JP2008155221A - Brazing filler metal, piezoelectric device, and sealing method for piezoelectric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive brazing filler metal which are relatively low in melting point, easily handled, excellent in strength and adhesiveness, and to provide a piezoelectric device. <P>SOLUTION: The composition ratio (Au (wt.%), Ag (wt.%), Sn (wt.%)) is in a region surrounded by a point A1 (41.8, 7.6, 50.5), a point A2 (62.6, 3.4, 34.0), a point A3 (75.7, 3.2, 21.1), a point A4 (53.6, 22.1, 24.3), and a point A5 (30.3, 33.2, 36.6) in the ternary composition diagram of Au, Ag and Sn. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a brazing material, a piezoelectric device, and a method for sealing a piezoelectric device.

A piezoelectric device such as a piezoelectric vibrator or a piezoelectric transmitter generally has a structure in which a piezoelectric vibrating piece is hermetically sealed in a package (see, for example, Patent Documents 1 and 2). In the piezoelectric device described in Patent Document 1 or 2, a metal ball made of a low melting point metal such as Au—Sn or Au—Ge is arranged in a sealing hole formed on the outer surface of the package and communicating with the inside, and a laser beam is placed on the ball. Is melted and cured while the sealing hole is closed, thereby sealing the piezoelectric vibrating piece.
JP 2002-009577 A JP 2003-158439 A

  Table 1 shows examples of alloys that can be applied as a brazing filler metal. As will be described in detail below, alloys that are currently known have not yet been able to satisfy brazing properties (sealing properties), economy, and the like at the same time.

No. 1 is a Sn—Pb solder having a eutectic composition, but this combination does not meet the conditions because the melting point is low and it does not endure solder reflow. In addition, since Pb is included, the load on the environment is high, and use must be refrained.
No. No. 2 Au—Sn has a melting point of 280 ° C., and is in the usable range although it is located at the lower limit in the above melting point range. However, Au is disadvantageous in terms of price because it contains 80% by weight.
No. No. 3 Au—Ge has excellent technical conditions, but the Au content is 88%, which is similarly disadvantageous from the viewpoint of price.
No. The Au-Sb No. 4 can slightly reduce the Au content as compared with Au-Sn and Au-Ge, but it is mechanically extremely fragile and is subject to great restrictions in actual use.

  The present invention has been made in view of the above-described problems of the prior art, and provides a brazing material and a piezoelectric device that are easy to handle with a relatively low melting point, excellent in strength and adhesion, and inexpensive. It is aimed.

In order to solve the above problems, the brazing material of the present invention has a composition ratio (Au (wt%), Ag (wt%), Sn (wt%)) in a ternary composition diagram of Au, Ag, and Sn. Point A1 (41.8, 7.6, 50.5), Point A2 (62.6, 3.4, 34.0), Point A3 (75.7, 3.2, 21.1), Point A4 (53.6, 22.1, 24.3) and the region surrounded by the point A5 (30.3, 33.2, 36.6).
In the present invention, by defining the region as described above and limiting the composition range, it is possible to obtain the same characteristics as the sealing material while reducing the Au content as compared with the conventional case.

The composition ratio (Au (wt%), Ag (wt%), Sn (wt%)) is point B1 (47.8, 14.2, 38. 0), point B2 (62.7, 5.5, 31.8), point B3 (60.2, 12.6, 27.1), point B4 (49.3, 21.0, 29.8) , In a region surrounded by.
In the present invention, by limiting to such a composition range, it is possible to obtain a brazing material that can obtain better heat resistance in addition to the effects obtained in the above composition range.

  It is good also as a structure which forms a solid solution with Au or Ag, and contains 0.1 wt% or more and 3% or less of a metal element whose bulk melting point is 400 degreeC or more. With such a structure, the melting point and hardness of the brazing material are increased, and a brazing material having excellent heat resistance and mechanical strength can be obtained.

The metal element is preferably Ni, Pd, or Pt. The metal element is preferably a plurality of metal elements selected from Ni, Pd, and Pt, and the total content of the metal elements is preferably 0.1 wt% or more and 3 wt% or less.
Thus, the metal element may be added alone or a mixture of a plurality of elements may be added. In any addition form, the melting point and hardness can be increased, and heat resistance and mechanical strength can be improved.

  In the present invention, the brazing material described above may be formed into a ball shape. Such a brazing material is useful for sealing narrow sealing holes.

