JPH09186550A - Chip mount base, package using it and surface acoustic wave filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a package in which an electric short-circuit is interrupted and noise invasion is prevented by providing individual grounding electrodes apart from each other to the mount base. SOLUTION: A mount substrate 1 is made of an insulation material and usually a package 2 of a SAW filter, various circuits and an IC or the like are mounted, and a common ground electrode 1a is provided to a lower side. The package 2 is made up of a package lower body 11 whose middle part is recessed as a hollow rectangular parallelepiped making of an insulation material such as ceramic, plastic, alumina or BT resin, and of a cover 19. Die pads 12b, 12c apart horizontally independently with a middle surface of a bottom wall 12 as a border are formed to a package lower part 11 by means of metallic plating. Furthermore, the chip 3 of the SAW filter is placed so as to be bridged over both the die pads 12b, 12c.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip mounting base for mounting a chip such as an elastic wave (SAW) filter used in a wireless telephone or the like, a package using the chip mounting base, and an elastic wave filter device.

[0002]

BACKGROUND ART FIG. 7 is a schematic view showing a structure of a chip of a conventional elastic wave filter, a piezoelectric substrate in the drawing 20 is formed of a high dielectric material having a piezoelectric effect such as LiTaO _3, 2
1, 22, 23, and 24 are IDTs (Inter Digital Transd
ucer) forming comb-shaped electrodes. Each of the comb-shaped electrodes 21, 22, 23, 24 has a trunk portion 2 which is a conductive portion.
A plurality of tooth portions 21b, 22b, 23b, 24b, which are conductive portions, are extended in parallel from one side of 1a, 22a, 23a, 24a in a comb shape.

The comb-teeth-shaped electrodes 21 and 22 and the comb-teeth-shaped electrodes 23 and 24 face their tooth portions 21b and 22b, 23b and 24b, respectively, and are in non-contact with each other between other tooth portions. It is combined to be located in the state,
Comb-shaped electrodes 21 and 2 are formed on the surface of a rectangular piezoelectric substrate 20.
2, 23 and 24 with their teeth 21b, 22b, 23b, 2
The extending directions of 4b are parallel to each other, and the tooth portion 21
They are arranged at a predetermined interval in the arrangement direction of b to 24b.

The comb-teeth electrodes 21 and 22 form an input-side electrode set, and the comb-teeth electrodes 23 and 24 form an output-side electrode set. The comb-teeth electrode 21 has one end at its trunk portion 21a. Is connected to the signal source via the other end A of the lead wire, and the comb-shaped electrode 23 is connected to the receiving portion (load) via the other end C of the lead wire whose one end is connected to the trunk portion 23a. The other comb-teeth-shaped electrodes 22 and 24 of the electrode set are the trunk portions 22a and 2
The other ends B and D of the lead wire, one end of which is connected to 4a, are connected to the ground electrode.

In such a SAW filter, if an electric signal in a predetermined frequency band is applied from the signal source to the comb-teeth-shaped electrode 21 on the input side, the electric signal is obtained.
Flowing between the tooth portions 21b and 22b of the above, and at this time, the piezoelectric substrate 20 is also energized. As a result, vibration is generated in the piezoelectric substrate 20, and a sound wave accompanying this is propagated from the input side to the output side on the surface of the piezoelectric substrate 20. When the propagated sound wave reaches the comb-teeth-shaped electrodes 23 and 24 on the output side, it is converted into an electric signal corresponding to the sound wave, and the tooth portions 23 of both comb-teeth-shaped electrodes 23 and 24.
An electric current is applied between b and 24b, and is applied to the load through the comb-shaped electrode 23.

In this way, in the process of converting an electric signal into a sound wave on the input side and re-converting from a sound wave to an electric signal on the output side, a predetermined input is made by the filter action due to the characteristics of the comb-shaped electrodes 21 to 24. From the electric signals in the frequency band, only the signal in the predetermined specific frequency band is selected and output.

