WO2021143518A1

WO2021143518A1 - Bulk acoustic wave duplex filter

Info

Publication number: WO2021143518A1
Application number: PCT/CN2020/140938
Authority: WO
Inventors: 庞慰; 徐利军
Original assignee: 诺思(天津)微系统有限责任公司
Priority date: 2020-01-16
Filing date: 2020-12-29
Publication date: 2021-07-22
Also published as: CN111162755B; CN111162755A

Abstract

Provided in the present invention is a bulk acoustic wave duplex filter, comprising a substrate, a plastic sealing body and a metal cover. A transmitting filter and a receiving filter are arranged on the substrate at intervals; the plastic sealing body covers the substrate, the transmitting filter and the receiving filter; and the metal cover is arranged at the top of the plastic sealing body and embedded into the plastic sealing body. According to the bulk acoustic wave duplex filter provided by the present invention, the metal cover can block space coupling between the transmitting filter and the receiving filter, thereby improving the isolation and mutual inhibition between a receiving channel and a transmitting channel; in this way, not only can the increase of passband insertion loss be prevented, but the overall size of a chip will not increase significantly and the manufacturing process will not become more complicated; meanwhile, due to the introduction of the metal cover, a heat dissipation path is improved and the power capacity is increased.

Description

A Bulk Acoustic Wave Duplex Filter

Technical field

The present invention relates to the field of communication technology, in particular to a bulk acoustic wave duplex filter.

Background technique

With the rapid development of wireless communication technology, many radio frequency devices have been widely used in the communication field. For example, a large number of filters and duplexers are used in personal mobile terminals such as mobile phones, mainly to filter out unwanted radio frequencies. Signal to improve the performance of the transmitting path or the receiving path. At the same time, in addition to higher requirements on the performance of filters and duplexers, higher requirements are also placed on the volumetric size, and the bulk acoustic wave filter can just meet its requirements. The bulk acoustic wave resonator uses the piezoelectric effect of the piezoelectric crystal to generate resonance. Since resonance is generated by mechanical waves instead of electromagnetic waves as the source of resonance, the wavelength of mechanical waves is much shorter than that of electromagnetic waves. Therefore, the volume of the bulk acoustic wave resonator and the filter composed of it is greatly reduced compared with the traditional electromagnetic filter. On the other hand, since the crystal orientation growth of the piezoelectric crystal can be well controlled at present, the loss of the resonator is extremely small, the quality factor is high, and it can cope with complex design requirements such as steep transition band and low insertion loss. Due to the small size, high roll-off, and low insertion loss of the BAW filter, the filter with this as the core has been widely used in communication systems.

At present, in the face of increasingly crowded frequency resources, frequency selective devices such as filters and duplexers in the RF front-end are required to suppress adjacent frequency bands at a higher level. FBAR devices also need to be improved and improved in this regard. To improve, it is necessary to improve the level of temporary band suppression and isolation without having a greater impact on the insertion loss, and at the same time not to increase the overall size of the chip or device as much as possible.

The common method is to add an inductance with a large inductance on the parallel branch to change the resonant frequency of the resonator to increase the temporary band suppression, or to add additional capacitance or inductance to one or several resonators to increase the suppression point to improve the performance. With suppression. However, these methods require the addition of additional reactive components, and the values of these components are usually relatively large, which is very difficult to implement on the chip. If it is realized by winding wires on the substrate or adding discrete components outside the chip, the number and size of the substrate will inevitably increase, which will inevitably lead to an increase in the overall size of the filter or duplexer. Moreover, the added windings or discrete components are not ideal in practice, and the losses introduced by them will be superimposed on the filter, resulting in the deterioration of the overall insertion loss of the filter.

In summary, the above method will lead to an increase in chip loss and a substantial increase in the overall size of the chip while improving the immediate band suppression and isolation. Therefore, without increasing the overall size of the chip, how to improve the short-band suppression and transmission and reception isolation of the duplexer while increasing the power capacity of the duplexer is still a technical problem to be solved.

Summary of the invention

In view of this, the bulk acoustic wave duplex filter provided by the present invention can block the spatial coupling between the transmitting filter and the receiving filter through the metal cover, thereby improving the relationship between the receiving channel and the transmitting channel. The isolation and mutual inhibition.

