Patent Application
20110193643
This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2010-024655 filed on Feb. 5, 2010, the entire content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a manufacturing method of forming a plurality of through-electrodes adjacent to a substrate and a method of manufacturing a piezoelectric vibrator using the same.
2. Description of the Related Art
In recent years, piezoelectric vibrators using crystals or the like have been used as time sources or timing sources for portable phones or portable information terminal devices. Various types of piezoelectric vibrators are known, and as an example, a surface-mounted piezoelectric vibrator is known. As this type of piezoelectric vibrator, there is one known having a three-layer structure in which a piezoelectric substrate provided with a piezoelectric vibrating reed is interposed between a base substrate and a lid substrate in the vertical direction, followed by bonding. The piezoelectric vibrating reed is accommodated in a cavity provided between the base substrate and the lid substrate.
In addition, recently, a piezoelectric vibrator with a two-layer structure type has been developed. This type has a two-layer structure type package in which a base substrate and a lid substrate are directly bonded to each other, and a piezoelectric vibrating reed is accommodated in a cavity between the base substrate and the lid substrate. A piezoelectric element with the two-layer structure type is excellent because it can achieve a reduction in thickness compared to the three-layer structure type.
In JP-A-2002-124845 and JP-A-2002-121037, a crystal oscillator package in a two-layer structure type is disclosed. A glass material is used as a package material of a base substrate and a lid substrate. Since the glass material is used, molding is easily performed as compared with a case where a ceramic is used, and manufacturing costs can be reduced. In addition, the glass material has a low thermal conductivity and excellent thermal insulation, so that a piezoelectric vibrator therein can be protected from temperature changes.
The base substrate made of the glass material is provided with two through-electrodes and can supply drive power to the crystal oscillator from outside. A solidified silver paste or a metal member may be used for the through-electrode. The through-electrodes and a cavity are formed by performing die-molding on the glass material. Specifically, a glass substrate for the base substrate is interposed between a lower die which is a stationary die and an upper die which is a movable die. The upper die is provided with a pin for through-hole formation and a convex portion for cavity formation, and the lower die is provided with a concave portion for pin reception and a convex portion for the cavity formation. The glass plate for the base substrate is interposed between the upper and lower dies, and the glass plate is heated to its softening point or higher and is subjected to molding. Accordingly, the cavity for accommodating the crystal oscillator and the through-hole for electrode formation are simultaneously formed. Next, the though-hole is filled with the silver paste, and the silver paste is solidified to be used as the through-electrode. Otherwise, while the glass plate is heated and softened, the metal members as headed pins are individually inserted into the through-holes and cooled to be used as the through-electrodes. In addition, the crystal oscillator is fixed to a head portion of the headed pin with an adhesive.
In JP-A-2003-209198, a crystal oscillator package having the two-layer structure type as described above is disclosed. Even in this case, a method of using a glass material as a base substrate and forming through-electrodes using a metal material on the base substrate is disclosed. Specifically, through-holes are formed by performing die-molding on a base member made of the glass material. Next, a glass frit made of a low-melting-point glass is attached to the through-hole, and a headed metal pin is individually inserted into the through-hole. In addition, the base substrate is placed on a lower press die and is heated to a softening point or higher of the base substrate along with a upper press die to melt the glass frit, and a gap between the metal pin and the through-hole is sealed, thereby forming the through-electrode.
A reduction in size is required for the piezoelectric vibrators used in the portable phones or the portable information terminal devices. For example, as a size of the package of the piezoelectric vibrator, a size of several millimeters or less is required. In order to implement this, the shape of the piezoelectric vibrating reed has to be reduced, and the diameter of the through-electrode or the interval between the through-electrodes has to be reduced. For example, in the case where the through-electrodes are formed of the silver paste on the base substrate made of the glass material, two through-holes may be formed with high precision. However, with regard to the through-electrode formed of the silver paste, an organic material such as resin is removed from the silver paste during a baking process and thus the volume of the through-electrode is reduced, so that concave portions are generated on the surface of the through-electrode or a hole is generated on the through-electrode. Therefore, there are problems in that airtightness of the cavity is degraded, or conductivity between the piezoelectric vibrating reed and an outer electrode is degraded.
In addition, in the case where the metal pins are individually inserted into a plurality of the through-holes provided in the base substrate made of the glass material and the glass material is heated to a temperature equal to or higher than its softening point to weld the glass material and the metal pins to each other, the glass material is softened and made to flow, and thus although the through-holes are formed with high precision, position precision of the through-electrode is degraded. Particularly, when the glass material is interposed between the lower die and the upper die and then the metal pins and the glass material are heated to a temperature equal to or higher than the softening point of the glass material and pressed to be welded to each other, the two metal electrodes are moved, so that there is a problem in that desired position precision cannot be obtained.
