Surface acoustic wave filter chip with protection structure

Abstract

The utility model relates to the field of surface acoustic wave filters, in particular to a surface acoustic wave filter chip with a protection structure. The protection structure of the surface acoustic wave filter chip comprises a cover plate wafer and the surface acoustic wave filter chip, the surface acoustic wave filter chip comprises a piezo-electric crystal, an interdigital transducer and an electrode, wherein the interdigital transducer and the electrode are arranged on the piezo-electric crystal; the electrodes are arranged on the two sides of the interdigital transducer; a metal supporting part is arranged on the electrode; the cover plate wafer comprises a wafer layer and a metal layer; the cover plate wafer is arranged above the interdigital transducer and the electrode, and the metal layer of the cover plate wafer is connected with the electrode through the metal supporting part. The protection structure of the surface acoustic wave filter chip is simple in structure and low in cost, has a good protection effect on the surface acoustic wave filter chip, prevents an interdigital transducer from being damaged in the assembly process, and ensures the stability of the chip.

Description

Technical Field

[0001] The utility model relates to the field of surface acoustic wave filters, in particular to a surface acoustic wave filter chip with a protection structure. Background Art

[0002] A surface acoustic wave (SAW) filter is a filter that propagates energy on the surface of a material. When an electrical signal is input into the input port, it is converted into mechanical energy through the inverse piezoelectric effect of the piezoelectric substrate and propagates across the substrate in the form of a surface acoustic wave. When the SAW signal reaches the output transducer, it is converted back into an electrical signal through the piezoelectric effect of the piezoelectric substrate and output. The frequency response and pulse response between the interdigital transducers are used to achieve filtering, delay, and sensing functions. Therefore, the surfaces of the interdigital electrodes of a SAW filter must not come into contact with or be covered by any material, and the electrodes must not be scratched, as this will affect the performance and reliability of the SAW filter.

[0003] Surface acoustic wave (SAW) filters are finding increasingly widespread use, widely employed in various modular devices for frequency-selective filtering. To meet the demands of modular devices for miniaturization, high integration, and low cost, modules are now moving toward high-integration, miniaturized bare chip designs. Some modules no longer utilize packaged SAW filters, but instead utilize bare SAW filter chips.

[0004] In view of this, the present utility model is proposed. Utility Model Content

[0005] In order to solve the technical problem that the interdigital transducer of the existing surface acoustic wave filter chip is easily damaged during the assembly process, the utility model provides a surface acoustic wave filter chip with a protective structure, including a cover wafer and a surface acoustic wave filter chip. The protective structure of the surface acoustic wave filter chip has the advantages of simple structure, low cost, good chip protection effect, and improved chip stability.

[0006] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0007] A surface acoustic wave filter chip with a protective structure, comprising a cover wafer and a surface acoustic wave filter chip;

[0008] The surface acoustic wave filter chip includes: a piezoelectric crystal and an interdigital transducer and an electrode arranged on the piezoelectric crystal; the electrodes are arranged on both sides of the interdigital transducer; and a metal support portion is arranged on the electrode;

[0009] The cover wafer includes: a wafer layer and a metal layer; the cover wafer is arranged above the interdigital transducer and the electrode, and the metal layer of the cover wafer is connected to the electrode through the metal support portion.

[0010] The protective structure of the surface acoustic wave filter chip has a simple structure and low cost, has a good protective effect on the surface acoustic wave filter chip, prevents the interdigital transducer from being damaged during the assembly process, and ensures the stability of the chip.

[0011] Preferably, the thickness of the metal layer is ≥2 μm.

[0012] Preferably, the wafer layer includes at least one of a lithium tantalate layer, a lithium niobate layer or a silicon layer.

[0013] Preferably, the metal layer includes: an aluminum layer and / or a gold layer.

[0014] Preferably, the metal support portion includes: a gold support portion and / or a tin support portion.

[0015] Preferably, the height of the metal support portion is 22 to 28 microns.

