A printed circuit board (PCB) is the board base for
physically supporting and wiring the surface-mounted and socketed components in
most electronics.

The first product that I have chosen is a mouse. A computer
mouse uses through hole circuit boards to manufacture them. This type of PCB mounts
electronic components by leads inserted through holes on one side of the board
and soldered onto copper traces on the other side. Some of the first ever PCB’s
used through hole technology making it one of the original PCB types. These
circuits may be single-sided, with an unplaited component side, or more compact
double-sided boards, with components soldered on both sides. This type of
circuit is used for a product such as a mouse because it is easily used, and it
has a high speed and high frequent design.

 

Components of through hole circuit boards include:

Electrolyte capacitor: “An
electrolytic capacitor is a type of capacitor that uses an electrolyte to
achieve a larger capacitance than other capacitor types. … Almost all
electrolytic capacitors are polarized, which means that the voltage on the
positive terminal must always be greater than the voltage on the negative
terminal. Electrolyte capacitors can achieve very high capacitance (the ability
of a system to store an electric charge) with very small sizes, but only act as
a capacitor as long as the current flows in one direction (direct current)”

Resistor: “Resistors
are electronic components which have a specific, never-changing electrical resistance.
The resistor’s resistance limits the flow of electrons through a circuit.

 

 

Thermal management

In a pcb circuit, thermal management is critical for a
successful product. This is because if a component gets too hot, it can fail to
work therefor it can lead to a fault in the product. Not only this, overheating
electrical products are huge danger to people and the environment. For the
example I have chosen, a mouse, thermal management is not so much of an issue
because they don’t tend to heat up. However, as technology is advancing, the
deep heating infrared heated mouse technology is becoming more popular. This is
a mouse that heats up to keep your hands warm. This would be an example of
where thermal management would be used with a mouse. A heat management method
that can be used is a fan. “Every computer has a cooling fan inside the
case, designed primarily to prevent the CPU from overheating. Cooling fans may
bring cool air into the computer, draw hot air out of the computer, or as part
of a heat sink, which is a special product designed to draw heat away from a
particular computer component.”  Although a fan can be good to distribute heat
and ventilate a computer, it can also blow dust into the circuit which can
affect how it runs. Another method of thermal management is convective air
cooling. This term describes device cooling by the convection currents of the
warm air being allowed to escape the confines of the component to be replaced
by cooler air. Since warm air normally rises, this method usually requires
venting at the top or sides of the casing to be effective. It is similar to a fan;
however, no power is needed, and the air is escaped through air holes.
Resistance in a circuit will cause the components to fail if it breaches their
temperature specifications. If a circuit is being used and the resistance is
high it can generate enough heat to melt components and soldered joints, making
the circuit stop working. Components can experience thermal cycling. Some
components can’t work in sub-zero temperatures as they freeze. Liquids can be
used to manage temperature – water. The consequences of all these actions are;
it can reduce the life span of the pcb as there is damage to it, it can affect
the efficiency of it, change of electrical characteristics and physical
stresses on components. Therefore, quality control checks are important to
maintain the products sustainability. An example of a quality control method is
Visual inspection. There are two typical types of electrical tests done on a
bare printed circuit board: Flying Probe and Universal Grid.

Advantages and disadvantages of THT (Through-hole technology)

Advantages

Disadvantages

Very reliable. Through-hole soldering creates a stronger bond between
components and the board. This means that it is perfect for large components
the undergo large amounts of power and voltage, as well as mechanical stress.

 

Through hole PBS’s can withstand environmental stress
such as air and wear.

 

Through-hole technology is used in applications that require testing
and prototyping because of the manual replacement and adjustment
capabilities.

 

 

 

 

 

 

 

 

 

The second product
that I have chosen is a usb flash drive. Unlike a mouse, this product uses a Surface
mount (SMT) PCB. Surface-mount technology (SMT) is a method for producing
electronic circuits in which the components are mounted or placed directly onto
the surface of printed circuit boards (PCBs). An electronic device so made is
called a surface-mount device (SMD). “these
components are smaller than the thru-hole type, which allows the design of
smaller and denser printed circuit boards. These types of components are useful
for frequencies up to 200 MHz (fundamental clock frequency).”  

Components of a surface mount PCB include:

Electrolyte capacitor

Tantalum capacitor: Tantalum capacitors are a
subtype of electrolytic capacitors. They are made of tantalum metal which acts
as an anode, covered by a layer of oxide which acts as the dielectric,
surrounded by a conductive cathode. Applications using tantalum capacitors take
advantage of their low leakage current, high capacity and long-term stability
and reliability.

Inductors

An inductor is just a coil of wire around a core. The core
could be just air, or it could be a magnet. When you apply a current through
the inductor, a magnetic field is created around it. By using a magnetic core
the magnetic field will be much stronger.

Thermal management

USB PD ports provide a great way to quickly charge small
portable electronics and even replace the charging cables currently used for
laptops. With the increased power density and small solution size, concerns
about proper thermal management are valid. TI offers several solutions that
enable you to fully leverage the power-delivery capabilities of USB PD and
maintain a safe operating temperature for both the system and end user.

In a circuit board such as a surface mount pcb contained in
a usb, there are many components that 
can heat up. As a result of components heating up, it can cause the
solder to be melted which will damage it. Components like a resistor will heat
up the most, especially if it has a high resistance. It is significant to carry
out quality checks often to make sure that the product is working at its best
ability. For a USB, you can manage the heat by ejecting it from the computer
device for 10 to 15 seconds to stop it from overheating. The heat is
transferred from the USB port to the flash drive (USB)

Advantages and disadvantages of SMT (surface mount
technology)

Advantages

Disadvantages

Much smaller components compared
to through – hole technique

SMT is not very efficient
for high voltage or high power circuits

There are more connections
per component

SMDs’ solder connections may
be damaged by potting compounds going through thermal cycling.

Components can be placed on
both sides of the circuit board.

Many types of SMT component
packages cannot be installed in sockets

There is a much better
mechanical performance under shock and vibration conditions

Usually smaller than through
hole components, therefore there is less surface area so less space for ID
codes so it is hard to read.

SMT circuit boards are
easier and faster to assemble

 

Many SMT parts cost less
than the same through-hole parts.