Stretchable PCBs are explicitly designed to save space while improving flexibility to meet smaller and mounting designs of high density.
Additionally, it also helps in reducing the process of assembly while enhancing reliability at the same time. In short, stretchable PCBs are the only solution that ensures miniaturization and the movement of electronic devices.
There are several advantages associated with stretchable printed circuit boards worth mentioning. For instance, stretchable PCBs can be twisted, bent, and moved without the risk of damaging the conductor. Additionally, special packaged sizes and several outlines get permitted with stretchable printed circuit boards.
That is not all. Stretchable PCBs provide outstanding electrical performance. They come with a low dielectric constant that gives room for the electrical transmission of signal and impressive thermal properties that make cooling very easy. Better yet, stretchable PCBs can operate well under high temperatures, unlike rigid PCBs.
Stretchable PCBs provide higher assembly output and reliability due to reduced internal connections hardware. Furthermore, there is little error during assembly since this is a PCBs designed or manufactured for one-way assembly. Stretchable boards can alter their positions with ease while remaining tethered electrically to each other all the time.
Briefly speaking, some of the reasons to use stretchable PCBs as opposed to rigid ones include:
• Reduced weight and space
• They meet changing flexing requirements
• Flexing for ease of service and installation
• Increase repeatability and reliability
• Excellent thermal management
• Reduce the costs of assembly
• Does away with connectors
• They provide uniform electrical characteristics for circuitry that require high speeds
What is the working principle of stretchable PCB?
While the thermoplastic Polyurethane used by manufacturers as substrate meant for stretchable PCBs can stretch easily, copper traces inhibits it from spreading. The reason for this is because copper is not malleable enough for such purposes.
Manufacturers use their confidential lay-up techniques and specialized press for bonding RA copper foil or standard ED on the Polyurethane substrate. Upon completing this step, they then use normal subtractive wet-etching printed circuit board steps to fabricate the stretchable circuits.
Since adding several layers of Polyurethane substrate and adhesive minimizes stretchability, most stretchable PCBs are double-sided or four layers at the most. Manufacturers apply polyurethane solder masks to finished PCBs to maintain a uniform elastomer design.
The assembly of stretchable PCBs employs the normal off-the-shelf surface mounting components soldered on the copper tracks. Since the parts are rigid, the places where the elements get positioned is impossible to stretch. In short, the concept of stretchable PCBs is some small islands of severe nature that holds few SMD components. These SMD components are interconnected using some conductive paper foil on stretchable substrates.
To ensure that traces of copper found on the substrate flex or bend without damage, designers give a horseshoe shape to the copper traces. After that, the horseshoe shapes are placed alternatively at 180° to allow them to meander along a path that would have been taken by straight marks. While other different ways, such as triangular shapes, can stretch, they exhibit high-stress levels and bring about lower reliability.