VACCO’s Photo Etching Design Guide was generated for those new to the photo etching process with the hope it will serve as an industry reference and raise awareness of our etching capabilities. VACCO encourages you to utilize these tools and information when developing your next prototype requirements. If you have any questions, please feel free to contact our Sales Team for personal assistance in your design requirements.
Advantages of Photo Chemical Etching
As complex or challenging as your design may seem, VACCO’s photo chemical etching process makes producing intricate parts effortless. Photo Chemical Etching is a fast and relatively inexpensive way to produce a wide variety of metal parts, with continuous accuracy VACCO’s consistency is possible with our tooling capabilities. VACCO’s photo tools are computer generated which increases accuracy while reducing tooling costs, in comparison to the competition that uses hard tooling.
How it Works
- VACCO takes your drawing or sketch reflecting the exact specifications of your part or design needs. If you don’t have a drawing, simply call our Sales Team to help turn your idea into full realization.
- Once the drawing and its specifications have been verified and customer approved, VACCO’s team of certified lab technicians will proceed with producing an Auto-Cad Photo Tool to transfer your exact specification into photo etched parts.
- Using the Photo Tool, VACCO’s lab technician can now transfer the part/image(s) onto a clean metal sheet from the customer pre-specified material. Before imaging, the metal sheet will first be laminated with UV sensitive film referred to as a “photoresist” Industrial process
- Using the photo tool and the photoresist laminated metal, the metal sheet can then be exposed to a UV light source that transfers the exact requirements onto the laminated sheet of material.
- After exposure and before etching, the exposed laminated sheet must be developed allowing the unwanted soft photoresist material to be removed and the required hardened photo resist to remain thus creating the pattern to produce your etched parts.
- Using the developed sheet of metal VACCO’s lab technician can now chemically etch away the defined pattern of metal from the metal sheet, leaving the desired photo etched part(s).
- After the etching process is completed VACCO’s lab technician wash away the photoresist, perform a final inspection and packaging procedure before the parts are shipped to the end user.
Dimensions & Tolerances
There are no specific ground rules regarding etching tolerances however, there are some variables which can have an impact on maintaining etching tolerances. Consider the following when developing prototype specifications:
- The type of specified metal material.
- The thickness of the specified material.
- The physical size of the parts’ and its desired features.
- The process sheet size and the number of critical part dimensions.
Generally speaking, etched dimensional tolerances are ±10% of the metal thickness. If a part is made of 0.010″ thick stainless steel, then the general rule is that the dimensional tolerance of the parts’ features is ± 0.001″ (or 10% of the material thickness.)
For more information please don’t hesitate to call the VACCO Sales Engineering Team.
Hole Size/ Slot Width to Metal Thickness
Typically, the diameter of a hole or slot width can’t be less than 1.1 times the material thickness. However, the relationship varies when metal thicknesses changes. Below is a chart gives an explanation of the relationship between the hole size to metal thickness.
- Metal Thickness (t)
- Smallest Hole Diameter (d)
- Less than .001″
- TBD by test run
- .001″ – .006″
- At least Metal Thickness
- .006″ or Over
- At least 110% Metal Thickness
Line Width to Metal Thickness
Spacing between holes and slots becomes a design factor when a part contains a large number of holes and/or slots. The metal between the holes is referred to as “Bar Width.” There are limitations as to how small the bar width between holes can be. In metals less than .005″ thick, bar widths must be at least equal to the metal thickness.
Inside & Outside Corner Radius to Metal Thickness
The smallest corner radius is proportional to the metal thickness. However, there are circumstances where the radius can be smaller, depending on the requirements.
Outside corners etch sharper than inside, so radii less than material thickness are easily obtainable.
If etching variance is a requirement, please specify the percentages needed at the time of order.
Tabs or Tie-Ins
Tabbing is performed by connecting one or more lines of metal from the part to the process sheet border or tie bars to keep parts in place. These tie-ins are made as few and as small as possible keeping consistent with the size of the parts being etched. Tabs are beneficial for parts with tighter tolerances, and those undergoing plating operations, not to mention they are cost efficient and will help produce a higher yield of quality product. Two common variations of tabbing most widely used include:
External Tab – These have a break off point, which leaves a small “burr” attached to the part.
Recessed Tab – Like external tabs, recessed tabs have a breaking point, only it becomes recessed into the actual part. VACCO recommend this application if the product specifications require tabbing, but cannot have extended areas beyond its perimeter.
If outside requirements are crucial or the preference is to avoid tabbing all together, then consider drop outs. These are tab free parts, meaning the part does not remain in the sheet during the etching process. This method is recommended for metals with a thickness of .010″ or thicker. Be advised, a drop out is less consistent, has looser tolerances and therefore is more expensive to handle, inspect and package in comparison to a tabbed part.