JP3974790B2 - Quartz device manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a quartz crystal device in which a quartz crystal resonator is bonded to a flat plate or casing-shaped substrate via a silicone conductive adhesive member obtained by curing a silicone-based conductive paste.
[0002]
[Prior art]
As shown in FIG. 7, a crystal device 51 that is a conventional crystal device has a crystal resonator 53 arranged in a ceramic package having electrode pads 525.
[0003]
The ceramic package 52 is formed by laminating a plate-shaped ceramic insulating layer such as alumina and a frame-shaped ceramic layer, and a cavity 520 for accommodating the crystal resonator 53 is formed therein.
[0004]
Further, external terminal electrodes 526 are formed on the lower surface of the ceramic package 52, and electrode pads 525 that are separated in the width direction at both ends in the longitudinal direction and are connected to terminal electrodes and the like outside are formed inside the ceramic package 52. In the upper part of the electrode pad 525, a strip-like bump 525a formed linearly in the width direction is formed.
[0005]
In addition, the quartz vibrator 53 includes excitation electrodes 531 and 533 and excitation electrodes 531 and 532 facing each other on both principal surfaces of a rectangular quartz substrate, and lead electrodes 532 extending from the excitation electrodes 531 and 532 to both principal surfaces on one short side of the quartz substrate. 534 is formed. Each electrode pattern (not shown) is formed using means such as vapor deposition or sputtering. Reference numerals 5321 and 5341 are electrode pads formed on one main surface of the quartz substrate after the extraction electrodes 532 and 534, and reference numerals 5322 and 5324 are electrode pads formed on the other main surface of the quartz substrate after the extraction electrodes 532 and 534. is there.
[0006]
A crystal device using such a crystal resonator is manufactured through the following manufacturing process.
[0007]
First, base metal layers 533a and 5322a such as Cr and Ni are formed in the first layer in a region where the excitation electrode 533 and the extraction electrode 5322 are formed on both main surfaces of the quartz substrate 530, for example, and the upper surface thereof. Then, second Au layers 533b and 5322b are formed, excitation electrodes 531 and 533 and lead electrodes 532 and 534 are formed to form a crystal resonator 53 (hereinafter described using Cr as a base metal layer). The same applies to the other extraction electrode 534, and the same applies to the upper surface side of the quartz crystal substrate 530.
[0008]
Thereafter, the crystal unit 53 is subjected to a heat treatment at 200 ° C. for 1 hour or more, for example, so that the first base metal layers 533a and 5332a are diffused into the second Au layers 533b and 5322b, and the Au layers 533b and 5322b Deposited on the surface, surface deposited layers 533c and 5322c are formed.
[0009]
Next, a ceramic package 52 is prepared.
[0010]
Next, a conductive resin paste to be a silicone-based conductive adhesive 57 is applied to the bumps 525a on the surface of the electrode pad 525, and the lead electrode of the crystal unit 53 is positioned on the applied conductive resin paste. To be installed.
[0011]
Thereafter, the conductive resin paste is cured, the ceramic package 52 and the piezoelectric vibrator 53 are fixed, and a lid 56 is attached on the ceramic package 52 so that the crystal vibrator 53 is hermetically sealed. (Japanese Patent Laid-Open No. 2000-151345).
[0012]
[Problems to be solved by the invention]
When a quartz crystal device is manufactured using the above-described manufacturing method and the entire crystal unit 53 is heated, the first Cr layer or Ni layer is deposited not only in the extraction electrode but also in the excitation electrode as shown in FIG. It was. That is, reference numeral 5322a is, for example, a Cr layer, 5322b is an Au layer, and 5322c is a surface deposition layer of Cr.
[0013]
In addition, as described above, the method of heating the entire crystal unit can be put into an annealing furnace or the like and batch-processed in order to increase production efficiency. However, in this method of heating a large number of crystal resonators at once, the step of mounting the electrode pads 525 and bumps 525a of the ceramic package 52 on the crystal resonators is sequentially performed after the heating. Depending on the crystal resonator, after 3 to 4 hours have elapsed, the quartz crystal resonator is placed on the conductive resin paste 54, and in particular, the surface deposited layer 5322c on the surface of the excitation electrode is oxidized, thereby the Au layer 5322b. Additional capacity is provided between the electrode pad 525 and the bump 525a, and the hardness and thickness of the excitation electrode and the extraction electrode are changed.
