CN113810020A

CN113810020A - Filter structure

Info

Publication number: CN113810020A
Application number: CN202110994467.2A
Authority: CN
Inventors: 余明伦; 林欣汉; 曾柏翔; 陈俊仁; 吕世文
Original assignee: Advanced Semiconductor Engineering Inc
Current assignee: Advanced Semiconductor Engineering Inc
Priority date: 2021-08-27
Filing date: 2021-08-27
Publication date: 2021-12-17

Abstract

The invention relates to a filter structure, the filter structure comprises: a base plate with a first surface and a second surface arranged oppositely; a filter with a first part and a second part, the first part and the second part are respectively arranged on the base plate the first and second surfaces. Wherein, the first part and the second part are electrically connected through through holes embedded in the substrate. The above technical solutions can at least maintain the performance of the SAW filter in the process of miniaturizing the filter structure.

Description

Filter structure

Technical Field

The invention relates to the technical field of semiconductors, in particular to a filter structure.

Background

Wireless communication products involve signal reception and transmission, and in order to ensure signal quality, different numbers of filters are used in system design. One of the filters is a surface acoustic Wave (SAW filter). Surface acoustic waves are mechanical waves with unique properties that when traveling along the crystal surface, the energy decays exponentially in the direction perpendicular to the crystal surface, and when deeper than one wavelength depth, the energy density drops to 1/10 at the surface. Since the energy of the wave is concentrated on the crystal surface, the surface acoustic wave element can easily utilize the energy carried by the wave.

Surface acoustic waves are typically excited using interdigital transducers (IDTs), which may be of intermediate thickness

The aluminum electrode is formed on the surface of a substrate made of piezoelectric single crystal materials through a photoetching technology, when voltage is applied to a positive electrode and a negative electrode of a transducer, an electric field is generated between the fingers, the surface of the piezoelectric substrate generates synchronous coupled up-and-down vibration under the action of the electric field to excite surface acoustic waves, and when the distance between the fingers of the same level is equal to the wavelength of the surface acoustic waves, the excited surface acoustic waves have the maximum efficiency; the performance and area of the SAW filter are directly related to each other, and unless the process technology or the material technology is developed, the area of the SAW filter cannot be effectively reduced in consideration of the miniaturization of the electronic components.

Disclosure of Invention

In view of the above problems in the related art, the present invention provides a filter structure to maintain the performance of a SAW filter during the miniaturization of the filter structure.

According to an aspect of an embodiment of the present invention, there is provided a filter structure including: a substrate having a first surface and a second surface oppositely disposed; a filter having a first portion and a second portion disposed at the first surface and the second surface of the substrate, respectively. The first part and the second part are electrically connected through a through hole embedded in the substrate.

In some embodiments, the first surface and the second surface are provided with a first pad and a second pad, respectively, electrically connected to the via, wherein the first pad and the second pad are connected to the first portion and the second portion, respectively.

In some embodiments, the first and second surfaces are provided with a moulding over the first and second portions respectively. In some embodiments, one of the first surface and the second surface of the substrate is provided with a connector electrically connected to the through hole, wherein the connector is exposed by the molding. In some embodiments, the surface of the molding is provided with a protective layer.

In some embodiments, the areas of the first portion and the second portion are substantially the same.

In some embodiments, the filter is a surface acoustic wave filter. In some embodiments, the filter is formed from a plurality of transducer structures, the first portion comprising a portion of the plurality of transducer structures and the second portion comprising another portion of the plurality of transducer structures.

In some embodiments, the through-holes include at least two through-holes that are offset from each other in a direction from the first surface to the second surface.

In some embodiments, any one of the first and second portions comprises a plurality of transducer structures, wherein a trace for interconnecting at least part of the plurality of transducer structures is further provided at the respective first or second surface.

According to another aspect of the embodiments of the present invention, there is provided a filter structure including: the substrate is provided with a first surface and a second surface which are oppositely arranged, and a through hole and a grounding wire are buried in the substrate; a filter having a first portion and a second portion disposed at the first surface and the second surface of the substrate, respectively. The first portion and the second portion are electrically connected through a through hole, and an inductor is connected between the through hole and the grounding wire.

In some embodiments, the filter structure further comprises: and a molding covering the first part and the second part. In some embodiments, the filter structure further comprises: and a connecting member on one of the first surface and the second surface of the substrate, wherein the connecting member is electrically connected to the through hole, and the connecting member is exposed by the molding. In some embodiments, the filter structure further comprises: and the protective layer covers the surface of the molding object far away from the substrate.

