Apparatus and method for fabricating microelectronic interconnect lines and bumps based on pulsed micro-hole jetting

Abstract

This invention provides an apparatus and method for fabricating microelectronic interconnects and bumps based on pulsed micro-orifice jetting. The apparatus includes a droplet jetting system with at least one set of jetting units disposed above the interior of a cavity. The micro-orifices at the bottom of each jetting unit are tapered, with an angle of 20° to 70°. A liquid level control system replenishes the liquid level lost during melt jetting via a liquid level adjuster, maintaining a stable overall liquid level. A three-dimensional motion system is located at the bottom of the cavity, on which electronic devices or substrates move according to a preset path, receiving the jetted droplets to fabricate bumps or achieve electronic interconnects. This invention offers good process controllability and flexibility, producing stable, uniform, and size-controllable jetted droplets, easily enabling efficient printing and customization of microelectronic interconnects and bumps.

Description

Technical Field

[0001] This invention relates to the field of electronic packaging technology, and more particularly to an apparatus and method for preparing microelectronic interconnects and bumps based on pulsed micro-orifice jetting in technologies such as direct forming of ball grid array bumps, direct printing of solder column arrays, and microcircuit printing. Background Technology

[0002] With the rapid development of the electronics industry, electronic circuits are becoming increasingly large-scale, miniaturized, and multifunctional. Electronic interconnection paths are constantly evolving towards shorter distances, higher densities, and greater personalization, posing a severe challenge to traditional packaging and soldering processes. To adapt to the development trend of electronic products, different types of packaging methods have emerged.

[0003] Ball Grid Array (BGA) packaging is a surface mount technology that achieves interconnection by fabricating a bump array on a PCB substrate. It has advantages such as short lead paths, high package density, and more pins in the same area.

[0004] Bump formation, a core step in BGA packaging, typically employs methods such as vacuum balling, stencil printing, evaporation deposition, and electroplating. Vacuum balling uses a vacuum chuck to pick up solder balls and place them on the corresponding positions on the pads. The vacuum is then stopped, allowing the solder balls to fall to their designated positions. However, this method is prone to solder ball loss and adhesion, and each batch of ball placement requires a replacement chuck compatible with the substrate, significantly increasing costs. Stencil printing uses a brush and stencil to apply solder to the pads. This method produces bumps with limited size and uneven solder distribution. Evaporation deposition heats the solder to a gaseous state and then deposits it onto a metal mask or photolithography mold to form bumps. Electroplating electroplats the solder onto photoresist-coated pads to form bumps, but photolithography and electroplating, being chemical methods, can pollute the environment, and electroplating makes it difficult to achieve uniform bump height.

[0005] The above process flow is usually divided into multiple steps such as ball making, screen printing (or dispensing), ball placement, reflow soldering, and cleaning. Some preparation methods also require specific fixtures to match the PCB substrate, which greatly increases the production time and cost of products with small batch and special array requirements.

[0006] Besides bump arrays, some 3D chip packaging also requires the fabrication of pillar arrays. Column Grid Array (CGA) is similar to BGA, but replaces the solder balls of BGA with slender pillars. These pillars are soldered onto the substrate pads at specific longitudinal and transverse spacing to form a neat array. The pillars are the key components of CGA devices, ensuring not only electrical continuity but also mechanical connections. The fabrication process involves multiple steps. Typically, the cast pillars are first fixed to the ceramic substrate using high-temperature soldering, and then soldered onto the PCB board using solder paste to complete the mechanical and electrical connections.

[0007] In the production and fabrication of personalized electronic circuits, it is necessary to rapidly print flexible circuits and quickly braze electronic circuits or devices to achieve electrical interconnection. For example, the connection between flexible gold fingers and external wires is usually done manually, which is labor-intensive and results in low brazing quality.

[0008] Traditional packaging technology typically requires the preparation of solder balls, the formation of solder joints and solder pillars, and the printing of wires to be carried out step by step on different equipment. Moreover, specific equipment can only prepare bumps or print wires of a single size, which can only achieve quantity on demand, but cannot simultaneously achieve size and form on demand, making it difficult to meet the personalized needs of microcircuits.

