1. Field of the Invention
The present invention relates to the mass production of thin, flexible electrical low-cost circuits. More particularly, the process according to the present invention aims at the super-mass production of flexible Radio Frequency [RF] planar resonant circuits for one way use and including inductive and capacitive components, as are commercially desired as marker means in Electronic Article Surveillance [EAS] systems, in Electronic Personnel Access Control [EPC] systems, in Electronic Anti-Counterfeit [EAC] systems, and in most modern Object Handling Control [OHC] systems, e.g. electronic document safe sysems, clinical supply systems, electronic flight baggage and ticket control systems, and the like.
The invention introduces the computerized nonstop super-mass production of such circuits, and breaks down prior art barriers in view of limits for custom designs of shape, face, and resonant properties of such circuits. Custom designs of circuits are easily layouted onscreen of a modern personal computer. The data obtained thereof are downloaded to the process line. Hopping custom circuit designs with ease is unprecedentedly introduced. Forming tools have been abandoned. As an exclusive longlife production tool electromagnetic wave energy is extensively used. The circuits may be washed and sewn and nicely go one way with a pretty face.
2. Descripton of the Prior Art
U.S. Pat. No. 3,913,219 (LICHTBLAU) describes a production process for the make of planar electrical circuits comprising a dielectric sheet and having an inductively reacting conductive spiral path made from an appropriate metal foil and bonded to one side of said dielectric sheet. Said spiral path terminates, at each end, via at least one connection means, into first and second conductive areas being in a mutually aligned opposite and spaced by said dielectric sheet, thus forming a discrete capacitor. Said capacitor and said conductive spiral thus cooperate to form an LC resonant circuit. The production method may be described by putting some light on the major problems encountering therewith, as follows. The production starts up with a trilayer compound material resulting from a difficult collamination process of two aluminum layers of widely differing thickness (typical 8 .mu.m and 50 .mu.m) with a polyethylene layer. The latter must exhibit very close tolerances in view of thickness (normally about of 25 .mu.m +/-5 .mu.m) and dielectric permittivity, and hence has to be produced off-line, in a special apparatus, at extra speed, and thus is expensive. First waste results between its shock cooled high density extrusion and its heated collamination between said aluminum layers, at a considerably low speed. Then, applying known roto-printing techniques, etching resist patterns are printed, in a mutual registration, on both faces of the compound and dried, at high speed. Due to the roto-printing technique, the print is of the fixed formatted type, which means, the circuit patterns repeat at a constant pitch or spacing on the circumference of the printing cylinder. Though printing is performed with a high repetitive register accuracy of the resist structures defining the resonator to be constructed, this repetitive registration is maintained only a very short time from the following reason. When etching, the entire processing web starts up shrinking, owing to strains frozen in the polyethylene during recrystallization in the early moment of its collamination with said aluminum layers aided by heat. These strains get active, once wide areas and spirally turn-to-turn spacings have been removed, and thus cancel any previously achieved registration on the previously nonetched web both in its along and across direction. Further, etching taken alone is a slow process step, since modern rapid etching techniques--due to their inherent poor overetch protection--cannot be utilized, from the following reason. Etching must take place on both faces of the compound simultaneously, meaning, that the etching of aluminum layers having a widely different thickness (e.g. 8 .mu.m and 50 .mu.m) should be finished right at the same time. Overetching and dropped-registration-waste is a result. Shrinking encounters the problem, that the endless processing web representing a plurality of resonant structures cannot be combined, as circuit's face, with an endless cover material preprinted with an individual outline per circuit repeating at a constant resonator pitch or space, since due to lost registration no precise alignment of a resonator and a preprinted circuit face to mate and cover each other can be maintained. Further, since the inconsistent multilayer construction of the fully finished circuit from other reasons can be printed merely asynchronously by low quality rubber-flex techniques, this known process neither yields standard circuits printed with a fixed print-to-resonator registration, nor yields circuits according to hopping an changing custom design specifications, e.g. including a super performance color print. Further problems encounter with that method, since immediately upon etching the processing web, due to its filigree shape, is most complicated to handle, to advance and to position, just in a state in which such should be easy and carried out quickly. Again waste is a result. For an improvement, it is not allowed to thicken the polyethylene layer for stabilization, otherwise the RF performance of resonators would dramatically drop whenever such circuit should be made as small as possible which is, however, a common desire. Further problems encounter with the need, that the two metal layers have to be contacted through said polyethylene layer's normal thickness of of 25 .mu.m. Such thru-contacts proved to be unreliable; "dead" circuits use already to appear among good ones when shipped from the factory. Chemical agents as being in worldwide use with the recreation of fashions and garments not only destroy these contacts. These agents dissolve and float off the roto-printable etchant resistive pattern, which is left back surplus in the circuit construction once etched. Hence, circuits of this make may even mediate or cause heavy degradations and deteriorations of suchlike treated fashions in a much later state, provided such circuits are made just for one way use for walking away with customer's buy. Moreover, though said polyethylene layer is considerable costly and its properties are essentially needed merely in a considerable small place of the entire resonator construction, this layer is most inefficiently wasted over the entire circuit area (wasted precision is wasted money). As an overall result, these problems and the restrictions for the finished product concluded thereof qualifies this method as non-applicable for making disposable one way RF marker circuits, which also serve for quite other functions, a variety thereof having been disclosed in more recent patent applications of applicant.