[0014]
As a result, the electrical capacity and the high temperature, for example, about 50 ° C., are affected by the change in additional capacitance and the hardness and thickness of the excitation electrode and the extraction electrode. There was a problem of coming.
[0015]
The present invention has been devised in view of the above problems, its object is also has good electrical properties at different temperatures, there is provided a method for manufacturing a quartz device that are stable .
[0016]
[Means for Solving the Problems]
This onset Ming, the underlying metal layer made of Cr layer or the Ni layer in a region to be a rectangular main surface excitation electrode and the extraction electrode of the quartz substrate, a step of sequentially depositing an Au layer, and the excitation electrode A mask having an opening that covers the region and exposes the region that becomes the extraction electrode is disposed on the quartz substrate, and the region exposed from the opening is irradiated with hot air, thereby forming the Au layer in this region. A step of forming a surface deposition layer formed by depositing the metal of the base metal layer on the surface, a step of preparing a substrate on which an electrode pad is formed, and applying a silicone-based conductive adhesive member on the electrode pad, And a step of mounting and fixing the quartz substrate by positioning an extraction electrode provided on the quartz substrate on an upper portion thereof.
[0017]
According to the present invention , a step of sequentially depositing a base metal layer made of a Cr layer or a Ni layer and an Au layer on a main surface of a rectangular crystal substrate and forming an extraction electrode and an extraction electrode; by abutting the heater formed in a block shape in the region, forming a surface deposition layer formed by depositing a metal of the underlying metal layer on the surface of the Au layer in this region, a substrate to form an electrode pad comprising the steps of preparing a silicone-based conductive adhesive member applied on the electrode pad, wherein by positioning an extraction electrode provided on the quartz substrate thereon, a step of mounting and fixing the quartz substrate, a It is a manufacturing method of a crystal device.
[0018]
In addition, since the surface of the excitation electrode can be substantially maintained by the Au layer, the formation of the surface precipitation layer can be effectively suppressed, and the state in which the surface is hardly oxidized can be maintained. For this reason, it is possible to effectively suppress the change in the CI value due to the change in the additional capacitance and the hardness and thickness of the excitation electrode and the extraction electrode at an electrical characteristic and high temperature, for example, about 50 ° C.
[0019]
Further, the lower surface side extraction electrode is placed so as to be positioned on the upper surface of an electrode pad or a bump coated with a conductive resin paste containing a silicone resin, and is cured by heating the conductive resin paste.
[0020]
As described above, by connecting and fixing the crystal resonator to the ceramic package, a good bonding state can be obtained in terms of the conductive resistance surface with the electrode pad or the bump in the extraction electrode.
[0021]
By performing the above-described method, it becomes possible to connect the conductive particles of the conductive adhesive member and the Au layer without forming a silicon film at the interface with the Au layer as in the prior art, and at the same time, the crystal vibration Since only the extraction electrode is heated by the child, the time required for heating can be shortened, and the above heating process and the crystal oscillator mounting process can be performed continuously. As a result, a crystal device with stable characteristics can be reliably and easily manufactured.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Will now be described in detail on the basis of a book onset Akira to the accompanying drawings.
[0023]
1 is a top view of the quartz device with the lid removed, FIG. 2 is a side sectional view of the quartz device, FIG. 3 is a top view of the quartz crystal resonator according to the present invention, and FIG. It is a principal part enlarged view of the holding | maintenance part of the base | substrate which accommodated and mounted the child.
[0024]
The crystal device 1 includes a ceramic package 2 as a base, a crystal resonator 3, a conductive adhesive 4, and a metal lid 6.