In some embodiments, the first portion and the second portion have substantially the same area.

Drawings

Various aspects of the invention are best understood from the following detailed description when read with the accompanying drawing figures. It should be noted that, in accordance with standard practice in the industry, the various components are not drawn to scale. In fact, the dimensions of the various elements may be arbitrarily increased or reduced for clarity of discussion.

Fig. 1A is a schematic diagram of a filter structure according to an embodiment of the invention.

Fig. 1B shows a partial enlarged view of the second part in fig. 1A.

Figure 2 is a schematic circuit connection diagram of a filter having multiple transducers according to some embodiments of the present invention.

Fig. 3A and 3B are schematic diagrams of an embodiment in which the filter is divided into two parts.

Fig. 4 is a schematic perspective view of a filter structure according to an embodiment of the invention.

Fig. 5 is a schematic diagram illustrating a simulation of the filtering effect of the filter structure according to the embodiment of the present invention.

Fig. 6 is a schematic diagram of a filter structure according to an embodiment of the invention.

Fig. 7 is a simulation diagram of the filtering effect of a SAW filter with 2 transducers.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, in the following description, forming a first feature over or on a second feature may include embodiments in which the first and second features are in direct contact, as well as embodiments in which additional features are formed between the first and second features such that the first and second features may not be in direct contact. Moreover, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

A filter structure is provided according to an embodiment of the invention. Fig. 1A is a schematic diagram of a filter structure 100 according to an embodiment of the invention. As shown in fig. 1A, the filter structure 100 includes a substrate 110, the substrate 110 having a first surface (e.g., an upper surface) 111 and a second surface (e.g., a lower surface) 112 disposed opposite to each other. The present invention divides the filter 120 into the first and

second portions

121 and 122, and the first and

second portions

121 and 122 are disposed at the first and

second surfaces

111 and 112 of the substrate, respectively. In some embodiments, the areas of the first portion 121 and the second portion 122 may be substantially the same. In other embodiments, the filter 120 may be divided in any suitable manner, and the filter 120 may be divided into the first portion 121 and the second portion 122 having different areas. In some embodiments, the first portion 121 is disposed opposite the second portion 122. In some embodiments, the filter 120 may be a SAW filter, and the first portion 121 and the second portion 122 may be two portions of the SAW filter.

The first portion 121 and the second portion 122 are electrically connected through the via hole 115 embedded in the substrate 110. In the illustrated embodiment, the through-holes 115 include at least two through-holes that are offset from each other in a direction from the first surface 111 to the second surface 121 to electrically connect the first portion 121 and the second portion 122. In some embodiments, the first portion 121 and the second portion 122 may also be electrically connected by traces (not shown) embedded in the substrate 110. It is to be understood that the first portion 121 and the second portion 122 may be electrically connected by any suitable arrangement of vias and traces, as the invention is not limited in this respect.

The technical scheme of the invention provides a double-sided surface acoustic wave filter, which is mainly used for disassembling the SAW filter into a first part 121 and a second part 122 with equivalent areas in order to meet the progress of miniaturization of electronic elements, the first part 121 and the second part 122 are respectively arranged on a first surface 111 and a second surface 112 above and below a substrate 110, and the first part 121 and the second part 122 are electrically connected through a through hole 115 and a trace which are embedded in the substrate 110, so that the substrate area occupied by the SAW filter is reduced, and the efficiency of the SAW filter is not influenced.

Fig. 1B shows a partial enlarged view of the second part in fig. 1A. Referring to FIG. 1B, the second portion 122 may include a plurality of transducers 191 located on a substrate 190. The plurality of transducers 191 are covered by a cover layer 194, such as a dielectric material. A plurality of transducers 191 are located at the bottom of a cavity 195 defined by walls 192 on the cover layer 194. A cover 198 is disposed over the wall 192, the cover 198 covering the cavity 195. Conductive posts 196 pass through wall 192 and are electrically connected to transducer 191 by conductive material 199. Solder balls 197 are disposed on top of the conductive posts 196 so that the transducers 191 in the second portion 122 can be electrically connected to other components. The first portion of the filter may have a similar structure as described with reference to fig. 1B and will not be described again here.

Referring back to fig. 1A, the substrate 110 is further provided at the first surface 111 and the second surface 112 with a first pad 116 and a second pad 118, respectively, which are electrically connected to the via 115. The first pads 116 and the second pads 118 are connected to a first portion 121 and a second portion 122 of a filter 120, respectively, by solder balls 119.

