SMD Vs SMT: What's the Difference?

Surface Mount Technology, often known as SMT, is the process of soldering different electronic components like integrated circuits, transistors, capacitors, and resistors onto printed circuit boards, also known as PCBs.

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Surface-mount devices are yet another name for the components utilized. It must be emphasized that SMT is substantially smaller compared to thru-hole insertion technology and does not require equivalent through holes to be reserved for the component pins.

What is SMD SMT?

When it comes to electrical function, SMD SMT components are identical to through-hole components. SMD which means Surface Mount Device is a part of an electrical device that attaches to the printed circuit board&#;s surface (in contrast to the &#;thru-hole&#; components that have pins which are inserted in the holes).

SMD SMT often allows for more components for every centimeter square of PCB board, however due to their size, manual assembly as well as prototyping might well be challenging.

An SMD, also known as surface mount device, is one essential features of surface mount technology. The markets are filled with different SMD packages.  The sizes and dimensions of these packages vary.

SMD were initially soldered by hand. Furthermore, the initial crop of the pick and the place machines was limited to a few basic components. The smaller, more intricate parts still required hand placement. A new age began just before the components of the surface mount were introduced more than two decades ago.

Today, practically all thru-hole component has SMT equivalent, from straightforward resistors to intricate and complex ICs.

Categories of SMT Devices

Devices that utilize surface mount technology are known as SMDs or surface mount devices. Instead of being wired in-between two places as would be the case for thru hole technology, the individual components utilized are specifically made to be directly soldered onto a board. The three primary types of SMT components are as follows.

Passive SMDs

Capacitors or resistors make up most passive SMDs. Other components, such as crystals, coils, and others, typically have more precise needs, while the packaging sizes are generally standardized.

Integrated circuits

Read our article to learn more about ICs (integrated circuits) generally. They might vary significantly in regard to SMD in particular based on the required connectivity.

Diodes and Transistors

Small plastic packages are frequently used to house diodes and transistors. Leads connect as well as make contact with the board. The bundles employ three leads majorly.

SMD Component Types

Discrete Surface Mount Resistors (SMD Resistors)

Surface mount resistor can come in two basic varieties: thick film as well as thin film.

As contrast to axial resistors, which deposit resistive films on the thick film, circular core surface mount resistor is made by the screening resistive films (a paste based on ruthenium dioxide or comparable substance) on a high, flat alumina substrate surface. Before screening, the resistive paste composition is changed, and after screening, the film is laser-trimmed to determine their resistance value.

In the thin film resistor, the resistive elements are mounted onto a ceramic substrate having solderable terminations on its sides and a protective covering (glass passivation) present on top. On ceramic substrates, the terminations include an adhesive layer (a silver that is deposited like a thick-film paste), a nickel barrier, and either a plated or dipped solder covering.

On ceramic substrates, the terminations include an adhesive layer (a silver that is deposited like a thick-film paste), a nickel barrier, and either a plated or dipped solder covering. Because it resists leaching of the gold or silver electrode throughout SMD soldering, its nickel barrier plays a huge role in maintaining the terminations&#; solderability.

Tantalum Surface Mount Capacitors

Tantalum or ceramic can be used as the dielectric in Surface Mount capacitors. Tantalum surface-mount capacitors provide high capacitance-voltage for every unit volume as well as a high volume efficiency.

Leads rather than terminations as well as beveled top that serves as the polarity indicator are features of a wrap-under lead capacitor, also known as plastic-molded tantalum capacitors. The plastic molded tantalum capacitors can be used without having to worry about soldering or location. There are two sizes available for them: extended and standard range.

Ceramic Capacitors for SMT

Because they have no leads and may be positioned beneath the package just on opposing side of a PCB Assembly, surface mount capacitors particularly are perfect for circuit applications of high frequency.

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A packaging that is mostly utilized for the ceramic capacitor is the 8 mm tape with the reel. Also, surface mount capacitors play a role in the decoupling of applications as well as frequency control.

