KR20010092584A - Prevention apparatus of bulk wave for surface acoustic wave filter - Google Patents

Abstract

PURPOSE: An apparatus for intercepting an internal wave of a SAW(Surface Acoustic Wave) filter is provided to intercept internal wave by forming a groove from an upper face of a substrate to a lower face of the substrate. CONSTITUTION: A package emits internal heat to protect internal circuits and performs a connecting function with external circuits. A substrate(100) is mounted in the package in order to transfer a signal. A bonding pad(105) is mounted on the substrate(100). An input IDT(Inter-Digital Transformer)(101), a ground bar(103), an output IDT(102) are mounted sequentially on an upper portion of the bonding pad(105). The input and the output IDT(101,102), the ground bar(103), and the package are connected electrically by the bonding pad(105). An intercepting groove(110) is formed between an internal edge of the substrate(100) and the bonding pad(105) to intercept the internal wave generated from the inside of the substrate(100).

Description

Internal wave blocking device for surface acoustic wave filter {Prevention apparatus of bulk wave for surface acoustic wave filter}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal wave blocking device for a surface acoustic wave filter. In particular, the present invention relates to an internal wave blocking device of a surface acoustic wave filter. The present invention relates to an internal wave blocking device of a surface acoustic wave filter capable of forming a groove to block internal waves from being directly radiated to both IDTs.

In general, surface acoustic wave (SAW) represents a state of the wave transmitted along the surface of the substrate and has a characteristic of rapidly attenuating in the depth direction. Surface acoustic wave (SAW) filters apply these features as frequency selective devices.

In other words, the SAW device temporarily forms a metal electrode on a highly insulating substrate and applies a piezoelectric twist to the substrate surface. This action causes a physical wave. Since the wave speed passing through the SAW device surface is slower than electromagnetic waves, it is used as a filter to temporarily delay an electric signal or pass only a specific frequency signal.

The SAW filter is a ceramic container that protects a semiconductor device or a function, and is formed in a package form that protects an internal circuit from a harmful environment and provides a means for dissipating heat generated therein and connecting it to the outside.

The SAW filter package is formed by a surface mount production technology, and is suitably used for supporting a wide band transmission such as a CDMA cellular telephone, a wireless LAN, and an image device.

For example, interdigital transducers (hereinafter referred to as IDTs) are installed at the input and output stages to convert electrical signals to mechanical signals when they are recognized during the intermediate frequency filter process in mobile communications components such as PCS or CDMA. When an electrical signal is applied to the piezoelectric object, it is converted into a mechanical signal, and then the output is converted into an electrical signal and outputted, thereby passing a desired frequency band and blocking the remaining band.

1 is a top view showing a configuration of a SAW filter according to the prior art, and FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. 1.

The SAW filter includes an input IDT 11 that recognizes an external electrical signal on the substrate 10 and converts the signal into a mechanical signal, and a desired frequency through which the signal inputted through the input IDT 11 passes through the surface of the substrate 10. The output IDT 12 converts the filtered mechanical signal into an electrical signal so that only the band is passed, and a ground bar 13 disposed between the two IDTs 11 and 12 to perform a grounding operation. do.

By the way, the two IDTs 11 and 12 and the ground bar 13 are bonded to a bonding pad 20.

In FIG. 2, E represents Al electrodes of both IDTs 11 and 12.

The SAW filter configured as described above is output to the output IDT 12 after the filtering function is performed such that a signal input through the input IDT 11 passes only the desired signal through the surface of the substrate 10.

In this case, an internal wave propagating from the input IDT 11 to the output IDT 12 through the inside of the substrate 10 is generated as shown by the arrow of FIG. 2 without passing through the surface of the substrate 10. Since the internal ID proceeds directly from the input IDT 11 to the output IDT 12, the internal wave acts as a noise in the system, thereby hampering the characteristics of the SAW filter.

The present invention has been made to solve the above-mentioned problems of the prior art, the object of which is located between the bonding pad and the four edges of the substrate, the input IDT and the ground bar, the output IDT is installed in order to the bottom direction from the top surface of the substrate As a result, grooves of a certain depth are formed to prevent internal waves generated inside the substrate of the surface acoustic wave filter from being directly radiated to both IDTs, thereby preventing the internal waves from acting as noise in the system, thereby improving the performance of the filter. The present invention provides an internal wave blocking device for a surface acoustic wave filter.

1 is a top view showing the configuration of a SAW filter according to the prior art,

FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. 1;

Figure 3 is a top view showing the configuration of the internal wave blocking device of the surface acoustic wave filter according to the present invention,

4 is a cross-sectional view of FIG.

