The present application relates to printing electrically conductive traces by applying ultrasonic energy to a conductive material. The present application also relates to a multiple-layered printed circuit board (PCB) fabrication process using ultrasonic energy for two (2)- and three (3)-dimensional (3D) PCB structures. In particular, the present application relates to an ultrasonic method for printing electrical patterns onto a PCB without employing a chemical or heating process.
In general, PCB fabrication includes a “build-Up method” and a “stack-up method.” A typical “build-up method” for PCB fabrication includes a cycle of drilling on a copper clad laminate (CCL), etching, dry film, inner layer exposing, and developing, the etching process requiring use of hazardous chemicals. A typical “stack-up method” for PCB fabrication includes a printing and etching process, silk screening or photo-printing using a resist on the CCL, and removal of the resist after completing the etching, requiring use of various solvents and chemicals. Increasingly stringent environmental regulations make use and disposal of solvents and chemicals difficult and expensive. Thus, there is a need for a flexible method for fabricating PCBs, not requiring multiple steps such as printing and etching processes, while providing traces with suitable electrical conductivity. Recently, conductive-ink based PCB printing on an insulation substrate has been developed. However, the conductive inks always contain a solvent that causes impurity, resulting in high resistivity even if silver is used, for example, 10 times higher than conventional copper PCBs.
According to at least one embodiment of the present invention, the present application provides a method and apparatus for fabricating PCBs that enables 2D and 3D electrical patterns (traces) with multiple-layered, 3D-shaped construction without using chemical treatment or other cumbersome processes used in the conventional PCB fabrication method(s). Disclosed in the present application are vibrational energy-transfer devices and processes for providing electrical patterns, vias between layers, insulation layers or coating, silk screen, masking, electrical connection (bonding, reflowing and soldering) to external electric elements, localized packaging for an electrical element, and a designated part during PCB fabrication. The devices and processes disclosed in the present application with reference to various embodiments eliminate complexity and environmental hazards raised in conventional chemical etching/plating processes. The inventive process according to various embodiments may reduce time and cost significantly, thus allowing (or facilitating) more effective PCB fabrication.
According to at least one embodiment of the present invention, a method for printing electrically conductive traces on a non-conductive material includes: printing a conductive material onto a non-conductive material by transferring ultrasonic energy to the conductive material; forming non-conductive resin on the non-conductive material on which the conductive material has been printed, using a three-dimensional printer head, the non-conductive resin being (or serving as) an insulation component; and forming a connecting portion or via hole in the non-conductive resin.
According to at least another embodiment of the present invention, a method for printing electrically conductive traces on a non-conductive material includes: printing a conductive material onto a non-conductive material by transferring ultrasonic energy to the conductive material; placing a prepreg on the non-conductive material on which the conductive material has been printed; and forming a connecting portion or via hole in the prepreg.
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
The following description is of various exemplary embodiments only, and is not intended to limit the scope, applicability or configuration of the present disclosure in any way. Rather, the following description is intended to provide a convenient illustration for implementing various embodiments including the best mode. As will become apparent, various changes may be made in the function and arrangement of the elements described in these embodiments without departing from the scope of the present disclosure. Hereinafter, features of embodiments of the present invention will be described with respect to the embodiment(s) illustrated in the annexed drawings.
In the present application, the terms “print” and “bond” may be used interchangeably. In the present application, three types of procedures are disclosed for 3D-shaped multiple-layered ultrasonic voxel manufacturing: a center started procedure, a build up procedure, and a stack-up procedure. In various embodiments disclosed in the present application, ultrasonic energy is applied to bond various materials (metals, polymers, ceramics) to similar or dissimilar materials. For example, a conductive material and a non-conductive material may be bonded by applying ultrasonic energy. Feedstock materials for bonding may be in various forms such as wire, strip, foil, etc.
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Further, various insulating materials may be additively fabricated onto the electrical patterns to build 3-dimensional PCB structures. Referring to
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As described above, the procedures disclosed for 3D-shaped multiple-layered PCB manufacturing according to embodiments of the present invention are non-chemical and simple to be implemented, e.g., for mass production. The ultrasonic energy is used to bond conductive materials to insulating substrates by using bonding tools shown, for example, in
In embodiments disclosed in the present application, feedstock materials for conductive and insulating (non-conductive) materials may have the following forms: wire, ribbon, foil, stripe, plate, and liquid. However, it is understood that they are not limited to these forms. A bonding tool in embodiments of the present application may have various element shapes. Because ultrasonic energy is focused on an end-tip of an element, the surface configuration of the end-tip may be important and may be in various patterns such as groove, knurling, or lattice to hold feedstock materials on the contact surface during a building process.
For non-conductive layers and solder mask layers described above, a micro sized multi-nozzle head may be used with resin and adhesive materials such as epoxy and solder mask paste. Further, automatic multiple-material feeder has a capability to control various forms of materials for conductive and non-conductive materials in forms of foils, sheet, wire, strip, filament, liquid, solder paste, solder mask paste, etc. Furthermore, the following may be used as a filler material for via holes described above: conductive materials such as pure or alloys of copper, aluminum, silver, tin, and gold, and a shape of the conductive material may be wire, ribbon, metal powder, micro sized ball, or metal sheet/foil. Moreover, holes may be filled with non-conductive material(s) as necessary.
The system may be integrated with other capabilities in-line and post nondestructive evaluation/inspection, a metrology tool for verifying correct dimensions, in-line correction during building by adding and removing materials, allowing easy swapping of tools. All functions may be integrated as a single, multifunctional head or modularized plural heads. The milling spindle for via holes and part removal is placed on the multifunctional head. Thus, a contact-based probe unit may be integrated with the multifunctional head to control the dimensional accuracy at a periodic interval preset by a user.
