JP5159207B2 - Surface mount crystal filter and manufacturing method thereof - Google Patents

Description

  The present invention relates to a surface mount crystal filter (hereinafter referred to as a surface mount filter) in the technical field, and more particularly to the manufacture of a high frequency and broadband crystal filter.

(Background of the Invention)
Since surface mount filters are small and light, they are used, for example, in mobile phones and land mobile radio equipment. In recent years, in order to cope with an increase in data communication speed and an increase in capacity, a higher frequency and a wider band are required.

(Example of conventional technology)
FIG. 8A is a cross-sectional view of a surface mount filter for explaining one conventional example. The surface mount filter includes a crystal piece 1, a concave container body 2 made of a ceramic laminate, and a cover 3. The crystal piece 1 has an input / output electrode 4 (ab) on one main surface and a common electrode 5 on the other main surface by vapor-depositing chromium as a base electrode and silver or the like as a main electrode thereon. A lead electrode (not shown) extends from the input / output electrode 4 (ab) and the common electrode 5 to the outer periphery. These electrodes are formed by vapor deposition with the crystal piece 1 in close contact with an electrode forming mask.

  Then, after each electrode is formed, the outer peripheral portion of the crystal piece 1 from which the extraction electrode extends is fixed to the electrode pad 9 provided on the inner bottom surface of the container body 2 by the conductive adhesive 6, and the container body 2. It is electrically connected to the mounting terminal 10 formed on the outer bottom surface. A shield electrode 8 is formed on the inner bottom surface of the container body 2 and is connected to a grounding terminal 10 via a wiring (not shown) provided in the container body 2.

  The characteristics of the surface mount filter are designed so that the rough characteristics are suitable when the electrode is formed on the crystal piece 1, but a so-called frequency adjustment step is required in which the surface mount filter is individually fitted after being incorporated in the container body 2. . As shown in FIG. 8 (b), a frequency adjusting mask 11 is used for the crystal piece 1 in the container body 2 and a frequency adjusting film 15 is deposited at a desired position on the common electrode 5 to obtain electrical characteristics. Make fine adjustments. After adjustment, the cover 3 is welded to the container body 2 by seam welding or the like in an atmosphere filled with vacuum or nitrogen, and the surface mount filter is formed.

  The pass bandwidth in the surface mount filter is mainly determined by the film thickness of the input / output electrode 4 (ab) and the dimension between the input / output electrode 4 (ab). FIG. 9 (a) shows the relationship between the bandwidth and the gap between the input and output electrodes. In the so-called monolithic filter having the input / output electrode 4 (ab) and the common electrode 5, two vibration modes called the symmetric mode (Fs) and the oblique symmetric mode (Fa) shown in FIG.

  However, the resonance frequency of the oblique symmetry mode is higher than that of the symmetry mode. Further, the curve in FIG. 5A represents the magnitude of vibration displacement at each position of the electrode. The bandwidth of the surface mount filter is roughly proportional to the frequency difference between these two modes (usually written as dF), and when dF is large, it becomes a wideband filter. Although the bandwidth varies depending on the design, it is approximately twice the frequency difference dF between the two modes, for example.

  In the manufacture of the surface mount filter, the center frequency and the bandwidth are adjusted by depositing silver at a specific location on the common electrode 5. The frequency of each vibration mode decreases as the electrode thickness increases and the mass increases due to vapor deposition, but vapor deposition is performed at a location where the vibration displacement of one vibration mode is large and the vibration displacement of the other vibration mode is small. To selectively reduce the frequency of one vibration mode.

  For example, it is possible to lower the frequency of the symmetric mode by performing vapor deposition on the central portion of the common electrode 5 where the vibration displacement of the symmetric mode is large and the vibration displacement of the oblique symmetric mode is small. As a result, the bandwidth can be widened. Conversely, if the vapor deposition is performed on both ends of the common electrode 5, the frequency of the oblique symmetry mode is lowered, and the bandwidth is narrowed. In this way, the bandwidth is adjusted.

(Problems of conventional technology)
However, the surface mount filter having the above-described configuration has a problem that it cannot sufficiently cope with a wide band while high frequency and miniaturization progress. In other words, when the bandwidth is increased, it is necessary to reduce the electrode thickness of the input / output electrode 4 (ab) and to narrow the dimension between the input / output electrodes 4 (ab). For example, when the electrode thickness is reduced, the resonance frequency of both the symmetric mode and the oblique symmetric mode is lowered, so that the frequency difference between the two is reduced. Further, when the dimension between the input / output electrodes 4 (ab) is reduced, the resonance frequency of the symmetric mode is lower than that of the oblique symmetric mode, so that the bandwidth is widened.

