A Short Guide to PCB Assembly

Electronic parts are inside every device bought today, and they’re what makes the device do what it does. If a company builds its own hardware, odds are high that they will need to design and build their own electronics. An electrical engineer knows how the pcb assembly process works, but this guide is meant for the uninitiated. Read on to learn the basics of PCB manufacturing.

The Production Process

A PCB is also referred to as a printed circuit board. It’s a flat fiberglass piece containing traces that connect electrical components, as well as pads that allow the components to connect to the board itself. PCBs consist of fiberglass, epoxy, conductive copper and a mask to keep solder in its intended position. They’re made using automated processes, usually by outside companies.

Application of Solder Paste

The first step in PCB assembly is to apply solder paste to the fiberglass board. The paste consists of tiny metal balls and flux; it must be applied precisely. In manufacturing environments, this is accomplished with a stencil, a fixture and a paste applicator. When stencils are removed, solder is in the right positions.

Pick & Place

After solder paste application, the boards go to pick & place machines. These robotic instruments position parts correctly, and ready them for soldering. Components are soldered to the board’s surface, and these machines can run day and night. Compare that to the high potential for error when humans place these components, and it’s easy to see why robotics are taking over the industry.


Once components are placed, the PCBs go to a reflow oven. The oven heats the boards until solder melts and joins the parts securely. Parts move on a conveyor belt past heaters that gradually warm the boards to the correct temperature, and they cool at controlled rates.

Quality Assurance and Inspection

After reflow, PCBs enter the testing phase. Mistakes during manufacturing result in non-functional components, short circuits and other errors. Visual inspections, optical inspections and x-rays can point out such errors; if flaws are detected the board will be reworked or scrapped. The sooner errors are found, the sooner they may be fixed—at substantial savings for the company.