 7 are connected using the bonding wire (32) (FIG. 2 (c)). Next, frequency adjustment is performed so as to obtain a frequency required for the crystal oscillator (FIG. 2D). Next, the package 5 is sealed using the metal lid 6 (FIG. 2E). Next, (4) a product test is performed to select non-defective products. After that, (5) Ship good products.
The crystal oscillator assembly method in this embodiment measures the characteristics of the crystal unit before mounting the package, so there is no need to discard the package on which the defective crystal unit is mounted as in the past, saving resources. It contributes and leads to cost reduction, and variation in variable characteristics can be reduced.

Next, Embodiment 2 will be described with reference to FIG.
This embodiment is characterized by the structure of the measurement substrate. The measurement substrate and the crystal resonator are joined before mounting the package (see FIG. 3). The IC chip and the measurement substrate are bonded to each other after being mounted on the package (see FIG. 2C).
One surface of the measurement substrate 27 is bonded to the bottom surface of the package, and a pair of connection electrodes 25 and 26 are formed on the other surface. The connection electrode 25 includes a connection portion 251 to which one of the electrodes of the crystal resonator is connected, a bonding pad portion 252 to which a bonding wire is connected, and a coupling portion 253 that couples both portions. It comprises a connection part 261 to which the other one of the child electrodes is connected, a bonding pad part 262 to which a bonding wire is connected, and a joint part 263 that joins both parts. The connection portions 251 and 261 constituting the connection electrodes 25 and 26 and the bonding pad portions 252 and 262 respectively have portions facing each other at a predetermined interval, and the bonding pad portion and the connection portion are portions of the portions facing each other. Connection is made only at a part (the coupling portions 253 and 263) (FIG. 4A).

  The crystal unit 28 includes a main surface electrode 281 and a back surface electrode 282. The main surface electrode 281 has a main portion formed on the main surface, and a portion of the tip portion extends beyond the main surface and passes through the side surface to the back surface. It is formed. The back surface portion of the tip portion becomes a connection portion with the connection electrode of the measurement substrate. The main part of the back electrode 282 is formed on the back surface, and a part of the tip part is formed on the main surface through the side surface beyond the back surface. This main portion becomes a connection portion with the connection electrode of the measurement substrate (FIG. 4C).

Next, an assembly process for bonding the crystal resonator to the measurement substrate will be described.
First, the connection electrodes 25 and 26 are formed on the main surface of the measurement substrate 27 (FIG. 4A). Next, the conductive adhesives 23 and 24 are applied to the connection portions 251 and 261 of the connection electrodes 25 and 26, and the main surface electrode 281 and the back surface electrode 282 are mounted thereon, and the crystal resonator 28, the measurement substrate 27, Are connected (FIG. 4B). In a subsequent process, bonding wires connected to the IC chip are bonded to the bonding pad portions 252 and 262 of the connection electrodes 25 and 26. In the previous process, a crystal resonator is tested. In the test, the probe is applied to the bonding pad portions 252 and 262 to adjust the frequency of the crystal resonator (see FIG. 3).
As described above, in this embodiment, since the connection electrode of the measurement substrate is configured so that the connection portion and the bonding pad portion face each other at a predetermined interval, it is possible to prevent the conductive adhesive from spreading to the bonding pad portion. This portion can be kept wide and bonding and testing can be easily performed. Moreover, the same effect as Example 1 can be recognized. This embodiment can be applied to the crystal oscillator of the first embodiment.

Next, Example 3 will be described with reference to FIG.
A connection electrode is formed on the main surface of the measurement substrate 35, a conductive adhesive 33 is applied to the connection portion of the connection electrode, and the electrode of the crystal unit 30 is placed on the connection surface of the measurement substrate 35. At this time, the protrusions 34 are formed on the main surface of the measurement substrate 35 located away from the conductive adhesive 33. The material may be the same as or different from the measurement substrate 35.
The protrusion 34 is used as a support when the crystal resonator 30 is bonded. It can also be removed after bonding. Moreover, the same effect as Example 1 can be recognized. This embodiment can be applied to the crystal oscillators of Embodiments 1 and 2.

DESCRIPTION OF SYMBOLS 1, 28, 30 ... Crystal oscillator 2 ... IC chip 4, 23, 24, 33 ... Conductive adhesive 5 ... Package 6 ... Metal lid 7, 27, 35 ... Measurement substrate 8, 9 ... Terminal 11, 12, 281, 282 ... Crystal resonator electrode 21, 22 ... IC chip connection electrode 25, 26, 73, 74, ... Measurement substrate Connection electrodes 31, 32 ... Bonding wires 251, 261 ... Connection portions of connection electrodes 252, 262 ... Bonding portions of connection electrodes 253, 263 ... Connection portions of connection electrodes

Claims (2)

A package, an IC chip on which an oscillation circuit fixed to the package is formed, a measurement substrate disposed in parallel with the IC chip in the package, and a crystal resonator supported and mounted on the measurement substrate The measurement substrate includes a bonding pad to which one surface is bonded to the package and a pair of connection electrodes are formed on the other surface, and each of the connection electrodes of the measurement substrate is bonded to a bonding wire. And a connection part to which one of the electrodes of the crystal resonator is connected, the bonding wire connects the connection electrode of the IC chip and the bonding pad part, and the measurement substrate is the crystal In the state before being bonded to the package together with the state in which the resonator is mounted, and the state in which the resonator is bonded to the package, frequency adjustment of the crystal resonator is performed. To the ability crystal oscillator whose mounting surface to expose said crystal oscillator is characterized in that it is open. The bonding pad portion and the connection portion constituting the connection electrode of the measurement substrate have a portion facing each other at a predetermined interval, and the bonding pad portion and the connection portion are portions of the portions facing each other. The crystal oscillator according to claim 1, wherein the crystal oscillator is connected only partially.

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