To achieve the above objective, according to one aspect of the present invention, a bulk acoustic wave duplex filter is provided.

A bulk acoustic wave duplex filter provided by the present invention includes a substrate, a plastic package and a metal cover, wherein:

A transmitting filter and a receiving filter are arranged on the substrate at intervals;

The plastic package covers the substrate and the transmitting filter and receiving filter;

The metal cover is arranged on the top of the plastic package body and is embedded in the plastic package body.

Optionally, the metal cover includes a first metal plate and at least one second metal plate disposed at the bottom of the first metal plate.

Optionally, the second metal plate is vertically arranged at the bottom of the first metal plate, and the second metal plate is embedded in the plastic package.

Optionally, the metal cover includes one of the first metal plate and one of the second metal plate, the second metal plate is connected to the center of the bottom of the first metal plate, and the first metal plate A T-shaped metal cover is formed with the second metal plate.

Optionally, the transmitting filter and the receiving filter are respectively located on both sides of the second metal plate.

Optionally, the metal cover includes one first metal plate and three second metal plates, and both ends and the center of the bottom of the first metal plate are connected with the second metal plates, And the first metal plate and the second metal plate form an inverted mountain-shaped metal cover.

Optionally, two adjacent second metal plates and the first metal plate form an accommodating space, and the transmitting filter and the receiving filter are respectively located in the adjacent accommodating spaces.

Optionally, the first metal plate is located directly above the transmitting filter and the receiving filter, and the distance between the first metal plate and the transmitting filter and the receiving filter is greater than 100μm.

Optionally, the distance between the transmitting filter and the receiving filter is greater than 150 μm.

Optionally, the substrate is made of organic material; the package body is made of epoxy resin.

According to the technical solution of the present invention, the spatial coupling between the transmitting filter and the receiving filter can be blocked by the metal cover, thereby improving the isolation and mutual inhibition between the receiving channel and the transmitting channel, and It does not cause an increase in passband insertion loss, a large increase in the overall size of the chip and an increase in the complexity of the manufacturing process, and at the same time, the introduction of the metal cover can also improve the heat dissipation path and increase the power capacity.

Description of the drawings

The drawings are used to better understand the present invention, and do not constitute an improper limitation of the present invention. in:

FIG. 1 is a schematic diagram of the structure of a bulk acoustic wave duplex filter in the prior art;

2 is a schematic diagram of a structure of a bulk acoustic wave duplex filter according to an embodiment of the present invention;

Fig. 3 is another structural schematic diagram of a bulk acoustic wave duplex filter according to an embodiment of the present invention;

Figure 4 is a comparison diagram of the isolation curves of Figure 1 and Figure 2;

Fig. 5 is a comparison diagram of the transmission characteristic curves of Fig. 1 and Fig. 2.

Among them, 1-substrate, 2-plastic package, 3-transmitting filter, 4-receiving filter, 5-solder ball, 71-first metal plate, 72-second metal plate.

Detailed ways

The following describes exemplary embodiments of the present invention with reference to the accompanying drawings, which include various details of the embodiments of the present invention to facilitate understanding, and should be regarded as merely exemplary. Therefore, those of ordinary skill in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention. Likewise, for clarity and conciseness, descriptions of well-known functions and structures are omitted in the following description.

As shown in Figure 1 is a bulk acoustic wave duplex filter in the prior art. When the transmitting filter 3 works, the electromagnetic waves radiated from it will enter the receiving filter 4 through spatial coupling, which will affect the normal operation of the receiving filter 4. The spatial coupling between the filter 3 and the receiving filter 4 can be equivalent to a capacitor, and this capacitor will inevitably affect the isolation between the receiving and sending channels, thereby causing deterioration of the isolation and mutual suppression between the receiving channel and the transmitting channel.

The present invention makes an improvement to this. As shown in FIG. 2, FIG. 2 is a structural diagram of a bulk acoustic wave duplex filter according to an embodiment of the present invention. The filter includes a substrate 1, a plastic package 2 and a metal cover, wherein, The substrate 1 is provided with a transmitting filter 3 and a receiving filter 4 at intervals; the plastic package 2 covers the substrate 1 and the transmitting filter 3 and the receiving filter 4; the metal cover is set on the top of the plastic package 2 and is embedded in the plastic package 2 Inside.

