Photochemical Etching Process

The PCM Process

The process is typically completed as follows:

1. Phototool / Artwork Generation

The phototool serves as the master tooling used to produce the part and can be reused for future production runs.

Tooling is created from customer-supplied CAD data or, when CAD files are unavailable, generated from a dimensional drawing or print. The part geometry is reproduced and adjusted to compensate for variables inherent to the chemical etching process, including material type, material thickness, feature size and anticipated etch characteristics.

Once the artwork is completed, multiple part images are stepped and repeated to efficiently utilize the available sheet area. The top and bottom phototools are then precisely registered to one another.

Because photochemical machining uses digital artwork and photographic tooling rather than conventional hard tooling and dies, tooling modifications can often be made quickly and economically when a design changes.

2. Material Preparation

Proper surface preparation is essential to achieving consistent photoresist adhesion and high-quality etched components.

Metal is cut to the appropriate panel size based on the phototool layout. The material is then thoroughly cleaned to remove oil, grease, dirt and other surface contaminants that could interfere with photoresist adhesion or subsequent processing.

Careful material preparation helps ensure that the photoresist bonds uniformly to the metal surface and that fine features and dimensional details are maintained throughout the photo etching process.

3. Photoresist Coating

After cleaning and surface preparation, both sides of the metal are laminated with a UV-sensitive dry film photoresist. The photoresist acts as a protective barrier during chemical etching, allowing selected areas of the metal to remain while exposed areas are chemically removed.

Etchit utilizes multiple thicknesses of dry film photoresist to accommodate a wide range of raw material thicknesses and processing requirements. The appropriate resist thickness is selected based on factors such as material thickness, component geometry, feature size, and the anticipated etching time.

The dry film is applied using controlled heat and pressure to create uniform adhesion across both sides of the metal panel. Proper lamination is critical to maintaining image definition and protecting the metal surface throughout the etching process.

By matching the photoresist to the material and application, Etchit can effectively process everything from very thin precision metal components to heavier-gauge parts requiring longer etching cycles.

4. Photoresist Exposure

Once coated, the prepared metal panel is positioned between the precisely registered top and bottom phototools.

The panel is exposed to controlled high-intensity ultraviolet (UV) light, transferring the component pattern from the phototool into the photoresist coating on both sides of the material.

Exposure time and light intensity are carefully controlled because they directly influence image definition and the ability to reproduce fine features.

Double-sided exposure allows features to be etched simultaneously from both sides of the material, an important advantage of the photochemical machining process.

5. Photo Developing

Following exposure, the panel moves through the developing process.

The exposed areas of photoresist representing the component geometry have been hardened by UV light. The remaining unwanted resist is removed through a controlled chemical developing process, revealing the bare metal that will subsequently be removed during etching.

After development, the panel contains a precise resist image of the desired components. Areas protected by photoresist will remain, while exposed metal areas are ready for chemical removal.

Proper developing is critical for maintaining feature definition, dimensional consistency, hole sizes, slots, webs, and other intricate geometries.

6. Etching / Chemical Milling

The developed panels are processed through Etchit’s controlled chemical etching lines, where unwanted metal is removed.

A typical etching process uses an aqueous ferric chloride solution maintained within controlled operating parameters to provide a consistent and predictable metal removal rate. As the panel travels through the etching equipment, etchant is applied to both sides of the material.

The exposed metal is gradually dissolved while areas protected by photoresist remain intact. Etching continues until the unwanted material has been completely removed, leaving the finished component geometry defined by the phototool.

Because material is removed chemically, photochemical machining produces components without the burrs, heat-affected zones, and mechanical stresses commonly associated with many conventional metalworking processes.

After etching is complete, the remaining photoresist is stripped from the metal, revealing the finished parts for cleaning and inspection.

7. Inspection and Quality Control

Quality control is an integral part of Etchit’s photochemical machining process.

After etching and stripping, components are inspected in accordance with applicable customer, drawing, purchase order, and internal quality requirements. Inspection typically includes dimensional measurement, visual inspection, feature verification, and other specified requirements depending on the application.

Modern optical inspection equipment allows complex component geometries to be measured efficiently while maintaining repeatable inspection methods for ongoing production.

Etchit’s Quality Management System is certified to ISO 9001:2015, providing a documented framework for process control, inspection, traceability, and continuous improvement.

Following final inspection and completion of any required secondary operations, parts are cleaned, packaged, and shipped according to customer requirements.