A piezoelectric MEMS synthetic jet cooling chip integrated with a fluidic cavity-silicon bottom

Abstract

A piezoelectric MEMS synthetic jet cooling chip integrating a jet cavity and a silicon substrate includes: a piezoelectric diaphragm, an integrated silicon substrate, and a PCB substrate; at least one jet cavity is integrally formed inside the integrated silicon substrate, and the jet cavity penetrates the substrate; two opposing piezoelectric diaphragms are disposed on the top of the jet cavity, the two piezoelectric diaphragms are located side by side on the top of the substrate, and span the jet cavity; and each piezoelectric diaphragm has one edge bonded to the top of the integrated silicon substrate, and a gap between its other edge and its opposing piezoelectric diaphragm; a jet hole is formed on the PCB substrate; the jet hole is coaxially arranged with the jet cavity; and the jet cavity forms an airflow channel sidewall extending downward from the edge region of the piezoelectric diaphragm to the PCB substrate, the airflow channel sidewall being configured such that the cross-sectional area of ​​the jet cavity gradually decreases from the edge region of the piezoelectric diaphragm toward the PCB substrate.

Description

Technical Field

[0001] This invention relates to the field of heat dissipation technology for large microelectromechanical systems (MEMS), specifically to a high-efficiency active heat dissipation device for compact electronic devices, particularly a piezoelectric MEMS synthetic jet cooling chip with an integrated jet cavity and silicon substrate. Background Technology

[0002] As compact electronic devices such as smartphones, smartwatches, and tablets evolve towards higher performance and greater integration, transistor density continues to increase, leading to a simultaneous surge in device power consumption and heat flux. Localized overheating has become a key bottleneck restricting device performance and reliability. Statistics show that nearly 50% of electronic component failures are caused by overheating. Therefore, developing efficient, low-power heat dissipation solutions suitable for micro-sized spaces is crucial.

[0003] Currently, thermal management solutions for compact electronic devices mainly include passive cooling and active cooling. Passive cooling (such as graphite sheets and heat spreaders) has a simple structure and no additional power consumption, but its heat dissipation capacity is limited and it is difficult to meet the heat dissipation requirements of high-performance chips. Traditional active cooling solutions (such as micro fans) can provide forced convection, but they generally have problems such as large size, high power consumption, and significant noise, making them difficult to integrate into ultra-thin devices with strict requirements on thickness and volume.

[0004] Piezoelectric MEMS synthetic jet technology is considered an ideal technological path to solve the heat dissipation problem in compact spaces due to its advantages such as miniaturization, low power consumption, no mechanical wear, and fast response. Existing piezoelectric MEMS cooling chips mostly adopt a "diaphragm + separate perforated plate" structural design, which has two major drawbacks: 1. The jet cavity and silicon substrate are separately assembled, making it difficult to precisely control the size and position accuracy. Furthermore, the airflow path has right-angle steps, which easily cause airflow separation and eddies, resulting in high flow resistance and low jet efficiency; 2. The connection constraint design between the diaphragm and the substrate is relatively large, limiting the free vibration area of ​​the diaphragm and resulting in insufficient diaphragm deflection, further reducing airflow generation capacity and heat dissipation efficiency.

[0005] Patent CN119393323A discloses a side-discharge synthetic jet pump device, which forms an L-shaped fluid path through a cavity plate and a flow direction conversion component, achieving lateral airflow output. This reduces the longitudinal space required by the device in the airflow direction, facilitating ultra-thin integration. However, its structure is still a multi-layer assembly, with abrupt changes in the airflow path, easily leading to airflow separation and eddies, increasing flow resistance, and losing diaphragm energy. Patent CN106574638A provides an air cooling system utilizing synthetic jet or airflow generators and multiple airflow generators. By placing a flexible vibrating structure inside or around the fins, it achieves direct impact cooling of the heat-generating element. This solution focuses on heat sink integration applications but does not address the optimization problem of the internal airflow channel of the MEMS synthetic jet generator itself.

