Browse Prior Art Database

MINIATURE HIGH POWER TRIM POTENTIOMETER

IP.com Disclosure Number: IPCOM000006232D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2001-Dec-17
Document File: 2 page(s) / 67K

Publishing Venue

Motorola

Related People

Robert Wagner: AUTHOR

Abstract

For tuning or trimming purposes, new RF module designs require surface-mountable variable resistors which are capable of dissipating one Watt of power at temperatures equal to or exceeding 100 degrees Centi- grade.

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MOTOROLA INC. Technical Developments Volume 13 July 1991

MINIATURE HIGH POWER TRIM POTENTIOMETER

by Robert Wagner

  For tuning or trimming purposes, new RF module designs require surface-mountable variable resistors which are capable of dissipating one Watt of power at temperatures equal to or exceeding 100 degrees Centi- grade.

  Presently, the smallest commercially available snr- face-mount trim potentiometers are capable of only one tenth of a Watt power dissipation at 70 degrees Centigrade, derating to zero power capability at 120 degrees Centigrade.

  This publication describes a method that increases the power dissipation capability of variable resistors of the type often used on RF printed circuit boards (PCB's) by a factor of up to ten times.

The increase in power dissipation capability of these variable resistors is obtained by adding metal

leads and a metal heat sink tab that is subsequently soldered over a plated hole that passes through the printed circuit board.

  One such arrangement is shown in FIGURE 1. The leads and heat sink tab remove heat during opera- tion. The plated hole and the attaching solder that fills it, provide a thermal path from the heat sink tab to a heat sink attached to the backside of the printed cir- cuit board.

  Trim potentiometers that were previously rated at a tenth of a Watt at 70 degrees Centigrade or zero Watts at 120 degrees Centigrade, can now be conser- vatively rated at a half Watt at 120 degrees Centigrade using this techni...