what is chemical milling

Chemical milling, also known as chemical machining or chem-milling, is a manufacturing process used to selectively remove material from the surface of a workpiece using chemical reactions. This process is typically used to shape and finish metal parts and is particularly useful for producing complex and intricate shapes that are difficult or costly to achieve using traditional mechanical machining methods like milling, turning, or grinding.

Here’s how chemical milling generally works:

• Masking: A protective mask or resist material is applied to the surface of the workpiece. This mask is typically made of materials that are resistant to the chemical etchant used in the process. The mask is precisely designed to expose only the areas of the workpiece that need to be chemically milled, leaving the rest of the surface protected.
• Etching: The workpiece, with the mask in place, is immersed in a chemical etchant bath. The etchant is a corrosive solution that reacts with the exposed metal surfaces but does not affect the masked areas. The etchant removes material from the exposed areas by dissolving it through chemical reactions.
• Rinse and Finish: After a predetermined amount of time, the workpiece is removed from the etchant bath and thoroughly rinsed to stop the chemical reaction. The mask is then removed, revealing the finished part. Additional finishing processes such as cleaning, deburring, or surface treatment may be necessary to achieve the desired final product.

Chemical milling offers several advantages, including the ability to produce parts with high precision, intricate geometries, and fine details. It is often used in aerospace and automotive industries to manufacture components like aircraft engine blades, turbine disks, and intricate parts for fuel systems.

how chemical milling works

Chemical milling, also known as chemical machining or chem-milling, is a subtractive manufacturing process used to selectively remove material from the surface of a workpiece through chemical reactions. The process typically involves the following steps:

1. Masking: A protective mask or resist material is applied to the surface of the workpiece. This mask is designed to cover and protect the areas of the workpiece where material should not be removed during the chemical milling process. The mask is often made of materials that are resistant to the chemical etchant used in the process.
2. Exposure: The masked workpiece is exposed to a chemical etchant. The etchant is a corrosive solution or chemical mixture that reacts with and dissolves the exposed metal surfaces of the workpiece. The specific etchant used depends on the material being processed and the desired rate of material removal.
3. Etching: As the workpiece is immersed in the etchant, the chemical reactions between the etchant and the exposed metal surfaces result in the removal of material. The etching process selectively removes material from the exposed areas while leaving the masked areas unaffected. The rate of material removal can be controlled by factors such as the concentration of the etchant, the temperature of the etchant bath, and the immersion time.
4. Rinse and Neutralization: After a predetermined amount of time or when the desired depth of material removal is achieved, the workpiece is removed from the etchant bath. It is then thoroughly rinsed to stop the chemical reaction. Rinsing helps remove any residual etchant and prevent further material removal. In some cases, a neutralization step may be required to neutralize any remaining acidic or alkaline residues.
5. Mask Removal: The protective mask or resist material is removed from the workpiece, revealing the final part with the desired shape and features.
6. Post-processing: Depending on the application and the final part requirements, additional post-processing steps such as cleaning, deburring, and surface finishing may be performed to achieve the desired surface quality and tolerances.

Chemical Milling Equipment

The equipment used in the production of high-precision metals and the details of how each piece of equipment works in the production of high-precision metals. Click to learn more.

Metals capable of being chemically milled

• Aluminum
• Beryllium Copper
• Brass
• Bronze
• Copper
• Copper-Nickel
• Elgiloy
• Havar
• Inconel
• Invar
• Kovar
• Metglas
• Molybdenum
• Monel
• Mu-Metal
• Nickel
• Nickel silver
• Nickel-iron
• Phosphor bronze
• Spring steel
• Stainless Steel
• Steel
• Titanium
• Tungsten
• Tungsten-Copper (W-Cu)

Wet film etching is another key technique in the precision metal etching process, offering an alternative approach to achieving fine patterns and features on thin metal substrates.

1. Substrate Preparation:

• Just like in dry film etching, the process begins with a clean metal substrate. The substrate is typically cleaned to remove any contaminants, ensuring proper adhesion of the photoresist layer.