  In these cases, the thickness of the electrode, regardless of the increase in the frequency, affects the aging characteristics and the like, and there is a limit to make it thin from the viewpoint of reliability, and the electrode thickness is maintained at a certain value or more, for example, 700 mm or more. . In general, although it varies depending on the frequency band, the upper limit is 3000 mm from the viewpoint of deterioration of vibration characteristics due to excessive mass. The dimension between the input / output electrodes 4 (ab) is formed by vapor deposition or sputtering using an electrode forming mask (not shown) according to the required bandwidth.

  The electrode forming mask has mask plates on both main surfaces having through holes (not shown) corresponding to the input / output electrodes 4 (ab) and the common electrode 5. Then, the crystal piece 1 is brought into close contact with the mask plates on both main surfaces, accommodated in the electrode forming mask, and deposited in a vacuum container. Thereby, the dimension between the input / output electrodes 4 (ab) is set to an approximate value corresponding to the required bandwidth. However, the dimension between the input / output electrodes 4 (ab) is limited to 0.05 mm due to the mechanical accuracy of the electrode forming mask and the spread of vapor deposition particles described later. Normally, the bandwidth at this point is set narrower than the standard value.

  Then, after fixing the crystal piece 1 to the inner bottom surface of the container body 2 (accommodating), as described above, the adjustment film 15 is provided at the central portion of the common electrode 5 facing the gap of the input / output electrode 4 (ab). Provide and adjust (fine tune) the bandwidth from narrower to wider. The adjustment film 15 is formed by vapor deposition using the frequency adjustment mask 11 that is disposed away from the main surface (common electrode side) of the crystal piece 1. The distance between the crystal piece 1 and the adjustment mask 11 is, for example, about 0.3 mm.

  In this case, the vapor deposition particles from the frequency adjusting device are vapor-deposited on the central portion of the common electrode 5 while spreading from the through hole of the adjustment mask 11 with a spread. Therefore, as the width between the input / output electrodes 4 (ab) becomes smaller as the bandwidth becomes wider, it becomes impossible to deposit on the central portion of the common electrode 5 accurately. If the bandwidth becomes wider than the standard value by adjustment, the adjustment film 15 by vapor deposition is provided at both ends of the common electrode 5 and readjustment is performed.

  Further, for example, as shown in FIG. 9 (a), in the frequency band and bandwidth where the conventional surface mount filter is required, the electrode dimensions (electrode area) that become the vibration displacement region between the symmetric mode and the oblique symmetric mode. On the other hand, since the adjustment film 15 in the central portion that lowers the resonance frequency is relatively sufficiently small, the influence on the other mode is small and adjustment can be performed without any problem.

  On the other hand, as shown in FIG. 9 (b), when the crystal piece 1 and the electrode area are reduced as the frequency is increased, the vibration displacement region between the symmetric mode and the oblique symmetric mode is also reduced. Therefore, the central adjustment film 15 is relatively large and affects the oblique symmetry mode, and the resonance frequency of the oblique symmetry mode is also lowered. From these points, there has been a problem that it is not possible to sufficiently cope with a wide band at the time of downsizing with an increase in frequency.

By the way, with a surface mount filter with a 3rd overtone in the 312 MHz band, the bandwidth with the electrode thickness and electrode spacing of the input / output electrodes 4 (ab) of the crystal piece being the aforementioned minimum values (700 mm and 0.05 mm) is: The maximum is approximately 38 kHz. Furthermore, even if the adjustment film 15 is provided between the input / output electrodes 4 (ab) with the adjustment mask after the crystal piece 1 is accommodated in the container body 2, the bandwidth is increased by several tens of percent to only about 45 to 50 kHz. Don't be.
JP-A-5-102787 JP-A-9-33228 JP 2001-7679 A JP 2004-228664 A

(Object of invention)
SUMMARY OF THE INVENTION An object of the present invention is to obtain a surface-mount filter that is suitable for a wide band while maintaining a high frequency and a small size, maintains reliability, and is highly productive.

