JP4157371B2 - Manufacturing method of crystal oscillator for surface mounting - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface mount crystal oscillator (hereinafter referred to as a surface mount oscillator) as an industrial technical field, and more particularly to a method of manufacturing a surface mount oscillator that promotes miniaturization.
[0002]
[Prior art]
BACKGROUND OF THE INVENTION Surface-mounted oscillators are small and light, and are therefore widely used as frequency and time reference sources, especially in portable electronic devices. In recent years, there has been a demand for smaller surface-mount oscillators from the trend toward further miniaturization.
[0003]
(Example of Prior Art) FIG. 2 is a view of a surface-mount oscillator for explaining one conventional example. FIG. 2 (a) is a sectional view and FIG. 2 (b) is a plan view of a crystal piece.
[0004]
The surface mount oscillator includes a mounting substrate 1, an IC chip 2, a crystal piece 3, and a cover 4. The mounting substrate 1 is made of a laminated ceramic having a concave shape with an inner wall, and is formed by laminating a bottom wall 5 and first and second frame walls 6 (ab). An IC connection terminal (not shown) is provided on the bottom of the recess, a crystal connection terminal is provided on the stepped portion, and an external terminal 7 for surface mounting is provided on the outer surface. The external terminal 7 is connected to the IC connection terminal through the laminated surface.
[0005]
The IC chip 2 integrates an oscillation circuit and has an IC terminal (not shown) including at least a power supply, an output, and a ground terminal on one main surface. Then, one main surface of the IC chip 2 is fixed to the IC connection terminal on the bottom surface of the concave portion by ultrasonic thermocompression or thermocompression using the bumps 8 and is electrically and mechanically connected.
[0006]
The crystal piece 3 has excitation electrodes 9 on both main surfaces, and for example, extraction electrodes 10 extend on both sides of one end. Then, both ends of the extended end portion of the extraction electrode 10 are fixed to the crystal connection terminal of the recess step portion by the conductive adhesive 16 and are electrically and mechanically connected.
[0007]
[Problems to be solved by the invention]
(Problem of the prior art) However, in the surface mount oscillator having the above configuration, since the component parts are four points of the mounting substrate 1, the IC chip 2, the crystal piece 3 and the cover 4, it is difficult to further reduce the size significantly. And In the above example, since the IC chip 2 and the crystal piece 3 are arranged in the thickness direction, there is a problem of particularly increasing the height dimension.
[0008]
Further, since the mounting substrate 1 is made of a multilayer ceramic, the thickness of the first frame wall 6a needs to be equal to or greater than a certain value, for example, the width, in the manufacturing process of the lamination and firing of the green sheets. Therefore, the inner bottom surface area in the container is impaired.
[0009]
On the other hand, the larger the plate surface area, the better the vibration characteristics of the crystal piece 3 and, for example, the capacity ratio C0 / C1 is reduced to increase the degree of freedom of design and facilitate the design. C0 is an equivalent parallel capacitance (interelectrode capacitance), and C1 is an equivalent series capacitance. Therefore, a container having a large inner bottom surface area with a small planar outer dimension of the mounting substrate 1 is required.
[0010]
In addition, in the related art (quartz crystal resonator), there is one in which the mounting substrate 1 has a flat plate shape, and a cover 4 made of a concave ceramic is sealed with glass or resin (not shown). In such a thing, since it is integral molding, the frame width of the cover 4 can be reduced and the inner bottom surface area can be increased. However, in the case of glass sealing, the strength of the glass as a bonding material is small and there is a problem in impact resistance characteristics, and in the case of resin sealing, there is a problem that outside air such as moisture enters and lowers vibration characteristics. .
[0011]
The object of the present invention is to provide a surface-mount oscillator that firstly facilitates miniaturization and particularly reduces the height dimension, and secondly provides a surface mount oscillator with good vibration characteristics and easy design. And
[0012]
[Non-Patent Document 1]
Advanced Materials Dictionary, published on February 25, 1997, 4th printing, P629-630.
[Non-Patent Document 2]
Toyota Central R & D Review, Vol. 28, No4 (1993.12) P53-54
[0013]
[Means for Solving the Problems]
(Points of interest and application) The present invention focuses on the anodic bonding technique between the silicon substrate and the glass containing mobile ions shown in Non-Patent Documents 1 and 2 above, and uses a silicon substrate as a flat mounting substrate. As a concave cover, it was applied to a container for a surface mount oscillator, and an oscillation circuit was integrated (integrated) on a silicon substrate.
