Company insight
Micro-optics for sensors and diagnostic applications
Accumold is the only company that has been continuously dedicated to micro moulding for over 30 years. It remains committed to serving high-tech industries that require high-volume, small, complex micro injection moulded parts with high quality and fast turn-around. Aaron Johnson, vice-president of marketing and customer strategy at Accumold, discusses manufacturing micro-optics for medical sensors and diagnostic applications.
F
rom a moulding perspective, only the most experienced, expert micro moulding companies can successfully achieve the exacting tolerances that micro-optic components demand. For Accumold, micro-optics can range from 20µm to 1mm in size, and are required for an array of applications, such as sensors, medical diagnostics, DataCom applications, wearables (which include fitness type devices and medical diagnostic devices), and emerging technologies such as augmented reality glasses and contact lenses.
however, and necessitates partnership with a truly vertically integrated micro moulding company (bringing together tooling, micro moulding, validation, and automated assembly), and one that is on top of its game when it comes to design for micro moulding (DfMM).
The overall micro-optic manufacturing sector is characterised by high costs and high risks, with few qualified and reliable micro moulders available that can manufacture to the level of accuracy required, in the timeframe required, and at a sensible and competitive cost.
“The demands that the production of micro-optics places on the micro moulding process itself has led Accumold to use its own micro moulding machines, as ‘off the shelf’ options struggle to come up to scratch.”
The demands that the production of micro-optics places on the micro moulding process itself has led Accumold to use its own micro moulding machines, as ‘off the shelf’ options struggle to come up to scratch. The micro moulding process used must be able to attain the dimensional requirements for micro-optics parts, and also achieve the absolute flatness required (the surface relief feature depth of diffractive optical elements (DOEs) being in the range of a few hundred nanometres to a few micrometres, and refractive micro lens arrays less than 100µm).
Go beyond for success
The skills involved in achieving success in micro-optics applications extend beyond the actual moulding process itself,
The micro moulder necessities Of vital concern when choosing a qualified partner is an understanding of the necessity for expert testing and quality assurance processes that are unique to micro-optic fabrication. In-house metrology tools need to be available that are able to validate and assess the unique lens profile and surface finish requirements that characterise micro-optics parts and components. Micro moulders will routinely be required to assist in the design, tooling, and manufacture of micro-optic devices, such as 250µm fibre-optic lenses, parallel array products, demux devices, and diffractive lenses. They may also need experience of moulding attenuated resins and adding IR, anti-reflective (AR), and reflective coatings on to plastics. The
Medical Device Developments /
www.nsmedicaldevices.com
demands associated with running micro- sized optical couplers, integrating lenses into housings, replicating lens profiles within a quarter wave, and lens surface finishes within 50Å requires that micro moulders have a dedicated tooling expert on staff to advise on and optimise DfMM and tooling for any OEM light transmission requirements.
Hands-free application Once moulded, it is important to use a fully automated and hands-free assembly process – overcoming the basic logistical issues surrounding the removal of such tiny and delicate components while also ensuring that orientation is maintained, and parts are not contaminated by touching. In micro-optics applications, complex assembly operations can often be avoided through the use of over- moulding, and a micro moulder with the understanding of what is possible in the moulding process and has the skills necessary to over mould is often vital. The fewer assembly steps the better, but when post-production assembly is required, and if the volumes are high enough, dedicated moulding and assembly work cells can be built to do the assembly all the way from moulding to final packaging. Typically, micro-optics cannot be bulk packaged, and so many methods for packaging need to be available, the most common being custom thermoform trays and tape and reel. For low volume projects it is possible to hand load the trays, but high volumes require automation for inspection and placement into packaging. ●
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