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Etching Process

Comprehensive Guide to Common Chemical Etchants and Their Applications

Chemical etching is a versatile and precise manufacturing process used in various industries, such as electronics, aerospace, and automotive. It involves selectively removing material from a substrate using chemical solutions, or etchants, to create intricate and accurate designs. In this article, we will explore several commonly used etchants, their applications, and provide a step-by-step guide for setting the temperature, concentration, and other parameters when injecting an etchant into an etching machine.

Dragone Etching PCB sheet etching equipment

Commonly Used Etchants

1. Ferric Chloride (FeCl3)

Applications:

  • Printed Circuit Boards (PCBs): Ferric chloride is widely used to etch copper traces on PCBs, creating the desired circuit patterns.
  • Metal Craftsmanship: Artists and metalworkers use ferric chloride to etch intricate designs onto metal surfaces.

Setting Parameters:

  • Temperature: Typically, the operating temperature for ferric chloride etching ranges from 35°C to 45°C (95°F to 113°F).
  • Concentration: A common concentration is around 40-45% ferric chloride in water. Ensure a consistent mix for optimal results.
  • Etching Time: Etching time can vary depending on the depth and complexity of the design but is typically in the range of 5-30 minutes.
  • Agitation: Adequate agitation ensures even etching and prevents the buildup of byproducts. Use an agitating mechanism within the etching machine.

2. Nitric Acid (HNO3)

Applications:

  • Stainless Steel: Nitric acid is used to etch stainless steel, making it useful in the manufacturing of medical instruments and aerospace components.
  • Integrated Circuits (ICs): In semiconductor fabrication, nitric acid is employed to etch silicon wafers, creating microelectronic structures.

Setting Parameters:

  • Temperature: Nitric acid etching is typically performed at lower temperatures, around 20°C to 30°C (68°F to 86°F).
  • Concentration: Common concentrations range from 10-70% nitric acid, depending on the material and desired etching rate.
  • Etching Time: Etching times can be as short as a few seconds for silicon wafers to several minutes for stainless steel.
  • Safety: Nitric acid is highly corrosive and should be handled with extreme care. Always use appropriate safety equipment and a well-ventilated workspace.

3. Sodium Hydroxide (NaOH)

Applications:

  • Silicon Dioxide (SiO2): Sodium hydroxide is used in the semiconductor industry to selectively etch silicon dioxide, allowing for the creation of microstructures.
  • Glass Etching: Artists and glassmakers use sodium hydroxide for glass etching to create decorative patterns.

Setting Parameters:

  • Temperature: Typically, sodium hydroxide etching is performed at elevated temperatures, ranging from 80°C to 90°C (176°F to 194°F).
  • Concentration: Concentrations vary but are often in the range of 5-20% sodium hydroxide.
  • Etching Time: Etching times can vary from a few minutes to several hours, depending on the desired depth and precision.

Setting Parameters in an Etching Machine

To ensure the successful operation of an etching machine, it is crucial to set the parameters correctly. Let’s use the example of etching a copper PCB with ferric chloride:

  1. Temperature: Check the machine’s temperature control settings and set it to the desired range of 35°C to 45°C for ferric chloride etching.
  2. Concentration: Prepare the etchant solution by measuring the correct amount of ferric chloride and mixing it with water to achieve the desired concentration (e.g., 40-45%). Use a calibrated measurement system to ensure accuracy.
  3. Etching Time: Determine the appropriate etching time based on the complexity of your design. Start with a shorter time and gradually increase if needed. Typically, a 10-15 minute initial test run is a good starting point.
  4. Agitation: Ensure that the etching machine has an agitation system in place to keep the etchant solution well-mixed during the process. Proper agitation prevents uneven etching.
  5. Safety: Always follow safety protocols when working with chemicals. Wear appropriate personal protective equipment (PPE), such as gloves, goggles, and lab coats. Ensure that the workspace is well-ventilated and equipped with safety showers and eyewash stations.
  6. Waste Disposal: Dispose of the used etchant solution properly in accordance with local regulations. Many etchants are hazardous waste and must be treated accordingly.