[0014]
(Solution) The present invention includes a crystal piece, an IC constituting an oscillation circuit , a crystal connection terminal , an IC connection terminal , a conduction electrode, and a conductive path as described in the claims (Claim 1). has a surface, the conductive electrode and via the conductive path, Ri Do from a mounting substrate having a flat plate shape having an external terminal on the outer surface of connecting said IC connection terminals electrically, the cover was a concave The mounting substrate is a silicon substrate in which an oscillation circuit is integrated into an IC , the cover is glass having movable ions, and the crystal connection terminal, the IC connection terminal, the conduction electrode, and the conduction path are provided on the surface of the silicon substrate. The conductive electrode and the external terminal are electrically connected by an electrode through hole shielded by the polysilicon layer, and the silicon substrate and the cover are connected to each other. A method of manufacturing a crystal oscillator in which the crystal piece is encapsulated by anodic bonding, the step of forming the polysilicon layer on one main surface of the mounting substrate , and covering the entire main surface of the mounting substrate . A step of providing, on both main surfaces of the mounting substrate, one mask and a second mask provided on the other main surface of the mounting substrate and having a hole corresponding to an electrode through-hole electrically connected to the conductive electrode; Etching the mounting substrate provided with the first mask and the second mask to form a through hole reaching the conduction electrode; and providing the electrode in the through hole to form the electrode through hole Process.
And
[0015]
As a result, the silicon substrate serves as both a conventional mounting substrate and an IC chip, so that the number of components can be reduced, and the size and particularly the height can be significantly reduced. In addition, since the cover has a concave glass, the frame width can be reduced. Therefore, the planar outer shape can be reduced and the inner bottom surface area can be increased. Thereby, the vibration characteristic of the crystal piece is improved. And without using sealing materials, such as glass and resin, impact resistance is made favorable and intrusion of external air is prevented. In addition, since the polysilicon layer is provided on the surface of the silicon substrate and the electrode through hole is provided on the lower surface thereof, the sealing can be reliably maintained by the polysilicon layer.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a view of a surface mount oscillator for explaining an embodiment of the present invention. FIG. 1 (a) is a sectional view and FIG. 1 (b) is a plan view excluding a cover. However, the frame in the plan view is a contact portion of the cover. In addition, the same number is attached | subjected to the same part as a prior art example, and the description is simplified or abbreviate | omitted.
[0017]
The surface-mount oscillator is formed by enclosing a crystal piece 3 in a container composed of a flat mounting substrate 1 and a concave cover 4. The mounting substrate 1 is a silicon substrate, and the cover 4 is glass containing movable ions such as Na + and Li +. The silicon substrate has an oscillation circuit integrated therein, and crystal connection terminals 11 are exposed on both sides of one end of the inner surface, and IC connection terminals 12 such as a power supply, an output, and a ground terminal are exposed in the central region. The IC connection terminal 12 is connected to a conduction terminal 13 provided at four corners on the inner surface by a conduction path 14. At the four corners of the outer surface, there are external terminals 7 that are electrically connected to the conductive terminals 13.
[0018]
The crystal connection terminal 11, the IC connection terminal 12, the conductive path 14, and the conductive terminal 13 are made of a polysilicon layer (P ⁺ Si) in which, for example, high-concentration boron is diffused on the surface of the silicon substrate. Then, for example, an Au layer (not shown) is provided on the polysilicon layer serving as the crystal connection terminal 11, and both ends of one end of the crystal piece 2 are fixed by ultrasonic thermocompression or thermocompression using the bumps 8. Further, an electrode through hole 15 is provided on the lower surface of the conduction terminal 13 and is electrically connected to the external terminal 7.
[0019]
First, a large number of polysilicon layers corresponding to crystal connection terminals 11, IC connection terminals 12, conductive paths 14, and conduction terminals 13 are provided on one main surface of a silicon wafer (not shown). For example, a first mask is provided on the entire surface. Provide. In addition, a second mask having a hole corresponding to the electrode through hole 15 is provided on the other main surface. Then, for example, the crystal wafer is etched in KOH (potassium hydroxide) solution. Thereby, a through hole reaching the polysilicon layer is formed.
[0020]
Although the silicon substrate is soluble in KOH, the polysilicon layer is not soluble. The first and second masks are made of, for example, SiO2, SiN or the like that does not dissolve in KOH. Next, Cr, Cu, and Au layers are formed by vapor deposition, sputtering, or the like on the through holes and the four corners that will be the respective mounting substrates 1. Thereby, the electrode through hole 15 and the mounting terminal 7 are formed. Then, it is divided into individual mounting substrates (silicon substrates) 1.
[0021]
Here, the cover 4 is made of Pyrex (registered trademark) glass and contains movable ions which are Na ⁺ . Then, the upper surface of the frame wall of the cover 4 is brought into contact with the outer peripheral surface of the mounting substrate 1 and a negative voltage of about 500 V is applied to the cover side while heating (300 to 400 ° C.). The contact surfaces of the mounting substrate 1 and the cover 4 are mirror-polished.
[0022]
In such a case, anodic bonding is performed as shown in Non-Patent Documents 1 and 2. That is, the movable ions Na ⁺ contained in the cover 4 (Pyrex (registered trademark) glass) move to form a Na ⁺ ion deficient layer at the interface with the mounting substrate 1 (silicon substrate), and a large electrostatic attraction is generated. And the interface of both leads to a chemical bond. Accordingly, the bond strength is significantly increased.
