High-power surface acoustic wave filter and forming method thereof

Abstract

The invention discloses a high-power surface acoustic wave filter and a forming method thereof, the filter comprises a substrate and a filter chip, the filter chip comprises a piezoelectric layer and a resonator, the lower surface of the piezoelectric layer is sequentially provided with a heat conduction layer and a heat conduction protection layer, and a heat conduction structure is arranged between the piezoelectric layer and the substrate. The forming method comprises the following steps: S1, providing a substrate; s2, forming a resonator, an interdigital input bonding pad and an interdigital output bonding pad on the upper surface of the piezoelectric layer; s3, the upper surface of the piezoelectric layer is coated with a heat conduction layer; s4, forming a heat conduction protection layer on the upper surface of the heat conduction layer; s5, a signal process hole and a heat dissipation process hole are formed through a drilling process; s6, performing photoetching to form a solder ball mounting hole; s7, inversely arranging the resonator on the substrate, and inserting the metal heat conduction column into the heat dissipation process hole; s8, heating and welding; and S9, coating an epoxy film layer. According to the filter formed by the forming method, the heat dissipation effect can be improved under the condition that the area is not increased, and the power capacity is further improved.

Description

Technical Field

[0001] The invention relates to the technical field of surface acoustic wave filters, and in particular to a high-power surface acoustic wave filter and a molding method thereof. Background Art

[0002] Due to the characteristics of simple structure, few mask layers, easy miniaturization and low cost, surface acoustic wave filters are widely used in home televisions, mobile communications, radio frequency filters and radars. As electronic packaging technology gradually develops towards miniaturization, high density, multi-function and high reliability, the power density of electronic systems increases, and the heat dissipation problem becomes more and more serious. For electronic devices, the effective life of the device is reduced by 30% to 50% for every 10°C increase in temperature. Therefore, increasing the power of the device has become a key issue in the development of electronic devices. The common method to increase the power of the filter is to cascade the resonator, expand the area and reduce the power flow density. However, due to the trend of miniaturization and the size of the filter, this method can only increase a small amount of power. Summary of the invention

[0003] The first technical problem to be solved by the present invention is to provide a high-power surface acoustic wave filter, which can improve the heat dissipation effect without increasing the area, thereby improving the power capacity.

[0004] The second technical problem to be solved by the present invention is to provide a molding method for a high-power surface acoustic wave filter, wherein the filter molded by the molding method can improve the heat dissipation effect without increasing the area, thereby improving the power capacity.

[0005] To solve the above-mentioned first technical problem, the technical solution of the present invention is: a high-power surface acoustic wave filter, comprising a substrate, wherein the upper surface of the substrate is provided with a substrate input upper layer pad and a substrate output upper layer pad, and the lower surface of the substrate is provided with a substrate input lower layer pad and a substrate output lower layer pad, and the substrate is embedded with an input connection metal connecting the substrate input upper layer pad and the substrate input upper layer pad, and an output connection metal connecting the substrate output upper layer pad and the substrate output lower layer pad, and a filter chip is arranged above the substrate, and the filter chip comprises a piezoelectric layer, and the lower surface of the piezoelectric layer is provided with a resonator, a forked input pad and a forked output pad, and the forked input pad is welded with the substrate input upper layer pad, and the forked output pad is welded with the substrate output upper layer pad by solder balls, and the lower surface of the piezoelectric layer is also covered with a heat conductive layer, and the heat conductive layer covers the resonator, the forked input pad and the forked output pad, and the heat conductive layer is provided with a heat conductive protective layer, and a heat conductive structure is also arranged between the piezoelectric layer and the substrate.

[0006] As a preferred solution, the heat-conducting structure includes a plurality of metal heat-conducting columns arranged between the piezoelectric layer and the upper surface of the substrate, the metal heat-conducting columns are arranged in the gaps between the metal strips of the resonator, and the metal heat-conducting columns penetrate the heat-conducting layer and the heat-conducting protective layer.

[0007] As a preferred solution, a heat-conducting metal layer is further provided on the upper surface of the substrate, and the heat-conducting metal layer connects the metal heat-conducting columns.

[0008] As a preferred solution, the heat-conducting metal layer is a curved heat-conducting metal layer.

