Packaging method for suppressing residual vibration of vibrating diaphragm

Abstract

The invention discloses a packaging method for suppressing residual vibration of a vibrating diaphragm, which relates to the technical field of chip packaging and comprises the following steps of: painting glue: painting patch glue on a carrier according to a preset thickness; and embedding the chip: inversely buckling the chip to enable the lining body of the chip to be embedded into the patch, enabling the vibrating diaphragm of the chip to be parallel to the carrier, and ensuring that the sound hole in the carrier is located in the projection range of the vibrating diaphragm. The chip is embedded in the patch adhesive instead of being suspended on the patch adhesive, and the packaging process of the carrier is improved, so that residual vibration is effectively reduced; when the thickness of the patch glue and the glue climbing height range are determined, sound holes with different sizes can be selected according to chips with different frequencies; when the size of the sound hole is fixed, different patch adhesive thicknesses and adhesive climbing height ranges can be selected according to chips with different frequencies, and the practicability is high.

Description

Technical Field

[0001] This invention belongs to the field of chip packaging technology, and specifically relates to a packaging method for suppressing residual vibration of a diaphragm. Background Technology

[0002] In PMUT (Piezoelectric Micromechanical Ultrasonic Transducer) devices, the diaphragm is one of the key components of the ultrasonic transducer chip. A diaphragm is a thin-film element capable of vibrating and converting electrical energy into mechanical energy, or vice versa. Diaphragm vibration refers to the vibration of the diaphragm under the influence of an electrical signal; residual vibration refers to the phenomenon where the diaphragm continues to vibrate due to inertia after the electrical signal disappears. For most current applications of ultrasonic transducers, lower residual vibration is more advantageous; however, due to limitations in packaging technology, the magnitude of residual vibration often exceeds the application requirements, significantly diminishing the advantages of ultrasonic transducers.

[0003] The ultrasonic transducer packaging process involves using adhesive to create a soft contact and fix the transducer chip to a carrier. This soft contact eliminates resonance caused by the chip, thereby increasing the speed at which diaphragm vibration decreases and allowing the diaphragm to quickly reach a relatively stationary state after the driving signal disappears. However, existing ultrasonic transducers still exhibit significant residual vibration, which cannot meet the requirements for close-range ranging. Summary of the Invention

[0004] In view of the problems mentioned in the background art, the purpose of the present invention is to provide a packaging method for suppressing residual vibration of the diaphragm, so as to solve the problems mentioned in the background art.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

[0006] A packaging method for suppressing residual vibration of a diaphragm includes the following steps:

[0007] Applying adhesive: Apply the adhesive to the substrate to a predetermined thickness. The substrate has sound holes.

[0008] Chip embedding: The chip substrate is then embedded in the adhesive, with the chip diaphragm parallel to the carrier, the opening facing the acoustic hole, and the acoustic hole on the carrier located within the projection range of the diaphragm.

[0009] Preferably, the adhesive patch is arranged in a dam-like shape on both the inner and outer sides of the liner.

[0010] Preferably, in the adhesive application step, the inner adhesive is first applied to a designated position on the carrier and pre-cured. Then, the outer adhesive is applied to the outer and top layers of the cured inner adhesive. Finally, the liner is embedded in the outer adhesive and cured.

[0011] Preferably, the fixed position is around the sound hole.

[0012] Preferably, the adhesive is sprayed: after the chip embedding step is completed, an adhesive of a preset thickness is sprayed around the substrate, and the adhesive is used to connect the outer wall of the substrate, the outer wall of the outer adhesive and the carrier.

[0013] Preferably, the adhesive spray is lower than the diaphragm.

[0014] Preferably, the inner diameter of the acoustic aperture is in the range of 1000-1100 μm.

[0015] Preferably, the carrier comprises three substrates arranged vertically, with pads mounted on the side of any substrate facing other substrates, adjacent substrates being fixedly connected by the pads, and filler glue filling the space between adjacent substrates.

[0016] Preferably, there is a gap between the filler adhesive and the solder pad.

[0017] This invention proposes a packaging method for suppressing diaphragm residual vibration. By embedding the chip inside the adhesive rather than suspending it on the adhesive, and by using an improved carrier packaging process, residual vibration is effectively reduced. When the thickness and creepage height of the adhesive are determined, different sizes of acoustic holes can be selected for chips of different frequencies. When the size of the acoustic hole is fixed, different thicknesses of adhesive and creepage heights can be selected for chips of different frequencies, making it highly practical.

[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] Figure 1 This is a front cross-section of the packaging method for suppressing diaphragm residual vibration proposed in this invention. Figure 1 ;

[0020] Figure 2 This is a front cross-section of the packaging method for suppressing diaphragm residual vibration proposed in this invention. Figure 2 ;

[0021] Figure 3 This is a front cross-section of the packaging method for suppressing diaphragm residual vibration proposed in this invention. Figure 3 ;

[0022] Figure 4 This is a structural diagram of the carrier for a packaging method for suppressing residual vibration of a diaphragm proposed in this invention.