[0023]
With such a configuration, the silicon substrate on which the oscillation circuit is integrated is applied to the mounting substrate 1, so that the conventional IC chip 2 is unnecessary. Therefore, the number of parts can be reduced, and miniaturization is promoted. In particular, in this example, the height dimension can be reduced in each step. Further, since the cover 4 is made of glass and has a concave shape, the frame width can be reduced, the planar outer shape can be reduced, and the inner bottom surface area can be increased. Therefore, the outer shape of the crystal piece 3 can be increased, the vibration characteristics are improved, and the degree of freedom in design is increased.
[0024]
Since the mounting substrate 1 is anodic bonded, a glass or resin sealing material is not required as in the prior art, and the impact resistance is improved to prevent the entry of outside air. Moreover, since the electrode through hole 15 electrically connected to the IC connection terminal 12 is shielded by a polysilicon layer provided on one main surface of the silicon substrate, airtightness is ensured.
[0025]
[Other matters]
In the above embodiment, the cover 4 is made of Pyrex (registered trademark) glass, but may be, for example, Devitron glass shown in Patent Document 2 (p54), and basically includes movable ions such as Na + and Li + ions. That's fine.
[0026]
【The invention's effect】
The present invention, via a crystal piece, the IC constituting an oscillation circuit, crystal connection terminals, IC connection terminals, has on the inner surface of the conductive electrode and the conductive path, the conductive electrode and the conductive path, the IC a mounting substrate having a flat plate shape having an external terminal on the outer surface to be connected to the connection terminals electrically, Ri Do a cover which is concave, wherein the mounting board as the silicon substrate having an IC oscillation circuit, wherein the cover is movable The glass includes ions, and the crystal connection terminal, the IC connection terminal, the conduction electrode, and the conduction path are formed of a polysilicon (P ⁺ Si) layer provided on the surface of the silicon substrate, and the conduction electrode and the external the terminal is electrically connected by the electrode through-holes is shielded by the polysilicon layer, the silicon substrate and the cover by anodic bonding, producing side of the crystal oscillator enclosing said crystal piece A is a step of forming the polysilicon layer on one main surface of the mounting substrate, a first mask covering the entire surface of one main surface of the mounting substrate, wherein provided on the other major surface of the mounting board A step of providing a second mask having holes corresponding to electrode through-holes electrically connected to the conductive electrodes on both main surfaces of the mounting substrate; and the mounting provided with the first mask and the second mask. The method includes a step of etching a substrate to form a through hole reaching the conduction electrode, and a step of forming an electrode in the through hole to form the electrode through hole.
[0027]
Therefore, the present invention can promote downsizing and particularly reduce the height dimension. In addition, it is possible to provide a method for manufacturing a surface-mount oscillator that has good vibration characteristics and can be easily designed.
[Brief description of the drawings]
FIGS. 1A and 1B are views of a surface-mounted oscillator for explaining an embodiment of the present invention, in which FIG. 1A is a cross-sectional view and FIG. 1B is a plan view excluding a cover.
2A is a cross-sectional view of a surface mount oscillator, and FIG. 2B is a plan view of a crystal piece 3; FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Mounting board, 2 IC chip, 3 Crystal piece, 4 Cover, 5 Bottom wall, 6 Frame wall, 7 External terminal, 8 Bump, 9 Excitation electrode, 10 Lead electrode, 11 Crystal connection terminal, 12 IC connection terminal, 13 Conduction Electrode, 14 conductive path, 15 electrode through hole, 16 conductive adhesive.

Claims (1)

A piece of crystal,
An IC constituting an oscillation circuit ;
Crystal connection terminals, IC connection terminals, has on the inner surface of the conductive electrode and conductive path via the conductive electrode and the conductive path, a flat plate having an external terminal on the outer surface of connecting said IC connection terminals electrically and the mounting substrate was Jo,
Ri Do a cover which is concave,
The mounting substrate is a silicon substrate in which an oscillation circuit is integrated into an IC , and the cover is glass having movable ions,
The crystal connection terminal, the IC connection terminal, the conductive electrode, and the conductive path are each composed of a polysilicon (P ⁺ Si) layer provided on the surface of the silicon substrate,
A method of manufacturing a crystal oscillator in which the conduction electrode and the external terminal are electrically connected by an electrode through hole shielded by the polysilicon layer, the silicon substrate and the cover are anodically bonded, and the crystal piece is enclosed Because
Forming the polysilicon layer on one principal surface of the mounting substrate;
A first mask that covers the entire surface of one main surface of the mounting substrate; and a second mask that is provided on the other main surface of the mounting substrate and has holes corresponding to electrode through holes that are electrically connected to the conductive electrodes. Providing on both main surfaces of the mounting substrate;
Etching the mounting substrate provided with the first mask and the second mask to form a through hole reaching the conduction electrode;
Providing the electrode in the through hole to form the electrode through hole;
A method for manufacturing a crystal oscillator, comprising:

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