[0016] Preferably, the shape of the metal support portion includes: a spherical shape.

[0017] Preferably, a PAD metal layer is further provided on the piezoelectric crystal, and the PAD metal layer is provided on a side of the electrode away from the interdigital transducer; a lead is provided on the PAD metal layer, one end of the lead is fixedly connected to the PAD metal layer, and the other end extends outward.

[0018] Preferably, the thickness of the PAD metal layer is 2 to 3 microns.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] (1) The protective structure of the surface acoustic wave filter chip provided by the present invention is characterized in that a metal support portion is provided on the pole piece of the surface acoustic wave filter chip for connecting with the metal layer of the cover wafer. The formed cavity structure can prevent the interdigital transducers on the bare chip from being scratched by the mounting machine tool or tweezers when assembling the bare surface acoustic wave filter chip, and at the same time reduce the dust and other particles in the module from falling on the surface of the interdigital transducers to cause dirt and failure.

[0021] (2) The protective structure of the surface acoustic wave filter chip provided by the utility model has the advantages of simple structure and low cost, and has a good protective effect on the surface acoustic wave filter chip, preventing the interdigital transducer from being damaged during the assembly process, ensuring the stability of the chip, and the protective structure does not affect the assembly of the chip, forming a simple protection for the surface acoustic wave filter bare chip used for the sealing module. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 A schematic structural diagram of a protection structure for a surface acoustic wave filter chip provided by an embodiment of the present utility model;

[0024] Figure 2 This is a flow chart for preparing the protective structure of the surface acoustic wave filter chip provided in an embodiment of the present utility model.

[0025] Reference numerals:

[0026] 1- piezoelectric crystal;

[0027] 2-interdigital transducer;

[0028] 3-electrode;

[0029] 4-Metal support part;

[0030] 5-wafer layer;

[0031] 6-metal layer;

[0032] 7-PAD metal layer;

[0033] 8-Lead. DETAILED DESCRIPTION

[0034] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but those skilled in the art will understand that the embodiments described below are part of the embodiments of the present invention, rather than all of the embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0035] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating positions or relationships, are based on the positions or relationships shown in the accompanying drawings and are intended solely to facilitate the description of this utility model and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0036] In the description of this utility model, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0037] One aspect of the present invention relates to a surface acoustic wave filter chip having a protective structure, such as Figure 1 As shown, it includes a cover wafer and a surface acoustic wave filter chip;

[0038] The surface acoustic wave filter chip includes: a piezoelectric crystal 1 and an interdigital transducer 2 and an electrode 3 arranged on the piezoelectric crystal 1; the electrode 3 is arranged on both sides of the interdigital transducer 2; and a metal support portion 4 is provided on the electrode 3;

[0039] The cover wafer includes: a wafer layer 5 and a metal layer 6 ; the cover wafer is disposed above the IDT 2 and the electrode 3 , and the metal layer 6 of the cover wafer is connected to the electrode 3 through the metal support portion 4 .

[0040] The protective structure of the surface acoustic wave filter chip is provided with a metal support portion 4 on the pole piece of the surface acoustic wave filter chip for connecting with the metal layer 6 of the cover wafer. The formed cavity structure can prevent the interdigital transducer 2 on the bare chip from being scratched by the placement machine tool or tweezers when assembling the surface acoustic wave filter bare chip, and at the same time reduce the dust and other particles in the module from falling on the surface of the interdigital transducer 2 to cause dirt and failure.

[0041] The protective structure of the surface acoustic wave filter chip has the advantages of simple structure and low cost, has a good protective effect on the surface acoustic wave filter chip, can prevent the interdigital transducer 2 from being damaged during the assembly process, ensures and improves the stability of the chip, and the protective structure does not affect the assembly of the chip, forming a simple protection for the surface acoustic wave filter bare chip used for the sealing module.

