Bulk acoustic wave device packaging method and structure

Abstract

The invention relates to the technical field of bulk acoustic wave devices, and particularly provides a bulk acoustic wave device packaging method and structure, and the method comprises the steps: carrying out the flip-chip welding of a bulk acoustic wave device on a packaging substrate; filling an air gap between the bulk acoustic wave device and the packaging substrate with a liquid material of which the acoustic impedance is smaller than that of an electrode of the bulk acoustic wave device and the heat conductivity coefficient is greater than a first preset heat conductivity coefficient; solidifying the liquid material so as to form a reflection heat dissipation layer between the bulk acoustic wave device and the packaging substrate; packaging the bulk acoustic wave device and the reflection heat dissipation layer to enable the packaging layer to wrap the bulk acoustic wave device and the reflection heat dissipation layer so as to obtain a bulk acoustic wave device packaging structure; according to the method, the power capacity of the bulk acoustic wave device can be improved under the condition that the structure of the bulk acoustic wave device does not need to be optimized.

Description

Technical Field

[0001] This application relates to the field of bulk acoustic wave device technology, and more specifically, to a bulk acoustic wave device packaging method and structure. Background Technology

[0002] Driven by both the market and technology advancements of 5G / 6G evolution and the expansion of the Internet of Things (IoT), communication terminal equipment is placing more stringent demands on the power capacity of bulk acoustic wave (BAW) devices. Improving power capacity directly impacts the data transmission rate, connection stability, operational reliability, and service life of communication systems. Therefore, enhancing the power capacity of BAW devices and extending their application to higher-power scenarios such as base stations, automotive, and industrial applications is crucial. However, the current power tolerance of commercially available BAW devices remains insufficient, becoming a bottleneck restricting performance breakthroughs and making power capacity improvement a focal point of industry attention.

[0003] Existing technologies typically improve the power capacity of bulk acoustic wave (SAW) devices by addressing the device design level. For example, in SAW filters, optimizing the resonator area or breaking it down into multiple units enhances heat dissipation, thereby increasing its power handling capacity to some extent. However, such design-level adjustments often lead to a deterioration in other key performance parameters such as insertion loss, out-of-band rejection, or linearity. Maintaining a balance between the original design specifications and overall performance requires repeated and complex simulations and process adjustments, which significantly increases the R&D cycle and design complexity, as well as incurring considerable time and cost investment.

[0004] Therefore, exploring an efficient, feasible, and non-introducing method to increase power capacity while maintaining the existing performance of bulk acoustic wave devices has become a significant technical challenge.

[0005] There is currently no effective technical solution to the above problems. Summary of the Invention

[0006] The purpose of this application is to provide a packaging method and structure for a bulk acoustic wave device, which can improve the power capacity of the bulk acoustic wave device without optimizing the structure of the bulk acoustic wave device.

[0007] In a first aspect, this application provides a packaging method for a bulk acoustic wave device (BAW) to improve the power capacity of the BAW device, comprising: S1. Flip-chip solder the bulk acoustic wave device onto the packaging substrate; S2. A liquid material with an acoustic impedance lower than that of the electrodes of the bulk acoustic wave device and a thermal conductivity greater than a first preset thermal conductivity is used to fill the air gap between the bulk acoustic wave device and the packaging substrate. The first preset thermal conductivity is greater than the thermal conductivity of air. S3. Solidify the liquid material to form a reflective heat dissipation layer between the bulk acoustic wave device and the packaging substrate; S4. Encapsulate the bulk acoustic wave device and the reflective heat dissipation layer so that the encapsulation layer covers the bulk acoustic wave device and the reflective heat dissipation layer, thereby obtaining the bulk acoustic wave device encapsulation structure.

[0008] This application provides a bulk acoustic wave (SAW) device packaging method. This method involves filling the space between the SAW device and the packaging substrate with a liquid material whose acoustic impedance is lower than that of the SAW device and whose thermal conductivity is higher than a first preset thermal conductivity. The liquid material is then solidified to form a reflective heat dissipation layer, creating an additional and efficient heat dissipation channel between the SAW device and the packaging substrate. Since this method can utilize this heat dissipation channel to quickly dissipate the heat generated by the SAW device, it effectively improves the heat dissipation capacity of the SAW device. Therefore, this method effectively increases the power capacity of the SAW device. In other words, this method increases the power capacity of the SAW device without optimizing its structure, thus effectively solving the problems of performance degradation, increased R&D cycle and design difficulty, and high time and cost investment associated with improving the power capacity of SAW devices through device design.

[0009] Optionally, step S4 includes: S41. The bulk acoustic wave device and the reflective heat dissipation layer are encapsulated with a film material with a thermal conductivity greater than the second preset thermal conductivity to form a sealed protective film that encapsulates the bulk acoustic wave device and the reflective heat dissipation layer. The second preset thermal conductivity is greater than the thermal conductivity of air. S42. Encapsulate the sealing protective film to form an encapsulation layer that wraps around the sealing protective film.

[0010] Because this technical solution introduces a sealing protective film with good thermal conductivity as an intermediate protective layer, the sealing protective film can effectively protect the bulk acoustic wave device during the packaging process and form an additional heat dissipation channel on the outer surface of the bulk acoustic wave device. Therefore, this technical solution can effectively reduce the impact of packaging stress on the performance of the bulk acoustic wave device and effectively improve the heat dissipation capacity of the bulk acoustic wave device, thereby effectively improving the power capacity of the bulk acoustic wave device.

[0011] Optionally, the bulk acoustic wave device, the packaging substrate, the reflective heat dissipation layer, and the sealing protective film constitute an intermediate packaging structure, and step S42 includes: S421. The intermediate encapsulation structure is moved into an encapsulation mold filled with powdered or liquid epoxy resin molding compound. S422. Preheat the packaging mold; S423. Heat the epoxy resin molding compound to a preset temperature and compress the epoxy resin molding compound so that the epoxy resin molding compound wraps the sealing protective film. S424. Bake the packaging mold to cure the epoxy resin molding compound inside the packaging mold, thereby obtaining a packaging layer that wraps the sealing protective film.