Advantages of SMT

Slimmer and smaller PCB: Compared to Thru-Hole, SMD Components usually have a size of 60&#;80% less. These components are also substantially less in weight. They take up less room on SMT PCB as a result, making it slimmer and smaller.

PCB Flexibility: Surface Mount Technology provides great flexibility regarding PCB design and material since the SMD Components comes directly soldered or mounted on the board&#;s surface. Only SMT makes it possible for flex PCB as well as rigid-flex PCB to exist.

Cost Savings on Board and Materials: SMT PCBs seem to be smaller in size and don&#;t require any plated through holes. Additionally, a lot of SMD components are less expensive than through-hole electronic components. That lowers the cost of manufacturing SMT PCBs.

Disadvantages of SMT

Equipment that costs a lot

The majority of SMT equipment costs a lot, including the reflow oven, the pick & place device, screen printer for solder paste, and SMD hot air rework station.

Inspection is challenging

This is because the majority of SMD components comes tiny and contains several solder joints. The solder joints and balls under this component make BGA Packages particularly challenging to check. Additionally, SMT inspection tools are highly expensive.

Can be damaged easily

SMD components may readily get damaged if they are dropped. Additionally, they require ESD products to ensure the packaging and handling due to their high ESD sensitivity.

Conclusion

SMD SMT are comparable. There are a plethora of SMD packages available. You often require a special circuit board created for them that has a copper matching pattern which they will be soldered, to work with surface-mount boxes.

What is the difference between SMT and SMD

SMT stands for Surface Mount Technology, the entire technology of mounting and soldering electronic components, such as resistors, capacitors, transistors, integrated circuits, onto a printed circuit board or PCB. The components used are also referred to as surface-mount devices (SMD, surface-mount devices). It should be noted that SMT does not need to reserve corresponding through holes for component pins, and SMD is much smaller than through-hole insertion technology.

Features of SMT:

• Components have no leads or only short leads;
• The main body of the component and the solder joint are on the same side of the PCB;

Features of SMD:

• miniaturization;
• No lead (flat or short lead);
• Suitable for surface assembly on PCB;

In the early stages, SMD were soldered manually by hand. Then the first batch of pick and place machines could only handle a few simple components. The more complex and smaller components still needed to be placed manually. Not long before the introduction of surface mount components over 20 years ago, a new era was born. From simple resistors to complex ICs, almost every through hole component now has an SMT equivalent.

The actual process of SMT

• Firstly, a PCB stencil is aligned on the surface of the boards and solder paste is applied using a squeegee to ensure the pads are coated with a uniform and controlled amount of solder paste.
• Secondly, via a pick and place machine or hand placement, the components are mounted onto the boards in their respective locations. The wet solder paste will act as a temporary adhesive but it is still important to ensure that the boards are moved gently to prevent misalignment.
• Thirdly, the boards are passed through a reflow oven which subjects the boards to infrared radiation, melting the solder paste and forming solder joints.Then the boards are passed through an AOI machine, or Automatic Optic Inspection machine which runs a number of quality checks on the boards visually, such as component alignment and checking for solder bridges. The boards then proceed to further testing.

In the s, SMT production technology became increasingly more refined and as a result, is widely used in mass production. As costs were reduced and technical performance enhanced, more advanced but economical equipment became available.

Types of SMD

Passive components

• resistance
• capacitance
• inductance
• Composite device

Discrete components

• integrated circuit
• Active device

Electromechanical devices

• Switch/relay
• Connector
• Micro-motor

Advantages of SMT

• Reduce PCB area;
• Reduced weight
• Installation is easy to automate;
• Reduce parasitic capacitance and parasitic inductance;
• Improve product quality and reliability;

SMT brought with it a new generation of electronic assembly technology, which is widely applied in applications from aviation, communications, automotive and medical electronics, down to household appliances and other fields.

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