JP4543598B2 - Low temperature fired ceramic substrate manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a low-temperature fired ceramic substrate for producing a low-temperature fired ceramic substrate having convex portions or concave portions on a substrate surface.
[0002]
[Prior art]
For example, when a crystal resonator is mounted on the surface of a low-temperature fired ceramic substrate, the crystal resonator needs to be floated from the low-temperature fired ceramic substrate so as not to inhibit the vibration of the crystal resonator. Therefore, as shown in Japanese Patent No. 2913629 and Japanese Patent Laid-Open No. 2000-49562, a metal pedestal component that supports the crystal resonator is attached to the substrate surface, and the crystal resonator is mounted on the pedestal component. There is something like that.
[0003]
[Problems to be solved by the invention]
However, the above-described configuration has a drawback in that it takes time and labor to process a metal pedestal component on which a crystal resonator is mounted or to attach it to a substrate, resulting in high manufacturing costs.
[0004]
Therefore, recently, instead of a metal pedestal component, there is a type in which a conductive paste or glass paste is printed on a substrate surface to form a pedestal portion, and a crystal resonator is mounted on the pedestal portion. .
[0005]
However, in this printing method, the thickness of the pedestal portion obtained by one printing is at most about 15 to 20 μm, and a necessary thickness cannot be obtained. The degree is the limit. In addition, when overprinting is performed, printing bleeds, drooling may occur, or cracks may occur in the pedestal portion (conductor layer) during firing, and there is a drawback that the quality is not stable as a whole.
[0006]
The present invention has been made in consideration of such circumstances. Therefore, the object of the present invention is to easily form convex portions or concave portions of 30 μm or more on the substrate surface with high dimensional accuracy, and to reduce the manufacturing cost and quality. An object of the present invention is to provide a method for manufacturing a low-temperature fired ceramic substrate that can satisfy the demand for improvement.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a method for producing a low-temperature fired ceramic substrate according to claim 1 of the present invention is a constraining green sheet that does not sinter on both sides of a raw substrate of the low-temperature fired ceramic at the sintering temperature of the low-temperature fired ceramic. And then firing while pressing, using a pressure firing method (also referred to as restraint firing method) to remove the residual green sheet for restraint after firing and producing a low-temperature fired ceramic substrate, The convex green sheet is formed on the surface of the substrate by forming a convex or concave molded part on the surface to be crimped to the green substrate, and pressing the green sheet for constraining to the green substrate and firing it while applying pressure. The shape of the molding part is transferred. In this case, the pressure firing method is a firing method that reduces firing shrinkage in the surface direction of the substrate and improves the substrate dimensional accuracy. Therefore, using this pressure firing method, a green sheet for constraining green sheets is formed on the substrate surface. If the shape is transferred, it is possible to easily form convex portions or concave portions of 30 μm or more on the substrate surface with high dimensional accuracy.
[0008]
In this case, as in claim 2, the constraining green sheet having the forming portion may be formed by laminating a plurality of green sheets, or as in claim 3, the forming portion is The constraining green sheet may be formed by press molding. In any method, a constraining green sheet having a forming portion can be easily formed with high dimensional accuracy.
[0009]
By using the method for producing a low-temperature fired ceramic substrate of the present invention, convex portions or concave portions having various shapes can be formed on the substrate surface. For example, a crystal resonator or the like is formed on the substrate surface as in claim 4. The pedestal portion on which the vibration element is mounted is formed by a constraining green sheet molding portion, or a convex strip portion for preventing the sealing resin from flowing out is restrained on the substrate surface as in claim 5. You may make it form by the formation part of a green sheet. Thereby, it is possible to easily form a pedestal portion and a protruding strip portion having an appropriate height dimension on the substrate surface with high dimensional accuracy.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment (1)]
Hereinafter, an embodiment (1) in which the present invention is applied to a method of manufacturing a low-temperature fired ceramic substrate for mounting a crystal resonator will be described with reference to FIGS.
[0011]
First, the structure of the low-temperature fired ceramic substrate 10 will be described with reference to FIG. The low-temperature fired ceramic substrate 10 is obtained by stacking a plurality of low-temperature fired ceramic green sheets 11a, 11b, and 11c and pressurizing them at 800 to 1000 ° C. Examples of the low-temperature fired ceramic include CaO—SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ glass: 50 to 65 wt% (preferably 60 wt%) and alumina: 50 to 35 wt% (preferably 40 wt%). And a mixture thereof may be used. In addition, a mixture of MgO—SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ glass and alumina, or a mixture of SiO ₂ —B ₂ O ₃ glass and alumina, PbO—SiO ₂ —B ₂ A low-temperature fired ceramic material that can be fired at 800 to 1000 ° C., such as a mixture of O ₃ glass and alumina, or cordierite crystallized glass, may be used.