[0012] Optionally, the thickness of the sealing protective film is less than the thickness of the encapsulation layer.

[0013] Optionally, step S1 includes: S11. Based on ultrasonic thermo-press flip-chip bonding technology, bulk acoustic wave devices are flip-chip bonded onto the packaging substrate.

[0014] Optionally, the ultrasonic power range of the ultrasonic thermo-press flip-chip welding technology is 0.5-50W, the ultrasonic time range is 50-1000ms, the temperature range is 100-300℃, and the pressure range is 5-100N.

[0015] Optionally, step S11 includes: S111: Multiple bulk acoustic wave devices are flip-chip bonded onto a packaging substrate based on ultrasonic thermo-press flip-chip bonding technology; The bulk acoustic wave device packaging method also includes steps performed after step S4: S5. The bulk acoustic wave device package structure is diced to obtain a single-unit package structure containing only one bulk acoustic wave device.

[0016] Optionally, step S5 includes: S51. Perform deflashing and surface treatment on the bulk acoustic wave device packaging structure; S52. The bulk acoustic wave device package structure that has undergone deflashing and surface treatment is diced to obtain a single-unit package structure containing only one bulk acoustic wave device.

[0017] This technical solution removes burrs or excess material from the edges of the bulk acoustic wave (SAW) device packaging structure by deflashing, preventing these defects from being pressed in or torn during the dicing process, thus affecting the flatness and integrity of the diced surface. Simultaneously, the solution ensures the surface of the SAW device packaging structure is clean and free of contaminants through surface treatment. This not only improves the cutting efficiency and lifespan of the dicing tool but also prevents contaminants from being introduced or adhering to the new cut surface during the dicing process, thereby guaranteeing the surface quality of the final single-unit packaging structure.

[0018] Optionally, the liquid material is a polyimide material.

[0019] Secondly, this application also provides a bulk acoustic wave device packaging structure for improving the power capacity of a bulk acoustic wave device, the bulk acoustic wave device packaging structure being made by the bulk acoustic wave device packaging method provided in the first aspect above.

[0020] This application provides a bulk acoustic wave (SAW) device packaging structure. By filling the space between the SAW device and the packaging substrate with a liquid material whose acoustic impedance is lower than that of the SAW device and whose thermal conductivity is greater than a first preset thermal conductivity, and then solidifying the liquid material to obtain a reflective heat dissipation layer, an additional and efficient heat dissipation channel is formed between the SAW device and the packaging substrate. Since this application can utilize this heat dissipation channel to quickly dissipate the heat generated by the SAW device, it can effectively improve the heat dissipation capacity of the SAW device. Therefore, this application can effectively improve the power capacity of the SAW device. In other words, this application is equivalent to improving the power capacity of the SAW device without optimizing its structure, thereby effectively solving the problems of performance degradation, increased R&D cycle and design difficulty, and large time and cost investment that arise from improving the power capacity of SAW devices from the device design level.

[0021] As can be seen from the above, the bulk acoustic wave (SAW) device packaging method and structure provided in this application form an additional and efficient heat dissipation channel between the SAW device and the packaging substrate by filling a liquid material with an acoustic impedance lower than that of the SAW device and a thermal conductivity greater than a first preset thermal conductivity between the SAW device and the packaging substrate, and then solidifying the liquid material to obtain a reflective heat dissipation layer. Since this application can utilize this heat dissipation channel to quickly dissipate the heat generated by the SAW device, it can effectively improve the heat dissipation capacity of the SAW device. Therefore, this application can effectively improve the power capacity of the SAW device. In other words, this application is equivalent to improving the power capacity of the SAW device without optimizing its structure. This effectively solves the problems of performance degradation, increased R&D cycle and design difficulty, and large time and cost investment caused by the need to improve the power capacity of the SAW device from the device design level. Attached Figure Description

[0022] Figure 1 This is a flowchart of a bulk acoustic wave device packaging method provided in an embodiment of this application.

[0023] Figure 2 This is a schematic diagram of a bulk acoustic wave device packaging structure provided in an embodiment of this application.

[0024] Reference numerals: 1. Bulk acoustic wave device; 2. Packaging substrate; 3. Reflective heat dissipation layer; 4. Packaging layer; 5. Sealing protective film; 6. Solder ball. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0026] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0027] Firstly, such as Figure 1 and Figure 2 As shown, this application provides a bulk acoustic wave device packaging method for improving the power capacity of a bulk acoustic wave device 1, which includes: S1. The bulk acoustic wave device 1 is flip-chip soldered onto the packaging substrate 2; S2. The air gap between the bulk acoustic wave device 1 and the packaging substrate 2 is filled with a liquid material whose acoustic impedance is less than that of the electrodes of the bulk acoustic wave device 1 and whose thermal conductivity is greater than that of the first preset thermal conductivity. S3. Solidify the liquid material to form a reflective heat dissipation layer 3 between the bulk acoustic wave device 1 and the packaging substrate 2; S4. Encapsulate the bulk acoustic wave device 1 and the reflective heat dissipation layer 3 so that the encapsulation layer 4 wraps the bulk acoustic wave device 1 and the reflective heat dissipation layer 3, thereby obtaining the bulk acoustic wave device encapsulation structure.

[0028] By introducing a reflective heat dissipation layer 3, this application not only effectively limits acoustic wave leakage, but also provides an additional heat dissipation channel and mechanical support for the bulk acoustic wave device 1, thereby significantly improving the power capacity, mechanical stability and reliability of the bulk acoustic wave device 1. This effectively solves the problem of insufficient power capacity and difficulty in improving other performance characteristics in the prior art.

