Packaging structure and component installation method for oscillator

Abstract

Disclosed are a packaging structure of an oscillator and a method for installing components in the packaging structure. Fluid capillarity and surface tension are utilized so that both the dimension of the oscillator can be reduced and the contamination of the piezoelectric components of the oscillator can be avoided at the same time. The packaging structure includes a platform having a top surface and a bottom surface, a number of side rims on the circumstance of the top surface extending upward for a distance and forming a top-open space with the top surface that can receive at least a piezoelectric component; a top cover sealing the top-open space into a closed and airtight space; a circuit placed beneath the bottom surface that can attach at least an electronic component, a number of pillars of a same length positioned on the circuit; a bottom cover having an adhesive injection aperture and joining the pillars to form a partially open space, and a malleable material filling the partially open space through the aperture.

Description

FIELD OF THE INVENTION

The present invention generally relates to the frequency control devices and, more specifically, to the packaging structure and the method of component installation for an oscillator.

BACKGROUND OF THE INVENTION

Temperature compensated crystal oscillators (TCXO) are commonly used for frequency control in electronic devices. As a stable and reliable frequency output device, a typical TCXO includes a piezoelectric component, usually a quartz crystal, and a temperature compensation circuit. A TCXO is especially applicable to high-frequency mobile electronic devices such as mobile handsets, pagers, and wireless modems. Because these mobile electronic devices are getting more and more compact and light-weighted, a packaging structure for the TCXO has to be adapted to this trend as well.

FIG. 1 is a perspective view of a packaging structure of a temperature compensated crystal oscillator (TCXO) 100 according to a prior art. As shown in FIG. 1, the TCXO 100 includes a piezoelectric component 101, a temperature compensation integrated circuit (IC) 102, a number of capacitors 103, an input/output pad (not shown in FIG. 1), a top cover 104, and a casing 105 receiving the foregoing components and forming a closed space therein when sealed with the top cover 104.

A characteristic of the piezoelectric component is that, when a stress is applied on the piezoelectric component, an electric charge is produced on the surface of the piezoelectric component and, thereby, a potential difference is developed. On the other hand, when the piezoelectric component is placed within an electric field, a deformation of the piezoelectric component is developed and the piezoelectric component, thereby, generates a radio frequency.

Accordingly, when a voltage is applied on the piezoelectric component 101, the piezoelectric component 101 generates a resonance frequency. The resonance frequency, however, will suffer a slight drift in frequency when the temperature within the casing 105 varies. A temperature compensation device, usually in the form of a temperature compensation IC, is hence placed inside the casing 105 to adjust the voltage applied to the piezoelectric component in response to the environmental temperature.

The temperature compensation IC 102 and other electronic components are usually coated with a layer of epoxy resin for protection sake. However, because the piezoelectric component 101 is also housed in the same closed space inside the casing 105, the epoxy resin would contaminate the piezoelectric component 101 and further result in a deviation of the resonance frequency of the piezoelectric component 101.

Another packaging structure of a TCXO solving the epoxy resin contamination problem according to a prior art is shown in FIGS. 2A and 2B.

FIG. 2A is a cross-sectional view of a packaging structure of a TCXO 200 according to another prior art. A principle component of the TCXO 200 is a platform 201. The platform 201 has a number of sides 202 on the circumference of the platform 201 extending outward perpendicularly to the platform 201. The sides 202 and the platform 201 jointly form a top-open space 204. The sides 202 have a number of metallic contact holes for electrical connection to external circuits (not shown in FIG. 2A). Similarly the platform 201 has a number of sides 203 on the circumference of the platform 201 extending outward perpendicularly to the platform 201 in a direction opposite to the sides 202. The sides 203 and the platform 201 jointly form a bottom-open space 205. A temperature compensation IC 206 and a number of capacitors 207 are placed on the platform 201 inside the top-open space 204. A piezoelectric component 208 is placed beneath the platform 201 inside the bottom-open space 205. The bottom-open space 205 is then further sealed into a closed space by a bottom cover 209. When the electronic components 206 and 207 are coated with the epoxy resin, the piezoelectric component 208 is not contaminated because it is separated by the platform 201 and hidden inside the closed space 205. A stability and reliability of the resonance frequency generated by the piezoelectric component 208 is therefore maintained.

