JP3468373B2 - Crystal oscillator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field of use of a crystal unit, and more particularly to a frequency-temperature characteristic (temperature characteristic) and a shock resistance of a crystal unit used for surface mounting. The present invention relates to an electrode structure and a method for applying an adhesive, which improve the performance. BACKGROUND OF THE INVENTION Quartz resonators are often used as a frequency and time reference source in various electronic devices because of their excellent resonance characteristics. In recent years, there has been a great demand for products for surface mounting such as resistors and capacitors, especially those used in dynamic environments, so that they have good impact resistance and maintain temperature characteristics. Is required. FIG. 11 is a view for explaining a conventional example of a crystal unit for surface mounting. FIG. 11 (a) is a sectional view, and FIG. 11 (b) is a plan view of a crystal blank. It is. The crystal oscillator is formed by enclosing a crystal blank 1 in a closed container 2. The crystal blank 1 has, for example, a rectangular shape and an AT cut in a thickness shear vibration mode. Opposing excitation electrodes 3 are formed on both main surfaces, and the extraction 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 cover 6 on a concave container body 5 having a laminated structure. The container main body 5 is made of ceramic, a metal ring 7 is provided on the surface thereof, and joined by seam welding. The container body 5 has a stepped portion on the inner wall on both ends, and the outer peripheral portions on both ends of the crystal blank 1 are held by a conductive adhesive (not shown). However, in the crystal resonator having the above-described structure, the outer peripheral portions of both ends of the crystal blank 1 are fixed to each other, that is, the both ends are held. For this reason, strain (stress) is generated by the shrinkage force at the time of curing of the adhesive, particularly in the length direction of the crystal blank 1. As a result, the temperature characteristic is deteriorated particularly due to the stress sensitivity characteristic, and its practical use has been difficult. For this reason, generally, only one end of the crystal blank 1 is held and the other end is a free end (no conductive adhesive is applied) to prevent the occurrence of stress in the longitudinal direction. "FIG. 12 (abc)". Reference numeral 8 in the drawing is a conductive adhesive. However, when the entire area of one end is fixed as the area to which the adhesive 8 is applied even in the case of holding the one end, stress is generated in the width direction in FIG. I do. In the case where only a part of one end is fixed in a point manner (FIG. 9B), the connection strength is insufficient, the crystal blank 1 is detached at the time of impact, and breakage or the like occurs as described above. For this reason, the drawing electrode 4 is provided in the width direction of the end portion, and both sides of the one end portion are pointwise held as the adhesive 8 application region (FIG. 9C). However, even in this case (one end both sides holding),
Basically, since both ends in the width direction are fixed ends, the crystal blank 1 is particularly distorted in the width direction. In either case of holding one end, the other end, which is a free end, swings up and down, resulting in damage to the crystal blank 1 at that portion and weakening of the bonding strength at one end. Therefore, there is a problem that impact resistance is exhibited. The present invention basically focuses on the point that holding both ends ensures more stable holding of the crystal blank and improves the shock resistance such as breakage. , Was made focusing on the electrode structure and the bonding method to achieve this,
The first object of the present invention is to maintain good temperature characteristics and to improve impact resistance secondly after holding both ends. [0006] The present invention relates to a method of forming an Al film on both main surfaces of a crystal blank.
From the excitation electrode consisting of
And extend the extraction electrode formed by folding back to the opposite surface.
The outer peripheral portions of both ends of the extraction electrode are extended with a conductive adhesive.
In a quartz resonator fixedly held on a plate,
Ag having a larger width than the extraction electrode as a main component on the extraction electrode
Electrode lands are overlapped, and the conductive adhesive is applied to each electrode.
Provided on both sides of the pole land, one side of each electrode land
It is located inside the land, and on the other side it is between the electrode land and the crystal blank.
