A lab-on-a-chip, designed to keep alive a microscopic worm in space. A PCB for advanced automation illumination. A surgeon’s orthopaedic power tools. What these technologies have in common is that they all relied on ES Precision’s newest laser technology – a q-switched, frequency-tripled Nd:YVO4 (‘Vanadate’) laser, operating in the UV part of the spectrum, with an output at 355nm.

ES has established itself as a leading UK provider of laser processing in the 3 years since it was founded by Directors Tim Millard and Andy May in 2017. The award-winning company has consistently reinvested its profits to expand its service offering to UK manufacturing. Key to its success in fine laser processing is the wide range of lasers available – 5 distinct types across its 8 laser workstations. The laser wavelengths output, from IR to near-IR to UV mean that virtually any material, from the exotic to the mundane can be surface modified. Typically this is a mark by surface transformation (oxidation, ablation, foaming, annealing ….) or, for very thin materials, clean cutting. ES wanted to be able to create attractive, functional marks on any material that our customers use. We handle all metals, sometimes with coatings such as anodising or paint, from aluminium to platinum. There is a wide range of ceramics too, but it is organic materials which probably present the most diversity; there is such a wide range of plastics and rubbers and each might appear in varying formulations, incorporating fire-retardants, glass fills or a multitude of pigments.Some plastics are formulated by the masterbatch supplier with specific additives designed to enhance laser marking, but this can be expensive and many moulding companies cannot dictate the formulation they use – that will be decided by their customer. So from time to time ES used to receive polymer components which could not be marked satisfactorily. The way that lasers interact with materials is primarily driven by their wavelength; organic materials tend to absorb well at the UV and far IR ends of the spectrum, but sometimes not so well in between. In seeking to meet the demands of medical device customers for permanent, high contrast marks, without reformulating the material, ES began to test sources of other wavelengths. Whilst CO2 lasers are also used for such substances, treatment with their 10600nm output tends to be more thermal than with UV’s 355nm. The UV laser can avoid burning, charring and melt-back.Laser marking is usually cleanest if the material is surface-absorbing and transmission spectra of many polymers show an increased absorption (decreased transmission) below about 400nm wavelength (see Fig. 1) and this is often enhanced if additives are incorporated.

Fig 1. Transmission of Polycarbonate Plummets at around 400nm (source: Wikipedia).

ES’s UV laser has therefore established a niche in processing materials hitherto thought to be unsuited to laser marking. There are also applications where the UV results outshine cruder marks from IR lasers in terms of contrast, resolution and crispness (edge quality). Aside from better surface absorption, mark quality also benefits from the smaller focal spot size and reduced thermal damage achieved when using the shorter wavelength.

So why don’t all laser subcontractors offer a service for laser marking using UV lasers? The answer is that they are no panacea – most metals and ceramics absorb better at near IR – so it is necessary to operate a suite of laser types. The other argument is economic – UV laser markers can be twice as expensive as IR ones and typically offer a fraction of the average power. Shorter wavelength lasers cost more; ES operates laser markers delivering 200W of CO2 (10600nm) average power and 100W of Nd:YAG (1060nm), but only 3W of UV. This modest power means that marking throughput can be slower at the short wavelength, so commercial returns would be reduced for routine jobs if a laser with a fraction of the power at twice the capital cost were used.

ES’s UV laser has nonetheless paid for itself by opening up valuable niche jobs. Here’s some more detail on those three applications mentioned at the start of the article:-

Worms in Space

A Cranfield University team of students has been selected for a project with the Swedish National Space Agency, German Aerospace Centre, and European Space Agency which seeks to investigate the effect on a complex life form of an extended period in the stratosphere. They chose the C. Elegans nematode – a 1mm worm, many of whose genes have functional counterparts in humans. The task will be to keep it alive in a compact environment in preparation to be launched as a satellite, beyond a low earth orbit. The team have designed a ‘bioCubeSat’ which incorporates a microfluidic assembly which can be pressurised and feed nutrients and drugs to the nematode in orbit. Such fluid assemblies tend to be made by laminating layers of polymers, often laser-cut to create functional channels linking feeding and sensors for monitoring the experiment. ES used the UV laser to create complex profiles in thin (a few microns) polycarbonate membrane (see figure 2) with minimal thermal damage.

Figure 2. Laser Cut Membrane in Polycarbonate for Microfluidic Assembly.

Unique ID Matrix identification on PCB

Bare board supplier PCB Partners and their end customer Esprit Electronics required their white solder resist on the boards to be permanently marked with tracking information in the form of a tiny ID Matrix code (see figure 3). Each code encrypts a series of alphanumerics incorporating a unique tracking code for optimal quality assurance for the automation illumination that they control. The only laser that would produce a reliably readable mark with sufficient contrast was the UV marker.

Figure 3. Unique ID Matrix Codes marked on PCB resist.

Permanent, Clean Traceability for the Operating Theatre

De Soutter Medical makes powered tools for use in orthopaedic and trauma surgery. Medical technology is a field which always demands traceability and cleanliness so components must be cleanly and permanently marked with product numbers and regulatory graphics. The cord sets which link instruments to controllers and power supplies tend to be made using a flexible silicone rubber which can be tough to get an excellent mark on with traditional lasers, but the UV laser produced a very fine, dark print. (See figure 4).

Figure 4. Essential Regulatory Graphics and a unique ID Matrix on a Medical Cord Set.

Looking to the future, forward-thinking service providers will be seeking to continue to invest to be able to produce better, faster marks on all manner of products. Some materials present laser processing challenges owing to their conductivity (pure gold, graphene), others due to their transparency (quartz, some glasses) and yet others due to their fragility (bio materials such as collagen, thin ones such as graphene). Deeper UV sources (e.g. excimer) provide some answers as will ultrashort pulse lasers such as femtosecond lasers. As always, the cost-benefit for such big-ticket items need to stack up for small, high tech laser processing businesses.