by Kerstin
October 23, 2022
PCB knowledge
(0)
05 mins

SMT process – every intricate detail you must know about it

Have you ever purchased complex mechanical and electrical devices? If yes, you must be curious about the type of working technology it operates.

Thus, today, we will guide you on everything related to SMT process.

The following comprehensive FAQ guide contains all essential questions about SMT process. So, why wait? Let’s start reading!

What is SMT?

SMT or Surface Mount Technology is the modern form of PCB (Printed Circuit Board) used in different mechanical and electrical devices. In this technology, all components and essential elements are directly mounted to the surface of the electric board.

So, wire leads or hole drilling are not used to embed the components into the board. This technology is mainly used to replace the through-hole technology. With the help of SMT process in modern devices, the automated production of different components becomes possible. Thus, devices can be made containing the required assembly of parts.

Furthermore, surface mount technology is known for providing the maximum output to the device by eliminating the bottleneck’s presence on the assembly line.

What is the SMT process?

SMT process is related to the production of surface-mounted technology. It consists of the following essential steps:

●Preparation and examination of materials

The first step of SMT process is related to the production of SMC and PCB materials. You have o examine the flaws in the materials. Also, examine the copper pads containing holes. These pads are commonly known as solder pads.

●Preparation of stencil

Make sure to prepare high-quality stencils. They give a fixed position for solder paste printing so that the solder pads can be designed.

●Printing the solder paste

Try to prepare the solder paste using a mixture of flux and tin. High-quality solder paste combines SMC and solder pads on printed board circuits.

●Place SMC

After preparing the solder paste, place all SMC components on the circuit board using pick and place machines.

●Conduct reflowing of soldering

After the placement of SMC components, the board is subjected to a reflow soldering oven. Here it is introduced to the pre-heat zone, soak zone, and reflow zone. The primary reason for this step is to avoid any joint defect in soldering.

●Clean and inspect the board

The last step is related to the inspection of the board. All flaws are checked in this step.

What is the function of SMT?

The primary function of SMT is the creation of customized electronic circuits in various electrical and mechanical devices. It performs this function by individually mounting different components to the printed board circuit. So, by using Surface Mount Technology, industries can produce customized machines without spending much time on mounting components on circuit boards in a personalized manner. Also another function of SMT is to replace the traditional through-hole mounting system of printed board circuits. Previously, the electric components on PCBs had to pass their leads through the board to perform their functions with full efficiency.

Where is SMT used?

Some devices in which SMT is commonly used are given as under:

USB flash drives
Smartphones
Marine devices
Navigation systems
Medicine and healthcare sector
Pacemakers
MRIs

The primary purpose of SMT in all these devices is to mount different electronic and SMD components on circuit boards.

What are SMT devices?

Three broad categories of SMT devices are given as under:

●Passive SMDs

Many versatile types of packages are used for passive SMDs. These devices can be SMT resistors or SMT capacitors. That is why, depending on the quality, package sizes are standardized. The connections in passive SMDs are made in the metalized areas. These connections can be present on either end of the package. Furthermore, many essential components, such as coils and crystals, are also present in it.

●Transistors and diodes

These are also considered essential devices for SMTs. They play an important role in maintaining the performance of printed board circuits. However, they are present in small plastic packages. The connections of these SMT devices are made via leads. These leads emanate from the desired packaged and molded in a way to touch the board.

●Integrated circuits

Last but not least, SMT devices are known as integrated circuits. These devices contain SMTs of a standard version of DIL (Dual in Line) circuits. Thus, you can incorporate almost 74 series logic chips in these circuits. Additionally, the connections in this SMT device are made according to the level of required interconnectivity.

What are the pros and cons of the SMT process?

Pros of the SMT process are given as under:

This process allows the integration of complex boards with many specialized parts.
You can place components on both sides of circuit boards.
It helps increase the utility per square inch of circuit boards.
This process helps in the production of fully-automated pick systems.
It supports the mass production of delicately printed board circuits.
Also, the SMT processdecreases the manufacturing cost of several devices.

However, some cons of the SMT process are:

Boards can beeasily broken by a slight damage.
It easily drops the components when damaged.
Visual inspection of the board isn’t easy.
It needs a significant investment as it uses SMT machine.
Production needs high training and learning costs.

What are the differences between SMT and SMD?

Some key differences between SMT and SMD are given as under:

SMT is a technical process used in making technology but SMD is a technical device.
SMT places all components on the board by electronic soldering.
Compared to SMT, SMD are the devices having boards with all integrated components.
Also, SMDs increase the device productivity and functionality when compared to SMT.

Considerations for SMT design

Essential considerations for SMT design are explained in the section below:

It must match the Coefficient of Thermal Expansion (CTE) of the PWB and circuit-mounted components.
Also, the soldering surface of the SMT must not be gold plating as it is a catastrophic joint failure.
While choosing the material surfaces, the solderability must be considered as it would help in a better fusion process.
Select circuit components that can sustain various soldering temperaturesin SMT process.
The size of the PWB during design must not be smaller than a requirement.

Conclusion

We have tried our best to quote every necessary detail about SMT process in the above article. But, if you still want to explore the facts, you can refer to IBE PCB & PCBA. It is ensured that you’ll get all your confusion cleared there!