Low cost fabrication processing for microwave and millimetre-wave passive components

Microwave and millimetre-wave technology has enabled many commercial applications to play a key role in the development of wireless communication. When dissipative attenuation is a critical factor, metal-pipe waveguides are essential in the development of microwave and millimetre-wave systems. However, their cost and weight may represent a limitation for their application. In the first part of this work two 3D printing technologies and electroless plating were employed to fabricate metal pipe rectangular waveguides in X and W-band. The performance for the fabricated waveguides was comparable to the one of commercially available equivalents, showing good impedance matching and low attenuation losses. Using these technologies, a high-performance inductive iris filter in W-band and a dielectric flap phase shifter in X-band were fabricated. Eventually the design and fabrication of a phased antenna array is reported. For microwave and millimetre-wave applications, system-on-substrate technology can be considered a very valuable alternative, where bulky coax and waveguide interconnects are replaced by low-loss transmission lines embedded into a multilayer substrate, which can include a wide range of components and subsystems. In the second part of this work the integration of RF MEMS with LTCC fabrication process is investigated. Three approaches to the manufacture of suspended structures were considered, based on laser micromachining, laser bending of aluminium foil and hybrid thick/thin film technology. Although the fabrication process posed many challenges, resulting in very poor yield, two of the solution investigated showed potential for the fabrication of low-cost RF MEMS fully integrated in LTCC technology. With the experience gained with laser machining, the rapid prototyping of high aspect ratio beams for silicon MEMS was also investigated. In the third part of this work, a statistical study based on the Taguchi design of experiment and analysis of variance was undertaken. The results show a performance comparable with standard cleanroom processing, but at a fraction of the processing costs and greater design flexibility, due to the lack of need for masks.Open Acces

DESIGN OF EXPERIMENT (DOE) LIQUID PHOTOIMAGEABLE SOLDER MASKS PCB PADA TEACHING FACTORY MANUFACTURING OF ELECTRONICS (TFME) POLITEKNIK NEGERI BATAM

This paper examines several variables to formulated the best parameters in the PCB manufacturing process. This study was implements a PCB with a screen printing process that uses the LPISM (Liquid Photoimageable Solder Mask) application. Where in the process PCB coating is done by connecting the amount of solder liquid mask in one coating using the right parameters using the Design of Experiment (DoE) method. This DoE method improves the quality of the PCB at the lowest possible cost. DoE on LPISM applied at the Teaching Factory Manufaktur Elektronika Politeknik Negeri Batam with the aim of protecting the PCB lines from being connected to one another, providing the right measurements, and using the use of laminated mask solder. Thus, Politeknik Negeri Batam Teaching Factory laboratory assistants can produce PCBs using the LPISM method with quality according to standards. From the analysis, obtained an appropriate angle for screen printing is between 150-200 so that the screen is not damaged. In addition, the oven process can thin the solder mask up to 70-80%. In accordance with the results of comprehensive testing, the 24th data obtained can be recommended because it fulfill the IPC-SM-840C standard, with the 2.5 μm solder mask thickness.Makalah ini mengkaji beberapa variabel untuk mencari paramater yang paling baik dalam proses pembuatan PCB. Kajian ini mengimplementasikan PCB dengan proses screen printing yang menggunakan aplikasi LPISM (Liquid Photoimageable Solder Masks). Dimana dalam prosesnya pelapisan PCB dilakukan dengan mengendalikan jumlah cairan solder masks dalam sekali pelapisan menggunakan parameter yang tepat menggunakan metode Design of Experiment (DoE). Metode DoE ini bertujuan untuk memperbaiki kualitas PCB dengan biaya seminimal mungkin. DoE pada LPISM diterapkan di Teaching Factory Manufaktur Elektronika Politeknik Negeri Batam dengan tujuan untuk melindungi jalur PCB agar tidak terhubung satu dan yang lainnya, memberikan takaran yang tepat, serta mengurangi penggunaan solder masks lamination. Sehingga, laboran di Teaching Factory, Politeknik Negeri Batam dapat memproduksi PCB yang menggunakan metode LPISM dengan kualitas sesuai standar. Dari hasil analisis, didapatkan sudut yang tepat untuk melakukan screen printing adalah antara 150 - 200 agar menghasilkan screen yang tidak rusak. Selain itu, proses oven dapat menipiskan solder masks hingga 70 – 80%. Sehingga dari hasil keseluruhan rangkaian percobaan, didapatkan data ke-24 yang dapat dijadikan rekomendasi karena telah sesuai dengan standar IPC-SM-840C, dengan hasil ketebalan solder masks yaitu 2,5 µm