[0029] The bulk acoustic wave (BAW) device 1 in this embodiment is an electronic device that operates by utilizing the propagation characteristics of sound waves in a solid medium. The BAW device 1 can be an existing BAW filter or BAW resonator. Preferably, the BAW device 1 includes a substrate, a bottom electrode, a piezoelectric layer, and a top electrode connected sequentially from bottom to top, with an acoustic reflector provided on the substrate. The packaging substrate 2 in this embodiment is a carrier for supporting and connecting the BAW device 1, and the packaging substrate 2 has good electrical and thermal properties. The reflective heat dissipation layer 3 in this embodiment is a special functional layer introduced in this application. Its main function is to act as a heat dissipation channel to conduct heat generated by the BAW device 1, while simultaneously reflecting sound waves to reduce sound wave leakage and providing stable mechanical support for the BAW device 1. The liquid material in this embodiment refers to a substance that is liquid at room temperature but can solidify under specific conditions to form the reflective heat dissipation layer 3. The packaging layer 4 in this embodiment is a protective structure used to protect the BAW device 1 and the reflective heat dissipation layer 3 from the influence of the external environment.

[0030] Step S1 involves flip-chip soldering the bulk acoustic wave device 1 onto the packaging substrate 2. Specifically, flip-chip soldering means first inverting the bulk acoustic wave device 1 (i.e., setting the top electrode of the bulk acoustic wave device 1 downwards), and then soldering the bulk acoustic wave device 1 onto the packaging substrate 2 by soldering the top electrode of the bulk acoustic wave device 1 onto the corresponding electrode of the packaging substrate 2. In this embodiment, a solder paste reflow soldering process can be used to solder the bulk acoustic wave device 1 onto the packaging substrate 2 (i.e., the top electrode of the bulk acoustic wave device 1 and the corresponding electrode on the packaging substrate 2 are connected by solder balls). In this embodiment, a thermoforming soldering technique can also be used to solder the bulk acoustic wave device 1 onto the packaging substrate 2 (i.e., using heating and pressure to connect the bulk acoustic wave device 1 and the packaging substrate 2).

[0031] Step S2 involves filling the air gap between the bulk acoustic wave device 1 and the encapsulation substrate 2 with a liquid material whose acoustic impedance is lower than that of the electrodes of the bulk acoustic wave device 1 and whose thermal conductivity is greater than a first preset thermal conductivity. The selection of the liquid material is crucial. This liquid material has an acoustic impedance lower than that of the electrodes (including the bottom and top electrodes) of the bulk acoustic wave device 1 and a thermal conductivity greater than the first preset thermal conductivity. In other words, this embodiment is equivalent to selecting a material with low acoustic impedance and high thermal conductivity as the material for filling the air gap between the bulk acoustic wave device 1 and the encapsulation substrate 2. The liquid material in this embodiment can be silicone oil, epoxy resin, or a polyimide precursor solution, etc. Since the acoustic impedance of the liquid material is less than that of the electrodes of the bulk acoustic wave device 1, i.e., there is an acoustic impedance difference between the liquid material and the top electrode, and this acoustic impedance difference can reflect sound waves, this embodiment can effectively reflect sound waves using the layer structure obtained by solidifying the liquid material, thereby effectively reducing sound wave leakage and thus effectively improving the performance and quality factor of the bulk acoustic wave device 1. Furthermore, since the thermal conductivity of the liquid material is greater than the first preset thermal conductivity, this embodiment can effectively conduct the heat generated by the bulk acoustic wave device 1 using the layer structure (reflective heat dissipation layer 3) obtained by solidifying the liquid material. In other words, this embodiment is equivalent to... A heat dissipation path is formed between the bulk acoustic wave device 1, the reflective heat dissipation layer 3, and the packaging substrate 2. Therefore, this embodiment is equivalent to providing an additional heat dissipation channel for the bulk acoustic wave device 1 by filling the air gap between the bulk acoustic wave device 1 and the packaging substrate 2 with liquid material and then solidifying the liquid material. This effectively improves the heat dissipation capacity of the bulk acoustic wave device 1. Since the heat dissipation capacity of the bulk acoustic wave device 1 is positively correlated with the maximum input power it can withstand, this embodiment enables the bulk acoustic wave device 1 to withstand a larger input power, thereby effectively improving the power capacity of the bulk acoustic wave device 1.

[0032] Step S3 involves solidifying a liquid material to form a reflective heat dissipation layer 3 between the bulk acoustic wave device 1 and the packaging substrate 2. Preferably, step S3 employs a vacuum baking process to solidify the liquid material. The solidified reflective heat dissipation layer 3 possesses stable physical and chemical properties, meaning that the reflective heat dissipation layer 3 in this embodiment can effectively and sustainably perform its functions of reflecting sound waves and dissipating heat. It should be understood that since the reflective heat dissipation layer 3 in this embodiment is obtained by solidifying a liquid material filled between the bulk acoustic wave device 1 and the packaging substrate 2, with both ends of the reflective heat dissipation layer 3 connected to the bulk acoustic wave device 1 and the packaging substrate 2 respectively, the reflective heat dissipation layer 3 also provides stable mechanical support for the bulk acoustic wave device 1, thereby effectively improving the mechanical stability and reliability of the final bulk acoustic wave device packaging structure.

[0033] Step S4 can employ existing molding processes to encapsulate the bulk acoustic wave device 1 and the reflective heat dissipation layer 3, so that the encapsulation layer 4 encapsulates the bulk acoustic wave device 1 and the reflective heat dissipation layer 3, thereby obtaining a bulk acoustic wave device encapsulation structure. After the encapsulation layer 4 is formed, it will enclose the encapsulation substrate 2 to form a sealed space. In this embodiment, both the bulk acoustic wave device 1 and the reflective heat dissipation layer 3 are located within this sealed space. Therefore, the encapsulation layer 4 in this embodiment can protect the bulk acoustic wave device 1 and the reflective heat dissipation layer 3, thereby effectively extending the service life of the bulk acoustic wave device 1 and the reflective heat dissipation layer 3.

