Orthogonal ultrasonic precision bonding structure and method for chip-oriented bumps under different phase differences

Abstract

The application discloses a kind of orthogonal ultrasonic precision bonding structures and methods for chip bump under different phase difference, the structure includes orthogonal ultrasonic vibration generation module, it is fixedly installed in the pressure head station of chip bonding equipment just above, inside is equipped with the orthogonal arrangement X axis and Y axis ultrasonic transducer, phase difference precision control unit, amplitude independent adjusting unit and vibration coupling head of conduction.The application is by X-Y double-axis independent controllable ultrasonic vibration, accurately controls double-axis vibration phase difference, and the adjusting range is 0°-90°, wherein 90° is formed elliptical trajectory to realize the uniform shear of bump interface global.Compared with traditional one-way ultrasonic bonding, the application can reduce the standard deviation of equivalent stress distribution by 40%, improve the uniformity of bump height change by 35%, increase the interface contact area by 25%, and increase the shear strength by more than 20%.It can be adapted to 20-100 μm diameter bump, and is suitable for high-density fine-pitch chip thermal ultrasonic bonding process.

Description

Technical Field

[0001] This invention belongs to the field of microelectronic packaging and thermo-ultrasonic bonding technology, and in particular, it is an orthogonal ultrasonic precision bonding structure for chip bumps under different phase differences, which is suitable for advanced packaging processes such as flip bonding and three-dimensional packaging of high-density, fine-pitch chips. Background Technology

[0002] Thermo-ultrasonic bonding is a core process in advanced microelectronic packaging that enables mechanical connection and electrical signal conduction between chip bumps and substrate pads. It utilizes the synergistic effects of temperature, vertical pressure, and ultrasonic shear vibration to break down the oxide film on the metal surface, induce plastic flow in the bump metal, and expand the actual contact area at the interface. Ultimately, a stable metallurgical bond is formed through interatomic diffusion, making it a critical step in advanced packaging processes. Existing thermo-ultrasonic bonding technologies all employ a unidirectional shear ultrasonic vibration structure. While this traditional structure meets basic bonding requirements, it has significant limitations in high-precision, high-reliability advanced packaging applications.

[0003] 1. Unidirectional ultrasonic vibration has a single friction trajectory, and the bonding interface is prone to oxide film removal "dead zone", resulting in insufficient diffusion of interfacial atoms, small actual contact area, and insufficient shear strength and long-term reliability of bonding points;

[0004] 2. Ultrasonic energy is transmitted to the convex interface only in a single direction (such as the X-axis), which can easily lead to uneven distribution of shear stress inside the convex.

[0005] Stress concentration at the local edge of the protrusion can lead to problems such as excessive crushing of the protrusion and initiation of microcracks at the interface.

[0006] 3. Unidirectional ultrasonic vibration is highly sensitive to the surface roughness of the bumps and the flatness of the pads, has a narrow process window, poor bonding consistency during batch bonding, and makes it difficult to improve the yield.

[0007] 4. To compensate for the shortcomings of unidirectional ultrasound, existing technologies require increasing the ultrasonic amplitude or loading pressure, which can easily cause excessive deformation of the bumps and stress damage to the chip substrate, further limiting the bonding quality of microbumps and ultra-fine pitch chips.

[0008] For the reasons mentioned above, the bonding process dominated by unidirectional ultrasonic vibration has limitations in terms of bonding strength and reliability. In existing technologies, some solutions attempt to use bidirectional vibration, but these are mostly synchronous vibrations in the same phase, failing to create an effective elliptical trajectory shearing effect and still unable to achieve uniform deformation across the entire protrusion area; moreover, the lack of precise control over the vibration direction and phase difference makes it difficult to solve the stress concentration problem. Furthermore, the rigid matching of ultrasonic energy input and bonding pressure in traditional processes cannot be dynamically adjusted according to the protrusion deformation state, further exacerbating uneven deformation and interface damage.

