JPH11284485A - Piezoelectric resonator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent solder flow at solder mounting by providing a connection pattern on the tip of a leader electrode bypassing at a side face and/or an end face of a rectangular plate, placing the connection pattern at or near a corner of the rectangular plate on a side opposite to a major side with an exciting electrode of the leader electrode and soldering the pattern with a terminal conductor. SOLUTION: A extraction electrode 21 of a front side exciting electrode 2 is connected to a connection pattern 24 provided to a corner of other major side, via a side face bypass section 22 and an end face bypass circuit section 23. An exciting electrode 3 is similarly connected to a connection pattern 34 at a corner of the opposite major side. The connection patterns 24, 34 are connected and supported at faces opposite to each other in the crystal chip 1 by lead wires of a crystal resonator and solder materials. Through the configuration above, wherein surface diffusion of Pb along an Ag film and particle diffusion of Sn result from diffusion via three orthogonal planes, the diffusion speed is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a structure of a quartz oscillator. More specifically, the present invention relates to a shape and a structure of an electrode including a support structure of a vibrator for preventing diffusion of solder in a quartz vibrator supported by solder.

[0002]

2. Description of the Related Art Piezoelectric vibrators, particularly quartz vibrators, and especially AT-cut thickness-sliding quartz vibrators, have a high frequency stability and have a wide range of uses as relatively inexpensive oscillation sources. For example, it is used as a reference signal source for video cameras, car tuners, mobile phones, personal computers and other electronic devices. These quartz resonators are usually used at room temperature, but may be used in a high temperature environment for a long time.

FIG. 4A shows an example of the structure of the inside of a container of a quartz resonator which has been widely used in the past. Reference numeral 1 denotes a quartz piece, which is, for example, a rectangular AT-cut quartz plate. At the center of the main surface corresponding to the front (surface), there is an excitation electrode 2 on the front side,
Then, an extraction electrode 21 is led out, and a tip portion thereof is a connection pattern 24 having a huge shape. These electrodes are formed in a film at a time by evaporating Ag, for example, by mask.
Reference numeral 5 denotes an airtight terminal, which penetrates through the inner insulating glass part.
Lead wire 51 and connection pattern 24
Surface is soldered. That is, the means for supporting the crystal blank 1 and electrically connecting it to the outside is the solder 4. The portion where the solder material is laid is indicated by hatching.
(The same applies to the other figures.)

The crystal resonator has a structure which is completely axially symmetric with respect to a vertical axis (not shown) passing through the center of the crystal blank 1 and has the same electrode shape. Therefore, 180
The rear view obtained by rotating by ° is exactly the same as FIG.
Although not shown again, the connection pattern 34 at the tip of the back extraction electrode 31 drawn from the back excitation electrode 3 provided on the main surface corresponding to the back surface (back surface) is connected to the other lead wire 5.
2 is soldered. Note that the extraction electrodes 21 and the connection patterns 24 are provided above and below the rectangular plate-shaped crystal blank 1 according to a well-known technique for eliminating the need to distinguish between the upper and lower sides when mounting the crystal blank 1.

In FIG. 4, the extraction electrode 21 is bent,
The reason for this is that the solder material 4 piled on the connection pattern 24 is melted when the crystal blank 1 is mounted, flows on the extraction electrode 21 and reaches the excitation electrode 2 as shown in FIG. This is to prevent a long road.
[(B) is a diagram showing the diffusion process of the solder material as described later. In the case of molten solder, if the amount is too large, it may flow to the vicinity of A along the same route. Since the amplitude of the crystal blank 1 is large in a part of the excitation electrode, the resonance frequency or the Q value is adversely affected if solder, which is a material having a large internal friction, is located in or near the part.

[0006]

Although the solder flow during mounting can be substantially prevented by the above-mentioned conventional structure, there is another problem. That is the diffusion phenomenon of the solder material when used in a high temperature environment. For example, 125 ° C as a high temperature environment test,
A 1000 hour heat resistance test is performed. First, among Pb and Sn constituting the solder material 4, the speed at which Pb diffuses on the surface of Ag, which is an electrode film, is high, and proceeds on the extraction electrode 21 as shown by the arrow in FIG. Then, the diffusion front shifts as A → B → C with time, and almost 100% of the excitation electrode is covered under the above temperature and time conditions.