[0034] The bulk acoustic wave (SAW) device packaging method of this application effectively solves the problem of insufficient power capacity of existing SAW devices by introducing a reflective heat dissipation layer 3. First, the SAW device 1 is flip-chip soldered onto the packaging substrate 2 to ensure a stable electrical and mechanical connection between the SAW device 1 and the packaging substrate 2. Then, a liquid material with specific acoustic impedance and thermal conductivity is used to fill the air gap between the SAW device 1 and the packaging substrate 2. After solidification, this liquid material forms the reflective heat dissipation layer 3, which acts as an additional heat dissipation channel, efficiently conducting the heat generated by the SAW device 1 during operation to the packaging substrate 2 and dissipating it. This allows the SAW device 1 to withstand higher input power, thereby effectively increasing its power capacity. The reflective heat dissipation layer 3 also effectively reflects the sound waves generated inside the SAW device 1, confining them within the device and reducing sound wave leakage to the external environment. This is crucial for maintaining the Q value (quality factor) and performance of the SAW device 1. Finally, by encapsulating the bulk acoustic wave device 1 and the reflective heat dissipation layer 3, a sealed encapsulation structure is formed to protect the bulk acoustic wave device 1 and the reflective heat dissipation layer 3, thereby ensuring the long-term stable operation of the bulk acoustic wave device 1 and the reflective heat dissipation layer 3. The entire process is interconnected, with various technical features working together to achieve a comprehensive improvement in the power capacity, mechanical stability, and reliability of the bulk acoustic wave device 1.

[0035] Therefore, the bulk acoustic wave device packaging method provided in this application forms an additional and efficient heat dissipation channel between the bulk acoustic wave device 1 and the packaging substrate 2 by filling the space between the bulk acoustic wave device 1 and the packaging substrate 2 with a liquid material whose acoustic impedance is less than that of the bulk acoustic wave device 1 and whose thermal conductivity is greater than a first preset thermal conductivity, and then solidifying the liquid material to obtain a reflective heat dissipation layer 3. Since this application can use this heat dissipation channel to quickly dissipate the heat generated by the bulk acoustic wave device 1, this application can effectively improve the heat dissipation capacity of the bulk acoustic wave device 1. Therefore, this application can effectively improve the power capacity of the bulk acoustic wave device 1. That is, this application is equivalent to improving the power capacity of the bulk acoustic wave device 1 without optimizing the structure of the bulk acoustic wave device 1, thereby effectively solving the problems of performance degradation, increased R&D cycle and design difficulty, and large time and cost investment caused by the need to start from the device design level to improve the power capacity of the bulk acoustic wave device 1.

[0036] In some preferred embodiments, step S4 includes: S41. The bulk acoustic wave device 1 and the reflective heat dissipation layer 3 are encapsulated using a film material with a thermal conductivity greater than the second preset thermal conductivity to form a sealing protective film 5 that encapsulates the bulk acoustic wave device 1 and the reflective heat dissipation layer 3. The second preset thermal conductivity is greater than the thermal conductivity of air. S42. The sealing protective film 5 is encapsulated to form an encapsulation layer 4 that wraps the sealing protective film 5.

[0037] Since step S41 selects a film material (preferably an epoxy resin film) with a thermal conductivity greater than the second preset thermal conductivity (preferably greater than or equal to the first preset thermal conductivity), step S42 can effectively conduct heat generated by the bulk acoustic wave device 1 while providing physical protection for the bulk acoustic wave device 1 and the reflective heat dissipation layer 3. After the film is coated and encapsulated, the film material forms a sealing protective film 5. The sealing protective film 5 is an intermediate layer between the bulk acoustic wave device 1, the reflective heat dissipation layer 3, and the subsequent encapsulation layer 4. The sealing protective film 5 can prevent the bulk acoustic wave device 1 from being contaminated or malfunctioning due to contaminants or moisture intruding into it during subsequent processes or use. In this embodiment, the thickness of the sealing protective film 5 is preferably 0.5-20 μm to avoid insufficient mechanical strength due to an excessively thin sealing protective film 5, and decreased heat conduction efficiency, increased bulk acoustic wave device encapsulation structure size, or affected acoustic wave transmission characteristics of the bulk acoustic wave device 1 due to an excessively thick sealing protective film 5. Step S42 encapsulates the formed sealing protective film 5 to obtain the final encapsulation layer 4. The encapsulation layer 4 mainly provides protection from the external environment and mechanical support. Since the bulk acoustic wave device 1 and the reflective heat dissipation layer 3 have been effectively isolated by the sealing protective film 5, there is greater flexibility in selecting the material of the encapsulation layer 4. That is, this embodiment can use materials with lower cost or easier processing as the material of the encapsulation layer 4 without having to consider its direct compatibility with the bulk acoustic wave device 1. The thermal conductivity of the encapsulation layer 4 material in this embodiment is preferably greater than or equal to the second preset thermal conductivity. It should be understood that since the thermal conductivity of the sealing protective film 5 in this embodiment is greater than the second preset thermal conductivity, and the thermal conductivity of the encapsulation layer 4 in this embodiment is greater than or equal to the second preset thermal conductivity, this embodiment is equivalent to forming an additional heat dissipation channel on the outer surface of the bulk acoustic wave device 1, thereby further improving the heat dissipation capacity of the bulk acoustic wave device 1, and thus effectively improving the power capacity of the bulk acoustic wave device 1.