[0009] Therefore, developing an orthogonal ultrasonic bonding structure that can achieve uniform shearing across the entire domain, precise phase control, and dynamic parameter matching has become the key to overcoming the current technological bottlenecks. Summary of the Invention

[0010] This invention aims to solve the technical problems of unidirectional vibration stress concentration, uneven bump deformation, and low interface bonding strength in existing chip thermo-ultrasonic bonding. It provides an orthogonal ultrasonic precision bonding structure and method for chip bumps under different phase differences. By loading XY biaxial orthogonal ultrasonic vibration, combined with adaptive pressure and isothermal conditions, uniform shearing of the bump interface is achieved throughout, thereby improving bonding quality and reliability.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] An orthogonal ultrasonic precision bonding structure for chip bumps under different phase differences includes an orthogonal ultrasonic vibration generating module, which is fixedly installed above the pressure head station of the chip bonding equipment to generate and output orthogonally coupled ultrasonic vibrations.

[0013] The orthogonal ultrasonic vibration generating module includes orthogonally arranged X-axis ultrasonic transducers and Y-axis ultrasonic transducers, as well as a phase difference precision control unit, an amplitude independent adjustment unit, and a vibration coupling transmission head; wherein:

[0014] The X-axis ultrasonic transducer and the Y-axis ultrasonic transducer are arranged horizontally orthogonally with their axes perpendicular to each other, and are used to independently generate high-frequency linear ultrasonic vibrations in the X-axis and Y-axis directions, respectively.

[0015] The phase difference precision control unit is connected to the X-axis ultrasonic transducer and the Y-axis ultrasonic transducer respectively, and is used to adjust the phase difference of vibration in the X-axis direction and the Y-axis direction. The phase difference adjustment range is 0°-90°.

[0016] The amplitude independent adjustment unit is connected to the X-axis ultrasonic transducer and the Y-axis ultrasonic transducer respectively, and is used to independently adjust the amplitude of vibration in the X-axis direction and the Y-axis direction respectively;

[0017] The vibration coupling and conduction head is used to couple and conduct vibrations in the X-axis and Y-axis directions to the upper surface of the chip.

[0018] Preferably, the orthogonal ultrasonic vibration generating module is an integrated ultrasonic vibration execution structure, which is rigidly and shockproofly packaged as a whole. The X-axis ultrasonic transducer, Y-axis ultrasonic transducer, phase difference precision control unit, amplitude independent adjustment unit, vibration coupling transmission head and transducer fixing base are all coaxially aligned and assembled in the rigid shockproof package.

[0019] Preferably, the phase difference precision control unit locks the phase difference between the vibrations in the X-axis and Y-axis directions to 90°, so that the vibrations in the X-axis and Y-axis directions are coupled to form a standard circular or elliptical trajectory.

[0020] Preferably, the X-axis ultrasonic transducer and the Y-axis ultrasonic transducer are piezoelectric ceramic ultrasonic transducers made of lead zirconate titanate (PZT-8) and have a working frequency of 20-60kHz.

[0021] Preferably, the amplitude adjustment unit adjusts the vibration amplitude within a range of 0.5-2 μm.

[0022] Preferably, the system also includes a convex interface microstructure, which is an array of micropillars prepared at the bottom of the convex point, wherein the diameter of the micropillars in the array is 5 μm and the height is 2 μm.

[0023] Preferably, the system also includes an adaptive pressure loading module and a thermostatic bonding module. The adaptive pressure loading module is rigidly connected to the orthogonal ultrasonic vibration generating module and is used to apply bonding pressure. The thermostatic bonding module is used to control the bonding temperature at 180°C.

[0024] Preferably, the diameter of the chip bumps is 20-100 μm.

[0025] This invention also provides a bonding method for orthogonal ultrasonic precision bonding structures facing chip bumps under different phase differences, comprising the following steps:

[0026] (1) Place the chip to be bonded under the vibration coupling transmission head, and align the chip bumps with the substrate pads;

[0027] (2) The phase difference between the vibrations generated by the X-axis ultrasonic transducer and the Y-axis ultrasonic transducer can be adjusted within the range of 0°-90° by using the phase difference precision control unit;

[0028] (3) Start the X-axis ultrasonic transducer and the Y-axis ultrasonic transducer to generate ultrasonic vibrations in the X-axis and Y-axis directions respectively, and adjust the amplitude in each direction to 0.5-2μm through the amplitude independent adjustment unit;

[0029] (4) The ultrasonic vibrations in the X-axis and Y-axis directions are coupled through the vibration coupling transmission head and transmitted to the upper surface of the chip, driving the chip bumps and the substrate pads to form an elliptical trajectory relative motion, thereby achieving bonding.

