JP3896792B2 - Electronic device and piezoelectric device package - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a package structure of an electronic device in which an IC element such as an IC (semiconductor integrated circuit) chip is mounted on a base and hermetically sealed, and in particular, a piezoelectric device in which an IC element and a piezoelectric vibrating piece are mounted in the same package. Related to the package.
[0002]
[Prior art]
Conventionally, various electronic devices and piezoelectric devices such as piezoelectric vibrators have been used in various information / communication equipment, OA equipment, consumer equipment, and other electronic equipment. Particularly recently, in the field of small information devices such as mobile computers and IC cards, and communication devices such as mobile phones, the size and performance of devices have been remarkably reduced. In response, piezoelectric devices have become smaller and thinner. There is a demand, and piezoelectric devices such as an oscillator and a real-time clock module in which a piezoelectric vibrating piece and an IC chip are sealed in the same package have been developed. Furthermore, a surface-mount type device suitable for mounting the apparatus on a circuit board is required.
[0003]
As such a surface mount type piezoelectric device, for example, in Japanese Patent Application Laid-Open No. 11-163670 by the present applicant, an IC chip and a piezoelectric vibrating piece are mounted on a base made of a ceramic insulating substrate having a laminated structure, A package structure in which a metal lid is joined and hermetically sealed is described. In this piezoelectric device, metal bumps formed on the electrode pads of the IC chip are connected to the electrode pattern formed on the mounting surface of the base by flip chip bonding, and the IC chip is more securely fixed and electrically connected. For this purpose, an underfill material is filled and cured in the gap between the base mounting surface and the IC chip lower surface.
[0004]
[Problems to be solved by the invention]
However, the flip chip bonding method using an underfill material after connecting the bumps of the IC chip and the substrate is, for example, a paper by Yoshinobu Honma "Underfill material for flip chip" (Electronic Materials, September 2000, pp. 36-40) And underfill material in the gap between the IC chip and the substrate, as described in the paper by Allen, “Underfill Sealant for Mounting Area Array Devices” (Electronic Materials, September 2000, pp. 42-48) There is a possibility that voids are generated by entraining air when the air is poured. Furthermore, with the miniaturization and thinning of piezoelectric devices and other electronic devices, the gaps are narrowed and the pitch of bumps is remarkably reduced, and voids are more likely to occur when using an underfill material. When the package is heated and expanded when the device is mounted on the substrate, the void may cause peeling or cracking in the underfill material, resulting in a problem that reliability and durability are impaired.
[0005]
In particular, a piezoelectric device having a package structure in which an IC chip and a piezoelectric vibrating piece are sealed as described in Japanese Patent Laid-Open No. 11-163670 described above is usually joined to a base by a seam welding or glass sealing. The package of the piezoelectric device is preferably vacuum-sealed to prevent corrosion of the piezoelectric vibrating piece and ensure its operational reliability. However, it is not possible to perform seam welding or glass sealing of the lid in a vacuum atmosphere. It is technically difficult in practice.
[0006]
Accordingly, the present invention has been made in view of the above-described conventional problems, and an object of the present invention is to mount an IC element on a base by flip chip bonding using an underfill material, and bond a lid to the base. An object of the present invention is to provide a highly reliable package that can effectively prevent the generation of voids in an underfill material while reducing the size and thickness of an electronic device hermetically sealed.
[0007]
Furthermore, an object of the present invention is to mount an IC element and a piezoelectric vibrating piece in the same package and hermetically seal, and in a piezoelectric device mounted based on the IC element by flip chip bonding using an underfill material, Similarly, it is an object of the present invention to provide a highly reliable package capable of effectively preventing generation of voids in an underfill material while reducing the size and thickness.
