Inkjet etching of micro-via holes in thin polymer layers

Facilitated by the development of various direct-write techniques and functional polymeric materials including polymer based conductors and semiconductors, printed electronics are flourishing both commercially and as a research topic. This is not only because of their simpler manufacturing routes and lower cost, but also as a result of lower processing temperatures and better compatibility with flexible substrates, compared with conventional electronics. The development of conventional electronics has been guided by Moore s Law, the driver for which lies in the demand for electronic devices with better performance and portability at lower prices. Therefore, one can expect a similar trend for printed electronics to guide its development. Multi-layered printing can be adopted in printed electronics to achieve higher density integration, so that this development trend can be maintained. In such circumstances, creation of electrical connections between multiple layers emerges as an important issue for printed electronics. Inkjet-etched via holes are one potential solution to providing such electrical interconnections, and which can provide good integration with other inkjet-printed features simply by switching nozzles. This thesis aims to elicit a better understanding of the physics involved in inkjet etching and investigate the capability of the inkjet etching technique. In the thesis, the factors that can affect the size of via holes produced by inkjet etching are evaluated, which is significant for evaluating the capability of this technique to deliver industrially relevant features. Identified factors include droplet ejection frequency, droplet diameter, solvent properties and substrate temperature. Droplet ejection frequency, i.e. the reciprocal of the time interval between drops, determines the extent of evaporation of the solvent between two consecutive drop impacts. Droplet diameter determines the radius of the wetted area after the droplet I impacts on the surface and spreads into a sessile drop. Solvents with different evaporation properties result in different size evolution with the number of drops dispensed, as does droplet ejection frequency. Higher substrate temperatures can reduce the drop diameter during flight and decrease the evaporation time on polymer surfaces, which can shrink the size of via holes. Another important issue is achieving complete polymer penetration as residual polymer creates an electrical conduction barrier after such holes are subsequently filled with conductive materials or act as a barrier to filling by electroplating. Experiments have been carried out to test the effect of outer diameter and polymer thickness on polymer penetration. Electroplating is utilised to test the completeness of via hole penetration. A mechanism using the Marangoni effect to explain the protrusion drying pattern other than a hole in the polymer layer is proposed

A mechanism of the penetration limit for producing holes in poly(4-vinyl phenol) films by inkjet etching

A penetration limit has been experimentally demonstrated for inkjet etching of holes in thin polymer layers. A mechanism combining the competing coffee ring flow, polymer dissolution and diffusion into the solvent drop, and the interaction between the contact line during evaporation and the softened deformable polymer, is proposed to explain the existence of such a penetration limit. The height-averaged velocity of the coffee ring flow within the evaporating sessile drop is calculated during the initial stage of this etching process when the spherical cap geometry assumption is valid. This is compared with the diffusion velocity of the disentangled polymer into the solvent. The two competing flows are used to elucidate why a hole could be formed initially. The complex wetting dynamics of the receding contact line is included to explain the via hole profile evolution in the later stage of the etching process and the existence of a penetration limit. These two stages are differentiated by the drop volume with respect to the volume of the via hole produced by the preceding drop. The competition between the coffee ring flow transferring polymer away from the central region and the polymer diffusion within the solvent drop is postulated to contribute to either via hole formation or a penetration limit, depending on which one of the two processes is dominant within the solvent evaporation time scale

The effect of droplet ejection frequency on inkjet-etched micro via holes

Inkjet etching has been identified as a potential route to formation of micro via holes in polymer dielectrics. Such vias could facilitate three-dimensional integration and sequential build-up fabrication in printed electronics. In the research reported in this paper, ethanol droplets were jetted onto a poly(4-vinyl phenol) (also known as PVP or PVPh) layer at different frequencies in order to observe the effect of droplet ejection frequency on the diameters of the via holes produced. The results demonstrate that via holes remain the same diameter at a low drop ejection frequency, while they enlarge at a relatively high frequency. A mechanism for this behaviour is proposed for which high speed photography provides evidence

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Machining of Aluminum Alloy

Import 23/07/2015Diplomová práce se zabývá kvalitou opracované hliníkové slitiny EN AW-6082, speciálně drsností povrchu a měřením a vyhodnocením složek řezných sil. Teoretická část objasňuje základní pojmy věnované čelnímu frézování, obrobitelnosti hliníku, obráběným materiálům, řezným podmínkám a geometrii obrábění. V návrhu experimentální části práce je popsáno použití stroje, nástroje a vyměnitelných břitových destiček, přístrojů na měření drsnosti, velikosti řezných sil a navržené řezné podmínky. V experimentální části práce jsou změřeny drsnosti povrchu a presentovány výsledky naměřených hodnot drsnosti Ra a Rz. Řezné síly byly měřeny na piezoelektrickém dynamometru.This master thesis is concerned with the quality of machined aluminium alloy EN AW-6082, especially surface roughness and the measurement and evaluation components of the cutting forces. The theoretical part explains the basic concepts of frontal milling, machinability aluminium, machined material, cutting conditions and geometry processing. In the proposal of the experimental part is described the using of machine, tool and indexable inserts, devices for measuring roughness, cutting forces and proposed cutting conditions. In the experimental part of the work are measured surface roughnesses and presented the results of the measured values of roughness Ra and Rz. Cutting forces were measured on the piezoelectric dynamometer.346 - Katedra obrábění, montáže a strojírenské metrologievelmi dobř

Mechanism Insight into the Constitutional Phase Change Selection of Dynameric Framework Libraries

We show that the use of reversibly connected trialdehyde cores and diamine hydrophilic/hydrophobic connectors may generate libraries of dynameric frameworks of variable composition. The dynamic reversible imine- and trans-imination reactions induce the progressive segregation of libraries consisting of homo- and heterodynameric frameworks through the constitutional selection and successive precipitation of low-soluble hydrophobic films and hydrophilic/hydrophobic core–shell particles. This “precipitation-driven segregation” results in the formation of membrane with unique asymmetric morpholgy. Systematic compositional changes of dynamers, segregating solvents, and casting surfaces were correlated with the emerged membrane structure, and NMR/transmission electron microscopy–energy-dispersive X-ray characterizations mostly supported their hypothesis

Using Data-Driven Methods and Aging Information to Quantitatively Identify Microplastic Environmental Sources and Establish a Comprehensive Discrimination Index

The global distribution of microplastics (MPs) across various environmental compartments has garnered significant attention. However, the differences in the characteristics of MPs in different environments remain unclear, and there is still a lack of quantitative analysis of their environmental sources. In addition, the inclusion of aging in source apportionment is a novel approach that has not been widely explored. In this study, we conducted a meta-analysis of the literature from the past 10 years and extracted conventional and aging characteristic data of MPs from 321 sampling points across 7 environmental compartments worldwide. We established a data-driven analysis framework using these data sets to identify different MP communities across environmental compartments, screen key MP features, and develop an environmental source analysis model for MPs. Our results indicate significant differences in the characteristics of MP communities across environments. The key features of differentiation were identified using the LEfSe method and include the carbonyl index, hydroxyl index, fouling index, proportions of polypropylene, white, black/gray, and film/sheet. These features were screened for each environmental compartment. An environmental source identification model was established based on these features with an accuracy of 75.1%. In order to accurately represent the single/multisource case in a more probabilistic manner, we proposed the MP environmental source index (MESI) to provide a probability estimation of the sample having multiple sources. Our findings contribute to a better understanding of MP migration trends and fluxes in the plastic cycle and inform effective prevention and control strategies for MP pollution