Showing posts with label Definition. Show all posts
Showing posts with label Definition. Show all posts


EMC: Electromagnetic Compatibility, the ability of a product to coexist in its intended electromagnetic environment without causing or suffering functional degradation or damage.

EMI: Electromagnetic Interference, a process by which disruptive electromagnetic energy is transmitted from one electronic device to another via radiated or conducted paths (or both).

FR4_Flame Retardant 4

A standard epoxy-glass PCB material.


~ It meets the requirements of Underwriters Laboratories UL94-V0, which exhibits flammability characteristics that are self-extinguishing.

~The cheaper alternatives have higher dielectric losses at high frequencies.

~ It absorb more moisture

~ Provide less strength and stiffness.

~ Assuming a rise/fall time >1 ns, trace lengths up to 10 inches can be supported for data rate of 150 Mbps.

Voltage Isolation Requirements

Table B: Basic and Reinforced Isolation Requirements
Common differences between basic and reinforced isolation requirements for various standards.
See specific standard for your system as requirements may vary slightly.

Safety Extra-Low-Voltage—A voltage less than 30 VRMS (60 VDC)

Hazardous—A voltage greater than 30 VRMS (60 VDC)

Basic Insulation—A single-level of protection against electric shock.
See Table B.

Reinforced/Double Insulation—Two-levels of protection against electric shock.
See Table B.

Creepage vs Clearance

Creepage is the separation between two PC board solder eyes as measured along the surface of the board.
Clearance denotes the shortest distance between two conductive parts as measured through the air.

Artwork by Melinda Vaughan, National Instruments.

Types of Via in PCB

Through hole via has a path to both external layers.
 Buried via grant's connection within inner layers, it has no path to the external layers.
Blind via does not cross through the entire board, and has a path to only one external layer.

HASL - Hot Air Solder Level

It is a molten solder immersion and hot air leveling or blasting of surfaces and holes to provide a "retained" coating on exposed copper surfaces.

The advantage of HASL is excellent solderability, because as its name implies "Nothing solders better than solder."  One of the less-expensive surfaces finished with a good shelf life.

However, the problem with this finish is its limitation and difficulty. A limited capability on high density boards and a capacity to clear vias holes on a greater than 6:1 aspect ratio. A difficulty to maintain hole size tolerance along plated edges and to process thin material.