As technology gets smaller so does the requirement for more compact components, however, alongside this, technological capabilities have become more advanced creating the demand for more components on circuit boards.
There are two main methods for mounting components onto a PCB; Surface Mounting and Through-Hole assembly processes. Through-Hole technology was first developed in the 1940s and was the go-to form of assembly up until the 1980s. Surface Mount Technology was first developed in the 1960’s; however, it wasn’t until the 1980’s that its popularity within the manufacturing industry grew. It met the demand created by advanced electronics manufacturing that the through-hole process couldn’t fulfill. Initially, it was thought that the increase of Surface Mount Technology into the assembly process would make the Through-Hole process obsolete; however it has remained a resilient feature of printed circuit boards in a number of industries.
Key Features, Advantages and Disadvantages of each Mounting Process
Through-Hole Technology (THT)
With Through-Hole, each components lead wires are fed through pre-drilled holes in the circuit board and then the lead ends are permanently mounted to the board and soldered onto pads located on the bottom of the board making them well equipped for physical endurance.
- Stronger bonds mean it’s better equipped for mechanical stress. (used in industrial machines, military and aerospace).
- Useful for manual adjustments and replacing/testing.
- Copes with more environmental stress.
- Ideal for prototyping.
- High heat tolerance and power handling capabilities.
- Can be expensive due to the added cost of drilling holes & the hand soldering of components.
- Time consuming due to construction process.
- Requires soldering on both sides.
Surface Mount Technology (SMT)
Originally known as planar mounting, with SMT components, whether or not they have leads are designed to be soldered directly onto the surface of the circuit board pad. Today, nearly all electronic hardware is manufactured utilising SMT as it is faster, smaller and cheaper than THT.
- Ability to solder to both sides of board allows for increased component density.
- Lack of holes drilled provides more space.
- Ability to miniaturize components so can add more.
- Improved quality & performance of PCBs.
- Lower cost process.
- Faster processing, lower production time.
- Solder joint formation reliable.
- Solder joint formation repeatable.
- Ideal for high volumes due to automated production.
- Overall better equipped to meet the demand for more compact technology.
- Expensive machinery, better to utilise companies with the production capabilities in place such as PCB Train.
- Due to process costs, better for large-scale productions.
- Imprecision in the assembly line can result in repeated defects.
Despite its benefits, THT remains the secondary option to the more modern surface mount as the component density and volume reduction of SMT meets the smaller sized and high-performance capability demands of modern electronics.