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Processing Dow Corning® Brand Silicone Encapsulants — Atmospheric Dispense
The atmospheric dispense has been demonstrated by machines from both Asymtek
and Camalot with a 20-gauge needle. The dispense is controlled by dispense
height and needle speed. Atmospheric dispense is done using a pattern that
dispenses on three sides of the die and after the material has been given time
to flow and "wick" underneath the die by capillary action, the fourth side is
put down to seal the die.
This method results in a void being trapped underneath the die. The void is
small enough that following up with an autoclave collapses the void and leaves
a void-free part.
Another option for atmospheric encapsulation is to dispense around all four
sides of the die and follow with a vacuum degassing step to remove the void.
This will work in theory, but the process of removing the void causes the
material to splatter and contaminate the backside of the die.
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