[0009] Pulsed micro-orifice jet deposition technology refers to a process where, under the influence of the melt's own weight, the vibration of a piezoelectric ceramic drives a transmission rod to locally disturb the melt near the micro-orifice, causing the melt at the micro-orifice to overcome surface tension and eject a certain amount of droplets. This, combined with a three-dimensional motion platform, enables various forms of microelectronic interconnection. Application No. 201110240940.4, entitled "A Laser Ball Placement System," discloses a laser ball placement system that saves some steps compared to traditional processes and can efficiently repair points. However, this method uses a spring-loaded ball, which is prone to problems such as excessive ball quantity causing jamming or insufficient balls, requiring adjustment with a knob. It also suffers from low ball placement efficiency, high laser energy that can easily burn the substrate, and difficulty in preparing small-diameter bumps. If batch preparation of interconnect bumps is required, the efficiency of this method is greatly limited. In existing technologies, only single-size solder balls can be interconnected at a time, and it is impossible to combine bump formation and microcircuit printing in the same equipment. Furthermore, the stability and controllability of droplet jetting are crucial for direct microelectronic interconnection and bump preparation.

[0010] Therefore, it is necessary to provide a device and method that can adapt to the current development of electronic products and to solve the problems mentioned above in the process of microelectronic interconnection. Summary of the Invention

[0011] To address the aforementioned technical problems in microelectronic interconnection processes, such as low ball-mounting efficiency and limited printing methods, this invention provides an apparatus and method for fabricating microelectronic interconnects and bumps based on pulsed micro-orifice jetting. The apparatus involves placing the materials required for electronic interconnection in a crucible and heating them to a molten state. By adjusting the mass of the added metal and coordinating with a liquid level regulator, the molten metal at the nozzle reaches a suitable pressure range. Simultaneously, a piezoelectric ceramic actuator applies a specific pulse waveform to the piezoelectric ceramic, causing a small displacement of the transmission rod. This creates a regular, localized disturbance in the molten metal at the bottom of the crucible, causing the liquid at the micro-orifice to overcome surface tension and flow out to form microdroplets. Each pulse forms one microdroplet. By switching the transmission rod to the vicinity of nozzles of different sizes as needed, a large range of sizes (25-800 μm) can be controlled simultaneously. Furthermore, improvements to the structure and materials at the micro-orifice enhance the stability of the microdroplet jetting. During the droplet descent, a three-dimensional platform moves along a pre-set path, allowing the droplets to be jetted onto the platform for bump fabrication, pillar array printing, and microcircuit printing.

[0012] The technical means employed in this invention are as follows:

[0013] An apparatus for fabricating microelectronic interconnects and bumps based on pulsed micro-orifice jetting method, comprising:

[0014] The droplet ejection system has at least one set of ejection units inside the cavity. One side of the cavity is provided with an observation window for observing the stability of particle ejection, and the other side is provided with a pre-collection disk. The micro-holes at the bottom of the ejection unit for ejection are designed in a conical shape of 20° to 70°.

[0015] The liquid level control system replenishes the liquid level that is reduced by the melt injection through the liquid level adjuster, so as to keep the overall liquid level stable.

[0016] A three-dimensional motion system is provided at the bottom of the cavity, where electronic devices or substrates move on their motion platform according to a preset path within the cavity, receiving the ejected droplets to achieve bump fabrication or electronic interconnection.

[0017] Furthermore, the droplet ejection system includes a crucible and a lifting platform connected to a piezoelectric ceramic actuator located above the crucible, a piezoelectric ceramic and a transmission rod connected below the lifting platform and extending into the crucible. A connecting sleeve is fitted around the outside of the crucible, and the connecting sleeve has at least two grooves for accommodating microporous sheets. A heater for heating and melting metal is provided outside the connecting sleeve. The piezoelectric ceramic is driven according to a set pulse waveform, and the piezoelectric ceramic drives the transmission rod to generate displacement, producing regular local disturbances near the micropores on the microporous sheets, causing the melt to overcome surface tension and eject from the micropores.