[0030] Preferably, in step (3), the operating frequency of the X-axis ultrasonic transducer and the Y-axis ultrasonic transducer is 20-60kHz.

[0031] Preferably, in step (4), bonding pressure is applied through an adaptive pressure loading module during the bonding process, and the bonding temperature is controlled at 180°C through a constant temperature bonding module.

[0032] Beneficial effects: Compared with traditional unidirectional ultrasonic bonding, the orthogonal ultrasonic bonding of this invention has the following significant advantages:

[0033] (1) Stress uniformity: The standard deviation of the equivalent stress distribution at the convex interface is reduced by 40%, with no obvious stress concentration area. This advantage stems from the core innovation of this invention—XY biaxial orthogonal ultrasonic vibration loading. By using an orthogonal ultrasonic vibration scheme based on a 90° phase difference, an elliptical trajectory shearing effect is formed, achieving uniform stress distribution across the entire convex interface, thus fundamentally solving the stress concentration problem of traditional unidirectional vibration.

[0034] (2) Deformation uniformity: The uniformity of the bump height change is improved by 35%, avoiding local crushing or insufficient deformation. Orthogonal shearing action causes uniform plastic flow of the bump material, ensuring deformation uniformity and providing a guarantee for high-quality bonding.

[0035] (3) Bonding strength: The actual contact area of ​​the interface increases by 25%, the shear strength increases by more than 20%, and the reliability is significantly improved. This effect is due to the synergistic effect of interface strengthening and orthogonal vibration—combining the convex micro-nano structure layer with orthogonal shearing, the oxide layer fragmentation and mechanical interlocking are strengthened, significantly improving the interface contact area and atomic diffusion efficiency, and further enhancing the bonding strength and reliability.

[0036] (4) Process adaptability: It can be adapted to bumps with diameters of 20-100μm, and is suitable for high-density fine-pitch packaging scenarios. By designing an independent phase difference control unit, the X / Y axis vibration phase difference (0-90°) can be precisely adjusted to adapt to different bump sizes and material systems, and to achieve customized optimization of shearing action.

[0037] In summary, this invention constructs a highly reliable and consistent chip orthogonal ultrasonic bonding structure through global uniform shear loading of orthogonal ultrasonic vibration, combined with precise phase modulation and closed-loop parameter matching. Compared with existing unidirectional ultrasonic bonding technology, this invention has significant improvements in stress uniformity, deformation consistency, bonding strength, and process adaptability, making it suitable for next-generation high-density microelectronic packaging processes and possessing significant engineering application value. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the overall orthogonal ultrasonic bonding structure of the present invention. Among them, (a) is an orthogonal ultrasonic bonding structure with ultrasonic vibration applied to the X component, (b) is an orthogonal ultrasonic bonding structure with ultrasonic vibration applied to the Y component (represented as the Z component in the simulation), and (c) is a schematic diagram of the substrate, electrodes, bumps, laser and tooling in the model.

[0039] Figure 2 The figures show the stress variation curves of the XY biaxial orthogonal elliptical vibration and orthogonal circular vibration of this invention. Among them, (a) is the equivalent stress variation curve of orthogonal circular vibration, in which the vibration amplitude of both X and Y components is 2μm and the frequency is 60kHz; (b) is the equivalent stress variation curve of orthogonal elliptical vibration, in which the vibration amplitude of X component is 2μm and the vibration amplitude of Y component is 1μm, and the frequency of both is 60kHz.

[0040] Figure 3 This is a flowchart of a chip orthogonal ultrasonic flip bonding method according to an embodiment of the present invention.

[0041] Figure 4 The figures show the convex deformation and overall stress under a 90° phase difference (without added downward pressure, the model's own weight is used as a substitute). (a) shows the convex stress contour plot with a 90° phase difference, (b) shows the overall stress contour plot, and (c) shows the overall deformation contour plot. Throughout the simulation, the amplitude remained at 2 μm, and the frequency was 60 kHz. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0043] Example 1: Orthogonal ultrasonic bonding structure