2. Application of Photoresist:

• Instead of dry film resist, wet film etching utilizes a liquid photoresist. The photoresist is applied to the metal substrate by various methods such as spin coating, dip coating, or spray coating. It forms a thin, uniform layer over the entire surface.

3. Soft Baking:

• After the photoresist is applied, it undergoes a soft baking process. This step involves heating the substrate to remove solvent and to ensure the photoresist adheres well to the metal surface.

4. Exposure to UV Light:

• A photomask or phototool is used to project a specific pattern onto the photoresist-coated substrate. The exposed areas of the photoresist become chemically altered and become either more or less soluble depending on the type of photoresist used.

5. Development:

• The substrate is then immersed in a developer solution. The developer removes the soluble regions of the photoresist, revealing the underlying metal surface in a pattern that corresponds to the exposed areas of the photoresist.

6. Etching:

• The substrate, with the developed photoresist pattern, is immersed in an etching solution, which chemically removes the exposed metal areas. The etching solution can be an acid or alkaline solution depending on the specific metal being etched. Similar to dry film etching, the etchant selectively dissolves the metal while leaving the protected areas covered by the photoresist untouched.

7. Rinsing and Inspection:

• After etching, the substrate is thoroughly rinsed to remove any remaining etchant and residual photoresist. The etched features are inspected for accuracy and quality at this stage.

8. Stripping of Photoresist:

• The photoresist is typically removed after etching. This can be done using a solvent that dissolves the photoresist without affecting the etched metal features.

9. Additional Processing (Optional):

• Depending on the specific application, additional processes such as passivation, plating, or other post-etch treatments may be applied to the metal substrate to enhance its properties or protect it from environmental factors.

10. Final Inspection and Quality Control: – The finished metal component undergoes a final inspection to ensure that the etched features meet the required specifications and quality standards. This may involve measurements, visual inspections, and other quality control procedures.

Wet film etching offers many of the same advantages as dry film etching, including high precision, customization, and compatibility with various metal substrates. However, it has its own set of considerations and requirements, such as the need for liquid photoresists and precise control of the coating and soft baking processes. Wet film etching is commonly used in industries that require intricate metal components and where the flexibility of using liquid photoresists is beneficial.

Wet film etching, as an alternative to dry film etching, possesses several distinctive features and advantages, making it suitable for specific applications.

• Homogeneous Coating Thickness:
  • Wet film etching allows for the deposition of a highly uniform and consistent photoresist layer on the metal substrate. This results in even etching across the entire surface, reducing variations and defects in the final product.
• Excellent Adhesion:
  • Liquid photoresists can offer strong adhesion to metal substrates, ensuring that the resist adheres firmly during the etching process. This helps maintain the integrity of the mask pattern and prevents delamination.
• Variety of Photoresists:
  • Wet film etching can use a wide range of photoresist types, including positive and negative photoresists, each with its own characteristics. This versatility allows for the selection of the most suitable resist for the specific application.
• Versatile Substrate Compatibility:
  • Wet film etching is compatible with various metals and alloys, similar to dry film etching. This versatility enables manufacturers to choose the material that best suits their requirements.
• Multi-Layer Etching:
  • In some cases, wet film etching can be used for multi-layer etching processes where different metals or materials are etched sequentially, allowing for complex component manufacturing.
• High Aspect Ratio Etching:
  • Wet film etching can achieve high aspect ratio features, meaning it is capable of etching deep, narrow channels or holes in metal substrates. This is crucial for certain microfabrication applications and MEMS devices.
• Controllable Etching Rate:
  • The etching rate in wet film etching can often be precisely controlled by adjusting parameters such as etchant concentration, temperature, and agitation. This control is important for achieving specific etching depths or feature dimensions.
• Rapid Prototyping:
  • Wet film etching is suitable for rapid prototyping and small-batch production, providing a quicker turnaround time compared to some other metal fabrication methods.
• Minimal Tool Wear:
  • Since wet film etching is a chemical process, it does not involve physical tooling or machining. Consequently, there is no tool wear, which can be advantageous for maintaining consistent quality over time.
• Environmental Considerations:
  • Similar to dry film etching, wet film etching is generally considered environmentally friendly as it does not produce significant hazardous waste or emissions, particularly when using environmentally friendly developer and etchant solutions.
• Integration with Other Processes:
  • Wet film etching can be easily integrated into larger manufacturing processes, making it compatible with subsequent steps such as plating, passivation, or additional patterning steps.
• Quality Control and Inspection:
  • Wet film etching, like dry film etching, allows for rigorous quality control and process monitoring, ensuring that final components meet specified tolerances and standards.