U.S. Pat. Nos. 4,482,874 (RUBERTUS & TAIT) and 4,598,276 (TAIT) describe a method of producing novel high efficiency marker devices the unique design scheme of which having been taught in U.S. Pat. No. 4,694,283 granted to applicant. This method is dedicated to a complex stamping routine which utilizes a most delicate domino stampling tool. It has a fixed design and requires steady performance control, service and exchange on elapse of its short lifetime. This means, that such production cannot be run continuously 24 hours/365 days a year, at minimum dead time. However, a minor advantage is obtained with this method over the one mentioned above, so far as the pitch or spacing between resonators may be influenced at some degree, however, by encountering complex mechanics along the production line, provided such resonators should be covered with a registered paper face on-line. However, owing to a limited dimensional precision of any cover material to join the endlessly produced resonator web, preprinting such cover material may not be applied without earning all the same lost-registration problems with the attempt to have individual resonator structures superpose in a perfect alignment individual face prints.
U.S. Pat. No. 4,658,264 (BAKER) also repeats the basic construction scheme of the planar stripline resonator as disclosed in applicant's U.S. Pat. No. 4,694,283. However, it is not taught how to assign to such resonator a precisely registered print on its usable outer face, or how to design such resonator for facilitating its fitting between most modern cover materials, for giving it even a tex-like appearance or the capability of being washed and sewn. Oppositely, this Patent centers merely on the task of how to fold over a substantially filigree and inconsistent substrate for a registered alignment of folded over portions with a precision of alignment sufficient enough, as has been reflcted in applicant's prior publications.
U.S. Pat. No. 4,369,557 (VANDEBULT) repeats major portions of the LICHTBLAU process, however, with an important distinction so far as the trilayer compound as a production carrier is exchanged for a dual layer one. Thus, etching of a constant thickness metal layer is carried out merely on one face of a thin and dimensionally unstable dielectric layer which, however, again and all the same has to serve for production carrier's function.
Consequently, all other problems and restrictions of the LICHBTLAU process are prefectly imported and maintained. Hence, that Patent does not teach how to produce one way RF marker circuits offering a modern cover face designed according to whatsoever customer's specifications.
European Patent Application No. 84104174.2 (SALAMONE, HOOVER & VANDEBULT) discloses a method of fabricating respective circuits by electrolytically depositing and growing up resonator structures. The process applies fixed format silk screen printing electrically conductive patterns on a thin dielectric film, as may be of polyester. Then, this film and patterns are subjected to a very slow electrolytic deposition routine. Since this method, too, does not yield a marketable product rather than mere (bare) resonators, it is also conflicted with the described lost-registration tragedy, so that this process also has to be considered as off-limits for the super mass production of RF marker circuits going both one way and customized, reading with a whatsoever pretty commercial face.
The present invention not only accomplishes the huge object of overcoming all of the above problems. It defines a new horizon for making mass marketable electrical one way circuits featuring custom designs to fill catalogs. Therefore, the present invention breaks with prior art methods, for defining a new reference standard of the state of the art, which becomes obvious from an impressive listing of objects of the invention as follows:
and