[0006] Therefore, there is an urgent need for an innovative structural design that can fundamentally optimize the airflow path and improve diaphragm performance while maintaining the inherent advantages of piezoelectric MEMS technology in miniaturization and low power consumption, thereby significantly improving the heat dissipation efficiency of synthetic jet cooling chips. Summary of the Invention

[0007] This invention addresses the shortcomings of existing technologies by providing a piezoelectric MEMS synthetic jet cooling chip that integrates a jet cavity and a silicon substrate. The cooling chip features a dual-diaphragm driven structure, based on the core principles of piezoelectric effect and synthetic jet heat dissipation. It employs a jet cavity integrally formed on a silicon substrate, achieving performance optimization through structural innovation.

[0008] A piezoelectric MEMS synthetic jet cooling chip integrating a jet cavity and a silicon substrate includes: a piezoelectric diaphragm, an integrated silicon substrate, and a PCB substrate; at least one jet cavity is integrally formed inside the integrated silicon substrate, and the jet cavity penetrates the substrate; two opposing piezoelectric diaphragms are disposed on the top of the jet cavity, the two piezoelectric diaphragms are located side by side on the top of the substrate, and span the jet cavity; and each piezoelectric diaphragm has one edge bonded to the top of the integrated silicon substrate, and a gap between its other edge and its opposing piezoelectric diaphragm.

[0009] The bottom of the integrated silicon substrate is fixed to the top of the PCB substrate, and the PCB substrate has a jet hole; the jet hole and the jet cavity are coaxially arranged.

[0010] Furthermore, the jet cavity forms an airflow channel sidewall extending downward from the edge region of the piezoelectric diaphragm to the PCB substrate, and the airflow channel sidewall is configured such that the cross-sectional area of ​​the jet cavity gradually decreases from the edge region of the piezoelectric diaphragm toward the PCB substrate;

[0011] Under the action of an AC drive signal, the piezoelectric diaphragm of the chip reciprocates. When the piezoelectric diaphragm moves downward, it compresses the air in the jet cavity formed by the integrated silicon substrate, the diaphragm and the PCB substrate, and ejects the impact heat source from the jet hole. When the piezoelectric diaphragm moves upward, the cavity generates negative pressure and draws in low-temperature ambient air from below.

[0012] The working principle of the chip described in this invention is as follows: The chip adopts a top-cap-less design, following an airflow direction of "bottom-side intake and bottom-side exhaust". Its working principle is as follows: An AC drive signal acts on the upper and lower electrodes of the piezoelectric diaphragm, causing the piezoelectric diaphragm to reciprocate under the piezoelectric effect.

[0013] During the downward jetting phase of the piezoelectric diaphragm, the diaphragm moves towards the PCB substrate, compressing the jet cavity formed by the integrated silicon substrate, the diaphragm, and the substrate. When the airflow channel of the jet cavity is a tapered slope or arc-shaped channel, the air inside the cavity flows along a smooth path, without energy loss caused by right-angle steps, and is ejected at high speed through the integrated jet orifice under positive pressure. When the airflow velocity reaches a threshold, a vortex ring forms at the edge of the jet orifice due to the boundary layer separation effect. The high-speed jet with the vortex ring vertically impacts the surface of the hot zone of the electronic device, efficiently disturbing the thermal boundary layer and enhancing heat exchange.

[0014] During the upward air intake phase of the piezoelectric diaphragm, the driving signal is reversed, causing the diaphragm to move away from the PCB substrate, creating a negative pressure within the cavity. At this time, the high-speed jet ejected in the previous stage moves away from the jet orifice under the influence of its self-induced velocity, and its high momentum characteristics form a "gas barrier," effectively preventing the backflow of hot air. Simultaneously, the optimized connection design between the integrated substrate and the diaphragm reduces constraints, allowing for a greater diaphragm retraction and a higher negative pressure within the cavity, enabling the rapid intake of fresh, cool air from the surrounding environment and providing ample cooling for the next jet cycle.

[0015] The integrated design of the jet cavity and silicon substrate of the chip described in this invention completely solves the problem of dimensional and positional accuracy deviation caused by separate assembly, ensuring the consistency of the jet path; the tapered airflow channel eliminates the abrupt interface of the traditional structure, making the airflow smoother, greatly reducing flow resistance and energy loss, and allowing the energy generated by diaphragm vibration to be efficiently converted into jet kinetic energy, thereby improving jet speed and stability.

