Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
1998-04-14
2001-09-04
Paladini, Albert W. (Department: 2841)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C313S494000, C313S521000, C428S690000
Reexamination Certificate
active
06284983
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a printed circuit board comprising one or more opto-electronically active luminous elements on the basis of electroluminescent systems, which elements can be made to emit light by applying a suitable supply voltage, thus converting passive printed circuit boards for interconnecting components into active multifunctional printed circuit boards, and the invention also relates to the application and method of manufacturing such a printed circuit board.
Thus, the invention relates to printed circuit boards with electroluminescent luminous fields, which are made to emit light upon application of a suitable voltage and frequency.
To manufacture electroluminescent arrangements by means of known printing techniques, electroluminescent coloring substances are known which are generally prepared on the basis of inorganic substances, such as, in particular, highly pure ZnS, CdS, Zn
x
Cd
1−x
S, etc., compounds of the II and VI groups of the periodic system, which are customarily doped or activated with Cu, Mn, Ag, etc. Customary colors include yellow, green, greenish blue, bluish green and white. In accordance with the state of the art, such electroluminescent pigments, whose diameters range typically from 15 &mgr;m to 60 &mgr;m, are admixed in micro-encapsulated or non-encapsulated form with the various printing dyes, while taking into account the specific hygroscopic properties of the ZnS pigments. The binding agents used adhere well to so-called conductive ITO films (Indium-Tin-Oxide films), they are good insulators, they enhance the dielectric properties and hence improve the dielectric strength at high electric field intensities. The binding agents should additionally exhibit a good water-vapor resistance in the cured state, protect the phosphor pigments and extend the service life.
Customarily, such electroluminescent dyes, which are commonly also referred to as phosphor pastes, are applied to transparent synthetic-resin foils or glasses by means of screen printing or other coating methods such as spread coating, roller coating, etc. The synthetic-resin foils, etc., comprise a substantially transparent electroconductive coating serving as the electrode for the viewing side. Subsequently, the dielectric and the rear-side electrode are manufactured by means of printing and/or lamination techniques. Such an electroluminescent arrangement is known, for example, from DE-A-44 30 907.
Often the order of the manufacturing process is reversed, as described, for example, in DE-A-43 19 441, in which first the rear-side electrode is manufactured or use is made of a rear-side electrode in the form of a metallized foil on which the dielectric is applied or is already present thereon in the form of a coating. Subsequently, the phosphor paste and the transparent, electroconductive upper electrode is provided, for example, in the form of an ITO paste. Customarily, such a system is further covered with a transparent covering foil, thus protecting it against water vapor and mechanical damage.
Customary ITO-paste coatings (or also coatings of tin oxide, etc.) which are provided by screen printing have the advantage that they can be provided in almost any desired shape, however, they have the disadvantage, compared to vapor-deposited or sputtered transparent and electroconductive films, that their optical transparency is smaller and their surface conductivity of generally several 100 Ohm per square (&OHgr;/▪) is substantially smaller compared to several 10 Ohm per square in the case of ITO-polyester foils and a few Ohm per square in the case of ITO-coated glasses, whereby in the case of glasses, additionally, pastes can be used, for example In
2
O
3
/SnO
2
, which must be fired at temperatures above 500° C., leading to an optical transparency beyond 95% at a film thickness of only 0.25 &mgr;m, and a conductivity in the case of a single coating of 500 to 1000 Ohm per square.
SUMMARY OF THE INVENTION
It is an object of the invention to manufacture, in a cost-effective manner, a multifunctional printed circuit board comprising integrated opto-electronic components, which demonstrates a long service life, a high luminous power and functionality at the available current-supply conditions, and integration in available PCB-manufacturing processes should be possible.
This object is achieved by an arrangement as described in the characterizing part of claim
1
, and by a method of manufacturing this arrangement as described in the characterizing part of claim
6
.
In the present case, use is made of methods and processes from the printed circuit board industry, in particular the screen-printing technique for manufacturing so-called single-sided, double-sided and multilayer printed circuit boards. The customarily used materials for the printed circuit boards, i.e. so called copper-clad laminates of the types XPC, FR-1, FR-2, FR-3, FR-4, CEM-1 to -3, polyimide foils as well as fleeces and bendable and flexible foils constitute the base substrate.
The base electrode for the luminous field as well as the connecting electrode for the transparent upper-side electrode (cover electrode) are generally formed by structuring of the typically 17, 35 or 70 &mgr;m thick copper foil. The copper foil can be provided with any desired structure by means of customary etching processes. To manufacture the dielectric use can be made of suitably insulating and, in general, properly reflecting screen-printing dyes, however, in particular of so-called solder-stop lacquers which, in the manufacture of the printed circuit board, are provided anyway to protect the fully etched conductor paths. In this connection, it has been found that 1-component UV-curing lacquers as well as 2-component thermo-curing lacquers can very suitably be used for more exacting applications.
To obtain a high dielectric strength, use is customarily made of two printing processes in which different sieves are employed, consequently, it is alternatively possible to employ combinations of semi-transparent and pigmented (for example white) or properly reflecting screen-printing dyes/solder-stop lacquers. The dielectric strength of such lacquers is approximately above 30 volt per micrometer of film thickness (typically 100 V/&mgr;m), so that in the case of customary film thicknesses in the range from 15 to 25 &mgr;m in the cured state, a sufficient dielectric strength would already be obtained by using one insulating film. However, for process, function and service life-related reasons, in general, two films are provided.
In a special embodiment, use may alternatively be made of photosensitive or photostructurable solder-stop lacquers which are applied by means of screen printing or curtain coating to obtain a high-quality, continuous, thin dielectric film having the highest possible dielectric strength.
Customarily, the electroluminescent dyes (phosphor pastes) are provided by screen printing and the desired geometries and colors can be set graphically. To achieve special color effects, use can be made, on the one hand, of pigmented, translucent and graphically formed masks and, on the other hand, of specially prepared pastes admixed with, for example, daylight luminous dyes or alternatively further luminescent pigments to achieve an appropriate emission spectrum. Optionally, these pigments can also be introduced into the transparent protective film.
The manufacture of the upper-side electrode (cover electrode) also typically takes place by means of screen printing on the phosphor paste. Customarily, use is made of so-called ITO pastes, which can be thermally cured already at relatively low temperatures, for example, of 120° C. and yield an optical transparency in the range from 70 to 85%. In the case of relatively small surface areas or small longitudinal dimensions, the electrical connection can only be made on one side on a copper connecting electrode from which, of course, the oxide film should be removed. If the luminous fields are more complex or comprise a larger surface area, customarily a so-cal
Lutschounig Ferdinand
Starzacher Andreas
AIK Electronics Austria GmbH
Paladini Albert W.
Vigil Thomas R.
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