<Explanation of symbols on main parts of the drawings>

100: substrate 101: input IDT

102: output IDT 103: ground bar

105: bonding pad 110: blocking groove

E: Al electrode

According to a first aspect of an internal wave blocking device of a surface acoustic wave filter according to the present invention for solving the above problems, a substrate mounted in a package to propagate a signal; A pad installed on the substrate to mount the parts and to perform an electrical connection function between each part and the package; An input interdigital converter (hereinafter referred to as IDT) installed on the pad to recognize and convert an external electrical signal into a mechanical signal, and a signal input through the input IDT to pass only a desired frequency band through a surface of a substrate. An output IDT for converting the filtered mechanical signal into an electrical signal, and a ground bar disposed between the two IDTs to perform a grounding operation; Located between the edge of the substrate and the pad and a groove formed in the bottom direction from the upper surface of the substrate comprises a blocking portion for blocking the internal waves generated in the substrate.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 3 is a top view showing the configuration of the internal wave blocking device of the surface acoustic wave filter according to the present invention, Figure 4 is a cross-sectional view of Figure 3 when the present invention, while protecting the internal circuit heat generated inside A package (not shown) that radiates heat and performs an external connection function; A substrate (100) mounted in the package to propagate a signal; The input IDT 101, the ground bar 103, and the output IDT 102 are sequentially mounted on the substrate 100 while being electrically connected between the IDT 101, 102, the ground bar 103, and the package. A bonding pad 105 for performing a function; A blocking groove 110 is formed between the inner edge of the substrate 100 and the bonding pad 105 to block internal waves generated in the substrate.

In particular, the blocking groove 110 has an internal wave generated inside the substrate 100 as shown in FIG. 4 and radiates from the inner surface of the substrate 100 to output the IDT 102 from the input IDT 101. It is formed to have a predetermined depth in the bottom direction of the substrate 100 so as not to be transmitted to.

In addition, the blocking groove 110 may be manufactured by scratching using a harder material than the material of the substrate 100, such as a dicing or a diamond tip.

Meanwhile, the inside of the blocking groove 110 may be filled using materials such as silver epoxy, silicon rubber, polyamide, photoresist, and UV epoxy, which are different materials from the substrate 100.

Reference numeral E not described in FIG. 2 denotes electrodes of the input and output IDTs 101 and 102.

In the operation of the present invention configured as described above, when an input signal is transmitted to the input IDT 101 installed in the bonding pad 105, the output signal is output to the output IDT 102 via the surface of the substrate 100. Some of the signals are radiated into the substrate 100 to generate internal waves.

In this case, when the internal wave is radiated from the inner surface of the substrate 100 and immediately transmitted to the output IDT 102 without passing through the surface of the substrate 100, the internal wave acts as a noise in the system, thereby degrading the filter performance. The blocking groove 110 is formed between the four edges of the substrate 100 and the bonding pad 105 so that a portion thereof is not directly transferred to the output IDT 102.

The blocking groove 110 is recessed at a predetermined depth in the bottom direction from the upper surface of the substrate 100 to block internal waves from directly radiating to the input and output IDTs 101 and 102.

The internal wave blocking device of the surface acoustic wave filter of the present invention configured as described above is positioned between the bonding pads on which the input IDT, the ground bar, and the output IDT are sequentially installed, and the four edges of the substrate. Since grooves are formed to block internal waves generated inside the substrate of the surface acoustic wave filter from being directly radiated to both IDTs, the internal waves are prevented from acting as noise to the system in advance, thereby improving the performance of the filter. have.

Claims (5)

A substrate mounted in the package for propagating signals; A pad installed on the substrate to mount the parts and to perform an electrical connection function between each part and the package; An input interdigital converter (hereinafter referred to as IDT) installed on the pad to recognize and convert an external electrical signal into a mechanical signal, and a signal input through the input IDT to pass only a desired frequency band through a surface of a substrate. An output IDT for converting the filtered mechanical signal into an electrical signal, and a ground bar disposed between the two IDTs to perform a grounding operation; The internal wave blocking device of the surface acoustic wave filter, characterized in that it comprises a blocking portion which is located between the edge of the substrate and the pad in the bottom direction from the upper surface of the substrate to block internal waves generated inside the substrate. The method of claim 1, The blocking means is an internal wave blocking device of the surface acoustic wave filter, characterized in that the manufacturing (Dicing). The method of claim 1, The blocking means is an internal wave blocking device of the surface acoustic wave filter, characterized in that the drawing is made by using a scratching means of a harder material than the substrate material. The method of claim 1, The blocking means is an internal wave blocking device of the surface acoustic wave filter, characterized in that the groove is filled with a different material different from the material of the substrate. The method of claim 4, wherein The heterogeneous material is an internal wave blocking device of a surface acoustic wave filter, characterized in that formed of a material such as epoxy, rubber, photoresist, polyamide.