Companies that design, assemble, manufacture, and test electronic components and assemblies for original equipment manufacturers are known as electronics manufacturing services.

The original equipment manufacturers, commonly termed as OEMs, retain the ownership of the said product designs and brand names. Electronic Manufacturing services sometimes branch out into contract electronic manufacturers, and specialize in rapid prototyping and product testing.

Electronic manufacturing services offer large, small or medium production runs. The materials can be built from consignment, vendor-owned or customer supplied materials.

Some electronic manufacturing services offer design services like conceptual product development advice, software, and mechanical and electrical design assistance.

Various other electronic manufacturing services have testing abilities and can perform in-circuit, environmental, functional, analytical laboratory and agency compliance testing.

They use several processes and manufacturing technologies. Some of them provide printed circuit boards, connected populated boards or assembly services into larger assemblies. Other products that can be made are flexible printed circuit boards, rigid boards and rigid-flexible circuit boards.

Some vendors specialize in optoelectronics. They can assemble devices that will function as electrical to optical or optical to electrical transducers. Light emitting diodes, injection laser diodes, and photodiodes can also be assembled.

Electronic manufacturing services also include component mounting. The electronic manufacturing services use two basic technologies, through hole technology (THT) and surface mount technology (SMT).

In the THT, components are mounted on a PCB by inserting component leads through holes in the board. They are then soldering the leads in place on the opposite side of the board.

In the SMT, components are added to a PCB by soldering component leads or terminals to the top surface of the board.

Electronic manufacturing services are available all over the world and in the United States. The EMS varies in terms of production capabilities, quality standards and various regulatory requirements.