[0009] As a preferred solution, a heat-conducting plate is embedded in the substrate, and the heat-conducting plate is connected to the heat-conducting metal layer via a heat-conducting connecting strip.

[0010] As a preferred solution, the heat-conducting layer is a polyimide heat-conducting layer or a polyamide heat-conducting layer, and the heat-conducting protective layer is a silicon nitride or silicon dioxide layer.

[0011] As a preferred solution, the thickness of the heat conductive layer is 100-200 nm, and the thickness of the heat conductive protection layer is 200-300 nm.

[0012] After adopting the above technical solution, the effect of the present invention is as follows: since the lower surface of the piezoelectric layer is also covered with a heat-conducting layer, the heat-conducting layer covers the resonator, the interdigital input pad and the interdigital output pad, the lower surface of the heat-conducting layer is provided with a heat-conducting protective layer, and a heat-conducting structure is also provided between the piezoelectric layer and the substrate. The heat-conducting layer can absorb the heat generated by the resonator and then transfer it to the heat-conducting protective layer. At the same time, the heat is also transferred between the piezoelectric layer and the substrate through the heat-conducting structure, so that as much heat as possible is transferred out, so that the power capacity of the filter can be improved.

[0013] Furthermore, since the heat-conducting structure includes a plurality of metal heat-conducting columns arranged between the piezoelectric layer and the upper surface of the substrate, the metal heat-conducting columns are arranged in the gaps between the metal strips of the resonator, and the metal heat-conducting columns penetrate the heat-conducting layer and the heat-conducting protective layer, heat can be better conducted through the metal heat-conducting columns. At the same time, the metal heat-conducting columns are arranged in the gaps and hinder the operation of the resonator.

[0014] Furthermore, since a heat-conducting metal layer is further provided on the upper surface of the substrate, the heat-conducting metal layer connects the metal heat-conducting columns, and the heat-conducting metal layer is a curved heat-conducting metal layer, the heat-conducting metal layer can further expand the heat dissipation area and improve the heat dissipation effect.

[0015] Since a heat-conducting plate is embedded inside the substrate, and the heat-conducting plate is connected to the heat-conducting metal layer via a heat-conducting connecting strip, heat can be further dissipated to the outside through the substrate, thereby greatly improving the power capacity.

[0016] In order to solve the above second technical problem, the technical solution of the present invention is: a molding method of a high-power surface acoustic wave filter, the molding method is used to mold the above high-power surface acoustic wave filter, comprising the following steps:

[0017] S1. Provide a substrate, on which a substrate input upper pad, a substrate output upper pad, a substrate input lower pad, a substrate output lower pad, an input connection metal and an output connection metal are pre-formed, and a metal heat-conducting column is formed in the middle of the substrate;

[0018] S2, forming a resonator, an interdigital input pad, and an interdigital output pad on the upper surface of the piezoelectric layer by a photolithography process;

[0019] S3, applying a thermal conductive layer on the upper surface of the piezoelectric layer by a glue machine, wherein the thermal conductive layer covers the resonator, the interdigital input pads and the interdigital output pads;

[0020] S4, forming a thermally conductive protective layer on the upper surface of the thermally conductive layer by physical vapor deposition; the thermally conductive protective layer covers the thermally conductive layer;

[0021] S5, drilling a signal process hole corresponding to the position of the interdigital input pad and the interdigital output pad, and a heat dissipation process hole adapted to the position of the metal heat conductive column on the upper surface of the thermal conductive protection layer through a drilling process;

[0022] S6, etching the thermal conductive layer in the signal process hole by a photolithography process until the interdigital input pad and the interdigital output pad are exposed, thereby forming a solder ball mounting hole; at the same time, etching the thermal conductive layer in the heat dissipation process hole until the piezoelectric layer is exposed;

[0023] S7, placing the solder ball into the solder ball installation hole and placing the resonator upside down on the substrate, inserting the metal heat-conducting column into the heat dissipation process hole, and placing the solder ball between the interdigital input pad and the substrate input upper pad, and between the interdigital output pad and the substrate output upper pad;

[0024] S8, heating to melt the solder balls for welding;

[0025] S9. Cover the outer surface of the resonator chip above the substrate with an epoxy film layer.

[0026] Preferably, in step S1, a thermally conductive metal layer connecting the metal thermally conductive columns is formed on the upper surface of the substrate.

