In the expanding world of medical devices, and wearables, the demand for biocompatible substrates in flex and rigid PCBs has never been greater. As electronic systems move closer to and even into the human body, designers and manufacturers must ensure that every material used in the circuit stack-up meets strict safety and regulatory standards without compromising electrical, mechanical, or thermal performance.
What Are Biocompatible Substrates?
A biocompatible substrate is a base material that can safely interact with human tissue, fluids, or skin without causing an adverse biological response. In PCB manufacturing, this includes materials used for:
- Flexible circuit layers
- Rigid base laminates
- Coverlays and solder masks
- Adhesives and bonding layers
These materials must be non-toxic, non-cytotoxic, non-irritating, and free of extractables that might harm the human body during direct or indirect exposure.
Common Biocompatible Substrate Materials
Polyimide (PI)
Polyimide is the most widely used base material in flexible PCBs, known for its:
- High thermal stability
- Dimensional stability
- Flexibility and bend endurance
- Proven record of biocompatibility
Polyimide films like DuPont™ Kapton® and similar variants have passed ISO 10993 biocompatibility testing, making them a trusted choice for wearable and diagnostic devices.
Liquid Crystal Polymer (LCP)
LCP is emerging as a premium substrate for both rigid and flex circuits due to its:
- Ultra-low moisture absorption
- Excellent barrier properties
- RF/microwave compatibility
- Superior biocompatibility
LCP is particularly valuable in implantable devices, microfluidics, and miniaturized interconnects in high-frequency medical electronics.
PTFE (Teflon)
Polytetrafluoroethylene is chemically inert, hydrophobic, and thermally stable, with:
- Excellent biocompatibility
- Low dielectric constant
- Limited mechanical flexibility (mostly used in rigid/mixed configurations)
Talk to an engineer about the right biocompatible materials for your design.
Biocompatible Solder Masks and Coverlays
Beyond the base dielectric, the outer protective layers must also meet biocompatibility standards. For flex PCBs, this includes:
- Medical-grade coverlays (e.g., polyimide with biocompatible adhesives)
- Photo imageable solder masks rated for ISO 10993 or USP Class VI
These materials protect circuitry from abrasion, corrosion, and body fluids, while also allowing for laser ablation, pad exposure, or selective flexibility.
Applications That Require Biocompatibility
Industries that rely on biocompatible substrates include:
- Wearable Health Devices: Skin-adhered ECG/EEG monitors, biosensors, smart patches
- Surgical and Diagnostic Equipment: Endoscopy tools, catheters, imaging probes
- Drug Delivery Systems: Insulin pumps, infusion systems
- Laboratory and Analytical Systems: Microfluidic cartridges and sample analysis devices
Regulatory and Testing Considerations
Biocompatible PCBs must meet standards such as:
- ISO 10993-1: Biological evaluation of medical devices
- USP Class VI: Testing for plastic biocompatibility
- RoHS & REACH: Non-toxic and environmentally safe
Manufacturers must ensure traceability, material declarations, and documentation of biocompatibility testing for each material in the circuit stack-up.
Conclusion: Biocompatibility by Design
Biocompatible substrates are not just a regulatory checkbox they are fundamental to patient safety, device performance, and market access. Whether you're building a wearable patch for athletic monitoring, the choice of substrate materials determines the success of your product in the field and in the body.
At PICA Manufacturing Solutions, we specialize in building advanced, biocompatible flex and rigid PCBs that meet the highest performance and compliance standards for medical and wearable devices.