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Method for Trimming Polymer Thick Film Resistors on Dielectric on Thermal Conductor Substrates

IP.com Disclosure Number: IPCOM000062495D
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Mace, EW: AUTHOR [+2]

Abstract

A packaging technology for power supplies, Dielectric on Thermal Conductor (DOTC) uses copper-metallized polyimide as a substrate. The polyimide is adhesively bonded to an aluminum heat sink which sinks the heat generated by the power-dissipating elements of the supply. A large percentage of the heat is generated by the several power resistors required by the supply design. The aluminum heat sink mentioned above provides a common heat sink for all the resistors as well as the other power-generating elements and eliminates individual heat sinks, thereby reducing system cost. Economic use of DOTC substrates requires use of integral power resistors. Present methods of screening these resistors do not consistently produce resistors of sufficiently low tolerance to attain adequate manufacturing yields.

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Method for Trimming Polymer Thick Film Resistors on Dielectric on Thermal Conductor Substrates

A packaging technology for power supplies, Dielectric on Thermal Conductor (DOTC) uses copper-metallized polyimide as a substrate. The polyimide is adhesively bonded to an aluminum heat sink which sinks the heat generated by the power-dissipating elements of the supply. A large percentage of the heat is generated by the several power resistors required by the supply design. The aluminum heat sink mentioned above provides a common heat sink for all the resistors as well as the other power-generating elements and eliminates individual heat sinks, thereby reducing system cost. Economic use of DOTC substrates requires use of integral power resistors. Present methods of screening these resistors do not consistently produce resistors of sufficiently low tolerance to attain adequate manufacturing yields. Resistor trimming is therefore a requirement if polymer thick film resistors are to be used on these substrates. A substrate thickness of two mils is chosen as a compromise between providing a reasonable thermal resistance between the elements mounted on the substrate and the heat sink, breakdown voltage required by safety considerations (includes safety factor), and ease of manufacturing. Power supplies require voltage breakdown between primary and secondary circuits of approximately 4000 volts, which is provided by a one-mil thickness (minimum) of polyimide. The trimming tec...