Wet Film Precision Metal Etching Process:

Equipment:

• Coater for Wet Film Resist:
  • Purpose: Used to evenly apply a wet film resist onto the metal surface.
• Drying Oven:
  • Purpose: Dries the wet film resist after application, ensuring proper adhesion and consistency.
• UV Exposure Unit:
  • Purpose: Exposes the dried wet film resist to UV light through a photomask, creating a pattern on the resist.
• Developer:
  • Purpose: Contains a chemical solution that removes the unexposed portions of the wet film resist, revealing the metal surface beneath.
• Etching Machine:
  • Purpose: Selectively removes metal from the exposed areas using chemical etching solutions, creating the desired pattern.
• Stripping Machine:
  • Purpose: Removes any remaining wet film resist from the metal surface after etching.

Workflow:

• Metal Cleaning:
  • Clean the metal sheet or component to remove impurities and contaminants.
• Wet Film Resist Application:
  • Place the metal sheet or component in the coater.
  • Apply the wet film resist evenly onto the cleaned metal surface. This resist is typically a liquid that covers the entire surface.
• Drying:
  • Transfer the metal with the applied wet film resist to a drying oven.
  • The oven dries the resist, evaporating any solvents and ensuring that the resist adheres properly to the metal.
• Exposure:
  • Place the metal with the dried wet film resist under the UV exposure unit.
  • Expose the resist to UV light through a photomask that carries the desired pattern. The UV light cures the resist in the exposed areas, making it resistant to etching.
• Development:
  • Transfer the exposed metal to the developer.
  • The developer contains a chemical solution that dissolves the unexposed portions of the wet film resist, revealing the metal surface underneath. This reveals the pattern for etching.
• Etching:
  • Immerse the metal into the chemical etching machine containing the etching solution.
  • The chemical selectively removes the exposed metal areas, leaving the protected areas intact. Etching continues until the desired depth or pattern is achieved.
• Rinsing and Cleaning:
  • Rinse the metal thoroughly with water or a suitable rinse solution to remove etching chemicals and residues.
• Stripping (if needed):
  • Use a stripping machine or stripping chemicals to remove any remaining wet film resist from the metal surface. This step ensures a clean, finished product.
• Final Inspection:
  • Inspect the etched metal for quality, accuracy, and adherence to specifications.
  • Any necessary post-processing or quality control checks are performed at this stage.

The wet film precision metal etching process is suitable for applications where fine details and intricate patterns are required. It offers an alternative to dry film etching and is commonly used in industries such as electronics, microfabrication, and precision engineering.

If you are interested in finding out about Wet Film Metal Etching Equipment overall price. Please do not hesitate to contact us. Usually we will contact you within 2 days after we receive your information.

Dry film etching is a crucial step in the precision metal etching process, which is a highly precise and controlled technique for creating intricate patterns and features on thin metal sheets or foils. This process is often used in various industries, including electronics, aerospace, medical devices, and more, where precision and accuracy are paramount.

