Injection over-moulded light in curved shape • 8 Dec 2020

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TNO-Holst Center and TNO-Brightlands Materials Center have designed and fabricated an injection over-moulded flexible electronic demonstrator with high strength engineering thermoplastics. High design freedom is presented in this demonstrator since the flexible electronics enable the applicability of the product with significant curvature. Also the integration between engineering thermoplastics and flexible electronics is realized by adhesion, which offers an extensive freedom in product design and tooling design. The injection moulded tool is designed to be suitable with different polymer based flexible electronics and different engineering thermoplastics, which is also simulated to offer an insight on the temperature and stress of electronics during the injection over-moulding process. Based on the simulation, electronics designers can optimise the design of their electronic circuits to maintain the functionality of electronics in the injection over-moulding process. The entire injection over-moulding process is fully automated, and the injection over-moulding cycle time of such demonstrator is in accordance to the typical cycle time of large scale injection moulding consumer electronic casing. Therefore, with the technology developed by Holst Center and Brightlands Materials Center, it is possible to have a one-step manufacture of a flexible electronic product with designed geometry of structural support casing without assembling the electronics into the casing fabricated in a separate injection moulding process.

This video shows the design and manufacturing of the demonstrator generating light from integrated sources that are injection moulded in a curved shape with ultra thin features of 4 mm. The driving architecture as realised in the handle allows dynamic effects of the curved light sources. Controls are based on capacitive touch sensing. The applied technology is circuitry based on printed electronics and adhesive bonding technology for the assembly of components. The flexible substrate and the stack built up of graphics and electronics are compatible with the process window of injection moulding, i.e. exposure to extreme pressure and temperature. 

The following steps are introduced in this video:

- design and manufacture of injection over-mould flexible electronics

- design of flexible circuit based on tooling design and simulation

- printing of flexible circuit

- automated injection over-moulding process with engineering thermoplastics