AT&S develop and manufacture miniaturised PCBs for medtech

31 October 2018

Credit: Shutterstock
Credit: Shutterstock

The systems and components for therapy, diagnosis and patient monitoring are becoming smaller, but more powerful; accordingly, Austria Technologie & Systemtechnik is addressing the trend towards miniaturisation and digitisation in medical technology...

Despite progressive miniaturisation, safety and reliability have top priority. AT&S (Austria Technologie & Systemtechnik) have developed various technologies that enable the use of its circuit carriers – also in innovative applications (both on and inside the human body). Moreover, the company is one of the few printed circuit board (PCB) manufacturers that is certified to EN ISO 13485: the standard for medical devices.

AT&S's extensive experience of connection technology in the medical field contributes to making the devices for medical therapy (hearing aids, neurostimulation, pacemakers, prostheses, and so on), for the monitoring of vital signs (blood sugar, blood pressure, electrocardiogram [ECG]), as well as for diagnosis and imaging (magnetic resonance imaging [MRI], x-ray and ultrasound) even smaller, more powerful and more reliable.

More on miniaturisation in medtech

The miniaturisation of medical assemblies requires extremely small interconnect solutions and therefore very small PCB dimensions, with corresponding challenges; for example, the conductor track widths and distances are currently only 50 µm and are becoming smaller and smaller still. (By way of comparison, the thickness of a human hair measures between 80 µm and 120 µm.)

The electrical connections of the individual layers are realised using minute 'stacked vias'. A technological challenge here is the small annular rings around the vias – produced using lasers.

Thanks to years of experience and high-positioning accuracy, designs with 150 µm pad size and 50 µm annular ring are already possible today. The solder resist also has to be positioned very precisely. It is also important to note that the polyimide composite expands or shrinks during the processing phase.

Credit: Shutterstock
Credit: Shutterstock

This effect has to be minimised or compensated as far as possible. On the one hand, comprehensive expertise and, on the other hand, the use of modern manufacturing techniques and materials, are essential to be able to meet all these exacting requirements in the production process – in a reproducible and reliable manner.

From the hearing aid to the prosthesis...

With sophisticated, reliable technologies, AT&S have for many years been a world-leading PCB supplier for hearing aids (to name one example). Even modern cochlear implants require a high degree of miniaturisation and use similar technologies.

To clarify, a cochlear implant is an electronic medical device that uses electronic signals to stimulate the defective auditory nerves of the inner ear (cochlea) in order to transmit signals to the brain. For the respective designs, different flexible PCBs with usually two to six layers are required. Due to the small installation space, the miniature systems are designed with high density interconnection in mind, or otherwise stacked via circuits.

To stabilise the heart rhythm, pacemakers or defibrillators are implanted. Both systems are used for life support and the PCBs used must be of very high quality and reliable. For all PCBs used here, therefore, special regulations for process control, which are specified and described in international standards, apply.

The materials used must also satisfy specific criteria, which are regularly checked in extensive qualification tests. For many years, AT&S have successfully supplied various customers worldwide with these applications and, thanks to its wealth of experience, can offer added value in the development of sophisticated medical technology solutions.

Credit: Shutterstock
Credit: Shutterstock

HDI circuits are used for the control and adjusting unit of prostheses; and in the prostheses themselves, flexible PCBs are used to implement the dynamic movement can. An important criterion in this regard is that the flexible PCB installed here is constantly being moved with small bending radii. For this purpose, a highly flexible base material with rolled copper is used to ensure the required bending cycles and the low bending radii. Furthermore, the durability of these heavily-stressed parts is further increased by special surfaces (carbon print).

Finally, extremely compact interconnection technologies are also being used in wearables and tracking systems for patient monitoring and medical lifestyle applications. The spectrum ranges from mobile medical measuring devices (for blood pressure measurement) to smart watches and fitness trackers.

Again, miniaturisation and reliability is required, but also at the lowest possible cost. Against this background, AT&S's 2.5D technology offers advantages for the implementation of cavities. The defined indents (cavities) in the PCBs can be used to ‘lower’ electronic components, such as sensors and even logic components – generally granting the assembled PCB a thinner structure.

Thanks to highly-miniaturised PCB technology as a carrier for the corresponding electronics, 'smart capsules', which monitor specific body parameters and transmit the relevant data or deliver a controlled dose of medication, are now a reality, too.

In addition to the necessary miniaturisation and high-quality requirements in medical technology, the development of new biocompatible materials also presents a challenge. AT&S is researching materials that are to be used directly in the body.

The objective of such research is twofold: depending on the field of application, the materials should, on the one hand, be resistant and, on the other hand, have no negative effects on humans themselves and their environment.

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