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Handbook of Solvents - George Wypych - ChemTech - Ventech!

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908 Martin Hanek, Norbert Löw, Andreas Mühlbauer<br />

Non-polar and organic residues are removed by contact with the hydrophobic or “solvent-like”<br />

phase. 12<br />

No specialized equipment is needed to handle microphase cleaning agents. In most<br />

cases a microphase cleaning agent can be used as a drop-in replacement in existing equipment.<br />

Microphase cleaners are effective in all types <strong>of</strong> cleaning equipment capable <strong>of</strong> applying<br />

the cleaning agent in a liquid form. This includes spray and ultrasonic equipment.<br />

Table 14.8.1. Comparison <strong>of</strong> different cleaner types<br />

Cleaning Agent Pros Cons<br />

Modern solvents<br />

Aqueous alkaline<br />

cleaner<br />

Aqueous based<br />

cleaners <strong>of</strong> MPC<br />

Technology<br />

Removal <strong>of</strong> adhesives and solder<br />

paste<br />

Wide process window<br />

Cleaning at room temperature<br />

Do not oxidize/corrode stencil<br />

Cheap<br />

Non-flammable<br />

Non ozone depleting<br />

No VOCs<br />

Mild odor<br />

Removal <strong>of</strong> adhesives and solder<br />

paste<br />

Wide process window<br />

Non-flammable<br />

Rapid drying<br />

Residue-free drying<br />

Long bath life<br />

Flammable<br />

Emits solvent vapors into work area<br />

Slow drying<br />

VOC (volatile organic compound)<br />

Ozone depletion potential<br />

Require explosion pro<strong>of</strong> equipment<br />

Do not remove adhesives<br />

Short bath life times<br />

Narrow process window<br />

Water rinse necessary<br />

Agitation <strong>of</strong> the cleaner (spray, ultrasonic,<br />

spray under immersion, overflow)<br />

necessary<br />

Table 14.8.2 presents the typical technical characteristics <strong>of</strong> different cleaning agents<br />

developed by Dr. O.K. Wack Chemie for stencil and misprint cleaning applications.<br />

14.8.3.4 Comparison <strong>of</strong> manual cleaning vs. automated cleaning<br />

Printing screens are <strong>of</strong>ten cleaned manually (Figure 14.8.8) as users still shy away from the<br />

purchase <strong>of</strong> a cleaning machine because <strong>of</strong> the associated investment costs ($6,500 to<br />

$60,000). However, a more accurate assessment must take the following points into ac-<br />

Table 14.8.2. Technical data <strong>of</strong> typical<br />

cleaning agents (water-based and solvent)<br />

Cleaning Agent Vigon � SC200 Zestron � SD300<br />

Chemistry water based solvent based<br />

Flash point none 106°F<br />

Appl. Temp. 77°F 77°F<br />

Process<br />

spray in air ultrasonic<br />

manual<br />

spray in air (ex<br />

pro<strong>of</strong>ed) manual<br />

count:<br />

(1) The mechanical rubbing action <strong>of</strong><br />

the repeated manual cleaning impairs the<br />

stencil surface. This is particularly apparent<br />

with plastic stencils. These changes to the<br />

stencil surface can result in misprints and<br />

shorten the service life <strong>of</strong> the stencil, making<br />

it very difficult to track the source <strong>of</strong> the<br />

problem.<br />

(2) Precise repeatability <strong>of</strong> the cleaning<br />

results is not guaranteed with manual

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