What Is an Etchant?
Etchant is an agent that corrodes metals and metal oxides and is used to process substrates. Compared to processing methods such as pressing, etching is a method with superior microfabrication properties, and wet etching methods using etchant are more cost-effective and easier to mass-produce than dry etching using gases. The type of compound that reacts differs depending on the type of metal, so the appropriate etchant should be selected according to the substrate material.
Since etchant often contains strong acids, strong bases, and toxic compounds, it is necessary to select protective equipment and take safety measures prior to use.
Etchant Applications
Etching is a method of processing metals such as gold and aluminum, and metal oxides such as indium tin oxide (ITO) by immersion removal. There are two types of etching: dry etching, which uses gas, and wet etching, which dissolves the metal in a solution.
Compared to press processing, etching enables fine processing and is used in the production of printed circuit boards, semiconductor devices, and displays. In manufacturing, the two methods are used separately: dry etching is used when precision processing is required, and wet etching is used when cost and mass production are required.
Etching Methods and Etchant Types
Dry etching is an etching process using gas or plasma. It is superior in microfabrication, but requires special conditions such as a vacuum, making it costly and unsuitable for mass production.
Wet etching, on the other hand, uses etchant containing compounds that corrode metals. Different compounds react and dissolve differently with different types of metals, so a variety of etchants are available.
For example, some etchants contain strong acids such as hydrochloric acid and nitric acid, strong bases such as sodium hydroxide, and heavy metal ions with high oxidizing power such as iron(III) chloride.
Etchant Effluent Treatment
Etchant dissolves metals by ionizing them, so the liquid after use contains a large amount of heavy metal ions. Therefore, untreated etchant effluent cannot be discharged into the environment. Therefore, etchant waste treatment is generally outsourced to a specialized waste treatment company.
Since etchant effluent contains strong acids and bases, there is a risk that the container may corrode during storage, depending on the container material. Therefore, it is important to first select an appropriate container with chemical resistance. Etchant may be irritating to the skin and eyes before or after use. When handling etchant, the Safety Data Sheet (SDS) should be carefully read in advance, and appropriate protective equipment should be worn and handled with extreme caution.