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US 5,291,178 AGranted
Film-type resistor assembly with full encapsulation except at the bottom surface
AssigneeCaddock Electronics, Inc.
InventorsMilton J. Strief, David L. Martin
Life of this patent
Estimating the term…
Abstract
A film-type resistor having a high power rating and a relatively low manufacturing cost. The structural strength of the resistor is derived primarily from a molded body that covers both a film-coated substrate and a heatsink. The heatsink, to which the substrate is bonded in high thermal-conductivity relationship, has an exposed flat bottom surface of relatively large area.
Claims32
A film-type power resistor combination, which comprises:
- (a) an elongate flat metal heatsink having substantially parallel upper and lower surfaces,
- (b) a flat ceramic substrate having substantially parallel upper and lower surfaces, said substrate having a size and shape so related to those of said heatsink that when said substrate is in a predetermined position with its lower surface parallel to and adjacent both one end portion and an intermediate portion of said upper heatsink surface, and with said lower substrate surface overlapping said upper heatsink surface, the following relationship exist:
- (1) the outer end portion of said upper heatsink surface is outwardly spaced from said lower substrate surface, and
- (2) a substantial portion of said upper heatsink surface, and which is adjacent said other end portion of said upper heatsink surface, extends outwardly from beneath said lower substrate surface,
- (c) means to effect a high thermal-conductivity bond between said lower substrate surface and said upper heatsink surface when said substrate is in said predetermined position, to thereby hold said substrate in said predetermined position and in high thermal-conductivity relationship to said heatsink,
- (d) an electrically resistive film provided on said upper surface of said substrate,
- (e) termination pins or leads connected physically and electrically to spaced-apart portions of said film and extending away from said substrate for connection into an electric circuit, and
- (f) a molded body of synthetic resin encapsulating said substrate, the inner portions of said pins, and at least substantially the entire upper surface of said heatsink,
- said lower heatsink surface being exposed so as to be mountable in flatwise engagement with the upper surface of a chassis, said molded body being thick to thereby provided structural strength to the combination, as well as environmental protection for said resistive film, said heatsink being a separate metal element that is not integral with any of said termination pins.
6 more elements
A film-type power resistor combination, which comprises:
- (a) an elongate flat metal heatsink the surface area of which may be considered as divided into a first one-third at one end portion thereof, a second one-third at the other end portion thereof, and a third one-third therebetween,
- said heatsink being thin but having sufficient thickness that when downward pressure is applied to said first one-third of said surface area in a mold, said second and third one-thirds of said area will bear down on a flat bottom wall of the mold cavity in flatwise engagement therewith,
- (b) a flat ceramic substrate mounted over and adjacent the majority of the top surface of said heatsink, generally above at least said second and third one-thirds of said area,
- (c) means to effect a high heat-transmission bond between the bottom surface of said substrate and said top surface of said heatsink,
- (d) first and second trace and pad means provided on the top surface of said substrate in spaced relationship from each other,
- (e) an electrically resistive film provided on said top surface of said substrate and extending between said first and second trace and pad means,
- (f) termination plus connected respectively to said first and second trace and pad means and extending outwardly from said substrate, and
- (g) a rigid synthetic resin body molded around substantially all portions of said above-recited elements excepting said bottom surface of said heatsink and the outer portions of said termination pins,
- said synthetic resin body having substantial thickness sufficient that, in combination with said heatsink and substrate and bond means, it makes said resistor rigid,
- said heatsink being a separate metal element that is not integral with any of said termination pins.
7 more elements
A film-type power resistor combination, which comprises:
- (a) a flat metal heatsink,
- (b) a flat ceramic substrate mounted over and substantially parallel to at least the majority of the top surface of said heatsink,
- (c) first and second trace and pad means provided on said substrate,
- said first and second trace and pad means being spaced apart from each other,
- (d) an electrically resistive film provided on said substrate and extending between said first and second trace and pad means,
- (e) means to effect a high heat-transmission relationship between said resistive film and said heatsink,
- (f) termination pins bonded respectively to said trace and pad means and extending outwardly from said substrate, and
- (g) a synthetic resin body molded around substantially all portions of said above-recited elements excepting the bottom surface of said heatsink and the outer portions of said termination pins,
- said synthetic resin body having substantial thickness sufficient that, in combination with said heatsink and substrate, it makes said resistor strong,
- said synthetic resin body having a bolt hole therethrough for use in connection of said resistor to a chassis,
- said heatsink being a separate metal element that is not integral with any of said termination pins.
8 more elements
Dependencies are inferred from the claim text.