JPH0750545A - Crystal vibrator - Google Patents

Abstract

PURPOSE:To improve shock resistance by connecting a connection-use electrode land overlappingly to an extension electrode formed through extension from input output electrodes of a crystal chip and employing an aluminum for one of the both, thereby keeping its temperature characteristic in an excellent way. CONSTITUTION:The crystal vibrator is formed by sealing an At-cut rectangular crystal chip 1 into an enclosed package, the crystal chip 1 has an exciting electrode 3 on its both major sides, a lead electrode 4 is led out from both sides opposite to each other and the electrode 4 is folded back to the other major side to each other. Then an electrode land 9 whose width is wider than that of the lead electrode 4 is provided overlappingly on the lead electrode 4 at both outer circumferential parts of the crystal chip 1. However, the electrode land 9 is formed by a channel shape bridging over both the major sides. In this case, a 4-layer structure (CrAg mixing layer) of Cr, Cr-Ag, Ag, Cr is adopted sequentially to the exciting electrode 3 and the lead electrode 4 from the surface of the crystal. Furthermore, the electrode land 9 is formed in Al single layer structure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field of application of a crystal unit, and in particular, an electrode structure and an adhesive for improving the frequency temperature characteristics (temperature characteristics) and impact resistance of the surface mounting type crystal unit. The coating method of.

[0002]

BACKGROUND OF THE INVENTION Quartz resonators are widely used as frequency and time reference sources in various electronic devices because of their excellent resonance characteristics. In recent years, there has been a great demand for surface mount devices such as resistors and capacitors, and since they are often used in dynamic environments in particular, products that have good impact resistance and maintain temperature characteristics. Is required.

[0003]

2. Description of the Related Art FIGS. 11A and 11B are views for explaining a conventional example of a crystal resonator for surface mounting. FIG. 11A is a sectional view and FIG. 11B is a plan view of a crystal piece. The crystal unit is formed by enclosing the crystal piece 1 in the closed container 2. The crystal piece 1 has, for example, a rectangular shape and is AT-cut in a thickness-shear vibration mode. Opposing excitation electrodes 3 are formed on both main surfaces, and lead electrodes 4 extend in opposite directions. The extraction electrode 4 is folded back to the other main surface at each end. The closed container 2 is formed by covering a concave container body 5 having a laminated structure with a cover 6. The container body 5 is made of ceramic, a metal ring 7 is provided on the surface thereof, and they are joined by seam welding. The container body 5 has stepped portions on the inner walls on both end sides, and the outer peripheral portions of both ends of the crystal blank 1 are held by a conductive adhesive (not shown).

[0004]

However, in the crystal resonator having the above-described structure, the outer peripheral portions of both ends of the crystal piece 1 are fixed to each other, that is, both ends are held. Therefore, due to the contracting force when the adhesive is cured, strain (stress) is generated in the crystal piece 1, particularly in the length direction. As a result, the temperature sensitivity is deteriorated particularly due to the stress sensitivity characteristics, and it is difficult to put it into practical use. For this reason, in general, only one end of the crystal blank 1 is held and the other end is set as a free end (no conductive adhesive is applied) to prevent generation of stress in the length direction. "Figure 12 (abc)". Reference numeral 8 in the figure is a conductive adhesive. However, even if the one end is held, if the entire area of the one end is fixed as the application area of the adhesive agent 8, stress is generated in the width direction in FIG. 12 (a), and the crystal blank 1 is damaged. To do. Further, in the case of "part (b) of the same figure" where only a part of one end is fixed in a point manner, the connection strength is insufficient and the crystal blank 1 is detached upon impact, causing damage or the like as described above. From this, the extraction electrode 4 is provided in the width direction of the end portion, and both sides of the one end portion are dot-held as the adhesive 8 application region (FIG. 7C). However, even in this case (holding both sides at one end),
Since both sides in the width direction are basically fixed ends, the crystal piece 1 is distorted particularly in the width direction. In any case of holding one end, the other end, which is a free end, swings up and down, resulting in damage to the crystal piece 1 at that portion and weakening of the joining strength of the one end. Therefore, there is a problem in that it exhibits impact resistance.

[0005]

Basically, the present invention focuses on the fact that holding both ends ensures more stable holding of the crystal piece and improves the shock resistance such as breakage. It was made paying attention to the electrode structure and the adhesion method to achieve,
The purpose is to maintain both ends, firstly to maintain good temperature characteristics, and secondly to improve impact resistance.

[0006]

According to the present invention, an electrode land having a width wider than that of the extraction electrode is superposed on an extraction electrode extending to the outer peripheral portions of both ends of a crystal piece, and the extraction electrode and the electrode land are formed of different metals. The use of either one as Al is the solution for the first purpose. According to the present invention, a conductive adhesive is provided on both sides of the electrode land, the electrode land is located inside the electrode land on one side, and the electrode land and the quartz piece are located on the other side, and Fixing the piece on the substrate is a solution for the second purpose.
Hereinafter, one embodiment of the present invention will be described together with its operation.

