Understanding The etching Process

Chemical etching is a widely used technique in the manufacturing industry for selectively removing material from a substrate using chemical reactions. The process involves using a chemical solution, known as an etchant, to dissolve certain parts of the substrate while leaving others intact. It is often used because it can be more cost-effective than other methods such as laser cutting, stamping, and electro-discharge machining. Not only is it more cost-effective, but it can also manufacture products without heat stress, burrs, or material hardness restrictions. It is because of these benefits, this technique has been applied in various industries such as electronics, aerospace, automotive, and many others. In this blog, we will discuss the fundamentals of chemical etching to provide you with a basic understanding of how the process works.

Raw Materials

To start chemical etching, you will need to pick out material you want to etch. Chemical etching can be performed on several different materials such as copper, steel, brass, aluminum, gold, nickel, titanium, glass, and more.

Clean

Once you have the raw material of what you want to etch, you will start by cleaning the surface of the material. It is a common practice to use an acidic cleaner or a micro-etch solution that will remove oils and contaminants that may interfere with the chemical etching process. This phase can also be done mechanically instead of utilizing chemicals. In some cases, people use mechanical brush systems to clean off the surface of the material they want to process.

Laminate

With the panels being clean, the next step is to laminate the panels with a photoresist. A photoresist is a film that can be applied to the surface of the material you want to etch. This photoresist is sensitive to light and polymerizes when it is exposed to light. By laminating our panels with this film, we can focus UV light on specific parts of the panels to select the parts of the metal we want to keep for our product. This process is typically done inside what is known as a yellow room -- a room that utilizes yellow lights. The yellow lights make it so when we are applying the resist to our panel, it does not polymerize in uncontrolled ambient light.

Expose

After applying the photoresist, we want to selectively expose areas of the panel to UV light. By polymerizing sections, we are forming a film that will be effective in preventing the metal underneath it from being etched away in the etching stage. There are a few methods we can use for selective exposure. One way to do it is through laser. There are machines available that use a laser to put the image directly onto film. The most common method is through contact printing. Contact printing is where a transparent mask with blacked-out sections is used to control the exposure. This mask is laid across the panel prior to exposure. In the exposure process, the entire panel is flooded with UV light. The only parts that get polymerized are the areas that were left transparent on the photomask because they receive the full effect of the UV light. The areas blacked out receive no polymerization because the UV couldn’t get through the photomask.  At the end of this process, we are left with our panel, fully laminated with some parts of the film polymerized and some parts not.

Develop

Since our panel is still left with the film with a mix of polymerized and unpolymerized sections, the next step is to remove the parts of the film that are unpolymerized. This step is called developing. What happens here is the panel is taken out of the yellow room and into the wet processing area. There the panel will run through a machine that has a chemical that will dissolve the unpolymerized photoresist and thus leave only the parts we noticed received exposure to UV light.

Etch

After developing, we now send our material through the etching phase. This is the stage where any parts of our panel, that do not have any photoresist on it, will be removed through what is essentially a controlled corrosion process. There are many different chemicals out there for chemical etching, but the one that will be used will depend on the material you are trying to etch. Once the panel is done being etched, we are left with our product but with a layer of photoresist still on it.

Strip

To get our final product, we now must remove the remaining photoresist through a process called stripping. In this stage, the panel is sent through another machine like the ones used for developing and etching, but this one utilizes a chemical that is specific to the photoresist to remove it in the form of easy to filter chips.

Many products you use daily may have been produced through this method of production. If you were to look at your cell phone as one example, you can potentially find several products made through etching (the touch screen glass, the circuit boards, the cooling units, etc.). If you want to learn more about chemical etching in depth, we highly encourage you to view some of our previous blog posts and our technical papers.