Patent Application
20080124528
The present invention relates generally to printed electrical circuitry, and more particularly, to a printed electronic device and methods of measuring the value of electronic devices that are formed by contact printing.
Conventional fabrication methods for printed circuits have always utilized one or more methods of creating a conductive metal pattern on a dielectric substrate. Some of the various methods include print and etch, electroless copper deposition, vacuum deposition, and screen printing, contact printing, or ink jetting a liquid slurry of metal onto the substrate. Some of these methods are subtractive, such as the print and etch where patterns are etched from a laminated copper foil, others are purely additive, such as the printing or ink jetting methods where conductor patterns are directly formed on the substrate, and still others are combinations of additive and subtractive. In addition to forming conductor patterns for the electrical circuitry, many have also sought to create passive devices, such as resistors and capacitors, on the substrate. Resistors and capacitors have long been utilized with success in circuits with ceramic substrates, and some have even modified this technology to incorporate it into circuitry on rigid glass reinforced polymer substrates, such as epoxy-glass and polyimide-glass. Adoption of passive devices on high volume, low cost, flexible film substrates has been less successful. Fabrication of printed electronic circuitry and devices using graphic arts technology has the potential to produce very inexpensive circuits in very high volumes. However, quality control of printed electronics during fabrication has been difficult, if not impossible, using high throughput graphics arts printing technology, due to the lack of on-press functional test capability. Conventional quality control techniques for measuring tolerances of resistors and capacitors utilize combinations of mechanical and electrical testing after the devices are completely fabricated. In the low volume factories of the past, this was acceptable, as process changes could be made before numerous off-specification parts were made. However, in the high volume world of the future, ‘after-the-fact’ testing will be financially disastrous, as errors during processing would create a large amount of defective product before the error was even detected. A more rapid means of measuring and testing printed electronic devices would be a significant contribution to the art.
The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
Before describing in detail embodiments that are in accordance with the present invention, it should be observed that the embodiments reside primarily in combinations of methods and apparatus components related to printed electronic devices that are formed by contact printing.
Accordingly, the apparatus components and methods 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 invention 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.
In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element. The terms “printed electronics” and “printed electronic device” are intended to include both active and passive devices such as capacitors, resistors, inverters, ring oscillators, transistors, etc. that are formed by contact printing one or more elements of the device on a substrate, in contrast to the discrete devices produced by, for example semiconductor technology on wafers or ceramic thick film firing techniques.
It will be appreciated that embodiments of the invention described herein may be comprised of one or more conventional materials or processes. Thus, methods and means for these functions have been described herein. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of using the measuring technique disclosed herein with minimal experimentation.
A method for determining the electrical value of printed electronic devices comprises contact printing a dielectric material on a substrate using a preset force. The substrate has a pressure sensitive material that comprises indicia that are optically responsive in direct proportion to the amount of force imparted by the contact printing step. The force of the contact printing step causes the indicia to form a pattern that is quantifiable to the amount of force. The pattern is then optically inspected and compared to one or more sets of previously made standards in order to quantify the amount of force that was used to contact print the dielectric material. The thickness of the printed dielectric material is then calculated based on the quantified force by comparing to another set of standards. The electrical value of the printed material can then be calculated based on the calculated thickness of the printed dielectric material, the surface area of the printed dielectric material, and the dielectric constant of the dielectric material.
In order to illustrate the invention, a method of printing capacitors on a film will now be illustrated. It should be understood that while this embodiment is provided to aid the reader in understanding the invention, it is not intended to be limiting, but is presented as one example of our invention. Referring now to
Referring now to
C=(E0×K×S)/T
where C is capacitance of the printed dielectric material, E0 is 8.8×10−12 farads per meter (vacuum permittivity), K is the dielectric constant of the printed dielectric material, S is the area of the printed dielectric material in square meters, and T is the calculated thickness of the printed dielectric material based on the measured force.
Referring now to
In summary, the electrical value of printed electronic devices can be indirectly determined by using optical inspection means to indirectly measure the amount of force used to contact print a dielectric material, then calculating the thickness of the printed material by referencing the calculated force. Once the thickness, area, and dielectric constant are known, the electrical value can be calculated.
In the foregoing specification, specific embodiments of the present invention have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. For example, one would also print a series of conductive patterns or circuit traces on the carrier substrate using silver-filled, carbon-filled, or an intrinsicaly conductive polymer ink, in any one of several conventional methods, to form resistors or capacitors in selected locations. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.
