Mikko Heikkinen

Hot Laminated Multilayer Polymer Illumination Structure Based on Embedded LED Chips

The dominant technology for manufacturing backlight illumination structure (BLIS) is typically based on the use of individually packaged surface mount device light emitting diodes (LEDs) and special light guide plate (LGP) and diffuser films. The prevailing BLIS package, however, contains several separate diffuser films, which results in a thick and costly structure. In addition, the light coupling from LED to the LGP is sensitive to alignment errors causing nonuniform and inefficient illumination. We have demonstrated a novel hot laminated packaging structure for backlighting solutions, which is based on inorganic LED chips and multilayer polymer structure. The main advantages of the implemented system compared to the traditional light guiding system are easy optical coupling with high efficiency in an integrated and thin package. The performed designs of 3×3, 5×5, and 5×7 LED chip matrices, verified by test structure implementations and characterizations, showed that the final thickness of the BLIS depends on the required uniformity of illumination, allowed LED device pitch and efficiency of the diffuser. The final BLIS demonstrator size was 50×75 mm2 consisting of six 25×25 mm2 modules. Each module consisting 5×5 LED devices resulting in total number of 150 LED devices with 5-mm pitch. The measured key characteristics of the demonstrator were as follows: average brightness 11.600 cd/m2 (ILED = 2 mA), luminous efficiency 22 lm/W, color temperature 5550 K, commission on illumination values (x = 0.331, y = 0.411), Color Rendering Index ≥ 70, and total power conversion efficiency of 6.3%. The combination of the developed Matlab performance simulation tool and cost-of-ownership cost evaluation tool enables us to estimate the manufacturing cost of a specific BLIS element against the required performance, assisting decision-making in different applications and specific individual customer cases.

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.

Backlight illumination structure based on inorganic LED devices and laminated multilayer polymer substrate

The dominant technology for manufacturing backlight illumination structures is typically based on use of individually packaged Surface Mount Device (SMD) Light Emitting Diodes (LEDs). The optical power from sources is coupled to the light guide having a special structure to couple light out so that uniform illumination is achieved to the illuminated component, typically LCD display. In practice the structure contains several separate diffuser films, which results to a thick and costly structure. In addition, the light coupling from LED to the light guide is sensitive to alignment errors causing nonuniform and inefficient illumination. The developed alternative packaging structure for backlighting solutions is based on inorganic LED devices and multilayer polymer substrate. Polycarbonate substrate material was used, which is highly transparent at visual band allowing low absorption and has good lamination properties in hot lamination process allowing compact integrated structures. In the manufacturing process the individual polymer sheets with an individual thickness of 100 µm were printed with conductive patterns produced by screen printing using silver-based thick film pastes. The final integrated multilayer structure containing embedded LED devices was produced in a hot lamination process. Two types of LED devices were embedded within the laminated structure, namely blue LED, type C470RT290 and green LED, type C527RT290. The bottom area of the chip was 300 µm × 300 µm and the thickness 115 µm. The devices were manufactured by Cree. Test samples containing 3 × 3, 5 × 5 and 5 × 7 LED devices were designed, implemented and characterized. The final laminated structure thickness was typically 300 µm. The performed designs verified by test structure implementations and characterizations showed that the final thickness of the backlight illumination structure depends of the required uniformity of illumination and allowed LED device pitch and used diffuser efficiency. The main advantages of the implemented system compared to traditional light guiding system are easy optical coupling with high efficiency in an integrated and thin package. The developed technology seems to be suitable to produce backlight illumination structures for applications in which thin, lightweight, efficient and cost-efficient backlight illumination structure is essential, such as, hand-held devices. In addition, the developed technology seems to be possible to apply in several other applications, such as, information tables, signboards and displays.

Component Packages for IMSE™ (Injection Molded Structural Electronics)

TactoTek has developed and commercialized an advanced platform of Injection Molded Structural Electronics (IMSE). IMSE is an innovative technology and significantly different from the conventional electronics in which components are reflow soldered onto printed circuit boards. Many of the packages optimized for conventional electronics can be used with IMSE technology. However, they are not ideal. In this paper we present the ideal component package for IMSE integration. We also present the TactoTek internal component qualification process. It verifies that component packages do not lower IMSE manufacturing yield and are reliable in IMSE designs.

Laser profilometer module based on a low-temperature cofired ceramic substrate

We realized a laser profilometer module using low tempera- ture cofired ceramics technology. The device consists of a vertical-cavity surface-emitting laser as the light source and a complementary metal oxide semiconductor image sensor as the detector. The laser transmitter produces a thin light stripe on the measurable object, and the receiver calculates the distance profile using triangulation. Because the design of optoelectronic modules, such as the laser profilometer, is usually carried out using specialized software, its electronic compatibility is very impor- tant. We developed a data transmission network using commercial opti- cal, electrical, and mechanical design software, which enabled us to electronically transfer data between the designers. The module electron- ics were realized with multilayer ceramics technology that eases compo- nent assembly by providing precision alignment features in the sub- strate. The housing was manufactured from aluminum using electronic data transfer from the mechanical design software to the five-axis milling workstation. Target distance profiles were obtained from 100 points with an accuracy varying from 0.1 mm at a 5-cm distance to 2 cm at 1.5 m. The module has potential for distance measurement in portable devices where small size, light weight, and low power consumption are important.