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An Introduction to Surface Mount Assembly

12th February 2014

What Is Surface Mount Technology (SMT)

SMT is a relatively new type of PCB assembly which in the last few years has grown to be the dominant form of printed circuit board production.

SMT differs from PTH assembly in that the electrical components are soldered directly on to the surface of the board. With PTH boards the components are inserted into holes on the circuit board and then soldered on the reverse side to secure them in place. SMT developed from the need to produce lighter and smaller PCBs and it is used in PCB prototyping, chip carrier packages and flatpack packages.

What Are the Pros of SMT Assembly?

As PCBs became more complicated, traditional PTH assembly resulted in boards that were too large and heavy for many applications. Surface Mount Assembly can produce the same board but in a much smaller and lighter form.

As well as being much smaller than their PTH equivalents, SMT components can also be fitted on to both sides of a PCB. This saves even more space and reduces the weight of a board.

SMT can produce boards for use in applications that simply couldn't exist if PTH was the only method available.

Because SMT boards are more efficient to assemble, they are much better suited to being made en masse than PTH boards, which reduces the average assembly cost.

The smaller physical size of an SMT board results in a faster circuit speed when compared to the equivalent PTH board, which again makes them suitable for a greater range of applications.

Despite being inferior to SMT boards in many ways, PTH assembly still has its uses, particularly in older applications where moving to an SMT solution may be uneconomical or impractical. PTH and SMT boards are fully compatible with each other and hybrids of the two technologies are quite common.

Surface mount assembly is more suited to outsourcing than Pin-Through-Hole solutions due to the high initial outlay required to purchase the equipment needed to produce your own.

Surface mount assembly also requires more technological, production and design skills that PTH boards so outsourcing to a specialist is the most common pathway to production. Working with specialists is often valuable in its own right as they can aid in designing and refining the final board.

If you are considering switching to surface mount assembly or have a new application which requires an SMT solution, then please contact us for advice or information.