Photo Chemical Machining Advantages
The PCM process is perfect for simple or complex thin-metal components of one to one million parts and which is very economical option for R&D or prototype phase of a project when quick turnaround is vital. PCM can be utilized to etch through metal thicknesses between .0005" to .060" and between .060" to .250" for depth etching on the types of metals listed below.
Types of metals
Stainless Steel, Spring Steel, Electrical Steel, Copper, Beryllium Copper, Brass, Aluminum, Bronze, Phosphor Bronze, Nickel 201, Nickel Alloys, Nickel Silver
Dimensions and tolerances
In the PCM process there are certain pointers and techniques that a designer should understand regarding the capabilities of the etching process. The following are basic guidelines for designing photo chemical machined parts.
Key factors in design include metal thickness, metal type and size of part features being etched.
Relationship of hole size to metal thickness
As a general rule, the diameter of a hole cannot be less than 125% of the metal thickness. Diameters of 110% of metal thickness on metals up to .010 thick can be achieved.
Remaining surface area in a large field of slots or holes also has certain limitations as to how small the metal land between holes can be. Again it depends on material thickness. If the material is less than .005" thick the space between holes must be at least the metal thickness. If the material is over .005" thick, the spaces between holes must be at least 125% times the material thickness.
Relationship of inside corners to metal thickness is directly proportional to the thickness of the metal. Smallest inside corner radii equal to metal thick can be achieved. Example: corner radius would be .002" for piece of metal .002" thick.
Relationship of outside corners to metal thickness considered to be at least 66% of metal thickness. The outside corners tend to etch more sharply than the inside; therefore radii of less than metal thickness are obtainable.
Relationship of bevel to metal thickness
When etching from one side of a sheet of metal the etchant attacks the material laterally as well as vertically. The result is an edge condition known as "bevel." Typically this bevel will be 40% of metal thickness. When the material is being etched from both sides (equally) the bevel is reduced to typically 10% of metal thickness.
Tolerances
Tolerances achievable with PCM depend on the material type, thickness, size of panel, equipment used and yield required. As a general rule of thumb a tolerance of +/- 15% of metal thickness can be achieved. Tolerances of +/- 10% of metal thickness can be achieved through photo tool modifications.
The above specifications have been kept very general – for more specific dimension and tolerance information as well as design criteria, please contact NW Etch. Depending on the alloy and the components you wish to produce we can specify the tolerances that are possible.
NW Etch has its own in-house CAD department that can generate tooling from DXF and other data files as well as from dimensioned drawing. Tooling is kept very reasonably priced because the same photo tool is used until revisions are needed.
Typical products
RFI/EMI Shielding, Screens, Filters, Lead Frames, Encoder Disks, Buss Bar, Flat Springs, Heat Sinks, Drive Bands, Electrical Contacts, Ribbon Shields, Laminates, Backplates, Shields, EMP grids, Signage, Plaques.
TYPICAL ETCHED PART CONSIDERATIONS
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