Low-Cost Fabrication Techniques for RF Microelectromechanical systems (MEMS) Switches and Varactors

A novel low-cost microfabrication technique for manufacturing RF MEMS switches and varactors is proposed. The fabrication process entails laser microstructuring and non-clean room micro-lithography standard wet bench techniques. An optimized laser microstructuring technique was employed to fabricate the MEMS component members and masks with readily available materials that include, Aluminum foils, sheets, and copper clad PCB boards. The non-clean room micro-lithography process was optimized to make for the patterning of the MEMS dielectric and bridge support layers, which were derived from deposits of negative-tone photosensitive epoxy-based polymers, SU-8 resins (glycidyl-ether-bisphenol-A novolac) and photoacid activated ADEX™ dry films. The novel microfabrication technique offers comparatively reasonably yields without intensive cleanroom manufacturing techniques and their associated equipment and processing costs. It is an optimized hybrid rapid prototyping manufacturing process that makes for a reduction in build cycles while ensuring good turnarounds. The techniques are characterized by analysing each contributing technology and dependent parameters: laser structuring, lithography and spin coating and thin film emboss. They are developed for planar substrates and can be modified to suit specific work material for optimized outcomes. The optimized laser structuring process offers ablation for pitches as small as 75 µm (track width of 50 µm and gap 25 µm), with a deviation of 3.5 % in the structured vector’s dimensions relative to design. The lithography process also developed for planar and microchannel applications makes for the realization of highly resolved patterned deposits of the SU-8 resin and the laminated ADEX™ polymer from 1 µm to 6 µm and with an accuracy ±0.2 µm. The complete micro-fabrication technique fabrication techniques are demonstrated by realizing test structures consisting of RF MEMS switches and varactors on FR4 substrates. Both MEMS structures and FR4 substrate were integrated by employing the micro-patterned polymers, developed from dry-film ADEX™ and SU-8 deposits, to make for a functional composite assembly. Average fabrication yield up to 60 % was achieved, calculated from ten fabrication attempts. The RF measurement results show that the RF MEMS devices fabricated by using the novel micro-fabrication process have good figure-of-merits, at much lower overall fabrication costs, as compared to the devices fabricated by conventional cleanroom process, enabling it to be used as a very good micro-fabrication process for cost-effective rapid prototyping of MEMS

A Framework for the Implementation of an ISO 9000 Based Certification Program for Printed Circuit Board Manufacturers

ISO 9000:2000 is the newest version of the ISO 9000 family of standards. Unlike the 1994 version, it does not distinguish between servicing, testing and designing standards. It emphasizes quality improvement rather than quality control and briefly explains how to implement the Plan-Do-Check- Act (PDCA) cycle for improvement and the use of statistical techniques to improve the quality of process and product instead of controlling the quality of the output. The thesis explains why companies need to be certified and how to implement quality improvement programs. The objective of this thesis is to provide generic certification guidelines for printed circuit board manufacturers, based on ISO 9000:2000 standard. This standardized framework could assist companies in achieving ISO 9000 certification. Since every manufacturer has its own proprietary set of controls on their processes, these generic guidelines provide an opportunity for the user to plug in their own information and to write their own processes. Another objective of this thesis is to introduce a methodology for the implementation of the various methods and tools that can be applied for process improvement in printed circuit boards manufacturing

