Antti Keränen

Printed hybrid systems

This paper presents research activities carried out at VTT Technical Research Centre of Finland in the field of hybrid integration of optics, electronics and mechanics. Main focus area in our research is the manufacturing of electronic modules and product structures with printed electronics, film-over-molding and polymer sheet lamination technologies and the goal is in the next generation of smart systems utilizing monolithic polymer packages. The combination of manufacturing technologies such as roll-to-roll -printing, injection molding and traditional component assembly is called Printed Hybrid Systems (PHS). Several demonstrator structures have been made, which show the potential of polymer packaging technology. One demonstrator example is a laminated structure with embedded LED chips. Element thickness is only 0.3mm and the flexible stack of foils can be bent in two directions after assembly process and was shaped curved using heat and pressure. The combination of printed flexible circuit boards and injection molding has also been demonstrated with several functional modules. The demonstrators illustrate the potential of origami electronics, which can be cut and folded to 3D shapes. It shows that several manufacturing process steps can be eliminated by Printed Hybrid Systems technology. The main benefits of this combination are small size, ruggedness and conformality. The devices are ideally suited for medical applications as the sensitive electronic components are well protected inside the plastic and the structures can be cleaned easily due to the fact that they have no joints or seams that can accumulate dirt or bacteria.

Hybrid in-mould integration for novel electrical and optical features in 3D plastic products

Next generation of smart systems in different application areas such as automotive, medical and consumer electronics will utilize various electronic, optical and mechanical functions integrated in plastic product structures. In this study, hybrid in-mould integration of electronic and optoelectronic modules was examined in order to embed novel functionality into polymer matrix. The feasibility to converge the printed electronics, component assembly and injection moulding manufacturing processes was examined by simulations, experimental tests and by realizing three demonstrators: over-moulded optical touch panel, plastic embedded flexible organic light emitting diode (OLED) foil and disposable healthcare sensor with over-moulded flexible printed circuit (FPC) connector. The demonstrators proved that hybrid in-mould integration could be feasible technology enabling seamless integration of optical, electrical and mechanical features into 3D plastic products.

Injection moulded lens array for high power LED modules

Light emitting diodes (LED) are increasingly replacing traditional light sources due to their better energy efficiency and potential for reliable operation with long lifetime. The price of LED-based luminaires is still fairly high. One way to decrease the manufacturing cost is to use single lens optics for many LEDs. Optics should provide high efficiency together with low cost and excellent reliability. This paper introduces injection moulded lens array designed for high power LED modules. The lenses were employed with a series of modules containing 4 × 4 white LEDs whose total luminous flux varied from 660 to 2280 lm. The lens had dimensions of 73.4 mm × 73.4 mm × 13.9 mm and it included alignment pins and sides that could be used for sealing. The lens optics gave elliptical 30° × 90° lighting pattern with the uniformity of the illuminance on plane surface better than 3∶2. The lens was optimized for Philips Lumileds Luxeon Rebel, but it was tested also with Cree X-Lamp, Luxeon K2, OSRAM Golden Dragon Plus, OSRAM Diamond Dragon and Seoul Z-power LEDs. This paper presents goniometer measurements of the luminous intensity and compares them to the simulations. Two different lens materials, namely cyclo olefin polymer (COP) and polyamide (PA), was used. The paper lists experiences obtained using these lenses. Especially the reliability of the lens and its attachment is discussed. In total, 24 LED modules were stressed in environmental tests including thermal cycling, thermal shock, moisture and corrosion. Observations made on the lens materials as well as lens attachment materials are depicted. Moisture and corrosion was not a problem but high temperatures challenged both the lens and adhesive materials. 22 modules were subjected to a life test of 6000 h where they were driven with a constant current of 700 mA and monitored continuously. The life test revealed failures in both lens materials. The results challenge the reliability of the plastic lenses in high power LED modules operating in high temperature applications.