The ABC of Electronic Manufacturing Services

This post was originally published in 2014 and has since been revised for maximum accuracy.

Electronics manufacturing services are inherently highly complex processes. And they can bring with them a veritable sea of acronyms to get your head around.

In this blog post we've pulled together a list of some of the most common terms and acronyms that you're likely to encounter when you meet with a prospective Electronics Manufacturing Services (EMS) provider.

AOI - Automated Optical Inspection

A fast and repeatable inspection tool that reduces rework by checking component presence, text, orientation, and solder joints.

ATE – Automatic Test Equipment

A machine designed to carry out a variety of tests on different components which can be cost efficient when dealing with stable, high volume products.

AVL – Approved Vendors List

A list of parts and/or vendors that meet an OEM's standards in terms of pricing/quality etc. AVL details may be included within the bill of materials or as a standalone document.

BGA – Ball Grid Array

A surface mount package used for integrated circuits. Instead of pins or ‘legs’, a BGA consists of pads on the bottom of the device which have tiny balls of solder attached. When these are heated through a reflow oven, they melt to form the connection on the printed circuit board.

BOM – Bill of Materials

A list of all of the devices needed to make a single product. If the assembly of the product needs to be built up in stages, then the BOM may consist of multiple ‘levels’.

BTP – Build to Print

The provision of exact technical specifications/instructions for manufacture, provided by to a sub-contractor by an OEM.

CAD – Computer Aided Design

Computer software used to create 2D/3D design documents which help OEMs explore and visualise new product concepts.

CEM – Contract Electronic Manufacturing

A provider of design, manufacture, test and distribution services for electronic components and assemblies to Original Equipment Manufacturers.

CRD – Customer Request Date

The date on a purchase order the customer requests delivery for a product or service.

DFM – Design for Manufacture

The element of the design effort that focuses on assembling the product in the most cost effective manner, within the shortest time frame, and to the highest quality.

Designing a new product? You might want to read this

DFP - Design for Production

A means of measuring product design variables against manufacturing system performance to help product development teams avoid problems and improve profitability.

DFT – Design for Test

The element of design that focuses on ensuring the right test features are incorporated into hardware product designs. 

DIL – Dual In-Line

An electronic device package consisting of two parallel rows of pins or ‘legs’.

DIN (Deutsche Institut fur Normung)

A DIN rail is the global industry standard metal rail used for mounting circuit breakers and industrial control equipment inside equipment racks.

DMR – Defective Material Report

The report used to communicate details of any product that has failed to comply with a customer's agreed quality standards.  

EAU – Estimated Annual Usage

The amount of product that a customer expects to purchase from a supplier within a 12-month time-frame.

ECN – Engineering Change Note

The document used to communicate, authorise and justify any agreed changes to a prototype, product or part.

ECO – Engineering Change Order

The list of all amended items, assemblies and documentation including drawings, CAD files, standard operating procedures (SOPs) and work instructions.

ECR – Engineering Change Request

The start of the engineering change process in which a form is used to detail and proposed changes or improvements to a product or part.

EDI – Electronic Data Interchange

A means of digitally exchanging business documents, such as purchase orders, between two computers.

EMS – Electronic Manufacturing Services

The range of services provided by Contract Electronics Manufacturers to Original Equipment Manufacturers.

EOL – End of Life

The term given to any part or product that has been, or is intended to be, made obsolete.

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E-RFQ - Electronic Request for Quotation

An electronic means for a customer to request price and delivery information for a specific product or service.

ERP – Enterprise Resource Planning

A description of the broad set of activities that help businesses manage crucial tasks such as project planning, stock control and order tracking.

FAI – First Article Inspection

The process that helps validate that the parts produced comply with agreed engineering design specifications.

FFF – Fit Form Function

The understanding that if the specifications for fit, form and function of one particular part are met, then they can be interchangeable with other parts with the same requirements.

FG – Finished Goods

The term given to an item that is ready to be sold.