By the way, the chip 3 of the SAW filter as shown in FIG. 7 is usually housed in the package 2 as shown in FIGS. 8 and 9 and mounted on the mounting substrate 1 as shown in FIG. 8 is a cross-sectional view of the central portion of the package 2 on which the chip 3 is mounted, FIG. 9 is a vertical cross-sectional view of a position near one end of the package 2, and FIG. 10A is a diagram of the package 2 and the mounting substrate 1 on which the package 2 is mounted. A plan view and FIG. 10B are sectional views taken along line XX of FIG. The package 2 includes a package lower body 11 and a lid 19. Package lower body 1
Reference numeral 1 denotes a bottomed rectangular tube, and the bottom wall 12 has a die pad 12a, which is a grounding electrode, on the entire upper surface thereof.
However, they are molded and fixed by means such as metal plating.

Further, on the pair of corresponding side walls 13 and 14 of the package lower body 11, metal pads (only the central portion is shown in FIG. 8) are provided at positions near the central portion and both ends thereof, respectively, as shown in FIGS. , And metal pads near one end appear in FIG. 9) 13a, 13b, 13d, 13e, metal pads 14a, 14b, 14d, 14e are molded and fixed by means such as metal plating, and each side wall In 13 and 14,
Upper and lower metal pads 13a and 13b, 13d and 13
e, through holes 13c, 13f, 14 for electrically connecting the metal pads 14a and 14b, 14d and 14e.
c and 14f are provided.

The chip 3 of the SAW filter as shown in FIG. 7 is placed on the die pad 12a as shown in FIGS. 8 and 9, and the comb-teeth-shaped electrodes 21 constituting the electrode group on the input side are shown in FIG. As shown, the metal pad 13a is connected to the metal pad 13a via the bonding wire 4a, and the comb-teeth-shaped electrode 23 forming the electrode set on the output side is connected to the metal pad 14a via the bonding wire 5a. Further, the other comb-teeth-shaped electrodes 22 and 24 of each set are also connected to the metal pads 13d and 14d provided at positions near one end of the side walls 13 and 14 via the bonding wires 4b and 5b as shown in FIG. ing.

The metal pads 13a and 14a are connected to the metal pad 1 through the through holes 13c and 14c as shown in FIG.
3b, 14b, and these metal pads 13
b and 14b are connected to the microstrip lines 1d and 1e on the mounting substrate 1 as shown in FIG. 10A through the pins (not shown) of the package 3 lower body 11.
The metal pads 13d and 14d are mounted on the mounting substrate 1 as shown in FIG.
Is connected to the metal pads 13e and 14e through the through holes 13f and 14f in the die pad 1 and
2a is also connected. Metal pads 13e, 14e
Is the through hole 1 in the mounting substrate 1 as shown in FIG.
It is connected to the ground electrode 1a formed on the lower surface of the mounting substrate 1 via b and 1c (or pins).

As shown in FIG. 10, the mounting substrate 1 is formed in a plate shape using an insulating material, a ground electrode 1a is formed on the lower surface, and two microstrip lines 1d and 1e are formed on the upper surface. The microstrip lines 1d and 1e are arranged in a straight line, and one ends of the two microstrip lines 1d and 1e face each other with a predetermined gap therebetween, and the other ends are connected to a signal source or a load (not shown). The chip 3 is housed in the package 2, and the pads 13b and 14b forming the input end and the output end of the package 2 shown in FIG. 8 are connected to the respective ends of the microstrip lines 1d and 1e through pins (not shown). The pads 13d and 14d shown in FIG. 9 are connected to the die pad 12a through the through holes 13f and 14f, and also the metal pads 13e and 14e, the pins (not shown) of the package 2 and the through holes 1b and 1 of the mounting substrate 1.
It is connected to the ground electrode 1a through c.

FIG. 11 is an explanatory view showing a transmission path of an electric signal between the chip 3 of the conventional SAW filter, the die pad 12a of the package 2 on which the SAW filter is mounted, and the ground electrode 1a of the mounting substrate 1. The electric signal of the predetermined frequency band output from the signal source receives the metal pad 1 as an input terminal.
3b, through hole 13c, metal pad 13
a, through the bonding wire 4a to the comb-teeth electrodes 21 and 22 shown in FIG. The tooth portions 21b and 22b of the comb-teeth electrodes 21 and 22 are not in contact with each other, but are located very close to each other, the impedance between them is extremely small, and the electric signals are comb-teeth electrodes 21 and 22. Flowing between the tooth portions 21b and 22b of the above, and at this time, the piezoelectric substrate 20 is also energized.