The present invention has a crystal piece in which an input / output electrode is formed on one main surface and a common electrode is formed on the other main surface, and a concave portion for accommodating the crystal piece, as shown in the claims (Claim 1 ). For surface mounting, comprising a container main body and a cover for sealing the container main body, and having a frequency adjustment body having a height higher than that of the peripheral portion at the central portion of the common electrode facing the gap portion of the input / output electrode In the quartz filter, the frequency adjusting body is a load electrode formed at the time of forming the input / output electrode and the common electrode before at least the quartz piece is accommodated in the container body, and the quartz piece and the common electrode A load electrode formed by vapor deposition or sputtering using an electrode forming mask within the width of the gap between the input and output electrodes, and an adjustment film formed to finely adjust the bandwidth, Crystal piece is the container body And an adjustment film formed on the common electrode stacked on the load electrode by vapor deposition or sputtering using a frequency adjustment mask after the common electrode is fixedly accommodated on the upper side.

According to a third aspect of the present invention , an input / output electrode is provided on one main surface and a common electrode is provided on the other main surface, and a load electrode as a frequency adjusting body is provided at the center of the common electrode facing the gap between the input / output electrodes. Before the crystal piece is accommodated in the container body, the input / output electrode, the common electrode, and the load electrode are all formed by vapor deposition or sputtering from both main surfaces using an electrode forming mask. In the method of manufacturing a filter, the crystal piece is accommodated in a first electrode forming mask having a through hole corresponding to the input / output electrode and the load electrode, and the first electrode forming mask is used. a first plating step for forming said applied electrode and the output electrode by vapor deposition or sputtering, after retrieving the crystal blank from the first electrode forming mask, corresponding to the crystal piece to the common electrode And a second plating step of forming the common electrode by vapor deposition or sputtering using the second electrode forming mask, which is accommodated in a second electrode forming mask having holes, and further After fixing the common electrode on the container body with the common electrode as the upper side, an adjustment film for finely adjusting the bandwidth is formed on the common electrode laminated on the load electrode by vapor deposition using a frequency adjustment mask or sputtering. Let it be a manufacturing method.

(Effect of Claim 1)
With such a configuration of the first aspect, the load electrode is formed in advance on the central portion of the common electrode before the frequency adjustment using the adjustment mask after the crystal piece is accommodated in the container body. In this case, similarly to the common electrode, the load electrode can be formed by vapor deposition or sputtering using an electrode forming mask in a state close to or close to 0.02 mm or less on both main surfaces of the crystal piece. In the case of etching, the electrode forming mask can be formed in close contact with the crystal piece.

  Therefore, the load electrode is placed closer to or closer to the crystal piece than the adjustment film using the adjustment mask separated from the crystal piece after being accommodated in the container body, and the deposited particles do not spread. It can be formed with high accuracy on the central portion of the common electrode between the output electrodes, that is, the maximum displacement portion of the symmetric mode and the minimum displacement portion of the oblique symmetric mode. As a result, the load electrode can reduce the influence on the oblique symmetry mode, and can independently lower only the resonance frequency of the symmetry mode.

  Therefore, the bandwidth (for example, about 2 dF) approximately proportional to the difference (dF) in the resonance frequency between the symmetric mode and the oblique symmetric mode can be greatly increased. Incidentally, as shown in the embodiment, the bandwidth of 38 kHz in the conventional example described above can be increased to 80 kHz or more, which is twice as much. Therefore, in the present invention (Claim 1), since the bandwidth can be increased even if the electrode film thickness of the input / output electrodes and the common electrode and the dimension between the input / output electrodes are equal to or larger than the specified values, the reliability is maintained high. And even if the miniaturization of the crystal piece at the time of high frequency progresses, the bandwidth can be increased.

  Furthermore, the load electrode is provided with high accuracy in the center of the common electrode in advance before the bandwidth adjustment with the quartz crystal housed in the container body. Accordingly, the adjustment amount (adjustment film) at the time of vapor deposition using the adjustment mask for adjusting the band mass after the quartz piece is accommodated in the container body, for example, using the adjustment mask for band adjustment can be reduced. In this case, the adjustment film affects not only the bandwidth but also other filter characteristics such as the center frequency. However, since the change of the center frequency is small, the readjustment is facilitated. Therefore, productivity can be increased.

  In the case of the conventional example, since the amount of adjustment at the time of band adjustment after the crystal piece is accommodated in the container body is increased, the influence on other filter characteristics is also increased, and for example, the center frequency is readjusted. Become. Since these band adjustments and other adjustments influence each other, for example, when the center frequency is readjusted, the bandwidth changes and becomes out of specification when the bandwidth is out of the standard. Therefore, these adjustment operations are complicated and productivity is deteriorated.

