Surface Mount Technology (SMT) in Electronics is a packaging technology that mounts electronic components on the surface of a Printed Circuit Board / Printed Wiring Board (PCB / PWB) instead of inserting them through holes of the board. SMT is relatively new technology in electronics and provides state-of-art, miniature electronics products at reduced weight, volume and cost.

SMT (Surface Mount Technology) is rooted in the technology of Flat Packs (FP) and hybrids of 1950s and 1960s. But for all practical purposes, today’s SMT can be considered to be a continually evolving technology. Currently the use of Fine Pitch, Ultra Fine Pitch (UFP) and Ball Grid Arrays (BGAs) are becoming even more common. Even the next level of packaging technologies such as Chip-on-Board (COB), Tape-Automated Bonding (TAB), and Flip Chip Technologies are gaining widespread acceptance. Multichip Modules (MCMs) using wire bond, TAB, or Flip Chip are used to achieve the highest performance possible but with a cost premium.

For electronics companies an entirely new internal and external infrastructure is necessary to develop and sustain the SMT Technology. It is prudent for almost every electronics company to begin developing its own internal infrastructure. Companies who do not focus on this will risk their own survival.

In order to understand SMT or Surface Mount Technology, one need to learn and understand some of the common terms, acronyms and meanings used in SMT.

Many electronic components are not yet available for surface mounting. Due to this reason, SMT must accommodate some through-hole components. Therefore the term “Surface Mount Assembly is incomplete”.

Surface mount components are small and can be mounted on either side of the PCB and have gained widespread usage in electronics. The benefits of SMT or Surface Mount Technology are available in both design and manufacturing.

In SMT or Surface Mount Assemblies (all Three Types of Surface Mount – Type I, II, and III) have three major process steps in common: mounting of electronic components, soldering, and cleaning.

Following equipments are required for any SMT production line:

• Pick-and-Place Machine for SMT

• Wave Soldering: Equipment & Process

• Reflow Soldering Equipment for SMT

• Solder Paste Screen Printer for SMT

• Curing / Baking Oven for SMT

• Solvent Cleaning in SMT

• Repair and Inspection Equipment for SMT

SMD or Surface Mount Electronic Components for SMT are no different from through-hole components as far as the electrical function is concerned. Because they are smaller, however, the SMCs (surface mount components) provide better electrical performance.

While surface mount technology has matured, it is constantly evolving as well with the introduction of new packages. The electronics industry is making progress every day in resolving the economic, technical, and standardization issues with surface mount components.

Read: SMD: Surface Mount Electronic Components for SMT

Solder paste or solder cream is simply a suspension of fine solder particles in a flux vehicle. In electronics industry, solder paste is used in Surface Mount Technology (SMT) to solder SMDs on to the Printed Circuit Board. The composition of the particles can be tailored to produce a paste of the desired melting range. Additional metals can be added to change paste compositions for specialized applications. Particle size and shape, metal content and flux type can be varied to produce pastes to varying viscosities.

Read: Solder Paste and itsapplication in SMT

A PCB is basically a substrate (normally made from glass epoxy) with conductive traces etched from copper sheets that facilitate flow of controlled electricity. Printed Circuit Board (PCB) for Surface Mounting (SMT) need to be choosen wisely taking into consideration factors such as CTE (Coefficient of Thermal Expansion), cost, dielectric properties and T_g. When designing surface mounting board (PCB), the selection of substrate is basically determined by the type of SMD components to be used.

For successful implementation of Surface Mount Technology (SMT) in the assembly line for manufacturing and production, the first order of business for management consideration is to obtain a clear outline of the outstanding technical issues. SMT should be developed and introduced is stages. Even after the technology has been evaluated and debugged, it should be implemented on a few selected products first.

Read: Implementing SMT in Assembly Line for Manufacturing and Production

There are many design issues with a surface mount design before the design is taken into consideration. The designer must consider market needs, function, and package moisture sensitivity. For every SMT board, the designer must consider all the pros and cons of designing the board in SMT. In the decision is to go ahead with SMT, then it is important to follow the specific guidelines and rules.

Read: Surface Mount Design Considerations

There are many soldering process available for surface mount components but none is perfect for all applications. All SMD soldering processes have technical concerns and there are ways to resolve those concerns. Because it offers higher yield and lower operation cost, convection dominant IR soldering has evolved as the preferred process for reflow soldering.

SMT (Surface Mount Technology), like other SMD Soldering and PCB assembly technology is not ZERO-Defect soldering process. There will always be some or the other defect in any Electronics PCB assembly in both Thru-Hole and SMT.

Here I will discuss some of the most common faults and causes of SMT defects and possible solution and troubleshooting. Read: SMT Troubleshooting (SMT Problem and Solution)