In conclusion, chemical etching is a precise and versatile manufacturing process used in various industries. Understanding the properties and applications of common etchants, as well as properly setting parameters in an etching machine, is essential for achieving high-quality results while ensuring safety and environmental compliance. Whether you’re creating intricate PCBs or crafting artistic designs on metal and glass, chemical etching offers a powerful tool for precise material removal.

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Mastering the Chemistry: Hydrofluoric Acid (HF) in PCB Wet Etching

In the world of PCB manufacturing, precision and control are paramount in crafting intricate circuit patterns. One of the most potent and challenging chemical solutions utilized in the wet etching process is Hydrofluoric Acid (HF). Composed of hydrogen and fluorine, HF is a highly corrosive and hazardous acid known for its ability to dissolve various materials, including glass and metals. In this blog, we will delve into the specifics of Hydrofluoric Acid (HF) and provide valuable details on its technique for use in PCB wet etching machines, emphasizing safety and precision.

In the field of chemistry Hydrofluoric Acid belongs to which category?

Inorganic Fluxes

Inorganic fluxes are highly corrosive, and are comprised of inorganic acids and salts such as hydrochloric acid, hydrofluoric acid, stannous chloride, sodium or potassium fluoride, and zinc chloride. These fluxes are capable of removing oxide films of ferrous and nonferrous metals such as stainless steel, Kovar and nickel irons, which cannot be soldered with weaker fluxes.

Inorganic fluxes generally are used for nonelectronics applications such as the brazing of copper pipes. They are, however, sometimes used for lead-tinning applications in the electronics industry. Inorganic fluxes should not even be considered for electronics assemblies (conventional or surface mount) because of potential reliability problems. Their major disadvantage is that they leave chemically active residues than can cause corrosion and serious field failures.

Performance criteria for chemical milling


photoresists are in many ways more demanding than those of PWB fabricators; there is aplethora of different substrates such as Alloy 42,beryllium copper, iron-nickel alloys, molybdenum, tungsten, Invar, and many more. Theetching chemistries and etch conditions, which the resist must survive, are brutal. In addition to the more benign cupric chloride and the mainstream ferric chloride, you find mixtures of hydrofluoric and nitric acid which embrittle the resist, as well as very highly alkaline solutions of potassium ferrocyanide, which act like strippers on aqueous processable resists.

What is Hydrofluoric Acid (HF)?

Hydrofluoric Acid (HF) is a strong, colorless liquid acid with the chemical formula HF. Due to its reactivity and corrosiveness, HF is typically used with caution in specialized applications, such as glass etching, metal cleaning, and semiconductor manufacturing. In PCB wet etching, HF is employed to selectively remove silicon dioxide (SiO2) or glass passivation layers from semiconductor devices, enabling the creation of specific circuit patterns.

Hydrofluoric Acid

Technique of Using Hydrofluoric Acid (HF) for PCB Wet Etching:

  1. Preparing the HF Solution:

To prepare the HF etchant solution, dilute the concentrated HF with deionized water to achieve the desired concentration. The concentration of HF is typically expressed in percentage (%). Common concentrations for PCB wet etching are around 5% to 10% HF.

  1. Personal Protective Equipment (PPE):

Safety is paramount when handling HF. Always wear appropriate Personal Protective Equipment (PPE), including acid-resistant gloves, a full-face shield, chemical-resistant apron, and safety goggles to protect against splashes and inhalation of vapors.

  1. Proper Ventilation:

Always work with HF in a well-ventilated area or under a fume hood to prevent exposure to its toxic and corrosive vapors.

  1. Etching Temperature:

The etching temperature can significantly impact the etch rate and selectivity. Typically, HF etching is conducted at room temperature (around 20°C to 25°C) to ensure precision and consistency.

  1. Immersion Time:

The immersion time in the HF etchant solution determines the depth of etching. Longer immersion times result in deeper etching, while shorter times yield shallower patterns. The immersion time should be carefully controlled based on the desired circuit design and the thickness of the SiO2 or glass passivation layer.

  1. Agitation:

Gentle agitation of the etchant solution can promote an even distribution of the HF across the substrate’s surface, ensuring uniform and precise etching results.

