phototool making for PCM
Photochemical Machining (PCM), also widely known as photochemical etching or chemical milling, is a non‑contact subtractive cold‑processing technology for thin‑gauge metal sheets. It uses photoresist masking and chemical etchant to selectively remove material without mechanical force or thermal deformation. It is extensively applied to produce encoder discs, filter meshes, precision shims, EMI shielding parts and micro‑components for semiconductor, medical, electronics and aerospace industries.
Every phase determines final dimensional accuracy, edge quality and batch consistency. Below is the complete manufacturing process of photochemical machining.
1. CAD Drawing Review & DFM Analysis
The whole workflow starts with customer‑provided CAD / DXF drawings. ‑ Engineers review dimensions, tolerances, hole layouts, feature width and material specifications. ‑ Carry out DFM (Design for Manufacturability) check, identify fragile narrow ribs, tiny isolated features and potential etching risks. ‑ Apply etching‑factor dimension compensation for inner and outer contours, then generate files for phototool production.
2. Phototool Fabrication
A high‑precision phototool (photomask) is produced from the compensated artwork file. ‑ Double‑sided matched phototool films are prepared for symmetrical double‑sided etching. ‑ The phototool contains inverse pattern: transparent areas correspond to regions to be etched away, black opaque areas protect the part geometry. ‑ High‑accuracy registration of top‑side and bottom‑side phototools guarantees alignment during UV exposure.
3. Metal Sheet Cutting & Surface Cleaning
‑ Select qualified metal sheet according to order requirements: stainless steel, copper, brass, nickel alloy, spring steel etc. Typical thickness range 0.02 mm‑2.0 mm. ‑ Cut raw material into working panel size. ‑ Multi‑stage cleaning: degreasing, alkaline washing, acid activation and full drying. Remove oil, fingerprints and oxide layers completely. Poor cleaning will cause photoresist delamination and pattern defects.
4. Photoresist Lamination
Dry‑film photoresist is hot‑laminated onto both surfaces of the cleaned metal panel. The photoresist is UV‑sensitive polymer which forms protective mask after exposure. Uniform lamination pressure and temperature are critical for stable pattern transfer.
5. UV Vacuum Exposure
‑ Align double‑sided phototool tightly against the photoresist‑covered metal sheet under vacuum condition to eliminate air gaps. ‑ Ultraviolet light passes through the transparent areas of phototool and cures / polymerizes the corresponding photoresist. The regions under black mask remain un‑polymerized and soluble in developer solution.
6. Developing
The exposed panel goes through developing chemical solution. Un‑exposed, un‑hardened photoresist is washed away, exposing bare metal areas ready for etching. UV‑hardened photoresist stays firmly bonded to metal as protective mask, exactly reproducing the target part geometry.
7. Core Chemical Etching Stage
This is the key forming step of photochemical machining. ‑ The developed panel passes through automated etching chamber. Etchant (mostly ferric‑chloride‑based solution) is sprayed symmetrically from top and bottom nozzles. ‑ Unprotected bare metal is chemically dissolved from both sides simultaneously. Etching temperature, spray pressure, conveying speed and solution concentration are strictly controlled. ‑ Metal dissolves until through‑cut is achieved for outer contours and holes. The photoresist‑covered zones remain intact to form finished parts.
8. Photoresist Stripping & Multi‑Rinse
‑ After etching completion, panels are rinsed to halt chemical reaction immediately. ‑ Alkaline stripping solution removes the cured photoresist mask completely. ‑ Multiple‑stage water washing removes residual etchant and stripping chemical, then full drying. At this stage, the burr‑free, stress‑free metal parts are already shaped.
9. Post‑Processing & Secondary Operations
According to customer requirements, optional secondary processes can be carried out: ‑ Deburr / tab removal, flatness correction ‑ Electropolishing, passivation ‑ Bending, forming ‑ Surface treatment: plating, coating ‑ Custom packaging preparation
10. Inspection & Quality Control
‑ Optical dimension inspection: 2D vision measuring system verifies critical dimensions, aperture, tolerance compliance. ‑ Visual check for micro‑defects: pinholes, over‑etching, incomplete cut‑through. ‑ Sampling flatness test, edge‑quality assessment. ‑ Batch‑traceable quality records are kept.
11. Packaging & Delivery
Qualified parts go into dust‑proof, anti‑oxidation vacuum packaging to avoid scratching and oxidation during transit, then shipped globally.
Key Advantages Brought by PCM Process
‑ Zero mechanical stress, no burrs on hole and contour edges ‑ Can manufacture complex micro‑features, fine slots and dense hole arrays ‑ No hard stamping dies; low‑cost phototool supports fast prototyping and mass‑production ‑ Consistent repeatability from small‑batch samples to large‑volume orders
If you need photochemical machining service, send your CAD drawings for DFM review and quotation.