In addition, even with regard to packages other than a crystal oscillator, if through-electrodes made of a metal material are formed on a base substrate made of a glass material for a package in which the diameters of the through-electrodes are small and high position precision and high airtightness are required, the same problem occurs.
In order to solve the above problems, an object of the invention is to provide a method of manufacturing a package capable of forming a through-electrode made of a metal material on a base substrate made of a glass material with high position precision.
A method of manufacturing a package according to the invention is a method of manufacturing a package for bonding a lid substrate onto a base substrate made of a glass material and accommodating an electronic component in a cavity configured therein, the method including: a through-hole forming step of providing a plurality of through-holes in a glass substrate; an electrode pin inserting step of preparing an electrode member having a plurality of pins erected on a base, and inserting the plurality of pins into the plurality of through-holes respectively; a welding step of heating the glass substrate to a temperature higher than the softening point of the glass substrate and welding the glass substrate and the electrode member to each other; and a grinding step of grinding both surfaces of the glass substrate along with the electrode member, exposing the plurality of pins from both surfaces of the glass substrate, and forming a base substrate having a plurality of through-electrodes in which through-electrodes are electrically separated from each other.
In addition, in the welding step, the glass substrate into which the plurality of pins is inserted is nipped between a receiving die and a pressurizing die and pressurized.
In addition, the through-hole forming step includes: a concave portion forming step of providing a plurality of convex portions in any one of the receiving die and the pressurizing die made of a carbon material, nipping the glass substrate between the receiving die and the pressurizing die and heating, and forming a plurality of concave portions on one surface of the glass substrate; and a penetrating step of grinding the other surface which is on the reverse side to the one surface of the glass substrate, and penetrating the plurality of concave portions from the one surface to the other surface.
In addition, a cooling step of cooling the glass substrate and the electrode member after the welding step is further included, and in the cooling step, compared to a cooling rate applied during cooling to a temperature 50° C. higher than the strain point of the glass substrate, a cooling rate applied during cooling from the temperature 50° C. higher than the strain point thereof to a temperature 50° C. lower than the strain point thereof is set to be smaller.
In addition, an axis-to-axis distance between center axes of the plurality of pins is in the range of 0.5 mm to 1.5 mm.
A method of manufacturing a piezoelectric vibrator according to the invention includes: a mounting step of mounting a piezoelectric vibrator on the base substrate manufactured as per any one of the package manufacturing methods described above; and a bonding step of bonding the lid substrate to the base substrate by anodic bonding.
In the method of manufacturing a package according to the invention, glass is used for the base substrate and thus the base substrate can be easily processed, and the glass substrate and the electrode member are welded to each other and thus airtightness of the package is further enhanced. Moreover, since the positions of the plurality of electrode pins are fixed in the welding step of welding the glass substrate to the electrode member, the plurality of electrode pins do not move relative to each other during welding. As a result, the plurality of through-electrodes can be positioned with high precision.
Before describing a method of manufacturing a package according to the invention, for easy understanding, an example of a package manufactured by the method of manufacturing a package according to the invention is described.
As illustrated in
As illustrated in
Here, a piezoelectric material made of crystal, lithium tantalate, lithium niobate, or the like may be used as the piezoelectric vibrating reed 5. Excitation electrodes (not shown) are formed on an upper surface of the piezoelectric vibrating reed 5 and a lower surface thereof on the reverse side. The one excitation electrode formed on the piezoelectric vibrating reed 5 is electrically connected to the outer electrode 7 via the conductive adhesive material 15, the lead-out electrode 14, and the through-electrode 9, and the other excitation electrode is electrically connected to the outer electrode 6 via the conductive adhesive material 15′, the lead-out electrode 14, and the through-electrode 8. Kovar is used for the through-electrodes 8 and 9.
First, in a through-hole forming step S1, a glass substrate 10 is prepared, and a plurality of through-holes 11 and 12 is provided in the glass substrate 10.
The through-holes 11 and 12 can be formed by grinding or etching. In addition, although described in detail according to a second embodiment, a convex portion is provided in at least one of a receiving die and a pressurizing die made of a carbon material, the glass substrate 10 is nipped between the receiving die and the pressurizing die and heated, a plurality of concave portions is provided on one surface of the glass substrate 10, and the other surface which is the reverse side to the one surface of the glass substrate 10 having the concave portions provided thereon is ground so as to penetrate a bottom surface of the concave portion.
Next, in an electrode pin inserting step S2, the pins 16 and 17 of the electrode member 18 are inserted into the through-holes 11 and 12 of the glass substrate 10.
