Resolution Benefit
Industrial standards for high density circuit production compare additive plating techniques against traditional subtractive methods to determine the most effective route for fine line geometry. The semi additive process, commonly known as sap, begins with a very thin seed layer on the substrate. This is followed by the application of a photoresist and the electroplating of the traces to their final thickness.
Build Method
Narrow traces and spaces are much easier to achieve with this method than with traditional subtractive etching. Because the traces are built up from the seed layer, they have nearly vertical sidewalls, which improves the signal integrity of the circuit. Once the plating is complete, the resist is removed and a quick flash etch is used to eliminate the remaining thin seed layer.
This sequence prevents the undercutting of the traces that typically occurs when thick copper is etched away. Modern smartphones and high density electronics rely on this technology to pack more functionality into a smaller area.
Production Cost
Manufacturing costs are higher than standard processes but are offset by the ability to create features that are impossible to make with other techniques. This sap method remains the primary choice for advanced high density interconnect designs.