[0016] Furthermore, the airflow channel of the jet cavity is a straight inclined surface that tapers towards the PCB substrate.

[0017] Furthermore, the airflow channel of the jet cavity is a streamlined curved surface that tapers towards the PCB substrate.

[0018] Furthermore, the airflow channel of the jet cavity is composed of a multi-level stepped plane that tapers towards the PCB substrate. The multi-level stepped plane includes at least three steps.

[0019] Furthermore, the airflow channel of the jet cavity is composed of a fully enclosed arc-shaped surface that tapers towards the PCB substrate, and the fully enclosed arc-shaped surface smoothly transitions from the edge of the piezoelectric diaphragm to the bottom of the integrated silicon substrate; and no support structure is provided in the substrate.

[0020] Furthermore, the piezoelectric diaphragm is bonded and fixed to the top of the integrated silicon substrate through its edge, and the main body of the diaphragm outside the bonding area is a free vibration part.

[0021] Furthermore, the integrated silicon substrate is integrally formed through bulk silicon micromachining, making the jet cavity and its airflow channel sidewalls and the substrate body a single structure without assembly seams.

[0022] Furthermore, the frequency of the AC drive signal applied to the chip is matched with the resonant frequency of the piezoelectric diaphragm to generate resonance and maximize the vibration amplitude.

[0023] Furthermore, the piezoelectric diaphragm is fixed to the integrated silicon substrate via a narrow-edge bonding structure. The bonding area is concentrated only in a very small region at the edge of the piezoelectric diaphragm, thereby maximizing the effective vibration area of ​​the diaphragm and ensuring that the diaphragm has a larger vibration amplitude, thus improving the chamber air compression efficiency and airflow generation capability.

[0024] The beneficial effects of this invention are as follows:

[0025] The chip's jet cavity is integrally formed with the silicon substrate, eliminating assembly errors and leakage points and ensuring consistent airflow paths. The gradually sloping airflow channel of the jet cavity, employing straight sloping surfaces, streamlined curved surfaces, and fully enclosed arc surfaces, eliminates right-angle steps, resulting in extremely smooth airflow, significantly reducing flow resistance and energy loss, and enabling more efficient conversion of the diaphragm's vibrational energy into jet kinetic energy. The constrained and optimized design of the narrow-edge bonding between the chip's substrate and the piezoelectric diaphragm releases the diaphragm's vibrational potential, increasing the vibration amplitude and thus improving the chamber's air compression ratio and intake capacity. The synergistic effect of these three structural features ultimately leads to a significant enhancement in the velocity, stability, and impact strength of the synthesized jet, with heat dissipation efficiency far exceeding that of traditional discrete structures.

[0026] The chip employs an integrated structure, eliminating the need for separate via plates and other assembly components, simplifying chip stacking and facilitating further reduction in overall chip thickness and volume. Furthermore, the coverless design enhances space utilization flexibility and avoids reliability issues such as loosening and leakage that can arise from assembling multiple components, resulting in better sealing and structural stability. This allows the chip of this invention to be seamlessly integrated into space-sensitive compact electronic devices such as smartphones and smartwatches.

[0027] This invention can be manufactured using mature semiconductor MEMS processing technology (such as bulk silicon micromachining, bonding, etc.), has good compatibility with existing production lines, is suitable for large-scale, low-cost mass production, and has strong product consistency. Attached Figure Description

[0028] Figure 1 This is a schematic cross-sectional view of the synthetic jet cooling chip described in Embodiment 1 of the present invention;

[0029] Figure 2 This is a schematic cross-sectional view of the synthetic jet cooling chip described in Example 2;

[0030] Figure 3 This is a schematic cross-sectional view of the synthetic jet cooling chip described in Example 3;

[0031] Figure 4 This is a cross-sectional structural diagram of the synthetic jet cooling chip described in Example 4.

