Electronic Manufacturing Services (EMS)

Electronic manufacturing services (EMS) are companies that design, assemble, produce, and test electronic components and assemblies for original equipment manufacturers (OEMs). Typically, OEMs retain ownership of product designs and brand names. Some electronic manufacturing services are contract electronic manufacturers (CEMs) that specialize in rapid prototyping or product testing. Others offer small, medium, or large production runs. Electronic assemblies can be built from vendor-owned, customer-supplied, or consignment materials. Design services provide conceptual product development advice and mechanical, electrical, and software design assistance. Testing services perform in-circuit, functional, environmental, agency compliance, and analytical laboratory testing. Electronic manufacturing services are located across the United States and throughout the word. They vary in terms of production capabilities and comply with various quality standards and regulatory requirements.  

Electronic manufacturing services (EMS) use several manufacturing processes and technologies. For example, many organizations provide basic printed circuit board (PCB) assembly services or connect populated boards into larger assemblies. Some vendors are capable of working with flexible PCBs. Others handle only rigid boards. Rigid-flexible PCB assemblies are rigid boards with flexible interconnects. Flip chips are integrated circuits (ICs) that use a specific number of bumps to provide electrical and mechanical interconnections. Vendors who specialize in optoelectronics can assemble devices that function as electrical-to-optical or optical-to-electric transducers. Examples of optoelectronic devices include light emitting diodes (LEDs), injection laser diodes, and photodiodes. In terms of component mounting, electronic manufacturing services use two basic technologies. Through hole technology (THT) mounts components on a PCB by inserting component leads through holes in the board and then soldering the leads in place on the opposite side of the board. Surface mount technology (SMT) adds components to a PCB by soldering component leads or terminals to the top surface of the board.

Electronic manufacturing services comply with both voluntary standards and regulatory requirements. The International Standards Organization (ISO), a worldwide federation of national standards bodies, establishes voluntary guidelines for design, development, production, and installation. The American National Standards Institute (ANSI) represents the United States in ISO. Industry-specific standards include QS-9000 and AS9100. QS-9000 is a quality standard for suppliers of DaimlerChrylser Corporation, Ford Motor Company, and General Motors Corporation. It is based on the 1994 edition of ISO 9001, but contains requirements that are particular to the automotive industry. AS9100, a standard from the International Aerospace Quality Group (IAQG), contains over 70 requirements specifically for aerospace and aviation companies. Regulatory agencies such as the U.S. Food and Drug Administration (FDA) also provide certifications. Federal standard 209E (FED-STD-209E) establishes air quality standards for clean rooms. Often, EMS companies that perform work for the U.S. government or its suppliers comply with military specifications (MIL-SPEC).

• The Circuit Designer's Companion, Second Edition
  The Circuit Designer's Companion, Second Edition Providing a unique masterclass in practical electronic design, this book focuses on the art of designing circuits so that every production model...
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