Flat Parts Photo Etching Design Guide
Tech-Etch specializes in the manufacture of light gauge metal parts. Photo etching produces intricate components with exacting tolerances that are impossible to duplicate by other processes.
All dimensions, tolerances and configurations are functions of the thickness of the material being photo etched and should be considered during the design process. The following guide gives practical limitations for slots, spaces, holes and construction dimensions with relation to metal thickness for photo chemical milling.
See Figures 1 and 2 below for a pictoral representation of the features referenced.
In many cases it may be possible to exceed these photo etching limitations, but with a reduction in yield percentage. Consult the factory for design assistance when these situations occur.
DIMENSIONSHOLES / SLOTSGenerally, the diameter of a hole or the width of a slot cannot be less than the metal thickness. This relationship varies as the metal thickness changes. A more exact relationship is illustrated in Table 1.
INSIDE CORNER RADIUS The smallest inside corner radius is directly proportional to the metal thickness. Consult the factory if a smaller or sharp radius is required. OUTSIDE CORNER RADIUS The outside corner radius will be at least .75 of the material thickness. FINGERS / WEBS Generally, the width of a finger or web cannot be less than the metal thickness. This relationship varies as the metal thickness changes. A more exact relationship is illustrated in Table 2.
TOLERANCESCENTER TO CENTERGenerally, the tolerances are a result of the stability of the photo tooling material. Table 3 illustrates the practical tolerances attainable from industry standard Mylar tooling. Consult the factory for information on alternate tooling materials.
PHOTO ETCHED DIMENSIONS Generally, a tolerance of ± 15% of the material thickness is practical. A more exact relationship is illustrated in Table 4.
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