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EDTA-Glycerol Flux for Molten Solder Redressing

IP.com Disclosure Number: IPCOM000103468D
Original Publication Date: 1990-Dec-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 1 page(s) / 47K

Publishing Venue

IBM

Related People

Nguyen, DQ: AUTHOR [+2]

Abstract

Conventionally, fluxes have been used during solder touch-up, redressing and rework operations, or even prior to component attachment as in the case of Tape Automated Bonding (TAB) devices. The flux minimizes oxidation of the solder and enables removal of icicles and leveling of solder crowns prior to rework.

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EDTA-Glycerol Flux for Molten Solder Redressing

      Conventionally, fluxes have been used during solder touch-up,
redressing and rework operations, or even prior to component
attachment as in the case of Tape Automated Bonding (TAB) devices.
The flux minimizes oxidation of the solder and enables removal of
icicles and leveling of solder crowns prior to rework.

      However, when fine pitch components are encountered, for
example, 0.016" pitch TAB devices with 0.010" wide solder pads, it is
extremely important that sufficient and uniform quantity of solder be
added so that the solder joints of the reattached component have good
integrity. Traditionally, the redressing has been accomplished using
cored solder wire in conjunction with a liquid flux, which may be RMA
based or water soluble.  A soldering iron is used to form a molten
ball of solder and the fluxed pads redressed.  We have found that a
mixture of 0.24 grams of ethylene diamine tetra-acetic acid (EDTA) in
5 milliliters of glycerol serves as an excellent flux in being able
to provide higher solder volume with better uniformity for the
redressing operation, compared to an RMA flux.  This is especially so
on copper pads that are badly oxidized.  For example, on 0.010" wide,
0.080" pads (0.016" pitch), the EDTA- glycerol flux provides 0.00115"
average solder crown height (standard deviation 0.00017"), compared
to 0.00073" for the RMA flux (standard deviation 0.00026" - sample
sizes 30).

      Using...