Printed circuit board (PCB) are the cornerstone of almost all electronic devices. These amazing PCB can be found in many advanced and basic electronics, including Android phones, laptops, computers, calculators, smartwatches and more. In very basic language, a PCB is a board that routes electronic signals in a device, which results in the electrical performance and requirements of the device being set by the designer.

The PCB consists of a substrate made of FR-4 material and copper paths throughout the circuit with signals throughout the board.

Prior to PCB design, the electronic circuit designer must visit the PCB manufacturing workshop to fully understand the capacity and limitations of PCB manufacturing. Facilities. This is important because many PCB designers are not aware of the limitations of PCB manufacturing facilities and when they send a design document to a PCB manufacturing shop/facility, they return and request changes to meet the capacity/limits of the PCB manufacturing process. However, if the circuit designer works for a company that does not have an in-house PCB manufacturing shop, and the company outsources the work to a foreign PCB manufacturing plant, then the designer must contact the manufacturer online and ask for limits or specifications such as maximum copper plate thickness per minute, maximum number of layers, minimum aperture and maximum size of PCB panels.

In this paper, we will focus on THE PCB manufacturing process, so this paper will be helpful for circuit designers to gradually understand the PCB manufacturing process, to avoid design mistakes.

PCB manufacturing process steps

Step 1: PCB design and GERBER files

< p> Circuit designers draw schematic diagrams in CAD software for layout PCB design. The designer must coordinate with the PCB manufacturer about the software used to lay out the PCB design so that there are no compatibility issues. The most popular CAD PCB design software is Altium Designer, Eagle, ORCAD and Mentor PADS.

After the PCB design has been accepted for manufacture, the designer will generate a file from the PCB manufacturer’s accepted design. This file is called a GERBER file. Gerber files are standard files used by most PCB manufacturers to display components of the PCB layout, such as copper tracking layers and welding masks. Gerber files are 2D vector image files. The extended Gerber provides perfect output.

The software has user/designer defined algorithms with key elements such as track width, plate edge spacing, trace and hole spacing, and hole size. The algorithm is run by the designer to check for any errors in the design. After the design is validated, it is sent to the PCB manufacturer where it is checked for DFM. DFM (Manufacturing Design) checks are used to ensure minimum tolerances for PCB designs.

< b> Step 2: GERBER to photo

The special printer used to print PCB photos is called a plotter. These plotters will print circuit boards on film. These films are used to image PCBS. Plotters are very accurate in printing techniques and can provide highly detailed PCB designs.

The plastic sheet removed from the plotter is a PCB printed with black ink. In the case of the inner layer, the black ink represents the conductive copper track, while the blank part is the non-conductive part. On the other hand, for the outer layer, the black ink will be etched away and the blank area will be used for the copper. These films should be stored properly to avoid unnecessary contact or fingerprints.

Each layer has its own film. The welding mask has a separate film. All these films must be aligned together to draw PCB alignment. This PCB alignment is achieved by adjusting the workbench to which the film fits, and optimal alignment can be achieved after minor calibration of the workbench. These films must have alignment holes to hold each other accurately. The locating pin will fit into the locating hole.

Step 3: Inner printing: photoresist and copper

These photographic films are now printed on copper foil. The basic structure of a PCB is made of laminate. The core material is epoxy resin and glass fiber called the base material. The laminate receives the copper that makes up the PCB. The substrate provides a powerful platform for PCBS. Both sides are covered with copper. The process involves removing copper to reveal the design of the film.

Decontamination is important for cleaning PCBS from copper laminates. Make sure there are no dust particles on the PCB. Otherwise, the circuit may be short or open

Photoresist film is now used. Photoresist is made of photosensitive chemicals that harden when ultraviolet radiation is applied. It must be ensured that photographic film and photoresist film match exactly.

These photographic and photolithographic films are attached to the laminate by fixing pins. Now ultraviolet radiation is applied. The black ink on photographic film will block ultraviolet light, thereby preventing the copper underneath and not hardening the photoresist beneath the black ink traces. The transparent area will be subjected to UV light, thereby hardening the excess photoresist that will be removed.

The plate is then cleaned with an alkaline solution to remove excess photoresist. The circuit board will now dry.