[0018] Furthermore, the upper surface of the microporous sheet is provided with a layer of wettable material that does not react with the molten metal to be sprayed, and 0.1-2 mm of non-wetting material is retained at the microporous nozzle of the microporous sheet.

[0019] Furthermore, the pre-collection tray is placed below the crucible, and the pre-collection tray is removed after the droplet spray has stabilized to proceed with the deposition process.

[0020] Furthermore, each groove of the connecting sleeve is provided with a microporous sheet of different aperture. The rotation of the transmission rod is achieved by a rotary dynamic seal above the cavity. The transmission rod rotates to a position corresponding to the micropores of different apertures, and the displacement disturbance of the melt is generated in conjunction with the injection parameters to achieve the injection of droplets of various sizes.

[0021] Furthermore, a crucible-cavity communication pipe is provided between the crucible and the cavity to prevent different gas pressures due to temperature differences.

[0022] Furthermore, the liquid level can be adjusted according to the particle size requirements to facilitate the fabrication of particles or bumps of different sizes and the printing of microcircuits. The critical pressure required for the droplets to overcome surface tension is P. 临 It can be expressed by equation (1):

[0023]

[0024] Where γ is the surface tension, θ is the wetting angle between the droplet and the microporous sheet, d is the diameter of the micropore, and the liquid itself has a certain weight, generating pressure P. 自 It can be expressed by equation (2):

[0025] P 自 =ρgh (2)

[0026] ρ is the solder density, and h is the height of the liquid surface formed by the molten metal after melting. When P 临 Greater than P 自 Then, by combining piezoelectric ceramics and a transmission rod, regular disturbances are applied to the micropores to overcome the surface tension of the melt at the micropores, thus achieving spraying.

[0027] Furthermore, the pore size of the micropores ranges from 25 to 800 μm, and the vibration frequency of the piezoelectric ceramic is between 0.1 and 1000 Hz.

[0028] Furthermore, the crucible contains a molten material, and a thermocouple is placed in the molten material to provide real-time temperature feedback to a temperature controller, thereby controlling the metal temperature; the temperature controller is connected to a heating plate on the motion platform to achieve the required deposition temperature.

[0029] This invention also discloses a method for preparing microelectronic interconnects and bumps based on pulsed micro-orifice jetting. Using the aforementioned apparatus, the required interconnect path is set by a computer program, causing the motion platform to move along the set path. The molten metal in the crucible is heated to a molten state by a heater. Different liquid level heights are set according to the pore size and material of the microporous sheet to maintain a suitable pressure at the nozzle. A certain pulse waveform is applied to the piezoelectric ceramic actuator to drive the piezoelectric ceramic to vibrate, which in turn drives the transmission rod to produce a small displacement, acting on the local melt at the bottom of the crucible. Each pulse can form a quantitative droplet at the small hole, which is stably and uniformly ejected.

[0030] Furthermore, the method includes the following steps:

[0031] S1. Set the motion path of the motion platform to match the frequency of the pulse waveform and the injection distance according to the required micro-interconnection requirements;

[0032] S2. Place the materials required for interconnection into a crucible, place the microporous sheet at the bottom of the connecting sleeve, and place a heater on the outside;

[0033] S3. Evacuate the crucible and cavity using a vacuum pump, open the chamber gas distribution valve to fill with protective gas, and bring the cavity into a slightly positive pressure state.

[0034] S4. According to the interconnection type and size requirements, rotate the drive rod to the position corresponding to the micro-hole to be sprayed and lower it to the micro-hole. Set the corresponding pulse waveform and apply it to the piezoelectric ceramic driver to drive the piezoelectric ceramic and drive the drive rod to produce a small displacement, generating regular local disturbance near the micro-hole so that the melt overcomes the surface tension and is sprayed out from the micro-hole.

