All About Flex: Plating Process Options for Flexible Circuits


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The first steps of via formation and seed plating are the same as pattern plating.

 Fig9.jpg

After the seed coating, photoresist is imaged so it exposes only the pads that capture the via.

Fig10.jpg 

Copper is electroplated in the vias and pad areas as shown below.

Fig11.jpg 

The resist is stripped and the panel goes through a second image resist operation.

Fig12.jpg

The panel then goes through an etch-strip operation—the image below shows the copper etched away. The resist is “tented” over the via to protect the through-holes from etchant.

Fig13.jpg 

The image below shows the resist stripped away leaving the final circuit pattern.

Fig14.jpg 

Plating, imaging and etching are basic operations used in flexible circuit and PCB fabrication. The sequence and combination of these operations can result in significantly different circuit configurations. Changing the order of processes can result in different plating thickness profiles. These operations are also dependent on each other for attaining desired yields. The interactions among various process steps, and achieving desired plating results, is understandably complex. We highly recommend involvement of a supplier for technical questions about specific applications.

Dave Becker is the V.P. of sales and marketing at All Flex Flexible Circuits and Heaters. To contact Becker, or read past columns, click here.

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