[0044] like Figure 1 As shown, this embodiment provides an orthogonal ultrasonic precision bonding structure for chip bumps under different phase differences. Figure 1 A simulation demonstration of a single-bump flip-chip bond 3D finite element model built using ANSYS software is shown. The model consists of five parts: substrate, electrode, bump, laser, and tooling. Figure 1In model (c), the substrate and laser are both square with side lengths of 200µm and 60µm, respectively, and a height of 100µm. The gold electrode has a side length of 100µm and a height of 0.3µm. The indium pillar has a diameter of 30µm and a height of 6µm. The tooling has a side length of 60µm and a height of 10µm. In this invention, the substrate is made of silicon (Si) to ensure substrate rigidity, the chip bumps are made of indium (In), and the electrodes are made of gold (Au) to achieve efficient plastic deformation and metallurgical bonding. The pressure head tooling is made of structural steel to accurately transmit vertical pressure. The selection of each material is matched to the mechanical and process characteristics of high-density fine-pitch packaging. The global basic mesh unit size is set to 5µm. Local mesh refinement is performed on the bump and bonding interface areas, with the minimum unit size set to 1µm. The bottom of the substrate is constrained by the boundary. The tooling applies constant pressure and 60kHz ultrasonic vibration. The interface stress and deformation are analyzed under multi-phase difference conditions. In addition, the laser described in this invention is used in actual processes to perform localized and precise heating and state monitoring of the bonding interface, assisting in achieving low-temperature and high-efficiency bonding; in simulation, it is simplified into a surface heat source model to construct a multi-physics coupling environment for analyzing the influence of different phase differences on the mechanical and metallurgical bonding properties of the bonding interface under laser assistance. Among them, (a) is an orthogonal ultrasonic bonding structure with ultrasonic vibration applied to the X component, (b) is an orthogonal ultrasonic bonding structure with ultrasonic vibration applied to the Y component (represented as the Z component in the simulation), and (c) is a schematic diagram of the substrate, electrode, bump, laser and tooling in the model.

[0045] The orthogonal ultrasonic vibration generation module is an integrated ultrasonic vibration execution structure, rigidly and shockproofly packaged and fixedly mounted above the pressure head of the chip bonding equipment. It generates and outputs orthogonally coupled ultrasonic vibrations. Internally, the module includes orthogonally arranged X-axis and Y-axis ultrasonic transducers, a phase difference precision control unit, an amplitude independent adjustment unit, a vibration coupling transmission head, and a transducer mounting base. The X-axis ultrasonic transducer, Y-axis ultrasonic transducer, phase difference precision control unit, amplitude independent adjustment unit, vibration coupling transmission head, and transducer mounting base are all coaxially aligned and assembled within the rigid, shockproof package, with no vibration offset gaps.

[0046] The X-axis and Y-axis ultrasonic transducers are piezoelectric ceramic ultrasonic transducers made of lead zirconate titanate (PZT-8), characterized by high electromechanical conversion efficiency, strong vibration stability, fast high-frequency response, and no hysteresis drift. The two transducers are arranged horizontally and orthogonally, with the X-axis transducer positioned laterally along the chip and the Y-axis transducer longitudinally along the chip. Their axes are perpendicular and do not interfere with each other, independently generating high-frequency linear ultrasonic vibrations in the X-axis and Y-axis directions, respectively. The vibration direction is strictly parallel to the upper surface of the chip, without generating any additional vertical force. The transducer's rear end connects to the device's ultrasonic power supply, and the front end connects to the amplitude adjustment unit via an elastic connector. The vibration amplitude is controllable within a range of 0.5-2 μm, and the operating frequency is 20-60 kHz.

[0047] The phase difference precision control unit is connected to both the X-axis and Y-axis ultrasonic transducers, and incorporates a high-precision signal phase-shifting circuit and clock synchronization module to adjust the phase difference between the X-axis and Y-axis vibrations, with an adjustment range of 0°-90°. The independent amplitude adjustment unit is also connected to both the X-axis and Y-axis ultrasonic transducers, allowing for independent adjustment of the vibration amplitude in each direction, supporting continuous and gradual amplitude changes throughout the bonding process. The vibration coupling and conduction head couples the X-axis and Y-axis vibrations and conducts them uniformly and vertically to the chip's upper surface, fully covering the area of ​​the bumps to be bonded.

