JP2007096372A - Surface mounting piezoelectric oscillator and its manufacturing process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface mounting piezoelectric oscillator which does not cause complication of structure or increase in number of manufacturing steps even in such a case as a cavity filled with underfill cannot be secured in a piezoelectric vibrator and the oscillation circuit IC section of three-dimensional arrangement, and to provide its manufacturing process. <P>SOLUTION: The process for manufacturing a surface mounting piezoelectric oscillator comprising a piezoelectric vibrator 21 and an IC component 10 mounted on a packaging substrate 2 and having such a structure as the entirety of the IC component is covered with a resin layer 41 from the upper surface of the substrate to the upper surface level of a conductor block 31 comprises an IC component mounting step performing flip-chip mounting on a wiring pattern 5 through small bumps 7, a hot press step for integrally coating the IC component with a resin layer while embedding, a step for irradiating the resin layer with a laser beam to form a plurality of wiring pattern exposure openings, a step for forming a conductor block on a wiring pattern in contact therewith by filling each opening with a conductive material, and a piezoelectric vibrator mounting step for securing an electrode on the bottom of the piezoelectric vibrator to the exposed upper surface of each conductor block through a connection conductor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an underfillless structure required with the progress of miniaturization, a surface-mounted piezoelectric oscillator that can cope with a cavityless structure, 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 parts as a module.
Examples of the surface mounting electronic device constructed by modularizing and packaging a plurality of related components include a piezoelectric vibrator, a piezoelectric oscillator, a SAW device, and the like.
By the way, in the conventional surface mount type oscillator, circuit elements such as transistors, resistors, capacitors, etc. constituting an oscillation circuit and a temperature compensation circuit are mounted on the mounting substrate as individual chip parts, and thus are downsized. There was a limit. Therefore, recently, in order to reduce the size of the piezoelectric oscillator, a one-chip IC component in which circuit elements constituting an oscillation circuit, a temperature compensation circuit and the like are integrated in a unique integrated circuit is used.
In order to achieve further miniaturization while maintaining the function of the piezoelectric oscillator high, for example, a module having a two-story structure as shown in FIG. 3 is employed.
That is, FIG. 4 is a schematic longitudinal sectional view showing a conventional configuration of a surface-mount type piezoelectric device (quartz oscillator) as a two-story structure type (H type) module, which is a container composed of a ceramic container body 101 and a metal lid 102. A quartz resonator 100 in which a quartz resonator element 103 is housed, and a bare chip that constitutes an oscillation circuit, a temperature compensation circuit, and the like on a ceiling surface in a cavity (cavity) 105a of a container 105 joined to the bottom surface of the quartz resonator 100 And a bottom structure (IC component unit) 107 on which an IC component 106 is flip-chip mounted. In order to protect the IC component 106 accommodated in the void 105a, the void 105a is filled with a resin (underfill) 110 to cover the entire IC component.

When this crystal oscillator is mounted on a printed board, soldering is performed using mounting terminals 105b provided on the bottom surface of the container 105 (for example, Patent Document 1).
In the conventional package structure described above, it is necessary to fill the space 105a of the container 105 with the underfill 110. However, as the size of the oscillator is reduced, it is difficult to secure a space for injecting the underfill. Accordingly, a package having an underfillless structure or a cavityless structure has been required.
Patent Document 2 discloses a package structure of a piezoelectric oscillator having an underfillless structure or a cavityless structure. In this conventional example, a circuit element (IC component) is mounted on an oscillation circuit board, and then only the circuit element is covered with resin, and further, via a large-diameter conductor mounted on a connection terminal on the circuit board. A packaged piezoelectric vibrator is mounted.
However, this conventional example has a problem that the structure and the manufacturing method for preventing the resin from flowing into the connection terminal located in the proximity when the circuit element is coated with the resin are complicated. That is, it is necessary to provide a dam or a mask so that the resin does not enter the connection terminal when the resin coating is performed, and the process before the resin coating becomes complicated and productivity is lowered.
JP 2000-278047 A JP 2004-180012 A

  The present invention has been made in view of the above, and a surface mount piezoelectric oscillator in which a piezoelectric vibrator and a one-chip IC component constituting an oscillation circuit or the like are juxtaposed in a vertical position on a mounting substrate. Even when an underfillless structure or a cavityless structure is adopted in response to the inability to secure a cavity for filling the underfill at the request of the above, problems such as a complicated structure and an increase in manufacturing steps may occur. The present invention provides a non-surface-mounted piezoelectric oscillator and a method for manufacturing the same.

