The present invention disclosures an architecture for printed circuit boards (PCBs) with conductive circuit traces within grooves in the surface of one or more PCB layers. More specifically, the grooves are preferably formed by embossing the PCB layers and filling the grooves with conductive materials. This type of architecture can be applied to almost all types of PCBs, Systems in a Package (SiPs), and related types of circuit devices.
Various embodiments of the present disclosure teach a device generally constructed from at least one PCB layer. The PCB layer includes pads for the connection of circuit devices such as ICs, LEDs, switches, connectors, and other types of electrical components. Most of the pads are connected by circuit traces to one or more other pads for the conduction of electrical signals. In some cases, a multi-layer PCB would have interconnect vias to make connection from one layer to another. All of these traces, pads, and vias are embedded into the PCB layers in the technology disclosed herein. By embedding these elements into the PCB layers, durability is increased over current state of the art PCBs, where those elements are thin, vulnerable metal films positioned atop the surfaces of the PCB layers. By embedding the elements (traces) in the PCB, the thickness (depth of the traces) can be orders of magnitude greater than current state of the art traces. This allows for trace width and spacing to be much less than current state of the art PCBs. Further, current state of the art trace widths is limited to 100 um in width. This width is due to the manufacturing limitations of the process. Embossed grooves can be, and have been, created with widths as small as 10 nanometers and depths up to five times the width. The embossed grooves are filled with conductive material via the insertion of inks, via chemistry methodology, or plating techniques.
Due to the much greater thickness (depth) of the disclosed traces compared to current art devices, the width of the traces can be much smaller while still achieving equivalent electrical conduction. (The total cross-sectional area is the same in the traces disclosed herein and in the current art devices.) The reduced width allows for more densely populated PCB devices.
The accompanying drawings, where like reference numerals refer to identical or functionally similar elements throughout the separate views, together with the detailed description below, are incorporated in and form part of the specification, and serve to further illustrate embodiments of concepts that include the claimed disclosure, and explain various principles and advantages of those embodiments.
The methods and systems disclosed herein have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
Two mechanical types of components are shown, a through hole type component and a surface mount device (SMD) type. The connector 4 is of the through hole type. The connector 4 has pins that extend through holes in the PCB board 10. The pins make electrical and mechanical connections via the above-mentioned solder or ink. The SMD type devices generally have rectangular shaped pads that connect to corresponding pads on the PCB board 10. Mechanical and electrical connections are made by filling the gaps between the pads with solder or conductive ink.
Referring now to
With the components removed in
Wide circuit trace 18 is a trace that is wider than a standard trace, thereby allowing a greater amount of electrical current to flow therethrough. The width of the trace 18 is engineered for the needs of a given implementation. Vias 16 are required to connect circuitry on the first circuit layer 11 to successive layers below. It should be noted that the surfaces of the traces, pads, and vias are typically coated with a conductive material or materials. The remaining areas of the circuit layer 11 are not conductive. These two types of areas (conductive and non-conductive) allow for the control of electrical signals over the PCB assembly 1 and to and from the different electrical components.
Referring now to
Referring now to
Referring now to
All of the multiple circuit layers of the PCB are typically bonded together. The bonding can be done with an adhesive or by other means know to those skilled in the art of PCB manufacture. It should be noted that the PCB assembly 1 described herein is not particularly complex. Many PCB assemblies are far more complex and include have many more components, and have more complex components. A PCB board used for such complex assemblies might require ten or more circuit layers to connect all of the required components and to deliver multiple required voltages.
There are many options for materials that can be used to form the substrate. One skilled in the art of PCB board manufacturing would readily understand the factors involved in the choice of material for a given application. Almost any type of insulating material can be deployed as a circuit substrate including but not limited to polymers, ceramics, glass, and dielectric semiconductor materials.
The conductive surfaces in the circuit layers can be created in a number of ways. The preferred method is to dispense liquids to the grooved areas. Different methods can be deployed to do this: needles, inkjet, and conventical type printing can be deployed. The grooves aid in the distribution of liquids to the intended areas (conductive surfaces to be formed) and aid in excluding the liquid from unintended areas (nonconductive surfaces). Capillary action is the physical force that drives the movement of the liquids in the grooves. Capillary action can cause liquid to move within the grooves and fill them with conductive material, even when the conductive material is not directly applied to the desired area. In many cases the liquid may only need be applied at the ends of the trace grooves, pads, or vias. Capillary action draws the liquid down the grooves to entirely fill them. The filling force of capillary action is greater for smaller channel widths. This is ideal for circuit formation. The current art for PCB circuit traces is 100 um wide. Embossed groove channels filled with capillary action can be much smaller than that.
The surface tension of the grooves, which may be embossed channels, also affects the capillary force. Those skilled in the art of surface tension and capillary action can readily devise appropriate chemistries choosing the substrate material, substrate surface characteristics, and the liquid used to fill the grooves to maximize capillary force. External pressure, a vacuum, gravity, and/or force derived from motion can also be used to enhance the filling of the grooves.