However, the total mass of Pb diffused is relatively small. For example, in the case of a crystal blank 1 having a resonance frequency of 20 MHz, several p
Only changes in pm. Therefore, even if the specification of the general product is, for example, ± 50 ppm, there is almost no problem, but a medium (for example, ± 20 ppm) or a product requiring higher precision is more likely to be defective.

Next, there is a phenomenon that Sn diffuses at the grain boundary in the Ag film. Since the diffusion speed is low, the diffusion front rarely reaches the excitation electrode under the above conditions. However, depending on the state of the Ag film, the diffusion may progress to several% of the excitation electrode area. However, the total mass of the diffusion is large, and the frequency shift when reaching the excitation electrode may reach several tens to several hundreds ppm with a 20 MHz quartz oscillator.

Also, the prevention of solder flow during solder mounting of the crystal blank 1 is not 100% perfect in the conventional example. Even if the solder flow does not reach the excitation electrode, the total amount is large. Depending on the variation of the heating condition, the influence is exerted. For example, the frequency of the spurious vibration moves and coupling with the main vibration occurs, which may cause inconvenient phenomena such as a jump in the frequency temperature characteristic of the product, an increase in the CI value, and a malfunction at a low drive level.

[0010] One of the prior arts is to use a conductive adhesive instead of solder to mount the crystal blank, which eliminates the problem of solder diffusion at high temperatures.
It is difficult to stabilize the yield and characteristics by keeping the bonding area constant and increasing the number of assembling steps as compared to the solder mount, so using the solder mount after solving the diffusion problem is more costly than using the adhesive mount. desirable.

An example of another conventional structure which is considered to be similar to the present invention will be introduced. In FIG. 5, (a) is a front view of a second prior art quartz oscillator (before mounting a sealing tube) disclosed in JP-A-4-3611, (b) is a rear view thereof, and (c) is a rear view thereof. FIG. 1 is a front view of a third prior art quartz oscillator (before mounting a sealing tube) disclosed in Japanese Utility Model Laid-Open No. 4-36329, and FIG.

In FIGS. 5A and 5B showing a second conventional example, excitation electrodes 2 and 3 on each plate surface (main surface) of a crystal blank 1 are shown.
The extraction electrodes 21, 31 bypass the upper and lower end surfaces of the crystal blank 1 and reach the surface on the opposite side (back side) of the main surface where the excitation electrode is located. The electrode film thickness is exaggerated to clearly show the end face detours 23 and 33. Lead wires 51 and 52 are connected to these.

In this conventional example, since both lead wires are located on the same main surface of the crystal blank 1, the extraction electrode 31 between the connection pattern 34 of the lead wire 52 and the excitation electrode 3 is used.
Is long because it passes through the end face detour 33, but since the connection pattern 24 of the lead wire 51 is in front of the end face detour 24 and the length of the extraction electrode 21 between the excitation electrode 2 and the connection pattern 24 is extremely short. When soldering is performed in the vibrator structure, the problem of movement or diffusion of the solder material cannot be avoided. The above-mentioned document which discloses this conventional example describes that "conduction is achieved by applying a conductive paste".

In FIGS. 5C and 5D showing a third conventional example, the extraction electrodes 21 and 31 from the excitation electrodes 2 and 3 on each plate surface of the crystal blank 1 bypass the side surfaces of the crystal blank 1. Then, it has reached the surface on the opposite side (back side) of the main surface where the excitation electrode is located. The electrode film thickness is exaggerated to clearly show the detour. Lead wires 51 and 52 are connected to these.

Since this embodiment also has a structure in which both lead wires are located on the same main surface of the crystal blank 1, the path of the extraction electrode 31 between the joint 34 of the lead wire 52 and the excitation electrode 3 is Although it is distant because it passes through the side surface detour portion 32, since the connection pattern 24 of the lead wire 51 is in front of the side surface detour portion 22, the distance between the extraction electrode 21 and the excitation electrode 2 is extremely short, and soldering connection is performed. In such a case, the problems of solder flow and diffusion cannot be avoided.

