Collaborative cleaning process innovations from managing experience and learning curves
come from the mixture of solvating
materials that rapidly dissolve resin and
rosin structures. Low reactivity improves
the cleaning rate but does not cause
compatibility concerns on components,
board laminates, flex, anodized coatings,
plastics and metallic’s. Wetting lowers
surface tension effects. Finally, minor
ingredients control foaming and protect
solder joint finishes. Innovative designs
run at lower wash bath concentrations
ranging from 10-13%. The aqueous design
Figure 4. Aqueous cleaning material design options. uses very low vapor pressure materials
that condense and return before being
evaluated out the exhaust stack, thus
rate. The benefits of highly reactive may result in higher consumption.
consuming very low levels of cleaning fluid
aqueous cleaning fluids are lower
over time. Users report consumption at
operating concentration and aggressive Best in class aqueous cleaning
less than 50% that of traditional aqueous
interaction with rosin, resin and weak material for cleaning under low
cleaning materials.
organic acids. The tradeoffs of highly standoff components : Cleaning process
reactive aqueous cleaning fluids are optimization requires a balance of
aqueous inline cleaning machine
materials compatibility, short bath life chemical and mechanical effects. The
innovations
and lower effectiveness on low-residue job of the cleaning material is to remove
The cleaning machine design is equally
flux residues. flux residue and ionic contaminants. As
important. Fluid management is critical
1. Aqueous mild reactivity: Product previously discussed, aqueous cleaning
in maintaining an economic cleaning
contains greater than 10% but less material designs contain reactive materials
process. Individual module containment
than 30% active free amine reactive at various concentration levels. On certain
and specifically with the wash chemistry
materials. Mild reactivity formulation flux types, higher reactivity increases the
is essential. Fluid delivery is critical for
designs improve rate using higher static cleaning rate but can cause other
penetrating and rapidly breaking the flux
solvency combined with reactivity. The issues. When cleaning flux residue under
dam under low standoff components.
benefits of mild reactivity aqueous low standoff components, longer wash
Air management is critical to reducing
cleaning fluids are improved material time is needed. Highly reactive cleaning
chemical odors in the workspace while
compatibility, longer bath life and materials create several compatibility
minimizing the amount of wash fumes
greater effectiveness on low-residue concerns in the form of solder joint attack,
exhausted from the machine. Fluid storage
flux residues. The tradeoffs are lower anodized aluminum attack, dry film solder
is critical for long wash bath life. Fluid
bath life and lower effectiveness on mask removal, part marking removal,
control is critical in maintaining the
higher molecular weight resins used in component attack, polymer/adhesive
proper wash bath concentration within the
lead-free flux compositions. attack and a range of other issues. Highly
cleaning process tolerance.
2. Aqueous low reactivity: Product reactive cleaning materials saponify rosin,
Cleaning equipment design issues in
contains less than 10% active free which can create a foam condition as the
any of these areas can and will upset the
amine reactive materials. Low reactivity wash bath loads.
cleaning process over time. Issues such
formulation designs improve rate using Best in class cleaning materials
as high wash consumption, steam out of
a combination of solvating materials exhibit other important properties. The
the machine, foaming in the wash and or
combined with reactivity. The benefits vapor pressure of each material used in
rinse, exhaust losses and poor cleaning all
of low reactivity aqueous cleaning the compositional make-up influences
result from an imbalance caused by one or
fluids are long bath life, good material evaporative loss rates. The dissolution rate
more of these factors. Process issues may
compatibility and highly effective on on higher molecular weight resin structures
not show up when the machine is initially
both eutectic and Pb-free flux residues. used in low residue and lead-free flux
charged with cleaning chemistry and
Aqueous low reactivity provides compositions influences the static cleaning
started up but slowly creep in over time.
best in class technology due to high rate. The rate of cleaning material solvency
Lack of process optimization results in
solvating power and excellent material in water can influence the cleaning rate
higher defect rates, which typically render
compatibility. and defoaming properties. The cleaning
white residue formation and unacceptable
3. Aqueous neutral: Product contains material wetting force is critical to
levels of ionic residues on the surface and
less than 2% active free amine penetrating low standoff gaps. Properly
under component gaps.
reactive materials. Aqueous neutral designed, the cleaning material rapidly
Fluid Delivery: To improve cleaning
formulation designs improve rate using dissolves rosin/resin structures, wets low
under low standoff components, research
solvency. The benefits of aqueous standoff gaps, inhibits solder joint attack,
data indicates that fluid flow, pressure
neutral formulation designs are very overcomes compatibility concerns, works at
at the board surface, directional forces
good materials compatibility, long bath low concentrations and provides long bath.
and time in the wash improve the process
life and excellent cleaning on a broad Aqueous Low Reactivity cleaning
cleaning rate. The wash section of the
range of flux materials. The tradeoffs material designs provide improved cleaning
cleaning machine is highly important.
of aqueous neutral formulation designs under low standoff components. The
Findings indicate that flux not adequately
are higher wash concentration that driving forces that improve performance
removed in the wash will not be removed
28 – Global SMT & Packaging – October 2009
www.globalsmt.net
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