[0048] A bump interface microstructure is fabricated at the bottom of the chip bumps. This microstructure is an array of micropillars fabricated at the bottom of the bumps, with each micropillar having a diameter of 5 μm and a height of 2 μm. A thermostatic bonding module is installed at the bottom of the substrate to control the bonding temperature at 180℃. An adaptive pressure loading module is integrated within the pressure head fixture and rigidly docked with the orthogonal ultrasonic vibration generation module to apply bonding pressure. This adaptive pressure loading module uses a multilayer piezoelectric ceramic drive and PID closed-loop control to achieve precise pressure adjustment, loading in three stages: "pre-contact - main deformation - curing": initial stable bonding, mid-stage coordinated deformation, and late-stage micro-pressure holding curing. A vertical guide structure avoids off-center loading, with a sampling accuracy of 0.01 MPa, ensuring uniform and stable pressure. The diameter of the chip bumps is 20-100 μm, suitable for high-density, fine-pitch packaging scenarios.

[0049] Example 2: Comparison of bonding effects under different phase differences

[0050] This embodiment uses the structure described in Embodiment 1 for bonding experiments. The ultrasonic frequency is uniformly set to 60kHz, and the uniaxial amplitude is set to 2μm. By changing the phase difference of the biaxial vibration through the phase difference precise control unit, different vibration trajectories and shearing effects can be formed. Specifically, the following four core scenarios are analyzed:

[0051] (1) Phase difference 0° (synchronous vibration in the same phase)

[0052] The X-axis and Y-axis vibrations start and fall synchronously. After the dual-axis vibrations are superimposed, they result in unidirectional linear vibration along a 45° diagonal line. Essentially, it is an optimized version of unidirectional vibration and lacks a global shearing effect. In this mode, the stress at the convex interface is still concentrated in the edge area, and the oxide layer is unevenly broken. It can only slightly improve the deformation consistency and cannot solve the core stress concentration problem. The bonding effect is not significantly different from that of traditional unidirectional vibration.

[0053] (2) Phase difference 45° (non-orthogonal oblique vibration)

[0054] The X-axis and Y-axis vibrations have a 45° phase difference, which, when superimposed, forms a narrow elliptical vibration trajectory, with the shear range covering a local area of ​​the protrusion. Compared to a 0° phase difference, the stress concentration is somewhat alleviated, and the oxide layer fragmentation efficiency is slightly improved. However, there is still a significant problem of uneven stress distribution, with a large difference in deformation between the edge and center of the protrusion, resulting in poor consistency in bonding strength. This method is only suitable for simple bonding scenarios with low precision and non-dense protrusions.

[0055] (3) Phase difference 90° (standard orthogonal elliptical vibration)

[0056] The X-axis and Y-axis vibration phase difference is precisely locked at 90°. After the dual-axis vibration is superimposed, a standard circular / elliptical trajectory is formed. The shearing action covers the entire interface of the protrusion, achieving uniform shearing across the entire area. Figure 2 The figures show the stress variation curves of the XY biaxial orthogonal elliptical vibration and orthogonal circular vibration of this invention. Among them, (a) is the equivalent stress variation curve of orthogonal circular vibration, in which the vibration amplitude of both the X and Z components is 2μm and the frequency is 60kHz; (b) is the equivalent stress variation curve of orthogonal elliptical vibration, in which the vibration amplitude of the X component is 2μm and the vibration amplitude of the Z component is 1μm, and the frequency of both is 60kHz.

[0057] Figure 3 This is a flowchart illustrating a method for orthogonal ultrasonic flip bonding of a chip according to an embodiment of the present invention. Figure 3 As shown, the method includes the following steps:

[0058] (1) Place the chip to be bonded under the vibration coupling transmission head, and align the chip bumps with the substrate pads;

[0059] (2) The phase difference between the vibrations generated by the X-axis ultrasonic transducer and the Y-axis ultrasonic transducer can be adjusted within the range of 0°-90° by using the phase difference precision control unit;

[0060] (3) Start the X-axis ultrasonic transducer and the Y-axis ultrasonic transducer to generate ultrasonic vibrations in the X-axis and Y-axis directions respectively, and adjust the amplitude in each direction to 0.5-2μm through the amplitude independent adjustment unit;

[0061] (4) The ultrasonic vibrations in the X-axis and Y-axis directions are coupled through the vibration coupling transmission head and transmitted to the upper surface of the chip, driving the chip bumps and the substrate pads to form an elliptical trajectory relative motion, thereby achieving bonding.

[0062] Figure 4 The figures show the convex deformation and overall stress under a 90° phase difference (without added downward pressure, the model's own weight is used as a substitute). (a) shows the convex stress contour plot with a 90° phase difference, (b) shows the overall stress contour plot, and (c) shows the overall deformation contour plot. Throughout the simulation, the amplitude remained at 2 μm, and the frequency was 60 kHz.

