While processors and software often steal the spotlight, there is often an underrated component in each electronic device- Printed Circuit Boards (PBC). As per industry reports, the global PCB market is expected to hit $86.17 million by 2026.

PCB fabrication is the process of creating the bare boards that lay the foundation for it. It is important to note that if the fabrication process is not well enough, the overall quality of the product might be affected. Therefore, in this blog, all the crucial points regarding the fabrication process including what is PCB fabrication and why it is important, will be discussed.

Key Highlights 

  • PCB fabrication is the process of transforming a circuit board design into a functional board. 
  • PCB Fabrication is required to ensure reliability, quality, and size optimization of the board.
  • The 4 crucial parts in a PCB are: Substrate, Copper Layer, Solder Mask, and Silkscreen.
  • Manufacturers must perform Laser Direct Imaging (LDI), drill the holes to deposit the copper layers, perform electroplating, and add the solder mask to prepare a board for PCB assembly.
  • The primary purpose of PCB fabrication is to create a bare PCB  while PCB assembly aims to give life to the circuit with electronic components.

What is PCB Fabrication?

PCB fabrication is the process of transforming a circuit board design into a functional board. The purpose of fabrication is simple- to create the foundational structure of the circuit board.

Unlike PCB assembly which joins the electric components to bring the circuit to life, fabrication deals with creating the board itself. It starts with the transfer of the board design layout to a special photosensitive film. Then, a patterned copper layer is created with it on the board. After a series of PCB etching and drilling processes, the unwanted copper is removed, and the remaining designed circuitry is plated with a protective layer.

Why is PCB Fabrication Important?

PCB fabrication is the foundation upon which a robust electronic device is made. Check out why the process is important:

  • Reliability and functionality

Only a well-made PCB can make sure that the connection between various electronic components flows correctly through the etched copper traces. As a result, the chances of signal interference and malfunction will be tackled. Moreover, the solder mask of the PCB protects these components from any environmental damage.

  • Improves Quality

Industries that have strict quality standards like automotive, aerospace, etc., use precise PCB fabrication to improve the performance of devices. It helps to create PCB components with extremely tight tolerances and high accuracy. Therefore, engineers can reduce material wastage and production costs. With this improved efficiency, the quality of the devices also skyrockets.

  • Better Prototyping

Prototyping is one of the most crucial phases of PCB fabrication. At this stage, designers are required to test and identify any potential issues. This way, companies can detect and solve the issues earlier, saving their valuable time.

  • Size Optimization

Nowadays, modern electric device brands are marketing lightweight and compact designs as Unique Selling Propositions (USPs). Luckily, PCB fabrication helps to minimise the size of electronic devices by laying out complex circuitry in a small and efficient manner. It is crucial for portable devices like mobile phones, tablets, laptops, etc.

Parts of PCB

PCB is composed of many components. Here are its four main parts:

  1. Substrate: Substrate is the base material of PCB and is created from fibreglass-reinforced epoxy laminate (FR-4). Its primary purpose is to give mechanical support and insulation for the copper layers.
  2. Copper Layer: The substrate is usually surrounded by some thin PCB layers of copper to pave conductive paths for electricity to flow between various components like PCB pads.
  3. Solder Mask: As the name suggests, it is a green insulating layer that masks the copper traces so that just the PCB golden fingers pads are exposed. Solder mask prevents short circuits by protecting copper from accidental contact with other metal parts.
  4. Silkscreen: Silkscreen is a white layer on top of the solder mask. It is mainly used to write letters and symbols for the identification of the PCB components like the PCB stencil.

PCB Fabrication Process Steps

Several steps are involved in the process of transformation of a circuit board design into a physical structure. Here's a detailed explanation of each step:

1. Laser Direct Imaging

First of all, Laser Direct Imaging (LDI) is used to create the circuitry pattern on the photoresist layer of the PCB. Check out the four main steps involved in the LDI process:

i) A light-sensitive and photoresist layer is applied to the copper-clad board.

ii)The board is subjected to a laser beam using a laser imaging machine. Then, certain parts of the board will be exposed in the shape of the PCB pattern.

iii)Unexposed parts of the PCB will be removed using a chemical solution.

iv)The exposed parts will be hardened through a developing process.