Here are some additional features and aspects to consider about dry film etching:

• High Precision and Accuracy:
  • Dry film etching is known for its exceptional precision and accuracy. It can create intricate and finely detailed patterns with tolerances as tight as a few micrometers. This level of precision is essential for manufacturing components used in electronics and other high-tech applications.
• Cost-Effective for Prototyping and Small Production Runs:
  • Dry film etching is well-suited for prototyping and small production runs. Unlike some other manufacturing processes that require expensive tooling or molds, dry film etching is more cost-effective for producing small quantities of complex metal parts.
• Customization and Design Flexibility:
  • Design changes can be implemented relatively easily in the dry film etching process. Since it involves exposing a resist to a mask, altering the mask design allows for rapid changes in the final etched pattern. This flexibility is advantageous when designing custom components.
• Material Compatibility:
  • Dry film etching is compatible with various metals and alloys, including stainless steel, copper, aluminum, and more. This versatility allows manufacturers to choose the material that best suits the application’s requirements.
• No Tool Contact:
  • Unlike some traditional machining processes that involve physical tooling, dry film etching is a non-contact method. This eliminates the risk of tool wear and damage to the substrate, making it ideal for delicate or thin materials.
• Minimal Heat Generation:
  • Dry film etching is a cold-etching process, meaning it does not generate significant heat during the etching stage. This lack of thermal stress minimizes the risk of material distortion or warping, which is particularly important for thin metal foils.
• Burr-Free and Stress-Free Etching:
  • The process produces burr-free edges and stress-free parts. This is crucial for components used in sensitive applications like microelectronics and medical devices, where sharp edges or residual stress can be problematic.
• Scalability:
  • Dry film etching can be scaled up for larger production volumes when needed. This scalability makes it adaptable for both small-scale and large-scale manufacturing.
• Environmental Considerations:
  • Dry film etching is generally considered to be a more environmentally friendly process compared to some other metal fabrication methods, as it does not produce large quantities of hazardous waste or emissions.
• Quality Control and Process Monitoring:
  • Due to its precision, dry film etching allows for robust quality control and process monitoring. Manufacturers can closely monitor each step of the process to ensure that the final components meet the required specifications.
• Wide Range of Applications:
  • Dry film etching is used in diverse industries, including electronics for printed circuit boards (PCBs), microelectromechanical systems (MEMS), sensors, medical devices, aerospace components, and more. Its versatility makes it applicable in various fields.

Overall, dry film etching is a highly specialized and valuable manufacturing process that excels in producing precise, intricate metal components while offering flexibility and cost-effectiveness for both small-scale and large-scale production.

Dry Film Metal Etching Equipment:

• Metal Cleaning Machine:
  • Purpose: Used to clean the metal surface, removing contaminants to ensure proper adhesion of the dry film resist.
• Pressure Layer Machine:
  • Purpose: Precisely applies the dry film resist onto the metal surface, ensuring uniform adhesion and thickness.
• Exposure Machine:
  • Purpose: Exposes the dry film resist to UV light through a photomask, creating a pattern on the resist.
• Developer:
  • Purpose: Contains a chemical solution that removes the unexposed portions of the dry film resist, revealing the metal surface beneath.
• Etching Machine:
  • Purpose: Selectively removes metal from the exposed areas using chemical etching solutions, creating the desired pattern.
• Stripping Machine:
  • Purpose: Removes any remaining dry film resist from the metal surface after etching.

Dry Film Metal Etching Workflow:

• Metal Cleaning:
  • Clean the metal sheet or component to remove impurities and contaminants.
• Pressure Layer:
  • Apply the dry film resist onto the cleaned metal surface using the pressure layer machine. Ensure uniform adhesion and thickness.
• Exposure:
  • Place the metal with the dry film resist under the exposure machine.
  • Expose the resist to UV light through a photomask that carries the desired pattern.
• Development:
  • Transfer the exposed metal to the developer, which removes the unexposed resist, exposing the metal underneath.
• Etching:
  • Immerse the metal into the chemical etching machine containing the etching solution. The chemical selectively removes the exposed metal areas, leaving the protected areas intact.
• Rinsing and Cleaning:
  • Rinse the metal thoroughly to remove etching chemicals and residues.
• Stripping (if needed):
  • Use stripping chemicals to remove any remaining masking material (resist) from the metal surface.
• Final Inspection:
  • Inspect the etched metal for quality and accuracy.

If you are interested in finding out about Dry Film Metal Etching Equipment overall price. Please do not hesitate to contact us. Usually we will contact you within 2 days after we receive your information.