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Oltin fond 2021, 1-sonBog'liq OLTIN FOND JURNALI 1-SON oxirgi Farhod Sultonov, Farruh Bozorboyev. O\'zbekiston hukmdorlari, 1. Tadbirkorlik turlari va shakllari, yarimo-tkazgichli-lazerlarOLTIN FOND
2021, 1-son
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120 mils long by 30 mils high. In addition, current stencil printing techniques are
generally ill-suited to handle preexisting components that may be as much as 50 mils
high.
There is a further requirement where it is desirable to print glue on a PCB that
already has clinched connector leads protruding through the PCB. In this case, the
required vertical clearance for preexisting board components alongside the adhesive
deposition sites poses the manufacturing dilemma of producing controllable-volume,
micro-fine apertures in a substrate thick enough to clear the preexisting components.
It is also necessary in the SMT industry to deliver solder balls in a ball grid
array (BGA) to a substrate, such as a BGA package or a silicon wafer with active
circuits. The substrate has pads that need to have flux placed on their surface. BGA
balls are placed into the flux on the pads through the use of a stencil. The tacky flux
holds the balls onto the substrate. During the solder reflow process, the solder balls
melt and become permanently attached to the substrate. It is desirable to bring the
ball drop stencil in contact with the substrate and drop the balls into the flux deposits
over the pads on the substrate. However, it is also desirable to keep the flux away
from the bottom side of the stencil. Current techniques include a structure with a
chemical etch relief on the bottom side of the stencil and a small hole etched all the
way through the stencil. This is a very difficult process to control. There is therefore a
need in the SMT industry to provide a cost-effective, flexible and easily-controllable
means for applying viscous materials, such as adhesives, conductive glue, solder
paste, and solder balls, onto PCBs, flexible circuits, wafers and other substrates.
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