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Removal of Solubilized Contaminants From Beneath Components With Low Stand-Off Heights Using High Pressure Air Knives During Aqueous Post Wave Solder Cleaning

IP.com Disclosure Number: IPCOM000102708D
Original Publication Date: 1990-Dec-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 3 page(s) / 131K

Publishing Venue

IBM

Related People

Griffin Jr, AJ: AUTHOR

Abstract

Disclosed is an enhancement to aqueous cleaners currently used in the manufacture of printed circuit board assemblies which use surface mount components with low stand-off heights. The addition of or enhancement of air knives after each cleaning stage during aqueous post wave solder cleaning can be used to displace the aqueous cleaning medium, with or without surfactants, and its solubilized contaminants from beneath components with low stand-off heights. In doing so, subsequent sprays or wash cycles can be made more efficient by allowing fresh solution to come into contact with residual contaminant and, therefore, increase the solubility of contaminant in the small volume of solution which penetrates beneath components with low stand-off heights.

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Removal of Solubilized Contaminants From Beneath Components With Low Stand-Off Heights Using High Pressure Air Knives During Aqueous Post Wave Solder Cleaning

       Disclosed is an enhancement to aqueous cleaners currently
used in the manufacture of printed circuit board assemblies which use
surface mount components with low stand-off heights.  The addition of
or enhancement of air knives after each cleaning stage during aqueous
post wave solder cleaning can be used to displace the aqueous
cleaning medium, with or without surfactants, and its solubilized
contaminants from beneath components with low stand-off heights.  In
doing so, subsequent sprays or wash cycles can be made more efficient
by allowing fresh solution to come into contact with residual
contaminant and, therefore, increase the solubility of contaminant in
the small volume of solution which penetrates beneath components with
low stand-off heights.

      Electrical functionality and reliability of fine-pitch surface
mount components can adversely be affected by ionic contaminants
present on the surface of hybrid surface mount assemblies.  In
particular, highly activated water-soluble flux residues are left
underneath component packages with low stand-off heights as a result
of marginal aqueous post wave solder cleaning processes.  Currently,
aqueous cleaners take advantage of air knives only between cleaning
stages in order to prevent 'dragout' of contaminated solution from
previous 'dirty' stages to the subsequent 'cleaner' stage. However,
it should be emphasized that the air knives are not designed to
remove or displace the cleaning solution and its solubilized
contaminants entrapped beneath components, they are only used to keep
excess solution from carrying over to the next cleaning stage.
Implementation and design optimization of air knives for the express
purpose of displacing cleaning solution and its solubilized
contaminants from beneath components with low stand-off heights would
therefore improve the reliability of products which use these
components by improving cleanability of the current aqueous post wave
solder cleaning process.

      The problem with current cleaning processes can best be
described with the aid of a diagram.  Figure 1 is a schematic
representation of how entrapped flux residue can get past a cleaning
stage.  The flux can get beneath the component during the fluxi...