In view of the above findings, it is an object of the present invention to provide a structure of a piezoelectric vibrator in which diffusion of a solder material in a high-temperature environment is delayed so as not to cause a practical problem, in addition to preventing flow during solder mounting. I do.

[0017]

For that purpose, the piezoelectric vibrator of the present invention has the following features. (1) An extraction electrode is derived from each of two excitation electrode films provided on each main surface of the rectangular plate-shaped vibrator, and each of the extraction electrodes bypasses a side surface and / or an end surface of the rectangular plate. A connection pattern is provided at the tip of the connection electrode, and the connection pattern is located at a substantially corner of a rectangular plate on a main surface opposite to a main surface on which the excitation electrode from which the extraction electrode is extracted is located. Solder to the terminal conductor in the pattern.

(2) Further, a part of each of the extraction electrodes is covered with a film of a material which is hardly wetted by solder.

(3) 2 provided on each main surface of the rectangular plate-shaped vibrator
An extraction electrode is led out from each of the two excitation electrode films, and a connection pattern formed at the tip of the extraction electrode is provided on the end face side of the crystal unit, and the extraction electrode is covered with a film of a material that is difficult to wet with solder. Being done.

(4) The extraction electrode is divided, and the divided part is connected by a film made of a material that is conductive and hard to wet with solder.

(5) The film of the material which is hardly wetted by the solder is 2
The piezoelectric vibrator is provided on both of the two extraction electrodes and is provided so as to be concentrated on only one main surface of the piezoelectric vibrator.

(6) The extraction electrode is mainly made of Ag, and the film of a conductive material that is hardly wetted with solder is made of Cr or Ti.

[0023]

FIG. 1 and FIG. 2 show an embodiment of the present invention. Corresponding portions in the embodiment of the present invention and the conventional example are assigned common symbols, and no new description will be made. 1A to 1D show a crystal piece with an electrode used in the present embodiment, wherein FIG. 1A is a left side view, FIG. 1B is a front view and top and bottom views, and FIG. FIG. 3D is a rear view. FIG. 2A is a partial front view (with the sealing tube removed) of the crystal unit according to the present embodiment, and FIG. 2B is a sectional view taken along line XX. The thickness of each electrode is exaggerated. FIG. 1E is a partial enlarged view of a front view of a modification of the present embodiment.

FIGS. 1 (a) to 1 (d) and 2 (a),
In (b), the extraction electrode 21 of the front excitation electrode 2 passes through both the side surface detour portion 22 and the end surface detour portion 23, and the corner of the opposite main surface (the back side of the main surface on which the excitation electrode 2 is provided). Are connected to the connection pattern 24 provided in the first pattern. Excitation electrode 3
The same applies to the connection pattern 34 at the corner of the opposite main surface. The connection patterns 24 and 34 are lead wires 5 which are terminal conductors of the crystal unit as shown in FIG.
The crystal blanks 1 and 52 are connected and supported by the solder material 4 on the opposite surfaces of the crystal blank 1. Reference numeral 6 denotes a sealing tube for keeping the crystal blank 1 airtight, which is drawn by imaginary lines.

Considering the surface diffusion of Pb along the Ag film and the grain boundary diffusion of Sn in this configuration, both of them are diffusions passing through three orthogonal planes. It is much slower than diffusion in the same plane. Also, as shown in FIGS. 1 (b) and 1 (d), the shape of the extraction electrode is set as close to the end face of the crystal blank 1 as possible,
The shape is such that it is connected to the end surface detour, and the route is lengthened to further slow the diffusion. Of course, the effect of preventing the flow of the molten solder is also high. In addition, the diffusion path and conditions are not different between the two connection parts as in the other conventional examples.
Will be the same.

The reason why the detour portions of the electrode film are provided on both the side surface and the end surface of the crystal blank 1 is that the electrode film on the side surface and the end surface is formed simultaneously by using the same vapor deposition mask as that for forming the excitation electrode. In this case, the film is formed by oblique evaporation and the film thickness is relatively thin, so that the connection at the side surface, the end surface, or the ridge portion where the surface intersects is ensured.