FP – Flying Probe

A form of automated test use printed circuit board assembly to carry out a Manufacturing Defects Analysis (MDA.)

FMEA – Failure Mode Effect Analysis

One of the first systematic techniques used when reviewing failure analysis of components, assemblies, and subsystems.

HALT - Highly Accelerated Life Testing

A stress testing methodology for enhancing product reliability by exposing any problems that may have been caused by new manufacturing processes.

HASL – Hot Air Solder Levelling

The predominant surface finish applied during PCB manufacture, in which boards are immersed in molten tin/alloy (or sometimes silver or gold.)

HASS - Highly Accelerated Stress Screening

A production screening method that helps to identify manufacturing defects to improve process control and overall quality.

HMI - Human Machine Interface

An industrial automation user interface or dashboard that is used to connect an operator to a controller.

ICT – In Circuit Test

A form of test which provides accurate and high-speed component level testing, with the option of both passive measurements and a degree of ‘power up’ testing.

JIT – Just In Time

The strategy of producing just the right amount of any specific product at the time that it is needed.

JTAG - Joint Test Action Group

An industry standard interface that is used for testing and verifying PCBs after assembly.

List X

A list of contractors or companies operating in the UK that are working on government contracts involving classified information.

LOI – Letter of Intent

The agreement between two or more parties before an official contract has been finalised.

LT – Lead Time

How long it takes for an item to be delivered to the customer once the order has been received by the supplier.

LTB – Last Time Buy

The last date on which purchase orders will be accepted by a factory for any part that has been made obsolete.

LTS – Last Time Ship

Following an LTB notification, LTS refers to the last date on which a factory will ship product out, whether directly to the customer or via their distribution channels.

LVHC - Low Volume High Complexity

The manufacture of smaller quantities of more complex products that will typically have a larger number of variants and a wider range of production tasks.

MDA - Manufacturing Defects Analysis

An in-circuit testing tool that is used to detect defects within a printed circuit board by measuring continuity.

MOQ – Minimum Order Quantity

The smallest quantity of parts that a supplier is willing to accept a purchase order for.

MOV – Minimum Order Value

The smallest value that a supplier will accept a purchase order for.

MPQ – Minimum Pack Quantity

The smallest number of parts that a customer can order from a supplier.

MRP – Material Requirements Planning

A software- based system for production planning and stock control.

MSD – Moisture Sensitive Device

An electronic device which is susceptible to moisture and so will require special handling and storage.

MSL – Moisture Sensitive Level

A means of differentiating electronic devices based on their sensitivity of the part. Different levels (from 1 through to 6) dictate specific handling and storage requirements.

MTO – Made to Order

A product or part that has been made to fulfil a customer’s firm order demand.

NCNR – Non-Cancellable Non-Returnable

Denoting that a purchase order for a part that cannot be cancelled or returned to the supplier as a result of a lack of, or fluctuation in, demand.

NCR – Non-Conformance Report

The formal document used to highlight details of non-conformance as the result of a process review or quality audit.

NPI – New Product Introduction

The process carried out by a contract electronic manufacturer on a product that they've not built previously. NPI is often based on a small build quantity to mitigate any unforeseen design or manufacturing issues prior to volume build.

What should a new product introduction (NPI) report look like?

NRE - Non-Recurring Engineering

The one-off costs associated with upfront engineering work (build pack creation, machine programming, tooling etc.) that is carried out prior to production.

OEM – Original Equipment Manufacturer

The term for a company that designs and sells its own products.

OTD – On Time Delivery

A measurement used to determine if delivery to a customer was made according to the purchase order request date.

OTIF – On Time in Full

The measure used to determine that the correct quantity and quality of a product has been delivered to the customer on the agreed order delivery date.

PCB – Printed Circuit Board

A device that mechanically supports, and electrically connects, electronic components using a combination of conductive tracks, pads and other features etched from copper sheets and laminated onto a non-conductive substrate.

PCBA – Printed Circuit Board Assembly

The assembly of electronic devices onto the PCB that result in a finished product.