Multifunctional vertical interconnections of multilayered flexible substrates for miniaturised POCT devices

Point-of-care testing (POCT) is an emerging technology which can lead to an eruptive change of lifestyle and medication of population against the traditional medical laboratory. Since living organisms are intrinsically flexible and malleable, the flexible substrate is a necessity for successful integration of electronics in biological systems that do not cause discomfort during prolonged use. Isotropic conductive adhesives (ICAs) are attractive to wearable POCT devices because ICAs are environmentally friendly and allow a lower processing temperature than soldering which protects heat-sensitive components. Vertical interconnections and optical interconnections are considered as the technologies to realise the miniaturised high-performance devices for the future applications. This thesis focused on the multifunctional integration to enable both electrical and optical vertical interconnections through one via hole that can be fabricated in flexible substrates. The functional properties of the via and their response to the external loadings which are likely encountered in the POCT devices are the primary concerns of this PhD project. In this thesis, the research of curing effect on via performance was first conducted by studying the relationship between curing conditions and material properties. Based on differential scanning calorimetry (DSC) analysis results, two-parameter autocatalytic model (Sestak-Berggren model) was established as the most suitable curing process description of our typical ICA composed of epoxy-based binders and Ag filler particles. A link between curing conditions and the mechanical properties of ICAs was established based on the DMA experiments. A series of test vehicles containing vias filled with ICAs were cured under varying conditions. The electrical resistance of the ICA filled vias were measured before testing and in real time during thermal cycling tests, damp heat tests and bending tests. A simplified model was derived to represent rivet-shaped vias in the flexible printed circuit boards (FPCBs) based on the assumption of homogenous ICAs. An equation was thus proposed to evaluate the resistance of the model. Vias with different cap sizes were also tested, and the equation was validated. Those samples were divided into three groups for thermal cycling test, damp heat ageing test and bending test. Finite element analysis (FEA) was used to aid better understanding of the electrical conduction mechanisms. Based on theoretical equation and simulation model, the fistula-shape ICA via was fabricated in flexible PCB. Its hollow nature provides the space for integrations of optical or fluidic circuits. Resistance measurements and reliability tests proved that carefully designed and manufactured small bores in vias did not comprise the performance. Test vehicles with optoelectrical vias were made through two different approaches to prove the feasibility of multifunctional vertical interconnections in flexible substrates. A case study was carried out on reflection Photoplethysmography (rPPG) sensors manufacturing, using a specially designed optoelectronic system. ICA-based low-temperature manufacture processes were developed to enable the integration of these flexible but delicate substrates and components. In the manufacturing routes, a modified stencil printing setup, which merges two printing-curing steps (vias forming and components bonding) into one step, was developed to save both time and energy. The assembled probes showed the outstanding performance in functional and physiological tests. The results from this thesis are anticipated to facilitate the understanding of ICA via conduction mechanism and provide an applicable tool to optimise the design and manufacturing of optoelectrical vias

Design & analysis of acoustically improved vehicle floor carpets

The main objective of this research project is to design, develop and validate an innovative vehicle floor carpet system with improved acoustic performance, and thus reduce noise levels inside the vehicle cabins. The proposed solutions are expected to improve vehicle floor carpet product in areas of acoustic performance, cost, weight and waste reduction, to be environmentally friendly and sustainable in manufacturing. The following are main research outcomes of the project. • Acoustically improved vehicle floor carpet with higher sound transmission loss and in-cabin sound absorption coefficient, compared to current production carpet designs. • Vehicle floor carpet designs that introduce minimum weight and cost penalty for the acoustic performance improvement obtained. • Material database, i.e. measured acoustic parameters for mathematical modelling, of different vehicle carpet layers. • Virtual modelling and validation method for design evaluation at component and vehicle levels. • In-situ vehicle on-road validation test methods for carpet designs • Optimization methods for further improving the design The following are identified as recommendations for future design work in improving vehicle carpet acoustics. • Introducing air-gaps in the range of 10mm in between the heavy layers by use of a honey-comb structure improves the transmission loss by up to 20dB in the frequency range of 1kHz – 2kHz, and up to 10dB in the frequency range of 500Hz – 1kHz, and achieves the best sound transmission loss in these frequency ranges. • The introduction of honey-comb structure as an air-gap structure does not add any over-head in terms of weight or thickness, compared to foam, nor affects the total absorption of the carpet system. • Special tuned absorber layers like the perforated facing foam Helmholtz resonator and the corrugated foil faced foam membrane absorbers are excellent in extending the noise reduction frequency ranges to specific low frequency ranges of interest