[0035] S5. First, use a pre-collection disk to collect the particles. When the droplet spray is stable and the accuracy is guaranteed, pull back the pre-collection disk so that the microdroplets are sprayed to the required position for substrate interconnection to achieve the purpose of electronic interconnection.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] The device of this invention produces microdroplets with uniform particle size, good controllability, and high precision. Moreover, the preparation process does not involve high energy or high temperature, so it will not damage some temperature-sensitive substrates and components. It can accurately print bumps, not only to realize the direct preparation of BGA solder joints, but also to realize the pin-point printing of MEMS devices, such as the internal corner three-dimensional interconnection of disk drive read / write heads. It can stabilize pillars, which can be used for the direct printing of CGA solder joints. It can stabilize wire fabrication, which can be used for the rapid printing of electronic circuits and the rapid interconnection of electronic circuits or devices. In a single experiment, different sizes of bumps and electronic circuits of different thicknesses can be printed as needed, which can well adapt to the personalized development needs of microcircuits and realize the "tailor-made" microcircuits.

[0038] This invention enables precise control of droplet size across a wide range, from 25 to 800 μm, by switching the drive rod to the vicinity of nozzles of different sizes as needed. Furthermore, the droplet size can be controlled through the synergistic effect of process parameters such as the rise time of the pulse waveform, voltage, the distance from the bottom of the drive rod to the micro-orifice (rod spacing), and orifice diameter. This allows for not only on-demand spraying in quantity and position but also on-demand spraying in size and form, enabling the simultaneous implementation of multiple micro-interconnection methods.

[0039] The stability of the jetting at the nozzle of the device of the present invention is an important prerequisite for ensuring direct microelectronic interconnection. Improving the structure and materials at the micropores can help improve the stability of the microdroplet jetting. Furthermore, it can be combined with the constraint of the wetting material on the micropore sheet to effectively suppress the shrinkage and expansion of the melt at the micropores, thereby increasing its stability.

[0040] In summary, the apparatus and method provided by this invention have advantages such as high flexibility and good controllability, simplified process flow, and significant savings in equipment and time costs. The sprayed microdroplets have uniform particle size and consistent thermal history, and the deposited interconnect bumps have consistent structure and stable performance. By reasonably matching the process parameters of the pulsed micro-orifice spraying method with the motion path of the three-dimensional platform, multiple interconnects can be achieved using the same apparatus, such as microcircuit printing, bump interconnects used in ball grid arrays, and column array printing, etc., which have advantages such as high flexibility and good controllability, simplified process flow, and significant savings in equipment and time costs.

[0041] Based on the above reasons, this invention can be widely promoted in the field of microelectronics. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a schematic diagram of the structure of the device of the present invention.

[0044] Figure 2 This is a schematic diagram of the bottom connecting sleeve of the crucible of the present invention, which is symmetrically equipped with four different sizes of microporous sheets.

[0045] Figure 3 The diagram shows the melt near the microporous sheet of the present invention. (1) and (2) show the problems existing in the current simulation of melt spraying. (3) and (4) are schematic diagrams of structural and material improvements for it.

[0046] Figure 4The image shows the surface morphology of the particles obtained in this invention, wherein the particle size is 63.8 μm.

[0047] Figure 5 The image shows the surface morphology of the particles obtained in this invention, wherein the particle size is 149.7 μm.

[0048] Figure 6 The image shows the surface morphology of the particles obtained in this invention, wherein the particle size is 190.2 μm.

[0049] Figure 7 The image shows the surface morphology of the particles obtained in this invention, wherein the particle size is 247.4 μm.

[0050] Figure 8 The image shows the surface morphology of the particles obtained in this invention, wherein the particle size is 296.8 μm.