The piezoelectric device according to the present invention is a piezoelectric device in which a piezoelectric vibrating piece is hermetically sealed in a cavity of a package, and the sealing hole that communicates the inside of the cavity with the outside of the package is described above. It is sealed using the brazing material of the present invention.
According to this sealing method, the sealing hole is sealed by the brazing material of the present invention, which can provide good sealing performance and can be provided at low cost, so that a piezoelectric with a good hermetic sealing structure is formed. Devices can be provided at low cost.

The piezoelectric device sealing method of the present invention is a piezoelectric device sealing method in which a piezoelectric vibrating piece is hermetically sealed in a package cavity, and the inside of the cavity communicates with the outside of the package. A sealing material formed by forming the brazing material of the present invention into a spherical shape is disposed with respect to the sealing hole, and the sealing hole is closed by irradiating the sealing material with laser light. It is characterized by that.
According to this sealing method, the sealing hole is sealed by the brazing material of the present invention, which provides good sealing performance and can be provided at a low cost, so that a piezoelectric with a good hermetic sealing structure is formed. Devices can be manufactured at low cost.

  The electronic component of the present invention is characterized by having an airtight sealing structure sealed using the brazing material of the present invention described above. According to this configuration, by using the brazing material of the present invention, it is possible to provide an electronic component having an airtight sealing structure with excellent sealing performance at a low cost.

(First embodiment)
[Au-Ag-Sn ternary alloy brazing material]
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a ternary composition diagram of Au, Ag, and Sn, which are the main constituent elements of the brazing filler metal according to the present invention. Table 2 shows the compositions, melting points, and the like of points A1 to A5, points B1 to B4, point C1, and points X1 to X6 shown in FIG.

The brazing material of the present embodiment is characterized by being in a region surrounded by points A1 to A5 indicated by black circles in the ternary composition diagram shown in FIG. Specifically, the composition ratios (Au (wt%), Ag (wt%), Sn (wt%)) are point A1 (41.8, 7.6, 50.5), point A2 (62.6). , 3.4, 34.0), point A3 (75.7, 3.2, 21.1), point A4 (53.6, 22.1, 24.3), point A5 (30.3, 33). .2, 36.6).
In the present invention, by defining the region as described above and limiting the composition range, it is possible to obtain the same characteristics as the sealing material while reducing the Au content as compared with the conventional case.
Further, in the present invention, as shown in FIG. 1, the Au content is 30.3 wt% or more and 75.7 wt% or less, and the Au content is reduced as compared with the Au alloy shown in Table 1 above. Can do.
In particular, if the Au content is in the range of 40 wt% or more and 60 wt% or less, the cost reduction effect is remarkable with respect to the conventional Au—Sn or Au—Ge brazing material. Further, in such an Au content range, a relatively wide range of Ag content and Sn content is allowed as shown in FIG. 1, so that it is easy to change the composition ratio according to the heat resistance condition and the like.

Further, the brazing material of the present invention is characterized by being in a region surrounded by points B1 to B4 indicated by double circles in the ternary composition diagram shown in FIG. Specifically, the composition ratios (Au (wt%), Ag (wt%), Sn (wt%)) are point B1 (47.8, 14.2, 38.0), point B2 (62.7). 5.5, 31.8), point B3 (60.2, 12.6, 27.1), and point B4 (49.3, 21.0, 29.8). is there.
In the present invention, by limiting to such a composition range, it is possible to obtain a brazing material that can obtain better heat resistance in addition to the effects obtained in the above composition range.

  Regarding binary and ternary alloy materials, many melting points and metal structures have already been investigated at the academic level. There have also been many researches and practical products on tin / lead solder and lead-free solder. Most of them are materials having a melting point of around 200 ° C. As in the present invention, there are very few brazing material investigations in a temperature range that can withstand the solder reflow process.

  In the present invention, the range of components that can be used as a brazing material that can withstand solder reflow processing was first examined. For materials used as brazing materials for electronic parts, it is necessary to sufficiently consider strength, wettability, corrosion resistance, heat resistance, and the like.

  With regard to heat resistance, the first requirement is that it withstands the soldering temperature in the electronic component mounting stage and does not melt itself. Since the temperature of solder reflow is generally in the range of about 250 ° C. to 270 ° C., the melting point of the brazing material itself needs to be approximately 280 ° C. or higher.

  On the other hand, although the maximum temperature of the melting point of the brazing material depends on the heat resistance temperature of the applied electronic component, the upper limit is about 500 ° C. in consideration of preventing thermal deterioration of the element itself and the difficulty of brazing. It is. Therefore, the melting point of the brazing material is required to be in the range of 280 ° C to 500 ° C. In order to protect the environment, the use of harmful metals such as lead and cadmium must also be avoided.

