JP2007201616A - Surface mount piezoelectric oscillator, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a package plane area in a surface mount piezoelectric oscillator having an externally mounted IC component, constituted of a bare chip, to a piezoelectric vibrator package, by making resin coating of an IC component with an underfill unnecessary, so as to reduce the overall size. <P>SOLUTION: The piezoelectric oscillator includes a piezoelectric vibrator 2 having an insulating substrate 3 which includes an element mounting pad 4 electrically connected to each excitation electrode of a piezoelectric vibrator 2 on the upper face, and also an IC component mounting pad 5 on the bottom, a piezoelectric vibration device mounted on the element mounting pad, and a lid member 8 for air-tight sealing the above piezoelectric vibration device; an IC component 11 having an electrode electrically connected to the IC component mounting pad and constituting an oscillation circuit; and a flexible substrate 20 being adhered to at least a portion of an external face of the IC component, and also having a mounting terminal mounted on the bottom face in an exposed manner. The flexible substrate electrically conducts through the IC component mounting pad, the electrode of the IC component, and the mounting terminal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement of a surface mount type piezoelectric oscillator in which an IC component is incorporated on the outer surface of a piezoelectric vibrator package, and in particular, by reducing the package plane area and reducing the overall shape by eliminating the need for resin coating of the IC component with an underfill. The present invention relates to a surface-mount piezoelectric oscillator that can be miniaturized and a manufacturing method thereof.

In the mobile communications market, an increasing number of manufacturers are promoting modularization of parts groups for each function, taking into account the mounting properties, maintenance and handling characteristics of various electrical components, and the commonality of parts between devices. . Further, along with modularization, there is a strong demand for downsizing and cost reduction.
In particular, there is an increasing tendency toward modularization of circuit components that have established functions and hardware configurations, such as a reference oscillation circuit, a PLL circuit, and a synthesizer circuit, and that require high stability and high performance. Furthermore, there is an advantage that a shield structure can be easily established by packaging these component groups as modules.

Examples of surface mount IC components constructed by modularizing and packaging a plurality of related components include piezoelectric vibrators, piezoelectric oscillators, SAW devices, etc., but these functions are maintained at a high level. However, in order to further reduce the size, for example, a two-story structure module as shown in FIG. 7 is employed.
That is, FIG. 7 is a longitudinal sectional view showing a conventional configuration of a surface mount type piezoelectric oscillator (crystal oscillator) as a two-story structure type (H type) module.
This piezoelectric oscillator has a configuration in which a piezoelectric vibration element 110 and an IC component 115 are mounted in recesses 102 and 103 provided on the upper surface and the lower surface of the package 100, respectively.

The package 100 of this piezoelectric oscillator has an insulating container 101 having a substantially H-shaped longitudinal section having recesses 102 and 103 on the upper surface and the lower surface, and four sides of the rectangular annular outer bottom surface of the insulating container, or two facing each other. Two mounting terminals 105 disposed on the bottom surface of each outer wall 114 projecting along the side, and a recess on the upper surface side for electrically connecting each mounting terminal 105 and each excitation electrode of the piezoelectric vibration element 110. Two upper surface side internal pads 102a provided in 102, an oscillation circuit (amplification circuit for amplifying an excitation signal of the piezoelectric vibration element for oscillation), a temperature compensation circuit (to compensate the frequency-temperature characteristics of the piezoelectric vibration element) A lower surface side internal pad 103a disposed on the ceiling surface of the lower surface side recess 103 for mounting an IC component 115 having an integrated circuit such as the above-described circuit), each mounting terminal 105, and the upper surface side internal pad 102a. The conductor 106 to conduct between the side inner pad 103a, and a. The piezoelectric oscillator connects and fixes the piezoelectric vibration element 110 to the upper surface side internal pad 102a of the package 100 and seals the upper surface side recess 102 with the metal lid 120, and connects and fixes the IC component 115 to the lower surface side internal pad 103a. It has the structure which did. Further, in order to protect the IC component 115 which is a bare chip, the underfill 121 is filled in the lower surface side recess 103 (Patent Document 1).
When this piezoelectric oscillator is mounted on the mother printed board, soldering is performed using mounting terminals 105 provided on the bottom surface of each outer wall 114.

