EMS may provide a variety of manufacturing services, including design, assembly, and testing. EMS servces may be contracted at various points in the manufacturing process. Some companies require only a design file from the customer before proceeding to develop the product, source the components from a trusted distributor, and assemble and test the product. Alternatively, EMS providers who specialize in assembly may require the customer to provide the design, the components necessary for manufacturing, and an assembled sample. EMS companies may provide additional onsite services, such as PCB etching, or provide these services through another contractor.

Electronic manufacturing involves different levels of automation, depending on the company and project. Companies that produce large runs of products typically use heavily automated manufacturing. Providers who specialize in prototypes or small production runs typically assemble PCBs manually to save the time and cost involved in setting up automated assembly equipment.