In order to solve the above-mentioned problem, a manufacturing method according to the invention of claim 1 is a surface-mount type piezoelectric oscillator comprising a mounting substrate, and a piezoelectric vibrator and an IC component mounted on the mounting substrate, The mounting substrate includes a flat insulating substrate, a mounting electrode provided on the bottom of the insulating substrate, and a wiring pattern provided on the top surface of the insulating substrate, and the IC component is provided on the wiring pattern on the top surface of the insulating substrate. The piezoelectric vibrator is mounted on the upper surface of the conductor block fixed on the other wiring pattern on the upper surface of the insulating substrate via a connecting conductor, and is connected to the upper surface of the conductor block from the upper surface of the insulating substrate. A method of manufacturing a surface-mounted piezoelectric oscillator in which the entire IC component is resin-coated with a resin layer covering up to a level of the IC, wherein the IC is formed on the wiring pattern on the mounting substrate. IC component mounting process for flip-chip mounting products with the above-mentioned small bumps, and mounting the resin layer while embedding the IC components by placing a sheet-like resin on the mounting substrate and heating it with pressure A heat pressing step, a laser irradiation step of irradiating the resin layer with a laser beam to form a plurality of openings for exposing the other wiring patterns, and filling the conductive blocks in the openings to form the conductor block. A conductor block forming step for forming a connection on the other wiring pattern, and a piezoelectric vibrator mounting step for fixing the electrode at the bottom of the piezoelectric vibration element to the exposed upper surface of each conductor block via a connecting conductor. It is characterized by comprising.
Since it is possible to coat the resin after completing the mounting of IC components and conductor blocks on each wiring pattern on the flat mounting board, a structure to prevent the resin from entering the wiring pattern in advance Save time and effort to form. Therefore, the number of manufacturing steps can be simplified, the productivity can be improved, and the manufacturing cost can be reduced. The oscillator structure is suitable for batch processing using a large-area mounting board base material.
According to a second aspect of the present invention, in the first aspect of the present invention, after the conductor block forming step, an adhesive application step of applying an adhesive to an appropriate position on the upper surface of the resin layer is performed.
By filling the gap between the upper surface of the resin layer and the bottom surface of the packaged piezoelectric oscillator, it is possible to increase the connection strength between the two.
A surface-mounted piezoelectric oscillator according to a third aspect of the present invention is manufactured by the manufacturing method according to the first or second aspect.

  According to the present invention, when mounting a piezoelectric vibrator packaged with an IC component on a mounting substrate so as to have a vertical positional relationship, it is possible to use a flat mounting substrate, so that a cavity-less configuration is achieved. It is possible to achieve downsizing. Also, in batch processing using mounting board base materials, IC components can be coated with resin without going through complicated steps such as providing damming means to prevent resin from flowing into part of the wiring pattern. Is possible.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
FIGS. 1A and 1B are an external perspective view and a longitudinal sectional view showing a configuration of a surface mount piezoelectric oscillator according to an embodiment of the present invention. Here, a crystal oscillator will be described as an example.
The surface-mount piezoelectric oscillator 1 includes a flat mounting substrate 2, an IC component 10 mounted on the mounting substrate 2, and a packaged crystal resonator (piezoelectric resonator) 21.
The mounting substrate 2 includes a flat insulating substrate 3, mounting electrodes 4 provided on the bottom of the insulating substrate, and wiring patterns (lands) 5 and 6 provided on the upper surface of the insulating substrate.
The IC component 10 is a semiconductor bare chip that constitutes an oscillation circuit, a temperature compensation circuit, and the like, and is flip-chip mounted on the wiring pattern 5 on the upper surface of the insulating substrate 3 by small bumps 7 having a low height.

