Abstract
In the preparation of copper interconnects in the conductor pattern of a printed circuit board (PCB), wet etching processes are commonly adopted for creating patterns of high-density interconnects. Currently available techniques of immersion and spray etching could lead to poorly shaped wires due to complex flow fields or the disturbing puddling effect. A modified technique of arrayed jet-stream etching was developed in this work, aiming at producing well-defined copper interconnects on a PCB in a significantly shorter time. The results were appealing in that copper interconnects of 35/140 μm (thickness/width) exhibiting etching factors of greater than 6 were obtained in 20 s, much better than the conventional ones with etching factors of 3 to 5 and etching times of at least 2 min. In addition, uniformly etched copper interconnects with less than 20 μm undercuts were observed on one etching line. One additional point to note is that no banking agents or inhibitors as commonly seen in conventional etching techniques were needed in this new processing method. © 2008 Springer Science+Business Media B.V.