[0023] Reference numerals: 1. Chip; 11. Diaphragm; 12. Substrate; 2. Adhesive; 21. Inner adhesive; 22. Outer adhesive; 3. Carrier; 31. Substrate; 32. Filler adhesive; 33. Pad; 4. Sound hole; 5. Spray adhesive. Detailed Implementation

[0024] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar symbols denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0025] Example 1

[0026] refer to Figures 1 to 4 The packaging method for suppressing residual vibration of a diaphragm described in this embodiment includes a chip 1, a patch adhesive 2 for fixing the chip 1, and a carrier 3 for carrying the chip 1 and the patch adhesive 2. The chip 1 includes a diaphragm 11 and a liner 12 surrounding the diaphragm 11. The chip 1 is in the shape of a lampshade with the opening facing downward. The patch adhesive 2 is filled between the liner 12 and the carrier 3. The liner 12 is embedded in the patch adhesive 2. The diaphragm 11 is parallel to the carrier 3 and has a sound hole 4 opened in the projection range of the diaphragm 11 within the carrier 3.

[0027] The adhesive patch 2 forms a dam-like shape on both the inner and outer sides of the liner 12.

[0028] Ultrasonic waves are emitted from or enter the chip 1 through the sound hole 4. The ultrasonic waves charge the diaphragm 11, causing the diaphragm 11 to vibrate. The adhesive 2 forms a concave shape below the substrate 12, which is narrow at the top and wide at the bottom. The load generated by the vibration of the diaphragm 11 of the chip 1 is transferred to the adhesive 2 and the carrier 3 through the tension balancing system. At the same time, it forms a dam-like structure inside and outside the substrate 12, forming a stable triangular force system, achieving mechanical stability and reducing the vibration speed of the diaphragm 11 more quickly.

[0029] Because the adhesive 2 is fluid and the transducer chip 1 itself has gravity, it is difficult to achieve a thicker stack of adhesive 2 using the above encapsulation process. Therefore, we use a "secondary adhesive application" method to achieve an encapsulation process for extra-thick adhesive.

[0030] Specifically, inner adhesive 21 is drawn at a designated position on carrier 3, and the inner adhesive 21 is pre-cured. Then, outer adhesive 22 is drawn on the outer and top layers of the cured inner adhesive 21. Finally, chip 1 is mounted on the outer adhesive 22 and cured. This forms a structure as shown in the diagram. Figure 2 The structure shown has an inner adhesive 21 distributed between the bottom of the liner 12 and the carrier 3, and an outer adhesive 22 surrounding the liner 12 and connecting the inner adhesive 21 and the carrier 3.

[0031] The fixed position is around the sound hole 4.

[0032] After the inner adhesive 21 is pre-cured, it forms a certain thickness and has a certain elasticity. At this time, embedding the chip 1 will not cause the inner adhesive 21 to become thinner due to the weight of the chip 1 itself. The outer adhesive 22 increases the amount of adhesive on the left and right sides of the inner adhesive 21, widens the bottom of the adhesive 2, and also ensures that the substrate 12 has a certain adhesive climbing height. While increasing the adhesive 2, it maintains the "U"-shaped adhesive with a narrow top and wide bottom. This ensures that the transducer can quickly bring the diaphragm 11 to a relatively static state after the high voltage drive ends.

[0033] Preferably, a predetermined thickness of adhesive 5 is sprayed onto the outer wall of the substrate 12. The adhesive 5 is tightly bonded to the carrier 3, the adhesive 2, and the outer side of the substrate 12. The adhesive 5 applies a downward and outward pulling force to the outer side of the chip 1, thereby quickly reducing the vibration speed of the diaphragm 11 and thus reducing the residual vibration of the diaphragm 11. At this time, the outer adhesive 2, adhesive 5, carrier 3, and substrate 12 form a right angle and a dam-like structure, which stabilizes the chip 1 and also effectively alleviates the amplitude of the chip 1 caused by the vibration of the diaphragm 11.

[0034] It is worth noting that, in order to avoid affecting the normal vibration effect of the diaphragm 11, the adhesive spray 5 is lower than the diaphragm 11.

[0035] The size of the acoustic aperture 4 is related to the vibration frequency of the chip 1. If the diameter of the acoustic aperture 4 is too small, there will be residual vibration tailing; if the diameter of the acoustic aperture 4 is too large, it will result in large residual vibration and weak signal. Therefore, preferably, the diameter of the acoustic aperture 4 is in the range of 1000-1100um.