As a result of the experiment according to the embodiment of the present invention, it was confirmed that the heat resistance test at about 125 ° C. for about 1000 hours had no practical problem. However, there is still a shortage given the environmental conditions that require ten times as much time. Fig. 1
The modification shown in FIG.

The modified example shown in FIG.
Is partially vapor-deposited on the solder with a metal material having poor wettability, such as Cr or Ti, to form a solder barrier film 25.
(Indicated by hatching and a frame with diagonal lines in a direction different from that of the solder 4; the same applies to other drawings). After deposition, the barrier material is heated and diffused into the Ag. The extraction electrode 31 on the opposite main surface (not shown) has the same structure.

The effect of simply adding the solder barrier film 25 on the extraction electrode is also effective.
(Angstrom) or more has a diffusion stopper effect, and at 1000 A or more, the effect is almost saturated and there is no change. Note that Ag, which is a main material of the electrode, has a thin Cr layer as an underlayer, but is not a solder barrier film of the present invention because it is deposited simultaneously with the same mask as Ag.

In this additional film formation, the mask for simultaneous vapor deposition of a large number of excitation electrodes is replaced with a mask having holes formed in the solder barrier film portion for the crystal blanks already aligned in the jig ( Alternatively, only the latter mask is required), so that the number of man-hours can be reduced. It is to be noted that if the slit 26 is provided at the position shown in the drawing to divide the extraction electrode and the electrical connection is made by utilizing the conductivity of the solder barrier film straddling the extraction electrode, the diffusion prevention is more perfect.

Next, another embodiment of the present invention will be described with reference to FIGS. (A) is a front view of the second embodiment, (b) is a rear view thereof, (c) is a front view of a modification of the second embodiment, and (d) is a rear view thereof. In the second embodiment, a method of forming a solder barrier film of Cr or the like is rationalized. In the example of FIG. 1E, the solder barrier film has to be formed by vapor deposition on both sides of a crystal piece. The configuration is intended to further reduce the number of man-hours by performing it on only one main surface.

The structure for that purpose is as follows.
Is also routed to the main surface on the front side, and on the front side of the crystal blank 1, one vapor deposition mask in which holes are separately formed on each of the front-side extraction electrode 21 and the wiring portion is provided. Place,
At the same time, solder barrier films are formed at two places (four places in the case of a leader line having a vertically symmetric pattern as shown). No barrier film is provided on the back surface.

In the shapes shown in FIGS. 3A and 3B, the distance from the connection pattern to the solder barrier film is almost equal, and it is desirable for the uniformity of solder diffusion.
In the shape of (d), the distances are unequal. However, on the other hand, the front and rear views of the electrode patterns (a) and (b) are different from each other, so that it is necessary to distinguish the front and back of the crystal blank 1 in the manufacturing process. However, the electrode patterns of (c) and (d) are used. Since the front view and the rear view are the same, there is an advantage that there is no need to judge them.

Next, a third embodiment of the present invention will be described. That is, a solder barrier film is applied to a conventional electrode as shown in FIGS. That is, for example, the case where the present invention is applied to the conventional example of FIG. 5 will be described with reference to FIG. 5. In each example of (a), (b) or (c) and (d), the connection pattern 24 on which the solder material 4 is piled up,
Since both are located on one main surface side of the crystal blank 1, one extraction electrode is long and the other extraction electrode is short.

Therefore, by covering at least a part or the whole of the shorter (preferably longer) extraction electrode with a solder barrier film, the diffusion of the solder material can be effectively prevented. Of course, the extraction electrode at the portion covered with the solder barrier film may be divided as shown in FIG.

Further, as a modification of the third embodiment, the longer lead-out portion of the lead-out electrode is shown in FIG.
If the solder barrier film 35 is provided on the same main surface as the connection pattern 34 as in the case of the extraction electrode 31 in (c) and the portion is provided with the solder barrier film 35, the solder barrier film (not shown) applied to the shorter extraction electrode ) Can be provided on the same main surface as above, and two (four in the case of a vertically symmetric pattern) solder barrier films can be concentrated on only one surface of the crystal blank 1. Moreover, in this case, it is easy to make the distance from the connection pattern to the solder barrier film substantially equal.