However the foregoing structure would encounter limitations and difficulties when attempting to reduce the dimension and volume of the TCXO 200.

FIG. 2B is a top view of the packaging structure of FIG. 2A. As shown in FIG. 2B, there are a number of soldering pads 211 on top of the sides 202. The soldering pads 211 are for soldering the TCXO 200 onto a circuit board of the electronic device where the TCXO 200 is used. The soldering pads 211 are required to have a certain area size for the soldering process. When attempting to reduce the dimension and volume of the TCXO 200, therefore, most of the reduction has to be on the platform 201. Because the area for the temperature compensation IC 206 and other electronic components are reduced, it would increase the difficulties in installing the temperature compensation IC 206 and other electronic components, which in turn would result in an increase of production cost and a lower yield.

In summary, the packaging structures of a TCXO according to prior arts cannot allow the reduction of the dimension of a TCXO and the avoidance of the contamination of the piezoelectric component at the same time. The present invention therefore provides a packaging structure of an oscillator and a method for installing components in the packaging structure so that the dilemma between dimension reduction and contamination avoidance of a TCXO can both be resolved satisfactorily. The structure and method can be further applied to the packages of other types of oscillators or similar semiconducting devices.

SUMMARY OF THE INVENTION

The present invention provides a packaging structure of an oscillator and a method for installing components in the packaging structure of the oscillator. The present invention utilizes the theories of fluid capillarity and surface tension so that the dimension of an oscillator can be reduced and the contamination of the piezoelectric component can be avoided as well. The packaging structure of the present invention includes a platform having a top surface and a bottom surface; a plurality of side rims on the circumstance of the top surface extending outward for a distance perpendicularly to the top surface and forming a top-open space with the top surface that can receive at least a piezoelectric component; a top cover sealing the top-open space into a closed space; a circuit placed beneath the bottom surface that can be installed with at least an electronic component; a plurality of pillars of a same length positioned on the circuit; a bottom cover having an adhesive injection aperture and joining the pillars to form a partially open space; and a malleable material filling the partially open space through the adhesive injection aperture.

The method of installing components in the packaging structure of the present invention includes the steps of providing a packaging structure having a top-open space and a bottom surface beneath the top-open space, sealing a piezoelectric component in the top-open space, attaching a plurality of electronic components to the bottom surface, preparing a plurality of pillars beneath the bottom surface, joining a cover having an adhesive injection aperture with the pillars to form a partially open space, filling a malleable material into the partially open space through the adhesive injection aperture, and adjusting the frequency of the piezoelectric component.

The foregoing and other objects, features, aspects and advantages of the present invention will become better understood from a careful reading of a detailed description provided herein below with appropriate reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a packaging structure of a temperature compensated crystal oscillator (TCXO) according to a prior art.

FIG. 2A is a cross-sectional view of a packaging structure of a TCXO according to another prior art.

FIG. 2B is a top view of the packaging structure of FIG. 2A

FIG. 3 is a perspective, exploded view of a packaging structure according to a preferred embodiment of the present invention.

FIG. 4 is another perspective, exploded view of the packaging structure of FIG. 3, wherein the viewing angle is from the bottom.

FIG. 5 is a perspective view showing part of the sequence of forming the packaging structure of FIG. 3.

FIG. 6A is a cross-sectional view showing a malleable material is to be injected into the packaging structure of FIG. 3.

FIG. 6B shows the packaging structure of FIG. 6A after the packaging structure is filled with the malleable material.

FIG. 6C shows the packaging structure of FIG. 6A after the packaging structure is filled with the malleable material of an amount different from that of FIG. 6B.

FIG. 7 is a perspective view of the packaging structure of FIG. 3 after the malleable material is injected and solidified.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the present invention is depicted from FIGS. 3 to 7.