[0027] Preferably, in step S1, a heat-conducting plate and a heat-conducting connecting strip are pre-formed inside the substrate, and the heat-conducting plate is connected to the metal heat-conducting column via the heat-conducting connecting strip.

[0028] After adopting the above technical solution, the effect of the present invention is: the molding method can mold the above filter, improve the heat dissipation effect, and greatly improve the power capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0030] Figure 1 is a structural cross-sectional view of an embodiment of the present invention;

[0031] Figure 2 yes Figure 1 Sectional view at AA;

[0032] In the attached figure: 1. substrate; 2. piezoelectric layer; 3. epoxy film layer; 4. resonator; 5. thermal conductive layer; 6. thermal conductive protective layer; 7. substrate input lower pad; 8. input connection metal; 9. substrate input upper pad; 10. solder ball; 11. forked input pad; 12. forked output pad; 13. substrate output upper pad; 14. output connection metal; 15. substrate output lower pad; 16. thermal conductive column; 17. thermal conductive metal layer; 18. thermal conductive connecting strip; 19. thermal conductive pad. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below through specific examples.

[0034] like Figure 1 and Figure 2 As shown, a high-power surface acoustic wave filter includes a substrate 1, wherein the upper surface of the substrate 1 is provided with a substrate input upper layer pad 9 and a substrate output upper layer pad 13, and the lower surface of the substrate 1 is provided with a substrate input lower layer pad 7 and a substrate output lower layer pad 15, wherein the substrate 1 is embedded with an input connection metal 8 connecting the substrate input upper layer pad 9 and the substrate input upper layer pad 9, and an output connection metal 14 connecting the substrate output upper layer pad 13 and the substrate output lower layer pad 15, and a filter chip is provided above the substrate 1, wherein the filter chip includes a piezoelectric Layer 2, the lower surface of the piezoelectric layer 2 is provided with a resonator 4, a forked input pad 11 and a forked output pad 12, the forked input pad 11 and the substrate input upper pad 9, the forked output pad 12 and the substrate output upper pad 13 are welded through solder balls 10, the lower surface of the piezoelectric layer 2 is also covered with a thermal conductive layer 5, the thermal conductive layer 5 covers the resonator 4, the forked input pad 11 and the forked output pad 12, the lower surface of the thermal conductive layer 5 is provided with a thermal conductive protective layer 6, and a thermal conductive structure is also provided between the piezoelectric layer 2 and the substrate 1.

[0035] like Figure 1As shown, the heat-conducting structure includes a plurality of metal heat-conducting columns 16 arranged between the piezoelectric layer 2 and the upper surface of the substrate 1 , wherein the metal heat-conducting columns 16 are arranged in the gaps between the metal strips of the resonator 4 , and the metal heat-conducting columns 16 penetrate the heat-conducting layer 5 and the heat-conducting protective layer 6 .

[0036] In this embodiment, Figure 1 and 2 As shown, a heat-conducting metal layer 17 is also provided on the upper surface of the substrate 1, and the heat-conducting metal layer 17 connects the metal heat-conducting pillars 16. The heat-conducting metal layer 17 is a curved heat-conducting metal layer 17. A heat-conducting plate 19 is also embedded in the interior of the substrate 1, and the heat-conducting plate 19 is connected to the heat-conducting metal layer 17 through a heat-conducting connecting strip 18.

[0037] The resonator 4 mainly includes a reflective grating and an interdigital transducer. In this embodiment, the heat-conducting layer 5 is a polyimide heat-conducting layer 5 or a polyamide heat-conducting layer 5, and the heat-conducting protective layer 6 is a silicon nitride or silicon dioxide layer, which not only plays a certain role in absorbing heat, but also can protect the structure of the resonator 4, avoid being corroded by water vapor, and improve the quality of the filter. The metal heat-conducting column 16 is preferably copper or aluminum. Of course, the heat-conducting plate 19 and the heat-conducting connecting strip 18 are preferably copper or aluminum cut to the same material as the metal heat-conducting column 16. The thickness of the heat-conducting layer 5 is 100-200nm, preferably 150nm, and the thickness of the heat-conducting protective layer 6 is 200-300nm, preferably 250nm.