The first and

second surfaces

111 and 112 are further provided with a molding 140 covering the first and

second portions

121 and 122, respectively. In the illustrated embodiment, a connection 149 is provided at the second surface 112 of the substrate 110. The connecting member 149 is electrically connected to the through hole 115. The connection 149 is exposed by the molding 140. In addition, the surface of the mold 140 may be further provided with a protective layer 150. In the illustrated embodiment, the protective layer 150 covers the top surface and sidewalls of the molding 140 on the first surface 111, and also extends over the sidewalls of the substrate 110 and the sidewalls of the molding 140 at the second surface 112.

In the filter structure 100 provided by the present invention, the divided SAW filters may be respectively disposed on the upper and lower surfaces (the first Surface 111 and the second Surface 112) of the substrate 110 by a Surface Mount Technology (SMT) method, and the first Surface 111 and the second Surface 112 are electrically connected by a via 115 and a trace embedded in the substrate 110, so as to form a double-side SAW filter. In addition, the mold 140 is used to mold the first surface 111 and the second surface 112 of the substrate 110, and then a singulation process is performed, and finally the protection layer 150 is formed outside the mold 140 by a sputtering (sputter) process. The substrate area occupied by the thus formed double-sided SAW filter is reduced by 50% compared to a conventional single-side SAW filter.

Fig. 2 is a circuit schematic diagram of a filter having multiple transducers (IDTs) according to some embodiments of the present invention. Fig. 3A and 3B are schematic diagrams of an embodiment in which the filter is divided into two parts. In the example shown in fig. 2, the filter 120 is formed by seven transducers 191 connected. As shown in fig. 3A and 3B, the 7 transducers 191 may be divided into two parts, with the first part 121 comprising one of the plurality of transducers (e.g., 4 of the 7 transducers) and the second part 12 of the filter comprising another of the plurality of transducer structures (e.g., another 3 of the 7 transducers). The plurality of transducers 191 in the first portion 121 and the plurality of transducers 191 in the second portion 122 are disposed at the first surface 111 and the second surface 112 (refer to fig. 1A) of the substrate 110, respectively. The area occupied by the filter having 7 IDTs is approximately 811 × 516, and the filter having 7 IDTs can be divided into two parts having the same area. In one embodiment, as in FIG. 3A, dividing the filter into a first portion 121 includes 4 transducers 191 occupying an area of about 400x 546; the second section 122 includes 3 transducers 191 occupying an area of about 400x 431. In another embodiment, as shown in FIG. 3B, the filter is divided into a first portion 121 comprising 3 transducers 191 occupying an area of about 400x 400 and a second portion 122 comprising 4 transducers 191 occupying an area of about 400x 694. In other embodiments, the filter may be divided in other suitable manners, and the areas of the divided first portion 121 and the divided second portion 122 may be substantially the same or different.

Fig. 4 is a schematic perspective view of a filter structure according to an embodiment of the invention. As shown in fig. 4, the plurality of transducers 191 of the filter are disposed at the first surface (uppermost surface) 111 and the second surface (lowermost surface) 112, respectively. The transducer 191 at the first surface 111 may be connected to the transducer 191 at the second surface 112 through a plurality of through holes 115 extending in the vertical direction. Traces 114 for interconnecting at least some of the plurality of transducers 191 are also provided at the first surface 111 or the second surface 112.

Fig. 5 is a result of a simulation (simulation) of the filtering effect of the filter structure according to an embodiment of the present invention. As can be seen from the simulation results of fig. 5, the filtering effect of the double-sided SAW filter (shown by the curve S51) is comparable to that of the single-sided SAW filter (shown by the curve S52). Therefore, the SAW filter is divided into two parts, one part is arranged on the upper surface of the substrate, the other part is arranged on the lower surface, the double-side SAW filter can reduce the area by about 50 percent compared with the single-side SAW filter, and the performance is similar to or even better than that of the single-side SAW filter.