The quartz piece is fixed on the substrate in the
Wearing is the solution. First Embodiment FIG. 1 is a view for explaining an embodiment of the present invention, in particular, an electrode structure diagram of a crystal unit. The description of the same parts as in the prior art example is omitted. The quartz resonator is formed by enclosing an AT-cut rectangular quartz piece 1 in a closed container as in the prior art. The crystal blank 1 has excitation electrodes 3 on both main surfaces, extends the extraction electrodes 4 at both ends in opposite directions, and is folded back to the other main surface. As is apparent from the figure, 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 blank.
Is superimposed on the extraction electrode 4. However, electrode land 9
Are formed in a U-shape over both main surfaces at the outer peripheral portions at 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 quartz surface. The electrode land 9 has a single-layer structure of Al. In addition, all are formed by vapor deposition. The outer shape of the crystal blank 1 is 5 mm in length (z′-axis direction), 2.5 mm in width (x-axis direction), and thickness (y ′).
Axial direction) was about 80 μm (21 MHz). The crystal blank 1 having such an electrode structure was fixed on the substrate as holding both ends, and the temperature characteristics were measured. As a result, good results were obtained. However, the adhesive 8 was applied to the center of the electrode land (FIG. 2). That is, as shown in FIG. 3, in the conventional case (curve A), the characteristic is linearly shifted 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, a urethane conductive adhesive having a pencil hardness of 2B or less, for example, was used as the adhesive. According to the inventor's guess, in the related art, the shrinkage of the adhesive at the time of curing causes friction at the interface between the crystal blank 1 and the extraction electrode and the excitation electrode 3, and tension (stress) is applied to the surface of the crystal blank 1. ). This tension has a great effect on the thickness shear vibration, and impairs the original temperature characteristics due to the stress sensitivity characteristics. On the other hand, in the present invention, even if the adhesive shrinks, 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 blank 1 is reduced. 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 slip. Therefore, it is considered that the electrode structure having the above-described structure does not cause distortion due to tension at the exciting portion, and has little influence on the thickness-shear vibration, so that the original temperature characteristics can be obtained. However, in such a device, even if the temperature characteristics are improved, the crystal impedance (hereinafter referred to as CI) has not been sufficiently satisfied. That is, an oxide film is likely to be formed on the surface of the electrode land 9 made of Al, and thereafter is fixed by a conductive adhesive, so that the conductivity is deteriorated and sufficient CI cannot be obtained. Less than,
The solution to this point is described. FIG. 4 is a view for explaining a solution to this point. FIG. 4 (a) is a plan view of a crystal blank, and FIG.
Is a sectional view. That is, in this example, the electrode land 9
Is formed, and then the extraction electrode 4 is superposed thereon. Then, when the adhesive 8 was applied over the electrode lands around the extraction electrode 4 and fixed, the temperature characteristics and the CI were good. That is, as described above, a slip phenomenon occurs due to the action of the oxide film at the interface between the extraction electrode 4 and the electrode land 9, and no stress is generated in the excitation portion, so that the temperature characteristics can be favorably maintained. However, since the end of the extraction electrode 4 is fixed by the adhesive 8 as compared with the above-described case, it is considered that the slip phenomenon is more hindered than in the case described above. And the adhesive 8
Is in direct contact with the extraction electrode 4 formed as a CrAg mixed layer, so that the conductivity is not impaired, and therefore, a decrease in CI is prevented. Although Cr has a large specific resistance and easily forms an oxide film, it does not cause conduction failure since the Ag layer is mixed. In the above electrode structure, the excitation electrode 3 and the extraction electrode 4 are made of a mixed layer of CrAg 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 made of Al. May be a CrAg mixed layer. That is, even in this case, the temperature characteristics can be favorably maintained by the same slip phenomenon as described above. And in the case of fixing, Cr
Since the conductive adhesive is applied to the electrode lands 9 formed as the Ag mixed layers, CI is improved without causing poor conduction. 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 affects the conductivity. Therefore, it is preferable to increase the contact area between the extraction electrode 4 and the electrode land 9 (FIG. 5). In this case, CrA
Needless to say, the extraction electrode 4 may be overlapped on the electrode land 9 formed as the g mixed layer. Since this electrode structure is made of Al having a small mass as the excitation electrode, it is particularly suitable for a crystal resonator in a high frequency band from the viewpoint of frequency adjustment. In addition,
In addition to the above, there are various methods for improving the CI by increasing the conductivity, and the purpose of the present invention is to maintain good temperature characteristics, and not to improve the CI. [0010] From the above, by adopting the electrode structure of the present invention, first, the problem of the electrical characteristics mainly at the both ends holding, particularly the temperature characteristics can be solved. But,
Even if both ends are simply held, that is, even if the center or the ends of both ends are point-wise held, the strength is insufficient in terms of impact resistance such as breakage. Therefore, four-point holding for holding both sides of both ends pointwise is desirable.