[0032] in,

[0033] FM: Piezoelectric diaphragm; S: Substrate; P: PCB substrate; AF: Jet hole; BL: Airflow channel sidewall. Detailed Implementation

[0034] To make the objectives, technical solutions, beneficial effects, and significant advancements of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings provided in the examples of the present invention. Obviously, all the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] In the description of this application, unless otherwise expressly specified and limited, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; the term "multiple" refers to two or more; unless otherwise specified or explained, the terms "connected," "fixed," etc., should be interpreted broadly. For example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0036] Example 1: Straight inclined plane gradually narrowing airflow channel

[0037] like Figure 1 As shown, a piezoelectric MEMS synthetic jet cooling chip integrating a jet cavity and a silicon substrate includes, from top to bottom: a piezoelectric diaphragm FM, an integrated silicon substrate S, and a PCB substrate P. The chip features a dual-diaphragm driving structure to generate a stronger synthetic jet effect. The substrate S and the PCB substrate P have consistent peripheral shapes and dimensions.

[0038] The PCB substrate P is located at the bottom layer and is used to support and fix the substrate S and provide a drive electrode interface. A jet hole AF is formed on the PCB substrate P. The top of the PCB substrate is connected to the bottom of the substrate S by solder balls.

[0039] The substrate S is an integrated silicon-based substrate, fabricated using monocrystalline silicon integral molding. It serves as the core support structure located between the piezoelectric diaphragm FM and the PCB substrate. An integrally molded jet cavity is formed within the substrate material, directly machined into the silicon substrate material rather than through the assembly of independent perforated plates. This integral molding structure significantly improves the structural precision and sealing between the jet cavity and the silicon substrate, avoiding assembly errors and sealing risks associated with traditional assembly structures. The jet cavity penetrates the substrate S and tapers towards the PCB substrate P. Furthermore, the jet cavity and the jet hole AF of the PCB substrate P are coaxially aligned.

[0040] Two piezoelectric diaphragms FM are disposed opposite each other on the top of the substrate S, located on the uppermost layer of the chip. They form a triangular composite diaphragm structure to provide reciprocating vibration power. One side of each piezoelectric diaphragm FM is fixed to the edge of the top of the substrate S near the jet cavity via a narrow-edge bonding structure, while the other side has a certain gap with the oppositely disposed piezoelectric diaphragm FM. The bonding area is concentrated only in a very small region at the edge of the piezoelectric diaphragm FM, thereby maximizing the effective vibration area of ​​the diaphragm and ensuring a larger vibration amplitude, thus improving the chamber air compression efficiency and airflow generation capability.

[0041] The inner wall of the jet cavity (i.e., the inner sidewall of the substrate S) forms an airflow channel sidewall BL extending from the edge region of the piezoelectric diaphragm FM to the PCB substrate P. The airflow channel sidewall BL defines the boundary of the airflow, and as... Figure 1 As shown, the sidewall BL of the airflow channel is processed into a straight inclined surface. The straight inclined surface starts from the edge of the piezoelectric diaphragm FM and extends linearly and gradually towards the PCB substrate P side (airflow outlet side) until it smoothly connects with the cavity edge on the PCB substrate P. This forms a smooth airflow channel with a linearly changing cross-section between the lower surface of the piezoelectric diaphragm FM, the inner sidewall of the substrate S, and the PCB substrate. The smooth inclined structure forms an airflow path without abrupt interface changes, which can effectively reduce energy loss caused by abrupt changes in the airflow path and improve airflow transmission efficiency.

[0042] Furthermore, the spacing between the piezoelectric diaphragms FM is smaller than the radial profile of the jet hole AF of the PCB substrate P.

[0043] During operation, the drive circuit applies an AC voltage to the piezoelectric diaphragm FM. During the downward vibration jet phase of the piezoelectric diaphragm FM, the air within the jet cavity formed by the integrated silicon substrate, the piezoelectric diaphragm, and the PCB substrate is compressed. The airflow converges along a gradually narrowing straight inclined channel and is ejected at high speed from the jet orifice AF, forming an impact jet with vortex rings that vertically impacts the heat source surface. During the upward vibration intake phase of the piezoelectric diaphragm FM, the chamber volume increases, creating a negative pressure. Simultaneously, the previously ejected high-momentum jet has moved away from the orifice, forming an "air curtain" to prevent hot air recirculation. This allows for the intake of surrounding low-temperature air from below, preparing for the next cycle. This cycle repeats continuously, achieving continuous and efficient heat dissipation from the hot spot.