[0007]

[First Embodiment] FIG. 1 is a view for explaining an embodiment of the present invention, particularly an electrode structure diagram of a crystal resonator. It should be noted that the description of the same parts as those of the previous conventional example is omitted. The crystal resonator is formed by enclosing the AT-cut rectangular crystal piece 1 in a hermetically sealed container, as in the conventional example. The crystal piece 1 has the excitation electrodes 3 on both main surfaces, the extraction electrodes 4 extend to both ends in opposite directions, and are folded back to the other main surface. Further, as is apparent from the drawing, in the present invention (embodiment), the electrode lands 9 larger than the width of the extraction electrode 4 are formed at the outer peripheral portions of both ends of the crystal piece.
Are superposed on the extraction electrode 4. However, the electrode land 9
Is formed in a U shape across both main surfaces at the outer peripheral portions of both ends. In this example, the excitation electrode 3 and the extraction electrode 4 have a four-layer structure of Cr, Cr-Ag, Ag, and Cr (hereinafter referred to as a CrAg mixed layer) sequentially from the crystal surface. The electrode land 9 has a single layer structure of Al. Both are formed by vapor deposition. The outer shape of the crystal piece 1 is 5 mm in length (z ′ axis direction), 2.5 mm in width (x axis direction), and thickness (y ′).
The target was about 80 μm (21 MHz) in the axial direction. When the crystal piece 1 having such an electrode structure was fixed on the substrate while holding both ends and the temperature characteristics were measured, good results were obtained. However, the adhesive 8 was applied to the central portion of the electrode land (FIG. 2). That is, as shown in FIG. 3, in the conventional case (curve B), the curve becomes linear with a deviation from the original cubic curve, but in the present embodiment (curve B), the characteristic close to the original cubic curve is maintained. did it. However, as the adhesive, for example, a urethane-based conductive adhesive having a pencil hardness of 2B or less was used. According to the estimation by the present inventor, in the conventional case, the contraction of the adhesive at the time of curing causes friction at the interface between the crystal element 1 and the extraction electrode and the excitation electrode 3 to cause tension (stress) on the surface of the crystal element 1. ) Is generated. Then, this tension has a great influence on the thickness shear vibration, and the original temperature characteristic is impaired by the stress sensitivity characteristic. On the other hand, in the present invention, even if the adhesive contracts, a slip phenomenon occurs at the interface between the extraction electrode 4 and the electrode land 9, and the tension generated on the surface of the crystal piece 1 is relaxed. That is, since the electrode land 9 is made of Al, an oxide film is formed between the electrode land 9 and the extraction electrode 4, and this oxide film weakens the bond between the two and promotes slippage. Therefore, it is considered that the electrode structure having the above-described structure does not cause distortion due to the tension particularly in the excitation portion, has little influence on the thickness shear vibration, and can obtain the original temperature characteristic.

However, with such a structure, the crystal impedance (hereinafter referred to as CI) has not been sufficiently satisfied even though the temperature characteristic is improved. That is, since an oxide film is likely to be formed on the surface of the electrode land 9 made of Al and then fixed by a conductive adhesive, the conductivity is deteriorated and a sufficient CI cannot be obtained. Less than,
A solution to this point will be described. FIG. 4 is a diagram for explaining a solution to this point, where FIG. 4 (a) is a plan view of a crystal piece and FIG. 4 (b).
Is a sectional view. That is, in this example, the electrode land 9
After forming the, the extraction electrode 4 is superposed on the electrode structure. Then, when the adhesive 8 was applied and fixed on the electrode land centering around the extraction electrode 4, good temperature characteristics and CI were obtained. That is, as described above, since the sliding phenomenon does not occur due to the action of the oxide film at the interface between the extraction electrode 4 and the electrode land 9, stress is not generated in the excited portion, so that the temperature characteristics can be maintained well. However, since the end portion of the extraction electrode 4 is fixed by the adhesive 8 rather than the above-mentioned one, it is considered that the slip phenomenon is more hindered than the above-mentioned case. And the adhesive 8
Directly contacts the extraction electrode 4 formed as a CrAg mixed layer, so that the conductivity is not impaired, and therefore the CI reduction is prevented. Although Cr has a large specific resistance and is likely to form an oxide film, Cr does not cause a conduction failure because it contains an Ag layer.