As a result, vibration is generated in the piezoelectric substrate 20, and the sound wave generated thereby is propagated to the output side on the surface of the piezoelectric substrate 20. However, the comb-shaped electrodes 21 and 22
The electric signal flowing to the
Die pad 12a through through holes 13c and 14f
Flow through the through holes 13f, 14f, etc., to the ground electrode 1a on the lower surface of the mounting substrate 1, while another flow directly through the die pad 12a to the output side. It is applied to the load via the tooth portions 23b and 24b.

[0014]

By the way, the comb-teeth-shaped electrodes 21 and 22 on the input side are converted into sound waves and propagated to the output side as sound waves on the surface of the piezoelectric substrate 20. The signals converted into electric signals again by the electrodes 23 and 24 are in a filtered state, but propagated from the comb-shaped electrodes 21 and 22 to the comb-shaped electrodes 23 and 24 through the die pad 12a. There is a problem that the electric signal is not filtered and a sufficient filtering function cannot be obtained.

The inventors of the present invention have conducted experiments and studies in order to solve such a problem. As a result, it is possible to eliminate noise by connecting each of a plurality of electrodes to be grounded in the chip to an individual grounding electrode. However, it was found to be extremely effective in achieving high isolation.

The present invention has been made on the basis of such knowledge. A first object of the present invention is to install a chip capable of preventing an ingress of noise by blocking an electrical short circuit path by a grounding electrode near the chip. It is to provide a base and a package used for the base.

The second purpose is to achieve high isolation by connecting one of the comb-teeth-shaped electrodes on the input side and the output side of the acoustic wave filter to an individual grounding electrode provided on the installation table. Another object of the present invention is to provide the elastic wave filter device.

[0018]

According to a first aspect of the present invention, there is provided a chip mounting table for mounting a chip having at least two electrodes to be grounded, the mounting table comprising: It is characterized in that it is provided with separate grounding electrodes which are separated from each other and which are to be connected to the respective electrodes to be grounded. In the first invention, since the grounding electrodes are spatially separated, an unnecessary electric signal is transmitted from one electrode to the other electrode through the grounding electrode, which causes noise. The inconvenience is eliminated.

The grounding electrode of the chip mounting table according to the second invention is a die pad on which the chip is mounted. According to the second aspect of the invention, the die pads of the chip mounting base are spatially separated by this, so that an unnecessary electric signal is transmitted from one electrode to the other electrode via this, and becomes a noise. Inconveniences such as are eliminated.

The chip mounted on the chip mount according to the third aspect of the invention is characterized by being an elastic wave filter. In the third invention, this can improve the performance as an elastic wave filter.

A package according to a fourth aspect of the invention is characterized by including the chip mounting base according to the first, second or third aspect. According to the fourth aspect of the invention, high isolation can be achieved as a package of the acoustic wave filter without increasing man-hours.

The elastic filtered device according to the fifth invention is
An acoustic wave filter chip comprising two pairs of comb-teeth-shaped electrodes, which are combined so that their tooth portions are located between other tooth portions, and are arranged at a required interval on a piezoelectric substrate, It is placed on an installation table provided with two separate grounding electrodes, and one comb tooth-shaped electrode of each set is connected to each of the individual grounding electrodes of the installation table. And According to the fifth aspect of the invention, since one of the comb-shaped electrodes on each of the input side and the output side is connected to each of the two electrically separated grounding electrodes, the input of the acoustic wave filter is can avoid a disadvantage that electrical signals from the comb-shaped electrode on the side to the comb-shaped electrode through the grounding electrode output side is directly transmitted, it may achieve high isolation of.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION A chip mounting table, a package and an elastic wave filter device using the same according to the present invention will be specifically described below with reference to the drawings showing the embodiments. 1 is a schematic vertical sectional view of a central portion of a package accommodating a chip of an acoustic wave filter according to the present invention, FIG. 2 is a cross-sectional plan view taken along line II-II of FIG. 1, and FIG. 3 is III-II of FIG.
FIG. 4 is a vertical cross-sectional view taken along line I, and FIG. 4 is a partially cutaway perspective view taken along line IV-IV in FIG.
AW) filter package, reference numeral 3 denotes an acoustic wave filter chip.

