Highly Complex PCBA from Microdul Compact Microelectronics As the Key to Epilepsy Therapy

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FAULHABER Drive Systems

For the EASEE neuromodulation system from Precisis, Microdul has developed a densely populated PCBA (Printed Circuit Board Assembly) with BGAs, chip-on-board and wire bonds in a very small space. The minimally invasive implant stimulates specific areas of the brain to reduce epileptic seizures.

Worldwide, around 3 to 4 percent of the population will develop epilepsy in the course of their lives. The disease is chronic and can be well controlled in up to 70 percent of those affected by drug therapy. However, the effectiveness of "seizure suppressant medication" is not sufficient for everyone. If seizures continue to occur despite careful treatment, this is referred to as "drug-resistant epilepsy". Around 70 percent of these patients suffer from focal epilepsy—in their cases, the Precisis treatment method can be a therapeutic option.

Transcranial Neuromodulation

EASEE stimulates the focus in the cortex with electrical pulses through the skull without the patient feeling it. The system consists of an electrode mat, a so-called Laplace electrode, which is placed under the scalp in a minimally invasive procedure—leaving the skull intact—and a flat electronic module that is placed on the pectoral muscle. The placement is individualized for each patient and the two units are connected subcutaneously with a stretchable cable.

Gallery

The hermetically sealed pulse generator contains the densely packed electronics and the battery. Precisis has brought Zurich-based Microdul AG on board to develop and manufacture the microelectronics. The company has many years of medtech experience and has implemented high-quality PCBAs in more than 15 class 3 active implantable medical devices (AIMDs), which are successful on the marke— and make everyday life easier for well over half a million people.

Microdul's specialties also include supporting start-ups that want to launch a high-quality device or implant on the market with a limited budget. From prototype development and qualification to industrialization and series production in accordance with ISO 13485, young companies such as Precisis benefit from a partnership that lasts throughout the entire product life cycle. This means that specialist knowledge and experience are incorporated into product development at an early stage, which prevents errors and helps to speed up market entry.

Two Stimulation Paradigms

The challenge of the EASEE lies in the flexible parameterization and precise control of the electronic stimulation so that it is directed exactly to the right areas of the brain and activates or inhibits certain nerve cells as required. The control is based on AI-based learning models that can be individually adapted to the patient's situation.

In addition to the subgaleal implantation, the system is also unique due to another aspect: it uses 2 different stimulation paradigms. Firstly, "DC-like stimulation" (DLS) is applied for 20 minutes per day to reduce the hyperexcitability of the epileptic network and thus the seizure frequency in the long term ("Long-Term Depression at the Epileptic Focus"). Secondly, high-frequency stimulation (HFS) is used to stimulate every 2 minutes during the period in which DLS is not used. This aims to suppress acutely occurring seizures. Both paradigms can be individually adjusted with regard to the stimulation parameters.

Key Technology PCBA

The hardware heart of the EASEE is the densely populated PCBA co-developed by Microdul, which takes up minimal space despite its complex layout and functions absolutely reliably. Many different SMD components, small and large ball grid arrays (BGA) and a bare die (chip-on-board) are installed on the PCB in a very small space. The latter is connected using wire bonds and covered with Glob-Top for mechanical protection. An underfill is applied to a BGA for heat dissipation and stability.

The higher the packing density, the more demanding the SMD assembly, BGA assembly and bare-die packaging. The qualification therefore covers all process steps from assembly and wire bonding to the application of the glob-top cover and laser marking and separation.

The risks, producibility and potential rejection hazards are identified in close cooperation with the customer during the creation of the PCBA layout (design for manufacturing). To ensure that Precisis only delivers modules of the required quality, the PCBAs are subjected to an X-ray inspection as well as an automatic optical inspection and visual inspection (under a microscope). In addition, the bond connections in each production batch are subjected to destructive testing. The production tests are followed by a "burn-in" (accelerated lifetime test) to detect early failures. The entire circuit is measured electronically before and after this stress test.

Comprehensive statistical process control (SPC) is used to ensure the highest quality at all times. From design development to production and quality inspection, all processes are fully traceable as required by ISO13485.

Smaller And More Complex Implants

Thanks to the miniaturization of electronic circuits, medtech manufacturers can design their active medical devices and implants (AIMD) to be smaller and more complex. This in turn benefits patients: The smaller the "medical device", the easier and safer the procedure. Following CE approval of the EASEE in 2022, Precisis has set its sights on market access in the USA as its next major goal and recently received the green light from the US Food and Drug Administration (FDA) to start the necessary clinical trial.

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