Laser materials processing developments in electronics manufacturing

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Productronica exhibitors shared some of the latest trends in electronics manufacturing with Abigail Williams

Laser depaneling systems such as this achieve higher output by higher effective cutting speed and cutting quality. (Image: LPKF)

This November, laser materials processing firms from around the globe were among those who gathered for Productronica – billed as 'the world’s leading trade fair for electronics development and production’.

To tie in with the event, some of this years’ exhibitors provided Laser Systems Europe with insight into a range of complex and interlinked trends in laser processing for electronics production.

The annual Productronica trade fair is the largest international event for the electronics production industry – and the only event of its kind to cover the entire value chain.

This years’ gathering – held between 16-19 November at Messe München in Germany – brought together more than 1,500 exhibitors from 45 countries, and more than 43,000 trade visitors from 82 countries.

In addition to a wide-ranging programme focusing on subjects from sustainable electronics supply chains and smart welding, to artificial intelligence and additive manufacturing at the nanoscale, the event also gave exhibitors and delegates the opportunity to discuss some of the current and emerging trends facing the sector.

Price-performance ratio

According to Patrick Stockbrügger, product manager at German firm LPKF Laser & Electronics, recent trends include demands for better price-performance ratio – and thus cost-effectiveness – offered by lasers to be brought to a broader field of applications in electronics production, as well as demands for a faster time-to-market.

‘Miniaturisation also remains a global trend for all kinds of electronics parts, from standard PCBs to chips,’ he said. ‘It is still possible to achieve this further miniaturisation through laser technology because it allows design freedom and a minimum distance between mounted components and tools.’

Stockbrügger also reported an increase in demand for ceramic and metal core circuit boards, mainly as a result of the increasing demands, requirements and production volumes of the growing electromobility sector. In his view, this development is of particular importance because these materials generally require more laser power to process.

Another trend is the demand for ‘technical cleanliness,’ which Stockbrügger explained plays a decisive role in the long-term stability of PCBs. This makes it a particular requirement for safety-relevant automotive and medical applications. LPKF addresses this issue with its laser-based innovation, CleanCut, which it says enables dust- and carbonisation-free processing at high cutting speeds.

 Example for a clean and residue-free FR4 cutting edge produced with the LPKF CleanCut technology. (Image: LPKF)

Advanced IC packaging

Cordula Krause-Widjaja, PR manager at LPKF, observed that advanced integrated circuit (IC) packaging plays an ever-increasing role in satisfying the need for more and more computing and signal processing power – and that new materials are always in focus in the research and development sector.

‘Thermoset encapsulation compounds are now the carrier of additional metal layers in an IC package or module, thus realising a greater functionality of the IC on the same footprint,’ she said. ‘Whether rigid, rigid-flex or flex materials, laser processes must be adapted to specific material requirements. Therefore, a variety of different laser systems for prototyping is necessary.’

Krause-Widjaja has consequently witnessed ‘a great increase in laser processing’ for advanced IC packaging – largely due to the fact that traditional back-end tools cannot keep up with the required pace of IC package improvement.

‘Our patented Laser Direct Structuring (LDS) and Active Mould Packaging (AMP) technologies, and related laser tools are ideal for this selective and direct manufacturing of conductors and vias,’ she said. ‘Because LDS and AMP are truly additive technologies, the environmental, social and governance impact of IC packaging can be reduced.’ She remarked that sustainability is becoming increasingly important in electronics manufacturing: ‘New ways of thinking, designing and manufacturing will be key to sustaining a habitable biosphere. Laser processing will play a crucial role in that process, as it has the power to replace traditional and rather resource-intensive manufacturing technologies.’

Technically clean-cut edges ensure high PCB edge quality, and allow – with a full-perimeter cutting via laser technology – for significant material savings, compared to conventional mechanical depaneling processes. (Image: LPKF)

In response to the varied demands of electronics manufacturing, Stockbrügger revealed that LPKF focuses on new laser sources with an improved price-performance ratio – mainly using pulsed lasers, as well as ultra-short-pulsed laser systems.

When it comes to new laser processing applications for electronics production, Stockbrügger reported an increase in those involving metal core PCBs – largely because of the necessity of a fast heat dissipation. He added: ‘Laser systems nowadays are economically attractive due to increased power. The processing of more than 1.6mm with a pulsed laser is possible – and the wavelength to be chosen depends on the requirements, design and product mix.’

On display

At this years’ Productronica trade fair, LPKF exhibited a range of laser processing technologies that included new system variants of its CuttingMaster series of laser depaneling machines.

The new variants are equipped with new, optimised laser sources,’ said Stockbrügger. ‘They also feature more power and an improved price-performance ratio – including an optimised total cost of ownership.’