In the above electrode structure, the excitation electrode 3 and the extraction electrode 4 are made of a CrAg mixed layer, and the electrode land 9 is made of Al. On the contrary, the excitation electrode 3 and the extraction electrode 4 are made of Al, and the electrode land 9 is formed. May be a CrAg mixed layer. That is, even in this case, the temperature characteristic can be favorably maintained by the slip phenomenon as described above. And, at the time of fixation, Cr
Since a conductive adhesive is applied to the electrode lands 9 that are Ag-mixed layers, CI can be improved without causing conduction failure. However, since Al exists at the interface between the electrode land 9 and the extraction electrode 4, the conductivity of the oxide film of Al is affected. Therefore, the contact area between the extraction electrode 4 and the electrode land 9 should be increased (FIG. 5). In this case, CrA
Of course, the extraction electrode 4 may be superposed on the electrode land 9 formed as a mixed layer. In addition, since the excitation electrode is made of Al having a small mass in this electrode structure, it is suitable for a crystal oscillator in a high frequency band particularly in terms of frequency adjustment. In addition,
In addition to the above, various methods of increasing the conductivity to improve the CI are conceivable, and the purpose of the present invention is to maintain good temperature characteristics, not the purpose of improving CI.

From the above, by using the electrode structure of the present invention, first, the problem of electrical characteristics mainly in temperature characteristics in holding both ends can be solved. But,
Even if both ends are simply held, that is, even if the center or ends of both ends are held in points, the strength is insufficient in terms of impact resistance such as breakage. Therefore, it is desirable to hold four points in which both ends of each end are held point by point.
Hereinafter, this point will be described with reference to the second embodiment.

[0011]

[Second Embodiment] FIG. 6 is a view for explaining the reason why the second solution means of the present invention has been reached. To show that there is a difference in the amount of strain generated in the crystal blank 1 depending on the method of applying the adhesive. belongs to. Note that FIG. 6 (ab) is a diagram in the case where the adhesive 8 is directly applied to the surfaces of both ends of the crystal piece 1 and adhered thereto, FIG. 6 (a) is a plan view, and FIG. Is. Also,
FIG. 6 (cd) shows an electrode 10 in the width direction at one end of the crystal blank 1.
FIG. 6C is a plan view and FIG. 8D is a cross-sectional view in the case where the same is fixed. FIG. 7 (a) is an experimental result diagram in which the vertical axis represents the strain amount d (μm) according to these coating methods. The amount of strain here is measured by the measuring instrument ZYGO.
"(B)" in the figure, in which the vertical difference d on the surface of the crystal piece 1 after the adhesive 8 is cured is measured using the system. As is clear from this, the amount of strain generated in the crystal piece 1 is about 1.5 times larger when the adhesive 8 is directly applied to the crystal piece 1 and held than when the electrode 10 is interposed. That is, the bonding strength between the crystal piece 1 and the adhesive 8 is
Since it is larger than when the electrode 10 is interposed, the shrinkage force during curing directly affects. Also, the electrode 10
It is considered that when the intervening metal is used, since the bonding strength between the electrode 10 and the crystal piece 1 is small, a phenomenon such as slippage is caused between the two to relax the contracting force. Therefore,
When the crystal piece 1 is directly applied with an adhesive, the amount of strain is large and the crystal piece 1 is easily damaged, which deteriorates the impact resistance. On the other hand, when the adhesive 8 is applied on the electrode 10, the amount of strain is small and damage is prevented, so that impact resistance is improved. When the positions where the adhesive 8 is applied are close to each other, the strain at the time of contraction is concentrated between the two and is likely to be damaged. From this, basically,
In the case of holding at four points, for example, as shown in FIG. 8, if the adhesive 8 is applied to the surfaces on both sides of each electrode land 9, damage due to strain can be prevented. However, in this case, since the adhesion strength of the electrode land 9 to the surface of the crystal piece 1 is weak, the electrode land 9 is easily peeled off from the surface of the crystal piece 1, causing a problem of impairing electrical conduction. From this fact, as shown in FIG. 9, for example, the adhesive 8 is located inside the electrode land 9 on one side in the width direction of the electrode land 9 and straddles the electrode land 9 and the crystal blank 1 on the other side. Put it in the closed position and fix it. With such a fixing method, the electrode lands 9 intervene as described above, whereby the strain of the crystal blank 1 at the time of contraction is relaxed, and one side of each electrode land 9 does not contact the adhesive 8. It's a free end, so to speak. Further, on the other side, the adhesive 8 adheres to the surface of the crystal piece, which causes distortion, but since the one side is a free end, the distortion is liable to occur and damage is prevented. Then, on the other side, the adhesive 8 is applied directly over the electrode lands 9 and the crystal piece 1, so that the peel strength of the electrode lands 9 is increased and electrical continuity can be maintained. Therefore, in addition to the electrode structure of the previous embodiment, such four-point holding can achieve both-end holding with improved impact resistance without impairing the electrical characteristics.