  By the way, as the demand for miniaturization of piezoelectric oscillators has been increasing year by year, one of the factors hindering miniaturization of the H-type surface-mount piezoelectric oscillator is an underfill in the lower surface side recess 103. The presence of space reserved for filling. That is, even if the size of the piezoelectric vibrator can be reduced and a small-sized IC component can be prepared to match the area of the piezoelectric vibrator, the outer wall 114 is formed to form the lower surface side recess, and the lower surface Since it is necessary to secure a gap for filling the underfill between the inner wall of the side recess and the IC component, there has been a limit to downsizing the entire oscillator.

Next, in Patent Document 2, an IC chip in which an electrode is directly formed on a semiconductor substrate such as silicon containing an oscillation circuit is flip-chip mounted directly on a crystal resonator package, or a mounting electrode formed on the IC chip is printed. A piezoelectric oscillator that is solder-connected on a substrate is disclosed.
However, when an electrode is formed on the bare chip surface of a semiconductor substrate such as a silicon substrate, the support strength of the electrode is not sufficient, and it is assumed that the electrode peels off from the substrate surface.
Recently, a surface mount type piezoelectric oscillator in which an IC component unit in which an IC component is coated and integrated with a mold resin is directly attached to a piezoelectric vibrator package has been proposed. In order to manufacture this IC component unit, Since a mold for resin molding is required, there is a problem that the initial investment amount increases. In particular, in the current situation where the cost reduction of piezoelectric devices continues chronically, an increase in manufacturing cost becomes a major bottleneck in product development and becomes a major obstacle to implementation.
JP 2002-329839 A JP 2004-228895 A

As described above, in the conventional H-type package disclosed in Patent Document 1, even if an attempt is made to reduce the IC component mounting space in the recess at the bottom of the package by downsizing the piezoelectric vibrator package, the IC component is covered. Since there was a need to secure a space for filling the underfill to be provided on the bottom surface side of the piezoelectric vibrator, there was a limit to miniaturization.
On the other hand, in a configuration in which a semiconductor substrate in which electrodes are directly formed on the outer surface as in the invention of Patent Document 2 is flip-chip connected directly to a piezoelectric vibrator package or mounted on a printed circuit board using electrodes of the semiconductor substrate, Since the connection strength between the substrate and the electrode is insufficient, a connection failure is likely to occur, and as a result, there is a concern that the operation may be disabled.
In addition, an oscillator in which an IC component unit in which an IC component is covered and integrated with a mold resin is directly attached to a piezoelectric vibrator package has a problem that an initial investment amount increases.
The present invention has been made in view of the above, and in a surface mount piezoelectric oscillator in which an IC component made of a bare chip is externally attached to a piezoelectric vibrator package, it is not necessary to coat the IC component with a resin by underfill. The purpose of this is to reduce the package flat area and reduce the overall shape.

  In order to achieve the above object, a surface-mounted piezoelectric oscillator according to the present invention has an element mounting pad electrically connected to each excitation electrode of a piezoelectric vibration element on an upper surface and an insulating part having an IC component mounting pad on the bottom. A substrate, a piezoelectric vibration element mounted on the element mounting pad, a piezoelectric vibrator including a lid member for hermetically sealing the piezoelectric vibration element, and an electrode electrically connected to the IC component mounting pad And an IC component that constitutes the oscillation circuit, and a flexible substrate that is in close contact with at least a part of the outer surface of the IC component and has a mounting terminal exposed on the bottom surface, the IC component mounting pad and the electrode of the IC component And the mounting terminal are electrically connected by the flexible substrate.