[0051] In the diagram: 1. Lifting platform; 2. Piezoelectric ceramic; 3. Piezoelectric ceramic cooling chamber; 4. Transmission rod; 5 (5') Heater; 6 (6') Crucible; 7. Connecting sleeve; 8. Microporous sheet; 9 (9') Liquid level adjuster; 10. Temperature controller; 11. Computer; 12. Motion platform; 13. Insulated water cooling plate; 14. Heating plate; 15. Substrate; 16. Cavity connecting water valve; 17. Pre-collection tray; 18. Crucible cavity connecting pipe; 19. Cavity gas distribution valve; 20. Protective gas; 21. Piezoelectric ceramic actuator; 22. Vacuum pump; 23. Cavity; 24. Observation window. Detailed Implementation

[0052] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. 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.

[0054] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0055] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0056] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms 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 on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0057] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0058] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0059] like Figure 1 As shown, this invention provides an apparatus for fabricating microelectronic interconnects and bumps based on a pulsed micro-orifice jetting method. The apparatus includes a droplet jetting system. At least one set of jetting units is arranged above the interior of a cavity 23. In this embodiment, two jetting units are provided. Depending on the requirements, one jetting unit can be activated, or both units can be activated simultaneously or sequentially. An observation window 24 for observing the stability of particle jetting is provided on one side of the middle of the cavity 23, and a pre-collection disk 17 is provided on the other side. The pre-collection disk 17 is placed below the crucible 6. After the droplet jetting stabilizes, the pre-collection disk 17 is removed to proceed with the deposition process.

[0060] The crucible 6 has at least one through hole at its bottom for the melt to drip. Figure 1 As shown, the end of the transmission rod 4 extends into the through hole. A connecting sleeve 7 is fitted around the outside of the crucible 6. The connecting sleeve 7 has at least one groove that mates with the bottom of the crucible to accommodate the microporous sheet 8. In this embodiment, four grooves are provided to hold four different apertures (e.g., ...). Figure 2 The microporous sheet 8 (as shown) has micropores with a conical design of 20° to 70°. To further improve stability, a layer of wettable material that does not react with the molten metal to be sprayed can be provided on the upper surface of the microporous sheet 8. 0.1-2 mm of non-wetting material is retained at the micropore nozzle of the microporous sheet 8.

[0061] The computer 11 program is transmitted to the motion control card, thereby controlling the movement path of the motion platform 12 in the three-dimensional motion system;

[0062] The liquid level control system replenishes the liquid level that is reduced by the melt spraying through the liquid level adjusters 9 and 9', so as to keep the overall liquid level stable; the temperature controller 10 controls the temperature of the spraying and deposition parts, the heaters 5 and 5' can be used to heat the crucibles 6 and 6' to make the metal molten, and the heating plate 14 can be used to heat the interconnected devices or substrate 15 to a suitable temperature.

[0063] The crucible 6 and 6' and the cavity 23 are connected to the atmosphere through the crucible cavity connecting pipe 18 and the cavity connecting water valve 16 to maintain a stable air pressure balance; a certain pulse waveform is applied to the piezoelectric ceramic 2 to drive the transmission rod 4 to produce a quantitative displacement, which generates regular disturbance to the melt near the micropore, realizes droplet spraying, and sprays it onto the electronic device or substrate 15 on the motion platform 12 to realize bump fabrication or electronic interconnection.

[0064] A three-dimensional motion system is provided at the bottom of the cavity 23. Electronic devices or substrates 15 move on their motion platform 12 (on which a hot water cooling plate 13 is provided) according to a preset path within the cavity 23, receiving the sprayed droplets to achieve bump preparation or electronic interconnection.

[0065] The specific implementation steps are as follows:

[0066] S1. Set relevant parameters according to the required electronic interconnection needs, and use the computer 11 program to set the motion path of the motion platform 12; set the pulse waveform and frequency of driving the piezoelectric ceramic 2.

[0067] S2. Place the interconnecting materials into crucibles 6 and 6' respectively, and place the four microporous sheets 8 into the grooves of the connecting sleeve 7 (e.g., Figure 2 As shown, the bottom plane of the four microporous sheets 8 has four micropores of different sizes. The heater 5 is placed on the outside of the crucible 6 and a thermocouple is placed in it to monitor the temperature. To increase efficiency, two or more units can be sprayed simultaneously to heat the crucible 6'. The operation is the same as that performed on the crucible 6.