[0025]
The ceramic package 2 includes a rectangular flat plate-like substrate 21 made of ceramic, a frame-like substrate 22 made of ceramic laminated on the upper surface thereof, and a sealing periphery provided around the opening of the frame-like substrate 22. The conductive film 23 and a seal ring 24 joined to the sealing dynamic film 23 are included. As a whole, as shown in FIG. 2, a substantially rectangular cavity 20 having an opening on the surface side and accommodating the crystal resonator 3 is formed. Further, a pair of electrode pads 25 and 25 are formed on the bottom surface of the cavity 20, that is, on one short side (the left side in FIG. 1) of the top surface of the flat substrate 21. Yes. The electrode pads 25 and 25 are formed separately in the width direction of the short side (vertical direction in FIG. 1). The shape is substantially rectangular.
[0026]
The above-described seal ring 24 is made of a metal such as Fe—Ni and Fe—Ni—Co, and is formed on the sealing conductor film 23 formed around the opening of the frame-shaped ceramic substrate 22 by brazing or the like.
[0027]
Further, external terminal electrodes 26 are formed on the bottom surface of the ceramic package 2 so as to be electrically connected to the electrode pads 25 and 25 and bonded to the external printed wiring board. The electrode pads 25 and 25 and the external terminal electrode 26 are connected by a via-hole conductor that penetrates a part of the ceramic package 2. If the electrode pads 25 and 25 do not correspond to the positions where the external terminal electrodes 26 are formed, if a wiring conductor having a predetermined shape is formed on the bottom surface of the cavity 20, it can be easily connected by a via-hole conductor.
[0028]
Further, bumps 25a formed by baking of conductive metal paste, printing of conductive resin paste, insulating resin paste, and curing are formed on the surfaces of the electrode pads 25 and 25, particularly near the center of the cavity 20. May be.
[0029]
The electrode pads 25 and 25 and the sealing conductor film 23 are made of a metal such as molybdenum or tungsten, and are formed by plating Ni or Au on the surface thereof.
For example, when the bump 25a is formed by baking a conductive metal paste, a conductor to be a base conductor of the electrode pads 25 and 25 is printed and formed with the above metal paste, and after drying, the above metal paste is used on the surface thereof. The bumps 25a are formed by printing according to the shape of the bumps 25a, and then both are fired.
[0030]
The crystal unit 3 includes, for example, a rectangular crystal substrate 30 cut (AT cut) according to a predetermined crystal orientation angle, excitation electrodes 31 and 33 formed on both main surfaces of the crystal substrate 30, and a pair of A lead electrode 32 extending from the excitation electrodes 31 and 33 in the direction of the short side (left side in the figure) of the quartz substrate 30 (reference numeral 321 is an electrode on the upper surface side in the figure, and reference numeral 322 is a lower surface side in the figure). ), 34 (indicated by reference numeral 341 on the electrode on the upper surface side and indicated by reference numeral 342 on the lower surface side in the figure). For example, in the extraction electrode 321 extending from the upper surface side excitation electrode 31, it extends near the short side of the upper surface, and on the lower surface side through one long side end surface (lower end surface in the drawing) near the short side. The extended electrode 322 is formed. Conversely, the extraction electrode 342 extending from the excitation electrode 33 on the lower surface side extends near the short side of the lower surface, and the other long side end surface (upper end surface in the drawing) near the short side. The lead electrode 341 is extended to the upper surface side. The lead electrodes 32 and 34 are formed at positions facing both main surfaces of the quartz crystal substrate 30, respectively, and the shape thereof is a shape capable of conducting to the electrode pads 25 and 25 when arranged at predetermined positions. .
[0031]
The excitation electrodes 31 and 33 and the extraction electrodes 32 and 34 are formed of a mask of a predetermined shape on both main surfaces of the quartz substrate 30, and the first layer of Cr or Ni is used by means such as vapor deposition or sputtering. A base metal layer 35a is formed, and a second Au layer 35b is formed on the upper surface of the base metal layer 35a, whereby the crystal unit 3 is formed. (In the following description, description will be made using Cr as an example of the base metal layer.)
