Effect of overmolding process on the integrity of electronic circuits

Traditional injection molding processes have been widely used in the plastic processing industry. It is the major processing technique for converting thermoplastic polymers into complicated 3D parts with the aid of heat and pressure. Next generation of electronic circuits used in different application areas such as automotive, home appliances and medical devices will embed various electronic functionalities in plastic products. In this study, over-molding injection molding (OVM) of electronic components will be examined to insert novel performance in polymer materials. This low-cost manufacturing process offers potential benefits such as, reduction in processing time, higher freedom of design and less energy used when compared to the conventional injection molding method. This paper aims to evaluate the performance of this process and propose a series of alternative solutions to optimize the adhesion between and integration of electronics and engineering plastics. A number of methods are used to optimize the process so that the electronic circuits are not damaged during the over-molding, moreover to test the reliability of the system in order to control the continuity of connections between the electronic circuit foils and the electronic components after the OVM process. Correspondingly, we have performed specific tests for this purpose varying in some conditions: the type of injected plastic used, over-molding parameters (temperature, pressure and injection time), electronic circuit design, type of assembled electronic components, type of foils used and the effect of using underfill material below the electronic component. From these tests, first conclusions were made. We have also studied adhesion between the foil and the over-molding material. In this case, various types of engineering plastics have been tested; polypropylene (PP), 30% weight percentage glass,fiber filled polypropylene (GF-PP), Polyamide-6 (PA6) and 50% weight percentage glass fiber filled polyamide-6 (GF-PA6). It was proved that throughout the wide range of tested materials, (PA6) over-molded samples showed a better adhesion on the copper-polyimide foils than the rest. These plastics were over-molded on two types of polyimide (PP/Copper (Cu) tracks foils with and without an adhesive layer between PI and Cu. It was obviously clear that the foils with on adhesive layer between PI and Cu had more delamination in the Cu tracks than the foils without an adhesive layer. Furthermore, it was shown that the presence of an underfill material has on effect on the system as the foils that had an underfill material below their components successfully had a better connection than the folis without an underfill material. Finally, experiments were executed using the two probe method as an electrical measurement and microscope investigation as the visual inspection

Fabrication of mixed-scale PMMA (Polymethyl methacrylate) fluidic device via thermal nanoimprint using a convex carbon mold

Department of Mechanical EngineeringRecently micro-/nanofluidic devices are widely used for various research areas including biological, chemical, and biomedical applications. Such mixed-scale micro-/nanofluidic devices are generally fabricated using photolithography and direct writing methods (e. g., e-beam lithography or focused ion beam milling) in series. However, the direct writing methods require high cost and long process time thus resulting in low throughput issue. PDMS (Polydimethylsiloxane) replication can overcome the low throughput issues. The PDMS replication method consists of a PDMS casting process on a pre-patterned mold and a subsequent curing processes. By this method, PDMS mixed-scale channel patterns can be replicated repeatedly, thus, total throughput of fabricated mixed-scale PDMS fluidic device is enhanced. However, the channel size is smaller, the more PDMS channels are collapsed due to the low Young???s modulus and hardness of PDMS. In this study, I developed the fabrication method of mixed-scale PMMA (Poly methyl methacrylate) fluidic device via simple thermal nanoimprint using a monolithic mixed-scale convex carbon mold (microchannel mold: width = ~ 50 ???m, height = ~ 5 ???mnanochannel mold: width = ~ 600 nm, height = ~ 60 nm). The monolithic carbon mold was fabricated using carbon-MEMS consisting of two step photolithography processes and one step pyrolysis. In pyrolysis, polymer structures shrank dramatically and thus microscale photoresist structures were converted into sub-micro- or nanoscale carbon structures. In nanoimprint process, the shape of the monolithic mixed-scale convex carbon mold was transferred into a PMMA sheet while the polymer sheet was heated. After demolding the carbon mold from the patterned PMMA sheet, the patterns were accurately transferred on the PMMA sheet (microchannel: width = ~ 50 ???m, height = ~ 5 ???mnanochannel: width = ~ 600 nm, height = ~ 60 nm). The pyrolyzed carbon mold could be easily demolded because of its curved side walls resulting from anisotropic volume reduction in pyrolysis. This special side wall geometry and good robustness of the carbon mold ensured reproducibility in nanoimprint. The mixed-scale channels were sealed by another thin PMMA sheet with low pressure and heat after oxygen plasma treatment. PMMA has higher Young???s modulus compared to PDMS (polydimethylsiloxane) so that the PMMA channels ensured consistent nanochannel fabrication and operation without channel collapse. The PMMA mixed-scale fluidic device was used to entrap single particles via diffusiophoresis. In the fluidic device, microchannels and nanochannels were smoothly connected via Kingfisher-beak-shaped 3D microfunnels that were converted from polymer triangular prims via pyrolysis. By filling two microchannels that are connected via multiple nanochannels with high concentration solution and low concentration solution respectively and controlling pressure difference between two microchannels, local concentration gradients can occur near the 3D microfunnels at the microchannel with low concentration. The localized concentration gradients generate local electric fields resulting in diffusiophoresisthe motion of charged particles along the localized electric fields. In this experiment, 1 ??m-diameter charged single particles dispersed in the low concentrate solution were dragged from the microchannel into the 3D microfunnels via diffusiophoresis. Consequently, the unique 3D microfunnel worked as a chamber where single particle was entrappedthus, single particles could be entrapped without external electric force in 3D microfunnels. The diffusiophoresis-based single particle entrapment experiment showed the potential of the mixed-scale channel networks as a single cell research tool.ope