  Table 2 shows examples of Au—Ag—Sn ternary alloys verified under various conditions including the composition range according to the present invention. No. in Table 2 1 to 5 correspond to points A1 to A5. 6 to 9 correspond to points B1 to B4. 10 corresponds to the point C1. No. 11 to 16 correspond to conditions (points X1 to X6) that deviate from the composition range according to the present invention verified for comparison.

As shown in Table 2, No. included in the composition range according to the present invention. Under the conditions of 1 to 10, all the melting points are in the range of 280 ° C. to 500 ° C., which has both good heat resistance in the mounting process and good wettability (sealing property) in the sealing process It has become.
Furthermore, No. corresponding to the area surrounded by the points B1 to B4. In 6-10, since the solidus temperature is 346 ° C. or higher and the liquidus temperature is 350 ° C. or higher, the solder flow process using lead-free solder having a higher melting point than Sn—Pb solder. Can withstand even more.

On the other hand, No. not included in the composition range according to the present invention. No. 11 to No. 16 For Nos. 11, 14, and 15, the melting point (solidus temperature) is below 280 ° C., there is no resistance to the solder reflow temperature, and it is assumed that it will melt itself in the solder reflow process. If used in the vacuum, there is a risk of breaking the vacuum.
No. Regarding 12, 13, and 14, the melting point (liquidus temperature) exceeds 500 ° C., and when used for vacuum sealing of a piezoelectric device, the material does not melt sufficiently in the sealing step by laser light irradiation. There is a possibility that the wettability is lowered and sufficient vacuum sealing cannot be performed.
In particular, no. No. 14 has a very wide solidification temperature range of 239 ° C. to 527 ° C. and is not suitable as a brazing material.
In addition, No. Although 16 is a generally known Au-Ag-Sn alloy, it has a liquidus temperature of 500 ° C. or higher and cannot be suitably used as a brazing material.

  The inventor has also verified the sealing performance and mechanical strength of the alloys having the respective composition ratios shown in Table 2 when used as a sealing material for a package of a piezoelectric device. When the material of the composition shown in 1 to 10 is used as a sealing material, it has been confirmed that good sealing can be performed in any case. That is, the brazing material according to the present invention has a low Au content and can be used as a low-cost and high-performance brazing material.

  The specific configuration of the piezoelectric device and the sealing method thereof are described with reference to FIG. 2 in the “piezoelectric device” section below. In this example, the material of each composition is formed into a spherical shape with a diameter of about 0.4 mm by the gas atomizing method, placed in the sealing hole of the package, then irradiated with laser light and solidified after melting and used as a vacuum sealing material did.

[Piezoelectric devices]
Next, a configuration of a piezoelectric device that can suitably use the brazing material of the present invention as a sealing material and a sealing method thereof will be described.
FIG. 2A is a schematic plan view of a surface-mounted crystal resonator that is an example of a piezoelectric device. FIG. 2B is a cross-sectional view corresponding to FIG. FIG.2 (c) is explanatory drawing of the sealing process using a brazing material.

  The crystal resonator shown in FIG. 2 includes a package 13 including a base 11 made of a ceramic material and a lid 12 and a tuning fork type crystal vibrating piece 14 hermetically sealed inside the package 13. The base 11 is formed by integrally laminating and joining a bottom plate portion 15 made of a generally rectangular ceramic thin plate and a generally rectangular frame body portion 16 formed by laminating a plurality of ceramic thin plates having different shapes. 14 is formed in a thin box shape that defines a cavity 17 for accommodating 14.

  The quartz crystal vibrating piece 14 is cantilevered to a connection electrode 19 formed on the bottom surface of the cavity 17 by a conductive adhesive 18 at a base end portion 14a thereof in a substantially horizontal manner. A recess 20 is formed on the bottom surface of the cavity 17 at a position corresponding to the vibrating arm tip 14 b of the crystal vibrating piece 14. The concave portion 20 functions as a relief for the vibrating arm tip portion 14b not to collide with the base 11 even if the vibrating arm of the quartz crystal vibrating piece 14 swings downward due to an external impact or the like.

  The lid portion 12 is formed of a rectangular thin plate made of an insulating material such as glass or ceramics, and is airtightly joined to the upper end surface of the base 11 with a low melting point glass 22. When a tuning fork type crystal vibrating piece is mounted, it is preferable to use a transparent glass lid so that the frequency can be adjusted by irradiating laser light from the outside of the package 13 after the lid portion 12 is joined.

