PCB Design

The Complete Guide to PCB Design and Fabrication for Beginners

PCB Fabrication

Almost all the electronic devices that we see in the world have printed circuit boards involved, such as smartphones, computers, tablets, televisions, smart home production, medical electronics, industrial devices, and even aerospace equipment. These small and usually green boards work as the brains of any electronic products, helping them to achieve the functions people desire to get.

As PCBs are so important in the electronic industry, it makes sense we know more about them. Such as How are these PCBs designed and produced? However, only a few people know about the whole process of PCB design and fabrication.

There are many rigorous steps when it comes to designing or fabricating a PCB to achieve a functional final product. In this article, we will talk about the complete process of PCB design and production in a simple, as a guide to beginners in the electronics and PCB industry.

PCB Design and Fabrication

PCB Design and Fabrication

Designing a PCB – The Full Guide

Designing a printed circuit board has different steps involved and we will break it all down for you.

Electrical Parameters Understanding

Do you know what is extremely important or imperative for PCB design? It is the understanding of electrical parameters. Consider factors like current limits, voltage specifications, signal types, capacitance restrictions, impedance characteristics, shielding, and available circuit parts.

This knowledge guides the design process, ensuring the printed circuit board meets performance requirements.

Crafting the Schematic

A schematic is a blueprint that displays the electrical details that describe how a board operates and what it was intended to accomplish. It is an indispensable tool for PCB designers.

The expressions and connections on this schematic serve as the electrical landscape of the board’s architectural framework.

It contains the essence of how the PCB will operate and coexist with the rest of the system. Specifically, at this early stage, the schematic cannot assume its mechanical form and only exists on the electronics plane.

This is only a conceptual roadmap, setting the stage for later phases where the printed circuit board will seamlessly transition from electrical abstraction to its physical components.

Create PCB Using Schematic Capture Tool

PCB design engineer makes use of a software platform in collaboration with the principal engineers so he can illustrate the functionality of the board along with the location of the components.

After that, it is the work of the mechanical engineer to integrate the design to see if it is suitable or appropriate for the intended device.

PCB Stackup Design

PCB stackup is the one thing that is critical for board thickness, especially if there is impedance. It is important because it affects the speed and integrity of the electrical signal. Consider the possibility of the right PCB stack up as early as possible. For high-layer and high-density circuit boards with blind and buried Vias, stack up design is very difficult.

Define Design Rules

PCB design is all about the IPC and industry standards. For this reason, it is important to define the design requirements and rules that are in accordance with the standards.

In this scenario, it is important to collaborate with a PCB layout provider because they are knowledgeable about IPC standards. This will help you save money and time on revisions and manufacturing delays.

Component Placement Arrangement

Usually, the customer and PCB supplier arrange components in accordance with design and layout specifications. However, it is important to note that in certain cases component placement may need to be restricted because there is the possibility of electrical noise generation.

The PCB supplier offers data sheets for approval by the client that need to be followed.

Drill Holes Incorporation

Based on components and connections, drill holes are added. Since most circuit boards have two sides, connections must be made to holes drilled from the top to the bottom layers.

Trace Routing

When it comes to trace routing a lot of consideration goes around. It is basically the process of joining points along the path after successful component placement and drill holes.

Identifiers and Labels Addition

After the trace routing the following step is all about including labels and identifiers. This phase is about adding reference designators, markings, identifiers and labels

On the board, components are identified by designations.

Generate Gerber Files For PCB Manufacturer

When these design files are completed, we need to check if all these files are free of error. After verification, we need to generate all the data needed to create a printed circuit board for a PCB manufacturer. The most widely used format is Gerber files with BOM. These are prepared for PCB fabrication and assembly. The step is very important for a perfect PCB design and fabrication.

PCB Fabrication

PCB Fabrication

PCB Fabrication: The Basic Steps

When it comes to PCB fabrication, it is all about converting the circuit board design into a tangible structure and achieving the functions of the electronic products. This process is performed by a PCB manufacturer.