[0038] This embodiment decomposes the encapsulation process into two stages by introducing an intermediate sealing protective film 5. First, a film material with specific thermal conductivity is used to coat the bulk acoustic wave device 1 and the reflective heat dissipation layer 3 to form a tightly fitting sealing protective film 5. This film provides direct physical and chemical protection for the sensitive bulk acoustic wave device 1, effectively preventing stress, corrosion, or contamination that may occur during subsequent encapsulation. Furthermore, because the thermal conductivity of the film material is greater than a second preset thermal conductivity, the sealing protective film 5 effectively transfers the heat generated by the bulk acoustic wave device 1 during operation. Then, the final encapsulation layer 4 is formed by externally encapsulating the sealing protective film 5. This layered encapsulation method provides more refined protection for the bulk acoustic wave device 1 throughout the entire encapsulation process and optimizes the thermal management path. Therefore, since this embodiment introduces a sealing protective film 5 with good thermal conductivity as an intermediate protective layer, the sealing protective film 5 can effectively protect the bulk acoustic wave device 1 during the packaging process and form an additional heat dissipation channel on the outer surface of the bulk acoustic wave device 1. Thus, this embodiment can effectively reduce the impact of packaging stress on the performance of the bulk acoustic wave device 1 and effectively improve the heat dissipation capacity of the bulk acoustic wave device 1, thereby effectively improving the power capacity of the bulk acoustic wave device 1.

[0039] In some preferred embodiments, the bulk acoustic wave device 1, the packaging substrate 2, the reflective heat dissipation layer 3, and the sealing protective film 5 constitute an intermediate packaging structure, and step S42 includes: S421. The intermediate encapsulation structure is moved into an encapsulation mold filled with powdered or liquid epoxy resin molding compound. S422. Preheat the packaging mold; S423. Heat the epoxy resin molding compound to a preset temperature and compress the epoxy resin molding compound so that the epoxy resin molding compound wraps the sealing protective film 5. S424. The packaging mold is baked to cure the epoxy resin molding compound inside the packaging mold, thereby obtaining the packaging layer 4 that wraps the sealing protective film 5.

[0040] In step S421, the intermediate encapsulation structure is precisely placed in the encapsulation mold, which is pre-filled with epoxy resin molding compound. The epoxy resin molding compound can be in powder or liquid form, depending on the specific encapsulation equipment and process requirements. In this embodiment, the purpose of choosing powder or liquid epoxy resin molding compound is to ensure that the molding compound can fully fill the mold space and make close contact with the sealing protective film 5, thus laying the foundation for the formation of a uniform encapsulation layer 4. In step S422, the encapsulation mold is preheated. This embodiment can improve the fluidity of the epoxy resin molding compound by preheating the encapsulation mold, so that it can better fill all corners of the mold during the subsequent compression process and promote good wetting and adhesion with the sealing protective film 5. It also helps to reduce internal stress during the curing process. In step S423, the epoxy resin molding compound is heated to a preset temperature and compressed at that temperature. Heating the epoxy resin molding compound to the preset temperature in this embodiment aims to achieve optimal flow and reactivity. The compression process in this embodiment refers to allowing the liquid or molten epoxy resin molding compound to flow within the mold under pressure, tightly wrapping the sealing protective film 5, thereby eliminating any possible voids and ensuring the uniformity and density of the encapsulation layer 4. In step S424, the encapsulation mold is baked. This embodiment provides a continuous high-temperature environment by baking the encapsulation mold to promote the cross-linking and curing reaction of the epoxy resin molding compound, thereby forming a robust and stable encapsulation layer 4. This embodiment ensures that the encapsulation layer 4 possesses the required mechanical strength, heat resistance, and chemical stability by precisely controlling the baking temperature and time. It should be understood that this embodiment is equivalent to forming the encapsulation layer 4 outside the sealing protective film 5 using existing molding processes; its working principle will not be discussed in detail here.

[0041] This embodiment effectively solves problems such as voids, weak bonding, or uneven encapsulation that may exist in traditional encapsulation by introducing a refined process of mold encapsulation, preheating, thermal compression, and baking curing. Specifically, the sealing protective film 5 is placed in an encapsulation mold filled with epoxy resin molding compound, providing a structural basis for subsequent precise encapsulation. The preheating step optimizes the flowability of the epoxy resin molding compound, allowing it to penetrate and wet the surface of the sealing protective film 5 more fully under pressure. Subsequently, heating to a preset temperature and compression treatment forces the epoxy resin molding compound to be uniformly filled into all surfaces and gaps of the sealing protective film 5 while in a flowing state, thereby maximizing the elimination of air and ensuring the density and void-free nature of the encapsulation layer 4. The final baking curing step ensures that the epoxy resin molding compound is completely cross-linked, forming a strong, uniform encapsulation layer 4 that is tightly bonded to the sealing protective film 5. Therefore, this embodiment can effectively improve the bonding strength and uniformity of the encapsulation layer 4 and the sealing protective film 5, and effectively avoid the generation of gaps and defects. Thus, this embodiment can effectively improve the mechanical stability and reliability of the bulk acoustic wave device encapsulation structure, effectively extend the service life of the bulk acoustic wave device 1 and the reflective heat dissipation layer 3, and ensure that the bulk acoustic wave device 1 can work stably under various working conditions.

[0042] In some preferred embodiments, the thickness of the sealing protective film 5 is less than the thickness of the encapsulation layer 4. In this embodiment, the sealing protective film 5 provides initial sealing and protection for the bulk acoustic wave device 1 and the reflective heat dissipation layer 3, while the encapsulation layer 4 provides final mechanical protection and environmental isolation for the bulk acoustic wave device 1 and the reflective heat dissipation layer 3. This embodiment optimizes the bulk acoustic wave device encapsulation structure by making the thickness of the sealing protective film 5 less than the thickness of the encapsulation layer 4, thereby reducing the overall encapsulation size of the bulk acoustic wave device encapsulation structure while effectively resisting external impacts and environmental stresses, thus contributing to the miniaturization of the bulk acoustic wave device encapsulation structure.