[0008]
[Means for Solving the Problems]
According to the present invention, in order to achieve the above object, in a package of an electronic device that has a base and a lid bonded to the base and hermetically seals an IC element therein, the base includes: An IC element is mounted on the mounting surface by flip-chip bonding and fixed with an underfill material, and a gas vent hole that opens to the outside of the package is formed on the mounting surface on the lower side of the IC element. An electronic device package is provided in which the holes are hermetically closed at the outer surface of the package.
[0009]
By providing a vent hole on the mounting surface of the base in this way, when filling the gap between the lower surface of the IC element and the base mounting surface with an underfill material, air or other gas in the gap Since the gas is exhausted not only from the gas vent holes, it is possible to effectively prevent the occurrence of voids in the underfill material regardless of the narrowing of the gap and the narrowing of the pitch of the bumps.
[0010]
According to another aspect of the present invention, in a package of a piezoelectric device having a base and a lid joined to the base and hermetically sealing an IC element and a piezoelectric vibrating piece therein, the base includes: An IC element is mounted on the mounting surface by flip-chip bonding and fixed with an underfill material, and a gas vent hole that opens to the outside of the package is formed on the mounting surface on the lower side of the IC element. A package of a piezoelectric device is provided in which the hole is hermetically closed from the outer surface side of the package.
[0011]
As a result, it is possible to effectively prevent the occurrence of voids in the underfill material even in a piezoelectric device package in which the IC element is mounted on the base by flip chip bonding and fixed with the underfill material. it can.
[0012]
In one embodiment, the base is further provided with a sealing hole communicating with the outside of the package in a region other than the IC element mounting region, and the sealing hole is airtightly closed from the outer surface side of the package. Has been. For example, as known in the art, the sealing hole is formed by attaching a metal ball such as Au-Sn in a dry air atmosphere, an inert gas atmosphere or a vacuum atmosphere after the lid is airtightly joined to the base. It can be sealed airtight by inserting from the outside of the package and heating and welding.
[0013]
Further, in one embodiment, the vent hole and the sealing hole communicate with a common opening provided on the outer surface of the package. In this case, by closing the common opening from the outside of the package by, for example, a technique of welding the metal balls, it is possible to simultaneously close both holes in the same process as before.
[0014]
Further, when the base has a laminated structure of thin plates made of an insulating material such as a ceramic material, the box-shaped package having a recess for accommodating the piezoelectric vibrating piece and the IC element is assembled, and both the base plate and the base are assembled. Since formation of a hole can be performed easily, it is preferable.
[0015]
In one embodiment, the piezoelectric vibrating piece is disposed above the IC element in the package, which is particularly advantageous for downsizing the piezoelectric device.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
1A to 1C show a first embodiment of a piezoelectric device to which the present invention is applied. This piezoelectric device is a piezoelectric oscillator, and includes a package 4 including a base 1 made of an insulating material and a metal lid 3 joined to the upper end of the base 1 via a seal ring 2. In the package 4, an AT-cut quartz crystal vibrating piece 5 mounted on the base 1 and an IC chip 6 for driving the AT-cut crystal vibrating piece 5 are sealed in a vacuum. The lid 3 is joined by, for example, seam welding, which is preferable because high heat does not act on the IC chip 6 and the crystal vibrating piece 5. When the lid 3 is made of glass, it can be joined directly to the upper end of the base with low melting point glass without using a seal ring.
[0017]
The base 1 has a substantially rectangular box-like structure composed of first to seventh layers 11 to 11 in which insulating thin plates made of a ceramic material are laminated. Crystals are formed by openings formed in the third to ninth layers 11. A space 12 for accommodating the resonator element 5 and the IC chip 6 is defined. The bottom of the void 12, that is, the surface of the second layer 8 exposed by the opening of the third layer 9 constitutes the IC chip mounting surface 1a, and the electrodes 13 and wiring patterns for connecting the IC chip are formed. The electrodes and the wiring pattern are generally formed by screen-printing a metal wiring material such as W or Mo on the surface of a ceramic thin plate and plating Ni or Au thereon.