  In addition, since the load electrode is formed on the central portion of the common electrode that becomes the gap portion of the input / output electrode here, even if the gap portion of the input / output electrode becomes narrow and the load electrode is shifted, an extreme problem occurs. There is no. On the other hand, when a load electrode is formed directly in the gap between the input / output electrodes and there is a positional shift, an electrical short circuit occurs with any of the input / output electrodes, resulting in a defective product.

In the present invention, the load electrode is formed between the crystal piece and the common electrode. Thereby, when the input / output electrode and the common electrode are formed, the thickness of the central portion of the common electrode is increased, so that the bandwidth can be efficiently widened.

Furthermore, by the load electrode is formed by vapor deposition or sputtering or etching using a mask for forming an electrode, the electrode forming mask is formed in proximity to or in close contact with the crystal blank, bandwidth spread efficiently It becomes clearer.

Furthermore, the width of the load electrode by was the gap width of the input and output electrodes, and remain spread the bandwidth by narrowing the electrode spacing of the input and output electrodes, with lots of further bandwidth by the load electrode. In addition, the case where the width of the load electrode is the same as the gap width of the input / output electrodes is included.

In the second aspect , the total thickness of the common electrode and the load electrode is set to 800 to 3000 mm, and the electrode thickness of the common electrode is set to 700 mm or more. Thereby, since the total thickness of the electrode thickness of a common electrode and a load electrode shall be 3000 mm or less, a vibration characteristic is maintained favorable. Since the common electrode has a minimum thickness of 700 mm or more, the aging characteristics and the like resulting from the electrode thickness are maintained well. Therefore, reliability can be ensured as in the prior art, and the bandwidth can be expanded by the load electrode.

Furthermore, in the present invention, the frequency adjustment body includes the load electrode and an adjustment film provided on a central portion of the common electrode where the load electrode is located after the crystal piece is accommodated in the container body. Become. Accordingly, the bandwidth can be finely adjusted by the adjustment film as the load mass after the crystal piece is accommodated in the container body after the bandwidth is widened by the load electrode.

Thus, by vapor deposition or the first and second electrode forming mask for sputtering, so close to the main surface of the quartz piece as already mentioned can form the load electrode on the common electrode, a load electrode electrode formed It can be formed with high accuracy along the inner periphery of the mask.

Further, the input / output electrode, the common electrode, and the load electrode are formed by vapor deposition or sputtering from both main surface sides of the crystal piece, and the crystal piece has a through hole corresponding to at least the load electrode. A first plating step of forming the load electrode with the second electrode forming mask, and taking out the crystal piece from the second electrode forming mask; The quartz crystal piece is accommodated in a first electrode forming mask having at least a through hole corresponding to the common electrode, and includes a second plating step for forming the common electrode with the first electrode forming mask. .

Thereby, a common electrode can be formed on a load electrode with the 1st and 2nd electrode formation mask for vapor deposition or sputtering. Even in this case, each electrode forming mask is close to the main surface of the crystal piece as described above, and the load electrode can be formed with high accuracy along the inner periphery of the electrode forming mask.

Further, after the crystal piece is accommodated in the container main body, an adjustment film is provided at the central portion of the common electrode where the load electrode is located. Thereby, the bandwidth can be finely adjusted by the mass load effect by adding the mass as described in the first aspect .

  FIGS. 1 (a) and 1 (b) are diagrams for explaining an embodiment of the present invention. FIG. 1 (a) is a sectional view showing a surface mount filter of the present invention, and FIG. 1 (b) is a surface mount without a cover. It is a top view of a filter. In addition, the same number is attached | subjected to the same part as a prior art example, and the description is simplified or abbreviate | omitted.

As described above, the surface mount filter is configured by accommodating the crystal piece 1 inside the container body 2. The crystal piece 1 is obtained by processing an AT-cut crystal plate into a rectangular shape, and has dimensions of 1.9 mm in length and 1.0 mm in width. The container body 2 is a three-layered laminate made of ceramic, and has dimensions of 2.5 mm in length and 2.0 mm in width. The cover 3 is made of Kovar or phosphor bronze having a thickness of about 0.2 mm, and is hermetically sealed by seam welding or the like through a seal ring (not shown).

  In this embodiment, the input / output electrode 4 (ab) is formed on one main surface of the crystal piece 1, the common electrode 5 is formed on the other main surface, and the load electrode 7 is formed on the common electrode 5. The The output electrode 4 (ab) and the common electrode are made uniform in thickness, and the thickness of these electrodes and the gap between the input / output electrodes 4 (ab) are set to the minimum values for widening the bandwidth. That is, as described above, the thickness of the input / output 4 (ab) and the common electrode 5 is set to 700 mm, and the gap between the input / output electrode 4 (ab) is set to 0.05 mm.