[0043] In some preferred embodiments, step S1 includes: S11. The bulk acoustic wave device 1 is flip-chip bonded onto the packaging substrate 2 based on ultrasonic thermo-press flip-chip bonding technology.

[0044] The ultrasonic thermocompression flip-chip bonding technology of this embodiment is an advanced welding method that combines ultrasonic energy, heat, and pressure. This technology first cleans the contact surfaces of the solder balls 6 formed on the top electrode of the bulk acoustic wave device 1 and the solder pads on the packaging substrate 2 under the action of ultrasonic vibration and pressure. Then, under the synergistic effect of a certain temperature, pressure, and ultrasonic vibration friction, a one-time bonding is achieved between the solder balls 6 and the packaging substrate 2. This ultrasonic thermocompression flip-chip bonding technology of this embodiment can rapidly soften the welding material through the combined energy field of heat and ultrasound, making it easier for plastic deformation. The entire welding process requires low pressure, low temperature, and short time. Therefore, this embodiment can effectively improve the efficiency of flip-chip bonding the bulk acoustic wave device 1 onto the packaging substrate 2. Furthermore, since the ultrasonic thermo-press flip-chip bonding technology of this embodiment does not require photolithography and patterning processes, it can effectively reduce the complexity and cost of flip-chip bonding the bulk acoustic wave device 1 onto the packaging substrate 2. Also, since the ultrasonic thermo-press flip-chip bonding technology does not require flux for cleaning, it can effectively avoid the situation where residual flux affects the adhesion between the liquid material and the bulk acoustic wave device 1 and the packaging substrate 2, resulting in a decrease in interface strength. Compared with existing reflow soldering technology, this embodiment can also avoid welding defects such as warping, non-contact disconnection, and local bridging that may occur during reflow soldering.

[0045] In some preferred embodiments, the ultrasonic power range of the ultrasonic thermocompression flip-chip bonding technology is 0.5-50W, the ultrasonic time range is 50-1000ms, the temperature range is 100-300℃, and the pressure range is 5-100N. The ultrasonic power in this embodiment refers to the ultrasonic energy intensity applied to the welding area during the ultrasonic thermocompression flip-chip bonding process. This embodiment provides sufficient energy to promote plastic deformation and atomic diffusion of the solder by setting the ultrasonic power range to 0.5-50W, while avoiding excessive power that could cause mechanical damage to the bulk acoustic wave device 1. The ultrasonic time in this embodiment refers to the duration of ultrasonic waves acting on the welding area. This embodiment ensures sufficient solder joint formation by setting the ultrasonic time range to 50-1000ms, enabling the bulk acoustic wave device 1 to form a stable and robust connection with the packaging structure. The temperature of ultrasonic thermocompression flip-chip bonding refers to the temperature at which the package substrate 2 or the bulk acoustic wave device 1 is heated during the bonding process. In this embodiment, the temperature range of ultrasonic thermocompression flip-chip bonding is set between 100-300°C to fully soften the solder, thereby reducing its flow resistance and accelerating the atomic diffusion process, thus forming a strong metallurgical bond. Simultaneously, excessively high temperatures are avoided to prevent thermal damage to the sensitive structure of the bulk acoustic wave device 1. The pressure of ultrasonic thermocompression flip-chip bonding refers to the mechanical force applied to the bulk acoustic wave device 1 during the bonding process. In this embodiment, the pressure range of ultrasonic thermocompression flip-chip bonding is set between 5-100N to ensure close contact between the bulk acoustic wave device 1 and the package substrate 2, promoting uniform solder spread and void removal, thereby forming defect-free solder joints.

[0046] In some preferred embodiments, step S11 includes: S111. Multiple bulk acoustic wave devices 1 are flip-chip bonded onto the packaging substrate 2 based on ultrasonic thermo-press flip-chip bonding technology; The bulk acoustic wave device packaging method also includes steps performed after step S4: S5. The bulk acoustic wave device package structure is diced to obtain a single package structure containing only one bulk acoustic wave device 1.

[0047] Step S111 is equivalent to soldering multiple independent bulk acoustic wave (SAW) devices 1 onto the same packaging substrate 2. These SAW devices 1 are treated as a whole in the subsequent packaging process. The dicing in this embodiment refers to using existing cutting, sawing, or other separation techniques to separate the overall packaging structure containing multiple SAW devices 1 into independent packaging units (mono-package structures) containing only one SAW device 1, according to a preset size and shape. This embodiment achieves batch packaging of SAW devices 1 by simultaneously flip-chip soldering multiple SAW devices 1 onto the same packaging substrate 2 and treating these SAW devices 1 as a whole in the subsequent packaging process. After completing the overall packaging, this embodiment separates the mono-package structures containing only one SAW device 1 by dicing the overall packaging structure. This batch processing method avoids the tedious and time-consuming process of individually packaging each SAW device 1. Therefore, this embodiment can effectively improve the parallelism of the SAW device 1 packaging process, thereby effectively improving the packaging efficiency of the SAW device 1.

[0048] In some preferred embodiments, step S5 includes: S51. Perform deflashing and surface treatment on the bulk acoustic wave device packaging structure; S52. The bulk acoustic wave device package structure that has undergone deflashing and surface treatment is diced to obtain a single package structure containing only one bulk acoustic wave device 1.