[0042] The wafer layer 5 of this invention requires good bonding with materials such as gold and aluminum during sputtering or evaporation deposition. The metal layer 6 on the wafer layer 5 is formed by photolithography, with the width and position of the aluminum layer corresponding to the position of the electrodes 3 on the surface acoustic wave filter bare chip. This strong bonding ensures better shear strength and reliability after flip-chip mounting.

[0043] The width of the cover wafer must match the area of the IDT 2. The wafer is split according to the size of the IDT 2. The width referred to in this utility model refers to the shorter side in the top view of the SAW filter chip.

[0044] Furthermore, the thickness of the metal layer 6 is ≥2μm. A metal layer needs to be formed on the cover wafer. The metal layer is a square block that corresponds to the shape and size of the supporting metal block in the transducer area below (can be aluminum, gold, etc.) and has a thickness of at least 2 microns.

[0045] Furthermore, the wafer layer 5 includes at least one of a lithium tantalate layer, a lithium niobate layer, and a silicon layer. The above wafer layer 5 has the advantage of low cost.

[0046] Furthermore, the metal layer 6 includes: an aluminum layer and / or a gold layer.

[0047] The wafer layer 5 and the metal layer 6 made of a specific material have good bonding strength.

[0048] Furthermore, the metal support portion 4 includes: a gold support portion and / or a tin support portion. The metal support portion 4 can play a good supporting role and better connect the electrode 3 and the cover wafer without displacement or deformation at high temperature.

[0049] Furthermore, the height of the metal support portion 4 is 22 to 28 micrometers, which can ensure that the IDT 2 is in a safe space.

[0050] Furthermore, the shape of the metal support portion 4 includes: spherical.

[0051] Furthermore, a PAD metal layer 7 is provided on the piezoelectric crystal 1, disposed on a side away from the electrode 3 of the interdigital transducer 2. A lead 8 is provided on the PAD metal layer 7, one end of which is fixedly connected to the PAD metal layer 7 and the other end of which extends outward, to meet overall assembly requirements during use. Furthermore, the lead can be made of, but is not limited to, gold or silicon aluminum wire.

[0052] The PAD metal layer 7 is formed by photolithography and positioned around the edge of the piezoelectric crystal 1. The PAD metal layer 7 is thickened, leaving the cover wafer uncovered. It serves as a bonding point for the module's electrical connections. The PAD metal layer serves as a contact point for the chip's pins and is soldered to pads on the printed circuit board (PCB), establishing an electrical connection between the chip and external circuitry.

[0053] Furthermore, the thickness of the PAD metal layer 7 is 2 to 3 microns. The thickened PAD metal layer 7 facilitates user assembly. Normally, miniaturized RF modules are assembled using gold wire bonding. Based on reliability requirements, the thickness of the PAD metal layer 7 is 3 microns when it is an aluminum layer, and 2 microns when it is a gold layer.

[0054] Furthermore, the method for preparing the protective structure of the surface acoustic wave filter chip is as follows: Figure 2 As shown, the following steps are included:

[0055] (1) forming a metal layer 6 on the wafer layer 5 by a thermal evaporation process to obtain a cover wafer;

[0056] (2) Planting a metal support 4 on the metal layer 6 of the cover wafer. The diameter of the metal wire used is 25 μm. The height of the metal support 4 after ball planting is about 25 μm. The wafer after ball planting is split.

[0057] (3) After the wafer is split, it is flipped onto the surface acoustic wave filter bare chip wafer after the electrode 3 has been thickened. The flip-chip temperature is 200° C. and the power is adjusted to select the appropriate power for flip-chip.

[0058] The technical solution of the present invention will be further described and explained below in conjunction with specific embodiments.