[0012]
In each ceramic layer (green sheets 11a, 11b, 11c), via holes 12 for interlayer connection are formed, and via conductors 13 are filled in the via holes 12 in each layer. The via conductor 13 of each layer is made of, for example, an Ag-based conductor paste mainly containing Ag, Ag / Pd, Ag / Pt, Ag / Au, or the like, or a paste of low melting point metal such as Au-based or Cu-based. Is formed.
[0013]
The second ceramic layer (green sheet 11b) has an inner layer conductor pattern 14 for connecting the first and second via conductors 13 with a low melting point metal such as Ag, Au, or Cu. It is formed by printing the paste. In addition, a back surface terminal 15 is formed on the lower surface of the lowermost ceramic layer (green sheet 11c) at a position where it is electrically connected to the via conductor 13 by printing a paste of a low melting point metal such as an Ag-based material, an Au-based material, or a Cu-based material. Yes.
[0014]
On the other hand, on the surface of the uppermost ceramic layer (green sheet 11a), a pedestal portion 17 on which the crystal resonator 16 is mounted is integrally formed by a method described later. The height of the pedestal portion 17 is, for example, 30 to 60 μm. A land 18 is formed on the upper surface of the pedestal 17 by printing a paste of a low melting point metal such as Ag, Au, or Cu, and the land 18 is connected to the via conductor 13 that penetrates the pedestal 17. . Thereby, the land 18 is connected to the back terminal 15 via the via conductor 13 and the inner layer conductor pattern 14. On the land 18, the crystal resonator 16 is bonded by a conductive adhesive 19.
[0015]
Next, a method for manufacturing the low-temperature fired ceramic substrate 10 having the above configuration will be described. The low-temperature fired ceramic green sheets 11a, 11b, and 11c are prepared by mixing a binder, a solvent, and a plasticizer with the above-mentioned low-temperature fired ceramic powder and sufficiently stirring and mixing the slurry, and using this slurry, a doctor blade Tape-formed by law.
[0016]
Before laminating the green sheets 11a, 11b, and 11c of each layer, a conductive paste of low melting point metal such as Ag, Au, or Cu is screen printed on the via hole 12 punched in the green sheets 11a and 11b of each layer. The via conductor 13 is formed by filling, and the inner layer conductor pattern 14 is screen-printed on the second green sheet 11b using the same kind of low melting point metal conductor paste.
[0017]
Further, on the lower surface of the lowermost green sheet 11c, the back terminal 15 is screen-printed using a paste of a low melting point metal such as Ag-based, Au-based, Cu-based, etc. The land 18 is screen-printed using a paste of low melting point metal such as Ag, Au, or Cu. Note that the back surface terminal 15 and the land 18 may be printed and fired after pressurization and firing.
After the printing process, the green sheets 11a, 11b, and 11c of the respective layers are laminated and thermocompression bonded and integrated to produce a low-temperature fired ceramic raw substrate 10 ′.
[0018]
On the other hand, the constraining green sheet 20 is formed using a high-temperature sinterable ceramic powder (for example, alumina powder) that is not sintered at the firing temperature (800 to 1000 ° C.) of the low-temperature fired ceramic raw substrate 10 ′.
[0019]
On the lower surface of the constraining green sheet 20 to be pressure-bonded to the upper surface of the low-temperature fired ceramic raw substrate 10 ', a recess 21 (molded portion) for forming the pedestal portion 17 is formed on the substrate surface by a press molding method or a green sheet lamination method. To do.
In the press molding method, the constraining green sheet 20 which has been tape-molded in advance by a doctor blade method or the like is press-molded to form the recess 21.
[0020]
On the other hand, in the green sheet laminating method, when the constraining green sheet 20 is produced by laminating a plurality of high-temperature sinterable ceramic green sheets, the recess 21 is formed in at least one green sheet previously laminated on the lower surface side. A constraining green sheet 20 is produced by forming a square hole for forming the film by punching or the like, and laminating the hole on another green sheet, followed by thermocompression bonding.
[0021]
In this case, the hardness of the constraining green sheet 20 is adjusted more appropriately than any of the binder, solvent, and plasticizer to be blended, so that the green sheet 11a, 11b, 11c (raw substrate 10 ′) of low-temperature fired ceramic is used. It is good to adjust it to be moderately hard.