  The load electrode 7 is formed on the central portion of the common electrode 5 facing the gap portion of the input / output electrode 4 (ab), and is formed within the gap width. Here, the width of the load electrode 7 is set to 0.05 mm, which is the same as the gap width. The thickness of the load electrode 7 is set to 2300 mm or less, and the total thickness with the common electrode 5 is set to, for example, 3000 mm or less, which does not adversely affect the vibration characteristics.

  The input / output electrode 4 (ab) is made of Al (aluminum), the common electrode 5 is made of Ag (silver) with a base of Cr (chrome), and the load electrode 7 is made of Ag. These input / output electrodes 4 (ab), common electrode 5 and load electrode 7 are formed by vapor deposition using an electrode forming mask. In this case, the gap between the electrode forming mask and both main surfaces of the crystal piece is, for example, 0.02 mm or less, and vapor deposition is performed in a close proximity.

  As described above, after the formation of the input / output electrode 4 (ab) common electrode 5 and the load electrode 7 by vapor deposition, the outer peripheral portion of the crystal piece 1 to which an unillustrated extraction electrode extends is the electrode pad 9 in the container body 2. Are fixed by a conductive adhesive 6 and are electrically and mechanically connected. At this time, the crystal piece 1 is held by the electrode pad 9 with the other main surface having the output electrode 4 (ab) facing the shield electrode 8 and the other main surface having the load electrode 7 and the common electrode 5 facing up. ing.

(First specific example of manufacturing method)
Next, a first specific example of a manufacturing method using the surface mount filter of the present invention will be described. In these cases, a rectangular crystal piece 1 is cut out from a crystal wafer (not shown) in advance, and a large number of crystal pieces 1 are placed in an etching tank filled with hydrofluoric acid and the like, and etching is performed until a predetermined thickness is obtained. After the etching is completed and dried, first, the input / output electrode 4 (ab), the common electrode 5 and the load electrode 7 are formed on both main surfaces of the crystal piece 1 by, for example, vapor deposition using an electrode forming mask. To do.

  The electrode formation here requires two vapor deposition steps, unlike a single vapor deposition step in a conventional surface mount filter. As shown in FIG. 2 (ab), the first electrode forming mask 12 used in the first vapor deposition step is composed of two masks 12 (the input / output electrodes 4 (ab) and the common electrode form 5). ab). This is the same as a conventional electrode forming mask, with one mask 12a serving as an input / output electrode 4 (ab) and the other mask 12b serving as a pattern corresponding to the common electrode 5 through holes 14 ( xy).

  As shown in FIG. 2 (cd), the second electrode forming mask 13 used in the second vapor deposition step shields one main surface side of the crystal piece 1 on which the input / output electrodes 4 (ab) are formed. And a mask 13b on the other main surface side having a through hole 14z corresponding to the load electrode 7 formed at the center of the common electrode 5.

  The first and second electrode forming masks 12 and 13 each have a holding frame 16 that forms a space between the two masks 12 (ab) and 13 (ab). . And after accommodating the crystal piece 1 in a space part, it fixes with the screw etc. which were provided in the square part which is not shown in figure. Each of these two masks 12 (ab) and 13 (ab) is made of, for example, a stainless steel plate having a thickness of about 0.05 mm, and each through hole 14 (xyz) is formed by etching. In addition, although the example of the mask with respect to one crystal piece 1 was shown in the figure, it is set as the sheet form in which many crystal pieces 1 are accommodated actually.

  Next, the crystal piece 1 is sandwiched and accommodated in the first electrode forming mask 12, and then the first electrode forming mask 12 is fixed to a mask holder installed in the vapor deposition apparatus and vapor deposited. Thus, the input / output electrode 4 (ab) is formed on one main surface of the crystal piece 1 and the common electrode 5 is formed on the other main surface (FIG. 3A). Next, the crystal piece 1 is taken out from the first electrode forming mask 12, and the crystal piece 1 is accommodated in the second electrode forming mask 13. And it vapor-deposits similarly and forms the load electrode 7 on the center part of the common electrode 5 (FIG. 3 (b)). Here, the load electrode 7 is set to a thickness narrower than the bandwidth of the specification (standard).

