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PCB Etching: Definition, Types & Process

How to Etch a PCB Board?

Table of Contents

PCB etching is like an artistic dance that transforms a blank copper-clad canvas into a masterpiece of circuitry. It’s a process that marries science and craftsmanship, allowing you to bring your electronic designs to life with flair and finesse. Imagine having the power to shape copper with precision, carving intricate pathways that guide the flow of electrons and breathe life into your electronic creations. Get ready to etch your way to electronic greatness, let the etching begin!

What is PCB Etching?

An introduction to etching

In essence, etching can be seen as a controlled erosion or dissolution of material, where specific areas are selectively removed to create a desired pattern or design. Whether it’s etching on glass, metal, or other materials, the principle remains the same — selectively removing material to achieve a desired visual or functional outcome.

Originally used to make printing embossing plates, it is now also widely used in processing lightweight instrument panels, nameplates and thin workpieces. With the development of process equipment, etching technology has also been applied to semiconductor manufacturing and other fields.

A panel is etched with images of lovers embracing each other.

An introduction to PCB etching

PCB etching is a critical step in the PCB manufacturing, where unwanted copper is removed from a substrate to create the desired circuit patterns for electronic components. This process involves applying a protective mask to outline the circuitry, then submerging the PCB in an etching solution that dissolves the exposed copper. This is one of the etching methods. We will introduce several types of PCB etching methods so that you can understand them deeper. The result is a precise pattern of copper tracks that form the electrical connections necessary for the PCB’s function.

A comparison picture of PCB before etching and after etching

Which stage does PCB etching belong to?

PCB etching is part of the PCB manufacturing stage. This occurs before components are assembled onto the board, which would be the PCB Assembly stage. The etching process is crucial for defining the pathways that will form the electrical connections necessary for the PCB’s operation. Once the PCB is etched and other finishing processes are completed, it moves on to the assembly stage where components are soldered onto the board to create a functional PCBA.

Types of PCB Etching

In PCB manufacturing, there are many types of PCB etching. At ELE, we understand that your PCB designs deserve the utmost care and attention. We believe ourselves to be a leading provider of PCB and PCBA services, delivering exceptional quality and unmatched precision to meet your exact requirements, contact us at info@elepcb.com. We continue to share more knowledge about the types of PCB etching.

Chemical Etching

Chemical etching, also know as wet etching, is the most widely used method for PCB etching. It involves the use of chemical solutions, typically ferric chloride (FeCl3) or ammonium persulfate (NH4)2S2O8, to selectively remove the unwanted copper from the PCB. The etchant reacts with the exposed copper, dissolving it and leaving behind the desired circuit patterns. Chemical etching offers precise control over the etching process and is suitable for producing intricate and fine circuitry. The wet PCB etching is further broken down into two types:

Alkaline Etching

Alkaline etching, also known as alkaline permanganate etching, utilizes an alkaline solution, typically a mixture of sodium hydroxide (NaOH) and potassium permanganate (KMnO4). The alkaline etchant selectively removes the unwanted copper from the PCB surface, leaving behind the desired circuit patterns. Alkaline etching is known for its ability to provide good etching uniformity and high etching rates. It is often used for PCBs with relatively simple and larger feature sizes.

Alkaline etching line

Acidic Etching

Acidic etching involves the use of an acidic solution, typically a mixture of hydrochloric acid (HCl) and hydrogen peroxide (H2O2), to selectively remove the unwanted copper from the PCB surface. Acidic etching offers precise control over the etching process and is suitable for producing intricate and fine circuitry. It is commonly used for high-density PCBs with smaller feature sizes, as it allows for better etching resolution and finer line widths.

Plasma Etching

Plasma etching, also known as dry etching or plasma etchback, is a more advanced and specialized etching technique. It utilizes a low-pressure plasma chamber to remove the unwanted copper from the PCB surface. In plasma etching, reactive gases such as oxygen (O2) or chlorine (Cl2) are introduced into the chamber, and the plasma generated breaks down the copper molecules, resulting in their removal. Plasma etching is particularly useful for high-density PCBs with smaller feature sizes. It allows for better control over etching profiles and is often used for fine-line circuitry and microelectronics applications.