FIG. 3 is a perspective, exploded view of a packaging structure according to a preferred embodiment of the present invention. As shown in FIG. 3, a packaging structure of an oscillator 300 according to a preferred embodiment of the present invention comprises a platform 301, a piezoelectric component 310, an integrated circuit 350 (not shown in FIG. 3), a top cover 320, a plurality of pillars 330, and a bottom cover 340.

The platform 301 is made of a ceramic material and further comprises a top surface 302, a bottom surface 307 (not shown in FIG. 3), and a plurality of side surfaces 305. The circumference of the top surface 302 extends outward for a distance perpendicularly to the top surface 302 and forms a plurality of side rims 303. On the side rims 303, there is a plurality of soldering pads 309, which can be either metallic pads having a specific thickness or metal-plated films having a thinner thickness. The soldering pads 309 shown in FIG. 3 are metal-plated films. The top surface 302 and the side rims 303 of the platform 301 jointly form a top-open space. Within this top-open space and on top of the top surface 302, there is a plurality of soldering pads 304. A piezoelectric component 310 having a plurality of soldering pads 312 and electrodes 311 is made of an AT-CUT quartz crystal or other similar materials. The piezoelectric component 310 is attached to the top surface 302 and electrical contacts between the soldering pads 304, the soldering pad 312, and electrodes 311 are thereby established. The piezoelectric component 310 is therefore electrically connected to a plurality of electrodes 306 on the side surfaces 305 or a circuit 308 (not shown in FIG. 3) of the platform 301.

The top cover 320 is placed on the top-open space formed by the platform 301 and the side rims 303. After putting the assembly formed by the top cover 320 and the platform 301 through a high temperature, the top cove 320 and the soldering pads 309 on top of the side rims 303 are jointed together, and the top-open space is thereby sealed into a closed and airtight space that can receives the piezoelectric component 310 completely. The top cover 320 comprises a metal.

FIG. 4 is another perspective, exploded view of the packaging structure of FIG. 3, wherein the viewing angle is from the bottom. As shown in FIG. 4, on the bottom surface 307 of the platform 301, the circuit 308 is installed with a plurality of capacitors 351 and an integrated circuit 350. The capacitors 351 and the integrated circuit 350 are interconnected via a plurality of metallic wires 352. The integrated circuit 350 can be a temperature compensation integrated circuit. In addition, a plurality of pillars 330 is attached to the circuit 308 beneath the bottom surface 307. The pillars 330 are of a same length between 200 μm and 1000 μm, and comprise a conducting material.

FIG. 5 is a perspective view showing part of a sequence of forming the packaging structure of FIG. 3. As shown in FIG. 5, the bottom cover 340 can be made of a ceramic material or a material for making printed circuit boards. The bottom cover 340 has an adhesive injection aperture 341 and a plurality of soldering pads 342. An equal number of the soldering pads 342 are on a top surface and a bottom surface of the bottom cover 340 respectively. Each of the soldering pads 342 is electrically connected to a corresponding soldering pad on the other surface of the bottom cover 340. Also, as shown in FIG. 5, by joining the pillars 330 with the soldering pads 342 of the bottom cover 340, a partially open space is formed. The electronic components received in this partially open space can be connected to an external circuit with the soldering pads 342.

FIG. 6A is a cross-sectional view showing a malleable material is to be injected into the partially open space formed between the bottom cover 340 and the bottom surface 307 of the platform 301. As shown in FIG. 6, after the top cover 320 and the bottom cover 340 are attached to the platform 301, a malleable material 401 is injected by a syringe through the adhesive injection aperture 341 into the partially open space formed between the bottom surface 307 and the bottom cover 340. The malleable material can be an epoxy resin. Because the height of the partially open space is determined by the length of the pillars 330, which is between 200 μm and 1000 μm, the injected malleable material 401 would fill the entire partially open space through a capillary effect of the malleable material 401. Moreover, the malleable material 401 will be stopped at the edges of the partially open space by a surface tension of the malleable material 401. Depending on the amount of the injected malleable material 401, either a concave structure as shown in FIG. 6B or a bulged structure as shown in FIG. 6C can be formed. The capillarity and surface tension effects of the malleable material 401 allow a tolerance in the amount of injected malleable material 401, which can increase a yield rate of the oscillator 300.

