This invention is directed generally to flexible circuits, and more particularly to flexible circuit boards and related systems.
Conventional circuit boards are typically formed from a rigid board that supports one or more electrical circuits. Such rigid circuit boards are typically used in electronic systems such as personal computers, cellular phones, televisions, and other devices. Conventional rigid circuits are often formed with multilayer printed circuit boards formed of glass cloth reinforced copper-clad plastic substrates. The substrates typically range in thickness from about 4-8 mils for the insulative plastic. The circuitry is typically etched into the glass cloth reinforced copper-clad plastic substrate. After etching, the inner layers of the board are laminated to form a multiple layer board formed of circuitry, a ground plane level and a power plane level. Holes are typically drilled through the board stack and walls of the holes are plated to form conductive interconnects between the multiple board layers. The process used to manufacture these boards has notable problems such as, drill wear and hole size limitations. In addition, the rigid boards are not useful in many applications where space is limited.
Flexible circuits have been made in an effort to overcome these limitations. Flexible circuits have been formed from flexible substrates having cover coats formed from non-photoimageable polyimide and polyester and other non-photoimageable cover coats, such as TEFLON and ultem. A drawback of these flexible circuits is that their utility is typically limited to specialized applications. A conventional fabrication method of the flexible circuit includes pre-punching the cover coats with holes for solder pads and then carefully aligning the cover coat on the base material. Industry needs call for more apertures in the cover coats. However, the current process cannot efficiently accommodate these changes without adding additional complexity and costs to the manufacturing process.
Moreover, flexible circuits typically include electrical conductors formed exclusively from copper foil. Such configurations are designed to bend only to a limited degree. In particular, such configurations are often capable of being bent in a circular configuration having a radius of curvature of about four inches. However, when the flexible circuits are folded in a smaller circle or folded into two planes that are parallel or nearly parallel to each other and in close proximity with each other, the copper foil breaks, thereby breaking the circuit and rendering the flexible circuit inoperable. Thus, a need exists for an alternative flexible circuit.
This invention is directed to a flexible electrical circuit formed from a flexible fabric and one or more conductive circuits attached to the flexible fabrics and formed at least partially from silver or other appropriate metals. The flexible electrical circuit may be configured for use in many applications, such as, but not limited to forming heaters, sensors, antennas, stretchable fabrics, medical applications, printed circuit boards, personal digital assistants (PDAs), and in other applications.
The flexible fabric may be formed from any fabric such as, but not limited to, nylon, polyester, acrylic, rayon, other polymeric materials, and other materials. In one embodiment, the flexible fabric may form a sheet of material. The flexible fabric may be stretchable, such as by including SPANDEX or other stretchable fibers in the formation of the flexible fabric. The flexible fabric may be used to form garments, such as shirts, pants, and other garments for positioning conductive circuits in close proximity to an outer skin surface of a person wearing the garment. The flexible fabric may also be launderable such that the fabric may be cleaned using mechanical washing machines and cleaned in other appropriate manners.
The conductive circuit may be formed from one or more conductive fibers. The conductive fibers may be formed from a core coated with a coating at least partially formed from silver. In at least one embodiment, the coating may be formed by at least 95 percent silver. The silver may be applied to the core with conventional metallizing techniques, such as chemical deposition and other appropriate methods. The silver coated core may be X-STATIC, produced by Sauquoit Industries, Inc., Scranton, Pa., or other appropriate materials. The core may be formed from materials including, but not limited to, nylon and other appropriate materials. In other embodiments, other metals may be used.
The conductive fiber may be embroidered onto the flexible fabric formed from the nonconductive material. The conductive fiber may be patterned stitched, which is also referred to as repetitive stitched, to adjust the resistance of the conductive circuit. The conductive fiber may also be plied two or more times to adjust the resistance of the conductive circuit.
In another embodiment, the conductive circuit may be formed from an etched silver layer attached to the flexible fabric and formed at least partially from silver. The etched layer may be created by applying a resist, such as acrylic, onto the flexible fabric to attach the layer to the flexible fabric. The layer may then be etched to remove excess portions of the layer to form the conductive circuit.
The conductive circuit may be formed in any appropriate configuration. For instance, the conductive circuit may be formed in a serpentine configuration to create a heater, a generally helical shape to form a sensor, such as an electrocardiogram (EKG) sensor used together with an EKG system, or an antenna. The conductive circuit is not limited to these use but may be used in other application as well.
An advantage of this invention is that the flexible circuit may be formed from a flexible fabric that is launderable, thereby enabling the flexible circuit to be incorporated into garments and other items that are laundered.
Another advantage of this invention is that the flexible circuit is very flexible and may be folded without breaking the conductive circuit.
Yet another advantage of this invention is that the flexible circuit is cost effective and can be manufactured in large quantities efficiently.
Another advantage of this invention is that the conductive fibers may be woven, sewn, knit, embroidered or otherwise attached to the flexible fabric to form the flexible electrical circuit.
Still another advantage of this invention is that the flexible electrical circuit is lightweight, thereby making it useful in a variety of applications.
These and other embodiments are described in more detail below.
The accompanying drawings, which are incorporated in and form a part of the specification, illustrate embodiments of the presently disclosed invention and, together with the description, disclose the principles of the invention.
As shown in
The flexible fabric 12 may be formed from any fabric. The fabric 12 may be, but is not limited to being, fabrics and filler materials formed from nylon, polyester, acrylic, rayon, other polymeric materials, and other materials. In one embodiment, the flexible fabric 12 may form a sheet 16 of material, as shown in
The conductive circuit 14 may be formed from one or more conductive fibers 20. The conductive fibers 20 may be formed from a core 22 coated with a coating 24 at least partially formed from silver, as shown in
The conductive fiber 20 may be embroidered onto the flexible fabric 12 formed from the nonconductive material. The conductive fiber 20 may be patterned stitched, which is also referred to as repetitive stitched, to adjust the resistance of the conductive circuit 14. The conductive fiber 20 may also be plied two or more times to adjust the resistance of the conductive circuit 14. For instance, as shown in
In another embodiment, as shown in
The conductive circuit 14 may be formed in any appropriate configuration. For instance, the conductive circuit 14 may be formed in a serpentine configuration, as shown in
As shown in
The flexible electric circuit 10 may be formed such that the fabric 12 may be folded, as shown in
While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.
This application claims the benefit of U.S. Provisional Application No. 60/673,709, filed Apr. 21, 2005.
Number | Date | Country | |
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60673709 | Apr 2005 | US |