[0012]

[Other Matters] In the above embodiment, the outer peripheral portions of both ends of the crystal piece 1 on which the electrode lands 9 are formed are fixed to the substrate.
For example, this electrode structure is useful even when it is fixed to a holder or the like provided on a substrate, or when it is held by a general flat plate-shaped supporter, and the present invention does not exclude this. Absent. Further, the electrode land 9 has a U-shape corresponding to the folded-back extraction electrode 4 which can be adhered from both sides, but the extraction electrode 4 is extended only to one main surface side, for example. In this case, the electrode lands may be formed only on the surface side, and these can be arbitrarily changed.
In short, the electrode lands 9 may be formed on the outer peripheral portions of the extending ends of the lead electrode 4 so as to overlap with them. Further, the outer dimensions and the direction of the crystal piece 1 are not limited to the embodiments, and the present invention can be basically applied even if the length direction is the x-axis direction or the dimensions are changed.

[0013]

According to the present invention, a separately formed connection electrode land is connected to an extraction electrode formed by extending from an input / output electrode of a crystal blank, and one of them is made of Al. Since the adhesive is applied to the outer peripheral portions of both ends where the electrode lands are formed and the outer peripheral portions are fixed, the temperature characteristics can be kept excellent. The adhesive is provided on both sides of each electrode land, and is located inside the electrode land on one side of each electrode land and fixed on the other side across the electrode land and the crystal piece, improving impact resistance. It is possible to provide a crystal unit that operates.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a first embodiment of the present invention, in which FIG. 1 (a) is a cross-sectional view of a crystal piece and FIG. 1 (b) is a plan view.

FIG. 2 is a view for explaining the first embodiment of the present invention, and is a plan view of a crystal piece showing an adhesive application position.

FIG. 3 is a temperature characteristic diagram for explaining the function and effect of the first embodiment of the present invention.

FIG. 4 is a view for explaining another example of the first embodiment of the present invention, in which FIG. 4 (a) is a plan view of a crystal piece and FIG. 4 (b) is a sectional view.

FIG. 5 is a plan view of a crystal piece for explaining another example of the first embodiment of the present invention.

FIG. 6 is a view for explaining the reason for reaching the second solution means of the present invention. FIG. 6 (a) is a plan view of a crystal piece in which an adhesive 8 is directly applied to the surfaces of both ends of the crystal piece 1. The figure, (b) is a sectional view when the crystal piece is fixed to a substrate, and (c) is the electrode 10 provided on one end of the crystal piece 1 and the conductive adhesive 8 is applied to both sides of the one end. FIG. 3D is a plan view of the crystal piece, and FIG. 6D is a cross-sectional view of the crystal piece fixed to a substrate.

FIG. 7 is a diagram for explaining the second embodiment of the present invention, in which FIG. 7 (a) shows the distortion amount d (μ of the quartz piece by the coating method of FIG.
m) is an experimental result diagram, and FIG. 6B is a sectional view defining the strain amount d of the crystal piece.

FIG. 8 is a view for explaining the second embodiment of the present invention, and is a plan view of a crystal piece showing a coating position of a conductive adhesive.

FIG. 9 is a view for explaining the second embodiment of the present invention, and is a plan view of a crystal piece showing a coating position of a conductive adhesive.

FIG. 10 is a cross-sectional view of a crystal element for explaining another embodiment of the present invention.

FIG. 11 is a cross-sectional view of a crystal resonator for explaining a conventional example.

FIG. 12 is a view for explaining a conventional example, and is a plan view of a crystal piece showing an electrode structure in the same figure (abc).

[Explanation of symbols]

1 crystal piece, 2 container, 3 excitation electrode, 4 extraction electrode,
5 container body, 6 lid, 7 metal ring, 8 adhesive, 9 electrode land, 10 electrode, 11 substrate.

Front Page Continuation (72) Inventor Takeo Seki 2 days at 1275 Kamihirose, Sayama City, Saitama Prefecture

Claims (2)

[Claims] 1. A pull-out electrode extends from an excitation electrode formed on both main surfaces of a crystal piece to outer peripheral portions of both ends of the crystal piece, and the outer peripheral portions of both ends are fixed and held on a substrate with a conductive adhesive. In the crystal resonator formed as described above, an electrode land having a width larger than that of the extraction electrode is superposed on the extraction electrode, the extraction electrode and the electrode land are formed of different metals, and one of the electrodes is made of Al. Characteristic crystal unit. 2. The conductive adhesive according to claim 1, wherein the conductive adhesive is provided on both sides of each electrode land, and is located inside the electrode land on one side of each electrode land and straddles the electrode land and the crystal piece on the other side. The crystal unit is characterized in that the crystal piece is fixed on a substrate in a state in which the crystal unit is positioned.