Introduction

Chemical etching, also known as “industrial etching” or “chemical milling”, is a subtractive process in manufacturing. It involves the immersion or spraying of metals with temperature-regulated chemicals in order to remove specific areas in the metal to produce the desired shape, thickness and intricate designs or geometric features.

With chemical etching, manufacturers are enabled to create metal parts even with the most difficult and intricate of designs, all while achieving high repeatability and consistent production quality.

How Does Chemical Etching Work?

The traditional chemical etching process comprises of a series of several steps:

• Cleaning: This step involves the preparation of the metal surface to be etched by removing grease, oils, residues and other contaminants. Cleaning is an extremely important step because a contaminated surface could result in poor adhesion of the photoresist film, which in turn causes defects. Upon completion of this process, workers should never handle the material with their bare hands as the sweat and oils from the human skin may contaminate the material.
• Lamination: This step involves the application of dry film photoresist to the surface. Photoresist protects the areas of the metal that will not be etched. These films are applied to both sides simultaneously by rolling or laminating onto the material using pressure, temperature and sometimes water.
• Exposure: In this step, the material is guided between two “masks” which have the negative image of the component to be created. These masks are made of either mylar or glass. Thereafter, high intensity, collimated, ultraviolet light is shined from both directions through the masks, crosslinking the film in locations where the light is not blocked by the mask images.
• Developing: After exposure, the material must be developed. This step chemically dissolves the non-crosslinked film that exposes the bare metal beneath. The material left protected by the film will ultimately be the finished product.
• Etching: After developing, the metal is fed into etch chambers where etchant is sprayed both from the top and bottom simultaneously. This process etches or dissolves the unprotected metal to achieve the desired product. An etchant bath requires careful monitoring of the concentration, composition, temperature of and time in the etchant.
• Stripping: In this process, the film is removed from the etched product using another concentration of chemistry.
• Rinsing and Drying: At this stage, the product is complete and the films removed. Significant rinsing is required to remove all residuals. This is likely performed using reverse osmosis water and deionized water.

Materials Suitable for Chemical Etching

Metals suitable for chemical etching include a wide range of stainless steels, nickel alloys, copper, brass, beryllium copper, and phosphor bronze.

Reel-to-reel Etching

Numerous advancements have been made in the chemical etching process, allowing for reel-to-reel processing, vertical integration, greater tolerances and repeatability, and improved time-to-market. With these innovations, it is now possible to perform half-etching procedures for special and more difficult applications, including sharp beveled tips and edges, capillary grooves, hand break-offs and other intricate features. Interplex uses a fully computerized process control system, ensuring high quality, uniformity and consistency of the products during processing, and excellent repeatability.

Advantages of Reel-to-Reel Etching

Using a tightly controlled reel-to-reel etching process is important to maintaining close tolerances and a high degree of repeatability combined with high-volume production output. Unlike panel etched parts, reel-to-reel etching is inherently automation friendly and allows for smooth integration of secondary processing steps. For example, the etched metal parts can be easily formed, plated or insert molded using various types of automated equipment.

The key advantages of reel-to-reel etching include:

• The ability to hold very tight tolerances for small feature sizes with a very high degree of repeatability and consistency.
• Increased repeatability and consistency that significantly reduces the total cost of quality, especially in high reliability applications.
• Burr-free, precision metal components with ultra-fine pitches, intricate shapes and 3D feature profiles are possible, which are unavailable using traditional metal stamping processes.
• Chemically etched parts can be produced in a high volume environment, which reduces tooling and production costs while improving time to market.
• Reel-to-reel etched parts can be presented to other automated processes such as forming, plating, insert molding and assembly on a reel, further reducing total manufacturing costs.

The degree of precision and consistency achievable offers a continuous chemically etched metal strip and a mass production advantage alternative to the standard panel or sheet etching process. The excellent control and flexibility enables the reel-to-reel chemical etching approach to design and deliver parts that meet virtually any specific set of application requirements.

Chemical etching is an excellent methodology for creating high-precision metal parts that are complex and multi-layered. It is also the best process for the creation of straight, sharp or profiled edges, and round holes.

As a viable, purposive option against conventional stamping and other manufacturing processes, it allows for the production of complex and intricate metal parts which cannot be accomplished through other production methods.