[0068] During simulated spraying, it was found that due to the lack of wetting between the melt and the microporous sheet material at the micropores, the melt repeatedly exhibited contraction and expansion at the micropores during disturbance, as shown in the attached figure. Figure 3 As shown in (1) and (2), this problem affects the stability of the jet. The stability of the jet at the nozzle is an important prerequisite for ensuring direct microelectronic interconnection. Therefore, this problem is addressed by improving the microporous sheet structure and materials to make the jet more stable.

[0069] Improving the structure and materials at the micropores can enhance the stability of microdroplet ejection, such as... Figure 3As shown in (3), the micro-orifice is designed as a cone shape of 20° to 70°. The weight of the melt itself effectively suppresses its upward contraction, thereby increasing spray stability. Figure 3 (4) A layer of wetting but non-reactive material is coated on the upper surface of the micro-orifice. Only 0.1-2 mm of non-wetting material is left near the nozzle according to the actual micro-orifice size to ensure smooth spraying. Due to the constraint of the wetting material, the shrinkage and expansion of the melt at the micro-orifice can also be effectively suppressed, thereby increasing its stability. This device saves a lot of time and cost and has great development prospects in the field of microelectronics.

[0070] S3. Use vacuum pump 22 to evacuate crucible 6 and 6' and cavity 23 to below 10 Pa. Open cavity gas distribution valve 19 to fill crucible 6 and 6' and cavity 23 with inert protective gas 20 to make them in a slightly positive pressure state. Repeat the process once more to clean the gas.

[0071] S4. Heat the crucibles 6 and 6' using heaters 5 and 5' to completely melt the metal material; heat the device to be deposited and interconnected using heating plate 14 to the appropriate temperature required for interconnection. After heating and during heat preservation, open the cavity water valve 16 to discharge excess gas from the crucibles 6 and 6' and the cavity 23 to maintain pressure stability.

[0072] S5. Depending on the required droplet size, place the transmission rod 4 at the required aperture. When the aperture size needs to be changed, simply lift the transmission rod 4, rotate it at the corresponding angle, and then lower it to the corresponding micropore to prepare droplets of different sizes. Set different liquid level heights so that the pressure generated by the melt surface is less than the pressure required to overcome the micropore.

[0073] Furthermore, before the microdroplet is stably ejected, the pre-collection tray 17 is pushed directly below the crucible 6; the position of the lifting platform 1 is adjusted so that the transmission rod 4 is near the bottom of the crucible 6, and the set pulse waveform is output to the piezoelectric ceramic 2. The piezoelectric ceramic 2 drives the transmission rod 4 to produce a small displacement and eject the droplets. The ejection status of the droplets is observed through the observation window 24. After the waveform and the height of the transmission rod 4 are adjusted to stabilize the ejection, the pre-collection tray 17 is pulled back, and the preparation of ball grid array bumps, microcircuit printing, and column array deposition are carried out.

[0074] Among them, the liquid level height is adjusted according to the particle size requirements to meet the needs of preparing particles or bumps of different sizes and printing microcircuits. The critical pressure value required for the droplets to overcome surface tension is P. 临 It can be expressed by equation (1):

[0075]

[0076] Where γ is the surface tension, θ is the wetting angle between the droplet and the microporous sheet, d is the diameter of the micropore, and the liquid itself has a certain weight, generating pressure P. 自It can be expressed by equation (2):

[0077] P 自 =ρgh (2)

[0078] ρ is the solder density, and h is the height of the liquid surface formed by the molten metal after melting. When P 临 Greater than P 自 Then, by combining piezoelectric ceramics and a transmission rod, regular disturbances are applied to the micropores to overcome the surface tension of the melt at the micropores, thus achieving spraying.