[0038] This embodiment also discloses a molding method for a high-power surface acoustic wave filter. The molding method is used to mold the above-mentioned high-power surface acoustic wave filter, and comprises the following steps:

[0039] S1. Provide a substrate 1, on which substrate input upper pad 9, substrate output upper pad 13, substrate input lower pad 7, substrate output lower pad 15, input connection metal 8 and output connection metal 14 are preformed, and metal heat-conducting column 16 is formed in the middle of substrate 1; heat-conducting metal layer 17 connecting metal heat-conducting column 16 is formed on the upper surface of substrate 1. Heat-conducting pad 19 and heat-conducting connecting strip 18 are also preformed inside substrate 1, and heat-conducting pad 19 is connected to metal heat-conducting column 16 through heat-conducting connecting strip 18.

[0040] S2, forming a resonator 4, an interdigital input pad 11 and an interdigital output pad 12 on the upper surface of the piezoelectric layer 2 by a photolithography process;

[0041] S3, applying a thermal conductive layer 5 on the upper surface of the piezoelectric layer 2 by a glue sprayer, wherein the thermal conductive layer 5 covers the resonator 4, the interdigital input pad 11 and the interdigital output pad 12;

[0042] S4. Form a thermally conductive protective layer 6 on the upper surface of the thermally conductive layer 5 by physical vapor deposition; the thermally conductive protective layer 6 covers the thermally conductive layer 5; physical vapor deposition (Physical Vapor Deposition) is a technology that uses physical methods under vacuum conditions to vaporize the surface of a material source (solid or liquid) into gaseous atoms or molecules, or partially ionize them into ions, and deposits a thin film with certain special functions on the surface of a substrate through a low-pressure gas (or plasma) process. Physical vapor deposition is one of the main surface treatment technologies.

[0043] S5. Signal process holes corresponding to the positions of the forked input pads 11 and the forked output pads 12 and heat dissipation process holes adapted to the positions of the metal thermal conductive columns 16 are drilled on the upper surface of the thermal conductive protection layer 6 by a drilling process; the drilling can be done by laser drilling or mechanical drilling.

[0044] S6, etching the heat-conducting layer 5 in the signal process hole by photolithography until the interdigital input pad 11 and the interdigital output pad 12 are exposed, thereby forming a mounting hole for the solder ball 10; at the same time, etching the heat-conducting layer 5 in the heat dissipation process hole until the piezoelectric layer 2 is exposed;

[0045] S7, place the solder ball 10 into the solder ball 10 installation hole and invert the resonator on the substrate 1, insert the metal heat-conducting column 16 into the heat dissipation process hole, and place the solder ball 10 between the interdigital input pad 11 and the substrate input upper pad 9, and between the interdigital output pad 12 and the substrate output upper pad 13;

[0046] S8, heating to melt the solder ball 10 for soldering;

[0047] S9, covering the outer surface of the resonator 4 chip above the substrate 1 with an epoxy film layer 3.

[0048] In the filter of this embodiment, the signal is input from the substrate input lower pad 7, passes through the input connection metal 8, the substrate input upper pad 9, the solder ball 10, and the forked input pad 11 to enter the resonator 4, and then outputs from the forked output pad 12, the solder ball 10, the substrate output upper pad 13, the output connection metal 14, and the substrate output lower pad 15 from the other end. Conventional filters generate heat after signal input, part of which remains in the resonator 4, and the other part is transferred out through the substrate 1, while the heat of the present invention is also dissipated through the heat conductive layer 5, the heat conductive protective layer 6, the metal heat conductive column 16, the heat conductive connecting strip 18, and the heat conductive pad 19, so as to transfer as much heat as possible and quickly, thereby improving the power capacity of the filter.

[0049] The above-described embodiments are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Various modifications and alterations to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A high-power surface acoustic wave filter, comprising a substrate, wherein the upper surface of the substrate is provided with a substrate input upper layer pad and a substrate output upper layer pad, the lower surface of the substrate is provided with a substrate input lower layer pad and a substrate output lower layer pad, the substrate is embedded with input connection metals connecting the substrate input upper layer pad and the substrate input upper layer pad, and output connection metals connecting the substrate output upper layer pad and the substrate output lower layer pad, a filter chip is arranged above the substrate, the filter chip comprises a piezoelectric layer, a resonator, a forked input pad and a forked output pad are arranged on the lower surface of the piezoelectric layer, the forked input pad and the substrate input upper layer pad, and the forked output pad and the substrate output upper layer pad are welded by solder balls, characterized in that: the lower surface of the piezoelectric layer is also covered with a heat conductive layer, the heat conductive layer covers the resonator, the forked input pad and the forked output pad, the lower surface of the heat conductive layer is provided with a heat conductive protective layer, and a heat conductive structure is also arranged between the piezoelectric layer and the substrate.