  1. Neutralization and Disposal:

HF should not be neutralized with alkaline substances, as this can produce toxic and corrosive fluoride salts. Instead, HF should be treated with specific HF neutralizing agents. After etching, the spent HF solution should be carefully collected and disposed of according to environmental regulations.

Conclusion:

Hydrofluoric Acid (HF) is a powerful tool in PCB wet etching, enabling engineers to achieve precision and control in crafting intricate circuit patterns. By adhering to proper safety protocols and technique, HF can be handled with confidence, and PCB manufacturers can create high-quality and reliable electronic devices. Embrace the chemistry of HF, and elevate your PCB manufacturing process to new heights of accuracy and excellence.

As a wet process engineer, mastering the use of Hydrofluoric Acid (HF) in PCB wet etching empowers you to create cutting-edge electronic devices with flawless circuitry, revolutionizing the world of technology. Happy etching!

FPCB, PCB, PCB Etching solution

Unleashing the Potential of Ferric Chloride Etchant in PCB Wet Etching: A Comprehensive Guide

In the realm of printed circuit board (PCB) manufacturing, the etching process plays a pivotal role in shaping intricate circuit patterns. Among the array of etchants available, Ferric Chloride Etchant stands out as a reliable and efficient solution. Composed of ferric chloride (FeCl3), this chemical marvel offers engineers unparalleled control and precision during wet etching. In this blog, we will delve into the specifics of Ferric Chloride Etchant and provide valuable tips for its effective utilization in PCB wet etching machines.

What is Ferric Chloride Etchant?

Ferric Chloride Etchant is an acidic solution containing ferric chloride, a potent chemical compound known for its exceptional ability to dissolve copper effectively. This unique etchant is widely employed in the PCB manufacturing industry for its excellent selectivity, allowing for the precise removal of copper from the PCB substrate without adversely affecting other materials.

What Could Ideal Etch Factors Mean for SAP?

If somehow you could get both the regeneration of cupric chloride and the vertical sidewalls of powderless ferric chloride etching, I think we would see a dramatic change in the PCB industry. Currently, using the semi-additive process (SAP) is the most practical way to obtain fine features. However, if sideways etch can be efficiently inhibited in the etchants we use today (cupric chloride and alkaline cupric chloride), SAP may not even be necessary in most cases. If you are unfamiliar with SAP, it can be summarized as a process where a copper-plated panel undergoes a selective plating process to form desired features on top of the copper that was already present. Once the features are plated onto the base copper, that panel gets etched to remove the base copper, thus leaving behind only the features that were added. Finding a way around SAP would mean skipping many long and costly steps in the PCB fabrication process. Without requiring SAP to obtain fine features, PCB shops would require less plating equipment and fewer resources to perform plating (i.e., chemicals, trained personnel, time to plate, and operating space).

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The Technique of Using Ferric Chloride Etchant in PCB Wet Etching Machine:

  1. Etchant Preparation:

To prepare the Ferric Chloride Etchant solution, dissolve ferric chloride crystals in water. The recommended ratio is typically one part ferric chloride to three parts water, by weight. Always add the ferric chloride slowly to the water while stirring, and ensure you work in a well-ventilated area with proper safety equipment.

  1. Temperature Control:

Maintaining the etchant at the ideal temperature is vital for achieving consistent and accurate etching results. The recommended operating temperature for Ferric Chloride Etchant typically ranges from 35°C to 45°C (95°F to 113°F). Consider using a temperature-controlled wet etching machine to ensure precise regulation.

  1. Immersion Time:

The etching time directly influences the depth of copper removal. Longer immersion times result in deeper etching, while shorter durations yield shallower patterns. The immersion time can vary depending on the desired circuit design and the thickness of the copper layer.

  1. Agitation:

Proper agitation of the etchant solution is essential for promoting an even distribution of the etchant across the PCB surface. Adequate agitation prevents over-etching or under-etching, ensuring uniformity in the etching process.

  1. Neutralization and Disposal:

After completing the etching process, neutralize the Ferric Chloride Etchant to deactivate it and render it safe for disposal. Utilize a neutralizing agent, such as sodium bicarbonate (baking soda), to neutralize the etchant solution before disposing of it responsibly according to environmental regulations.