[0037]

According to the present invention, since the lead-out electrode of the excitation electrode is bypassed and soldered to the connection conductor on the other main surface, not only the flow of molten solder is prevented, but also
Since the diffusion speed of the material forming the solder can be sufficiently reduced, the high-temperature environment resistance of the quartz oscillator (more generally, a piezoelectric oscillator made of a piezoelectric crystal) is improved (the characteristics under high temperature for a long time). (Prevent change).

The effect is further enhanced by covering the electrode film on the solder diffusion path with a solder barrier film or by further dividing the electrode film covered with the solder barrier film. If a solder barrier film is applied,
A soldering support structure on one side of the crystal blank 1 can be employed without fear of solder diffusion.

[Brief description of the drawings]

1 (a) to 1 (d) show an electrode structure of a crystal blank according to a first embodiment of the present invention, wherein (a) is a left side view,
(B) is a front view and top and bottom views, (c) is a right side view,
(D) is a rear view. (E) is an enlarged view of a main part of an electrode structure of a quartz piece according to a modification of the first embodiment.

FIG. 2A is a partial front view showing the internal structure of the crystal unit according to the first embodiment of the present invention, and FIG.
It is -X sectional drawing.

3A is a front view of a crystal blank according to a second embodiment of the present invention, FIG. 3B is a rear view thereof, and FIG. 3C is a front view of a crystal blank according to a modification of the second embodiment. FIG. 3D is a rear view thereof.

FIGS. 4A and 4B are views showing the internal structure of a quartz oscillator of a first conventional example, wherein FIG. 4A is a front view and FIG. 4B is an explanatory view of a diffusion process of a solder material.

5A and 5B are diagrams showing the internal structure of another conventional crystal unit, and FIG. 5A is a front view of a second conventional crystal unit;
(B) is a rear view, (c) is a front view of a third conventional crystal unit, and (d) is a rear view.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 crystal blank 2 excitation electrode 21 extraction electrode 22 side detour 23 end detour 24 connection pattern 25 solder barrier film 26 slit 3 excitation electrode 31 extraction electrode 32 side detour 33 end detour 34 connection pattern 35 solder barrier film 4 Solder material 5 Hermetic terminal 51 Lead wire 52 Lead wire 6 Sealing tube

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Matsui 4107, Miyoshida, Miyoshida-machi, Kitasaku-gun, Nagano Prefecture Inside Miyota Co., Ltd. Inside the corporation

Claims (6)

[Claims] An extraction electrode is derived from each of two excitation electrode films provided on each main surface of a rectangular plate-shaped vibrator, and each of the extraction electrodes bypasses a side surface and / or an end surface of the rectangular plate. A connection pattern is provided at the tip of the extraction electrode, and the connection pattern is located at a substantially corner of a rectangular plate on a main surface opposite to a main surface on which the excitation electrode from which the extraction electrode is extracted is located. A piezoelectric vibrator characterized by being soldered to a terminal conductor in a connection pattern. 2. The piezoelectric vibrator according to claim 1, wherein a part of each of the extraction electrodes is covered with a film of a material that is difficult to wet with solder. 3. An extraction electrode is derived from each of two excitation electrode films provided on each main surface of a rectangular plate-shaped vibrator, and is provided on an end face side of the quartz crystal vibrator at a tip end of the extraction electrode. A piezoelectric vibrator, wherein a pattern is provided and the extraction electrode is covered with a film of a material that is hardly wetted by solder. 4. The extraction electrode according to claim 2, wherein the extraction electrode is divided, and the divided part is connected by a film made of a material which is conductive and hard to wet with solder.
Piezoelectric vibrator. 5. A film made of a material which is difficult to wet with solder is provided on both of the two extraction electrodes, and is provided so as to be concentrated only on one main surface of the piezoelectric vibrator. Any of the piezoelectric vibrators. 6. The extraction electrode is mainly made of Ag,
6. The piezoelectric vibrator according to claim 2, wherein the film made of a material that is difficult to wet with solder is made of Cr or Ti.