The system bonding process according to at least one embodiment of the present invention, which uses voxel-by-voxel ultrasonic energy transfer, is a solid state, nonthermal bonding process using ultrasonic energy. The system bonding process strongly bonds segments of material to dissimilar materials at subsurface levels through plastic deformation and/or atomic diffusion.
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The system bonding process may consume very little energy, for example, about 2 W for 18 μm diameter gold wire. No melting/sintering is involved in the system bonding process according to various embodiments, and thus, no thermal stresses/defects are created.
According to at least another embodiment of the present invention, an insulator 3D printing head may be used for simultaneous printing of multiple materials.
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A wire cutter may be used to end feedstock segments when new line segments or material change is required. For example, types of the wire cutter include a pneumatic cutter type, power scissors type with vibrating blades, and ultrasound cutting tools.
The milling tool is located on a multifunctional head with its own small linear stage such that a tip is normally positioned above a bonding tool and lowered when milling is activated. The milling tool is used during a building process to ensure proper dimensions.
According to at least one embodiment of the present invention, a precision motion platform includes a force sensor with a force sensing mechanism because best bonding may occur when an optimal normal force is applied to feedstock.
According to at least another embodiment of the present invention, a force sensor is not necessary if a new motion platform Z-stage, for example, PI V-551.7x, is used. It is possible to read force through current draw in a system up to 0.1N accuracy, using the new motion platform Z-stage. Thus, using the motion platform Z-stage may simplify the system such that no analog sensor is necessary. Use of the motion platform Z-stage allows use of a moment/displacement method for readings, and simpler software may be implemented.
S1 is a step to wait for print data from an external device. If data are received from an external device (Yes), then the next procedure, S2, is performed. Otherwise (No), continue waiting for print data from an external device.
S2 is a step to check the current platform position.
S3 is a step to calculate the next print head location.
S4 is a step to move the print head to the next position until the print head reaches the correct position. When the print head reaches the position (YES), the next step, S6, is performed.
S6 is a step to check the force sensor reading to determine a preset force. When the force reaches the preset force (OK), Z-axis control is stopped and the next procedure, S7, is performed. When the checked force is not OK, S5 is performed to control the Z-axis.
S7 is a step to activate the ultrasonic bonder for an activation duration.
S8 is a step to check the activation duration. When the activation duration is reached (YES), the next step, S9, is performed. Otherwise (NO), the activation duration is checked until the activation duration is reached.
S9 is a step to deactivate the ultrasonic bonder.
S10 is a step to check a status of feedstock materials (remaining amount, etc.) and control the feeder operation.
S11 is a step to check if the feedstock needs to be cut. If the feedstock needs to be cut (Yes), the next step, S12, is performed. Otherwise (No), the next step, S14, is performed.
S12 is a step to cut the material.
S13 is a step to check a status of feedstock materials (remaining amount etc.) and control the feeder operation.
S14 is a step to determine if the end of trace build is reached. If the end of the trace build is reached (Yes), the next step, S15, is insulation layer build. If the end of the trace build is not reached (No), the next step is to build more traces on the same layer.
S15 is a step to determine the necessity of an insulation layer. If an insulation layer is necessary (Yes), then the next step, S16, is to build the insulation layer. If not (No), the next step, S17, is performed.
S16 is a step to build the insulation layer. Once the insulation layer is built, the next step, S17, is performed.
S17 is a step to determine the necessity of a stack-up process. If the stack-up process is necessary (Yes), then the next step, S18, is performed to stack prepreg (or other non-conductive material/insulation layer). If no stack-up process is necessary (No), the next step, S19, is performed.
S18 is a step to stack the prepreg (or other non-conductive material/insulation layer) up on the current layer.
S19 is a step to determine if the current layer is completed. If the current layer is completed (Yes), then the next step, S20/S21, is to make vias and holes. If the current layer has not been completed (No), then the next step is to build more layers by going back to perform S2.
S20 is a step to determine the necessity of vias and holes. If vias and holes are necessary (Yes), then the next step, S21, is to make the vias and holes. Otherwise (No), the next step, S22, is performed.
S21 is a step to make vias and holes.
S22 is a step to determine the necessity of flipping the layer. If flipping is necessary (Yes), the next step, S23, is to flip the layer. If no flipping is necessary (No), the next step, S24, is performed.
S23 is a step to flip the layer.
S24 is a step to determine if overall build is completed. If overall build is completed (Yes), either all procedures are finished or goes back to S1. If overall build is not completed (No), the procedure goes back to S2 to perform the entire procedure described above repeatedly.
Aspects or features of embodiments of the present invention are also applicable to directly solder an active/passive electronic component on electrical patterns on the substrate. An extensive application of aspects or features of embodiments of the present invention may include additive packaging around silicon-dies by building micro-thin layers of deposition, electrical contacts, connections, insulation, filling, while ensuring protection against impact, corrosion, heat dissipation, and counterfeiting. Aspects or features of embodiments of the present invention may provide a same process to additively build all packaging components layer-by-layer on/around a semiconductor die such as contacts, pins or leads, bumps (lead or copper), electrical insulators, filling, redistribution layer (RDL) etc. with metal, polymer, and ceramics on a single platform.
Aspects of the present disclosure relate to the art and science of a multiple-layered printed circuit boards (PCB) fabrication process using ultrasonic energy for 2- and 3-dimensional PCB structures. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
Pursuant to 35 U.S.C. § 119(e), this application claims the benefit of Provisional Application No. 62/777,006 filed on Dec. 7, 2018, the contents of which are hereby incorporated by reference herein in their entirety.
Number | Date | Country | |
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62777006 | Dec 2018 | US |