The mounting substrate 1 is formed of an insulating material, and is usually equipped with various circuits, ICs, etc. in addition to the SAW filter package 2, and has a common ground electrode 1a on its lower surface. There is. The package 2 is composed of a package lower body (installation table) 11 and a lid 19 which are hollow rectangular parallelepiped and are made of an insulating material such as ceramic, plastic, alumina, and BT resin.

In the package lower body 11, the die pads 12b and 12c are formed separately by means of metal plating or the like so as to be separated left and right independently of each other with the center portion of the surface of the bottom wall 12 as a boundary. S in the form of straddling 12c
The chip 3 of the AW filter is mounted. The structure of the chip 3 of the SAW filter is substantially the same as that of the conventional one shown in FIG. 7, and the input side is provided on the upper surface of the piezoelectric substrate 20 formed in the shape of a rectangular parallelepiped plate using a piezoelectric material having a high dielectric constant. , Comb-teeth-shaped electrodes 21 and 22 that form electrode pairs on the output side and 2
3, 24 are arranged. Each comb-shaped electrode 2
Reference numerals 1 to 24 denote conductive trunk portions 21a to 24a, respectively, and a large number of conductive tooth portions 21b to 24 extending from each of them in a comb-like shape.
b. The tooth portions 21b and 2 of each of the comb-shaped electrodes 21 to 24
2b, 23b and 24b face each other, and are combined so that each tooth portion is positioned in a non-contact state between other tooth portions, and the trunk portions 21a and 23a and 22a and 24a are placed on substantially the same straight line. The comb-teeth electrodes 21, 22 and the comb-teeth electrodes 23, 24 are arranged at a predetermined interval in the arrangement direction of the tooth portions 21b to 24b.

The stem portion 21a of the comb-tooth-shaped electrode 21 on the input side of the chip 3 is connected to the metal pad 13a arranged at the center of the upper surface of the side wall 13 via the bonding wire 4a as shown in FIG. The trunk portions 23a of the comb-shaped electrodes 23 are connected to the metal pads 14a arranged at the center of the upper surface of the side wall 14 via the bonding wires 5a. Further, each other comb-shaped electrode 2 on the input side and the output side
2, 24 have sidewalls 13 via bonding wires 4b, 5b, one ends of which are connected to the trunks 22a, 24a,
Metal pads 13d, 1 arranged on the upper surface near one end of 14
4d. The metal pads 13a, 14
a, the electrical connection mode after the metal pads 13d and 14d are as shown in FIG.

FIG. 5 shows the die pads 12b and 12c and the metal pads 13a and 14 in the package 2 described above.
It is a schematic diagram which shows arrangement | positioning of a, 13d, 14d, a through hole, etc., and an electrical connection mode. As is apparent from FIG. 5, the pair of side walls 13 and 14 of the package 2 facing each other have the above-mentioned metal pads 13a and 14a at the center of the upper surface and the metal pads 13b and 14b at the center of the lower surface facing the side walls 13 and 14 respectively.
Are disposed between the metal pads 13a and 13b, and 14a and 1b.
4b are electrically connected by through holes 13c and 14c, respectively.

Metal pads 13d and 14d are provided on the upper surfaces of the pair of side walls 13 and 14 near one end side, and metal pads 13e and 14e are provided on the lower surfaces facing each other, and between the metal pads 13d and 13e, 14d and 14e are electrically connected by through holes 13f and 14f, respectively. Further, metal pads 13g and 14g are provided on the upper surfaces of the pair of side walls 13 and 14 near the other ends, and metal pads 13h and 14h are provided on the lower surfaces facing each other, and between the metal pads 13g and 13h, 14g, The 14h are electrically connected through through holes 13i and 14i, respectively.

