Inkjet printing to build circuit boards

A method of mass producing electronic circuit boards using inkjet printing technology is being developed in the UK.

Production runs of 10,000 to hundreds of thousands of units per year could be possible, according to scientists at UMIST. The inkjet process involved is said to generate less waste and be quicker than similar methods used for prototyping.

The technology will initially be used to build boards of a ceramic material to improve heat sink capabilities. Applications include high-powered radar and mobile phones and laptops.

Prof Brian Derby is leading the research at UMIST’s materials science centre. His team is part of an Anglo-American consortium. ‘We are working with a UK company that manufactures consumer electronics. Our method is direct printing – we only print down what we want.’

He said the technique is an advance on so-called indirect printing methods that are used for making prototypes. This is where a large amount of a particulate material is laid down and adhesive is sprayed on to bind only what is needed, producing a lot of waste.

‘Another advantage with our method is that it takes far less time to dry. Our particle containing ink takes no longer than a normal printer,’ he said.

Derby’s team has an inkjet printer that can print four different materials for the circuit board’s construction. Those materials are silver for the conductor, a ceramic, a resistor and a piezoelectric, all in particulate form. It can receive its data for the ‘printing’ instructions from a normal CAD file.

Once downloaded the printer will then use its four print ‘heads’ to deliver the material within an ink or liquid polymer. To cope with this the print heads aremodified to deal with this much thicker, higher viscosity, liquid.

Like a normal printer it then processes the ‘paper’, which will go back and forth as layer after layer is built up. The ‘paper’ used in these printers can be a plastic film or a wax.

As the paper goes back and forth the printer can build so-called ‘vias’ into the multiple layers. These are silver-based connections between layers and could be used to link microchips fitted on both sides of the circuit board.

The end result is a board that consists of a ceramic or aluminium oxide for the improved heat absorption abilities.

Derby also said that the circuit board need not be flat. The process can also ‘print’ on to curved boards.

Wax can also be used with the process to build actual electrical components such as a piezoelectic actuator.

After the silver and ceramic is printed on to the wax, the wax itself can be dissolved to leave a free-standing structure.

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