[0049] Step S51, deflashing, refers to removing excess material or burrs that may be generated on the edges or surface of the package structure during the manufacturing process (such as molding, cutting, etc.). If deflashing is not performed on the bulk acoustic wave (SAW) device package structure, the excess material or burrs located at the edges of the package structure may affect the subsequent cutting accuracy, or even cause short circuits or mechanical interference in the final product. This embodiment can use mechanical grinding, laser trimming, chemical etching, or high-pressure water jetting to achieve deflashing. Specifically, mechanical grinding refers to finely grinding the edges with a grinding wheel or grinding head; laser trimming refers to removing tiny burrs using the precise energy of a laser beam; chemical etching refers to dissolving excess material with a specific solution; and high-pressure water jetting refers to removing burrs using the impact force of a high-speed water jet. The surface treatment in step S51 refers to cleaning, smoothing, or modifying the outer surface of the bulk acoustic wave device (SAW) package structure to improve its surface properties. For example, this can be achieved by cleaning the SAW package structure to remove surface contaminants, polishing to improve surface smoothness, or performing plasma treatment to improve surface wettability or adhesion. This embodiment provides a clean, smooth, and defect-free package structure for subsequent dicing by performing surface treatment on the SAW package structure, thereby ensuring the accuracy and quality of dicing and reducing potential secondary contamination or damage during the dicing process.

[0050] This embodiment effectively solves the problems of flash and surface defects that may be caused by direct slicing by introducing deburring and surface treatment steps before slicing. Specifically, this embodiment removes burrs or excess material on the edges of the bulk acoustic wave device (BAW) package structure by deburring, so as to prevent these defects from being pressed in or torn during the slicing process, thereby affecting the flatness and integrity of the slicing surface. At the same time, this embodiment ensures that the surface of the BAW package structure is clean and free of contaminants by performing surface treatment. This not only helps to improve the cutting efficiency and life of the slicing tool, but also prevents contaminants from being introduced or attached to the new cut surface during the slicing process, thereby ensuring the surface quality of the final single-unit package structure.

[0051] In some preferred embodiments, the liquid material is polyimide. The polyimide material in this embodiment is a high-performance polymer with good fluidity in its liquid state. Therefore, this embodiment can utilize the liquid polyimide material to fully fill the air gap between the bulk acoustic wave device 1 and the encapsulation substrate 2. After curing, the polyimide material can form a solid layer with excellent mechanical properties, thermal stability, and electrical insulation. It should be understood that those skilled in the art can adjust the formulation of the polyimide material to meet the requirements that its acoustic impedance is less than a preset acoustic impedance and its thermal conductivity is greater than a first preset thermal conductivity, thereby ensuring that the reflective heat dissipation layer 3 formed after curing can effectively reflect sound waves and conduct heat.

[0052] In some preferred embodiments, the bulk acoustic wave device packaging method includes the following steps: A1. Multiple bulk acoustic wave devices 1 are flip-chip bonded onto the packaging substrate 2 using ultrasonic thermo-press flip-chip bonding technology. Specifically, the flip-chip bonding process is carried out in a constant temperature environment of 200°C. The duration of ultrasonic action in ultrasonic thermo-press flip-chip bonding technology is 500ms, the ultrasonic power is 5W, and the applied pressure is 20N. Under these process parameters, the electrodes of the bulk acoustic wave devices 1 are connected to the corresponding electrodes on the packaging substrate 2 through solder balls 6. A2. Using the underfill technology in the flip chip packaging process, liquid polyimide material is injected and filled into the air gap formed between the bulk acoustic wave device 1 and the packaging substrate 2. A3. In a vacuum oven, the structure in which liquid polyimide material was poured in step A2 is baked and cured at a temperature of 230°C for 2-4 hours to solidify and shape the liquid polyimide material, thereby forming a reflective heat dissipation layer 3 between the bulk acoustic wave device 1 and the packaging substrate 2. A4. Using vacuum coating technology, cover the structure completed in step A3 with an epoxy resin film of about 3 μm thickness to obtain a sealing protective film 5 for the encapsulated acoustic wave device 1 and the reflective heat dissipation layer 3. Specifically, the vacuum coating technology is carried out at a temperature of 100-160℃ and a pressure of 0.1-5MPa to ensure that the film material forms a firm bond with the encapsulation substrate 2, the bulk acoustic wave device 1 and the reflective heat dissipation layer 3. A5. Using compression molding encapsulation, the structure completed in step A4 is transferred into an encapsulation mold pre-filled with powdered or liquid epoxy resin encapsulating material. The upper and lower molds are closed, and the structure is preheated at 70-85℃ for 20-60 seconds. Then, the temperature is gradually increased to 175℃, and the structure is compressed at 3-20MPa for 30-300 seconds to fully melt the epoxy resin encapsulating material and to encapsulate the structure completed in step A4.

[0053] A6. Bake the encapsulation mold at a temperature of 140-175℃ for 3-6 hours to fully cure the encapsulation material inside the encapsulation mold, thereby forming a stable encapsulation layer 4 outside the sealing protective film 5. A7. After the bulk acoustic wave device packaging structure has been cured and shaped, it is inspected and processed before cutting, such as removing burrs and surface treatment. Then, the bulk acoustic wave device packaging structure is divided and cut according to the packaging area to obtain multiple single-unit packaging structures.

[0054] As can be seen from the above, the bulk acoustic wave device packaging method provided in this application forms an additional and efficient heat dissipation channel between the bulk acoustic wave device 1 and the packaging substrate 2 by filling the space between the bulk acoustic wave device 1 and the packaging substrate 2 with a liquid material whose acoustic impedance is less than that of the bulk acoustic wave device 1 and whose thermal conductivity is greater than a first preset thermal conductivity, and then solidifying the liquid material to obtain a reflective heat dissipation layer 3. Since this application can use this heat dissipation channel to quickly dissipate the heat generated by the bulk acoustic wave device 1, this application can effectively improve the heat dissipation capacity of the bulk acoustic wave device 1. Therefore, this application can effectively improve the power capacity of the bulk acoustic wave device 1. That is, this application is equivalent to improving the power capacity of the bulk acoustic wave device 1 without optimizing the structure of the bulk acoustic wave device 1, thereby effectively solving the problems of performance degradation, increased R&D cycle and design difficulty, and large time and cost investment caused by the need to start from the device design level to improve the power capacity of the bulk acoustic wave device 1.