FIG. 7 is a perspective view of the packaging structure according to the preferred embodiment of the present invention after the malleable material is injected and solidified. After the partially open space is filled with the malleable material 401, a heating procedure is conducted to evaporate a solvent of the malleable material 401. The malleable material 401 is then solidified as shown in FIG. 7. At last, the oscillator 300 is tested and has its output frequency fine-tuned. A packaging structure of the oscillator 300 according to the present invention is thereby accomplished.

The foregoing packaging structure of an oscillator and the method for installing its components provided by the present invention can be applied to temperature compensated crystal oscillators, other types of oscillators, or even semiconducting devices.

Although the present invention has been described with reference to the preferred embodiment, it will be understood that the present invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.

Claims

1. A packaging structure for an oscillator comprising:

a platform having a top surface and a bottom surface;

a plurality of side rims on a circumference of said top surface extending outward for a distance perpendicularly to said top surface, and jointly forming a top-open space along with said top surface, wherein said top-open space receives at least a piezoelectric component;

a top cover sealing said top-open space into a closed space;

a circuit beneath said bottom surface comprising at least an electronic component;

a plurality of pillars of a same length dispersed on said circuit;

a bottom cover attaching to said pillars and jointly forming a partially open space along with said bottom surface, wherein bottom cover has an adhesive injection aperture; and

a malleable material filling said partially open space.

2. The packaging structure for an oscillator according to claim 1, wherein said platform further comprises a plurality of side surfaces each having a plurality of electrodes for electrically connecting said circuit on said bottom surface to an external circuit.

3. The packaging structure for an oscillator according to claim 1, wherein said platform is made of a ceramic material.

4. The packaging structure for an oscillator according to claim 1, wherein said plurality of side rims have a plurality of soldering pads on top of said side rims for attaching to said top cover.

5. The packaging structure for an oscillator according to claim 4, wherein said plurality of soldering pads are made of a metal with a specific thickness or a metal-plated film.

6. The packaging structure for an oscillator according to claim 1, wherein said piezoelectric component is an AT-CUT quartz crystal.

7. The packaging structure for an oscillator according to claim 1, wherein said at least an electronic component is an integrated circuit.

8. The packaging structure for an oscillator according to claim 1, wherein said at least an electronic component comprises an integrated circuit and at least a capacitor.

9. The packaging structure for an oscillator according to claim 1, wherein said top cover comprises a metal.

10. The packaging structure for an oscillator according to claim 1, wherein said plurality of pillars comprise a conducting material.

11. The packaging structure for an oscillator according to claim 1, wherein said bottom cover is made of a ceramic material.

12. The packaging structure for an oscillator according to claim 1, wherein said bottom cover is made of a material for making printed circuit boards.

13. The packaging structure for an oscillator according to claim 1, wherein said bottom cover further comprises a top surface and a bottom surface, each having a plurality of soldering pads for electrically connecting said plurality of pillars to an external circuit.

14. The packaging structure for an oscillator according to claim 1, wherein said malleable material is epoxy resin.

15. The packaging structure for an oscillator according to claim 1, wherein said malleable material is confined by a capillarity and surface tension of said malleable material within said partially open space formed by said bottom cover, said pillars, and said bottom surface.

16. A method for installing components in a packaging structure of an oscillator comprising the steps of:

providing a packaging structure having a top-open space and a bottom surface;

attaching and sealing a piezoelectric component in said partially open space;

attaching a plurality of electronic components on said bottom surface of said packaging structure;

providing a plurality of pillars beneath said bottom surface of said packaging structure;

attaching a bottom cover to said pillars to form a partially open space, said bottom cover having an adhesive injection aperture;

filling a malleable material in said partially open space through said adhesive injection aperture; and

adjusting an output frequency and functionality of said oscillator.