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Resistive Wire Thermode for Soldering Surface-Mount Components

IP.com Disclosure Number: IPCOM000102156D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 41K

Publishing Venue

IBM

Related People

Shi, LT: AUTHOR [+3]

Abstract

Disclosed is the design of a thermode using resistive wire for soldering and rework of surface-mount components.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 79% of the total text.

Resistive Wire Thermode for Soldering Surface-Mount Components

       Disclosed is the design of a thermode using resistive
wire for soldering and rework of surface-mount components.

      The distinct design feature of the resistive wire thermode is
the use of a coaxial wire for heating.  The coaxial wire
(THERMOCOAX*) incorporates a nichrome wire as a core insulated by a
layer of MgO in an inconel sheath.  The wire is bent into shape in a
die and then brazed to a stainless steel holder in such a way that
the co-planarity of the wire is guaranteed by the flatness of the
holder.  A vacuum chuck is built into the stainless steel holder such
that the leads on the component can be sufficiently contacted by the
resistive wire.  Since the coefficient of thermal expansion of
inconel is very close to that of the stainless steel, it is not a
concern that the thermal fatigue cracking will occur between the wire
and the holder.  In addition, the portion of the wire used as the
power connection is wrapped in a ceramic sleeve in order to avoid hot
spot and breakage due to thermal fatigue.

      It is verified that the temperature distribution of the
resistive wire thermode is quite uniform.  The temperature ramping
and cooling of the thermode can be achieved within very short period
of time as a result of highly local heating and effective heat sink
induced by the stainless steel holder.  The temperature cycle (or
history) of the thermode can be controlled by a fe...