Further, connection pieces protruding from the die pad 12b are provided on the through holes 13f and 13i provided on both sides of the side walls 13 and 14 and above and below the through holes 13f and 13i, and on the through holes 14f and 14i. Connection pieces protruding from the die pad 12c are in contact with the lower middle portion, respectively, and are electrically connected to each other. Metal pads 13b, 13e, 13h, 14 provided on the lower surfaces of the side walls 13, 14 of the package 2 facing each other
b, 14e, and 14h are electrically connected to pins (not shown), and when the package 2 is mounted on the mounting board 1, the pins connected to the metal pads 13b and 14b are connected to the microstrip line 1d on the surface of the mounting board 1. , 1e, and the pins electrically connected to the metal pads 13e and 13h and the metal pads 14e and 14h are the mounting substrate 1
Through holes 1b, 1c (metal pads 14e, 14h)
The mounting board 1 is mounted so as to be electrically connected to the ground electrode 1a via a through hole to which the pin connected to is connected.

Therefore, when the package 2 is mounted on the mounting substrate 1, the comb-teeth-shaped electrode 21 on the input side has a metal pad 13a, a through hole 13c, a metal pad 13b and a pin (not shown) connected to the bonding wire 4a. It is electrically connected to the microstrip line 1d as shown in FIG. 10 (a) via the, and the microstrip line 1d is connected to a signal source (not shown). Further, the comb-teeth-shaped electrode 23 on the output side is provided with a microstrip line 1e as shown in FIG. 10A via the metal pad 14a connected to the bonding wire 5a, the through hole 14c, the metal pad 14b and a pin (not shown). Is electrically connected to the receiving section (load) (not shown) through the microstrip line 1e.

On the other hand, the comb-teeth-shaped electrode 22 on the input side and the comb-teeth-shaped electrode 24 on the output side have the above-described bonding wires 4b and 5b.
metal pads 13d and 14d connected to b, and die pads 12b and 12c separated from each other through through holes 13f and 14f, respectively, and the through holes 13f and 14f, metal pads 13e and 14e, and these metals. It is electrically connected to the ground electrode 1a through the pins connected to the pads 13e and 14e and the through holes 1b and 1c of the mounting substrate 1. The comb-shaped electrodes 22 and 24 and the die pads 12b and 12c may be electrically connected directly via a bonding wire or through a through hole.

FIG. 6 shows the chip 3 and the die pads 12b and 12c in the package lower body 11 which is a chip mounting table.
It is explanatory drawing which shows the propagation path of the electric signal between the mounting board 1 and. An electric signal of a predetermined frequency band output from the signal source is input to the metal pad 13b which is an input terminal from the microstrip line 1d, and the comb-teeth electrode 21 on the surface of the chip 3 through the through hole 13c, the metal pad 13a, and the bonding wire 4a. An electric signal is transmitted to.

Tooth portion 21 of comb-shaped electrodes 21 and 22 on the input side
Since a large number of b and 22b are located close to each other, the impedance between them is extremely small, and the electric signal input to the comb-shaped electrode 21 is
It is also transmitted to 2. At that time, the piezoelectric substrate 20 is also energized, and the piezoelectric substrate 20 vibrates to generate a sound wave. The generated sound wave propagates to the output side on the surface of the piezoelectric substrate 20.

At this time, as described above, a part of the electric signal to be transmitted from the comb-teeth electrodes 21 to 22 is transmitted to the die pad 12b via the bonding wire 4b having one end connected to the comb-teeth electrode 22. But die pad 12
Since b and 12c are separated, they directly flow to the ground electrode 1a of the mounting substrate 1 and are prevented from transmitting an electric signal directly to the output side. That is, the electrical signal on the input side is prevented from being short-circuited to the output side as it is through the die pad 12b near the chip 3.

On the other hand, on the output side, the sound wave reaching between the comb-teeth electrodes 23, 24 is converted into an electric signal corresponding to the sound wave, and one end of the bonding wire 5 is connected to the comb-teeth electrode 23.
It is output to the outside from the microstrip line 1e via a, the metal pad 14a, the through hole 14c, and the metal pad 14b which is an output terminal. During this time, the electric signal in the predetermined frequency band input from the signal source is the electric signal → sound wave →
In the process of being converted into an electric signal, only an electric signal having a predetermined frequency is applied to the load.

