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Is laser sintering the future of PCBs?

Published Wednesday 3rd October, 2018

The electronics industry never stands still and is always looking for innovations that allow us to produce faster, stronger and more powerful circuit boards, which is why laser sintering has created such a buzz.

Sintering itself is a naturally occurring process that's been harnessed in many different industries but has previously been considered too expensive an alternative for printed circuit boards. However, a new study out of South Korea may have changed that, but first let’s take a quick look at what sintering and laser sintering are...

Sintering

Essentially, sintering is a process that fuses particles together to form a solid mass by diffusing the atoms in the material across the particle borders. Observing it occurring naturally, metallurgists soon recognised the advantages when working with materials with very high melting points, because sintering happens at a temperature below the melting or liquefaction point.

Laser sintering simply uses photons (light) as the heat source for this process: perfect for electronics because a laser can be controlled and directed all the way down to a micrometre level.

Laser sintering in electronics

Printed circuit board (PCB) manufacturers are always attempting to push the boundaries of the possible and make our boards smaller, stronger, faster, more reliable and more adaptable – and laser sintering has always offered potential in that regard.

A recent study by Kye-Si Kwon of Soonchunhyang University in South Korea is really exciting us because his team has been building on previous work undertaken with silver nanoparticle ink – metallic ink has a much lower melting point than bulk metal, making it ideal for tiny applications like micro boards – by using copper oxide as a low-cost alternative.

Laser sintering can turn copper oxide nanoparticle ink into usable copper at incredibly low temperatures of between 150 - 500°C (bulk copper melts at 1,083°C), making it a potentially cost-effective solution. Interestingly, Kwon discovered that green light in the 500 - 800 nm range is the most effective - a fact that, to his knowledge, hasn't been reported before.

Discovery in action

The nanoparticle ink was spin-coated onto glass at two speeds in order to create two different thicknesses prior to sintering. Copper oxide film production and bubbling were dealt with by pre-baking the material to burn off as much solvent as possible at temperatures just below 200°C - ideal, according to the team's tests.

Figuring out the optimum laser power and scanning speed during the sintering process to obtain the most effective conductivity of the copper was their next task, and they discovered that a speed of between 10 - 100 m/s and a power level of between 0.3 and 0.5 watts was perfect - further proof of the efficiency of the process.

Of course, however fascinating this is, the results are ultimately what matters, and Kwon's team report up to a 74% reduction in film thickness post-sintering – an outcome that really does offer exciting prospects for advances in electronics.

As with every quantum leap in electronics technology, Daletech is excited to see where this work goes, and we’ll be watching Kwon's future work on the substrate effect on laser sintering to see if it can take PCB design even further into the future.

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