Electrical connection and mechanical connection between the ceramic package 2 and the crystal unit 3 described above are achieved by a silicone-based conductive adhesive 4 including a silicone resin 41 and conductive particles 42 as an adhesive.
[0032]
Specifically, only the extraction electrodes 32 and 34, in particular, at least the lower surface side extraction electrode (the portion on which the conductive adhesive 4 is attached) is heated by locally irradiating hot air, and each crystal resonator In contrast, heating is performed for a short time such as 250 ° C. and 5 to 10 minutes. Thereafter, the lead electrodes 32 and 34 of the crystal unit 3 are placed on the conductive resin paste applied on the electrode pads 25 and 25 on the lower surface of the cavity 20 and cured.
[0033]
In this manner, only the lead electrodes 32 and 34 are formed with a third Cr surface deposition layer on the second Au layer, and then the time is within 5 to 10 minutes within a short time. The crystal resonator 3 can be connected to the electrode pads 25 and the bumps 25a of the ceramic package 2 by using the conductive resin paste 4, and can be bonded to each crystal resonator 3 in a short time. Therefore, productivity is improved.
[0034]
Conventionally, in order to efficiently perform the heating of the crystal unit, a batch method is used to simultaneously heat a large amount of crystal units. Normally, after the crystal unit is heated, the ceramic unit is individually ceramicized. The lead electrode was placed so as to be positioned on the conductive resin paste applied to the electrode pad of the package. In this case, depending on the crystal resonator, it is placed after a long time of 3 to 4 hours, and Cr deposited on the surface of the excitation electrode during the time of being left in this way has been oxidized. End up. As a result, an abnormality that the CI value is remarkably deteriorated at a high temperature is generated. However, in the present invention, the thickness of the base metal layer 35a such as Cr may be about 40 to 80 mm. Even in a heated process such as a process, it is possible to effectively limit the amount of Cr deposited on the surfaces of the excitation electrodes 31 and 33, and to prevent a large change in oscillation frequency as a quartz crystal device. become.
[0035]
Here, the reason why the base metal layer 35a made of Cr may be 40 to 80 mm is that when the base metal layer is 40 mm or less, the Au layer 35b is required to be about 2000 mm or more. Since it is too thin for the layer 35b, even when only the extraction electrodes 32 and 34 are heated, almost no Cr can be deposited on the surface of the Au layer. For this reason, it becomes difficult to establish electrical connection between the conductive adhesive member 4 and the extraction electrodes 32 and 34 of the crystal unit 3.
[0036]
On the contrary, when the film thickness of the base metal layer 35a made of Cr becomes 80 mm or more, only the lead electrodes 32 and 34 of the crystal resonator 3 are locally heated, and the electrode pads 25 and 25 using the conductive adhesive member 4 are heated. When connected, an electrically stable connection can be obtained. However, in the heating process such as the reflow process in the subsequent process, diffusion of Cr into the Au layer and precipitation on the Au layer surface also proceed in the excitation electrodes 31 and 33. As a result, there is a risk that the oscillation frequency is lowered and eventually becomes a defective product.
[0037]
For the reasons described above, the film thickness of the base metal layer 35a made of Cr may be 40 to 80 mm. However, if the thickness is 50 to 60 mm, a more stable crystal resonator or crystal device can be obtained.
In addition, since the oscillation frequency does not change greatly even in a heating process such as a reflow process thereafter, there is a risk of causing abnormalities in electrical characteristics, for example, a CI value at a high temperature as a crystal device, that is, as an oscillation circuit. The risk of oscillation stop can be eliminated.
[0038]
The metal lid 6 is made of a substantially flat metal, for example, an Fe—Ni alloy (42 alloy), an Fe—Ni—Co alloy (Kovar), or the like. Such a metal lid 6 hermetically seals the accommodation region (cavity) 20 of the crystal resonator 3 with nitrogen gas or vacuum. Specifically, the metal lid 6 is placed on the seal ring 24 of the ceramic package 2 in a predetermined atmosphere, and the metal on the surface of the seal ring 24 and a part of the metal of the metal lid 6 are welded. As shown, seam welding is performed by applying a predetermined current. In order to perform this welding reliably, an Ag brazing layer or the like may be formed in advance on the joint surface side of the metal lid 6, and the brazing material melted by welding may be attached to the metal lid 6. An Ni plating layer may be formed on the surface side of the metal lid 6 so that the brazing material that goes around the surface side and contributes to the bonding does not decrease.