  The base 11 is provided with a sealing hole 23 that allows communication between the outside of the package 13 and the inside of the cavity 17. The sealing hole 23 includes a circular outer hole 24 that opens to the bottom surface of the base 11 and a circular inner hole 25 that opens to the bottom surface of the cavity 17. The outer hole portion 24 and the inner hole portion 25 are through holes formed in a thin ceramic plate constituting the bottom plate portion 15 and the frame body portion 16, respectively. The outer hole portion 24 and the inner hole portion 25 are formed at concentric positions in plan view as shown in FIG. 2A, and the outer hole portion 24 is formed with a larger diameter than the inner hole portion 25. Has been.

  The outer hole 24 of the sealing hole 23 is closed with a sealing material 27 made of a brazing material of Au—Ag—Sn alloy according to the present invention, and the inside of the package 13 is hermetically sealed. A metallized portion 28 (see FIG. 2C) for increasing the adhesion of the sealing material 27 is formed on the inner peripheral surface of the outer hole portion 24.

In the crystal resonator having the above-described configuration, the sealing hole 23 is sealed by, for example, the following process.
In the step of sealing the sealing hole 23 with the sealing material 27, first, the crystal vibrating piece 14 is mounted on the base 11 and the lid portion 12 is joined to the upper surface of the base, and then the package 13 is attached to the bottom surface (bottom plate portion 15 Place in a vacuum atmosphere with the side facing up. At this time, a metallized portion 28 is formed inside the outer hole portion 24 as shown in FIG.

  The metallized portion 28 can be formed by a method of forming a metal film by screen printing and forming a plating layer on the metal film, or a known film forming method such as vapor deposition or sputtering. The metallized portion 28 is also formed on the surface of the step 29 formed at the connection portion between the outer hole portion 24 and the internal passage 26.

  Next, as shown in FIG. 2 (c), a metal ball 30 formed using an Au—Ag—Sn alloy, which is a brazing material according to the present invention, is formed in the outer hole 24 of the package 13 that faces upward. Put in. As shown in the drawing, the metal ball 30 has a particle size that is placed on a step 29 formed around the inner hole portion 25 located in the outer hole portion 24. For example, the metal ball 30 has a particle size of about 0.4 mm. A molded one is used.

  Next, when the metal ball 30 on the step 29 is irradiated with a laser beam, the molten metal material spreads over the entire inside of the outer hole 24 and is completely closed and solidified. Since the inner peripheral surface of the outer hole 24 and the step 29 are metalized, good adhesiveness between them and the sealing material 27 can be obtained, so that the inside of the package can be reliably hermetically sealed.

  In the present invention, the brazing material according to the present invention described above is used as the sealing material 27 for closing the sealing hole 23. As described above, the present inventor performs brazing using materials having respective compositions described in Table 2 and evaluates the sealing property and the like. As a result, as shown in Table 2, the composition range No. 1-No. It has been confirmed that good sealing properties can be obtained for ten materials. According to the present invention, since a brazing material having a smaller Au content than that of a conventional brazing material is used, a piezoelectric device can be provided at a low cost.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.
In the present embodiment, a further effect can be obtained by adding a fourth component to the brazing material having the ternary composition. Table 3 shows examples. In this example, no. Ten materials (53.2Au-14.6Ag-32.2Sn) are used as reference materials, and various metal elements are added to the results to verify the results.

  In the experiment whose results are shown in Table 3, No. For 10 materials, the basic composition ratio of Au—Ag—Sn was not changed and Ni, Pd, and Pt were changed in the range of 0.1% to over 3% as the fourth component. No. in Table 3 1 is the one to which the fourth component is not added (No. 10 in Table 2).

In the component notation in Table 3, Au-Ag-Sn mixed earlier is regarded as one component, and is described as a ratio with the fourth component. For example, no. In the case of 2, Ni: 0.05% is written, but the basic Au—Ag—Sn ratio is about Au: Ag: Sn = 53.2: 14.6: 32.2 by weight ratio. In contrast, 0.05% by weight of Ni (fourth component) is added.
“Mix” in the composition column in Table 3 is a mixture of Ni, Pd, and Pt at a ratio of 1: 1: 1 to form a fourth component, which is added to the reference material at the indicated weight ratio. Yes.