The dispensed liquid used to fill the grooves in the surface of the PCB to create the conductive surfaces can be any one of a number of solutions. The preferred solution is a catalyst liquid that creates a surface that can be electroless plated with copper or other conductors. The catalyzed surfaces coming into contact with a catalyzed solution enables chemical plating. Surfaces that have not been catalyzed will not plate during the plating process. Therefore, the grooves, pads, and vias are filed with a catalyzing solution to readily enable chemical plating. Surfaces that are not desired to be conductive are left uncatalyzed, and are therefore not affected during the plating process. The uncatalyzed surfaces do not form and retain a conductive surface. The areas of conductivity selectively created by the catalyzed surfaces allows for the submersion of the entire substrate in a chemical plating solution for the plating process. The noncatalyzed areas on the substrate do not plate where the substrate surface is not catalyzed. The surface catalyzation and plating of a substrate generally requires a number of process steps, including: (1) Cleaning and or etching of the substrate; (2) Neutralizing; (3) Catalyzing; (4) Activating; and (5) Electroless plating.
An alternate method of fabrication would be to catalyze the entire surface of the substrate and then selectively plate the grooves. Still another method of creating the desired conductive areas would be electroplating. Electroplating requires an electrical connection to the areas to be plated. With some circuit designs, the required electrical connections are easily established. With other designs, it is far more challenging. The circuit design for a given implementation drives what type of plating is deployed. Electroplating can be used to plate more than one type of material. The material may be chosen according to the requirements of a given desired product. Gold, for example may be applied for corrosion resistance, tin for solder adhesion and flow, and nickel for durability.
Most PCB boards would also include a solder mask coating and printed nomenclature. These same processes may be added to the disclosed PCB board and are not presented in this disclosure as they are well known in the art.
An alternate embodiment for metallization is the substitution of conductive ink for one or both of the catalyzing and plating processes. Conductive ink can also be used for just the plane metallization. Just as there is a large number of suppliers for plating chemicals there are also many suppliers of conductive inks and related types of materials.
In sum, fabrication may be accomplished by several methods. A preferred embodiment of fabrication utilizes the following steps: (1) Emboss a substrate with traces and counterbores; (2) Metalize embossed channels and counterbores; (3) Repeat steps 1 & 2 for all layers; (4) Laminate all layers together; (5) Drill holes and vias as required; and (6) Metalize vias and holes.
An alternate preferred embodiment for the fabrication process includes the following steps: (1) Emboss a substrate with traces, vias, holes and counterbores; (2) Repeat steps 1 & 2 for all layers; (3) Laminate all layers together; (4) Drill additional holes and vias if needed; and (5) Metalize all traces, vias and holes by forcing liquids through all of the traces, vias and holes in all of the layers.
A second alternate preferred embodiment for the fabrication process includes the following steps: (1) Emboss the base substrate with traces and counter bores; (2) Create holes including via holes as needed; (3) Metalize embossed channels, counterbores, vias and holes; (4) Emboss another substrate with traces and counter bores; (5) Create holes including via holes as needed in the substrate; (6) Laminate the substrate to the previous substrate(s); (7) Metalize embossed channels, counterbores and holes (vias and holes are metalized down to lower layer(s)) making connections to the lower layers; and (8) Repeat steps step 4 through 6 as required.
Metallization may also be accomplished by several methods. The method chosen depends on the parameters of the given construction required. One preferred embodiment of metallization utilizes the following steps: (1) Activate only the surfaces to be metalized with a catalyst containing a noble metal; and (2) Chemically plate the catalyzed surfaces with a metal. Note that the only the catalyzed surfaces will be plated. This allows for the entire part to be submerged in the plating solution.
An alternate preferred embodiment for the metallization process includes the following steps: (1) Activate the entire part with a catalyst containing a noble metal; and (2) Selectively chemically plate the catalyzed surfaces with a metal. The surfaces that are not to be plated need to be masked to keep them from being plated.
Another alternate preferred embodiment for the metallization process includes the following steps: (1) Coat the surfaces that are not to be plated with a sacrificial material; (2) Activate the entire part with a catalyst containing a noble metal; (3) Remove the sacrificial material thereby removing the catalyzed surfaces in the areas that are not to be metalized; and (4) Chemically plate the remaining catalyzed surfaces with a metal. Note that the only the catalyzed surfaces will be plated. This allows for the entire part to be submerged in the plating solution.
Still another alternate preferred embodiment for the metallization process includes the following steps: (1) Partially metalize the surfaces to be plated with a conductive ink or a solution, nano particles, or a conductive material; and (2) Chemically plate the metalized surfaces with another metal. Note that the only the previously metalized surfaces will be plated. This allows for the entire part to be submerged in the plating solution.
Yet another alternate preferred embodiment for the metallization process includes metallizing the desired surfaces with a conductive ink, nano particles, or a conductive material.
It should be noted that the systems and methods described above yield a significant advantage in the fabrication of PCB assemblies. With current art technology, traces are typically 100 um in width. With the technology disclosed herein, equivalent conductivities are achieved with trace widths of less than 1 um. The reduced width allows for much more compact arrangement of circuitry, and therefore the construction of much smaller electronic devices. The dimensions cited above are illustrative only. Many variations of trace and pad widths can be made while adhering to the teachings herein. These numbers are recited only to illustrate that with present technology, conductive surfaces can be made much more narrow while maintaining equivalent conductivity by increasing the depth of the groove used to form the conductive trace or pad.