[0059] Example 1

[0060] The protection structure of the surface acoustic wave filter chip provided in this embodiment includes a cover wafer and a surface acoustic wave filter chip;

[0061] The surface acoustic wave filter chip includes: a piezoelectric crystal 1 and an interdigital transducer 2 and an electrode 3 arranged on the piezoelectric crystal 1; the electrode 3 is arranged on both sides of the interdigital transducer 2; and a metal support portion 4 is arranged on the electrode 3;

[0062] The cover wafer includes: a wafer layer 5 and a metal layer 6 ; the cover wafer is arranged above the IDT 2 and the electrode 3 , and the metal layer 6 of the cover wafer is connected to the electrode 3 through the metal support portion 4 .

[0063] The thickness of the metal layer 6 is 2 μm;

[0064] Wafer layer 5 is: lithium tantalate layer;

[0065] The metal layer 6 is: an aluminum layer;

[0066] The metal support portion 4 is: a gold support portion;

[0067] The height of the metal support portion 4 is 25 microns;

[0068] The metal support portion 4 is spherical in shape;

[0069] A PAD metal layer 7 is also provided on the piezoelectric crystal 1, and the PAD metal layer 7 is provided on a side away from the electrode 3 of the interdigital transducer 2; a lead 8 is provided on the PAD metal layer 7, one end of the lead 8 is fixedly connected to the PAD metal layer 7, and the other end extends outward; the thickness of the PAD metal layer 7 is 3μm.

[0070] Example 2

[0071] The difference between this embodiment and embodiment 1 is that the thickness of the metal layer 6 is 5 μm; the wafer layer 5 is a silicon layer; the metal layer 6 is a gold layer; the metal support part 4 is a tin support part; the height of the metal support part 4 is 22 microns; and the thickness of the PAD metal layer 7 is 2 μm.

[0072] Example 3

[0073] The difference between this embodiment and embodiment 1 is that the thickness of the metal layer 6 is 7 μm; the wafer layer 5 is a lithium niobate layer; and the height of the metal support portion 4 is 28 μm.

[0074] The surface acoustic wave filter chip provided by the utility model does not affect the bonding of the bare chip after assembly, and at the same time plays a protective role, thereby improving the overall reliability of the module.

[0075] Although the present invention has been illustrated and described using specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features therein may be replaced by equivalents, without departing from the spirit and scope of the present invention. However, these modifications or replacements do not deviate from the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A surface acoustic wave filter chip with a protective structure, characterized in that: Including cover wafer and surface acoustic wave filter chip; The surface acoustic wave filter chip includes: a piezoelectric crystal and an interdigital transducer and an electrode arranged on the piezoelectric crystal; the electrodes are arranged on both sides of the interdigital transducer; and a metal support portion is arranged on the electrode; The cover wafer includes: a wafer layer and a metal layer; the cover wafer is arranged above the interdigital transducer and the electrode, and the metal layer of the cover wafer is connected to the electrode through the metal support portion.

2. The surface acoustic wave filter chip with a protection structure according to claim 1, wherein: The thickness of the metal layer is ≥2 μm.

3. The surface acoustic wave filter chip with a protection structure according to claim 1, wherein: The wafer layer includes at least one of a lithium tantalate layer, a lithium niobate layer or a silicon layer.

4. The surface acoustic wave filter chip with a protection structure according to claim 1, wherein: The metal layer includes: an aluminum layer and / or a gold layer.

5. The surface acoustic wave filter chip with a protection structure according to claim 1, wherein: The metal support portion includes: a gold support portion and / or a tin support portion; And / or, the height of the metal support portion is 22-28 microns.

6. The surface acoustic wave filter chip with a protection structure according to claim 1, wherein: The shape of the metal support portion includes: a spherical shape.

7. The surface acoustic wave filter chip with a protection structure according to any one of claims 1 to 6, characterized in that: A PAD metal layer is also provided on the piezoelectric crystal, and the PAD metal layer is provided on a side of the electrode away from the interdigital transducer; a lead is provided on the PAD metal layer, one end of the lead is fixedly connected to the PAD metal layer, and the other end extends outward.

8. The surface acoustic wave filter chip with a protection structure according to claim 7, wherein: The thickness of the PAD metal layer is 2-3 microns.

Images