[0063] In this mode, the standard deviation of the equivalent stress distribution inside the bump is reduced by 40%, there is no obvious stress concentration peak, the oxide layer is uniformly broken throughout, the interface contact area is increased by 25%, the bump deformation uniformity is increased by more than 30%, the bonding strength and reliability are optimal, and it is suitable for high-precision bonding of various high-density, fine-pitch chips and MEMS devices.

[0064] (4) Phase difference 135° / 180° (anti-phase, reverse vibration)

[0065] At a 180° phase difference, the X and Y axes vibrate in completely opposite directions. When superimposed, the vibrations cancel each other out, resulting in a significant attenuation of effective shear energy, insufficient plastic deformation of the bumps, and extremely low interfacial bonding strength. At a 135° phase difference, an irregular elliptical trajectory is formed, the shear force direction is disordered, easily causing bump distortion and deformation, microcracks at the interface, and even bump breakage, leading to a significant decrease in bonding success rate. This type of phase difference mode has no practical value and is only used for comparative analysis.

[0066] In summary, the phase difference of XY biaxial ultrasonic vibration directly determines the vibration trajectory, stress distribution, and bonding effect. A 90° standard orthogonal phase difference is the optimal solution, which can achieve uniform shearing across the entire domain and avoid energy cancellation and stress concentration, perfectly meeting the bonding requirements of high-end microelectronic packaging.

[0067] Example 3: Optimization of bonding process parameters and interface strengthening

[0068] This embodiment, based on the preferred scheme of 90° phase difference, further verifies the convex interface bonding process and interface strengthening effect.

[0069] like Figure 1As shown, a micropillar array structure (micropillar diameter 5μm, height 2μm) is fabricated at the bottom of the chip bumps. A temperature compensation unit at the bottom of the substrate controls the bonding temperature to 180℃. The temperature compensation unit uses a flexible thin-film heating element and a high-precision NTC thermistor, achieving precise temperature control of 180℃±1℃ through PID closed-loop control with a response time ≤100ms. It can dynamically compensate for ultrasonic friction temperature rise, avoiding interface thermal damage and embrittlement, while softening the In bumps to assist in plastic deformation, adapting to the requirements of low-temperature, low-damage, high-density fine-pitch bonding. During the bonding process:

[0070] (1) The orthogonal elliptical shearing motion causes the oxide layer on the surface of the bump and the pad to be uniformly broken throughout the entire area. The micro-pillar array further improves the breaking efficiency, forms a mechanical interlock, and increases the actual contact area.

[0071] (2) The synergistic effect of ultrasonic frictional heating and constant temperature heating reduces the yield strength of the protrusion material, promotes the diffusion of interfacial atoms, and provides conditions for metallurgical bonding.

[0072] (3) Compared with unidirectional vibration, orthogonal vibration allows the reduction rate of convex height to be precisely controlled within the optimal range of 20%-30%, and the deformation uniformity is improved by more than 30%, without local crushing or insufficient deformation problems.

[0073] Compared with traditional unidirectional ultrasonic bonding, the orthogonal ultrasonic bonding of this invention has the following significant advantages:

[0074] Stress uniformity is characterized by a 40% reduction in the standard deviation of the equivalent stress distribution at the convex interface, with no obvious stress concentration areas.

[0075] The deformation consistency is reflected in the 35% improvement in the uniformity of the convex height change, avoiding local crushing or insufficient deformation.

[0076] The bonding strength is reflected in a 25% increase in the actual contact area at the interface, a more than 20% increase in shear strength, and a significant improvement in reliability.

[0077] Its process adaptability is demonstrated by its ability to accommodate bumps with diameters of 20-100μm, making it suitable for high-density, fine-pitch packaging scenarios.