The surface-mounted piezoelectric oscillator of the present invention includes an IC component unit integrated by surrounding the outer surface of the IC component with the flexible substrate, and the wiring component of the flexible substrate constituting the IC component unit is arranged with the wiring pattern of the flexible substrate. The IC component mounting pad of the piezoelectric vibrator is electrically connected to the electrode of the IC component.
The surface-mount piezoelectric oscillator according to the present invention is characterized in that the flexible substrate surrounds the bottom surface of the IC component and a part of the outer surface of the piezoelectric vibrator so as to connect them.
In the surface mount piezoelectric oscillator of the present invention, a thermoplastic resin layer is provided in advance on the inner surface of the flexible substrate, and the flexible substrate, the IC component, and the piezoelectric vibrator are bonded by the thermoplastic resin layer. It is characterized by that.

The surface-mount piezoelectric oscillator of the present invention is characterized in that a thermoplastic resin layer is provided in advance on the outer surface of the flexible substrate.
The method for manufacturing a surface-mounted piezoelectric oscillator according to the present invention is any one of the above-described methods for manufacturing a surface-mounted piezoelectric oscillator, wherein a predetermined interval is provided between the inner surface of the flexible substrate and both ends of the flexible substrate. Mounting the IC component and the piezoelectric vibrator so that a surplus portion remains in the portion, bending the flexible substrate so that the IC component and the piezoelectric vibrator overlap, and the surplus of the flexible substrate A step of adhering an inner surface of the part to the outer surface of the IC component and the outer surface of the piezoelectric vibrator.

  The method for manufacturing a surface-mounted piezoelectric oscillator according to the present invention is a method for manufacturing each of the surface-mounted piezoelectric oscillators described above, and a step of preparing a flexible substrate base material in which a plurality of the flexible substrates are integrated into a sheet shape. A step of forming one or two U-shaped cuts or slits along the boundary contour lines of the individual regions of each flexible substrate constituting the flexible substrate base material, and the flexible substrate surface in the individual regions And a step of cutting each flexible substrate along the boundary contour line.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
1A and 1B are an external perspective view and a longitudinal sectional view of a crystal oscillator as an example of a temperature compensated surface mount piezoelectric oscillator (TCXO) of the present invention.
The crystal oscillator 1 has a configuration in which an IC component unit 10 composed of an IC component 11 and a flexible substrate 20 is connected and fixed to the bottom surface of a package of the crystal resonator 2.
The crystal resonator 2 has an element mounting pad 4 electrically connected to each excitation electrode of the crystal resonator element 6 on the upper surface, an insulating substrate 3 having an IC component mounting pad 5 on the bottom, and the element mounting pad 4 And a lid member 8 for hermetically sealing the quartz resonator element 6.
The insulating substrate 3 according to this example is a box-shaped package having a recess on the upper surface, but the crystal resonator element 6 connected to the element mounting pad 4 formed on the flat insulating substrate surface by a conductive adhesive is used. You may make it airtightly seal with a reverse saddle-shaped lid member.

The IC component 11 is made of a semiconductor substrate such as a silicon substrate provided with an oscillation circuit and a temperature compensation circuit, and has an electrode (gold bump or the like) 11a electrically connected to the IC component mounting pad 5 on its upper surface. .
As is well known, the flexible substrate 20 has a configuration in which a wiring pattern is formed on the surface or inside of a flexible insulating sheet. The flexible substrate 20 has a configuration in which at least a part of the outer surface of the IC component 11 is covered and covered to protect it, and four mounting terminals 21 are exposed on the bottom surface.
In this example, an insulating thermoplastic resin layer 25 is formed on the inner surface of the flexible substrate 20 so as to be in close contact with and cover the entire upper surface, the entire left and right side surfaces, and most of the lower surface of the IC component 11. In addition to the function as an adhesive layer, the thermoplastic resin layer 25 is provided between the outer surface of the IC component and the inner surface of the flexible substrate 20 and is in close contact with the two, thereby protecting the IC component from external force and moisture. To do.