According to the structure shown in FIG. 2, by providing a metal cover on the top of the package, and blocking the spatial coupling between the transmitting filter 3 and the receiving filter 4 by the metal cover, the relationship between the receiving channel and the transmitting channel is improved. Isolation and mutual inhibition, and will neither increase the passband insertion loss, nor cause a significant increase in the overall size of the chip and increase in the complexity of the manufacturing process. At the same time, the introduction of the metal cover can also improve the heat dissipation path. Improve power capacity.

The emission filter 3 is a bulk acoustic wave emission filter, and the emission filter 3 includes an emission filter chip, and the emission filter chip is connected to the substrate 1 through solder balls 5 in a flip-chip form.

The receiving filter 4 is a bulk acoustic wave receiving filter, and the receiving filter 4 includes a receiving filter chip, and the receiving filter chip is connected to the substrate 1 through solder balls 5 in a flip-chip form.

The material of the substrate 1 can be organic materials or ceramics. On the one hand, the substrate 1 can carry the transmitting filter chip and the receiving filter chip. On the other hand, the substrate 1 can also be provided with a metal layer for electrical connection.

The plastic package 2 is generally made of epoxy resin. The transmitting filter 3 and the receiving filter 4 can be plastically sealed to protect the transmitting filter chip and the receiving filter chip from damage by external forces. At the same time, it can also isolate moisture from the environment. The change affects the performance of the transmitting filter 3 and the receiving filter 4.

The substrate 1 may completely cover the top of the plastic package 2 or partly cover the top of the plastic package 2.

In the embodiment of the present invention, the metal cover may include a first metal plate 71 and at least one second metal plate 72 disposed at the bottom of the first metal plate 71.

The number of the second metal plates 72 may be one or more. The number of the second metal plates 72 can be set according to actual needs.

In the embodiment of the present invention, the second metal plate 72 may be vertically arranged at the bottom of the first metal plate 71, and the second metal plate 72 is embedded in the plastic package body 2. The bottom of the first metal plate 71 is connected to the top of the second metal plate 72. The bottom of the second metal plate 72 may be in contact with the substrate 1 or may be located above the substrate 1.

As shown in FIG. 2, in the embodiment of the present invention, the metal cover includes a first metal plate 71 and a second metal plate 72 (the first metal plate 71 and the second metal plate 72 are perpendicular to each other). A second metal plate 72 is connected to the center of the bottom of the 71, and the first metal plate 71 and the second metal plate 72 form a T-shaped metal cover. The transmitting filter 3 and the receiving filter 4 are respectively located on both sides of the second metal plate 72.

The first metal plate 71 and the second metal plate 72 separate the transmitting filter 3 and the receiving filter 4, which can prevent the spatial coupling between the transmitting filter 3 and the receiving filter 4, so that the transmitting filter 3 and the receiving filter The devices 4 will not affect each other.

As shown in FIG. 3, in the embodiment of the present invention, the metal cover includes a first metal plate 71 and three second metal plates 72. The two ends and the center of the first metal plate 71 are connected with the second metal plate 71. The metal plate 72, and the first metal plate 71 and the second metal plate 72 form an inverted mountain-shaped metal cover.

The three second metal plates 72 are arranged in parallel and at equal intervals, wherein one second metal plate 72 is located in the middle of the first metal plate 71, and the second metal plate 72 separates the transmitting filter 3 from the receiving filter 4; The two second metal plates 72 are respectively located at both ends of the first metal plate 71.

The two adjacent second metal plates 72 and the first metal plate 71 form an accommodating space, and the transmitting filter 3 and the receiving filter 4 are respectively located in the adjacent accommodating spaces. Since the transmitting filter 3 and the receiving filter 4 are respectively located in different accommodation spaces, the spatial coupling between the transmitting filter 3 and the receiving filter 4 can be effectively prevented, thereby making the transmitting filter 3 and the receiving filter 4 Will not affect each other.