PCBS can now cover the copper wires used to make circuit tracks with corrosion repellents. If the board is two layers, then it will be used for drilling, otherwise more steps will be taken.

Step 4: Remove unwanted copper

Use a powerful copper solvent solution to remove excess copper, just as an alkaline solution removes excess photoresist. The copper beneath the hardened photoresist will not be removed.

The now hardened photoresist will be removed to protect the required copper. This is done by washing off the PCB with another solvent.

Step 5: Layer alignment and optical inspection

After all the layers have been prepared, they align with each other. This can be done by stamping the registration hole as described in the previous step. Technicians place all the layers in a machine called an “optical punch.” This machine will punch holes accurately.

The number of layers placed and errors that occur cannot be reversed.

An automatic optical detector will use a laser to detect any defects and compare the digital image to a Gerber file.

Step 6: Add layers and bindings

At this stage, all the layers, including the outer layer, are glued together. All layers will be stacked on top of the substrate.

The outer layer is made of fiberglass “preimpregnated” with an epoxy resin called preimpregnated. The top and bottom of the substrate will be covered with thin copper layers etched with copper trace lines.

Heavy steel table with metal clamps for bonding/pressing layers. These layers are tightly fastened to the table to avoid movement during calibration.

Install the prepreg layer on the calibration table, then install the substrate layer on it, and then place the copper plate. More prepreg plates are placed in a similar manner, and finally the aluminum foil completes the stack.

The computer will automate the process of the press, heating the stack and cooling it at a controlled rate.

Now technicians will remove the pin and pressure plate to open the package.

Step 7: Drill holes

Now it’s time to drill holes in stacked PCBS. Precision drill bits can achieve 100 micron diameter holes with high precision. The bit is pneumatic and has a spindle speed of about 300K RPM. But even with that speed, the drilling process takes time, because each hole takes time to drill perfectly. Accurate identification of bit position with X-ray based identifiers.

Drilling files are also generated by the PCB designer at an early stage for the PCB manufacturer. This drill file determines the minute movement of the bit and determines the location of the drill.These holes will now become plated through holes and holes.

Step 8: Plating and copper deposition

After careful cleaning, the PCB panel is now chemically deposited. During this time, thin layers (1 micron thick) of copper are deposited on the surface of the panel. Copper flows into the borehole. The walls of the holes are completely copper-plated. The entire process of dipping and removal is controlled by a computer

Step 9: Image the outer layer

As with the inner layer, photoresist is applied to the outer layer, the prepreg panel and the black ink film connected together have now burst in the yellow room with ultraviolet light. Photoresist hardens. The panel is now washed by machine to remove the hardening resist protected by the opacity of the black ink.

Step 10: Plating outer layer:

An electroplated plate with a thin copper layer. After the initial copper plating, the panel is tinned to remove any copper left on the plate. Tin during the etching phase prevents the required portion of the panel from being sealed by copper. Etching removes unwanted copper from the panel.

Step 11: Etch

Unwanted copper and copper will be removed from the residual resist layer. Chemicals are used to clean excess copper. Tin, on the other hand, covers the required copper. It now finally leads to the correct connection and track

Step 12: Welding mask application

Clean the panel and epoxy solder blocking ink will cover the panel. UV radiation is applied to the plate through the welding mask photographic film. The overlaid portion remains unhardened and will be removed. Now place the circuit board in the oven to repair the solder film.

Step 13: Surface treatment

HASL (Hot Air Solder Leveling) provides additional soldering capabilities for PCBS. RayPCB (https://raypcb.com/pcb-fabrication/) offers gold immersion and silver immersion HASL. HASL provides even pads. This results in surface finish.

Step 14: Screen printing

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PCBS are in the final stage and accept inkjet printing/writing on the surface. This is used to represent important information related to the PCB.

Step 15: Electrical test

The final stage is the electrical test of the final PCB. The automatic process verifies the PCB’s functionality to match the original design. At RayPCB, we offer flying needle testing or nail bed testing.

Step 16: Analyze

The final step is to cut the plate from the original panel. The router is used for this purpose by creating small labels along the edges of the board so that the board can be easily ejected from the panel.