Krause-Widjaja revealed that the company also presented the first system to feature LPKF’s ‘disruptive’ faster beam guidance technology, ‘Tensor’, at the show, as well as its product portfolio for inhouse PCB prototyping. ‘LPKF also presented its WeLDS technology – which combines 3D moulded interconnect devices with laser plastic welding,’ she added. ‘Conductive traces can be produced on the surfaces of injection- moulded parts. The required cover is then welded onto the housing using LPKF’s laser plastic welding technology.'

Trim and proper

Elsewhere, Ludwig Schuhmann, sales manager at German system supplier, GS Electronic, observed that the main customer drivers are tighter accuracy specifications driven by the shrinking dimensions of electronic components and circuits, and the need to offer customised solutions. Although logistical problems related to the covid pandemic meant that GS Electronic could not have a laser trimming system on display at this years’ Productronica event, Schuhmann confirmed that the company did have posters, flyers and laser trimming customer service experts at its booth.

Foil cutting

Dr Gernot Schrems, head of product management at Austrian company, Just Laser – which manufactures laser engravers, cutters and markers – reported a trend for cutting thin metallic foils in electronics manufacturing, including single foils or compounds with metal and polymer. ‘These foils can be cut up to at least 0.5mm thickness using a super-pulsed CO2 laser. A standard 400W sealed-off, RF- excited CO2 laser delivers 500-600W of peak power. This is not sufficient for metallic foils. Using a super-pulsed laser with a peak power above 1,000W leads to a nice quality cut with high throughput,’ he said.

According to Schrems, the capabilities of CO2 lasers are far from being ‘maxed out’, with recent developments in power electronics yielding high emitted power from antennas into laser resonators.

Micro-welded hybrid PCBs could lead to lighter electric vehicles

Scientists have produced hybrid printed circuit boards (PCBs) using laser micro- welding that are both more versatile and 20-times cheaper than conventional power electronics made of ceramics.

The new PCBs could significantly reduce the installation space required for power electronics and thus, the overall weight of electric vehicles, resulting in longer driving range and lower CO2 emissions.

They are also an extremely important development due to the microchip shortage, according to scientists.

To produce the PCBs, scientists developed a new manufacturing process that makes it possible to use low-cost FR4 circuit board substrates in power electronics, for example in electric motors.

Woo-Sik Chung, from the Micro Joining Group at Fraunhofer ILT, explained: ‘Imagine two copper blocks with the same surface area, but different thicknesses in cross section. The thicker the block, the greater the current flow. Where the most current is needed, we reinforce the circuit board. Where little current needs to flow through, we save on material.’

A hybrid circuit board produced as part of the BMWi-funded CLAPE project. It combines several functions in one component. (Image: Fraunhofer ILT)

With standardised manufacturing processes, it was previously very costly to selectively thicken individual areas so that a welded connection could be applied. In the CLAPE project, however, (Innovative Cold-spray deposition and Laser joining for PCB-based Power Electronics), experts from Fraunhofer ILT, ILFA GmbH and Ouest Coating have successfully tackled this challenge over the past three years.

‘Until now, the rule was: you use a PCB with a thin metallisation layer, or one with a thick layer, depending on the application,’ Chung explained. A current transformer to charge batteries in electric cars, for example, requires a great deal of current within a short period of time for the charging process, whereas only a few milliamperes are needed to transmit a current signal to an LED light. ‘Our new manufacturing process enables us to realise both simultaneously on just one circuit board: signal and current transmission,’ said Chung.

The researchers achieved this using specially adapted circuit boards that were thickened selectively by cold gas spraying. Conductor tracks of different thicknesses could then be micro-welded to the printed circuit board using lasers.

Optimised design

Thanks to their specific structure for signal and current transmission, the resulting hybrid PCBs not only require less space, but also distribute the energy much more efficiently.

‘In the future, our hybrid PCBs could combine several functions within one component,’ said Chung. ‘If the [manufacturing] process becomes established in practice, both the installation space for power electronics and the overall weight of electric cars could be significantly reduced, resulting in both a longer range and lower CO2 emissions in the long term. This is also an extremely important finding as the resources to manufacture chips for power electronics are in short supply.’

With the project only recently being completed, the technology is not yet ready for the market, and some adjustments still need to be made before it can be used in practice. ‘But we’ve already been able to show there are promising technological alternatives to the status quo,’ said Chung.

The next research goal is to optimise how selective the cold gas spray process works and further reduce costs. ‘Here we still have room for improvement. But this also shows us what great potential there is in the technology once it can be used in a commercially viable way,’ Chung concluded.

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