2. Strengthen the Bonds

Once the layers are etched, a chemical treatment called oxide is done to strengthen the bond between multilayer PCBs. A thin layer of uncured prepreg is applied to each layer, after cleaning. Then, a hydraulic press applies pressure to activate the prepreg adhesive. As a result, the prepreg resin melts and the layers are bonded.

3. Drill the Holes

The next step is to create precise holes to facilitate connection between various layers. The type of drilling varies with the type of visa being fabricated. However, usually, a CNC-controlled drilling machine is used for the purpose.

Different drill bits are used depending on hole size and required plating depth. Debris from drilling is removed through a cleaning process.

4. Deposit Copper Elements

Now, it's time to plate the drilled holes with copper. This is done to create a conductive path for electric signals to pass through various layers. For copper deposition, the PCB panel must be placed in an electroless plating bath containing a copper solution. As a result of a chemical reaction, thin layers of copper will be deposited on all exposed conductive surfaces.

5. Electroplating

Next, electroplating is done to thicken the copper traces and increase the conductivity. Here is a short brief of the process:

i) The PCB panel is placed in an electroplating tank containing a copper sulphate solution and anodes.

ii)An electrical current is applied to the surface.

iii)Soon the exposed surfaces attract copper ions from the solution.

Remember, success depends upon the controlling of the electroplating process.

6. Add Solder Mask

As an extra protection layer, a green solder mask coat is applied to the PBC board. The solder mask is patterned using an imaging process similar to LDI and the exposed solder mask is treated with UV light. 

7. Assembly Preparation

At last, the board is cleaned to remove any contaminants. Then, it is silk screened with a logo and markings. It is then inspected for any defects before moving on to the assembly stage for components like enig PCB and taconic PCB.

Difference Between PCB Fabrication and PCB Assembly Process

The terms PCB fabrication and PCB assembly are often used interchangeably without knowing the core differences between them. Here's a breakdown of the key differences between the both:

1. Objective

The primary purpose of PCB fabrication is to create a bare PCB with conductive pathways and insulative layers. However, PCB assembly aims to give life to the circuit with electronic components like resistors, capacitors, integrated circuits, etc.

2. Processes

PCB Fabrication involves subtractive processes for removing unwanted material. Moreover, some chemical treatments like electroplating are used to deposit copper layers on the surface. But PCB assembly focuses on adding components and soldering connections.

3. Tools

PCB Fabrication requires specialised equipment like film printers, etching machines, plating lines, testers, etc. PCB assembly uses comparatively more simple tools like automated pick-and-place machines, reflow ovens, and wash systems.

4. Role in production

PCB fabrication has the primary role in the production of electronic devices as it lays the foundation by creating the bare PCB. PCB assembly focuses on making it functional.

How to Implement the PCB Fabrication Process?

Setting up and managing an in-house PCB fabrication process is not a simple walk-over process. There are many significant challenges like high investment, specialised equipment, skilled workers, etc. On top of that, you need to consider the safety considerations first of all. Check out some tips to implement the PCB fabrication process successfully.

  • Prioritise acquiring high-quality equipment suited for the types of PCBs you intend to fabricate. Avoid adjusting with cheap tools!
  • Recruit the right talents, preferably with experience in fabrication processes. If not, allocate the necessary time and resources for their training.
  • Conduct inspections at each stage of fabrication to identify and rectify any issues in advance.
  • Consider collaborating with an established PCB manufacturer for complex projects.

Conclusion

 In a nutshell, PCB fabrication sets out the base for an electrical device. So, make sure that the foundation is laid out in the best possible manner with proper techniques and safety standards.

The right tools and knowledge will be useful only if there is a right team on the side. Lion Circuits is a high-quality PCB manufacturing and assembling service provider to guide companies hassle-free through the process. Contact us now!