Further, as shown in the figure, an insulating thermoplastic resin layer 26 may be formed on the outer surface of the flexible substrate 20 to protect the outer surface of the flexible substrate.
The electrode 11a of the IC component 11 and the IC component mounting pad 5 on the bottom surface of the crystal resonator are conducted through a wiring pattern on the flexible substrate. Further, each mounting terminal 21 located on the bottom surface of the flexible substrate 20 is electrically connected to the IC component mounting pad 5 and the IC component electrode 11a through the wiring pattern of the flexible substrate 20.
The thermoplastic resin layers 25 and 26 are not essential, and the IC component unit 10 may be formed by adhering the flexible substrate and the IC component with an arbitrary insulating adhesive. Further, the thermoplastic resin layer 25 may be provided only on the inner side surface of the flexible substrate 20, the thermoplastic resin layer 26 may be provided only on the outer side surface of the flexible substrate 20, or as in the illustrated embodiment. The thermoplastic resin layers 25 and 26 may be simultaneously provided on both surfaces of the flexible substrate 20. For example, when a structure is provided in which the thermoplastic resin is provided only on the inner side surface and not provided on the outer side surface, it is easy to distinguish the front and back of the flexible substrate (or a flexible substrate base material described later).

In this way, by connecting and fixing the IC component unit 10 in which the IC component 11 is surrounded by the flexible substrate to the bottom surface of the package of the crystal unit 2, a protective layer that protects the IC component from external force and moisture without using an underfill is provided. It has become possible to build an oscillator with this. For this reason, the IC component unit 10 can be miniaturized following the miniaturization of the crystal unit, and the plane area of the entire oscillator can be miniaturized.
In addition, this surface mount type crystal oscillator uses a flexible substrate instead of the conventional resin as a means for covering and protecting the outer surface of most of the IC components externally attached to the crystal resonator. In addition to making the overall shape of the device compact, the layout of the connection pads with the crystal unit, the connection pattern with the IC component electrodes, the mounting terminals, etc. The degree of freedom increases and it becomes easier to design.

2A and 2B are diagrams showing the configuration and manufacturing procedure of the IC component unit.
As shown in FIG. 2A, the flexible substrate 20 includes four mounting terminals 21 on the outer surface thereof, and a pattern connected to the inner surface of the electrode (gold bump or the like) 11a of the IC component 11 at an integrated position. 22. Thermoplastic resin layers 25 and 26 are respectively formed on the inner and outer surfaces of the flexible substrate that avoids the mounting terminals 21 and the patterns 22.
Next, as shown in (a) and (b), after flip-chip mounting so that each electrode 11a of the IC component has a one-to-one correspondence on the pattern 22, the flexible substrate 20 positioned outside the IC component 11 is mounted. It is folded and superposed on the electrode non-formation surface of the IC component 11.
Next, the IC component unit 10 can be completed by joining and integrating the flexible substrate and the IC component by heating to the softening temperature of the thermoplastic resin while suppressing the outer surface of the flexible substrate by a suppressing means (not shown).
In this way, the assembly of the IC component unit is completed by a simple manufacturing procedure, and the oscillator can be completed by connecting the completed IC component unit 10 to the crystal unit package, thus simplifying the total manufacturing procedure and improving productivity. Can be increased.

Next, FIGS. 3A and 3B are an external perspective view and a longitudinal sectional view of a surface-mounted crystal oscillator according to another embodiment of the present invention. The same parts as those in the embodiment of FIG.
In this crystal oscillator 1, one surface of the IC component 11 (semiconductor surface not having the electrode 11 a) is disposed on the outer surface of the lid member 8 of the crystal resonator 2 with the lid member 8 facing downward via an insulating adhesive 30. Or it is made to contact | abut directly, and the other surface of IC component which has the electrode 11a is turned downward. Further, the flexible substrate 20 tightly surrounds the bottom surface and both the left and right side surfaces of the IC component and a part of the outer surface of the crystal unit 2 (the left and right side surfaces and the top surface).
Thermoplastic resins 25 and 26 are laminated on the inner surface or the outer surface of the flexible substrate 20 as necessary.
The mounting terminal 21 exposed on the outer surface of the flexible substrate 20 is electrically and mechanically connected to the electrode 11a of the IC component, and the IC component is mounted on the bottom surface (upper surface in FIG. 3) of the crystal unit 2. The pad 5 is electrically connected to the IC component electrode 11a and the mounting terminal 21 through a wiring pattern on a flexible substrate covering the pad 5.