The crystal resonator 21 is mounted on the upper surface of a tall conductor block 31 fixed on the other wiring pattern 6 on the upper surface of the insulating substrate via a connection conductor 32 such as solder. The crystal resonator 21 supports a crystal resonator element 23 using a conductive adhesive on a connection pad 22b provided in a recess 22a of a container body 22 made of ceramic or the like, and the recess 22a is supported by a metal lid 24. It has a sealed configuration. An external electrode 25 is provided at the bottom of the container body 22, and the crystal resonator 21 is fixed to the upper surface of the conductor block 31 by connecting the external electrode 25 and the connecting conductor 32. The quartz resonator element 23 has a configuration in which conductor patterns (excitation electrodes and lead electrodes drawn from the excitation electrodes) are formed on both main surfaces of the quartz substrate.
The conductor block 31 is dimensioned so as to be taller than the IC component 10 flip-chip mounted on the mounting substrate 2. That is, the flat upper surface of the conductor block 31 is set to have a higher positional relationship than the height position of the upper surface of the IC component 10 after mounting. A method of forming the conductor block 31 will be described in the manufacturing method described later.
Further, the entire IC component is resin-coated with a resin layer 41 that covers from the upper surface of the insulating substrate 3 to the level of the upper surface of the conductor block.

Alternatively, the gap between the upper surface of the resin layer 41 and the lower surface of the crystal unit 21 may be filled with an adhesive 45 to integrate them. Thus, by filling the gap between the upper surface of the resin layer and the bottom surface of the packaged piezoelectric oscillator, it is possible to increase the connection strength between the two.
The oscillator 1 of the present invention is characterized by a structure in which not only the IC component 10 but also the substrate upper surface including the conductor block 31 on which the crystal resonator 21 is mounted on the mounting substrate is covered with the resin layer 41, as described above. The configuration other than the IC component 10 is coated with the resin, thereby simplifying the configuration and simplifying the manufacturing process as described later.
Therefore, according to the present invention, in a surface-mounted crystal oscillator in which a packaged crystal resonator and a one-chip IC component are mounted on a mounting substrate so as to be in a vertical position relationship, an underfill is caused by a request for miniaturization. Even when an underfillless structure or a cavityless structure is employed in response to the inability to secure a cavity for filling, problems such as a complicated structure and an increase in the number of manufacturing steps can be solved.

Next, a method for manufacturing the surface-mounted crystal oscillator will be described with reference to a process chart shown in FIG.
The following steps are performed by batch processing using a mounting substrate base material in which a large number of mounting substrates are connected in the form of a sheet, but here, in order to clarify the manufacturing procedure for each oscillator piece, This will be described with reference to a sectional view of the piece.
FIG. 2A shows an IC component mounting process, in which the IC component 10 is flip-chip mounted on the wiring pattern 5 on the mounting substrate 2 by the small bumps 7.
In the heat press step of FIG. 2B, a sheet-like resin 41 having a uniform thickness sufficient to embed the IC component 10 is placed on the upper surface of the mounting substrate 2 and pressed by the heat roller 45. The mounting substrate 2 and the IC component 10 are covered and integrated by the resin layer 41 while softening the sheet-like resin 41 and embedding the IC component 10 by heating (hot pressing). The height of the upper surface of the resin layer 41 that is pressed until the upper surface is flattened on the mounting substrate 2 is naturally positioned beyond the upper surface of the IC component 10. The hot pressing may be performed in a vacuum or may be performed during standby.
As a typical example of the sheet-like resin 41, there can be exemplified a sheet-shaped resin compounded with an epoxy resin, a B-stage resin, a dry film resist, and the like.
When mass-producing oscillators by batch processing using a mounting substrate base material in which a large number of mounting substrates are connected in the form of a sheet, the heat press process is performed by using a frame-shaped damming member around the mounting substrate base material. In a surrounded state, the sheet-shaped resin having a large area is placed inside the damming member and then heated while being pressed by the heat roller 45. That is, in this process, the sheet-like resin is simply placed and added without taking a complicated method such as providing a dike or a mask to prevent the resin from entering a specific portion on the mounting board piece. It is sufficient to solidify after pressing and heating, and the productivity can be greatly increased.
In addition, you may fill underfill with arbitrary places before resin coating.

In the laser irradiation process of FIG. 2C, a plurality of openings 41a are formed to expose the other wiring patterns 6 by irradiating the resin layer 41 with laser light. The laser beam irradiation position is controlled by attaching a mask (not shown) on the upper surface of the resin layer 41.
In the conductor block forming step of FIG. 2D, the conductor block 31 is connected and formed on the other wiring pattern 6 by filling each opening 41a with a conductive material 31 such as solder or Ag paste and curing it. As a result, the conductor block 31 is mounted on each wiring pattern 6 on the mounting substrate 2. The height position of the uppermost portion of the conductor block 31 is taller than the upper surface of the IC component mounted on the mounting substrate 2.
In the crystal resonator mounting step of FIG. 2E, the electrode 25 at the bottom of the crystal resonator element is fixed to each exposed upper surface of each conductor block 31 via the connecting conductor 32. In this mounting step, the electrode 25 at the bottom of the quartz-crystal vibrating element is fixed to each exposed upper surface 31a of each conductor block via the connection conductor 32 with solder or the like.
In addition, you may implement the adhesive agent application process which apply | coats the adhesive agent 45 to the planarized resin layer upper surface suitable place after a hot press process (FIG.2 (b)) as needed.
Finally, individual oscillators are obtained by dicing along the boundaries between the pieces.
As described above, according to the manufacturing method of the present invention, an ultra-small, underfillless type and cavityless type surface-mount crystal oscillator can be mass-produced with a simple process using a mounting substrate base material. .