Modelling and control of variability in PCB copper electroplating

This thesis is concerned with the modelling and control of the acid copper electroplating process for the manufacturing of printed circuit boards (PCB). The objectives of this study were to investigate the effects of process and product parameters on the workpiece level uniformity during the acid copper plating of lithographic patterns, plated-through holes (PTH) and blind-via (BV), and to explore the minimization of the deposit thickness variation. The parameters studied were the average current density (ACD), plating duration, concentration of additive and sulphuric acid, electrode separation (ES), line width and active area density ratio (AADR) of the circuit pattern. The effects of the copper sulphate concentration, aspect ratio (CAR) and depth ratio were also studied for the PTH and BV plating. The results of the study enhance the understanding of the limitations of applying current distribution and statistical models to the copper electroplating of PCB at a workpiece level. Multifactor two-level factorial and the central composite rotatable five-level experiments were designed, and a total of fourteen sets of experiment were conducted sequentially and used to generate statistical process models. For the plating of uniform patterns, ACD, ES and their quadratic effects were found to be significant and a 6- term second order model was built and verified to predict and minimize the workpiece level variability. The existence of a minimum plating variability was attributed to the minimum deviation from the Faraday's nominal thickness observed under a particular combination of ACD and ES. For non-uniform patterns, ACD, AADR and the ACD x ES interaction were found significant and an 8-term first-order prediction model was constructed. The minimum variability achievable was found to increase with the AADR, and was explained by the scattering effect of AADR on the average plating thickness. Verification of the model with patterns of same AADR but different line width revealed the limitation of the continuum concept, i. e. AADR alone is not sufficient to characterize a non-uniformly patterned substrate. Subsequent verification runs using a simple circuit pattern showed further that a composite parameter involving the overall active area density, the continuum area and the number of AAD contrasts, was appropriate. For the PTH plating, ACD, CAR, ACD2 and the ACD x ES, ES x CAR interactions were found significant but only ES, ES2 and ACD x ES were active for BV plating. Second-order models were also developed for the two processes in their respective optimum regions and verified experimentally. The optimum values of ACD and ES, and the minimum variability achievable were found to increase with the corrected aspect ratio of the through-hole. Given the difference in the optimum regions of the PTH and BV plating, a new response surface of the PTH process was constructed at the optimum region of the BV process and vice versa. The process limiting the workpiece level uniformity under different combinations of ACD and ES was found by the intersections of these responses surfaces. Finally, process parameters limiting the simultaneous minimization of the plating variability of pattern, PTH and BV were discussed. It showed that under most situations, the workpiece level variability of BVs was higher than that of the PTHs

An investigation into non-destructive testing strategies and in-situ surface finish improvement for direct metal printing with SS 17-4 PH : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering at Massey University, Albany, New Zealand

