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Thermistor Braze and Reflow Procedure

IP.com Disclosure Number: IPCOM000039069D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Interrante, M: AUTHOR [+4]

Abstract

A procedure has been developed for using a new gold-tin alloy braze to attach thermistors to pads on substrates in thermal conduction modules (TCMs). A reflow procedure uses a continuous-wave CO2 laser to reflow the thermistor braze paste during rework procedures. In the manufacture of semiconductor modules, thermistors with platinum wiring have to be attached to pads on the TCM substrate. Prior methods used ultrasonic bonding which required heavy gold plating. A new brazing material 82/18 Au/Sn has characteristics which enable it to be bonded to the thermistor pads during pin braze to provide a suitable bonding material for the platinum thermistor wire.

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Thermistor Braze and Reflow Procedure

A procedure has been developed for using a new gold-tin alloy braze to attach thermistors to pads on substrates in thermal conduction modules (TCMs). A reflow procedure uses a continuous-wave CO2 laser to reflow the thermistor braze paste during rework procedures. In the manufacture of semiconductor modules, thermistors with platinum wiring have to be attached to pads on the TCM substrate. Prior methods used ultrasonic bonding which required heavy gold plating. A new brazing material 82/18 Au/Sn has characteristics which enable it to be bonded to the thermistor pads during pin braze to provide a suitable bonding material for the platinum thermistor wire. The braze has the capability of holding the thermistor wire during chip join cycles at a maximum temperature of about 350~C and yet reflow during pin braze with a maximum temperature of about 385~C. It provides a bond that is mechanically and metallurgically superior to that achieved with ultrasonic bonding techniques and makes it possible to eliminate heavy Au plating methods. When reworking the TCM to remove defective transistors, it is necessary to heat the connections so as to remove the thermistor wires and reflow the paste to accept the new wire. Infrared and thermal conduction methods cannot raise the temperature high enough or fast enough without the possibility of pad damage. The proposal also suggests the use of a continuous-wave CO2 laser tool which may be pulsed a...