Hereinafter, this point will be described with reference to a second embodiment. Second Embodiment FIG. 6 is a view for explaining the reason for the second solution of the present invention. There is a difference in the amount of distortion generated in the crystal blank 1 depending on the method of applying the adhesive. It is for showing. FIG. 6 (a) is a view in which the adhesive 8 is directly applied to and fixed to the surface on both sides of one end of the crystal blank 1. FIG. 6 (a) is a plan view, and FIG. 6 (b) is a cross-sectional view. It is. Also,
FIG. 6 (cd) shows the electrode 10 in the width direction of one end of the crystal blank 1.
(C) is a plan view, and (d) is a cross-sectional view. FIG. 7 (a) is an experimental result diagram in which the vertical axis is the amount of strain d (μm) by these coating methods. The amount of distortion here is measured by a measuring instrument ZYGO.
The vertical difference d on the surface of the crystal blank 1 after the curing of the adhesive 8 is measured using the system, as shown in FIG. As is clear from the above, the amount of distortion generated in the crystal blank 1 is approximately 1.5 times greater when the adhesive 8 is directly applied to the crystal blank 1 and held than when the electrode 10 is interposed therebetween. That is, the bonding strength between the crystal blank 1 and the adhesive 8 is
Since it is larger than the case where the electrode 10 is interposed, the contraction force at the time of curing has a direct effect. The electrode 10
It is considered that the presence of the intervening layer causes a phenomenon such as slippage between the electrodes 10 and the quartz piece 1 because the bonding strength between the electrode 10 and the crystal blank 1 is low, thereby reducing the contraction force. Therefore,
When an adhesive is directly applied to the crystal blank 1, the amount of distortion is large and the crystal blank 1 is easily broken, thereby deteriorating impact resistance. On the other hand, when the adhesive 8 is applied on the electrode 10, the amount of distortion is small, damage is prevented, and the impact resistance is improved. In addition, when the application position of the adhesive 8 is close, the strain at the time of shrinkage is concentrated between the two, and it is easy to be broken. So, basically,
In the case of holding at four points, for example, as shown in FIG. 8, if the adhesive 8 is applied to both surfaces of each electrode land 9, breakage due to distortion can be prevented. However, in this case, since the adhesion strength of the electrode lands 9 to the surface of the crystal blank 1 is weak, the electrode lands 9 are easily peeled off from the surface of the crystal blank 1, causing a problem that electrical conduction is impaired. For this reason, for example, as shown in FIG. 9, the adhesive 8 is located within 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. Position. According to such a fixing method, as described above, the interposition of the electrode lands 9 alleviates the distortion of the crystal blank 1 at the time of shrinkage. It is a free end. On the other side, the adhesive 8 adheres to the surface of the quartz piece, causing distortion. However, since one side is a free end, the distortion is liable to occur, thereby preventing breakage. Then, on the other side, the adhesive 8 is applied directly over the electrode lands 9 and the crystal blank 1, so that the peel strength of the electrode lands 9 is increased and the 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 deteriorating the electrical characteristics. In the above embodiment, the outer peripheral portions of both ends of the crystal blank 1 on which the electrode lands 9 are formed are fixed on the substrate.