Next, in a welding step S3, the glass substrate 10 is heated to a temperature higher than its softening point so that the pins 16 and 17 and the glass substrate 10 are welded to each other. During welding, the glass substrate 10 is interposed between the receiving die and the pressurizing die and pressed so as to accelerate fluidity of the glass material, thereby achieving welding for a short time. Since pins 16 and 17 are fixed to the base 19, although the glass substrate 10 is softened and flows, the pins 16 and 17 do not move or fall.
Next, in a cooling step S4, the glass substrate 10 is cooled.
Next, in a grinding step S5, both surfaces of the glass substrate 10 are ground, the base 19 is removed from the one surface 10a of the glass substrate 10, and protruding portions of the pins 16 and 17 are removed from the other surface 10b thereof, thereby flattening both surfaces.
As such, since the plurality of pins 16 and 17 is welded to the glass substrate 10 while being fixed to the base 19, although the diameters of the pins 16 and 17 are small within the range of 0.05 mm to 0.3 mm and the interval between the pins 16 and 17 is small within the range of 0.5 mm to 1.5 mm, welding can be performed with high position precision.
As illustrated in
In the subsequent penetrating step S1b, the other surface 10b which is on the reverse side to the one surface 10a of the glass substrate 10 is ground to penetrate the transferred concave portions 34a, 34b, 34c, and 34d through the other surface 10b.
Next, the receiving die 35, the pressurizing die 36, and the glass substrate 10 are cooled (cooling step S4), and the glass substrate 10 is taken out.
As such, the pins 16 and 17 fixed to the base 19 are inserted through the through-holes 11 and 12 and the pins 16 and 17 and the glass material are welded to each other, so that the through-electrodes 8 and 9 having high airtightness can be simply formed with high position precision. Accordingly, a number of packages of electronic components which have small electrode diameters and small intervals between the electrodes and require high reliability can be formed simultaneously.
First, in a polishing, washing, and etching step S0, a glass substrate is polished and washed, and then the glass substrate is subjected to etching to remove a work-affected layer on its outermost surface. Next, in a through-electrode forming step S9, as in the first or second embodiment, a glass wafer 21 having the through-electrodes 8 and 9 implanted in the glass substrate 10 is formed. The soda-lime glass may be used as the glass material.
Specifically, in the through-hole forming step S1, a plurality of the through-holes 11 and 12 is provided in the glass substrate 10. First, in the concave portion formation step, the glass substrate 10 is placed on the concave portion formation die 31, and is heated to the softening point of glass or higher to form a plurality of the transferred concave portions 34 on the one surface 10a of the glass substrate 10. A carbon material may be used as the concave portion formation die 31. The carbon material has an excellent release property from the glass material and absorbs gases discharged from the glass material, thereby reducing porosity of pores remaining in the glass material. Next, in the penetration step, the other surface 10b on the reverse side to the one surface 10a of the glass substrate 10 is ground, and the bottom surface of the transferred concave portion 34 is opened to form the through-holes 11 and 12.
Next, in the electrode pin inserting step S2, the electrode member 18 having the plurality of the pins 16 and 17 erected on the base 19 is prepared, and the plurality of the pins 16 and 17 of the electrode member 18 is inserted into the through-holes 11 and 12 of the glass substrate 10. Kovar is used for the electrode member 18. The glass substrate 10 in which the electrode member 18 is mounted is nipped between the receiving die 35 and the pressurizing die 36. The receiving die 35 is provided with the base receiving portion 38, and the base 19 of the electrode member 18 is mounted on the base receiving portion 38. The pressurizing die 36 may have a flat plate surface as an abutting surface abutting the glass substrate 10 or may be provided with protrusions for scribe lines for easily separating and cutting the glass substrate 10.
Next, in the welding step S3, the receiving die 35 and the pressurizing die 36 with the glass substrate 10 nipped therebetween are introduced into an electric furnace, and heated to the softening point of the glass material or higher, for example, to 900° C. and simultaneously the pressurizing die 36 is pressed. Accordingly, the glass material is made to flow and the side surfaces of the pins 16 and 17 and the side walls of the through-holes 11 and 12 are welded to each other. The glass material becomes a viscous flow and moves such that a stress is applied to the pins 16 and 17. However, since the pins 16 and 17 are fixed to the base 19 and mounted on the base receiving portion 38 of the receiving die 35, the pins 16 and 17 are not moved.
