Wet characteristics improvement to underfill - Printed Wiring Boards
High density and performance supported by the surface quality improvement technology
Sealing replenishment performance is enhanced by underfills (i.e., liquid hardening resin to protect gold wire of IC chips)
1) Due to poor replenishment and fluidity performance of underfills, wet does not spread over well. Or bleeding out occurs.
2) There is a time dependence on the surface improvement effectiveness
= Difficulty of controlling wettability
Wet-blast was applied after SR develop and drying process.
- 1) Cleaning and removal of foreign objects on the SR surface.
- 2) Improve wettability by expanding the surface area.
- 3) Bleed prevention by Pinning.
Example of surface quality improvement applied by wet-blasting
Resin solution was dropped on the SR surface, side view observation.
|Untreated||Wet Blast (A#800)||Wet Blast (A#2000)|
|One Minute After Dropping the Resin Solution|
|SEM Photograph of the Treated Surface (Angle 10 °)|
|Surface Roughness RMS||0.047μm||0.237μm||0.113μm|
↑ Non-directional micro roughness is obtained by wet-blasting.
Differentiation from plasma treatment
1) Polar group independent surface quality improvement
- As this is the wettability improvement carried by expanding the surface area, its effect does not have time independence.
- As it does not increase the polarity, the surface does not induce unwanted water.
2) Droplet Pinning Hold
In the case droplet is shrunk
In the case droplet is diffused.
Droplet spreads out due to expansion of the surface area, but micro-roughness at periphery holds it as the function of a dam.
Contact Angle 78.3° (Pure water)
When the surface is flat, the surface tension is working and the droplet shrinks.
Contact Angle 79.1° (Pure water)
The fine uneven surface prevents the droplet movement (shrinks)
Examples of associated equipment
(PFE - Physical Fine Etcher)
Surface treatment equipment for precision physics cleaning to sheet material surfaces like printed-wiring substrates (thickness range: 0.2-2.0mm, width spec: less than 610mm)
It processes both sides of the lamina materials evenly, and is able to continually process automatically the steps from water rinsing to cutwater followed by drying.
- Wide gun with 630mm in width is used and hence it can process thinner plate with up to 610mm in width.
- Processing both sides of the work piece is applicable.
- Continuous automatic processing of blasting, rinse, cutwater and drying is applicable.
- Processing without damaging the circuit on the surface of substrate is applicable.
- "Line and space 30um" is applicable.
- Cleaning for any material types of substrate is applicable.
|Work piece||Thinner plate materials, Printed Wiring Boards|
|Work size||Width : 610mm and below|
Length : 200～700mm
Thickness : 0.2～2.0mm
|Conveyor transportation speed||0.5～2.5m/min|
|Gun||Wide Gun 630mm ×2|
|Power supply||AC200V, 50/60Hz, 3 phases|
|Power consumption||About 15kW (Total rated apparent power of all the equipment)|
|Air supply pressure||0.5MPa or more, 0.7MPa and below|
|Air consumption||19.9m3/min (NTP at 0.25 MPa of preset blast air pressure)|
|Option||Sludge Recovery unit|