Attachment of leads to precision resistors
AssigneeVishay Intertechnology, Inc.
InventorsKenneth R. Lewis, Anthony C. Meenan
Life of this patent
Estimating the term…
Abstract
A precision resistor has a thin resistive foil cemented to a much thicker rigid substrate. The foil has formed therein a pattern defining the resistive path between terminal pads. Copper leads can be spot-welded directly to these pads without damage to the junction. To that end, apertures are provided through the terminal pads, through which cement softened by the spot-welding heat can locally expand and gas evolved under pressure can escape, all without adversely affecting the junction and without substantial lifting of the terminal pads from the substrate.
Claims25
In a precision resistor which includes a thin resistance foil cemented to a much thicker rigid substrate, and a resistive path between terminal pads defined in the cemented foil, the improvement comprising:
- at least one aperture located within the confines of each cemented pad and penetrating through the entire thickness of the foil.
In a precision resistor which includes a thin resistance foil cemented to a much thicker rigid substrate, and a resistive path between terminal pads defined in the foil, the improvement comprising:
- a plurality of apertures located within the confines of each pad and penetrating through the entire thickness of the foil,
- a flat copper connecting lead lying upon and covering a portion of each pad and spot-welded to the foil of the pad,
- at least some of the apertures in the terminal pads being not covered by the flat connecting leads lying upon the pads.
In a precision resistor which includes a thin resistance foil cemented to a much thicker rigid substrate, and a resistive path between terminal pads defined in the foil, the improvement comprising:
- a plurality of apertures located within the confines of each pad and penetrating through the entire thickness of the foil,
- a flat copper connecting lead lying upon and covering a portion of each pad and spot-welded to the foil of the pad,
- the apertures being arranged generally along the periphery of each pad.
A subassembly for a precision resistor, said subassembly comprising
- a thin resistance foil connected to a much thicker rigid substrate, said foil having defined therein a resistive path between terminal pads, and
- a plurality of apertures located within the confines of each pad and penetrating through the entire thickness of the foil.
A precision resistor manufactured by the method which comprises the steps of:
- defining in a thin foil of resistance material a resistive path extending between two terminal pads,
- defining within the confines of each terminal pad a plurality of apertures extending through the thickness of the pad,
- cementing the foil to a much thicker substrate of a rigid material, before or after defining the resistive path and terminal pads,
- applying an overcoat at least to the resistive path,
- applying a connecting lead to the surface of such pad, and
- spot-welding the leads to the pads under such conditions that the heat of the spot-welding softens the cement between foil and substrate and causes gas at high pressure to evolve between foil and substrate, and the apertures being proportioned so that the softened cement expands locally and the gas escapes through the apertures,
- whereby there is no substantial lifting of the pads from the substrate as a result of the spot-welding.
The method of manufacturing a precision resistor which comprises the steps of:
- defining in a thin foil of resistance material a resistive path extending between two terminal pads,
- defining within the confines of each terminal pad a plurality of apertures extending through the thickness of the pad,
- cementing the foil to a much thicker substrate of a rigid material, before or after defining the resistive path and terminal pads,
- applying an overcoat at least to the resistive path,
- applying a connecting lead to the surface of each pad, and
- spot-welding the leads to the pads under such conditions that the heat of the spot-welding softens the cement between foil and substrate and causes gas at high pressure to evolve between foil and substrate, and the apertures being proportioned so that the softened cement expands locally and the gas escapes through the apertures,
- whereby there is no substantial lifting of the pad from the substrate as a result of the spot-welding.
Dependencies are inferred from the claim text.