[0044] Example 2: Curved tapering airflow channel

[0045] like Figure 2 As shown, a piezoelectric MEMS synthetic jet cooling chip integrating a jet cavity and a silicon substrate includes, from top to bottom: a piezoelectric diaphragm FM, an integrated silicon substrate S, and a PCB substrate P. This embodiment is similar to Embodiment 1, differing only in the outline of the airflow channel sidewall BL. The following description only outlines the distinguishing features; identical details will not be repeated.

[0046] The airflow channel sidewall BL adopts a smooth, tapered curve structure. The sidewall profile is a continuous, smooth arc shape, without any sharp edges or inflections from the piezoelectric diaphragm FM side to the PCB substrate P side. It is processed into an arc-shaped tapering channel. The arc-shaped airflow channel sidewall BL starts from the edge connecting the piezoelectric diaphragm FM and extends in an arc-shaped tapering slope towards the PCB substrate P side until it smoothly connects with the cavity edge on the PCB substrate P. This forms an arc-shaped, smooth airflow channel between the lower surface of the piezoelectric diaphragm FM, the inner sidewall of the substrate S, and the PCB substrate. Compared to the straight, sloping tapering channel of Embodiment 1, the curved tapering structure of this embodiment can guide the airflow to turn and accelerate more smoothly, further suppressing boundary layer separation and vortex generation, thus achieving better results in reducing flow resistance and improving airflow transmission efficiency.

[0047] Example 3: Stepped gradually narrowing airflow channel

[0048] like Figure 3 As shown, a piezoelectric MEMS synthetic jet cooling chip integrating a jet cavity and a silicon substrate includes, from top to bottom: a piezoelectric diaphragm FM, an integrated silicon substrate S, and a PCB substrate P. This embodiment is similar to Embodiment 1, differing only in the outline of the airflow channel sidewall BL. The following description only outlines the distinguishing features; identical details will not be repeated.

[0049] The airflow channel sidewall BL is processed into a three-segment stepped tapering channel. Starting from the edge connecting the piezoelectric diaphragm FM, the stepped tapering airflow channel sidewall BL tapers in three steps towards the PCB substrate P. Each step recedes towards the central axis, gradually reducing the cross-section of the airflow channel. This forms a stepped tapering airflow channel between the lower surface of the piezoelectric diaphragm FM, the inner sidewall of the substrate S, and the PCB substrate. Compared to the straight inclined channel of Embodiment 1, the stepped tapering structure can flexibly adapt to different heat dissipation requirements in terms of flow resistance and airflow velocity by adjusting the number of steps, the amount of receding, and the height, while maintaining the controllability of the manufacturing process.

[0050] Example 4: Fully Enclosed Arc-Shaped Airflow Channel

[0051] like Figure 4 As shown, a piezoelectric MEMS synthetic jet cooling chip integrating a jet cavity and a silicon substrate includes, from top to bottom: a piezoelectric diaphragm FM, an integrated silicon substrate S, and a PCB substrate P. This embodiment is similar to Embodiment 1, differing only in the outline of the airflow channel sidewall BL. The following description only outlines the distinguishing features; identical details will not be repeated.

[0052] The airflow channel sidewall BL forms a large-arc cavity wall that smoothly transitions from the outer edge of the piezoelectric diaphragm PM to the bottom of the PCB substrate 3. Its shape resembles a quarter sphere or part of an ellipsoid, without any direct connections or sharp edges. Furthermore, this embodiment eliminates any intermediate support pillars that might exist inside the substrate S. The airflow channel sidewall BL directly connects the piezoelectric diaphragm FM to the PCB substrate, maximizing the cavity volume and achieving the smoothest possible airflow path. Theoretically, this can completely eliminate airflow separation zones and vortex dead zones, making it one of the structural forms that achieves optimal airflow transmission efficiency.