[0022]
When the low-temperature fired ceramic raw substrate 10 ′ is pressure fired using the constraining green sheet 20, first, as shown in FIG. 1B, the restraining green is provided on both the front and back surfaces of the low-temperature fired ceramic raw substrate 10 ′. The sheet 20 is laminated, and this laminate is heat-pressed at 80 to 150 ° C., for example.
[0023]
Thereafter, the pressure-bonded body of the low-temperature fired ceramic raw substrate 10 'and the constraining green sheet 20 is sandwiched between porous setter plates (not shown) formed of alumina or the like, and at a pressure of 10 to 300 N / cm ² . It fires at 800-1000 degreeC which is the sintering temperature of the low-temperature baking ceramic raw substrate 10 ', pressurizing.
[0024]
During this firing, no pressure is applied to the portion of the surface portion of the low-temperature fired ceramic raw substrate 10 ′ corresponding to the concave portion 21 of the constraining green sheet 20, so that the ceramic in the portion rises into the concave portion 21, The recess 21 is filled with the ceramic on the substrate surface. Thereby, the pedestal portion 17 on which the crystal resonator 16 is mounted is formed on the substrate surface. Under the present circumstances, if the depth dimension of the recessed part 21 is 30-60 micrometers, for example, the height dimension of the base part 17 will be 30-60 micrometers.
[0025]
In this case, the constraining green sheet 20 (high temperature sinterable ceramic such as alumina) laminated on both surfaces of the low-temperature fired ceramic raw substrate 10 ′ does not sinter unless heated to 1300 ° C. or higher, and is fired at 800 to 1000 ° C. Then, the restraining green sheet 20 is left unsintered. However, in the firing process, organic substances such as a binder in the constraining green sheet 20 are thermally decomposed and scattered to remain as ceramic powder.
[0026]
After firing, the residue (ceramic powder) of the constraining green sheet 20 adhering to both surfaces of the fired substrate is removed by blasting, buffing or the like. Thereby, the manufacture of the low-temperature fired ceramic substrate 10 is completed.
[0027]
The embodiment (1) described above is characterized in that the pedestal portion 17 on which the crystal resonator 16 is mounted is formed on the surface of the substrate by using the pressure baking method. Therefore, if the shape of the concave portion 21 of the constraining green sheet 20 is transferred to the substrate surface using this pressure firing method, the firing shrinkage of the substrate is reduced to 30 on the substrate surface. The pedestal 17 having a thickness of ˜60 μm can be easily formed with high dimensional accuracy, and the demands for manufacturing cost reduction and quality improvement can be satisfied. According to the experiment results of the inventor, it has been confirmed that the height dimension of the pedestal portion 17 can be adjusted with an accuracy of ± 10% by adjusting the depth dimension of the recess 21 of the constraining green sheet 20.
[0028]
Needless to say, the element mounted on the pedestal portion 17 is not limited to the crystal resonator 16 and may be another oscillation element such as a ceramic resonator.
[0029]
[Embodiment (2)]
Next, Embodiment (2) of this invention is demonstrated based on FIG. In the present embodiment (2), the ridge portion 23 for preventing the sealing resin from flowing out is formed on the surface peripheral portion of the low-temperature fired ceramic substrate 22 as follows.
[0030]
First, a step 25 (molded portion) for forming the ridges 23 on the peripheral edge of the substrate surface is formed on the lower surface of the restraining green sheet 24 to be pressure-bonded to the upper surface of the low-temperature fired ceramic raw substrate by press molding or green sheet. It is formed by a lamination method.
[0031]
Then, the low-temperature fired ceramic green sheets 11a, 11b, and 11c of each layer are laminated and integrated by thermocompression bonding to produce a low-temperature fired ceramic raw substrate, and constraining green sheets 24 are laminated on both the front and back surfaces of the raw substrate. Then, this laminated body is heat-pressed at 80 to 150 ° C., for example.
[0032]
After that, the pressure-bonded body of the low-temperature fired ceramic raw substrate and the constraining green sheet 24 is sandwiched between porous setter plates (not shown) formed of alumina or the like, and pressed at a pressure of 10 to 300 N / cm ^2. While firing at 800 to 1000 ° C., which is the sintering temperature of the low-temperature fired ceramic raw substrate. Thereby, the ridge part 23 is formed in the peripheral part of the substrate surface by the step part 25 of the restraining green sheet 24.
[0033]
After firing, the residue (ceramic powder) of the constraining green sheet 20 adhering to both surfaces of the fired substrate is removed by blasting, buffing or the like. Thereby, the manufacture of the low-temperature fired ceramic substrate 22 is completed.