[0018]
The IC chip 6 has metal bumps 14 such as solder or Au formed on the electrode pads disposed on the lower surface thereof, and is connected to the corresponding electrodes by known flip chip bonding. A narrow gap between the lower surface of the IC chip 6 and the chip mounting surface 1a of the base is filled with an underfill material 15, so that the IC chip is more securely fixed to the base, electrically connected, and the connection portion is protected. ing. In the chip mounting surface 1 a, a gas vent hole 16 that is opened substantially in the center is formed through the first layer 7 and the second layer 8 of the base 1. The gas vent hole 16 is airtightly closed from the outer surface side of the package with a filler 17 as will be described later.
[0019]
As shown in FIG. 2, the underfill material 15 is formed from the tip of the dispenser 18 disposed immediately next to the IC chip 6 after the metal bumps 14 of the IC chip are connected to the corresponding electrodes 13 in the manufacturing process of the piezoelectric device. An appropriate amount is poured into the gap 19 between the chip mounting surface 1a and the lower surface of the IC chip. Air or other gas in the gap 19 is pushed out to the underfill material 15 and is discharged not only from the periphery of the gap opposite to the dispenser 18 but also from the gas vent hole 16, so that it does not remain in the gap. Thereafter, the underfill material 15 is cured by heating at a predetermined temperature for a predetermined time. However, generation of voids can be effectively prevented even with a narrow gap or a narrow pitch bump array. Various conventionally known resin materials are used as the underfill material, and it is appropriate in consideration of conditions such as material injectability, fillet formability, post-curing characteristics, and reliability depending on gaps and IC chip dimensions. Selected.
[0020]
The quartz crystal resonator element 5 is disposed immediately above the IC chip 6, and a pair of connection electrodes 20 drawn out from the excitation electrodes formed on both surfaces thereof to the base end portion are provided on the upper surface of the fourth layer 10 of the base. Each connection terminal 21 is fixed and supported in a cantilever manner and generally horizontally by a conductive adhesive 22 and is electrically connected. Further, a sealing hole 23 is formed in the base 1 through the first layer 7 to the third layer 9 at a position below the free end of the crystal vibrating piece 5, that is, in a region other than the chip mounting surface. And the filler 24 is hermetically closed from the outer surface side of the package.
[0021]
The degassing hole 16 and the sealing hole 23 are formed of a metal ball 17 ′ formed of, for example, a high melting point Pb—Sn solder-based material such as an Au—Sn solder system or 9: 1 solder as a filler. , 24 'are placed on the step 16a, 23a on the outer surface side of the package of each hole, and sealed by batch type vacuum sealing device, laser device, electron beam device or the like. In particular, the sealing hole 23 is finally closed in a vacuum atmosphere after the lid 3 is joined to the base 1 and the frequency of the crystal vibrating piece 5 is finely adjusted by ion beam etching through the sealing hole. Thus, the package 4 can be sealed in a vacuum.
[0022]
3 and 4 show a second embodiment of a piezoelectric device according to the present invention. In this embodiment, the base 1 of the package has a six-layer structure in which a layer 25 made of an insulating thin plate of the same ceramic material is added between the first layer 7 and the second layer 8. A groove 26 is formed in the additional layer 25, thereby forming a passage through which the sealing hole 23 communicates with the gas vent hole 16, and the first layer 7 of the base is provided only at the position of the gas vent hole 16. An opening 7a is formed, and the gas vent hole and the sealing hole communicate with the outside of the package 4 through the common opening. Therefore, in this embodiment, both the holes can be sealed simultaneously and in one step by closing the common opening 7a with the filler 17 as in the first embodiment.
[0023]
In both the first and second embodiments, the base 1 is formed of a laminated structure of ceramic substrates. Therefore, by forming appropriate openings and grooves in each ceramic substrate and combining them, the base 1 is formed. The gas vent hole 16, the sealing hole 23, the space 12, the mount portion of the crystal vibrating piece 5, and the like can be easily formed into a suitable structure.
