Classification System and Core Selection Criteria for Electronic Components in Medical Devices

In the highly regulated and reliability-critical field of medical devices, understanding electronic components extends far beyond traditional electronics engineering. It demands establishing a multidimensional cognitive framework—one that not only identifies components from a circuit functionality perspective but also evaluates them through the lenses of patient safety, regulatory compliance, and lifecycle management. This blog systematically analyzes the classification methods for medical electronic components across three dimensions: core functionality, safety criticality levels, and technical integration. It delves into the six critical factors that must be weighed during selection, providing comprehensive guidance for design and development.

Classification of Electronic Components

Classification by Core Function

This categorization is based on the specific electrical functions components perform within a device, representing the most fundamental and commonly used classification method. Active components serve as the device's “brain” and “nervous system,” including microprocessors, digital signal processors, and application-specific integrated circuits (ASICs). They handle signal processing, system control, and logical decision-making. Sensors and transducers serve as the device's “senses,” capturing physiological signals (e.g., ECG electrodes, pulse oximeters) and physical signals (e.g., accelerometers, pressure sensors). Passive components (resistors, capacitors, inductors) form the circuitry's foundation, regulating current and voltage. Connectivity and interface components (wireless modules, isolators) ensure secure internal and external communication, while actuators and output components (motors, displays, alarms) convert electrical signals into physical actions or information outputs. Finally, power supply components (medical adapters, batteries) provide stable, reliable energy for the entire system.

Classified by Criticality Level for Safety and Reliability

This is a classification method unique and critical to the medical device field, based on the risk level that component failure may pose to patients and operators, and strictly adhering to medical device safety standards (such as IEC 60601-1). Class A components are those whose failure poses no safety risk, such as status indicator lights or decorative elements on equipment. Class B components may cause loss of function or reduced performance upon failure, but do not directly create safety hazards. For example, damage to a main control chip or memory may shut down the device but typically does not directly harm patients. Category C components represent the highest risk level, where failure directly causes unacceptable risks. Examples include core components in life-support equipment (such as control valves in ventilators or cardiac pacemaker circuits) or barrier elements used for patient isolation. The selection, testing, and management of such components are subject to the most stringent requirements.

Classified by Technology Integration Level

This classification focuses on the inherent complexity and integration level of components. Discrete components represent the most fundamental form, referring to independent units with a single function, such as resistors, capacitors, and transistors. They form the building blocks of circuits. Integrated circuits utilize semiconductor processes to integrate numerous miniature components—including transistors, resistors, and capacitors—onto a single chip, creating complex circuit systems such as microcontrollers and power management chips. Modules or subsystems represent higher levels of integration. They combine multiple integrated circuits and discrete components into a complete module with specific functions, such as a blood oxygen measurement module integrating sensors, processors, and communication units. This approach significantly shortens product development cycles.

Key Considerations for Selecting Medical Electronic Components

Safety and Reliability

Failure of any component must not pose unacceptable risks to patients or operators. Therefore, components with extremely high reliability and minimal failure rates must be selected to ensure stable operation throughout the device's entire lifecycle. Potential failure modes must be thoroughly analyzed and safeguarded against.

Regulatory Compliance and Certification

Components must comply with stringent international and regional regulations. Manufacturers should ideally hold ISO 13485 medical device quality management system certification. Components themselves must meet environmental directives such as RoHS and REACH, while ensuring full traceability throughout the supply chain.

Long-Term Availability and Supply Chain Stability

Given the extended R&D and sales cycles of medical devices, core components must guarantee stable, continuous supply for the next decade or longer. Suppliers must strictly manage and provide advance notice for any design or process changes to maintain product consistency and safety.

Precision Performance and Rigorous Environmental Adaptability

Components must deliver high precision, stability, and low drift to meet application demands. They must withstand common clinical environment challenges including disinfection, sterilization, temperature fluctuations, and physical shocks, while exhibiting excellent electromagnetic compatibility to prevent mutual interference.

Biocompatibility

All components that come into direct or indirect contact with patients—including housings, cables, and other materials—must undergo biocompatibility evaluation according to ISO 10993 standards. This is critical to ensuring devices pose no toxicity, irritation, or allergic reactions to the human body and is non-negotiable.

Low-Power Design

For portable, wearable, and implantable medical devices powered by batteries, component power consumption directly determines device runtime and user experience. Consequently, the power characteristics of microcontrollers, sensors, and wireless communication modules become paramount considerations during component selection.

In summary, Selecting medical electronic components is an art that seeks the optimal balance between precision engineering and stringent regulations. It demands that engineers and decision-makers transcend individual performance parameters to build a holistic perspective encompassing functional realization, safety risks, supply chain resilience, and regulatory compliance. Only by prioritizing reliability, safety, and compliance throughout the entire lifecycle—from concept design to product end-of-life—can truly innovative and trustworthy medical devices ultimately be created.

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• Micriavia filling with copper: laser via size 0.1-0.125mm, priority 0.1mm
• Finished hole size for via-in-pad filling with resin: 0.1-0.9mm (drill size 0.15-1.0mm), 0.3-0.55mm normal (drill size 0.4-0.65mm)
• Max aspect ratio for via-in-pad filling with resin PCB - 12: 1
• Min resin plugged PCB thickness: 0.2mm
• Max via-filling ith resin PCB thickness: 3.2mm
• Making different hole sizes with via filling in one board: Yes
• Via filling with copper/silver: Yes

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Conclusion

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