[0034]
According to the present embodiment (2) described above, the protruding ridge portion 23 that prevents the sealing resin from flowing out is formed on the substrate surface by the step portion 25 of the constraining green sheet 24 using the pressure firing method. Since it did in this way, the convex part 23 of moderate height dimension can be easily formed in a substrate surface with sufficient dimensional accuracy, and the request | requirement of manufacturing cost reduction and quality improvement can be satisfy | filled.
[0035]
Note that the present invention is not limited to the case where the crystal unit mounting base 17 or the sealing resin outflow prevention convex portion 23 is formed on the substrate surface, and various shapes of convex portions or concave portions are formed on the substrate surface. It can be applied when forming.
[0036]
The constraining green sheet is not limited to an alumina green sheet, and other high-temperature sinterable ceramic green sheets such as aluminum nitride (AlN) may be used.
[0037]
【The invention's effect】
As is apparent from the above description, according to the method for manufacturing a low-temperature fired ceramic substrate of claim 1 of the present invention, a pressure firing method is used, and the convex green surface of the restraining green sheet is pressed onto the raw substrate. Alternatively, the shape of the molding part of the constraining green sheet is transferred to the substrate surface by forming a concave molding part and firing the constraining green sheet against the green substrate and pressurizing it. Further, it is possible to easily form convex portions or concave portions of 30 μm or more on the substrate surface with high dimensional accuracy, and to satisfy the demands for manufacturing cost reduction and quality improvement.
[0038]
Further, in Claims 2 and 3, since the constraining green sheet having the forming part is formed by the green sheet laminating method or the press forming method, the constraining green sheet having the forming part can be easily and dimensionally accurate. It can be formed well.
[0039]
According to the fourth aspect of the present invention, since the pedestal portion on which the vibration element such as a crystal resonator is mounted is formed on the substrate surface by the forming portion of the restraining green sheet, the pedestal having an appropriate height dimension is formed on the substrate surface. The portion can be formed easily and with high dimensional accuracy.
[0040]
According to the fifth aspect of the present invention, since the protruding strip portion for preventing the sealing resin from flowing out is formed on the substrate surface by the forming portion of the restraining green sheet, the protruding strip portion having an appropriate height can be easily formed. In addition, it can be formed with high dimensional accuracy.
[Brief description of the drawings]
FIGS. 1A to 1C are views for explaining a manufacturing process of an embodiment (1) of the present invention. FIG. 2 is a longitudinal sectional view showing a structure of a low-temperature fired ceramic substrate on which a crystal resonator is mounted. 3 (a) and (b) are diagrams for explaining the manufacturing process of the embodiment (2) of the present invention.
DESCRIPTION OF SYMBOLS 10 ... Low temperature firing ceramic substrate, 10 '... Low temperature firing ceramic raw substrate, 11a, 11b, 11c ... Low temperature firing ceramic green sheet, 12 ... Via hole, 13 ... Via conductor, 14 ... Inner layer conductor pattern, 15 ... Back terminal, 16 DESCRIPTION OF SYMBOLS ... Crystal oscillator, 17 ... Base part, 18 ... Land, 19 ... Conductive adhesive, 20 ... Constraining green sheet, 21 ... Concave part (molding part), 22 ... Low-temperature-fired ceramic substrate, 23 ... Convex part, 24 ... green sheet for restraint, 25 ... step part (molding part).

Claims (5)

A constraining green sheet that does not sinter at the sintering temperature of the low-temperature fired ceramic is pressed onto both sides of the raw substrate of the low-temperature fired ceramic and fired while pressing, and after firing, the residual green sheet for restraint is removed. A method for producing a low-temperature fired ceramic substrate, comprising:
A convex or concave shaped part is formed on the surface of the restraining green sheet to be crimped to the raw substrate, and the restraint green sheet is fired while being pressed against the raw substrate and being pressed. A method for producing a low-temperature fired ceramic substrate, wherein the shape of the forming portion of the constraining green sheet is transferred to the substrate. The method for producing a low-temperature fired ceramic substrate according to claim 1, wherein the constraining green sheet having the forming portion is formed by laminating a plurality of green sheets. The method for producing a low-temperature fired ceramic substrate according to claim 1, wherein the constraining green sheet having the molded part is formed by press molding. 4. The manufacturing method of a low-temperature fired ceramic substrate according to claim 1, wherein a pedestal portion on which a vibration element such as a crystal resonator is mounted is formed on the substrate surface by a forming portion of the constraining green sheet. Method. The method for producing a low-temperature fired ceramic substrate according to any one of claims 1 to 4, wherein a protruding strip portion for preventing the sealing resin from flowing out is formed on the substrate surface by the forming portion of the constraining green sheet. .

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