Engineering Guidelines

PPF's chemical etching process is a highly precise, flexible, and cost-effective method of manufacturing thin metal parts. Because of the precision and the flexibility, the process is ideal for a number of applications, from screens and filters, to microfluidics channels.

Keep in mind that with our process, there is usually no price difference between one feature and 100!

This engineering guide will help answer questions relating to the capabilities and requirements driven by the process. Remember that due to on-going improvements in all aspects of our process, and because we continuously update our equipment, our capabilities are constantly improving. With this in mind, we are always willing to consider your most aggressive designs!

See our FAQs for a step-by-step description of the chemical etching process. If your questions aren't answered here, please don't hesitate to email, or call us at 1-800-875-1093.

Metals

Most ferrous and non-ferrous metals, as well as a variety of other materials, can be etched by Precision Photo-Fab Inc.

The following list represents the most commonly etched metals.

Dimensional and Tolerance Capabilities

Minimum dimensions and tolerances are primarily determined by material type and thickness. Since the the etchant will dissolve the metal laterally and vertically (thickness of material) at the same rate, features which are to be etched through the metal should equal material thickness. Features which are to be half-etched into the metal should equal half-material thickness.

Line Widths

Please specify on your print if the width of the metal at the surface is critical. Due to the cusp/bevel (please see below), a line which measures .016" wide may only have a .010'' surface width.

Inside Corners and Metal Thickness

The smallest corner radius should be directly proportional to the thickness of the metal. For example, for metal thickness of .002", the corner radius should be .002"; however, if you need a smaller radius, it may be possible, based on other design considerations.

Outside Corners and Metal Thickness

Outside corners tend to etch more sharply than inside corners. Therefore, radii of less than metal thickness are possible. As a guideline, outside radii should be at least 75% metal thickness.

Corner Radii

PPF's photo-chemical machining process tends to round off corners. This is more pronounced on thicker material. If you need a square corner, Precision Photo-Fab has techniques to accomplish this as well. For a sharp corner, simple changes to CAD designs can be incorporated!

Cusp or Bevel and Metal Thickness

The etchant dissolves metal laterally as well as vertically. This results in a condition for a edge condition known as a cusp or a bevel. The relationship of a cusp to metal thickness depends on one-sided or two-sided etching.

One-sided etching:

The cusp will equal .4thickness (t)

Two-sided etching:

The cusp will equal .2t

The cusp (or bevel) is more pronounced in heavier materials. The cusp (or bevel) can be controlled through our process, or can in most cases, be eliminated by a secondary operation.

Tabs

Parts can be manufactured & shipped in one of three ways...

	Tabbed in sheet form - Parts are "tabbed" (connected) much like a model airplane kit. Tabs can be either recessed or protruding, depending on your edge finish requirements. Tabs can save you money by minimizing handling, therefore reducing manufacturing costs.
	Broken out - If parts are manufactured tabbed in sheets, they can be "broken out" in-house prior to shipping. Note, this picture depicts "protruding" tabs on the left, top, and bottom of the part. The right side of the part shows two "recessed" areas where the tabs were removed.
	Etched clean - Acid etches entirely around the perimeter of the part. This eliminates the possibility of burrs from tab removal.

Tolerances

While there are no absolute design rules for etching tolerances, our standard offering is +/- 10% material thickness. This can be tightened based on your needs, and the design characteristics of the part.