Electrical resistors – Incased – embedded – or housed – Flattened resistance element between flat layers
Reexamination Certificate
1999-10-15
2001-11-13
Easthom, Karl D. (Department: 2832)
Electrical resistors
Incased, embedded, or housed
Flattened resistance element between flat layers
C338S309000, C338S320000, C029S620000, C174S259000, C427S096400, C427S103000
Reexamination Certificate
active
06317023
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to an improved method of embedding thick film passive components on an organic layer wherein a flexible metallic substrate has a conductive paste underprint applied thereon.
BACKGROUND OF THE INVENTION
Passive components today consist of a carrier with built in passive compositions usually derived from resistor or capacitor thick film technology and terminated by metal conductors. The components are mounted onto a printed wiring board (PWB) surface one at a time with pick and place equipment, and connected electrically to the circuit by one of several complex processes involving adhesives, fluxes, solder paste, and/or wave soldering or reflow.
As the demand for miniaturizing electronic devices increases, both circuit density and the density of components per unit area have dramatically increased.
The number of components has risen exponentially necessitating the shrinking of component size. Since the design of smaller, denser boards is approaching the practical limit for today's technology, circuit designers have maximized real-estate and cannot add components unless they become much smaller, or as an alternative, buried within the inner layers, i.e., vertical stacking of components.
Early versions of the embedded passive panels, as found in Japanese patent application kokoku H2-153589, had the passive components printed directly onto a metal foil. This method had drawbacks, such as adhesion problems with the resistors and low capacitance and high dissipation factor with the capacitors. The present invention achieves success with adhesion by the application of a paste underprint that was applied to the metal foil before the printing of the passive components. Therefore, the present invention utilizes an improved method of forming passive components using present cermet thick film technology for low cost embedded component formation on organic substrates.
SUMMARY OF THE INVENTION
The present invention is directed to a method of embedding thick film passive components comprising the following steps:
A. applying as an underprint a conductor paste onto a flexible metallic substrate;
B. firing the article found in step A.;
C. applying at least one resistor paste onto the underprint;
D. firing the article found in step C.;
E. applying the fired paste side of the article found in step D. onto at least one side of an organic layer which is at least partially coated with an adhesive layer wherein the fired paste side of the article is embedded into the adhesive layer.
The present invention is further directed to a method of embedding thick film passive components comprising the following steps:
A. applying as an underprint a first conductor paste onto a flexible metallic substrate;
B. firing the article found in step A.;
C. applying at least one dielectric paste onto the underprint;
D. firing the article found in step C.;
E. applying a second conductor paste onto the fired pastes;
F. firing the article found in step E.;
G. applying the fired paste side of the article found in step F. onto at least one side of an organic layer which is at least partially coated with an adhesive layer wherein the fired paste side of the article is embedded into the adhesive layer.
Employing conventional print/etch processing to pattern the conductors may then complete the above methods.
Resistor and capacitor pastes can in principle be printed together, as well as multiple grades of resistor paste and multiple grades of capacitor pastes, as long as all pastes use the same furnace profile in the firing step.
REFERENCES:
patent: 4180608 (1979-12-01), Del
patent: 4204187 (1980-05-01), Kakuhashi et al.
patent: 4724040 (1988-02-01), Iwasa
patent: 5263243 (1993-11-01), Taneda et al.
patent: 5473118 (1995-12-01), Fukutake et al.
patent: 5557843 (1996-09-01), McKenney et al.
patent: 5652055 (1997-07-01), King et al.
patent: 5781100 (1998-07-01), Komatsu
patent: 0 859 705 A1 (1998-10-01), None
patent: 2-153589 (1990-06-01), None
patent: 98/39784 (1998-09-01), None
E. I. Du Pont de Nemours and Company
Easthom Karl D.
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