2. A high power surface acoustic wave filter as claimed in claim 1, characterized in that: The heat-conducting structure comprises a plurality of metal heat-conducting columns arranged between the piezoelectric layer and the upper surface of the substrate. The metal heat-conducting columns are arranged in the gaps between the metal strips of the resonator, and the metal heat-conducting columns penetrate the heat-conducting layer and the heat-conducting protective layer.

3. A high power surface acoustic wave filter as claimed in claim 2, characterized in that: A heat-conducting metal layer is also disposed on the upper surface of the substrate, and the heat-conducting metal layer connects the metal heat-conducting columns.

4. A high power surface acoustic wave filter as claimed in claim 3, characterized in that: The heat-conducting metal layer is a curved heat-conducting metal layer.

5. A high power surface acoustic wave filter as claimed in claim 4, characterized in that: A heat-conducting plate is also embedded in the substrate, and the heat-conducting plate is connected to the heat-conducting metal layer via a heat-conducting connecting strip.

6. A high power surface acoustic wave filter as claimed in claim 5, characterized in that: The heat-conducting layer is a polyimide heat-conducting layer or a polyamide heat-conducting layer, and the heat-conducting protective layer is a silicon nitride or silicon dioxide layer.

7. A high power surface acoustic wave filter as claimed in claim 6, characterized in that: The thickness of the heat-conducting layer is 100-200nm, and that of the heat-conducting protective layer is 200-300nm.

8. A method for forming a high-power surface acoustic wave filter, characterized in that: The molding method is used to mold the high-power surface acoustic wave filter as claimed in claim 1, comprising the following steps: S1. Provide a substrate, on which a substrate input upper pad, a substrate output upper pad, a substrate input lower pad, a substrate output lower pad, an input connection metal and an output connection metal are pre-formed, and a metal heat-conducting column is formed in the middle of the substrate; S2, forming a resonator, an interdigital input pad, and an interdigital output pad on the upper surface of the piezoelectric layer by a photolithography process; S3, applying a thermal conductive layer on the upper surface of the piezoelectric layer by a glue machine, wherein the thermal conductive layer covers the resonator, the interdigital input pads and the interdigital output pads; S4, forming a thermally conductive protective layer on the upper surface of the thermally conductive layer by physical vapor deposition; the thermally conductive protective layer covers the thermally conductive layer; S5, drilling a signal process hole corresponding to the position of the interdigital input pad and the interdigital output pad, and a heat dissipation process hole adapted to the position of the metal heat conductive column on the upper surface of the thermal conductive protection layer through a drilling process; S6, etching the thermal conductive layer in the signal process hole by a photolithography process until the interdigital input pad and the interdigital output pad are exposed, thereby forming a solder ball mounting hole; at the same time, etching the thermal conductive layer in the heat dissipation process hole until the piezoelectric layer is exposed; S7, placing the solder ball into the solder ball installation hole and placing the resonator upside down on the substrate, inserting the metal heat-conducting column into the heat dissipation process hole, and placing the solder ball between the interdigital input pad and the substrate input upper pad, and between the interdigital output pad and the substrate output upper pad; S8, heating to melt the solder balls for welding; S9. Cover the outer surface of the resonator chip above the substrate with an epoxy film layer.

9. A method for forming a high-power surface acoustic wave filter as claimed in claim 8, characterized in that: In the step S1, a heat-conducting metal layer connecting the metal heat-conducting pillars is formed on the upper surface of the substrate.

10. A method for forming a high-power surface acoustic wave filter as claimed in claim 9, characterized in that: In the step S1, a heat-conducting plate and a heat-conducting connecting strip are pre-formed inside the substrate, and the heat-conducting plate is connected to the metal heat-conducting column through the heat-conducting connecting strip.

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