[0039]
As described above, by connecting the lead electrodes 32 and 34 of the crystal resonator 3 to the electrode pads 25 and the bumps 25a of the ceramic package 2, the conduction resistance at the joint portion with the silicone-based conductive adhesive 4 can be reduced. At the same time, the excitation electrode is oxidized and an oxide film is formed on the surface, so that an additional capacitance is generated between the Au layer and the electrode pad 25 and the bump 25a, and the hardness and thickness of the excitation electrode are changed. Although an abnormal change in the oscillation frequency may occur depending on the temperature, the occurrence of such an abnormality can be prevented.
[0040]
As a result, the quartz crystal device 1 that contains the quartz crystal resonator 3 and is hermetically sealed can provide the quartz crystal device 1 that has good conduction resistance and good electrical characteristics even when the temperature is changed. It became so.
[0041]
In practice, before the ceramic package 2 containing the crystal unit 3 is hermetically sealed using the metal lid 6, the oscillation frequency of the crystal unit 3 is adjusted using the external terminal electrode 26 or the like. Measure and adjust the frequency by evaporating Ag or the like on the surface of the upper surface side excitation electrode 31 of the crystal unit 3 or irradiating Ar gas and removing Au on the surface of the excitation electrode as necessary. The process to perform etc. is performed.
[0042]
The above-described crystal device 1 is manufactured as follows.
[0043]
First, a pair of electrode pads 25, 25 are formed on the bottom surface of the ceramic package 2, ie, the surface of the flat substrate 21, and the sealing conductor film 23 and the seal ring are formed on the surface around the opening of the cavity 20. The ceramic package 2, the crystal substrate 30 and the metal lid 6 on which 24 is formed are prepared.
[0044]
A base metal layer of Cr, which is the first layer by sputtering or vapor deposition, in the regions to be the excitation electrodes 31 and 33 on both main surfaces of the quartz substrate 30 and the lead electrodes 32 and 34 extended to both main surfaces on one short side. 35a is formed, and a second Au layer 35b is formed on the upper surface thereof to form the crystal unit 3.
[0045]
Thereafter, a process of locally heating only the extraction electrodes 32 and 34 of the crystal resonator 3 (at least the extraction electrode on the lower surface side) is performed.
[0046]
As a first heating method, as shown in FIG. 5A, hot air is irradiated to the extraction electrodes 32 and 34 exposed from the opening of the mask 36 of the crystal resonator fitted to the mask 36 or the like to perform heating. For example, it is performed with hot air at 250 ° C. for 5 to 10 minutes.
[0047]
As a second method, as shown in FIG. 5B, the heater 7 formed in a block shape is brought into contact with the extraction electrodes 32 and 34, for example, at 250 ° C. for 5 to 10 minutes.
[0048]
In this way, the extraction electrodes 32 and 34 on at least the lower surface side of the crystal unit 3 are heated by using the first method or the second method, and Cr in the base metal layer 35a is diffused into the Au layer 35b. It is deposited on the surface of the layer 35b. Here, a surface precipitation layer 35c is formed on the surface. Further, if necessary, the other main surface may be similarly subjected to local heat treatment.
[0049]
Next, a conductive resin paste that is silicone-based and hardened to become the conductive adhesive member 4 is supplied and applied to the electrode pads 25 and 25 with a dispenser or the like.
[0050]
Next, the crystal unit 3 is placed on the conductive resin paste supplied as described above. Specifically, the crystal unit 3 is placed so that the lower surface side extraction electrodes 32 and 34 are in contact with the portion supplied with the conductive resin paste.
[0051]
Next, the conductive resin paste is cured, and the ceramic package 2 and the crystal unit 3 are bonded and fixed. Specifically, it is cured by application of heat.