In the embodiment of the present invention, the first metal plate 71 may be located directly above the transmitting filter 3 and the receiving filter 4, and the distance between the first metal plate 71 and the transmitting filter 3 and the receiving filter 4 is greater than 100 μm . The distance between the transmitting filter 3 and the receiving filter 4 may be greater than 150 μm.

Test example

In order to illustrate the actual effect of the bulk acoustic wave duplex filter of the present invention, the bulk acoustic wave duplex filter shown in FIG. 1 and the bulk acoustic wave duplex filter shown in FIG. 2 of the embodiment of the present invention are used in the prior art. In comparison, the following results are obtained.

Fig. 4 is a comparison diagram of isolation curves, the solid line is the isolation curve corresponding to Fig. 1, and the dashed line is the isolation curve corresponding to Fig. 2 of the present invention. It can be clearly seen that the isolation of the dotted line is obviously better than the solid line in the two frequency ranges of 880MHz to 915MHz and 925MHz to 960MHz of interest. Therefore, it can be explained that the bulk acoustic wave duplex filter in the embodiment of the present application can help improve isolation.

Fig. 5 is a comparison diagram of transmission characteristic curves, the solid line is the curve corresponding to Fig. 1, and the dashed line is the curve corresponding to Fig. 2 of the present invention. It can be seen that the mutual suppression of the dotted lines in the two frequency bands of 880MHz ~ 915MHz and 925MHz ~ 960MHz has also been improved.

In addition, since the thermal conductivity of metal is much higher than that of epoxy resin, for example, the thermal conductivity of copper is 401W/mk and epoxy resin is 0.3W/mk. Therefore, the bulk acoustic wave duplex filter provided by this application can greatly improve the heat dissipation effect. Therefore, the power capacity has also been greatly improved.

Therefore, the bulk acoustic wave duplex filter provided by the present invention can not only improve the isolation of the duplexer, but also improve the heat dissipation, without increasing the size and complexity of the transceiver filter. The purpose of the power capacity of the duplexer.

The foregoing specific implementations do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that, depending on design requirements and other factors, various modifications, combinations, sub-combinations, and substitutions can occur. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

A bulk acoustic wave duplex filter, which is characterized by comprising a substrate, a plastic package and a metal cover, wherein:

A transmitting filter and a receiving filter are arranged on the substrate at intervals;

The plastic package covers the substrate and the transmitting filter and receiving filter;

The metal cover is arranged on the top of the plastic package body and is embedded in the plastic package body.
The bulk acoustic wave duplex filter according to claim 1, wherein the metal cover comprises a first metal plate and at least one second metal plate disposed at the bottom of the first metal plate.
3. The bulk acoustic wave duplex filter according to claim 2, wherein the second metal plate is vertically arranged at the bottom of the first metal plate, and the second metal plate is embedded in the plastic package.
The bulk acoustic wave duplex filter according to claim 3, wherein the metal cover comprises one of the first metal plate and one of the second metal plate, and the bottom center of the first metal plate is connected with The second metal plate, and the first metal plate and the second metal plate form a T-shaped metal cover.
The bulk acoustic wave duplex filter according to claim 4, wherein the transmitting filter and the receiving filter are respectively located on both sides of the second metal plate.
The bulk acoustic wave duplex filter according to claim 3, wherein the metal cover comprises one of the first metal plate and three of the second metal plates, and both ends on the bottom of the first metal plate And the center is connected with the second metal plate, and the first metal plate and the second metal plate form an inverted mountain-shaped metal cover.
The bulk acoustic wave duplex filter according to claim 6, wherein two adjacent second metal plates and the first metal plate form an accommodation space, and the transmitting filter and the receiving filter They are respectively located in adjacent accommodation spaces.
The bulk acoustic wave duplex filter according to claim 1, wherein the first metal plate is located directly above the transmitting filter and the receiving filter, and the first metal plate and the transmitting filter The distance between the filter and the receiving filter is greater than 100 μm.
The bulk acoustic wave duplex filter according to claim 1, wherein the distance between the transmitting filter and the receiving filter is greater than 150 μm.
The bulk acoustic wave duplex filter according to claim 1, wherein the substrate is made of organic material; and the package body is made of epoxy resin.