From Design to Electrical: A Detailed Guide to the PCB Manufacturing Process

November 16, 2023
From design to electrical: A detailed guide to the PCB manufacturing process
PCB

Printed circuit board (PCB) manufacturing is developing and creating custom-designed circuit boards used in electronic devices. PCBs are crucial in most modern electronics, from smartphones to household appliances to automotive systems. They provide the physical structure and the electrical connections for various components like resistors, capacitors, microchips, and connectors.

The PCB manufacturing process consists of a series of complex procedures that, when combined, ensure the finished product's performance.

PCBs can vary quite a bit in design depending on the type of electronic device they are intended for use in and can be single, double, or multilayered, but the fabrication processes that a PCB must undergo remain the same for all PCB types in the beginning and only differs after the first layer’s production.

More complex PCBs require the completion of more steps during the manufacturing process, and some particularly complex PCBs may even require 20 or more steps before being fully completed. None of these steps must be skipped throughout the procedure, as doing so could seriously impact a PCB’s performance.

What are the main steps involved in the PCB manufacturing process?

Manufacturing even the most basic PCBs requires a complex process with many steps. Many of these steps need machine-driven tools and computer guidance to guarantee accuracy, prevent short circuits or incomplete circuits, and assure that the PCB will perform as intended.

The following are some of the most critical steps that are included in this manufacturing process:

Step 1: Design and Output

Before anything else can be done, developing the PCB’s design is essential. It uses PCB design software like Altium Designer, OrCAD, or Pads. Once the design is approved, it is exported into a format supported by the manufacturer using a Gerber program. This software uses algorithms to oversee every design detail to check for potential errors.

Step 2: Printing the Design

Once the PCB manufacturer receives the schematic files and conducts a design for manufacture (DFM) check, they print the circuit board using a laser plotter printer that makes highly detailed photo films.

It provides the manufacturer with a plastic sheet with a photo negative of the PCB, on which black ink represents the PCB’s conductive copper parts. The transparent part is the non-conductive material for the inner layers. The opposite is true for the outer layers, with clear representing copper and black representing the area etched away.

Each layer of PCB and solder mask receives its film sheet, and to ensure perfect alignment between them, registration holes are punched through them.

Step 3: Printing the Inner Layers

After being printed onto a piece of laminate, a copper foil layer is applied to the PCB design and pre-bonded to the laminate to serve as the PCB’s structure before being etched away to reveal the blueprint.

The panel is covered with a layer of photoreactive chemicals that harden when exposed to UV light, called the resist.

When the UV light passes through the translucent parts of the film and hardens the resist, it indicates the locations of copper that are to be kept as pathways, while the black ink prevents hardening from occurring in areas that are removed later on.

The board is then washed with an alkaline solution to remove leftover resist, pressure washed, and left to dry.

Step 4: Removing Unwanted Copper

Next, a copper solvent solution bath removes the exposed excess copper. Once that excess copper is removed, another solvent must wash off the hardened resist that protects the preferred copper.

Step 5: Layer Alignment

Once clean, the PCB’s layers must receive alignment punches to ensure that they line up correctly, so they are placed into a machine called the optical punch that does this. Following the alignment, another machine checks for defects through an automated visual inspection that compares the panels to the original Gerber design.

Step 6: Layer-up and Bond

Next, the layers must be fused, and the outer layers must join with the substrate. The outer layer consists of sheets of fibreglass pre-impregnated with epoxy resin.

The original substrate containing the copper trace etchings is covered on its top and bottom with a thin copper foil. The layers are fit securely into pins attached to a heavy steel table.

First, a prepreg layer is placed over the alignment basin, followed by the substrate layer, the copper sheet, further sheets of prepreg, and an aluminum foil and copper press plate.

A bonding press computer heats this stack, applies pressure to specific points, and then allows it to cool at a controlled rate. After that, the restraining pins are removed, and the top pressure plate is discarded.

Step 7: Drilling

Exact holes are drilled into the stack board using an X-ray locator to ensure accuracy and a computer-powered drill with air-driven spindles that turn at 150,000 rpm. Once the drilling is complete, a profiling tool removes any additional copper that lines the edges of the production panel.

Step 8: Plating

A chemical is used to fuse all of the PCB’s layers, and then it is cleaned and bathed in a series of chemicals, which, in part, coats the panel in a very thin copper layer to cover the walls of the previously drilled holes.

Step 9: Outer Layer Imaging

Another resist layer must be applied to the outer layer to be imaged with the PCB design. Then, the outer layers are plated using the same method used on the inner layers in the previous step. However, the outer layers get a tin plating to help guard this layer’s copper.

Step 10: Outer Layer Etching

Any unwanted copper is removed from the outer layer using the same solvent from earlier. The remaining resist coating is removed during this step.

Then, another automated optical inspection takes place to ensure the outer layer meets the exact requirements of the design and to verify that all excess copper has been removed.

Step 11: Solder Mask Application

After being thoroughly cleaned, the surface of each panel is covered with an ink epoxy and solder mask film. UV light indicates which parts of the solder mask need to be removed, and after they are, the rest of the mask is cured in an oven.

Step 12: Silkscreen and Surface Finish Application

Next, it is necessary to print vital information, such as company ID numbers, warning labels, manufacturer marks or logos, part numbers, and pin locators, on the surface of the PCB with an inkjet printer. Then, the surface of the PCB is chemically plated with gold or silver.

Step 13: Electrical Testing

As a last precaution, multiple electrical tests are performed on the PCB to assess its functionality and conformity to the original design.

Step 14: Profiling and V-Scoring

The final step involves cutting different boards from the original panel using a router or a v-groove. First, the engineer must program where the cuts/scores are made, and then the machine does the rest.

How Circuits Central Can Satisfy Your PCB Manufacturing Needs

The PCB manufacturing process can be challenging to handle independently without the right amount of experience. Still, fortunately, Circuits Central can help take care of all of your PCB manufacturing needs.

Our team of PCB experts has a significant wealth of experience in PCB design, PCB prototyping, PCB Assembly, and post-manufacturing testing and development. With our knowledge, experience, and reliable production facility, we can handle the development and production of even the most complex PCBs.

For more information about our approach to the PCB manufacturing process or to learn more about our other PCB assembly and manufacturing services, call Circuits Central at 1 (888) 602-7264 or email us at info@circuits-central.com.

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