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Specs and Tolerances for Photochemical Etching

Photo Etching Specifications

The dimensional capabilities of the photo chemical etching process are always driven by metal thickness.

  • Drawing block tolerances of +/-.005" are achievable on metals up to .032" thick
  • Minimum dimensional tolerances of +/-.001" are achievable on metals up to .005" thick.
  • For metal over .005" thick, minimum dimensional tolerances will be +/- 15% of metal thickness
  • Minimum hole/slot dimension must be at least 110% of metal thickness
  • Minimum radius to be not less than 70% of metal thickness
  • Partial etch depth tolerance to be +/-.001"
  • Location tolerances will be within +/-.001" of drawing nominal

Tolerances have a direct impact on sheet sizes. 

Tighter tolerances mean smaller sheets. Smaller sheets mean higher costs.

The table below illustrates the impact of tolerances and sheet sizes on photo-etching costs.  The premise is based on a 1-inch part on .010" thick metal and does not include metal cost.  The major variable in this example is the labor.  In chemical etching, the unit of labor is the sheet.  The amount of labor per sheet varies very little with the size of the sheet.  Therefore, the number of sheets becomes a decisive factor in calculating costs.

Sheet Size

12 x 12

12 x 18

12 x 24

18 x 24

Min Tolerance

+/-.002

+/-.0025

+/-.003

+/-.004

500

.59

.43

.41

.38

1000

.56

.39

.36

.31

2500

.52

.38

.29

.25

5000

.45

.33

.29

.23

10000

.42

.31

.27

.22

25000

.40

.30

.26

.21

50000

.39

.29

.26

.20

Sheets/ 1k Parts

15

9

7

5


 Design Guide for Photochemical Etching

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