Modern electronics heavily relies on precisely manufactured printed circuit boards (PCBs). To create the required layout of conductive tracks, the PCB must undergo etching — a process that removes excess copper from the laminate surface. One of the most commonly used etching agents in this process is sodium persulfate (e.g., marked as B327). In this article, we’ll explain what sodium persulfate is, how it works, and why it’s an effective solution for etching PCBs.
What is PCB Etching?
PCB etching is a critical step in the production of printed circuit boards. It involves removing unwanted layers of copper from the laminate surface.
Etching removes the excess copper from areas not protected by a resist (e.g., photoresist lacquer), revealing the desired conductive paths that form the electrical circuit.
Etching directly affects the final appearance and quality of the PCB and ensures accurate electrical connections. It is usually performed in automated production lines at professional facilities, minimizing the risk of human error.
How Does the PCB Etching Process Work?
There are two main methods for etching: mechanical and chemical. This article focuses on the chemical method, which is common in small-scale production and workshops. It requires chemicals capable of controlled copper dissolution. The most popular ones include:
Ferric chloride (FeCl₃)
Sodium persulfate (Na₂S₂O₈)
Acid and oxidizer mixtures
More and more PCB manufacturers prefer sodium persulfate over ferric chloride, as FeCl₃ can behave unpredictably. B327 is also favored by hobbyists and beginners due to its availability, affordability, effectiveness, and safety.
Sodium Persulfate – Key Information
Sodium persulfate is an essential inorganic compound from the persulfate group used for PCB etching. At room temperature, it appears as a white, fine, hygroscopic powder.
Key Properties of Sodium Persulfate
Sodium persulfate is a powerful oxidizer. It dissolves easily in water and prevents crystallization from the solution. It ensures fast and uniform etching, resulting in sharp track edges and reduced undercutting.
It’s safe to use, with one important precaution — it must be stored away from flammable materials.
Do not store sodium persulfate or its solution in airtight containers. Decomposition may release gases (such as oxygen), which can increase pressure and damage the container. Always store in a dry, shaded place.
What Does B327 Stand For?
In electronics, commercial sodium persulfate often appears under the label B327, indicating it’s ready-to-use for PCB etching — exactly the kind of product we offer.
B327 sodium persulfate is a purified, ready-to-use version of Na₂S₂O₈, different from raw sodium persulfate. The differences, while subtle, are important:
B327 is based on pure Na₂S₂O₈
It’s specifically formulated for PCB use, meeting purity and safety standards
It is chemically pure, free of contaminants like chlorides, chlorates, manganese, iron, heavy metals, and ammonia
The powder has a long shelf life (up to 3 years if stored properly)
Comes with detailed dosing and safety instructions
On the technical chemical market, you may find various sodium persulfate products — but choosing B327 ensures quality and reliability.
At AG TermoPasty, we provide full transparency of B327’s specifications — you’re welcome to review its technical and safety data sheets.
How Does B327 Sodium Persulfate Work as a PCB Etchant?
PCB etching removes excess copper from the laminate surface. B327 is simple to use — just mix the powder with the appropriate amount of water to prepare the etching solution.
Its strong oxidizing properties are its key strength. During etching, copper (Cu) is oxidized into Cu²⁺ ions, which dissolve into the solution:
Cu + S₂O₈²⁻ → Cu²⁺ + 2 SO₄²⁻
In water, sodium persulfate decomposes into sulfate radicals (SO₄•⁻), powerful oxidizers that dissolve metallic copper via oxidation.
Etching Conditions with B327 Sodium Persulfate
Proper etching requires the solution to reach a temperature of about 50°C and remain between 40–50°C. Elevated temperatures significantly accelerate the process.
A typical etching solution contains 200 g of powder per 1 liter of water (20%), though this ratio can be adjusted. The etching time depends on copper thickness and temperature, usually ranging from a few to several minutes. Continuous monitoring is essential. The transparent solution makes it easy to see when the copper is fully etched.
Ensure constant agitation during etching — use a magnetic stirrer or gently move the container. This speeds up the process and ensures uniform results. Dispose of the used solution according to environmental and safety regulations.
B327 Sodium Persulfate vs. Ferric Chloride: Advantages
While ferric chloride is still widely used, sodium persulfate is becoming more popular due to several advantages:
It doesn’t leave brown stains or permanent discoloration on the board
It provides better process control and cleaner, sharper track edges
It offers clear visibility during etching — unlike murky FeCl₃ solutions
It poses a lower risk of corroding all the PCB components
Sodium persulfate is an excellent alternative to ferric chloride, offering comparable results with greater control and cleaner outcomes.
Applications of B327 Beyond PCB Etching
B327 sodium persulfate is commonly used in technical and medical university labs.
In electronics, it’s ideal for etching various types of PCBs and copper. It can also replace ammonium persulfate for gentler etching or be used in zinc etching solutions.
In metalworking, it plays a role in recovering precious metals by oxidizing them into ionic form for precipitation or separation.
Its applications go beyond electronics and analytical chemistry — it’s also found in the paper, cosmetics, and cleaning industries:
In cosmetics: used in hair dyes, bleaching agents, and exfoliants
In cleaning products: a component of dry bleaches and activators in whitening products
It’s a top choice for technical and medical labs and a go-to etchant for hobbyists and DIY projects.
Summary
Sodium persulfate B327 is an effective, clean, and safe etchant for PCBs. Thanks to its strong oxidizing properties, it precisely removes excess copper, ensuring high-quality conductive tracks. It’s widely used in both professional electronics and hobby projects.
Get in touch with us if you’d like to learn more about B327 sodium persulfate or need expert advice on electronics maintenance!