What is PCB (Printed Circuit Board) ?

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Definition:

A PCB is a Printed Circuit Board, and used to mechanically support and electrically connect electronic components using conductive pathways (copper traces), signal traces etched from copper sheets laminated onto a non-conductive substrate Glass Epoxy (FR4).

Also PCBs are a composite of organic and/or inorganic dielectric materials with many layers with wiring interconnects and also house components like inductors and capacitors. There isn’t any standard printed circuit board as such and each board is unique, often a function of the product itself.

PCB Design Layers:

A PCB design package allows the designer to define and design on multiple layers.

Many of these are physical layers such as:

• Signal Layer

• Power plane Layer

• Mechanical Layer

And some are special layers such as:

• Solder & Paste Mask Layers

• Silkscreen or Top Overlay Layers

• Drill guides

• Keep-out Layer

Types of PCB:

A PCB can be of four types: Rigid board , Flexible board and Rigid-flex board, Metal-core and Injection Molded boards out of which the Rigid board is the most popular. Further these may be Single Sided, Double Sided or Multilayer. 

The mechanical, electrical, chemical and thermal properties of the material should be considered while making PCBs otherwise the reliability of the board suffers. Presently, copper-clad laminates of different reinforced resin systems are used in rigid boards. Examples include Fire resistant FR-4 epoxies, PTFE, cyanate esters, polymides etc. Most commonly used reinforcement material is continuous filament E-Glass. Flexible and rigid flex-boards have random arrangements of conductors on a flexible base and may be with/without cover layers. Here, the wiring is restricted to select areas of the plane. In case of constraining metal core technology, the PCB can be of standard materials but the core materials must have low Coefficient of Thermal Expansion and strength to constrain the PCB. Copper-Invar-Copper and Copper-Molybdenum-Copper are two popular materials for this purpose. Molded boards have resins containing fillers which are molded into a die to form the required shapes.

What is PCB Board Design?

• PCB board design defines the electrical pathways between components
• It is derived from a schematic representation of the circuit
• When it is derived, or imported from a schematic design, it translates the schematic symbols and libraries into physical components and connections

PCB Manufacturing Process:

Step 1: Film Generation

The film is generated from the design files (Gerber/CAM files) which are sent to the manufacturing house. One film is generated per layer

Step 2: Raw Material

Industry standard 0.059” thick, copper clad panel

Step 3: Drill Holes

Using NC machines and carbide drills to drill holes according to the drill spec sent to the manufacturing house

Step 4: Electroless Copper

Apply thin copper deposit in hole barrels

Step 5: Apply Image

Apply photosensitive dry film to panel and use a light source and the film to expose the panel

Step 6: Pattern Plate

Electrochemical process to build copper in the holes and on the trace areas. Apply tin to surface

Step 7: Strip and Etch

Remove the dry film, and then etch the exposed copper. The tin protects the copper circuitry from being etched away

Step 8: Solder Mask

Apply a solder mask area to the entire board with the exception of solder pads

Step 9: Solder Coating

Apply solder to pads by immersing into tank of solder. Hot air knives level the solder when removed from the tank

Step 10: Nomenclature(Silk Screen Printing)

Apply white letter markings using screen printing process

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