Although the die pads 12b and 12c are both connected to the ground electrode 1a provided on the lower surface of the mounting substrate 1, since the connection is made at a location distant from the chip 3, this causes noise. Comb-shaped electrode 23,
Rarely is it output directly through 24. Of course, if necessary, the ground electrode 1a on the lower surface of the mounting substrate 1 may be divided into two, and each may be connected to another grounding electrode.

Next, the comparison test results of the package as the installation table according to the present invention and the conventional package will be described. Simulations were carried out on the device of the present invention as shown in FIGS. 1 to 5 and the conventional device as shown in FIGS. 6 to 11 to obtain respective isolations. As a result, in the device of the present invention, when the frequency signal of 1.9 GHz was input from the input side, the isolation strength between the input side and the output side was 38 dB. Under the same conditions, the isolation strength of the conventional device was 29 dB, and it was confirmed that the device of the present invention significantly improved the isolation as compared with the conventional device.

[0038]

In the chip mount according to the first, second and third aspects of the present invention, it is possible to prevent the inconvenience that noise is directly transmitted from the input end side to the output end side through the ground electrode. .

According to the fourth aspect of the invention, high isolation of the package can be achieved without increasing the number of manufacturing steps of the package.

In the fifth invention, it is prevented that the electric signal is directly transmitted from the comb-teeth electrode on the input side through the grounding electrode to the comb-teeth electrode on the output side and the function as the acoustic wave filter is deteriorated. And high isolation can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view of a package accommodating a chip of an acoustic wave filter according to the present invention.

FIG. 2 is a cross-sectional plan view taken along the line II-II of FIG.

FIG. 3 is a vertical sectional view taken along the line III-III in FIG.

4 is a partially cutaway perspective view taken along the line IV-IV of FIG.

FIG. 5 is a schematic view showing the arrangement and electrical connection of die pads, metal pads, through holes in a package.

FIG. 6 is an explanatory diagram showing a transmission path of an electric signal according to the embodiment of the present invention.

FIG. 7 is a schematic diagram of a general acoustic wave filter.

FIG. 8 is a schematic vertical sectional view of a central portion of a package of a conventional acoustic wave filter.

FIG. 9 is a schematic vertical sectional view of a conventional acoustic wave filter package, which is closer to one side.

FIG. 10 is a schematic plan view and a cross-sectional view showing a state in which a package is mounted on a mounting board.

FIG. 11 is an explanatory view showing a transmission path of an electric signal between a chip and a package of a conventional acoustic wave filter.

[Explanation of symbols]

1 Mounting Substrate 1a Ground Electrode 2 Package 3 Chip 4a, 4b, 5a, 5b Bonding Wire 11 Package Lower Body 12 Bottom Wall 12b, 12c Die Pad 13, 14 Sidewall 13a, 13b, 13d, 13e, 13g, 13h Metal Pad 13c, 13f , 13i Through hole 14a, 14b, 14d, 14e, 14g, 14h Metal pad 14c, 14f, 13i Through hole 20 Piezoelectric substrate 21, 22, 23, 24 Comb-shaped electrode

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yatsuo Harada 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd.

Claims (5)

[Claims] 1. An installation table for mounting a chip having at least two electrodes to be grounded, wherein the installation table is a mutually spaced position to which each of the electrodes of the chip to be grounded should be connected. A chip mounting table, which is provided with another grounding electrode. 2. The chip mount base according to claim 1, wherein the ground electrode is a die pad on which the chip is mounted. 3. The chip mount base according to claim 1, wherein the chip is a chip made of an acoustic wave filter. 4. A package comprising the chip installation base according to claim 1, 2, or 3. 5. A combination of a pair of comb-teeth-shaped electrodes on a piezoelectric substrate such that their tooth portions are located between other tooth portions.
The acoustic wave filter chips, which are formed by arranging the sets at a required interval, are placed on an installation table provided with two separate grounding electrodes, and one of the comb-shaped electrodes of each set is placed. Are connected to the separate grounding electrodes of the installation table, respectively.