  Next, the outer peripheral portion of the crystal piece 1 from which the extraction electrode extends from the input / output electrode 4 (ab), the common electrode 5 and the load electrode 7 is fixedly accommodated on the inner bottom surface of the container body 2. In this case, as described above, the other main surface on which the input / output electrode 4 is formed faces the shield electrode 8 of the container body 2 and is on the lower side, and the one main surface on which the common electrode 5 and the load electrode 7 are formed is on the upper side. As fixed.

  And the adjustment film | membrane 15 is formed on the load electrode 7 by vapor deposition by metals, such as silver, using the frequency adjustment mask 11, and a bandwidth is finely adjusted. That is, the adjustment film 15 lowers the resonance frequency of the symmetric mode to widen the frequency difference from the oblique symmetric mode, and finely adjusts the bandwidth from a narrower side to a wider direction. Other characteristics including, for example, the center frequency are adjusted by the same vapor deposition while maintaining the bandwidth within the standard value. Thus, various final frequency adjustments including the bandwidth are performed. Finally, a cover is joined to the open end face of the container body 2 and the crystal piece 1 is hermetically sealed.

(Second specific example of manufacturing method)
In the first specific example, after the input / output electrode 4 (ab) is formed by the first electrode forming mask 12, the load electrode 7 is provided on the central portion of the common electrode 5 by the second electrode forming mask 13. However, these orders are reversed in the second specific example.

  That is, in the second specific example, first, the load electrode 7 is provided on the central portion of the other main surface of the crystal piece 1 by the second electrode forming mask 13. Next, the common electrode 5 is formed on the load electrode 7 by the first electrode forming mask 12 and the input / output electrode 4 (ab) is formed on the other main surface side.

(Other specific examples)
In these cases, for example, after the input / output electrode 4 (ab) and the load electrode 7 are formed first, the common electrode 5 can be formed on the load electrode 7 (FIG. 4 (a)). In addition, after the load electrode 7 is formed first, the input / output electrode 4 (ab) and the common electrode 5 can be formed (FIG. 4B).

(Effect of embodiment)
FIGS. 5A to 5F are diagrams for explaining the action of the load electrode compared to the conventional example. FIG. 5A is a basic example of a filter, FIG. 5C is a conventional example, and FIG. It is a specific example of the present invention. 5 (a), (c), and (e) are cross-sectional views of the crystal piece, and FIGS. 5 (b), (d), and (f) are reactance characteristics with respect to frequency.

  In the basic example of the filter, when the input / output electrode 4 (ab) and the common electrode 5 are provided, “FIG. 5 (a)” causes vibrations in the symmetric mode (Fs) and the oblique symmetric mode (Fa). “(A)” having a resonance characteristic represented by a reactance characteristic. Then, for example, the anti-resonance point (parallel resonance point) fa in the symmetric mode and the series resonance point fs ′ in the oblique symmetric mode are matched.

  As a result, the inductive region is formed between the series resonance point fs in the symmetric mode and the antiresonance point fa ′ in the oblique symmetric mode. For example, the bandwidth in the 3 dB attenuation region from the center frequency is proportional to the inductive region, and as described above, the frequency difference (fs′−fs) between the series resonance frequency of the symmetric mode and the oblique symmetric mode. Is proportional to

  Conventionally, as described above, after accommodating the crystal piece 1 in the container body 2, the adjustment film 15 is formed by vapor deposition on the central portion of the common electrode 5 using the adjustment mask 11 separated from the crystal piece 1. FIG. 5 (d) ". Therefore, since the adjustment film 11 is formed with a gentle slope, it affects not only the maximum displacement portion in the symmetric mode but also the vibration displacement portion in the oblique symmetric mode. Accordingly, not only the series resonance frequency fs of the symmetric mode but also the series resonance frequency fs ′ of the oblique symmetric mode is lowered, so that the frequency difference dF (= fs′−fs) between them is not so wide as “FIG. 5 (d)”. .

  On the other hand, in the present embodiment, the load electrode 7 is previously formed on the central portion of the common electrode 5 by using the second electrode forming mask 13 at the time of electrode formation before being accommodated in the container body 2, for example. FIG. 5 (e) ". Therefore, the load electrode 7 can be accurately formed in the maximum displacement portion of the symmetric mode and the minimum displacement portion of the oblique symmetric mode with the outer peripheral end face being steep.

  Accordingly, the amount of decrease in the resonance frequency fs ′ in the oblique symmetry mode relative to the amount of decrease in the resonance frequency fs in the symmetric mode can be reduced, and the frequency difference dF between both can be increased (FIG. 5 (f)). Therefore, it is easy to increase the bandwidth. Even when the common electrode 5 is formed on the load electrode 7 using the second electrode forming mask 13, the load electrode 7 can be formed with high accuracy in the central portion, and the same effect is produced.

