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4 Process Hardware 4.4 Print Material 22 Process Foundation DEK Micron-Series 12/2017 Using Print Material (Squeegee) 4.4.1 Re-using Print Material ● Only re-use print material if there have been no printing problems ● D…
4 Process Hardware
4.4 Print Material
Process Foundation DEK Micron-Series 12/2017 21
Environment
●
Most print materials decrease in viscosity (become more liquid) when they get hotter (though
solder paste may dry out and eventually become thicker)
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Most increase in viscosity (get thicker) when they get colder
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Minimise temperature fluctuations (keep covers closed, use an environment control module
(ECM), locate machine away from sources of heat, direct sunlight, etc.)
●
Some materials are also sensitive to changes in humidity. Water-soluble pastes, for instance,
tend to absorb water if humidity is high, decreasing their viscosity and degrading their later
performance in the reflow oven
Temperature:
●
Affects paste viscosity
●
Keep comfortably cool (22 - 24°C typical)
Humidity:
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Too low may dry out paste
●
Too high may cause water absorption, particularly in aqueous pastes
●
Keep to mid-range (40-50% typical)…
In this example a change of room temperature from 20°C to 30°C reduced the materials viscosity
by some 10 – 15%, resulting in poorer print definition.
4 Process Hardware
4.4 Print Material
22 Process Foundation DEK Micron-Series 12/2017
Using Print Material (Squeegee)
4.4.1 Re-using Print Material
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Only re-use print material if there have been no printing problems
●
Discard old material or dry material around the edges or on the squeegees / wiper blades
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Store good material in a sealed container overnight
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Do not mix used and new material in the same container
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The exact procedure for re-using a material will depend on its type and quality as well as
economic considerations
Storage
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Store material in order of age and use FIFO (first in, first out) procedures
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Store as per manufacturers instructions
●
Refrigeration may be required for long periods
●
Storing at room temperature is OK for short periods and may cause fewer problems then
failing to normalise material taken from a refrigerator
●
Minimise temperature fluctuations during storage
●
Label material clearly showing the date and time taken out of storage
Example:
4 Process Hardware
4.4 Print Material
Process Foundation DEK Micron-Series 12/2017 23
Exercise
Complete the table below for the specific material that you use in production. Information can be
found from the material data sheets, production data sheets, from the Internet or by asking your
instructor or process engineer.
Material Type and Product Code:
Personal Safety Precautions:
Method of Maintaining Roll Volume:
(Manual or Auto-dispense)
Knead Strategy:
(Manual, Programmed or Both)
Working Temperature Range:
Storage Procedure:
Re-use Procedure:
Disposal Procedure:
Notes: