The photo chemical etching "chem-etch" process is used to produce very precise parts that would otherwise be difficult or impossible to manufacture using conventional fabrication methods. This technology was first commercially used during World War Two for producing gun sight reticles.

A brief outline of possibilities and limitations follows. This information is presented to provide the reader with rough guidelines rather than the maximum limits achievable by chem-etch.

Advantages of Chemical Etching

• SUPERIOR FOR PROTOTYPES: Excellent precision, repeatability, and accuracy, quick turn around. Engineering changes and modifications can be made quickly, easily, and inexpensively.
• LOW COST: Compared to hard tooled parts, the chem-etch photo tool is more efficient and far less expensive than typical hard tooling. Unlike hard tooling, complexity of a part is not a cost driver.
• NO HARD TOOLING: no major investments, no die maintenance and repair costs, no long tooling delivery delay. Photo tool lead time is normally 1-2 weeks and can be shortened if necessary. Photo tool charges are substantially lower than conventional die shop charges.
• NO METAL STRESS OR PART DEFORMATION: Chem-etched parts remain flat since the metal removal is achieved chemically, not mechanically.
• BURR FREE: Secondary deburring operations are eliminated since no metal to metal contact stress occurs.
• MATERIAL PROPERTIES: Remain unchanged. Temper of metal is not changed. Magnetic property is not affected.

Tolerances and Other Considerations

• Some BEVEL undercutting at the edges of all dimensions will occur. This BEVEL is approximately 20% of material thickness when etching the sheet from 2 sides.
• Hole size generally can not be less than material thickness.
• Outside radius corners are sharper than inside corners.
• Inside radius corners are usually limited to one half the material thickness.

Hole Sizes
MATERIAL THICKNESS	MINIMUM HOLE DIAMETER	TOLERANCE ±
.001"-.005"	Material thickness	.001
.006"-.010"	Min. 110% of material thickness	.0015
.010" and thicker	Min. 125% of material thickness	.002

MINIMUM MATERIAL BETWEEN PARTS OR ETCHED AREAS.
MATERIAL THICKNESS	SIZE OF MATERIAL WEB
Less Than .005"	Minimum of thickness of material.
Over .005"	125% Thickness of material.

Materials Commonly Used

Aluminum, Beryllium Copper, Brass, Copper alloys and Copper, Nickel Silver, Phosphorous Bronze, Stainless Steel, Steel.

Material thicknesses usually within a range of .0005" to .090"

Photo-Chemical Etching Process

1. Generate artwork on mylar from in-house CAD/CAM system or customer supplied data.
2. Clean and pre-treat the material.
3. Apply 1.5 mil dry PHOTO RESIST (photographically resistant) mylar layered film to the metal sheet to be etched.
4. Expose the film via UV (Ultraviolet) light to transfer the piece part photographically to the previously treated sheet of metal.
5. Develop the metal sheet thereby exposing the piece part image.
6. Chemically remove the unprotected material areas by etching.
7. Rinse and strip the photographically resistant film from the sheet.
8. Proceed to next steps of manufacturing operations, forming, dip brazing, hardware insertion, silk screening, etc.