  By providing the load electrode 7, the parallel resonance frequency fa is lowered by lowering the series resonance frequency fs in the symmetric mode, and the reactance characteristic is entirely lowered. Therefore, the parallel resonance frequency fa of the symmetric mode and the resonance frequency fs ′ of the oblique symmetric mode do not coincide with each other, and the vicinity of the center frequency becomes a capacitive region and a ripple is generated. However, this ripple can be flattened by, for example, an external inductor.

(Effects of the embodiment)
FIG. 6 is a graph for explaining the effect of the load electrode, particularly a graph showing the frequency difference dF (= fs′−fs) between the symmetric mode and the oblique symmetric mode when the thickness of the load electrode is changed. However, as described above, the center frequency is 312 MHz, the gap between the input / output electrodes 4 (ab) is 0.05 mm, and the width of the load electrode 7 is 0.05 mm, which is the same width as the gap. The load electrode is provided on the center of the common electrode, and the electrode thickness of the input / output electrode and the common electrode is 700 mm.

  As is apparent from this figure, the frequency difference dF in the conventional case where the load electrode 7 is not formed is 38 kHz, whereas in the present embodiment, the thickness of the load electrode 7 is increased. The frequency difference dF also increases. The load electrode 7 is a curve obtained by actually measuring the thickness of the load electrode 7 as 50, 100, 200, 300, 500, 600 mm and connecting these points.

  Specifically, the dF increases slightly when the thickness of the load electrode 7 is 50 mm, and becomes 42 kHz at 100 mm, 55 kHz at 200 mm, 60 kHz at 300 mm, 80 kHz at 500 mm, and 100 kHz at 600 mm. Therefore, for example, when the thickness of the load electrode 7 is 200 mm, the bandwidth becomes 42 kHz with respect to the conventional 38 kHz, and the bandwidth becomes 30% or more. In addition, when the frequency is 500 mm, the frequency becomes 80 kHz or more than the conventional value, and when the adjustment film of the conventional example is provided to increase the bandwidth, for example, 30 kHz or more, the bandwidth can be significantly increased.

  The other effects are the same as those described in the “Effects of the Invention” section (paragraphs 0021 to 0040), and are therefore omitted here.

(Other matters)
In the above embodiment, the input / output electrode 4 (ab), the common electrode 5 and the load electrode 7 are formed by vapor deposition, but may be formed by sputtering. Even in this case, the above-described first and second electrode forming masks 12 and 13 are applied. Furthermore, the present invention is not limited to vapor deposition or sputtering, and can be applied even when formed by etching.

  In this case, the electrode forming mask is, for example, a crystal piece (quartz wafer), and the first and second electrode forming masks are formed by a resist film using a photolithographic technique (photo printing technique). Then, unnecessary metal on the quartz wafer is removed by wet etching, for example, and the input / output electrode 4 (ab), the common electrode 5 and the load electrode 7 are formed. For example, only the input / output electrode 4 (ab) and the common electrode 5 may be etched, and the load electrode 7 may be vapor deposited or sputtered.