[0053] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is merely for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in the embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A piezoelectric MEMS synthetic jet cooling chip integrating a jet cavity and a silicon substrate, characterized in that... include: The device comprises a piezoelectric diaphragm (FM), an integrated silicon substrate (S), and a PCB substrate (P). At least one jet cavity is integrally formed inside the integrated silicon substrate (S), extending through the integrated silicon substrate (S). Two opposing piezoelectric diaphragms (FM) are disposed at the top of the jet cavity, side-by-side on the top of the integrated silicon substrate (S), spanning the jet cavity. Furthermore, one edge of each piezoelectric diaphragm (FM) is bonded and fixed to the top of the integrated silicon substrate (S), while a gap exists between its other edge and its opposing piezoelectric diaphragm (FM). The bottom of the integrated silicon substrate (S) is fixed to the top of the PCB substrate (P), and the PCB substrate (P) has a jet hole (AF); the jet hole (AF) is coaxially arranged with the jet cavity; Furthermore, the jet cavity forms an airflow channel sidewall (BL) extending downward from the edge region of the piezoelectric diaphragm (FM) to the PCB substrate (P), and the airflow channel sidewall (BL) is configured such that the cross-sectional area of ​​the jet cavity gradually decreases from the edge region of the piezoelectric diaphragm (FM) toward the PCB substrate (P); Under the action of an AC drive signal, the piezoelectric diaphragm of the chip reciprocates. When the piezoelectric diaphragm (FM) moves downward, it compresses the air in the jet cavity formed by the integrated silicon substrate (S), the piezoelectric diaphragm (FM), and the PCB substrate (P), and ejects the impact heat source from the jet hole (AF). When the piezoelectric diaphragm (FM) moves upward, the jet cavity generates negative pressure and draws in low-temperature ambient air from below.

2. The piezoelectric MEMS synthetic jet cooling chip with integrated jet cavity and silicon substrate according to claim 1, characterized in that, The airflow channel of the jet cavity is a straight inclined surface that tapers towards the PCB substrate (P).

3. The piezoelectric MEMS synthetic jet cooling chip with integrated jet cavity and silicon substrate according to claim 1, characterized in that, The airflow channel of the jet cavity is a streamlined curved surface that tapers towards the PCB substrate (P).

4. The piezoelectric MEMS synthetic jet cooling chip with integrated jet cavity and silicon substrate according to claim 1, characterized in that, The airflow channel of the jet cavity is composed of a multi-level stepped plane that tapers toward the PCB substrate (P).

5. The piezoelectric MEMS synthetic jet cooling chip with integrated jet cavity and silicon substrate according to claim 4, characterized in that, The multi-level stepped plane includes at least three steps.

6. The piezoelectric MEMS synthetic jet cooling chip with integrated jet cavity and silicon substrate according to claim 1, characterized in that, The airflow channel of the jet cavity is formed by a fully enclosed arc-shaped surface that tapers towards the PCB substrate (P). The fully enclosed arc-shaped surface smoothly transitions from the edge of the piezoelectric diaphragm (FM) to the bottom of the integrated silicon substrate (S); and no support structure is provided in the integrated silicon substrate (S).

7. The piezoelectric MEMS synthetic jet cooling chip with integrated jet cavity and silicon substrate according to claim 1, characterized in that, The integrated silicon substrate (S) is integrally formed by bulk silicon micromachining, so that the jet cavity, the airflow channel sidewall (BL) and the main body of the integrated silicon substrate (S) are a single structure without assembly seams.

8. The piezoelectric MEMS synthetic jet cooling chip with integrated jet cavity and silicon substrate according to claim 1, characterized in that, The frequency of the AC drive signal applied to the chip is matched with the resonant frequency of the piezoelectric diaphragm (FM) to generate resonance and maximize the vibration amplitude.

9. The piezoelectric MEMS synthetic jet cooling chip with integrated jet cavity and silicon substrate according to claim 1, characterized in that, The piezoelectric diaphragm (FM) is fixed to the integrated silicon substrate (S) by a narrow-edge bonding structure.

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