Laser Etching

Laser etching, also known as laser ablation or laser direct imaging (LDI), utilizes a high-powered laser beam to selectively remove the unwanted copper from the PCB surface. The laser beam is precisely controlled and directed towards specific areas of the PCB, vaporizing or ablating the copper material. Key features and benefits of laser etching in PCB manufacturing include:

  • Precision: Laser etching offers high precision and accuracy, allowing for the creation of fine feature sizes and intricate circuit patterns. It enables the production of high-density interconnect (HDI) PCBs and microelectronics with tight tolerances and precise geometries.
  • Versatility: Laser etching is compatible with various PCB materials, including rigid PCBs, flexible PCBs, and rigid-flex PCBs. It can be used for single-sided, double-sided, and multilayer PCBs, making it a versatile solution for different types of PCB designs.
  • Non-Contact Process: Laser etching is a non-contact process, meaning the laser beam does not physically touch the PCB surface. This eliminates the risk of mechanical damage to delicate components or substrates. It is particularly beneficial for sensitive electronic devices or fine-pitch components.
  • High Resolution: Laser etching provides excellent resolution, allowing for the creation of complex and detailed circuit patterns. It can achieve fine line widths, small vias, and intricate shapes with high accuracy.
  • Rapid Prototyping: Laser etching is well-suited for rapid prototyping and quick turnaround times. It offers flexibility in making design iterations and modifications without the need for costly and time-consuming tooling changes.
  • Minimal Material Wastage: Laser etching is a subtractive process, selectively removing only the desired material. This results in minimal material wastage, making it a cost-effective and environmentally friendly etching method.
  • Direct Imaging: Laser etching is commonly used in direct imaging processes, where the laser beam directly exposes the PCB surface without the need for photomasks. This eliminates the need for costly and time-consuming photolithography processes, improving efficiency and reducing manufacturing steps.

It’s important to note that laser etching requires specialized equipment, including laser systems with appropriate wavelength and power settings. The laser parameters, such as power, speed, and focus, can be adjusted to achieve the desired etching results based on the specific PCB design requirements.

laser etching

The Etching Process

The etching process in PCB manufacturing is a critical step that involves removing unwanted copper from the board to create the desired circuit patterns. Here’s a detailed and professional overview of the PCB etching process:

Step 1: Preparation

The PCB material, typically a copper-clad laminate, is thoroughly cleaned to remove any contaminants such as oils or dirt that could interfere with the etching process. This ensures that the photoresist adheres properly and that the etching solution works effectively.

Step 2: Applying Photoresist

A light-sensitive photoresist layer is applied to the entire surface of the PCB. This can be done through various methods, including lamination or spraying. The photoresist will protect the copper that needs to remain after the etching process.

Step 3: Exposure

The PCB is exposed to ultraviolet light. A photomask with the desired circuit pattern is placed over the photoresist-coated board. The areas of photoresist exposed to UV light will harden, while the unexposed areas will remain soft and can be washed away in the developing stage.

Step 4: Developing

The board is then developed in a chemical solution that removes the unhardened photoresist. This step reveals the copper areas that will be etched away, leaving behind the hardened photoresist in the pattern of the desired circuitry.

Step 5: Etching

The PCB is submerged in an etching solution that dissolves the exposed copper. Common etching solutions include ferric chloride, ammonium persulfate, or a mixture of hydrochloric acid and hydrogen peroxide. The etching solution must be agitated to ensure even removal of copper.

Step 6: Stripping

After etching, the remaining photoresist is stripped off, exposing the copper circuit that was protected underneath. This can be done using a photoresist stripper solution.

Step 7: Inspection and Testing

The etched PCB is inspected for any defects, such as under-etching or over-etching. Electrical testing is also conducted to ensure the circuit’s functionality.

Step 8: Finishing

Additional finishing steps may include applying a solder mask, surface finish, and silkscreen for labeling component locations. These steps provide additional protection to the copper circuits and ensure solderability during component assembly.

This process requires precise control and monitoring to achieve the high level of detail and reliability needed for professional PCBs, especially in high-tech applications like aerospace or medical devices. The choice of etching solution and the control of the etching rate are crucial to the quality of the final product.

We want to tell you a little secret. After introducing the specific steps of PCB etching, you will find that you can actually DIY your own PCB by yourself. Get started and send us your experience of etching PCB boards via email.

Conclusion

PCB etching is an important process in manufacturing circuit boards. It involves the removal of unwanted copper to create a desired circuit pattern. Safety precautions and quality control are essential throughout the etching process to ensure accurate results and avoid damage. ElEPCB offers a convenient solution for etching PCBs, providing customization options and efficient service. You can contact us and request a quote based on your requirements.

Keywords: PCB Etching, PCB Etching Process

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About Michael

Michael is the general manager of ELEPCB, a leading PCB design and manufacturing company based in China. He has over 10 years of experience in the PCB industry, and has been involved in various projects.

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