Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1993-07-29
1994-10-25
Ryan, Patrick J.
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
428901, 428405, 428327, 428325, 428331, 428421, 361750, B32B 300, B32B 700
Patent
active
053587758
ABSTRACT:
A high dielectric constant (K'.gtoreq.4), low thermal coefficient of dielectric constant (TCK'.ltoreq.150 ppm/.degree. C.) electrical substrate material comprises a fluoropolymer (preferably PTFE) filled with particulate ceramic material (powder) which exhibits low loss, comparatively high K' and acceptable TCK'. Examples of such ceramic powders include "class 1" capacitor ceramics. In accordance with an important feature of this invention, it has been discovered that it is insufficient to use only a low TCK' filler (e.g., class 1 capacitor ceramic powder) in the fluoropolymeric binder in order to achieve the desired TCK'. Instead, it has been discovered that the coefficient of thermal expansion (CTE) of the composite must also be sufficiently low (e.g.,.ltoreq.35 ppm/.degree. C.) to result in a composite which consistently maintains a low TCK'. This low CTE is achieved by adding one or more additional particulate ceramic fillers. These additional fillers have a low CTE and are of a composition which differs from the low TCK' fillers. Examples include silica and alumina. In accordance with still another important feature of this invention, the particle size distribution of the particulate ceramic fillers are carefully controlled to achieve low porosity (e.g.,.ltoreq.15% when the filler content exceeds about 50 volume %).
REFERENCES:
patent: 4241132 (1980-12-01), Pratt
patent: 4849284 (1989-07-01), Arthur
patent: 4855266 (1989-08-01), Burn
patent: 4870377 (1989-09-01), Brown
patent: 4996097 (1991-02-01), Fischer
Jewik Patrick
Rogers Corporation
Ryan Patrick J.
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