Etchit Photochemical Etching
Home Company Profile ETCHIT Services ETCHIT Design Guide Sample Parts Gallery Contact Us Site Map

About PCM - Photochemical Etching

Photochemical Machining (PCM) Also known as Photo Etching, photochemical milling or chemical milling is a process of manufacturing that emerged in the 1960's as an offshoot of the printed circuit board industry. Typically the process is accomplished as follows...

  1. Phototool/Artwork Generation... Photo tooling becomes the master tool for all future production runs. Tooling or artwork is designed from a CAD file or drawn from a print if CAD file is not available. The process involves taking an exact replica of the part and compensating dimensions for etch factors such as material type and material thickness. Once drawn, the image is stepped and repeated on a set of mylar films. The films are then registered within .0005".
  2. Material Preparation... Material is cut to length based on part size and photo size and then thoroughly cleaned to remove all dirt, grease and mill oils from the surface so to ensure the adhesion of photoresist.
  3. Photoresist Coating... Photoresist is a UV light sensitive coating that may be applied in a variety of ways. Etchit's custom manufactured liquid resist dip coater allows for coating of extremely thin materials, as thin as .0005". In addition, our DuPont dry film laminator gives us the flexibility to increase material thickness by using a hot roll laminator for better adhesion when product calls for increased etching times.
  4. Photoresist Exposure... After coating, material is put into the double sided photo tool and exposed to high intensity light on both sides. Timing and intensity of light is critical to cure the image onto the photoresist. Etchit's two tray Colight exposure unit allows us to develop both liquid resist and dry film resist without interruption.
  5. Photo Developing... During exposure, the image is hardened onto the material, however, all remaining resist must be removed. A liquid chemical bath along with high pressure spray will remove all unwanted resist and leave only the exact image of the part.
  6. Etching/Chemical Milling... Panels are then fed through one of our Chemcut etching lines. Typical etching bath consists of an aqueous ferric chloride bath maintained to a certain chemical composition to achieve a constant etching rate along with a lower environmental impact. The result, unwanted material is “etched” away leaving only the parts as designed on the photo tool. Photoresist is stripped away prior to inspection.
  7. Inspection... Parts then go through a rigorous inspection process. Etchit typically inspects based on an AQL of 2.5, however, if a more intense inspection criteria is necessary we can accommodate. Upon completion of inspection, parts are shipped as requested. The process can offer economical alternatives to metal stamping, punching, laser or water jet cutting. It is a particularly more affordable alternative to electrical discharge machining (EDM) for thin gage precision parts. The tooling is inexpensive and quickly produced making the process useful for prototyping and allows for easy design changes if needed. Finished parts are burr and stress free, no sharp edges.

Standard Tolerances

Standard Tolerances Guide

Material Thickness (Inches)










> .035"

Copper/Beryllium Copper +/-. 0003" +/- .0005" +/- .001" +/- .001" +/- .0015" +/- .002" +/- .003" +/- .0035"  
Kovar +/- .0005" +/- .0008" +/- .001" +/- .0015" +/- .002" +/- .0025" +/- .003" +/- .004"  
Nickel/Nickel Silver +/-. 0003" +/-. 0005" +/- .001" +/- .001" +/- .0015" +/- .002" +/- .003" +/- .004"  
Stainless Steels +/-. 0005" +/- .0008" +/- .001" +/- .0015" +/- .002" +/- .0025" +/- .003" +/- .004"  
CRS/Blue Temp Steel +/-. 0005" +/- .0008" +/- .001" +/- .0015" +/- .002" +/- .0025" +/- .003" +/- .004"  
Phos Bronze +/-. 0005" +/- .0008" +/- .001" +/- .0015" +/- .002" +/- .0025" +/- .003" +/- .004"  
Other Materials Consult one of our sales specialists for additional metals and tolerances…

Industry Terms

Photochemical Machining (PCM) - also known as photochemical milling or photo etching, is the process of fabricating sheet metal components using a photoresist and etchants to corrosively machine away selected areas. This process emerged in the 1960's as an offshoot of the printed circuit board industry. Photo etching can produce highly complex parts with very fine detail accurately and economically.

This process can offer economical alternatives to stamping, punching, laser or water jet cutting, or wire electrical discharge machining (EDM) for thin gauge precision parts. The tooling is inexpensive and quickly produced. This makes the process useful for prototyping and allows for easy changes in mass production. It maintains dimensional tolerances and does not create burrs or sharp edges. It can make a part in hours after receiving the drawing.

PCM can be used on virtually any commercially available metal or alloy, of any hardness. It is limited to materials 0.0005 to 0.080 in (0.013 to 2.03 mm) thick. Materials can include aluminum, brass, copper, inconel, manganese, nickel, silver, steel, stainless steel, zinc and titanium.

Photoresist - is a light-sensitive material used in several industrial processes, such as photolithography and photoengraving to form a patterned coating on a surface.