[0024]
It will be apparent to those skilled in the art that the present invention is not limited to the above-described embodiments and can be implemented with various modifications and changes. For example, the piezoelectric vibrating reed need not necessarily be disposed above the IC chip, and both may be disposed in parallel on the same mounting surface of the base. The base may be a flat substrate instead of a box, and a cavity-type lid may be joined to the base to seal an IC chip or the like in the package. The present invention is also applicable to various piezoelectric devices such as a piezoelectric vibrating piece made of a piezoelectric material other than quartz, a piezoelectric vibrating piece having a different structure such as a tuning fork type, and a SAW device. In addition to piezoelectric devices, the present invention can be applied to various electronic devices in which an IC chip is mounted on a base and hermetically sealed by flip chip bonding using an underfill material.
[0025]
【The invention's effect】
The electronic device package according to the present invention uses the vent hole provided in the mounting surface of the base as described above, so that when the underfill material is filled, the air is removed from the gap between the lower surface of the IC element and the base mounting surface. Since other gases are exhausted completely, it is possible to effectively prevent voids in the underfill material regardless of the narrowing of the gap and the narrowing of the pitch of the bumps. However, a highly reliable electronic device can be realized.
[0026]
Further, according to the piezoelectric device package of the present invention, when the underfill material is filled by using the vent hole provided in the base mounting surface, the gap between the lower surface of the IC element and the base mounting surface is used. Since air and other gases are completely discharged, voids in the underfill material can be effectively prevented regardless of the narrowing of the gap and the narrowing of the pitch of the bumps. A piezoelectric device with high performance and high reliability can be realized while complying.
[Brief description of the drawings]
FIG. 1A is a plan view showing a first embodiment of a piezoelectric device according to the present invention, FIG. 1B is a longitudinal sectional view thereof, and FIG. 1C is a bottom view thereof.
FIG. 2 is a partially enlarged view showing a process of filling an underfill material in a gap between a base and an IC chip.
FIG. 3 is a partially enlarged end view showing a base of a piezoelectric device according to a second embodiment of the present invention.
4 is a bottom view of the base of FIG. 4. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Base 1a Chip mounting surface 2 Seal ring 3 Lid 4 Package 5 Crystal vibrating piece 6 IC chip 7 1st layer 7a Opening 8 2nd layer 9 3rd layer 10 4th layer 11 5th layer 12 Space | gap 13 Electrode 14 Metal bump 15 Underfill material 16 Degassing holes 16a, 23a Step 17 Filler 17 ', 24' Metal ball 18 Dispenser 19 Gap 20 Connection electrode 21 Connection terminal 22 Conductive adhesive 23 Sealing hole 24 Filler 25 Layer 26 Groove

Claims (3)

In a package of a piezoelectric device having a base and a lid joined to the base and hermetically sealing an IC element and a piezoelectric vibrating piece therein,
The IC element is mounted on the mounting surface of the base by flip-chip bonding and fixed with an underfill material, and a gas vent hole communicating with the outside of the package is formed on the lower side of the IC element on the mounting surface. Established,
The base is further provided with a sealing hole communicating with the outside of the package in a region other than the region where the IC element is mounted,
The degassing hole and the sealing hole communicate with a common opening provided on the outer surface of the package, and the common opening is airtightly closed from the outer surface side of the package. Piezoelectric device package. Ri laminated structure der thin plate the base is made of an insulating material, wherein the laminated structure comprises a first layer formed with said common opening, and the second layer forming the gas release openings and the sealing hole, 3. An additional layer provided between the first layer and the second layer and having a groove for communicating the gas vent hole and the sealing hole. Package of the described piezoelectric device. The piezoelectric device package according to claim 2 , wherein the piezoelectric vibrating piece is disposed above the IC element.

Images