What is SMT process & SMT manufacturing?

SMT stand for Surface Mount Technology. SMT
is replacement of “Through Hole Technology-THT”. 

Through hole technology is mounting scheme used for
electronic components that involves the us
e of leads on the component that are inserted into holes drilled in PCB,
solder to other side manually.

Through Hole technology is reserve for heavy & sulkier
components. While SMT is advance,  increases manufacturing automation. SMT
components have no leads. Actually there is no need of components leads to pass
through the hole. It is adequate for components to be soldered directly to the
board. For this SMT was born.

SMT vs Through Hole Technology

Before going further in details of PCB we have to understand some “Basic of Electronics here.  

study of the behavior of an electron under different conditions of externally
applied fields. 

Electronic Components:-

There are 5 components- 3 Passive & 2 active

  • Active– Diode, Transistors & ICs
  • Passive– Resistor, Capacitor & Inductor
component:- Active components are those that deliver or produce energy or power
in the form of a voltage or current.

component:- Passive components are those that utilize or store energy in the
form of voltage or current.

In Simple PCB we found components like- Resistor,
Capacitor, diode, LED, etc.

What resistor does in

receive a voltage and restrict the amount of current that flows through it. 

What Diode does in

Diode is an electronic component, which allows the flow of
current in one direction. Diode serves as a gate keeper, allow current to flow
at a certain minimum or break-over voltage, in one direction.  Most common type of diode is p-n junction

Capacitor does in PCB?

is an electronic device that stores electric energy. The function of capacitors
is to temporarily hold electric charge, and release it whenever more power
is needed elsewhere in the circuit.

PCB Components Details

What are leads in PCB?

Lead in electronic is an electrical connection from electric
pole of an electronic part/Electronic components.

Through Hole technology is reserved for heavier &
bulkier components (Electrolytic capacitor / semiconductor). SMT is advance
technology, increase manufacturing automation. In SMT components have no leads,
there is actually no need for component lead to pass through the board. It is
easy or adequate for component to be soldered directly though the board. For
this SMT was born.

SMT vs THT, Components details in PCB


What are Vias in any

 It is an electrical connection between copper layers
in PCB. The holes are plated hole (Gold plating). Copper layer are conductive
rest material is non conductive.

What are Vias in PCB

 What are SMT

SMT components are design to set down on board. All SMT
components are called SMC (Surface Mount comp). SMC are classified in Passive
SMD (Here resistor & Capacitor), Transistor Diode and Integrated
circuit.  In PCB assembly process most of
the components on board are placed automatically. SMC are smaller in size.

SMT Components and its Types

What is SMT

SMT soldering is stand for surface mount soldering, and it
is process of connecting SMD components which are mounted directly on to the
surface of PCB. The SMD connection by SMT is done using  solder paste.

The soldering processes required for SMDs during the PCB
assembly needs to ensure the components are held in place during the soldering,
the components are not damaged, and the final soldered quality is exceedingly

There are two
main methods for SMT soldering:-

  1. Wave Soldering
  2. Reflow Soldering

What is solder paste?

paste is a mixture of minute solder spheres and specialized form of solder
flux. And solder flux is nothing but chemical substance used to clean the
surface of PCB board. Since mixture of these two make paste like texture, so we
call solder paste.

Solder flux is cleaning agent that helps in removing oxides
and impurities from the surfaces. It helps in effectively soldering the
joints by cleaning the surface.

Solder Grade:- Grade
of solder depend upon size of solder ball. There are around 8 grade. Type1 to
type 8- As the size reduce grade size increases.  Example- Type 8 solder paste grade- Solder
ball size is 2~8 mm.

What is solder Paste & Solder Flux

What is Solder Flux?

It is chemical substance used in PCB assembly. It is
cleaning agent that helps in removing oxides and impurities from the surfaces. It
helps in effectively soldering the joints by cleaning the surface. 

Type of Solder Flux:-

  1. Rosin Based solder paste
  2. Water soluble flux paste
  3. No clean solder paste

Article on SMT process and PCB manufacturing is covered in next article. Visit learnmytool.com for related article. 

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