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Flex & Rigid-Flex Circuits

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Outlining Flex Circuits & Integral Fingers Manufacturing Processes

Outlining

Flex Panel
Individual parts can be de-panelized using several different methods. Photo on right shows a panel containing flex circuits.

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.

Open Windows on Flex Circuit
By using our unique polyimide etching technology, Tech-Etch can supply circuits with conductors suspended across an open window in the polyimide film or cantilevered from the edge of the circuit. For circuits made with beryllium copper, cantilevered leads can be formed and used as integral contacts.

CO2 or UV-YAG lasers can be used to outline flex circuits. Advantages include minimal tooling, short lead-time and intricate outlining.

Integral Fingers

Soldered Fingers
Sometimes it is necessary to create custom solderable finger terminations. Tech-Etch can provide two different cost effective solutions.

1. Soldered on Fingers
Tech-Etch can solder an array of .010-.020" thick etched brass fingers of any shape or form to the termination area of the flex. A protective polyimide coverlay is added over a high temperature solder joint to prevent movement in the event of reflow during assembly. Advantages: The main body of the flex can be of any construction, retaining required flexing characteristics.

Contoured Flex
2. Contoured Flex Circuits
By capitalizing on our experience with thick metal etching, Tech-Etch can supply Contoured Circuits with integral contact fingers up to .010" thick. The remaining metal in other areas of the circuit is etched down to approximately .003" thick. Particularly useful for applications where current carrying capacity is a requirement, this process also supports raised solder pads above the cover layer or circuits manufactured on material as thick as .020".
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