Next, in the cooling step S4, the receiving die 35, the glass substrate 10, and the pressurizing die 36 are cooled. During the cooling of the glass substrate 10, for example, compared to the cooling rate applied during cooling to the temperature 50° C. higher than the strain point of the glass substrate 10, the cooling rate applied during cooling from the temperature 50° C. higher than the strain point thereof to the temperature 50° C. lower than the strain point thereof is set to be smaller. Accordingly, strain remaining in the glass substrate 10 can be reduced. As a result, it is possible to prevent degradation in reliability of electronic components caused by degradation of airtightness between the through-electrodes and the base substrate due to gaps between pins and glass that are generated due to the thermal expansion difference between the pins 16 and 17 and the glass substrate 10, or cracks that are generated from the vicinity of the gaps.
Next, in the grinding step S5, both surfaces of the glass substrate 10 are ground along with the electrode member 18 and thus the base 19 of the electrode member 18 is removed, and the pins 16 and 17 are electrically separated from each other, thereby forming the through-electrodes 8 and 9. For example, both surfaces can be simultaneously ground using a double-sided polishing machine. Accordingly, the glass wafer 21 in which the exposed surfaces of the through-electrodes 8 and 9 and the surface of the base substrate 2 are flush with each other and thus have a high degree of planarity can be formed.
Next, in a bonding film forming step S6, a bonding film for anodic bonding is deposited on an area which becomes the vicinity of the base substrate 2. An aluminum film is deposited as the bonding film. Next, in a lead-out electrode forming step S7, the lead-out electrode 14 is formed from the upper surface of the one through-electrode 9 along an outer peripheral portion of the base substrate 2. The lead-out electrode 14 is formed by depositing an Au/Cr film using sputtering and performing patterning using photolithography or etching. In addition, the lead-out electrode 14 may also be formed using printing instead of the sputtering. The base substrate forming step S10 has been described above.
Next, the lid substrate forming step S20 will be described. In order to reduce the thermal expansion difference when the lid substrate 3 is bonded to the base substrate 2, the same material as that used for the base substrate 2 may be used for the lid substrate 3. When soda-lime glass is used for the base substrate 2, the same material is used for the lid substrate 3. First, in the polishing, washing, and etching step S21, the glass substrate is polished, and the glass substrate is subjected to etching to remove the work-affected layer on its outermost surface and is then washed.
Next, in the concave portion forming step S22, the concave portion 3a is formed by die-molding. The concave portion 3a is used for nipping the glass substrate between the receiving die having the convex portion and the pressurizing die having the concave portion, is heated to the softening point of the glass material or higher, and is pressed to be molded. It is preferable that the molding die be formed of the carbon material because the carbon material has an excellent release property from glass and an excellent property of absorbing bubbles. Next, in the polishing step S23, the bonding surface bonded to the base substrate 2 is polished to be a flat surface. Accordingly, sealing ability can be enhanced when the bonding surface is bonded to the base substrate 2.
Next, in the piezoelectric vibrating reed generating step S30, the piezoelectric vibrating reed 5 made of a crystal plate is prepared. The excitation electrodes which are electrically separated from each other are provided on both surfaces of the piezoelectric vibrating reed 5 and are electrically connected to a terminal electrode formed on a surface of one end of the piezoelectric vibrating reed 5. Next, in a mounting step S11, the conductive adhesive material 15, for example, the metal bump is formed on the end portions of the through-electrode 8 of the base substrate 2 and the lead-out electrode 14 or on the terminal electrode of the piezoelectric vibrating reed 5. The piezoelectric vibrating reed 5 is cantilevered by the conductive adhesive material 15. Accordingly, the excitation electrodes formed on both surfaces of the piezoelectric vibrating reed 5 are electrically separated from each other and conduct through the two through-electrodes 8 and 9.
Next, in a frequency adjustment step S12, a vibration frequency of the piezoelectric vibrating reed 5 is adjusted to a predetermined frequency. Next, in a superimposing step S13, the lid substrate 3 is installed and superimposed on the base substrate 2 with the bonding material 13 interposed therebetween. Next, in a bonding step S14, the base substrate 2 and the lid substrate 3 superimposed thereon are heated, and a high voltage is applied to the base substrate 2 and the lid substrate 3 for anodic bonding. Next, in an outer electrode forming step S15, the outer electrodes 6 and 7 which are electrically connected to the through-electrodes 8 and 9, respectively, are formed on the outer surface of the base substrate 2. Next, in a cutting step S16, the glass wafer 21 is separated and cut along the cutting lines, thereby obtaining individual piezoelectric vibrators 20.
As such, the pins 16 and 17 fixed to the base 19 are inserted through the through-holes 11 and 12 and the pins 16 and 17 and the glass material are welded to each other, so that position precision and airtightness of the through-electrodes 8 and 9 can be enhanced, thereby providing the piezoelectric vibrator 20 having small electrode diameters and small electrode intervals of the through-electrodes 8 and 9.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-024655 | Feb 2010 | JP | national |