This arduous process involves a number of steps toward the physical transformation. The copper layout is first imprinted onto copper-clad laminates using imaging, and then the excess copper from the inner layers needs to be etched away in order to expose traces and pads. Next, PCB board materials and copper sheets are heated and laminated to form the layer stack up. Drill holes for mounting, through-hole pins and vias, then follow. The next steps are to trim off excess copper from the top and bottom layers, plate via holes and traces in order to be sure they are durable, and apply a protective coating or solder mask or mental surface finish. Reference indicators, polarity details, logos or any other markings are added by silkscreen printing. Copper pad areas on the surface can be optionally treated as surface finishes. And lastly, testing and inspection.

This thorough process of PCB design and fabrication turns a circuit board design into a physical functional structure. But PCB fabrication is a very complicated task. Besides, different types of PCBs have different production processes. Here, we take the basic multilayer printed circuit board production process as an example and talk about the detailed process of printed circuit board fabrication.

Out Layer Copper Trace Formation

The PCB-fabrication process begins with Laser Direct Imaging (LDI) and the Develop/Etch/Strip procedure. A copper laminate is provided with a dry film, and LDI exposes specific areas in the PCB pattern. The film remains an etch barrier after the unexposed areas are removed through washing.

In order to create the copper circuitry, the remaining film acts as an etch barrier to remove the exposed copper. Subsequently, issues like shorts and opens could be fixed with an optical inspection of the layers for flaws prior to lamination. The bond strength of the inner layer of the PCB is further strengthened by an oxide chemical treatment that follows etching.

Brown Oxide and Lamination

After applying the oxide, the laminating procedure takes place, where heat and a hydraulic press are used to press interleaving layers of prepreg and copper foil into a single unit. This fiberglass material, coated with epoxy resin and referred to as a prepreg, melts under the heat and pressure of the lamination process to fuse the layers together.

During this stage, strict alignment maintenance guarantees that the circuitry between layers is intact. An intricate process involving chemical and precision treatments results in a multilayered printed circuit board that is prepared for electronic components.

Drilling and Via Plating

Multi-layer PCBs are interconnected through the use of vias. A stack of 2-3 panels is used in the drilling process, which is tailored to the type of visa. To increase the efficiency of signal transmission, these holes are plated with copper using electroless copper deposition after drilling, and then plated thicker copper to get robust via copper wall.

After drilling, the excess resin and debris are completely removed through cleaning. Later, fine copper is deposited on exposed panel parts to provide the basis for electroplating.

Metal Deposition and Etching

After applying a dry film coating and performing a laser direct image, a conductive circuit is created on the exterior surfaces.

After being powered by a current and submerged in a copper plating bath, the conductive surface of this PCB is covered in copper. Tin plating applied later on acts as an etch barrier. Following plating, the tin-uncovered copper is etched away, and the dry film is peeled off. It leaves behind unfinished traces, pads, and patterns.

Solder Mask, Silkscreen and Surface Finishes

The PCB is protected prior to assembly by solder masking with UV exposure. It helps keep solder bridges and copper traces from oxidizing. It is typically green. Although you can choose any color for your solder mask, green makes it easier to see flaws.

Markings and component reference marks are applied via silkscreening, and the ink is baked to cure it.

The surface finish of metal surfaces that are exposed to the elements is protected by soldering during the assembly process. The most common ones are HAL, OSP, and ENIG.

Testing and Inspection

By now you must have an idea that the finished printed circuit board goes through a lot of things including the rigorous testing process. This process is important to guarantee that the complete procedure has been followed.

E-testing for open and short circuits is the most critical test. Also, AOI inspections and visual inspections are done to detect any defects.

Conclusion

PCB design and fabrication can be tough since many steps are involved. But it is so important because the entire electronic product is dependent on it. The good course of action is to always take the help of a skilled PCB designer and PCB manufacturer so things are pitch perfect for a fully functional electronic device.

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