In this embodiment, since the IC component 11 is in contact with the crystal unit 2 and the entire part is surrounded by the flexible substrate 20 that also functions as a protective layer, the IC can be used without using an underfill. It has become possible to build an oscillator with a protective layer that protects components from external forces and moisture. For this reason, the IC component unit 10 can be miniaturized following the miniaturization of the crystal unit, and the plane area of the entire oscillator can be miniaturized.
Further, the crystal oscillator according to this embodiment not only uses the flexible substrate as a protection means for the IC parts, but also as a means for fixing the IC parts to the crystal resonator. It is possible to provide a low-cost and compact oscillator without increasing the number of steps.

  Next, FIG. 4 is a diagram showing an example of the assembly procedure of the oscillator according to the embodiment of FIG. 3. First, as shown in FIG. 4, the IC component is developed with the inner surface of the flexible substrate 20 facing upward. 11 electrodes 11a and IC component mounting pads 5 of the crystal resonator 2 are connected to corresponding wiring patterns on the inner surface of the flexible substrate, respectively. At this time, care is taken so that the surplus portion 20a remains between both ends of the flexible substrate and the IC component and the crystal resonator. Subsequently, as shown by the arrows, the flexible substrate is folded in two at the longitudinal center so that the electrode non-formation surface of the IC component 11 and the lid member of the crystal unit 2 are in contact with each other. Assemble. When the thermoplastic resin layer 25 is formed on the inner surface of the flexible substrate, it is completed by heating to the softening temperature of the thermoplastic resin and bonding it to the outer surface of the IC component and the outer surface of the crystal unit, and then cooling and solidifying. .

Next, a procedure for mass-producing the IC component unit 10 shown in FIG. 1 using a flexible substrate base material in which a plurality of flexible substrates 20 are integrated into a sheet shape will be described.
As the simplest manufacturing method, as shown in FIG. 5, first, the IC component 11 is placed on a predetermined position on the individual area surface of the flexible substrate base material 40 in which the flexible substrate pieces 20 are connected in a sheet shape. Then, the IC component electrode 11a is flip-chip mounted on the pattern 22 in the flexible substrate piece region. Next, the base material may be cut along the outer contour line (boundary contour line) L of the piece region.
Thereafter, both end portions 20a of the flexible substrate 20 are bent and heated to the softening temperature of the thermoplastic resin 25 in a state where the thermoplastic resin 25 on the inner surface is held in close contact from both side surfaces to the upper surface of the IC component, and then cooled. As a result, the IC component unit 10 is completed.

FIGS. 6A and 6B show another method for manufacturing an IC component unit. In this method, a U-shaped slit is formed along the outline of each piece region on the flexible substrate base material 40. (Or a cut line) 31 is formed. Accordingly, after the IC component is flip-chip mounted on the flexible substrate piece 20 positioned inside the slit etc. 31, the slit etc. 31 formed along the outer outline (boundary outline) L of the piece area is formed. Use to cut the base material.
Thereafter, both end portions 20a of the flexible substrate 20 are bent and heated to the softening temperature of the thermoplastic resin 25 in a state where the thermoplastic resin 25 on the inner surface is held in close contact from both side surfaces to the upper surface of the IC component, and then cooled. As a result, the IC component unit 10 is completed.
In the above-described embodiment, a crystal oscillator is illustrated as a representative example of a piezoelectric oscillator. However, the present invention can be applied to an oscillator that uses a piezoelectric vibration element made of a piezoelectric material.