On the other hand, impedance matching of a circuit is important for a high-frequency circuit, the Q value of an inductance structure used in the matching circuit affects the loss of the high-frequency circuit, and the larger the Q value of the inductance structure is, the smaller the insertion loss of the SAW filter is, and therefore, the general SAW filter is connected to an inductance structure provided on the surface of a substrate at an output end to enhance a filter effect. However, the inductor provided on the surface of the substrate is too bulky, and this is a problem in the progress of miniaturization of electronic devices. Therefore, in some embodiments, as shown in the filter structure 200 shown in fig. 6, the through holes embedded in the substrate 110 are further used as the inductors 160 with spiral structures, and the through holes are connected to the first portion 121 and the second portion 122 of the filter 120 on the first surface 111 and the second surface 112 of the substrate. As shown in fig. 6, the inductor 160 may be disposed at ground GND. Other aspects of the filter structure 200 shown in fig. 6 may be similar to those discussed with reference to fig. 1A, and the same reference numerals are used for similar components and will not be repeated here.

This may further enhance the filtering effect of the SAW filter and filter out unwanted waves. As shown in FIG. 7, the SAW filter of 2 transducers of FIG. 7, wherein Zs is the series configuration of the internal transducers and Zp is the parallel configuration, wherein Zs has a waveform of S71 line segment and Zp has a waveform of S72 line segment, which are combined into a filtered waveform S73 for frequencies of 2

Is passed through. The through hole embedded in the substrate is used as an inductor with a spiral structure for filtering the waveform

The left side is connected with

The right wave is filtered out. In addition, the inductance structure which is originally arranged on the surface of the substrate and is electrically connected with the SAW filter is embedded into the substrate, so that the occupied area of the substrate can be further reduced, and the aim of miniaturization is fulfilled.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.

Claims

1. A filter structure, comprising:

a substrate having a first surface and a second surface oppositely disposed;

a filter having a first portion and a second portion disposed at the first surface and the second surface of the substrate, respectively;

wherein the first portion and the second portion are electrically connected by a through hole embedded in the substrate.

2. The filter structure according to claim 1,

the first surface and the second surface are respectively provided with a first bonding pad and a second bonding pad which are electrically connected with the through holes, wherein the first bonding pad and the second bonding pad are respectively connected with the first part and the second part.

3. A filter structure according to claim 1, characterized in that the first and second surfaces are provided with a moulding covering the first and second parts, respectively.

4. The filter structure according to claim 3, wherein one of the first surface and the second surface of the substrate is provided with a connector electrically connected to the through hole, wherein the connector is exposed by the mold.

5. A filter structure according to claim 3, characterized in that the surface of the moulding is provided with a protective layer.

6. The filter structure according to claim 1, characterized in that the areas of the first and second portions are substantially the same.

7. The filter structure according to claim 1, characterized in that the filter is a surface acoustic wave filter.

8. The filter structure of claim 7, wherein the filter is formed from a plurality of transducer structures, the first portion comprising a portion of the plurality of transducer structures, the second portion comprising another portion of the plurality of transducer structures.

9. The filter structure according to claim 1, wherein the through-holes comprise at least two through-holes offset from each other in a direction from the first surface to the second surface.

10. The filter structure according to claim 1, wherein any one of the first portion and the second portion comprises a plurality of transducer structures, wherein further traces for interconnecting at least parts of the plurality of transducer structures are provided at the respective first surface or the second surface.

11. A filter structure, comprising:

the circuit board comprises a substrate, a first circuit board and a second circuit board, wherein the substrate is provided with a first surface and a second surface which are oppositely arranged, and a through hole and a grounding wire are buried in the substrate;

wherein the first portion and the second portion are electrically connected by the via, and an inductor is connected between the via and the ground line.

12. The filter structure according to claim 11,

13. The filter structure of claim 11, further comprising:

a molding encasing the first portion and the second portion.

14. The filter structure of claim 13, further comprising:

a connector on one of the first surface and the second surface of the substrate, wherein the connector is electrically connected to the through hole, and the connector is exposed by the molding.

15. The filter structure of claim 13, further comprising:

a protective layer covering a surface of the molding remote from the substrate.

16. The filter structure according to claim 11, characterized in that the first portion and the second portion have substantially the same area.

17. The filter structure according to claim 11, characterized in that the filter is a surface acoustic wave filter.

18. The filter structure of claim 17, wherein the filter is formed from a plurality of transducer structures, the first portion comprising a portion of the plurality of transducer structures, the second portion comprising another portion of the plurality of transducer structures.

19. The filter structure according to claim 11, wherein the through-holes comprise at least two through-holes offset from each other in a direction from the first surface to the second surface.

20. The filter structure according to claim 11, wherein any one of the first and second portions comprises a plurality of transducer structures, wherein further traces for interconnecting at least parts of the plurality of transducer structures are provided at the respective first or second surface.