  As shown in Table 3, when any of Ni, Pd, and Pt is added as the fourth component, the liquidus temperature and the hardness increase with almost the same tendency. The hardness increases in this way in the sealing material in which Ni, Pd, and Pt added as the fourth component form a hard solid solution with Au or Ag, and this solid solution is solidified after melting the brazing filler metal. It is thought that it is because it precipitates.

In addition, the liquidus temperature is rapidly increased by the addition of the fourth component, and when the addition amount exceeds 3%, it reaches 500 ° C., and there is a possibility that the melting by the laser beam may be insufficient. It is unsuitable as a brazing material. On the other hand, when the addition amount is less than 0.1%, there is little change in hardness, which does not contribute to improvement in strength.
Therefore, the addition of the fourth component is desirably 0.1% or more and 3% or less for any material. In addition, even when several kinds of the fourth component are mixed, the change in liquidus temperature and hardness is the same tendency as when added alone, and also when mixed and added, the total is 0.1% or more, 3% or less is desirable.

Furthermore, the present inventor also verified the effect of the brazing material to which the fourth component of this example was added by using it for sealing a piezoelectric device in the same manner as the materials shown in Table 2. Specifically, as in the first embodiment, each material shown in Table 3 was formed into a spherical shape having a diameter of 0.4 mm by a gas atomizing method, and laser sealing was performed with a crystal package shown in FIG.
When the sealing property (wetting property) of the obtained sample was evaluated, the Ni addition amount exceeded 3%. No. 7, the amount of Pt added exceeds 3%. No. 14 and the amount of mixture added exceeds 3%. It was confirmed that good sealing can be performed except for 20 materials.

  In addition, although this embodiment demonstrated the addition result of the 4th component about the reference material (No. 10 material of Table 2) mentioned above, according to the experimental result by this inventor, it concerns on this invention as described previously. It has been confirmed that the same effect can be obtained when the fourth component is added to the material in the composition range.

The ternary composition figure which shows the composition range in the brazing material which concerns on this invention. The figure which shows the structure and sealing method of the piezoelectric device which concern on this invention.

Explanation of symbols

  11 Base, 12 Lid, 13 Package, 14 Crystal vibrating piece, 14a Base end, 14b Vibration arm tip, 15 Bottom plate, 16 Frame, 17 Cavity, 18 Conductive adhesive, 19 Connection electrode, 20 Recess , 22 Low melting point glass, 23 Sealing hole, 24 Outer hole part, 25 Inner hole part, 27 Sealing material (brazing material), 28 Metallized part, 29 Step, 30 Metal ball.

Claims (7)

The composition ratio (Au (wt%), Ag (wt%), Sn (wt%)) is
In the ternary composition diagram of Au, Ag, and Sn,
Point A1 (41.8, 7.6, 50.5),
Point A2 (62.6, 3.4, 34.0),
Point A3 (75.7, 3.2, 21.1),
Point A4 (53.6, 22.1, 24.3),
Point A5 (30.3, 33.2, 36.6)
A brazing material characterized by being in an area surrounded by The composition ratio (Au (wt%), Ag (wt%), Sn (wt%)) is
In the ternary composition diagram of Au, Ag, and Sn,
Point B1 (47.8, 14.2, 38.0),
Point B2 (62.7, 5.5, 31.8),
Point B3 (60.2, 12.6, 27.1),
Point B4 (49.3, 21.0, 29.8),
A brazing material characterized by being in an area surrounded by In the brazing material according to claim 1 or 2,
A brazing material characterized by containing a metal element which forms a solid solution with Au or Ag and has a bulk melting point of 400 ° C. or more and 0.1 wt% or more and 3% or less. In the brazing material according to claim 3,
The brazing material, wherein the metal element is any one of Ni, Pd, and Pt. In the brazing material according to claim 3,
The brazing material, wherein the metal element is a plurality of metal elements selected from Ni, Pd, and Pt, and the total content of the metal elements is 0.1 wt% or more and 3 wt% or less. A piezoelectric device in which a piezoelectric vibrating piece is hermetically sealed in a cavity of a package,
6. A piezoelectric device, wherein a sealing hole that communicates the inside of the cavity and the outside of the package is sealed using the brazing material according to claim 1. A piezoelectric device sealing method in which a piezoelectric vibrating piece is hermetically sealed in a package cavity,
A sealing material formed by forming the brazing material according to any one of claims 1 to 5 in a spherical shape with respect to a sealing hole communicating the inside of the cavity and the outside of the package,
A sealing method for a piezoelectric device, wherein the sealing hole is closed by irradiating the sealing material with laser light.

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