(A) And (b) is the external appearance perspective view and longitudinal cross-sectional view of the crystal oscillator as an example of the temperature compensation type surface mount type piezoelectric oscillator (TCXO) of this invention. (A) And (b) is a figure which shows the structure and manufacturing procedure of an IC component unit. (A) And (b) is an external appearance perspective view and longitudinal cross-sectional view of the surface mount-type crystal oscillator which concerns on other embodiment of this invention. The figure which shows an example of the assembly | attachment procedure of the oscillator which concerns on embodiment of FIG. The figure explaining the method of manufacturing an IC component unit. (A) And (b) is a figure explaining the other method of manufacturing IC component unit. The longitudinal section showing the conventional composition of the surface mount type piezoelectric oscillator as a two-story structure type (H type) module.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Crystal oscillator, 2 ... Crystal oscillator (piezoelectric vibrator), 3 ... Insulating substrate, 4 ... Element mounting pad, 5 ... IC component mounting pad, 6 ... Crystal vibration element, 7 ... Conductive adhesive agent, 8 ... Cover Member: 10: IC component unit, 11: IC component, 11a: IC component electrode, 20: flexible substrate, 20a: surplus portion, 21: mounting terminal, 22: pattern, 25, 26: thermoplastic resin layer, 30: insulation Adhesive, 31 ... slit, etc. 40 ... flexible substrate base material.

Claims (7)

An insulating substrate having an element mounting pad electrically connected to each excitation electrode of the piezoelectric vibration element on the upper surface and an IC component mounting pad on the bottom, a piezoelectric vibration element mounted on the element mounting pad, and the piezoelectric A piezoelectric vibrator having a lid member for hermetically sealing the vibration element;
An IC component comprising an electrode electrically connected to the IC component mounting pad and constituting an oscillation circuit;
A flexible substrate that is in close contact with at least a part of the outer surface of the IC component and has a mounting terminal exposed on the bottom surface,
A surface-mount type piezoelectric oscillator, wherein the IC component mounting pad, the electrode of the IC component, and the mounting terminal are electrically connected by the flexible substrate. An IC component unit that surrounds and integrates the outer surface of the IC component by the flexible substrate;
2. The surface-mount type piezoelectric device according to claim 1, wherein an IC component mounting pad of the piezoelectric vibrator and an electrode of the IC component are electrically connected through a wiring pattern of a flexible substrate constituting the IC component unit. Oscillator.   2. The surface-mount type piezoelectric oscillator according to claim 1, wherein the flexible substrate surrounds the bottom surface of the IC component and a part of the outer surface of the piezoelectric vibrator so as to be connected to each other.   A thermoplastic resin layer is provided in advance on an inner surface of the flexible substrate, and the flexible substrate, the IC component, and the piezoelectric vibrator are bonded by the thermoplastic resin layer. 3. A surface-mount piezoelectric oscillator according to 3.   The surface-mount type piezoelectric oscillator according to claim 1, wherein a thermoplastic resin layer is provided in advance on an outer surface of the flexible substrate. A method for manufacturing a surface-mounted piezoelectric oscillator according to any one of claims 1 to 5,
Mounting the IC component and the piezoelectric vibrator so as to leave a predetermined interval on the inner surface of the flexible substrate and to leave an excess portion at both ends of the flexible substrate;
Bending the flexible substrate so that the IC component and the piezoelectric vibrator overlap;
Bonding the inner surface of the excess portion of the flexible substrate to the outer surface of the IC component and the outer surface of the piezoelectric vibrator;
A method for manufacturing a surface-mounted piezoelectric oscillator, comprising: A method for manufacturing the surface-mounted piezoelectric oscillator according to claim 1,
Preparing a flexible substrate base material in which a plurality of the flexible substrates are integrated into a sheet shape;
Forming one or two U-shaped cuts or slits along the boundary contour lines of the individual regions of each flexible substrate constituting the flexible substrate base material; and
Mounting the IC component on the flexible substrate surface in the piece area;
Cutting each flexible substrate along the boundary contour line; and
A method for manufacturing a surface-mounted piezoelectric oscillator, comprising:

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