How are PCBs Fabricated?

PCB fabricate

Printed Circuit Boards offer robust performance of circuitry with durability. Today, from our cell phone to satellites, every electronic equipment contains PCBs for routing signals. The compact size of electronics has been possible mainly because of the compact fabrication of circuitry on PCB.

PCBs have accelerated the advancement in technology and made it possible to add exceptional functionalities in palm size gadgets. Within last few decades, PCB technology has modernized to the extent that an exclusive type of PCB is available for every application.

 

Although millions of PCBs are produced , and the demand is rising with the rise in production. But is it that simple to fabricate a PCB? The printed circuit board (PCB) fabrication demands sensitive handling and various procedures to be followed. The basic steps involved in the PCB fabrication process are described below.

 

Gerber files designing

 

Before a PCB is fabricated, a soft form of circuit is designed using any suitable software such as Altium, Ares, Eagle or OrCAD. The dimensions of pads, tracks, and overall PCB depends upon the dimensions of soft design. Since the design is editable and it enables the designer to make unlimited changes before the hardware is developed.

 

Once a circuit is designed, it is thoroughly checked for any misrouting or flaws and accordingly the design is rectified. After finalization of design, a Gerber file is created which carries detailed information about the PCB design.

 

Photo films

 

These Gerber files are used for printing photo films. The image of a circuit design is printed on these photo films with in-depth details. The purpose of photo films is to route copper tracks on the layers.

 

The conductive and insulated parts of the design are distinguished with colors. At least two films are produced for each layer of PCB. One film illustrates the layer design while the other one shows the solder mask. Their placements need to be aligned as per the soft design.

 

Photo-resistive layer deposition

 

A raw PCB is in the form of a laminated board with an epoxy resin core and a glass fiber substrate. The conductive copper layer is bonded on both sides of PCB. The goal is to keep the copper layer only on conductive paths and remove it from the rest. The copper layer needs to be clean and dirt free otherwise the track markings can be missed on the final prototype. After thorough cleaning, a photoresistive layer is pasted on the copper layer.

Upon exposure to UV light, a trace of design is replicated on the copper layer. The trace hardens, and it is thoroughly washed with an alkaline solution. The copper layer on areas other than design traces is removed. However, the traces are still covered with a photoresistive layer.

 

Optical Punch

 

The layers are punched together using optical punch. Special care must be given to layer alignment to ensure proper punching of registration holes.

The hard design is then scanned by the machine using an optical scanning technique. The machine scans the whole structure from the insides to ensure there are no flaws. Each track is checked with respect to the design in Gerber file.

 

The digital copy serves as the model design for the machine. In case if any flaws are detected, the machine displays detailed information for the assistance of the operator. If there are no flaws, the PCB is moved towards the next stage.

 

Bonding Layers

 

The layers are finalized up to this step, and now they need to be bonded together using a bonding press machine. All layers are adequately aligned by settling in pins on the machine. The pressure, heat and cooling levels need to precise, and the automated machine controls them as needed. After the layers have been bonded together, the final product takes shape.

 

Drilling

 

The board needs to be drilled for placing via holes. The diameter of via holes can vary, but in most of the cases, the diameter of via holes is nearly 100 microns. The process of locating and drilling is delicate and modern systems are automated for this process.

 

Typically a CNC machine locates and drills precisely according to the design requirements. The drill runs at nearly 150,000 rpm but since there are various holes to be drilled the drilling process takes considerable time. Later via holes are filled with vias.

 

Copper Deposition and Layer Imaging

pcb fabrication process

The chemical deposition process is carried out for fusing multiple layers. The product is bathed in chemical and a thin copper layer deposits on the surface. The copper deposits on the insides of the holes too.

 

The photoresistive layer is pasted on the outer layer as per the PCB design. The UV light is directed on it for hardening photoresistive layer.

 

Copper plating and Etching

 

The parts of the board uncovered with photoresistive layer are electroplated with copper. After copper plating, the product is tin plated which secures traces to be saved on the final prototype and removes unnecessary copper marks.

During the Etching process, the unwanted copper is removed leaving behind circuit design.

 

Solder Masking and Ink-Jet writing

 

The hardware is thoroughly cleaned, and solder mask ink is applied to it.  In case of sensitive products such as satellite are to be made using these PCBs, the solder strength needs to be robust, and for that, they are plated with gold or silver.

The information related to components and board specifications is printed on to the board using ink-jet writing.

 

Testing

 

After the PCB has been developed and finalized, various tests are performed for ensuring the PCB performs required functions and is reliable.

 

PCB Fabrication at RAYMING

 

The https://www.raypcb.com/pcb-fabrication/PCB fabrication process is sensitive and demands a high level of expertise. Always choose an experienced fabricator for better results.

Do you know RAYMING offers PCB fabrication facility on latest automated machines? It doesn’t matter if you need a single board or bulk deal, RAYMING has an exciting package for you.

RAYMING offers fabrication of various types of boards including Rigid-Flex PCB, Flexible PCB, Multilayer PCB, Rogers PCB, Aluminium PCB, Heavy Copper PCB, HDI PCB, Microwave and RF PCB, Express PCB and LED PCB.

Have any queries? Contact us at sales@raypcb.com.

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