Reactive & Efficient: Organic Azides as Cross-Linkers in Material Sciences

The exceptional reactivity of the azide group makes organic azides a highly versatile family of compounds in chemistry and the material sciences. One of the most prominent reactions employing organic azides is the regioselective copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition with alkynes yielding 1,2,3-triazoles. Other named reactions include the Staudinger reduction, the aza-Wittig reaction, and the Curtius rearrangement. The popularity of organic azides in material sciences is mostly based on their propensity to release nitrogen by thermal activation or photolysis. On the one hand, this scission reaction is accompanied with a considerable output of energy, making them interesting as highly energetic materials. On the other hand, it produces highly reactive nitrenes that show extraordinary efficiency in polymer crosslinking, a process used to alter the physical properties of polymers and to boost efficiencies of polymer-based devices such as membrane fuel cells, organic solar cells (OSCs), light-emitting diodes (LEDs), and organic field-effect transistors (OFETs). Thermosets are also suitable application areas. In most cases, organic azides with multiple azide functions are employed which can either be small molecules or oligo- and polymers. This review focuses on nitrene-based applications of multivalent organic azides in the material and life sciences

Complete fabrication station of scalable microfluidic devices for sensing applications

Microfluidics has become a field of intense research in the last decades due to the interesting capabilities this type of devices have. In the sensing area, they are meant to outperform classical laboratory techniques in terms of speed, volume of sample required, resolution, handling and efficiency. However, the technology has not achieved the predicted impact on the actual sensing world. Among the issues that slow down its development, the limited scalability of the fabrication techniques used results in a poor translation from research to the market

Unconventional Low-Cost Fabrication and Patterning Techniques for Point of Care Diagnostics

The potential of rapid, quantitative, and sensitive diagnosis has led to many innovative ‘lab on chip’ technologies for point of care diagnostic applications. Because these chips must be designed within strict cost constraints to be widely deployable, recent research in this area has produced extremely novel non-conventional micro- and nano-fabrication innovations. These advances can be leveraged for other biological assays as well, including for custom assay development and academic prototyping. The technologies reviewed here leverage extremely low-cost substrates and easily adoptable ways to pattern both structural and biological materials at high resolution in unprecedented ways. These new approaches offer the promise of more rapid prototyping with less investment in capital equipment as well as greater flexibility in design. Though still in their infancy, these technologies hold potential to improve upon the resolution, sensitivity, flexibility, and cost-savings over more traditional approaches

Mechanical and structural investigation of porous bulk metallic glasses

The intrinsic properties of advanced alloy systems can be altered by changing their microstructural features. Here, we present a highly efficient method to produce and characterize structures with systematically-designed pores embedded inside. The fabrication stage involves a combination of photolithography and deep reactive ion etching of a Si template replicated using the concept of thermoplastic forming. Pt- and Zr-based bulk metallic glasses (BMGs) were evaluated through uniaxial tensile test, followed by scanning electron microscope (SEM) fractographic and shear band analysis. Compositional investigation of the fracture surface performed via energy dispersive X-ray spectroscopy (EDX), as well as Auger spectroscopy (AES) shows a moderate amount of interdiffusion (5 at.% maximum) of the constituent elements between the deformed and undeformed regions. Furthermore, length-scale effects on the mechanical behavior of porous BMGs were explored through molecular dynamics (MD) simulations, where shear band formation is observed for a material width of 18 nm

A vector light sensor for 3D proximity applications: Designs, materials, and applications

In this thesis, a three-dimensional design of a vector light sensor for angular proximity detection applications is realized. 3D printed mesa pyramid designs, along with commercial photodiodes, were used as a prototype for the experimental verification of single-pixel and two-pixel systems. The operation principles, microfabrication details, and experimental verification of micro-sized mesa and CMOS-compatible inverse vector light pixels in silicon are presented, where p-n junctions are created on pyramid’s facets as photodiodes. The one-pixel system allows for angular estimations, providing spatial proximity of incident light in 2D and 3D. A two-pixel system was further demonstrated to have a wider-angle detection. Multilayered carbon nanotubes, graphene, and vanadium oxide thin films as well as carbon nanoparticles-based composites were studied along with cost effective deposition processes to incorporate these films onto 3D mesa structures. Combining such design and materials optimizations produces sensors with a unique design, simple fabrication process, and readout integrated circuits’ compatibility. Finally, an approach to utilize such sensors in smart energy system applications as solar trackers, for automated power generation optimizations, is explored. However, integration optimizations in complementary-Si PV solar modules were first required. In this multi-step approach, custom composite materials are utilized to significantly enhance the reliability in bifacial silicon PV solar modules. Thermal measurements and process optimizations in the development of imec’s novel interconnection technology in solar applications are discussed. The interconnection technology is used to improve solar modules’ performance and enhance the connectivity between modules’ cells and components. This essential precursor allows for the effective powering and consistent operations of standalone module-associated components, such as the solar tracker and Internet of Things sensing devices, typically used in remote monitoring of modules’ performance or smart energy systems. Such integrations and optimizations in the interconnection technology improve solar modules’ performance and reliability, while further reducing materials and production costs. Such advantages further promote solar (Si) PV as a continuously evolving renewable energy source that is compatible with new waves of smart city technology and systems