  In addition, the surface mounting filter having a two-pole type composed of a pair of input / output electrodes 4 (ab) has been described. For example, as shown in FIG. A so-called three-pole type using three vibration modes (F1, F2, and F3), or a four-pole type or more (not shown) provided with more divided electrodes can be applied. FIG. 7 (b) is a diagram showing the application of the present invention to, for example, a three-pole filter. In this case as well, a load electrode may be provided on a common electrode between three divided electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining one Embodiment of this invention, The figure (a) is sectional drawing of the surface mount filter which formed the load electrode in the common electrode, The figure (b) is a top view of the surface mount crystal filter except the cover It is. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining an electrode forming mask according to the present invention. FIGS. 1A and 1B are a common electrode side pattern and an input / output electrode side pattern of a conventional electrode forming mask, and FIGS. These are the common electrode side pattern and the input / output electrode side pattern of the load electrode forming mask provided on the common electrode in the present invention. FIG. 4E is a side view showing the electrode forming mask and the crystal piece accommodated in the electrode forming mask. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining an example of the electrode formation process of this invention, The figure (a) is sectional drawing of the crystal piece before load electrode formation, The figure (b) is a figure explaining a mode that a load electrode is formed. The figure explaining the other example in the electrode formation process of this invention, The figure (a) is sectional drawing of the crystal piece which formed the common electrode on the load electrode after forming an input-output electrode and a load electrode previously, FIG. 4B is a diagram for explaining how the input / output electrodes and the common electrode are formed on the load electrode after the load electrode is formed. The figure explaining the effect of the load electrode in a surface mount crystal filter, The figure (a) is a sectional view of the crystal piece before the frequency adjustment in the conventional surface mount filter, The figure (b) is the frequency characteristic of the vibration mode. FIG. FIG. 4C is a cross-sectional view of a crystal piece when the bandwidth is adjusted to a conventional surface mount crystal filter, and FIG. 4D is a frequency characteristic diagram of the vibration mode. FIG. 4E is a cross-sectional view of a crystal piece of a surface mount filter in which a load electrode is formed on the common electrode of the present invention, and FIG. 4F is a frequency characteristic diagram of the vibration mode. It is a graph which shows the relationship between the film thickness of a load electrode, and dF. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining the application example to 3 poles of this invention, The figure (a) is sectional drawing of the crystal piece used for the 3 pole type filter before load electrode formation, The figure (b) is three division electrodes. It is sectional drawing of the crystal piece explaining a mode that two load electrodes are formed on the common electrode in between. The figure explaining the conventional surface mount crystal filter, The figure (a) is a side view of the surface mount crystal filter explaining a prior art example, The figure (b) is a figure explaining the mode of the frequency adjustment of a surface mount crystal filter It is. FIG. 6A is a diagram for explaining the relationship between the vibration mode of the surface-mount crystal filter and the electrode. FIG. 5A shows the relationship between the vibration mode in the low-frequency surface mount filter, the electrode, and the frequency adjustment location, and FIG. It is a figure which shows the relationship between the vibration mode in a broadband surface mount crystal filter, an electrode, and a frequency adjustment location.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Crystal piece, 2 Container body, 3 Cover, 4 Input / output electrode, 5 Common electrode, 6 Conductive adhesive, 7 Load electrode, 8 Shield electrode, 9 Electrode pad, 10 Mounting terminal, 11 Frequency adjustment mask, 12 Output electrode forming mask, 13 Common electrode forming mask, 14 Load electrode forming mask, 15 Frequency adjustment film, 16 Crystal holding frame.

Claims (3)

A crystal piece having an input / output electrode on one main surface and a common electrode on the other main surface; a container body having a recess for accommodating the crystal piece; and a cover for sealing the container body; In the surface mount crystal filter having a frequency adjusting body having a height higher than that of the peripheral portion in the central portion of the common electrode facing the gap portion of the electrode,
The frequency adjuster is
A load electrode formed at the time of forming the input / output electrode and the common electrode before at least the crystal piece is accommodated in the container body, and a gap between the input / output electrodes between the crystal piece and the common electrode A load electrode formed by vapor deposition or sputtering using an electrode forming mask within the width of
An adjustment film formed to finely adjust a bandwidth, wherein the crystal piece is fixedly accommodated in the container body with the common electrode as an upper side, and then deposited on the load electrode by vapor deposition or sputtering using a frequency adjustment mask. An adjustment film formed on the common electrode laminated on the substrate;
A surface-mount crystal filter characterized by comprising:   The surface mount crystal filter according to claim 1, wherein the total electrode thickness of the common electrode and the load electrode is 800 to 3000 mm, and the electrode thickness of the common electrode is 700 mm or more. An input / output electrode is provided on one main surface, a common electrode is provided on the other main surface, and a load electrode as a frequency adjusting body is provided at the center of the common electrode facing the gap between the input / output electrodes. A method of manufacturing a quartz filter in which the input / output electrode, the common electrode, and the load electrode are all formed by vapor deposition or sputtering from both main surfaces using an electrode forming mask before being housed in a main body. ,
The crystal piece is accommodated in a first electrode forming mask having a through hole corresponding to the input / output electrode and the load electrode, and the input / output electrode is formed by vapor deposition or sputtering using the first electrode forming mask. And a first plating step for forming the load electrode ;
After the crystal piece is taken out from the first electrode forming mask, the crystal piece is accommodated in a second electrode forming mask having a through hole corresponding to the common electrode, and the second electrode forming mask. Performing a second plating step of forming the common electrode by vapor deposition or sputtering using
After the crystal piece is fixedly accommodated in the container body with the common electrode as the upper side, an adjustment film for finely adjusting the bandwidth is deposited or sputtered using a frequency adjustment mask on the common electrode laminated on the load electrode. A method for producing a surface-mounted crystal filter, characterized by comprising:

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