What is the difference between through-hole and surface mount?(1/7)

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1. T hole to install | PCB assembly

1.1 What is THM (Through-Hole Installation) -T through-hole technical information!

THM refers to "through-hole installation" also known as "THM" "through-hole" or "through-hole technology" "THT". Through-hole mounting is the process of placing component leads into a borehole on an exposed PCB, a predecessor of surface mounting technology.

Over the past few years, the electronics industry has grown steadily due to the increasing use of electronics in all aspects of human life. The printed circuit board (PCB) industry is growing as the demand for premium and micro products grows.

Through-hole technology has been used in the construction of almost all printed circuit boards (PCBS) for many years. Although through-hole mounting provides greater mechanical bonding than surface mounting techniques, the additional drilling required makes the circuit board more costly to produce. This also limits the available wiring area for signal routing on the multilayer board, as the holes must pass through all layers to reach the opposite side. These problems are just two of the many reasons why surface mounting technology was so popular in the 1980s.

Through-hole technology replaced earlier electronic assembly techniques, such as point-to-point construction. From second-generation computers in the 1950s to surface mount technology that became popular in the late 1980s, every component on a typical PCB was a through-hole component.

Today, PCBS are smaller than they used to be. Mounting various components on the circuit board is challenging due to its smaller surface. To mitigate this, manufacturers are using two technologies to install electrical components onto circuit boards. These technologies are electroplating through-hole technology (PTH) and surface mount technology (SMT). PTH is one of the most commonly used technologies used to mount electronic components, including microchips, capacitors, and resistors, onto circuit boards. In through-hole assembly, the lead wire is threaded through the pre-drilled hole to form a cross pattern on her side of the OT.

1.2 hole components | what they are and how they work?

1) Type through-hole assembly

Before you begin, you should understand some basic electronic components. There are two basic types of electronic components, active and passive. Here are the details of both classifications.

● Active components

● Passive components

Active ingredients

What are active electronic components?

Active electronic components are components that can control current. Different types of printed circuit boards have at least one active component. Some examples of active electronic components are transistors, vacuum tubes, and thyristor rectifiers (SCRS).

Such as:

Diode - two terminal components of the current in a major direction. It has low resistance in one direction and high resistance in the other direction

Rectifier - device that converts alternating current (changing direction) to direct current (in one direction)

Vacuum tube - A tube or valve that conducts an electric current through a vacuum

Function: Active components manage current. Most PCBS have at least one active component.

From a circuit point of view, active components have two basic functions:

● The active components themselves consume power.

● In addition to the input signal, an external power supply must be used.

Passive components

What are passive electronic components?

Passive electronic components are those that do not have the right to control the current flowing through another electrical signal. Examples of passive electronic components include capacitors, resistors, inductors, transformers, and some diodes. These may be square holes in the SMD component.

2) Type of plated through-hole element (PTH)

The PTH component is called a "through-hole" because the leads are inserted through the copper plated holes in the circuit board. These components have two types of leads:

● Axial lead assembly

● Radial lead assembly

Axial lead component (ALC) :

These components may have one or more leads. Cause the lead to lead out of one end of the component. During electroplating through-hole assembly, both ends pass through separate holes in the circuit board. Therefore, the components are placed closely on the circuit board. Electrolytic capacitors, fuses, light-emitting diodes (leds), and carbon resistors are some examples of axial components. These components are preferred when manufacturers are seeking a compact fit.

Radial lead Assembly (RLC) :

The leads of these components extend out of their bodies. Radial leads are mainly used on high-density boards because they take up less space on the circuit board. Ceramic disc capacitor is one of the important types of radial lead assembly.

Such as:

Resistor - an electrical component with resistance at both ends. Resistors can reduce current, change signal level, partial voltage, etc.

Capacitors - These components can store and release charges. They can filter the power line and block the DC voltage while allowing the AC signal to pass through.

Sensors - Also known as detectors, these components react by changing their electrical characteristics or transmitting electrical signals

From a circuit point of view, passive components have two basic characteristics:

● Passive components themselves consume electricity or convert it into other energy in other forms.

● Only input signals, there is no need to work properly.

Function - Passive components cannot use other electrical signals to change current.

Together, these components constitute a much safer and more convenient process than in the past by assembling printed circuit boards (including surface mount technology and through-holes). Although these components may become more complex in the coming years, the science behind them is timeless.

3) P type related through-hole circuit board components

Like all other components, electroplated through-hole circuit board components can be roughly divided into:

● The through-hole should be positive. component

● Through hole passive assembly.

Each type of component is mounted to the board in the same way. Designers need to place through-holes in their PCB layout where pads on the surface surround them with pads for soldering. The through-hole installation process is simple: the component leads are placed into the hole, and the exposed leads are soldered to the pad. Electroplated through-hole circuit board elements are large and sturdy and can be easily welded by hand. For passive through-hole assemblies, component leads can be long, so they are usually cut short before installation.

Passive through-hole assembly

Passive through-hole elements are packaged in two possible forms: radial and axial. The electrical wires of the axial through-hole assembly extend along the symmetry axis of the assembly. Consider a basic resistance; The wire runs along the cylindrical axis of the resistor. Diodes, inductors and many capacitors are installed in the same way. Not all through-hole components come in cylindrical packages; Some components, such as high-power resistors, have rectangular packages with leads extending along the length of the package.

Meanwhile, the radial component has electrical leads protruding from one end of the component. Many large electrolytic capacitors are packaged in this way, thus allowing them to be mounted onto the board by passing leads through the hole pad while occupying less space on the circuit board. Other components such as switches, leds, small relays and fuses are also packaged as radial through-hole components.

Active through-hole element S

If you remember electronics courses, then you probably remember integrated circuits used with dual in-line packaging (DIP) or plastic DIP (PDIP). These components are often seen as being mounted on breadboards for proof-of-concept development, but they are often used in actual PCBS. DIP packages are commonly used for active through-hole components, such as operational amplifier packages, low power regulators, and many other common components. Transistors, higher power regulators, quartz resonators, higher power leds and other components may be packaged in zigzag series (ZIP) or transistor shape (TO) packages. Just like axial or radial passive through-hole technologies, these other packages are mounted to the PCB in the same way.

The emergence of through-hole components comes at a time when designers are more concerned with making electronic systems mechanically stable and less concerned with aesthetics and signal integrity. Little attention is paid to reducing the space occupied by components, and signal integrity issues are not an issue. Later, as power consumption, signal integrity, and board space requirements began to take center stage, designers needed to use components that provided the same electrical functionality in a smaller package. This is where the surface mount element enters.

Please stay tuned for the complete article in the next issue