Figure 1.1 is re-used under an Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licenceAdditive Manufacturing (AM) technologies have the potential to create complex geometric parts that can be used in high-end product industries, aerospace, automotive, medical etc. However, the surface finish, part-to-part reliability, and machine-to-machine reliability has made it difficult to qualify the process for load dependent structures. The improvement of surface finish on metal printed parts, is a widely sought solution by these high-end industries and non-destructively characterizing the mechanical aptitude of metal printed parts, would pave the way for quality assessment strategies used to certify additively manufactured parts. This thesis examines the capability of laser polishing and non-destructive testing technologies and methods to address these difficulties. This research study presents an investigation into quality management strategies for Direct Metal Printing (DMP) with powdered Stainless Steel 17-4 PH. The research aim is split into two key categories: to improve the surface finish of metal additive manufactured parts and to non-destructively characterize the impact of defects (metallurgical anomalies) on the mechanical properties of the printed part. To improve surface finish of a printed part, a novel methodology was tested to laser polish the Laser-Powder Bed Fusion (L-PBF) parts during print with the built-in laser. Numerous technologies for non-destructive testing techniques already exist, and in the duration of this doctoral study various technologies were explored. However, the final solution focuses on layer-wise capture with a versatile low-cost imaging system, retrofitted within the DMP machine, to capture each layer following the lasering process. In addition, the study also focuses on progressing the characterization of data (images), using a combination of image processing, 3D modelling and Finite-Element-Analysis to create a novel strategy for replicating the as-built specimen as a computer-aided design model and performing simulated fatigue failure analysis on the part. This thesis begins with a broadened justification of the research need for the solutions described, followed by a review of literature defining existing techniques and methods pertaining to the solutions, with validation of the research gap identified to provide novel contribution to the metal additive manufacturing space. This is followed by the methodologies developed, to firstly, control the laser parameters within the DMP and examine the influence of these parameters using surface profilometry, scanning electron microscopy and mechanical hardness testing. The control variables in this methodology combines laser parameters (laser power, scan speed and polishing iterations) and print orientation (polished surface angled at 0º, 20º, 40º, 60º, 80º and 90º degree increments from the laser), using several Taguchi designs of experiments and statistical analysis to characterize the experimental results. The second methodology describes the retrofitted imaging system, image processing techniques and analysis methods used to reconstruct the 3D model of a standard square shaped part and one with synthesized defects. The method explores various 2D to 3D extrusion-based techniques using a combination of code-based image processing (Python 3, OpenCV and MATLAB image processing toolbox) and ready-made software tools (Solidworks, InkTrace, ImageJ and more). Finally, the new research findings are presented, including the results of the laser polishing study demonstrating the successful improvement of surface finish. The discussion surrounding these results, highlights the most effective part orientation for laser polishing the outline of an AM part and the most effective laser parameter combination resulting in the most significant improvement to surface finish (roughness and profile height variation). Summarily, the best improvement in surface roughness was achieved with the <80 angled surface with the laser speed, laser power and polishing iterations set to 500mm/s, 30W, 3 respectively. The sample set total average measured a 16.7% decrease in Ra. NDT digital imaging, thermal imaging and acoustic technologies were considered for defect capture in metal AM parts. The solution presented is primarily focused on the expansion of research to process digital images of each part layer and examine strategies to move the research from a data capture stage to a data processing strategy with quantitative measurement (FEA analysis) of the printed part’s mechanical properties. In addition, the results discuss a method to create feedback to the DMP to selectively melt problematic areas, by re-creating the sliced part layers but removing the well-melted areas from the laser scanning pattern. The methods and technological solutions developed in this research study, have presented novel data to further research these methods in the pursuit of quality assurance for AM parts. The work done has paved the way for more the research opportunities and alternative methods to be explored that complement the methods detailed here. For example, using a combination of in-situ laser polishing, followed by post-processing the AM specimens in an acid-based chemical bath. Alternatively, further exploring acoustic NDT techniques to create an in-built acoustic-based imaging device within the AM machine. Finally, this thesis cross-examines the work done to answer the research questions established at the start of the thesis and verify the hypotheses stated in the methods chapter