  1. Safety Precautions:

Ferric Chloride Etchant is corrosive and can cause skin and eye irritation. Always wear appropriate personal protective equipment (PPE), such as gloves and safety goggles, and work in a well-ventilated area to avoid exposure to fumes.

Ferric Chloride Etchant is a powerful ally in the PCB wet etching process, offering precision, control, and efficiency. By following the proper technique for its preparation and usage, engineers can create intricate circuit patterns with confidence. Embrace the potential of Ferric Chloride Etchant, and elevate your PCB manufacturing process to new heights of accuracy and excellence.

As a wet process engineer, your mastery of Ferric Chloride Etchant will undoubtedly contribute to the success of PCB manufacturing, ushering in a new era of advanced electronic devices with flawless circuitry. Happy etching!

Electronic Components, FPCB, PCB, PCB Etching solution

Mastering the Art of Cupric Chloride Etchant in PCB Wet Etching: A Step-by-Step Guide

In the realm of printed circuit board (PCB) manufacturing, Cupric Chloride Etchant stands as a powerful ally in achieving precision and control during the wet etching process. This chemical solution, composed of cupric chloride (CuCl2), enables engineers to selectively remove copper from PCB substrates, shaping intricate circuit patterns. In this blog, we will delve into the specifics of Cupric Chloride Etchant and provide valuable tips for its effective utilization in PCB wet etching machines.

What is Cupric Chloride Etchant?

Cupric Chloride Etchant is an acidic solution containing cupric chloride, a chemical compound known for its ability to dissolve copper efficiently. This etchant is widely used in the PCB manufacturing industry for its excellent selectivity, allowing for precise copper removal without adversely affecting other materials on the PCB.

Tips for Using Cupric Chloride Etchant in PCB Wet Etching Machine:

  1. Etchant Preparation:

To prepare the Cupric Chloride Etchant solution, mix cupric chloride crystals with hydrochloric acid (HCl) in a proper ratio. The common ratio is approximately 100 grams of cupric chloride per 100 milliliters of concentrated hydrochloric acid. Always add the acid to the water slowly while stirring, and ensure you’re working in a well-ventilated area with proper safety equipment.

  1. Temperature Control:

Maintaining the right temperature is crucial for achieving accurate etching results. The ideal operating temperature for Cupric Chloride Etchant typically ranges from 35°C to 50°C (95°F to 122°F). Consider using a temperature-controlled wet etching machine to ensure precise regulation.

  1. Immersion Time:

The etching time is directly related to the depth of copper removal. Longer immersion times result in deeper etching, while shorter times yield shallower patterns. The immersion time can vary depending on the desired circuit design and the thickness of the copper layer.

  1. Agitation:

Gentle agitation of the etchant solution can enhance the etching process by promoting even distribution. Proper agitation helps prevent over-etching or under-etching and ensures uniformity across the PCB surface.

  1. Neutralization and Disposal:

After the etching process, neutralize the Cupric Chloride Etchant to ensure it is deactivated and rendered safe for disposal. Utilize a neutralizing agent, such as sodium carbonate (Na2CO3), to neutralize the etchant solution before disposing of it responsibly according to environmental regulations.

  1. Safety Precautions:

Cupric Chloride Etchant is corrosive and toxic, requiring careful handling. Always wear appropriate personal protective equipment (PPE), work in a well-ventilated area, and follow proper safety protocols to avoid accidents and exposure to harmful fumes.

About Cupric and Alkaline
Together, these etchants are used in the majority of PCB etch shops, with alkaline being the most popular. To provide a baseline of how they work, their etch reactions along with their corresponding regeneration reactions, can be found in Table 1.

One of the main reasons these two etchants are the most used is because of their regeneration capabilities. With regeneration, you increase the capacity of copper you can etch. It also helps keep the etch rate at a consistent value. To maintain mass production of PCBs, it is important to keep the etch rate steady but also high enough to maximize output. Since etch rate can greatly influence production rates, it is a major factor when comparing etchants.

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Etch Factor

Another matter where alkaline etchant is highly favored is etch factor, the ratio of downward etch to sideways etch. Alkaline etchant offers the benefit of a 4-to-1 etch factor (meaning it etches downward four times as much as it etches sideways). Cupric provides a standard 3-to-1 etch factor (Figure 1).

