Introduction to Stretchable Printed Circuit Boards and Their Applications

Introduction to Stretchable Printed Circuit Boards

Printed circuit boards (PCBs) are an integral part of most electronic devices. They provide the foundation on which components are mounted and connected. Traditional PCBs are made of rigid materials like FR-4 fiberglass. However, recent advances in materials science have led to the development of a exciting new type of PCB - the stretchable PCB.

What Are Stretchable PCBs?

As the name suggests, stretchable PCBs can be stretched, twisted, folded, and flexed without damage. This is in sharp contrast to standard rigid PCBs which would crack under such strain. Stretchable PCBs achieve this mechanical compliance by embedding stretchable interconnects on an elastic substrate.

Materials Used in Stretchable PCBs

The substrate and conductive traces in stretchable PCBs need to balance electrical conductivity and mechanical stretchability. Research has focused on materials like silicones, thermoplastic elastomers (TPEs), and shape memory polymers (SMPs) for the insulating substrate. Stretchable conductive materials include conductive polymers, nano-particle inks, liquid metals like eutectic gallium indium (EGaIn), and others.

Benefits of Using Stretchable PCBs

The novel properties of stretchable PCBs open up new possibilities in electronics and design. Some of their key benefits are:

Conformability to Surface

Stretchable PCBs can intimately wrap around surfaces, including irregular and 3D objects. This allows seamless integration into products. Applications like wearable devices particularly benefit from this conformal bonding.

Reduced Strain Damage

Mechanical strain is unavoidable in flexed or stretched applications. Stretchable interconnects accommodate this deformation without fracture failure. This improves reliability and minimizes need for special strain relief.

Light Weight and Portable

Substrate materials like silicones have a very low mass density compared to traditional PCBs. This significantly reduces weight, improving portability. The highly flexible nature also enables ease of transport.

Applications of Stretchable PCBs

The novel properties of stretchable circuits are enabling electronic systems in previously inaccessible areas. Some current and future applications include:

Wearable Electronics

Conformal bio-integrated devices like health monitors rely on the stretchable PCB's ability to bond intimately with skin for reliable measurements. The overall light weight also reduces load on the wearer.

Implantable Medical Devices

Implant electronics can benefit from stretchable PCBs. The circuits can more seamlessly integrate with soft internal body tissues. Stretchability also accommodates natural motions, enhancing patient comfort.

Robotics

Robots designed to tightly interact with humans can embed control or sensor electronics into robotic skin layers. Stretchable wiring conforms easily to movable joints or tactile surfaces.

Aerospace Skins

Embedding stretchable PCB antennas or sensors into an aircraft skin reduces weight versus exterior mounting. The elasticity also causes no internal material discontinuities or weaknesses.

Future Outlook

Initial research into stretchable electronics began in the 1990s. However, material and manufacturing challenges restricted commercialization opportunities until more recently. Now, improvements in printable conductive polymers and elastomers show promise in moving stretchable PCBs into mass production.

As material and process capabilities expand, many see stretchable electronics as a key enabling technology for sectors like wearables, robotics, healthcare, and aerospace. Its disruptive influence may match what rigid PCBs did for consumer electronics. Indeed, the next generation of our smart devices may literally be wrapped around us! With so many possibilities, stretchable PCBs mark an exciting future ahead.

FAQs

What materials are used to make stretchable PCBs?

Stretchable PCBs use elastic substrate materials like silicones, thermoplastic elastomers (TPEs), or shape memory polymers (SMPs). Conductive traces are made from materials such as conductive polymers, nanoparticle inks, or liquid metals.

How stretchable can these PCBs be?

Researchers have demonstrated stretchability of over 500% in laboratory samples. Commercially, around 20% stretchability is typical currently, with improvements expected as manufacturing processes mature.

Can components be directly soldered onto stretchable PCBs?

Yes, techniques like soldering can assembly components onto stretchable PCB conductors. However, not all commercial components may be rated for continual flexing.

What are potential applications for stretchable electronics?

Key applications gaining commercial interest are in wearable devices, bio-integrated medical monitors, soft robotics, sensing skins for machines or structures, and lightweight transport solutions.