SMT PCB Assembly Manufacturing

SMT (Surface Mount Technology) is a PCB production or assembly method that involves placing and soldering electronic components directly onto the PCB surface. The process requires a solder paste printer to apply the solder paste, a pick-and-place SMT machine for component placement, and a reflow oven to melt the solder and weld components to pads.

SMT is challenging for prototyping because steps like solder paste printing and component placement need stencils and pick-and-place files for specific board designs. Consequently, prototyping can be costly, but it is doable.

An SMD is a Surface Mount Device. An SMD device is mounted on a PCB utilizing surface mount technologies. SMD electronics are designed to not have components with leads that go through holes, as they are soldered onto pads on the surface. SMD parts include resistors, capacitors, and an SMD chip.

SMT is the surface mounting process in this PCB assembly technology, while SMD refers to the component or type of device used.

So, which one technology do you choose for your PCB? Here’s how SMT compares to THT:

Component Size

SMT components are significantly smaller than THT parts, primarily because they have smaller/shorter leads or contact pads. THT devices have larger and longer leads.

Assembly Process

Assembling SMT components requires solder paste printing, component placement using a pick-and-place machine, and reflow soldering. But THT assembly needs component insertion machines followed by wave soldering.

Mechanical Strength

THT provides more robust mechanical bonds with the board because the component pins go through the PCB and are soldered on the other side. These solder joints handle environmental and mechanical stresses better than SMT joints.

Both THT and SMT are technologies used to mount and solder components on a bare board. Here is how SMT is different from the traditional THT:

Higher Component Density

SMT components are significantly smaller than their THT counterparts, so it is possible to pack them at a higher density per unit area on the board’s surface.

Efficient Use of PCB Space

Because they are smaller than THT components, SMT parts occupy less space on the board. This makes it possible to build smaller PCBs or leave more space for other functions.

No Drilling Required

THT creates electrical connections between the board and components by mounting component leads into holes drilled through the PCB. These leads are soldered on the other side of the plated-through hole to create a reliable mechanical and electrical joint.

However, SMT involves mounting components directly on the PCB surface, which requires no drilling.

SMT is important in electronics manufacturing because it:

• Contributes to miniaturization
• Improves PCB reliability (less noise and parasitism)
• Enhances circuit board performance of PCBs (high component density)
• Reduces the production costs

These components are cheaper than their THT counterparts, and the assembly process is easier to automate.

Consumer Electronics

SMT is common in smartphones, laptops, smartwatches, and other compact consumer electronics because of its miniaturization advantage.

Medical Devices

Compact medical equipment like heart rate monitors, EMG, EEG, and ECG sensors, glucometers, and pacemakers require miniaturization, which is one of the benefits of SMT. The reliability offered by SMT is also important in medical devices.

Automotive Industry

Modern vehicles have several control systems and modules that require efficient, stable, and reliable operations. SMT provides these advantages.

Aerospace and Defense

SMT components can weigh up to 10 times less than THT devices, which results in high PCB weight reduction. This factor is important in aerospace and defense applications because lift pulls in the opposite direction of weight. Drones, planes, and rockets benefit immensely from this technology.

Resistors and Capacitors

Resistors are the most common SMD components, and their purpose is to limit the flow of electric current through the circuit. They include various types, such as thin film, thick film, wire-wound, and current-sense resistors.

On the other hand, capacitors store electric charge, functioning as temporary batteries or power supplies in the circuit. They include ceramic, electrolytic, film, and tantalum capacitors.

Integrated Circuits (ICs)

ICs are complex SMT components that have multiple transistors, resistors, diodes, capacitors, etc., on a single chip. They include digital, analog, mixed-signal, and power management ICs.

Diodes and Transistors

Diodes are 2-terminal semiconductors that only allow current to flow in one direction to help in rectification, signal processing, lighting, and voltage regulation. On the other hand, transistors are 3-terminal semiconductors that switch or amplify electric signals.

Inductors and Transformers

Inductors are single coils that store energy in a magnetic field when current flows through them. They are common in power supplies and analog circuits, where they stabilize the current flow and filter out high-frequency noise.

Transformers have at least two coils. They transfer energy from one circuit to another using magnetic induction.

Connectors and Switches

SMD connectors provide electrical connections between the PCB and external devices without permanent attachment (soldering). On the other hand, switches give manual control over the electrical current flow in a circuit.