PCN – Product Change Notification

The official notification, usually from a component manufacturer, that a part they are supplying will be changing in terms of fit, form or function.

PO – Purchase Order

A document supplied by a customer to a supplier that confirms the details of the product or service they have ordered.

PPM – Parts Per Million

A value that represents the part of a whole number in units of 1/1000000.

PTH – Plated Through Hole

A packaging type, and method, of mounting electronic components onto a PCB by placing the pins or ‘legs’ through drilled holes. The components are then either soldered by hand or by using flow solder equipment.

QC – Quality Control

The process responsible for ensuring the quality of a product is reviewed prior to shipment.

QMS – Quality Management System

The set of policies, processes and procedures that focus on achieving quality objectives for an organisation's product or service.


The European Union regulation concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals.

RFI – Request for Information

An RFI is typically carried out before an RFQ. It can be used by customers as part of the initial supplier section process in order to obtain company and capability information from potential supply chain partners.

RFQ – Request for Quotation

The process by which a customer submits an order to obtain price and delivery information for a product or service.

RMA – Return Material Authorisation

An agreement from a supplier, in the form of a reference number or document, confirming they will take back goods from a customer.

RoHS – Restriction of Hazardous Substances

An EU directive restricting the use of hazardous substances (such as lead) that are commonly found within electrical and electronic components.

SCM – Supply Chain Management

The process of managing the movement of goods within an organisation, from the receipt and storage of raw materials through to the shipment of finished goods.

SLA – Service Level Agreement

An agreement drawn up between the customer and the supplier that contains details of specific service expectations such as pricing, estimated annual usage, delivery, quality and warranty.

SMD – Surface Mounted Device

An electronic device which is designed to be suitable for surface mount placement.

SMT – Surface Mount Technology

The method of mounting electronic components, which unlike PTH, involves the device being placed onto pads on the PCB instead of the pins or ‘legs’ being placed through drilled holes.

SPC – Statistics Process Control

A method used to monitor, control and improve a process through detailed statistical analysis.

SPI - Solder Paste Inspection

A piece of equipment used to monitor and control solder paste deposition.

TCM – Total Component Management

A process which helps OEMs realise tangible benefits (such as on-time, in-full and assembly-ready delivery of product) and which aims to reduce total acquisition costs.

TQM – Total Quality Management

A management system in which all members of an organisation are committed to continually improving the processes, procedures, products and service that they offer.

UOM – Unit of Measure

The standard unit by which the quantity of an item is expressed (cm, mm, each etc.)

VA – Value Add

A term that denotes that additional features or benefits have been provided within a product or service but without additional cost to the customer.

VMI – Vendor Managed Inventory

The process in which a supplier is responsible for managing and maintaining agreed inventory levels (which might usually be held on site at a customer’s premises) so they are available for immediate use.

WEEE – Waste Electrical and Electronic Equipment

The EC directive that outlines how electronic and electrical goods must be collected and recycled.

WIP – Work in Progress

A partially complete works order which is awaiting additional parts or processes before it can be completed.

WO – Works Order

The document that confirms to the manufacturing plant the quantity, revision, build instructions and specifications required prior to completion/shipment to the customer.


A placement programme that instructs a machine as to which component goes where on a board.

So there you have it - an A - Z (well an A to XY) of some of the most frequently used terms used within the electronics manufacturing industry. If you'd like to read similar content on what's new in the world of contract electronics manufacturing then you can subscribe to our blog to receive the latest updates. 

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Written by Neil Sharp

Neil has over 25 years’ experience in Electronics Manufacturing Services and Component Distribution. During his career, Neil has held a range of leadership positions in sales, marketing, and customer service. Neil is currently part of the ESCATEC Senior Management Team and is responsible for setting and delivering the overall Group Marketing strategy. Neil heads up the marketing department and is responsible for both the strategy and the implementation of innovative marketing campaigns designed to deliver high quality content to those seeking outsourcing solutions.