For example, the 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 supporter, and the present invention does not exclude this structure. Absent. The electrode land 9 has a U-shape corresponding to the folded lead electrode 4 that enables bonding from both sides. For example, the lead electrode 4 extends only on one main surface side. 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 at both ends of the extension of the extraction electrode 4 so as to be superimposed thereon. The external dimensions and direction of the crystal blank 1 are not limited to those in the embodiment, and the present invention is basically applicable to a case where the length direction is the x-axis direction and the dimensions are changed. According to the present invention, an A-shaped crystal formed on both main surfaces of a crystal blank is provided.
from the excitation electrode consisting of
Extend the extraction electrode formed by folding back to the opposite surface,
The outer peripheral portions of both ends of the extraction electrode are extended with a conductive adhesive.
In the case of a crystal unit fixed and held on a substrate,
Ag which is wider than the extraction electrode is mainly formed on the extraction electrode.
And the conductive adhesive is applied to each
Provided on both sides of the electrode land, one side of each electrode land
It is located inside the pole land, and on the other side it is
Put the quartz piece on the substrate
Since it is fixed, it maintains the temperature characteristics and improves impact resistance.
The above-mentioned quartz oscillator can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining a first embodiment of the present invention, wherein FIG. 1 (a) is a sectional view of a crystal blank and FIG. 1 (b) is a plan view. FIG. 2 is a view for explaining a first embodiment of the present invention, and is a plan view of a crystal blank showing an application position of an adhesive. FIG. 3 is a temperature characteristic diagram for explaining the operation 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. FIG. 4 (a) is a plan view of a crystal blank, and FIG. 4 (b) is a sectional view. FIG. 5 is a plan view of a crystal blank for explaining another example of the first embodiment of the present invention. FIG. 6 is a view for explaining the reason for the second solution of the present invention. FIG. 6 (a) is a plan view of a crystal piece in which an adhesive 8 is directly applied to both surfaces of one end of the crystal piece 1. FIG. 2B is a cross-sectional view when the quartz piece is fixed to a substrate, and FIG. 1C is a diagram in which an electrode 10 is provided at one end of the quartz piece 1 and a conductive adhesive 8 is applied to both sides of the one end. FIG. 4D is a plan view of the crystal blank, and FIG. 4D is a cross-sectional view when the crystal blank is fixed to a substrate. FIG. 7 is a view for explaining a second embodiment of the present invention. FIG. 7 (a) shows a distortion amount d (μ) of a crystal blank by the coating method shown in FIG.
m) is an experimental result diagram, and FIG. 2B is a cross-sectional view defining the distortion amount d of the crystal blank. FIG. 8 is a view for explaining a second embodiment of the present invention, and is a plan view of a quartz piece showing a position where a conductive adhesive is applied. FIG. 9 is a view for explaining a second embodiment of the present invention, and is a plan view of a crystal piece showing a position where a conductive adhesive is applied. FIG. 10 is a cross-sectional view of a crystal blank for explaining another embodiment of the present invention. FIG. 11 is a cross-sectional view of a crystal unit illustrating a conventional example. FIG. 12 is a view for explaining a conventional example, and FIG. 12 (abc) is a plan view of a crystal blank showing an electrode structure. [Explanation of symbols] 1 crystal blank, 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.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Seki Takeo               Saitama Pref.               Nihon Denpa Kogyo Co., Ltd.                (56) References JP-A-63-109606 (JP, A)                 JP-A-63-193709 (JP, A)                 Showa 55-74126 (JP, U)                 Shokai Sho 61-33521 (JP, U)                 Actual opening Hei 1-143516 (JP, U)

Claims (1)

(57) Claims: 1. From the excitation electrodes made of Al formed on both main surfaces of the quartz piece, to the outer peripheral portions at both ends of the quartz piece on opposite sides.
Extending the extraction electrode formed by folding , the extraction electrode
In the quartz oscillator, the extended portions of both ends of which are fixed and held on a substrate with a conductive adhesive, an electrode land mainly composed of Ag having a width larger than that of the extraction electrode is formed on the extraction electrode. Superposed, the conductive adhesive is provided on both sides of each electrode land, and on one side of each electrode land,
On the other side, straddling the electrode land and crystal blank.
The quartz crystal device is characterized in that the quartz piece is fixed on a substrate in a placed state .