The relationship of the passive devices 3 to the lower circuit layer 75 can best be seen in
Referring to
The top layer circuit elements—top layer connection 85, top layer traces 86, top layer pads 87—and the corresponding bottom layer components—bottom layer pads 89, bottom layer traces 90, and bottom layer connections 91—are metallic and are not shown as transparent. These metallic features make electrical connections from the LED die 85 to the edges of the LED PCB assembly 80.
An electrical signal is typically delivered to the edge of the LED PCB assembly 80 at the top layer connection 85. The top layer connection 85 is large relative to the other circuit elements to reduce the need for accuracy in aligning an external connection to the top layer connection 85. The top layer trace 86 conducts the electrical signal from the top layer connector 85 to the top layer pads 87. The top layer pads 85 deliver the signal to the top surface of the LED die 85. The signal conducts through the LED die 85 to the bottom layer pad 89. The conducted signal enables the production of light by the LED die 85. The signal is conducted to the bottom layer tracer 89 and then to the bottom layer connection 91. As with the top layer, the bottom layer would be connected to an external device that creates the electrical signal.
The traces are shown to be much more narrow than they are deep. This allows for high electrical conductivity with high optical clarity. Both are generally desired elements of an LED type device.
The top layer and bottom layer pads are shown to have multiple grooves in parallel. The actual number of grooves associated with the pads would be a function of the needs of the LED die 85 and the extraction of light from the LED die 85. The top layer pads 87 might be limited in size to maximize light output. The bottom side layer pads 89 may not need to allow light output. In fact, the bottom side layer pads 89 can be continuous or even larger than the LED die to reflect light to the top side of the LED PCB assembly 80.
The LED die 85 is shown to have tapered sides. This attribute aids in the assembly of the die to the LED spacer layer 83. The LED spacer layer 83 can be seen by isolated in
The metal plating of the pad traces is preferably thick enough that the metal surface extends slightly above the surface of the corresponding layer to ensure there is a good electrical connection between the LED die and pads.
Conductive ink could also be deployed to make the electrical connections between the LED die 85 and the top and bottom layer pads.
For a color display application, three of the LED PCB assemblies 80 would be deployed. One device would be configured with red LED dies, the second with green dies, and the third with blue.
Many of the disclosed LED PCB assemblies can be laminated together to form a 3D array of LEDs. This 3D array can be used to produce 3D images.
The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the present disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the present disclosure. Exemplary embodiments were chosen and described in order to best explain the principles of the present disclosure and its practical application, and to enable others of ordinary skill in the art to understand the present disclosure for various embodiments with various modifications as are suited to the particular use contemplated.
While this technology is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail several specific embodiments with the understanding that the present disclosure is to be considered as an exemplification of the principles of the technology and is not intended to limit the technology to the embodiments illustrated.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the technology. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It will be understood that like or analogous elements and/or components, referred to herein, may be identified throughout the drawings with like reference characters. It will be further understood that several of the Figures are merely schematic representations of the present disclosure. As such, some of the components may have been distorted from their actual scale for pictorial clarity.
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” or “according to one embodiment” (or other phrases having similar import) at various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Furthermore, depending on the context of discussion herein, a singular term may include its plural forms and a plural term may include its singular form. Similarly, a hyphenated term (e.g., “on-demand”) may be occasionally interchangeably used with its non-hyphenated version (e.g., “on demand”), a capitalized entry (e.g., “Software”) may be interchangeably used with its non-capitalized version (e.g., “software”), a plural term may be indicated with or without an apostrophe (e.g., PE's or PEs), and an italicized term (e.g., “N+1”) may be interchangeably used with its non-italicized version (e.g., “N+1”). Such occasional interchangeable uses shall not be considered inconsistent with each other.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It is noted at the outset that the terms “coupled,” “connected”, “connecting,” “electrically connected,” etc., are used interchangeably herein to generally refer to the condition of being electrically/electronically connected. Similarly, a first entity is considered to be in “communication” with a second entity (or entities) when the first entity electrically sends and/or receives (whether through wireline or wireless means) information signals (whether containing data information or non-data/control information) to the second entity regardless of the type (analog or digital) of those signals. It is further noted that various Figures (including component diagrams) shown and discussed herein are for illustrative purpose only, and are not drawn to scale.
While specific embodiments of, and examples for, the system are described above for illustrative purposes, various equivalent modifications are possible within the scope of the system, as those skilled in the relevant art will recognize. For example, while processes or steps are presented in a given order, alternative embodiments may perform routines having steps in a different order, and some processes or steps may be deleted, moved, added, subdivided, combined, and/or modified to provide alternative or sub-combinations. Each of these processes or steps may be implemented in a variety of different ways. Also, while processes or steps are at times shown as being performed in series, these processes or steps may instead be performed in parallel, or may be performed at different times.