Thereafter, the metal lid 6 is placed on the seal ring 24, and seam welding is performed on both of them.
[0052]
In the above-described embodiment, Cr is used as the base metal layer 35a. However, Ni may be used instead of Cr. Further, in the above-described embodiment, the substrate has been described as a casing-shaped ceramic package, but a plate-shaped ceramic substrate may be used as the substrate. In this case, the shape of the lid 6 may be a casing that can cover the crystal unit 3.
[0053]
【The invention's effect】
As described above, in the present invention, the base metal layer made of Cr or Ni and the Au layer are deposited on the upper surface of the region to be the lead electrode and the excitation electrode on both main surfaces of the crystal resonator, and the lead electrode is locally formed. Since the lead electrode portion was diffused into the Au layer and deposited on the surface of the Au layer, the electrical conductivity was improved, and fluctuations in characteristics could be reduced.
[0054]
Furthermore, since only the extraction electrode is locally heated by hot air irradiation or heater heating, there is no need to heat the entire crystal unit by batch processing as in the past, and the extraction electrode heating process and the subsequent substrate It becomes easy to continuously perform the bonding process using the silicone-based conductive adhesive member for each crystal resonator.
[0055]
As described above, it is possible to provide a crystal device and a method for manufacturing the crystal device, in which production efficiency is dramatically improved.
[Brief description of the drawings]
FIG. 1 is a top view of a crystal device according to the present invention in a state where a lid is omitted.
FIG. 2 is a side sectional view of the quartz crystal device of the present invention.
FIG. 3 is a top view of a crystal resonator used in the crystal device of the present invention.
FIG. 4 is an enlarged cross-sectional view of a main part of a crystal resonator used in the crystal device of the present invention.
FIG. 5A is a cross-sectional view showing a state where the extraction electrode of the crystal resonator of the present invention is heated by hot air irradiation, and FIG. 5B is a cross-sectional view showing a state where the extraction electrode is heated by heater heating.
FIG. 6 is an enlarged cross-sectional view of a main part in a state in which a base metal layer is deposited on an extraction electrode and an excitation electrode of a crystal resonator used in a conventional crystal device.
FIG. 7 is a side sectional view of a conventional crystal device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Quartz device 2 ... Ceramic package 3 ... Crystal oscillator 31, 33 Excitation electrode 32, 34 Extraction electrode 35a Base metal layer 35b Au layer 35c Surface precipitation layer 4 ... Silicone system conductive adhesive member 41 ... Silicone resin 42 ... Conductive particles 6 ... Metal lid 7 ... Block heater

Claims (2)

A step of sequentially depositing a base metal layer made of a Cr layer or a Ni layer and an Au layer on a main surface of a rectangular crystal substrate in a region to be an excitation electrode and an extraction electrode ;
Placing a mask on the quartz substrate having an opening that covers the region to be the excitation electrode and exposes the region to be the extraction electrode;
Irradiating the region exposed from the opening with hot air to form a surface deposition layer by depositing the metal of the base metal layer on the surface of the Au layer in this region;
Preparing a substrate on which an electrode pad is formed;
A method of manufacturing a quartz crystal device, comprising: applying a silicone-based conductive adhesive member on the electrode pad; positioning a lead electrode provided on the quartz crystal substrate; and mounting and fixing the quartz crystal substrate. A step of sequentially depositing a base metal layer made of a Cr layer or a Ni layer and an Au layer on a main surface of a rectangular crystal substrate in a region to be an excitation electrode and an extraction electrode;
By abutting the heater formed in a block shape in a region to be the lead-out electrode, and forming a Au layer surface deposition layer formed by the metal of the underlying metal layer is deposited on the surface of this region,
Preparing a substrate on which an electrode pad is formed;
The silicone-based conductive adhesive member applied on the electrode pads, by positioning the lead electrodes provided on the quartz substrate thereon, a manufacturing method of the quartz crystal device including the steps of mounting and fixing the quartz substrate .

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