If you are in the manufacturing business, photography or have an artistic taste, you probably have heard of the term photo etching being tossed about. It can also be that you have never come cross the word but need some knowledge on it. Whichever category you fall in, here comes the question…what is photo etching?
First of all, it should be noted that photo etching, photochemical milling and photochemical machining are one and the same thing. It is a process of subtractive manufacturing where chemicals are used to fabricate metal sheets in the desired pattern, shape and thickness. Through the process, various parts and textures can be achieved.
What takes place in photochemical machining?
The material to be imprinted on also the substrate is laminated with a photoresist (light-sensitive resist) and UV light shone on it. This is done to get apositive image of the material. After subjecting the product to UV light, the selected geometric pattern is transferred. The patterned substrate is then subjected to an etching solution which is chemical treatment that selectively corrodes the unprotected parts.
Steps in photochemical milling
Like every industrial process, photo etching is a step by step process which is followed systematically to reach the required results. These steps are grouped into front-end and back-end procedures. They include:
Step 1: Design selection
The design to be imprinted on the material is the initial step as it determines what will happen throughout the other steps. Once the design has been selected, then the work can start.
Step 2: Material selection
In photochemical milling, there are a number of materials that can be used. Some include; stainless steel, brass, copper, aluminium, mild steel and nickel alloys among others. Whichever material is to be used is nominated at this step.
Step 3: Cleaning of the material
Surface of the selected material is degreased and cleaned before any procedure takes place.
Step 3: Lamination
It is quite obvious that you may have an idea on what lamination is all about. Maybe at one point or another you had gotten a document laminated. That also applies here but in this case a photoresist is what is being laminated. It is laminated at the top and bottom of the sheet and it is important that the resist is well attached so as to prevent the etchant from damaging the material.
Step 4: Image printing
At this step, Laser direct imaging is used to expose the photo resist to UV light. The resist then hardens.
Step 5: Development
After the UV treatment, only the exposed resist is left intact while the rest is removed. This resist remains in order to protect the underlying material during the whole procedure.
Step 6: Etching
The real business takes place here where the now developed sheets are sprayed with the required chemicals and are allowed to settle for some time.
Step 7: Stripping (of the resist)
Once the etching is done the exposed resist is stripped away because its role of protection has been accomplished.
Step 8: Inspection
Before the photo etching is considered a done deal, inspection of the finished products must be done. With the inspection all dimensional and cosmetic defects are sought out.
Step 9: Finishing
Depending on the specific manufacturer, different value additions such as plating can be done.