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Alkaline etchant’s better etch factor opens the opportunity to maintain finer spaces and line widths when you are etching panels with thicker copper layers. Although alkaline can provide a great etch factor, a 4-to-1 ratio can only be obtained if the etchant is kept at its optimal condition, which is easier said than done.

Mastering the art of Cupric Chloride Etchant in PCB wet etching opens the door to unparalleled precision and control in circuit pattern creation. By adhering to proper etchant preparation, temperature regulation, immersion time, and safety precautions, engineers can craft intricate PCB designs with confidence. Embrace the power of Cupric Chloride Etchant and elevate your PCB manufacturing process to new heights of accuracy and efficiency.

In the realm of printed circuit board (PCB) manufacturing, Cupric Chloride Etchant stands as a powerful ally in achieving precision and control during the wet etching process. This chemical solution, composed of cupric chloride (CuCl2), enables engineers to selectively remove copper from PCB substrates, shaping intricate circuit patterns. In this blog, we will delve into the specifics of Cupric Chloride Etchant and provide valuable tips for its effective utilization in PCB wet etching machines.

FPCB, PCB, PCB Etching solution

Alkaline Etchant for PCB WET etching machine

As technology advances, so does our demand for smaller and more intricate electronic devices. Behind these cutting-edge gadgets lies the fascinating world of printed circuit boards (PCBs). Within PCB fabrication, the use of alkaline etchants has revolutionized the process of wet etching. In this blog, we will explore the ins and outs of alkaline etchants, uncovering the technique’s details for employing them in PCB wet etching machines.

What is Alkaline Etchant?

Alkaline etchant is a potent chemical solution utilized in the PCB manufacturing process. Composed mainly of alkaline substances such as sodium hydroxide (NaOH) or potassium hydroxide (KOH), this etchant is specially designed to selectively remove copper or other metallic materials from the PCB substrate. The purpose of this precise removal is to create specific circuit patterns and interconnections on the board.


Schematic diagrams illustrating the progressive alkaline etching process 
Image from:https://www.researchgate.net/figure/Schematic-diagrams-illustrating-the-progressive-alkaline-etching-process-a-c-and-the_fig11_346886096

The Technique of Using Alkaline Etchant for PCB Wet Etching Machine:

  1. Preparing the PCB:

Before delving into the wet etching process, it is essential to ensure that the PCB is thoroughly cleaned and dried. Any contaminants or residues must be removed to guarantee optimal etching results.

  1. Etchant Composition:

Creating the right alkaline etchant solution is crucial for the success of the wet etching process. The proper concentration of the alkaline substance and any additional additives must be meticulously calculated and mixed. These additives may include stabilizers to control etch rates or improve solution stability.

  1. Immersion in Alkaline Etchant:

Once the etchant solution is prepared, the PCB is carefully immersed in the solution. For large-scale PCB manufacturing, automated wet etching machines are employed to ensure consistent and uniform etching across the substrate.

  1. Time and Temperature Control:

The key to achieving precise circuit patterns lies in controlling the etching time and temperature. The duration of immersion and the temperature of the etchant solution must be meticulously regulated to prevent over-etching or under-etching, both of which can lead to defective PCBs.

  1. Agitation:

In some cases, gentle agitation of the etchant solution is used to enhance the etching process further. Proper agitation ensures the even distribution of the etchant across the PCB surface, leading to uniform results.

  1. Rinse and Neutralization:

After the etching process is complete, the PCB is thoroughly rinsed with water to remove any remaining etchant solution. Additionally, the PCB may undergo a neutralization step to ensure the complete deactivation of the etchant.

Alkaline etchant has proven to be a game-changer in the world of PCB wet etching. By harnessing the power of this precise chemical solution, PCB manufacturers can create intricate circuit patterns, essential for modern electronic devices. Understanding the technique of using alkaline etchant, from its preparation to its application in wet etching machines, empowers engineers to deliver high-quality, reliable, and innovative PCBs for a myriad of technological applications.

Embrace the magic of alkaline etchant and dive into the realm of endless possibilities in PCB fabrication!