PCBs go down to the wire

The market demands ever greater miniaturisation in printed circuit boards - as well as an increasing use of flexible circuitry - so the need for improved methods of producing high-resolution PCBs is becoming more important.

By controlling the etching process, inventors from Britain's Oxford University can ensure reliable production of boards with conductors down to 10 µm wide.

Today's PCBs feature conductors of 150 µm but there is a growing requirement for conductors to be 25 µm and even 10 µm.

With present manufacturing techniques it is not possible to attain the required precision - especially where the spacing between the conductors varies.

The etching rate is highest where the conductors are furthest apart. This leads to over-etching and subsequent under-cutting of the very fine conductors in these areas.

The resulting PCB has copper conductors of variable width and its performance is, therefore, 'not optimum'.

By controlling the etch conditions and the area to be etched, the inventors claim to have reduced over-etching to an acceptable level and under-cutting has been virtually eliminated. The spaces between the conductors are now all uniform width but with more redundant copper remaining on the PCB. The etching has been confined to narrow tracks.