Next, FIG. 3 is a cross-sectional view showing the configuration of a surface-mount type crystal oscillator according to another embodiment of the present invention. In this embodiment, bumps previously fixed to the external electrode 25 at the bottom of the crystal unit 21 are shown. 26 is fixed so as to be embedded from the upper surface of the conductor block 31.
In this embodiment, before the conductive material 31 such as solder or Ag paste filled in the opening 41a formed in the resin layer 41 is cured, the crystal resonator 21 is placed on the resin layer 41 and the bumps 26 are placed. Is embedded in the conductive material 31, and the conductive material 31 is cured after being embedded to complete the fixing of the crystal unit 21 on the resin layer 41.
In the above embodiment, a crystal oscillator is illustrated as a typical example of a crystal oscillator. However, the present invention can be applied to an oscillator using a piezoelectric vibration element made of a piezoelectric material.

(A) And (b) is an external appearance perspective view and longitudinal cross-sectional view which show the structure of the surface mount-type piezoelectric oscillator which concerns on one Embodiment of this invention. (A) thru | or (e) are process drawings of the manufacturing method of the surface mount-type piezoelectric oscillator of this invention. FIG. 6 is a partial cross-sectional configuration explanatory view of a surface-mount piezoelectric oscillator according to another embodiment of the present invention. FIG. 6 is a configuration explanatory diagram of a conventional piezoelectric oscillator.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Surface mount type piezoelectric oscillator, 2 ... Mounting board, 3 ... Insulating board, 4 ... Mounting electrode, 5 ... Wiring pattern, 6 ... Wiring pattern, 7 ... Small bump, 10 ... IC component, 21 ... Crystal oscillator (piezoelectric) (Vibrator), 22 ... container body, 22a ... recess, 22b ... connection pad, 23 ... crystal resonator element, 24 ... metal lid, 25 ... external electrode, 31 ... conductor block, 31a ... upper surface, 32 ... connection conductor, 41 ... resin layer, 41a ... opening, 45 ... heat roller.

Claims (3)

A surface-mount type piezoelectric oscillator comprising a mounting substrate, and a piezoelectric vibrator and an IC component mounted on the mounting substrate, wherein the mounting substrate is provided on a flat insulating substrate and a bottom of the insulating substrate The IC component is flip-chip mounted by a small bump on the wiring pattern on the upper surface of the insulating substrate, and the piezoelectric vibrator is connected to the insulating substrate. A surface in which the entire IC component is resin-coated with a resin layer mounted on the upper surface of the conductor block fixed on the other wiring pattern on the upper surface via a connecting conductor and covering from the upper surface of the insulating substrate to the level of the upper surface of the conductor block. A method of manufacturing a mountable piezoelectric oscillator,
An IC component mounting step in which the IC component is flip-chip mounted by the small bumps on the wiring pattern on the mounting substrate;
A heat press step of covering and integrating the resin layer while embedding the IC component by placing the sheet-like resin on the top surface of the mounting substrate and heating while applying pressure;
A laser irradiation step of forming a plurality of openings for irradiating the resin layer with laser light to expose the other wiring patterns;
A conductor block forming step of filling each of the openings with a conductive material and forming the conductor block on the other wiring pattern;
A piezoelectric vibrator mounting step for fixing the electrode at the bottom of the piezoelectric vibration element to each exposed upper surface of each conductor block via a connecting conductor;
A method for manufacturing a surface-mounted piezoelectric oscillator, comprising:   2. The method of manufacturing a surface-mount piezoelectric oscillator according to claim 1, wherein an adhesive application step of applying an adhesive to an appropriate position on the upper surface of the resin layer is performed after the conductor block forming step.   A surface-mount piezoelectric oscillator manufactured by the manufacturing method according to claim 1.

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