16-04-2012, 04:12 PM
pc board network and repair
guide1.pdf PCB.pdf (Size: 6.36 MB / Downloads: 433)
Introduction
PC boards are more complex today than ever before, but despite how severely damaged they
may be, they can be repaired. Indeed the high value of many PC boards demands that they
be repaired. Even less expensive assemblies require repair because just-in-time
manufacturing and tightly controlled production runs leave little room for shortage.
Just a few years ago, PC boards were much simpler and repairs were relatively easy. Today's
PC boards have fine pitch components, ball grid arrays and fine line circuits making them a
challenge to repair. Yet, we're driven by simple economics and must repair damaged PC
boards whenever possible. This manual is designed to help you repair and ship good, reliable
PC boards that might otherwise be consigned to scrap.
Printed Board Types
Four Printed Board Types are referred to in this guidebook.
R - Rigid Printed Boards and Assemblies
A printed board or assembly using rigid base materials only. These may be single sided,
double sided or multilayered.
F - Flexible Printed Boards and Assemblies
A printed board or assembly using flexible or a combination of rigid and flexible materials
only. May be partially provided with electrically nonfunctional stiffeners and/or cover lay.
These may be single sided, double sided or multilayered.
W - Discrete Wiring Boards and Assemblies
A printed board assembly using a wire technique to obtain electrical interconnections.
C - Ceramic Boards and Assemblies
A printed board or assembly using ceramic as the base material with interconnections
separated by dielectric.
Tools and Materials
Repair is and may always be a highly labor intensive operation relying more on individual
operator skills than automation. Despite the availability of very good tools for repair, many
in-house repair operations are poorly equipped. Here are a few guidelines for the basic
equipment needed in an up-to-date repair operation.
How To Set Up An In-House PC Board Repair Department
It's a fact that far more printed circuit assemblies are damaged during the manufacturing
process than they are in the field. And even though PC boards are more complex today than
ever before, they are still repairable. Ten years ago boards were much simpler, and repairs
were easy; but the assemblies also cost a great deal less. Today's printed circuit
manufacturers and assemblers are driven by simple economics. They must repair damaged
circuit boards. The primary question is whether to develop and maintain a full repair
department in-house, or to contract the repair out. Which choice makes the most sense?
Electrostatic Discharge (ESD)
Certain components used in electronic assemblies are sensitive to static
electricity and can be damaged by its discharge. Static charges are
created when non-conductive materials are separated, such as when
plastic bags are picked up or opened, when friction occurs between
articles of synthetic clothing, when plastic tapes are dispensed and many
other causes.