Erik Jung | Fraunhofer IZM: How do you wire bond a 25-micron bare silicon die inside a highly flexible, stretchable patch?
00:15:54.995 - 00:17:05.385
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How do you wire bond a 25-micron bare silicon die inside a highly flexible, stretchable patch?
Embedding active silicon integrated circuits into stretchable substrates requires a heterogeneous packaging approach to isolate fragile silicon from mechanical stress. By thinning silicon wafers down to just 25 microns—thinner than a human hair—engineers can embed bare die ICs into flexible polyimide carriers. This micro-module is then encapsulated within a protective thermoplastic polyurethane (TPU) envelope, shielding the active silicon from bending and stretching forces.
Traditional interconnection methods like lead-free soldering or isotropic conductive adhesives face severe limitations when bonding to low-temperature thermoplastic substrates. Thermal budgets must be strictly controlled to prevent the TPU from melting during assembly, while mechanical mismatch between rigid joints and flexible lines leads to premature fatigue failures.
To solve these interconnect bottlenecks, ultrasonic welding has emerged as a high-throughput, low-temperature alternative. By taking advantage of TPU’s capability to rapidly melt and resolidify under localized acoustic energy, engineers can establish reliable electrical connections to conductive layers without exposing the surrounding stretchable system to damaging thermal cycles.
In this short video, you can learn:
* The multi-layer packaging architecture used to protect 25-micron thin bare dies inside stretchable patches.
* Why traditional soldering and adhesive bonding struggle to meet the thermal and mechanical demands of thermoplastic substrates.
* How localized ultrasonic welding enables rapid, low-thermal-budget electrical interconnections on TPU.
📋 **Clip Abstract** This segment details advanced micro-integration techniques, showcasing how a 25-micron bare silicon die is embedded within polyimide and TPU layers. The speaker discusses why standard soldering is replaced by ultrasonic welding to accommodate the thermal limits of thermoplastic substrates.
#UltrasonicWelding, #UltraThinSilicon, #HeterogeneousIntegration, #ThermoplasticPolyurethane, #StretchableElectronics, #FlexibleHybridElectronics
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00:08:52.885 - 00:11:33.765
Why is the electronics industry rejecting silicone despite its superior 600% stretchability?
Why is the electronics industry rejecting silicone despite its superior 600% stretchability?
The selection of stretchable substrate materials for next-generation wearables represents a critical trade-off between mechanical compliance and manufacturing compatibility. While silicone elastomer substrates offer superb biocompatibility and up to 600% elongation, they face massive resistance in commercial electronics manufacturing due to issues like plasticizer bleed-out, poor adhesive bonding, and extreme propagation of surface micro-tears leading to catastrophic failure.
Thermoplastic polyurethane (TPU) has emerged as the industry's preferred compromise. TPU provides acceptable stretchability, integrates directly with standard printed circuit board (PCB) and textile manufacturing lines, and enables direct thermal lamination. However, TPU lacks intrinsic three-dimensional meshing capabilities, meaning engineers must rely on alternative conductor architectures like liquid metal alloys to achieve high reliability.
Liquid metal conductors (such as gallium-based alloys) present an appealing solution to the reliability challenges of traditional copper or silver meanders. Because liquid metals maintain conductivity during extreme elongation and exhibit self-healing behaviors upon mechanical rupture, they offer a viable path toward high-density, stretchable routing without compromising long-term fatigue life.
In this short video, you can learn:
* Why silicone's surface sensitivity and chemical properties make it incompatible with standard SMT assembly lines.
* The integration advantages of Thermoplastic Polyurethane (TPU) over silicone in industrial textile laminations.
* How liquid metal alloys solve the metal fatigue and routing density constraints of traditional meandering copper conductors.
📋 **Clip Abstract** This clip analyzes the engineering trade-offs between silicone and thermoplastic polyurethane (TPU) for stretchable wearable electronics. Erik Jung highlights why TPU and liquid metal conductors are gaining commercial traction over silicone due to superior manufacturing compatibility and self-healing properties.
#LiquidMetalConductors, #ThermoplasticPolyurethane, #StretchableElectronics, #SMTAssembly, #PrintedElectronics, #WearableElectronics
00:12:27.115 - 00:14:45.565
Why is burying active microelectronics directly inside disposable smart patches a commercial mistake?
Why is burying active microelectronics directly inside disposable smart patches a commercial mistake?
Integrating electronics into smart textiles and wound care dressings demands a clear architectural separation between disposable and reusable components. From both an environmental and economic standpoint, laminating active microprocessors and wireless radios directly into single-use substrates is unsustainable. A modular approach that isolates the disposable sensory layer from a detachable, reusable transceiver module is critical for commercial viability.
For the disposable textile layer, fabrication relies on laminating stretchable TPU-based circuits directly onto non-woven fabrics or utilizing laser-structured, metalized fibers. These substrates conform easily to the body and can even feature three-dimensional surface topography. By shaping the TPU carrier, engineers can create protruding, dry contact electrodes that establish excellent conformity with the skin for applications like electromyography (EMG).
Furthermore, these soft integration platforms allow for the co-packaging of both sensors and soft actuators. By embedding stretch-sensing meanders alongside pneumatic chambers, designers can create lightweight exoskeletons that detect physical movement and actively assist the wearer. This level of intimate physical integration is only achievable by pairing flexible substrate routing with advanced, near-body micro-packaging.
In this short video, you can learn:
* The strategic product architecture rule: separating disposable textile sensors from reusable active microelectronics.
* How laser-structured metalized fibers and TPU lamination create conformable dry electrodes for EMG.
* The integration of pneumatic actuators and stretch sensors on a single flexible substrate for wearable exoskeletons.
📋 **Clip Abstract** The speaker reviews the integration of electronic textiles, discussing the lamination of stretchable TPU circuits onto non-woven medical fabrics. He emphasizes a modular design strategy that keeps expensive active components detachable from disposable, single-use sensor membranes.
#ModularWearables, #StretchableTPU, #LaserStructuredFibers, #DryContactElectrodes, #ETextiles, #WearableMedTech