[0036] The carrier 3 is typically formed by stacking and packaging three substrates 31, i.e., from top to bottom, there are three substrates 31: upper, middle, and lower. Each substrate 31 has a slightly raised pad 33 on the side facing other substrates 31. Figure 4 As shown, multiple sets of solder pads 33 are soldered to the bottom end of the upper substrate 31, the upper and lower end faces of the middle substrate 31, and the top end of the lower substrate 31. The solder pads 33 on adjacent substrates 31 are soldered together with solder paste.

[0037] However, the carrier supported by the above-mentioned traditional packaging process has certain defects: it is fixed by rigid contact between the pads 33 and the solder paste. When the chip 1 is driven to vibrate, the vibration force will be gradually transmitted to the three-layer substrate 31 through the solder paste and the pads 33, thereby causing the entire ultrasonic transducer to resonate. Once the chip 1 loses its drive, the entire ultrasonic transducer will continue to vibrate due to inertia. The chip 1 cannot quickly reach a relatively stationary state, and thus cannot achieve the effect of quickly reducing residual vibration.

[0038] Therefore, filler adhesive 32 is filled between adjacent substrates 31 using a screen printing process. After the filler adhesive 32 has cured, a three-layer substrate 31 stacking and reflow packaging process is performed, and solder paste is used to solder the pads 33 of the three-layer substrates 31 together.

[0039] The thickness of the cured filler adhesive 32 should not exceed the height between the two solder pads 33 after soldering, so as to avoid the filler adhesive 32 being too thick and stretching the substrate 31, which would prevent the solder paste between the substrates 31 from connecting; at the same time, it should be ensured that the cured filler adhesive 32 is in contact with the adjacent substrates 31, so as to avoid the filler adhesive 32 being too thin and unable to play a vibration damping role.

[0040] It is worth noting that there is a gap between the filler adhesive 32 and the pad 33. If the filler adhesive 32 sticks to the pad 33, the solder paste will detach from the pad 33 after the reflow process, and an electrical connection cannot be formed between the upper and lower substrates 31.

[0041] The chip 1 produced by this packaging process is embedded inside the adhesive 2, rather than floating on the adhesive 2, which effectively reduces residual vibration. When the thickness of the adhesive and the range of the adhesive climbing height are determined, different sizes of acoustic holes 4 can be selected for chips 1 of different frequencies. When the size of the acoustic hole 4 is fixed, different thicknesses of the adhesive 2 and the range of the adhesive climbing height can be selected for chips 1 of different frequencies, which is highly practical. The carrier 3 after the improved packaging process further reduces residual vibration.

[0042] It should be understood that the terms "length", "thickness", "upper", "lower", "inner", "outer", "axial", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0043] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0044] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0045] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0046] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A packaging method for suppressing residual vibration of a diaphragm, characterized in that: Includes the following steps: Apply adhesive: Apply the adhesive (2) to the carrier (3) with a predetermined thickness. The carrier (3) has a sound hole (4). Chip embedding: The substrate (12) of the chip (1) is then embedded in the adhesive (2). The diaphragm (11) of the chip (1) is parallel to the carrier (3), with the opening facing the sound hole (4) and ensuring that the sound hole (4) on the carrier (3) is within the projection range of the diaphragm (11).

2. The packaging method for suppressing diaphragm residual vibration according to claim 1, characterized in that: The adhesive patch (2) forms a dam-like structure on both the inner and outer sides of the liner (12).

3. The packaging method for suppressing diaphragm residual vibration according to claim 1, characterized in that: In the process of applying the adhesive, the inner adhesive (21) is first applied to the designated position on the carrier (3), and the inner adhesive (21) is pre-cured. Then, the outer adhesive (22) is applied to the outer and top layers of the cured inner adhesive (21). The liner (12) is then embedded into the outer adhesive (22) and cured.

4. The packaging method for suppressing diaphragm residual vibration according to claim 1, characterized in that: The fixed position is one revolution around the sound hole (4).

5. The packaging method for suppressing diaphragm residual vibration according to claim 1, characterized in that: Spraying adhesive: After the chip embedding step is completed, spray adhesive (5) of a preset thickness is applied around the substrate (12). The adhesive (5) connects the outer wall of the substrate (12), the outer wall of the outer adhesive (22), and the carrier (3).

6. The packaging method for suppressing diaphragm residual vibration according to claim 5, characterized in that: The adhesive spray (5) is shorter than the diaphragm (11).

7. The packaging method for suppressing diaphragm residual vibration according to claim 1, characterized in that: The inner diameter of the acoustic hole (4) ranges from 1000 to 1100 μm.

8. The packaging method for suppressing diaphragm residual vibration according to any one of claims 1-7, characterized in that: The carrier (3) includes three substrates (31) arranged vertically. A pad (33) is installed on the side of any substrate (31) facing other substrates (31). Adjacent substrates (31) are fixedly connected by the pad (33). Filler glue (32) is filled between adjacent substrates (31).

9. The packaging method for suppressing diaphragm residual vibration according to claim 8, characterized in that: There is a gap between the filler glue (32) and the pad (33).

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