Author: Patrick Song

The Different PCB Assembly Methods

The Printed Circuit Board (PCB) is the “brain” of an electronic device. Every electronic device has it. It could be single-layered or multilayered. Complex devices such as computers can have as many as 12 layers of printed circuit board to make them function according to their purpose.

However, before a PCB can function, it needs to undergo PCB manufacturing and PCB assembly (PCBA). PCB Manufacturing is the process of creating the printed circuit board, while PCBA is the process of attaching electronic components to make the PCB work according to its functionality. A PCB has two sides: the component side and the copper tracks side. As the name implies, the component side is where you can find the electronic components such transistors, resistors, and capacitors. On the other hand, the copper tracks side is where the electrical connections are.

There are two known methods used in PCB assembly: surface mount and through-hole. Both methods use electro-mechanical and manual assembly along the way.

Surface-mount Assembly (SMT)

SMT is the process of mounting electronic components on the surface of a printed circuit board without drilling holes on it. As of today, majority of PCB manufacturers and assemblers use this technology due to its cost efficiency in the manufacturing and assembly process. The 80s was the beginning of sophisticated electronic devices that require much smaller PCBs. Thus, SMT was developed and gained its popularity during that time. Nowadays, you could see multilayered electronic PCB in a single device. This is made possible with the use of SMT.

Solder pads and solder paste are used to mount components onto the PCB. SMT decreases the number of holes drilled on the surface of PCB, if not completely eliminates the need for drilling holes. The use of the technology allows for a much higher component density to be achieved. The electronic components in an SMT procedure are as small as 1mm. These components are getting smaller as new developments emerge.

Pcb assemblyMoreover, SMT creates a dual-mounting technology during PCB assembly, which means both side of the PCB can be used to mount components. Because of the surface mounting technique, there is no need to provide space for wiring purposes. Another advantage of SMT is that it can still use the conventional method when necessary.

One disadvantage of SMT is its unreliability on electronic devices that require frequent attaching or detaching. Due to its smaller components, reliability of the circuit may be compromised and solder joints are less efficient compared to those of a through-hole assembled PCB. Changing the settings of prototype and test applications is harder. It will take days or even weeks to create the correct setting for another prototype.

Through-hole Assembly

Through-hole technique, sometimes spelled “thru-hole”, is the method of mounting components with holes pre-drilled on the wiring board. The electronic components have pins and are soldered through the holes. The mechanical bond of the electronic components with the PCB is stronger. Since it allows components to be easily interchanged, this technology is commonly used in prototyping and manufacturing heavy-duty electronic equipment such as military and aerospace products.

One disadvantage of through-hole assembly is that it requires a more expensive board due to drilling requirement. Through-hole also limits an assembler to work one side of the board.

In conclusion, SMT is more reliable and practical for the mass production of electronic products and devices that need highly sophisticated components and wiring, while through-hole PCB assembly is best for creating prototypes and heavy-duty equipment. Despite the popularity of SMT among manufacturers and assemblers, many still use through-hole assembly due to its reliability in withstanding constant mechanical and environmental stress.