Wednesday, June 6, 2012

pcb clone business

PCBs intended for extreme environments often have a conformal coating, which is applied by

dipping or spraying after the components have been soldered. The coat prevents corrosion and

leakage currents or shorting due to condensation.The earliest conformal coats were

wax;modern conformal coats are usually dips of dilute solutions of silicone

rubber,polyurethane,acrylic,or epoxy. Another technique for applying a conformal coating is

for plastic to be sputtered onto the PCB in a vacuum chamber. The chief disadvantage of

conformal coating is that servicing of the board is rendered extrmely difficult.
Many assembled PCBs are static sensitive,and therefore must be placed in antistatic bags

during transport.When handling these boards,the user must be grounded (earthed).Improper

handling techniques might transmit an accumlated static charge through the board ,damaging

or destroying components.Even bare boards are sometimes static sensitive.Traces have become

so fine that it's quite possible to blow an etch off the board(or change its

characteristics) with a static charge.This is especially true on non-traditional PCBs such

as MCMs and microwave PCBs.