What is a PCB main assembly?

20 Jan, 2022

By ren

What is a printed circuit board (PCB)?

The most frequent moniker is "PCB," however it could also be called "printed wiring board" or "electronic circuit cards." Before the Printed circuit boards, connections were built by a time-consuming process of juncture wiring. As wire wrapping started to deteriorate and fracture, that resulted in frequent breakdowns at wire connections and tripping. The advent of wires wrapping, where a thin thread cable is wrapped around with a post at every point of connection, providing a gas-tight, extremely robust, and readily adjustable connector, was a big step forward.

The size and cost of electrical parts began to decrease when electronics transitioned beyond vacuum tubes as well as switches to silicone and electronic components. Electricals grew more prominent in goods and services, and the drive to minimize electronic item design and cost of production prompted manufacturers to seek better alternatives. As a result, PCBs were developed.

PCB manufacturing

A PCB is similar to a layer cake or lasagna except that it is made up of alternating layers comprising material properties that are bonded together along with heat and glue to form a single entity.

Flame retardant

Fiberglass is frequently used as a feedstock or substrate. flame retardant has been the most popular design challenge for this fiberglass in the past. The stiffness and density of the PCB are owed towards its solid core. Retractable PCBs made from the soft warmness of plastics are also available. There are a variety of PCB thicknesses available; the most typical size for SparkFun items is 1.6mm (0.063"). A 0.8microns thick board is often used in certain manufacturing goods, such as LilyPad and Arduino Pro Micro board.

Such substrate material is indeed commonly used in low-cost consumer devices. When the soldering iron is kept just on the circuit for far too long, phenolics delaminate, smoke, or char due to low thermal degradation temperatures.

Copper layer

The following layer is a thin copper foil that is heated, and adhesives bonded to the printed circuit board. Copper is placed on both surfaces of such base on most double-sided PCBs. In low-cost electrical devices, the PCB assembly should only have a copper layer across one side. The amount of copper layers (2) is known as a dual side or 2-layer board. It is possible to have as little as one layer and as many as 16 layers and more.

The density of copper traces varies and is indicated by mass, in ounce every square foot. The vast bulk of PCBs has one ounce of copper each square foot, however certain PCBs that manage extremely high voltage may include two or three ounces of copper. Each ounce per square equates to approximately 35 micrometers of copper density.

Solder mask layer

The solder mask layer is the layer that appears at the top of such copper foil. This layer is responsible for the PCB's green (or, in the case of SparkFun, red) hue. It is layered well over the copper layer to protect the copper cables from interaction with other metal, soldering, or conductive components. This layer assists users in soldering in the proper locations and preventing solder jumpers.

The green solder mask is placed to the bulk of a Printed circuit board in the illustration below, concealing the little copper traces while letting the metal clasps and SMD pad visible be joined to.

Silkscreen layer

On over of the solder mask layer, a white silkscreen component is put. The silkscreen puts lettering, figures, and symbol on the PCB to simplify assembly simpler and to help people comprehend the board better. Silkscreen tags are frequently used to identify the purpose of every pin and LED.

The most frequent silkscreen color is white, however, any print color could be used. Silkscreen colors in black, grey, reddish, or even yellowish are frequently accessible; nonetheless, it is unusual seeing more than a hue on a single printed circuit board.

The three main kinds of PCBs are as follows:

Rigid PCB: The most prevalent form of PCB foundation, accounting for the bulk of Printed circuit board assembly, is indeed a rigid PCB. The stiff PCB's rigidity and thickness are provided by the board's solid core. These rigid PCB bases are made of a variety of materials. The most popular is fiberglass, often known as "FR4". Fewer cost PCBs are produced using epoxies or phenolics, however, they are less durable than FR4.

Flexible PCB: Flexible PCBs are a little more malleable than their more stiff equivalents. These PCBs are often made of flexible, increased plastic such as Kapton.

Metal Base PCB: These PCBs are an additional option to the standard FR4 board. These boards, which have a metal core, disperse heat greater efficiently than others. That aids in heat dissipation and protects more high-temperature board elements.

Terms of PCB assembly services

Let us just clarify some phrases you might encounter while working with Printed circuit board assembly nowadays that you know what a PCB construction is:

  • An annular ring is a copper ring that surrounds PTH components on a Printed circuit board.
  • DRC stands for design rule check. A computerized analysis of your design is to ensure there were no defects including such traces that contact wrongly, traces that were too slender or drill a hole that is too tiny.
  • Drilling hit - a PCB assembly process in which locations on a layout in which a-holes must be bored and where the hole was successfully drilled just on board. Drilling strikes that are incorrect due to dulled bit are a typical production problem.
  • Finger-metal surfaces pads all along the border of a board that is used to connect printed circuit boards. Instances include the borders of computer expansions or storage boards, as well as earlier cartage computer games.
  • Pad is a piece of uncovered metal just on board's base with which a component is joined.
  • Panel - a bigger printed circuit board made up of numerous smaller boards that will be disassembled before usage.
  • Board size commonly causes problems for automated PCB board material handling, and so by combining numerous boards in at once, the operation may be considerably sped up.
  • Pick-and-place: device or procedure for deemed significant on a printed circuit board.
  •   Plated through-hole - holes on printed circuit board with a circumferential ring that is layered together all way around. It might be a connecting point for a through-hole component, a signal via, or surface mount components.
  • Reflow soldering entails heating the solder to form connections among pad and components leads.
  • Slots - any non-round hole in aboard. Slots can be lined accept or reject. Slots can occasionally increase the price of the board since they demand more cut-out time.
  • Solder paste consists of small pellets of solder coated together in a gel medium that is deposited towards the surface mount components of a circuit board assembly pcba using a paste stencil first before components are installed. The solder inside the paste melts after reflow, forming electromechanical connections between both the pads and the components.
  • Solder pot: a pot for swiftly soldering boards together through-hole components by hand. Usually has a little quantity of hot solder in it that the board is swiftly dipped into, creating solder paste on all accessible pads.
  • Solder mask ensures that the right of substance is applied to a metal surface to avoid short circuits, corrosion, and other issues. Green is the most common color, however other colors are also conceivable. Sometimes referred to as resist. 
  • Solder jumpers - a little glob of manual soldering different neighboring pins on a power circuit board component. Solder jumpers could be used to link two pads or pins simultaneously, due to the design. This can result in unwelcome shorts.
  • Surface mount technology - surface mounting is an approach that allows elements to be readily placed on an assembled board without the need for leads to travel through holes on the boards. This is the most commonly used form of assembling today, and it allows circuits to be filled quickly and effectively.
  • Wave soldering is a soldering method used for the printed circuit boards with tht components that involve passing the board more than a wave of molten material, which sticks to visible pads and components leads. Inspection of PCB: Usually conventional Printed circuit assembly process will continue with an automatic optical inspection of the board, soldered, and elements.


Printed circuit boards are elaborately constructed pathways made by metallic implantations that enable power to flow smoothly to the elements of technological devices. This simple transfer of electric electricity allows electronic gadgets to run smoothly and without disruption. Authorized the formation of printed circuit boards, a next necessary stage is to properly combine components for such mechanism's completeness.


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