The PCB assembly process is usually a complement of equipment with different capabilities and constraints in terms of automation, speed, component technology, and quality. Table 6.4 contains a listing from the classifications for the different types of PCB assemblies. This listing was developed by the Institute for Interconnecting and Packaging of Electronic Circuits (IPC).
It can readily be seen that the task of assembling a PCB can be achieved through many different alternatives of equipment and processes, some of which are overlapping in function, yet different in quality and productivity.
A typical approach to printed circuit board assembly is presented in Figure 6.7. The process presented shows a two-sided mixed printed circuit board (PCB) assembly, including all the steps required to populate the boards with components on both sides. Using a technology mix of TH and SMT, components can be loaded by machine or by hand, depending on the geometry of the components and the volume and number of component types that the manufacturing facility processes. Automatic sequencing and insertion equipment are limited by the number of heads available and geometry of the parts.
SMT components can also have different material and manufacturing options. Components can be placed by hand or machine, depending on the constraints of geometry and package variety. In addition, some of the smaller-size components might be assembled by more accurate placement machines, such as robots, requiring their own set of processes in parallel to the regular-size SMT components.
Three levels of PCB costs systems are in common use in the electronics industry, depending on accuracy and resources available to manage the cost system.