[0078] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An orthogonal ultrasonic precision bonding structure for chip bumps under different phase differences, characterized in that: It includes an orthogonal ultrasonic vibration generating module, which is fixedly installed above the pressure head station of the chip bonding equipment to generate and output orthogonally coupled ultrasonic vibrations; The orthogonal ultrasonic vibration generating module includes orthogonally arranged X-axis ultrasonic transducers and Y-axis ultrasonic transducers, as well as a phase difference precision control unit, an amplitude independent adjustment unit, and a vibration coupling transmission head; wherein: The X-axis ultrasonic transducer and the Y-axis ultrasonic transducer are arranged horizontally orthogonally with their axes perpendicular to each other, and are used to independently generate high-frequency linear ultrasonic vibrations in the X-axis and Y-axis directions, respectively. The phase difference precision control unit is connected to the X-axis ultrasonic transducer and the Y-axis ultrasonic transducer respectively, and is used to adjust the phase difference of vibration in the X-axis direction and the Y-axis direction. The phase difference adjustment range is 0°-90°. The amplitude independent adjustment unit is connected to the X-axis ultrasonic transducer and the Y-axis ultrasonic transducer respectively, and is used to independently adjust the amplitude of vibration in the X-axis direction and the Y-axis direction respectively; The vibration coupling and conduction head is used to couple and conduct vibrations in the X-axis and Y-axis directions to the upper surface of the chip.

2. The orthogonal ultrasonic precision bonding structure for chip bumps under different phase differences according to claim 1, characterized in that: The orthogonal ultrasonic vibration generating module is an integrated ultrasonic vibration execution structure with a rigid shockproof enclosure. The X-axis ultrasonic transducer, Y-axis ultrasonic transducer, phase difference precision control unit, amplitude independent adjustment unit, vibration coupling transmission head and transducer fixing base are all coaxially aligned and assembled in the rigid shockproof enclosure.

3. The orthogonal ultrasonic precision bonding structure for chip bumps under different phase differences according to claim 1, characterized in that: The phase difference precision control unit locks the phase difference between the vibrations in the X-axis and Y-axis directions to 90°, so that the vibrations in the X-axis and Y-axis directions are coupled to form a standard circular or elliptical trajectory.

4. The orthogonal ultrasonic precision bonding structure for chip bumps under different phase differences according to claim 1, characterized in that: The X-axis and Y-axis ultrasonic transducers are piezoelectric ceramic ultrasonic transducers made of lead zirconate titanate and operating at a frequency of 20-60kHz. The amplitude independent adjustment unit adjusts the vibration amplitude within a range of 0.5-2μm.

5. The orthogonal ultrasonic precision bonding structure for chip bumps under different phase differences according to claim 1, characterized in that: It also includes a convex interface microstructure, which is a micropillar array prepared at the bottom of the convex point, wherein the micropillars in the micropillar array have a diameter of 5μm and a height of 2μm.

6. The orthogonal ultrasonic precision bonding structure for chip bumps under different phase differences according to claim 1, characterized in that: It also includes an adaptive pressure loading module and a thermostatic bonding module. The adaptive pressure loading module is rigidly connected to the orthogonal ultrasonic vibration generating module and is used to apply bonding pressure. The thermostatic bonding module is used to control the bonding temperature at 180°C.

7. The orthogonal ultrasonic precision bonding structure for chip bumps under different phase differences according to claim 1, characterized in that: The diameter of the chip bumps is 20-100μm.

8. A bonding method using the orthogonal ultrasonic precision bonding structure for chip bumps under different phase differences as described in any one of claims 1-7, characterized in that: Includes the following steps: (1) Place the chip to be bonded under the vibration coupling transmission head, and align the chip bumps with the substrate pads; (2) The phase difference between the vibrations generated by the X-axis ultrasonic transducer and the Y-axis ultrasonic transducer can be adjusted within the range of 0°-90° by using the phase difference precision control unit; (3) Start the X-axis ultrasonic transducer and the Y-axis ultrasonic transducer to generate ultrasonic vibrations in the X-axis and Y-axis directions respectively, and adjust the amplitude in each direction to 0.5-2μm through the amplitude independent adjustment unit; (4) The ultrasonic vibrations in the X-axis and Y-axis directions are coupled through the vibration coupling transmission head and transmitted to the upper surface of the chip, driving the chip bumps and the substrate pads to form an elliptical trajectory relative motion, thereby achieving bonding.

9. The bonding method according to claim 8, characterized in that, In step (3), the operating frequency of the X-axis ultrasonic transducer and the Y-axis ultrasonic transducer is 20-60kHz.

10. The bonding method according to claim 8, characterized in that, In step (4), bonding pressure is applied through the adaptive pressure loading module during the bonding process, and the bonding temperature is controlled at 180°C through the constant temperature bonding module.

Images