[0079] Furthermore, experiments revealed that the rise time of the pulse waveform and the voltage jointly determine whether spraying occurs. Taking a 280μm aperture as an example, when the voltage is 45V, the rise time needs to be less than 225μs to complete spraying; when the voltage increases to 75V, the rise time needs to be less than 450μs to complete spraying. A 100μs change in rise time results in a change of approximately 50μm in solder ball size; a 22.5V change in voltage also results in a change of approximately 50μm in solder ball size. For a wider range of size control, a single variable is insufficient, as both excessively short rise times and excessively high voltages prevent stable spraying. Therefore, it is necessary to coordinate several key parameters, including rise time, voltage, pin spacing, and aperture. Again, using a 280μm aperture as an example, with a rise time of 150μs, a voltage of 4V, and a pin height of 1.98mm, the solder ball size is 207μm; with a rise time of 250μs, a voltage of 4V, and a pin height of 0.08mm, the solder ball size is 328μm. Therefore, it can be seen that with a single pore size, the particle size of hundreds of micrometers can be controlled simply by adjusting the parameters. When the bottom of the crucible is as follows... Figure 2 As shown, four different pore sizes can be assembled, such as 50μm, 150μm, 450μm and 750μm. By combining different pore sizes, a wide range of size control (25-800μm) can be achieved at one time to realize full coverage of the droplet size, and it is easy to realize multiple micro interconnects at one time.

[0080] This invention allows for temperature control of the melt and substrate 15 within crucibles 6 and 6' during the fabrication process, enabling interconnection at suitable temperatures to achieve good interconnection without damaging electronic devices. The dimensions are controllable; the position of the drive rod 4 can be switched according to the requirements of the interconnect solder joints and wires, placing it near the desired size. Combined with parameter adjustment using the piezoelectric ceramic actuator 21, precise control from 25-800 μm can be achieved (e.g., ...). Figures 4-8 As shown, it greatly reduces the size gradient of interconnect solder joints and interconnect lines; the frequency is controllable, and the frequency can be adjusted according to different interconnection requirements to achieve various interconnection methods such as bumps and circuit lines in conjunction with the three-dimensional platform; the aperture range of the microporous sheet is 25-800μm, and its material can be graphite, zirconium oxide, alumina, aluminum nitride, stainless steel, etc., which can be adjusted according to the material or size required by the bump.

[0081] The process of this invention has good controllability and high flexibility. The sprayed microdroplets are stable, uniform, and have controllable size, making it easy to achieve efficient printing and personalized needs for microelectronic interconnects and bumps.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An apparatus for fabricating microelectronic interconnects and bumps based on pulsed micro-orifice jetting, characterized in that, include: The droplet ejection system has at least one set of ejection units inside the cavity. An observation window for observing the stability of particle ejection is provided on one side of the middle of the cavity, and a pre-collection plate is provided on the other side. The micro-holes at the bottom of the ejection unit are tapered with an angle of 20° to 70°. The upper surface of the micro-hole sheet is provided with a layer of wettable material that does not react with the molten metal to be ejected. 0.1-2 mm of non-wetting material is retained at the micro-hole nozzle of the micro-hole sheet. The liquid level control system replenishes the liquid level that is reduced by the melt injection through the liquid level adjuster, so as to keep the overall liquid level stable. And a three-dimensional motion system, set at the bottom of the cavity, where electronic devices or substrates move on their motion platform according to a preset path in the cavity, receiving the sprayed droplets to achieve bump fabrication or electronic interconnection; The droplet ejection system includes a crucible and a lifting platform connected to a piezoelectric ceramic located above the crucible, a piezoelectric ceramic and a transmission rod connected below the lifting platform and extending into the crucible. A connecting sleeve is fitted around the outside of the crucible, and the connecting sleeve has at least two grooves for accommodating microporous sheets. A heater for heating and melting metal is provided outside the connecting sleeve. The piezoelectric ceramic actuator drives the piezoelectric ceramic according to a set pulse waveform, and the piezoelectric ceramic drives the transmission rod to generate displacement, generating regular local disturbances near the micropores on the microporous sheets, causing the melt to overcome surface tension and eject from the micropores. The pore size of the micropores ranges from 25 to 800 μm, and the vibration frequency of the piezoelectric ceramic is between 0.1 and 1000 Hz.