[0055] Secondly, such as Figure 2 As shown, this application also provides a bulk acoustic wave device packaging structure for improving the power capacity of the bulk acoustic wave device 1. The bulk acoustic wave device packaging structure is made by the bulk acoustic wave device packaging method provided in the first aspect above.

[0056] The bulk acoustic wave device packaging structure provided in this application is made by the bulk acoustic wave device packaging method provided in the first aspect above. The principle of the bulk acoustic wave device packaging structure provided in this embodiment is the same as the principle of the bulk acoustic wave device packaging method provided in the first aspect above, and will not be discussed in detail here.

[0057] As can be seen from the above, the bulk acoustic wave device packaging method and structure provided in this application form an additional and efficient heat dissipation channel between the bulk acoustic wave device 1 and the packaging substrate 2 by filling the space between the bulk acoustic wave device 1 and the packaging substrate 2 with a liquid material whose acoustic impedance is less than that of the bulk acoustic wave device 1 and whose thermal conductivity is greater than a first preset thermal conductivity, and then solidifying the liquid material to obtain a reflective heat dissipation layer 3. Since this application can use this heat dissipation channel to quickly dissipate the heat generated by the bulk acoustic wave device 1, this application can effectively improve the heat dissipation capacity of the bulk acoustic wave device 1. Therefore, this application can effectively improve the power capacity of the bulk acoustic wave device 1. That is, this application is equivalent to improving the power capacity of the bulk acoustic wave device 1 without optimizing the structure of the bulk acoustic wave device 1, thereby effectively solving the problems of performance degradation, increased R&D cycle and design difficulty, and large time and cost investment caused by the need to improve the power capacity of the bulk acoustic wave device 1 from the device design level.

[0058] In the embodiments provided in this application, it should be understood that relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0059] The above are merely embodiments of this application and are not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A packaging method for a bulk acoustic wave device, used to improve the power capacity of the bulk acoustic wave device, characterized in that, The bulk acoustic wave device packaging method includes the following steps: S1. The bulk acoustic wave device is flip-chip soldered onto the packaging substrate; S2. Fill the air gap between the bulk acoustic wave device and the packaging substrate with a liquid material whose acoustic impedance is less than that of the electrodes of the bulk acoustic wave device and whose thermal conductivity is greater than that of a first preset thermal conductivity. The first preset thermal conductivity is greater than that of air. S3. The liquid material is solidified to form a reflective heat dissipation layer between the bulk acoustic wave device and the packaging substrate; S4. Encapsulate the bulk acoustic wave device and the reflective heat dissipation layer so that the encapsulation layer covers the bulk acoustic wave device and the reflective heat dissipation layer, thereby obtaining a bulk acoustic wave device encapsulation structure.

2. The bulk acoustic wave device packaging method according to claim 1, characterized in that, Step S4 includes: S41. The bulk acoustic wave device and the reflective heat dissipation layer are encapsulated using a film material with a thermal conductivity greater than a second preset thermal conductivity, so as to form a sealed protective film that wraps the bulk acoustic wave device and the reflective heat dissipation layer. The second preset thermal conductivity is greater than the thermal conductivity of air. S42. The sealing protective film is encapsulated to form an encapsulation layer that wraps the sealing protective film.

3. The bulk acoustic wave device packaging method according to claim 2, characterized in that, The bulk acoustic wave device, the packaging substrate, the reflective heat dissipation layer, and the sealing protective film constitute an intermediate packaging structure. Step S42 includes: S421. The intermediate encapsulation structure is moved into an encapsulation mold filled with powdered or liquid epoxy resin molding compound. S422. Preheat the packaging mold; S423. Heat the epoxy resin molding compound to a preset temperature and compress the epoxy resin molding compound to encapsulate the sealing protective film. S424. The packaging mold is baked to cure the epoxy resin molding compound inside the packaging mold, thereby obtaining a packaging layer that wraps the sealing protective film.

4. The bulk acoustic wave device packaging method according to claim 2, characterized in that, The thickness of the sealing protective film is less than the thickness of the encapsulation layer.

5. The bulk acoustic wave device packaging method according to claim 1, characterized in that, Step S1 includes: S11. The bulk acoustic wave device is flip-chip bonded onto the packaging substrate based on ultrasonic thermo-press flip-chip bonding technology.

6. The bulk acoustic wave device packaging method according to claim 5, characterized in that, The ultrasonic power range of the ultrasonic thermo-press flip-chip welding technology is 0.5-50W, the ultrasonic time range is 50-1000ms, the temperature range is 100-300℃, and the pressure range is 5-100N.

7. The bulk acoustic wave device packaging method according to claim 5, characterized in that, Step S11 includes: S111. Multiple bulk acoustic wave devices are flip-chip bonded onto a packaging substrate based on ultrasonic thermo-press flip-chip bonding technology; The bulk acoustic wave device packaging method further includes steps performed after step S4: S5. The bulk acoustic wave device packaging structure is diced to obtain a single-unit packaging structure containing only one bulk acoustic wave device.

8. The bulk acoustic wave device packaging method according to claim 7, characterized in that, Step S5 includes: S51. Perform burr removal and surface treatment on the bulk acoustic wave device packaging structure; S52. The bulk acoustic wave device package structure that has undergone deflashing and surface treatment is diced to obtain a single package structure containing only one bulk acoustic wave device.

9. The bulk acoustic wave device packaging method according to claim 1, characterized in that, The liquid material is a polyimide material.

10. A bulk acoustic wave device packaging structure for improving the power capacity of a bulk acoustic wave device, characterized in that, The bulk acoustic wave device packaging structure is made by the bulk acoustic wave device packaging method according to any one of claims 1-9.

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