Optimum Design of Axial Flux PM Machines based on Electromagnetic 3D FEA

Axial flux permanent magnet (AFPM) machines have recently attracted significant attention due to several reasons, such as their specific form factor, potentially higher torque density and lower losses, feasibility of increasing the number of poles, and facilitating innovative machine structures for emerging applications. One such machine design, which has promising, high efficiency particularly at higher speeds, is of the coreless AFPM type and has been studied in the dissertation together with more conventional AFPM topologies that employ a ferromagnetic core. A challenge in designing coreless AFPM machines is estimating the eddy current losses. This work proposes a new hybrid analytical and numerical finite element (FE) based method for calculating ac eddy current losses in windings and demonstrates its applicability for axial flux electric machines. The method takes into account 3D field effects in order to achieve accurate results and yet greatly reduce computational efforts. It is also shown that hybrid methods based on 2D FE models, which require semi-empirical correction factors, may over-estimate the eddy current losses. The new 3D FE-based method is advantageous as it employs minimum simplifications and considers the end turns in the eddy current path, the magnetic flux density variation along the effective length of coils, and the field fringing and leakage, which ultimately increases the accuracy of simulations. After exemplifying the practice and benefits of employing a combined design of experiments and response surface methodology for the comparative design of coreless and conventional AFPM machines with cores, an innovative approach is proposed for integrated design, prototyping, and testing efforts. It is shown that extensive sensitivity analysis can be utilized to systematically study the manufacturing tolerances and identify whether the causes for out of specification performance are detectable. The electromagnetic flux path in AFPM machines is substantially 3D and cannot be satisfactorily analyzed through simplified 2D simulations, requiring laborious 3D models for performance prediction. The use of computationally expensive 3D models becomes even more challenging for optimal design studies, in which case, thousands of candidate design evaluations are required, making the conventional approaches impractical. In this dissertation a new two-level surrogate assisted differential evolution multi-objective optimization algorithm (SAMODE) is developed in order to optimally and accurately design the electric machine with a minimum number of expensive 3D design evaluations. The developed surrogate assisted optimization algorithm is used to comparatively and systematically design several AFPM machines. The studies include exploring the effects of pole count on the machine performance and cost limits, and the systematic comparison of optimally designed single-sided and double-sided AFPM machines. For the case studies, the new optimization algorithm reduced the required number of FEA design evaluations from thousands to less than two hundred. The new methods, developed and presented in the dissertation, maybe directly applicable or extended to a wide class of electrical machines and in particular to those of the PM-excited synchronous type. The benefits of the new eddy current loss calculation and of the optimization method are mostly relevant and significant for electrical machines with a rather complicated magnetic flux path, such is the case of axial flux and of transvers flux topologies, which are a main subject of current research in the field worldwide

Micro-extrusion process parameter modeling

Direct write processes are a family of technologies with the ability to deposit functional structures directly onto planar and non-planar surfaces. Direct writing includes a variety of processes that use different mechanisms to transfer materials on to substrates and can be generally distinguished from conventional rapid prototyping processes by a feature resolution in the sub-micron to micron range. The dispensing system studied in this thesis is a pneumatically actuated micro-extruder which is capable of processing a wide variety of materials. This material dispensing tool is capable of depositing small amounts of material to build three dimensional structures in an accurate and repeatable manner. The material dispensing system in this study has a variety of manufacturing applications ranging from printed electronics to biomedical applications. The material dispensing system employs a needle valve mechanism that allows ink or slurry to be deposited onto a substrate using air pressure. The dispensing tool used for this research is an nScrypt SmartPump. This research is focused on analyzing the extrusion process and developing and validating a parametric model for the input parameters using a design of experiments (DOE) approach. The aim is to improve the repeatability and accuracy of the process. A two phase approach was used to identify significant input parameters impacting the dimensional properties of a printed track. The first set of experiments employed a 2-level fractional factorial screening design where all user controllable parameters were tested against the response variables - height and width of a printed track. Significant parameters from this analysis were then used to build a regression equation for both height and width. It was observed that while the regression equation for height was accurate in predicting the output at intermediate levels, the regression equation for width was unable to do so and displayed signs of curvature. A higher order three-level regression model was then fit to the significant parameters for width and was found to be satisfactory in predicting process output. The errors observed between predicted outputs from the regression equations and actual output dimensions from the validation experiments were less than 2% and 3% for height and width respectively