2. The apparatus for fabricating microelectronic interconnects and bumps based on the pulsed micro-orifice jetting method according to claim 1, characterized in that, Each groove of the connecting sleeve is provided with a microporous sheet with a different aperture. The rotation of the transmission rod is achieved by a rotary dynamic seal above the cavity. The transmission rod rotates to a position corresponding to the micropores with different apertures, and the displacement disturbance of the melt is generated in conjunction with the injection parameters to achieve the injection of droplets of various sizes.

3. The apparatus for fabricating microelectronic interconnects and bumps based on the pulsed micro-orifice jetting method according to claim 2, characterized in that, A crucible-cavity connecting pipe is provided between the crucible and the cavity to prevent different gas pressures due to temperature differences.

4. The apparatus for fabricating microelectronic interconnects and bumps based on pulsed micro-orifice jetting according to claim 2, characterized in that, The liquid level height is adjusted according to the particle size requirements to accommodate the fabrication of particles or bumps of different sizes, as well as microcircuit printing. The critical pressure required for the droplets to overcome surface tension is [value missing]. It can be expressed by equation (1): （1）； in, For surface tension, The wetting angle formed by the droplet and the microporous sheet. The diameter of the micropore is given; the liquid itself has a certain weight, which generates pressure. It can be expressed by equation (2): （2）； ρ is the solder density, and h is the height of the liquid surface formed by the molten metal after melting. Greater than Then, by using piezoelectric ceramics and a transmission rod to apply regular disturbances to the micropores, the melt at the micropores can overcome the surface tension and thus achieve spraying.

5. The apparatus for fabricating microelectronic interconnects and bumps based on the pulsed micro-orifice jetting method according to claim 2, characterized in that, The crucible contains a molten material, and a thermocouple is placed in the molten material to provide real-time temperature feedback to a temperature controller, thereby controlling the metal temperature. The temperature controller is connected to a heating plate on the motion platform to achieve the required deposition temperature.

6. A method for fabricating microelectronic interconnects and bumps based on pulsed micro-orifice jetting, characterized in that: Using the device described in any one of claims 1 to 5, the required interconnection path is set by a computer program, causing the motion platform to move along the set path; the molten metal in the crucible is heated to a molten state by a heater; different liquid level heights are set according to the pore size and material of the microporous sheet to ensure appropriate pressure at the nozzle; a certain pulse waveform is applied to the piezoelectric ceramic actuator to drive the piezoelectric ceramic to vibrate, which in turn drives the transmission rod to produce a small displacement acting on the local molten metal at the bottom of the crucible; each pulse can form a quantitative droplet at the small hole, which is stably and uniformly ejected.

7. The method according to claim 6, characterized in that, Includes the following steps: S1. Set the motion path of the motion platform to match the frequency of the pulse waveform and the injection distance according to the required micro-interconnection requirements; S2. Place the materials required for interconnection into a crucible, place the microporous sheet at the bottom of the connecting sleeve, and place a heater on the outside; S3. Evacuate the crucible and cavity using a vacuum pump, open the cavity gas distribution valve to fill with protective gas, and bring the cavity into a slightly positive pressure state. S4. According to the interconnection type and size requirements, rotate the drive rod to the position corresponding to the micro-hole to be sprayed and lower it to the micro-hole. Set the corresponding pulse waveform and apply it to the piezoelectric ceramic driver to drive the piezoelectric ceramic and drive the drive rod to produce a small displacement, generating regular local disturbance near the micro-hole so that the melt overcomes the surface tension and is sprayed out from the micro-hole. S5. First, collect the particles with a pre-collection disk. When the droplet spray is stable and the accuracy is guaranteed, pull back the pre-collection disk so that the microdroplets are sprayed to the required position for substrate interconnection to achieve the purpose of electronic interconnection.

Images