Capabilities
Technologies - Description of Manufacturing Processes
Circuit Layer Generation
Circuit layer conductors can be created using an additive or subtractive manufacturing process. The choice between additive or subtractive process is generally left to the discretion of the manufacturer.
A. Additive – The creation of additive circuitry starts with very thin (5 micron or thinner) copper layers on one or both sides of polyimide film. Resist is first coated on the surface of the copper, and then it is imaged and developed. What remains are channels in the resist in which copper will be plated. This plated copper becomes the traces, pads and other conductive regions of the circuit. Next the resist is removed and the background 5 micron copper is etched away to isolate the newly created copper features. There are more processing steps in creating additive circuitry than subtractive circuitry, making it more costly. However, additive processing provides resolution of .003" wide (or smaller) leads and a rectangular lead cross section.
B. Subtractive – Subtractive circuitry starts with copper bonded to one or both sides of polyimide film. The copper thickness is the desired final thickness. Resist is applied to the copper surface and then the resist is exposed and developed. What remains are channels or openings in the resist, through which the copper can be attacked using an etchant. After etching, the resist is removed and the finished circuitry remains.
Drilling
Flexible circuits may be pre-drilled to create plated through hole interconnections or simple mounting holes. Holes smaller than .008" will be laser drilled.
Plating
With over 30,000 square feet of our facility dedicated to finishing, Tech-Etch can provide both conventional and exotic surface finishes to flex circuits. Consult with Engineering if you have special finishing requirements.
| Finish |
Min Thickness (in.) |
Max Thickness (in.) |
Tolerance |
| Hard Gold |
.000010 |
.000200 |
Min. |
| Soft Gold |
.000010 |
.000200 |
Min. |
| Tin |
.000050 |
.000200 |
+/- 25% |
| Tin-lead |
.000050 |
.000500 |
+/- 25% |
| Cu-Tin |
- |
- |
- |
| Nickel |
.000050 |
.000200 |
+/- 40% |
| Hot Air Level |
N/A |
N/A |
N/A |
Outlining
Individual parts can be de-panelized using several different methods.
Steel rule dies are the most common and economical means of de-panelizing flex. High quality plywood is laser cut in the pattern to be outlined. Steel blades and spring-loaded datum pins are inserted into the laser cut path. The flex panel is registered to the blades using the datum pins and a flat platen is brought into contact with the blades, cutting the outline. Advantages of steel rule dies include low initial cost, fast delivery and the ability to excise many parts in one strike.
Class A hardtools are used for tight tolerance requirements. They typically consist of a punch and die mounted in a precision die set. Dies can be built to cut single or multiple parts. Advantages of hardtools include tight tolerances, process consistency and long life.
Polyimide etch – We commonly use polyimide (and adhesive) etch processes to create access to conductors and create part outlines. Similar to metal etching, resist is imaged and exposed to create an etching mask and the polyimide is chemically attacked. When defining the outline, small tie tabs are left behind to suspend the part in the panel. These tie-tabs are usually cut by hand during final inspection of the product. Advantages of using polyimide etch to outline parts include cost efficient sheet processing, quick lead-time and intricate outlining at no additional cost.
CO2 or UV-YAG lasers can be used to outline flex circuits. Advantages include minimal tooling, short lead-time and intricate outlining.
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