Print-Consistency and Process-Interaction for Inkjet-Printed Copper on Flexible Substrate

Printed electronics is a fastest growing and emerging technology that have shown much potential in several industries including automotive, wearables, healthcare, and aerospace. Its applications can be found not only in flexible but also in large area electronics. The technology provides an effective and convenient method to additively deposit conductive and insulating materials on any type of substrate. Comparing with traditional manufacturing processes, which involves chemical etching, this technology also comes to be relatively environmental friendly. Despite its status, it is not without its challenges. Starting from the material being compatible in the printer equipment to the point of achieving fine resolutions, and with excellent properties are some of the challenges that printed electronics face. Among the myriad of printing technologies such as Aerosol Jet, micro-dispensing, gravure printing, screen printing, Inkjet printing, Inkjet has gained much attention due to its low-cost, low material consumption, and roll-to-roll capability for mass manufacturing. The technology has been widely used in home and office, but recently gained interest in printed electronics in a research and development setting. Conductive materials used in Inkjet printing generally comprises of metal Nanoparticles that need to be thermally sintered for it to be conductive. The preferred metal of choice has been mostly silver due to its excellent electrical properties and ease in sintering. However, silver comes to be expensive than its counterpart copper. Since copper is prone to oxidation, much focus has been given towards photonic sintering that involves sudden burst of pulsed light at certain energy to sinter the copper Nanoparticles. With this technique, only the printed material gets sintered in a matter of seconds without having a great impact on its substrate, due to which it is also preferred in low temperature applications. With all the knowledge, there is still a large gap in the process side with copper where it is important to look how the print process affects the resolution of the print along with the effect of post-print processes on electrical and mechanical properties. In this paper, a copper Inkjet ink is utilized for understanding the effect of Inkjet print parameters on the ejected droplet and its resolution. Post-print process is also quantified using a photonic sintering equipment for excellent electrical and mechanical properties. To demonstrate the complete process, commercial-off-the-shelf components will also be mounted on the additively printed pads via Inkjet. Statistically, control charting technique will be utilized to understand the capability of the Inkjet process.

DATA ANALYSIS AS THE BASIS FOR IMPROVED DESIGN FOR ADDITIVE MANUFACTURING (DFAM)

Additive Manufacturing (AM) has a large potential to revolutionize the manufacturing industry, yet the printing parameters and part design have a profound impact on the robustness of the printing process as well as the resulting quality of the manufactured components. To control the printing process, a substantial number of parameters is measured while printing and used primarily to control and adjust the printing process in-situ. The question raised in this paper is how to benefit from these data being gathered to gain insight into the print process stability. The case study performed included the analysis of data gathered during printing 22 components. The analysis was performed with a widely used Random Forest Classifier. The study revealed that the data did contain some detectable patterns that can be used further in assessing the quality of the printed component, however, they were distinct enough so that in case the test and train sets were comprised of separate components the predictions’ result was very poor. The study gives a good understanding of what is necessary to do a meaningful analytics study of manufacturing data from a design perspective.

Evaluation of The Printability of Lead Versus Lead Free Solder Pastes

As the global marketplaces consider mandating lead-free equipments, many questions arise about the impact and feasibility of replacing lead in printed circuit boards soldering applications. In this project, the results presented of a study on comparing the process of screening lead paste versus lead free paste parameters for regular stencil printing using standard manufacturing methods. The key process parameters studies were: squeegee speed, squeegee pressure, and screening yield for both types of pastes. Two solder paste formulations (lead paste and lead-free paste) were evaluated in this study. The analysis of the pastes deposit volumes showed that for normal manufacturing range of printer (screener) settings (speed and pressure) tested the two pastes performed the same. The results also showed that the squeegee speed has a greater effect on the printing process than the squeegee pressure. The tests clearly showed that the lead paste was affected more by setting changes compared to the lead free paste. Varying the print speed and pressure for type of pastes by observing the resulting printed paste volumes optimized screening parameters. This study confirms that a new stencil or stencil design is not needed for the lead free paste. However, this study recommends a change to the sitting of the screening print process. Stencil cleaning frequency is one of the main factors that impact the production rate in an SMT line. The project highlights new results that lead free paste throughput will be less compared to lead paste at the screening step. The number of rejected boards screened with lead free-paste exceeded normal manufacturing standards. As stencil cleaning is a must function, it was recommended to increase stencil wiping frequency when lead free paste [is] in use in order to obtain a consistent volume with less screening defect.

Evaluation of The Printability of Lead Versus Lead Free Solder Pastes

As the global marketplaces consider mandating lead-free equipments, many questions arise about the impact and feasibility of replacing lead in printed circuit boards soldering applications. In this project, the results presented of a study on comparing the process of screening lead paste versus lead free paste parameters for regular stencil printing using standard manufacturing methods. The key process parameters studies were: squeegee speed, squeegee pressure, and screening yield for both types of pastes. Two solder paste formulations (lead paste and lead-free paste) were evaluated in this study. The analysis of the pastes deposit volumes showed that for normal manufacturing range of printer (screener) settings (speed and pressure) tested the two pastes performed the same. The results also showed that the squeegee speed has a greater effect on the printing process than the squeegee pressure. The tests clearly showed that the lead paste was affected more by setting changes compared to the lead free paste. Varying the print speed and pressure for type of pastes by observing the resulting printed paste volumes optimized screening parameters. This study confirms that a new stencil or stencil design is not needed for the lead free paste. However, this study recommends a change to the sitting of the screening print process. Stencil cleaning frequency is one of the main factors that impact the production rate in an SMT line. The project highlights new results that lead free paste throughput will be less compared to lead paste at the screening step. The number of rejected boards screened with lead free-paste exceeded normal manufacturing standards. As stencil cleaning is a must function, it was recommended to increase stencil wiping frequency when lead free paste [is] in use in order to obtain a consistent volume with less screening defect.

Voxel based method for predictive modelling of solidification and stress in digital light processing based additive manufacture

A method for predicting the solidification and stress of a digital light processing 3D print process is presented, using a voxel-based, multi-layer model to predict the degree of polymerization of the material at every stage during the print.

Computer Science for (Live) Modernism(s)?

This chapter frames little magazines and periodicals as modernist objects which are often preoccupied with their own materiality in a distinct and unprecedented manner. To illustrate this principle, I argue that the little magazine represents the textual equivalent of what is known in the field of Computer Science as a metaobject, a part of a computer system that has the power to modify and update itself via a process known as reflection. While the production of a book—the typesetting, printing, and assemblage or ‘gathering’ of pages tended to take place out of the sight of their writers, the limited economic funds of a little magazine meant that their editors had a direct role in the print process. Drawing on examples from global periodicals including the British Rhythm, the Japanese periodical Shirakaba, the American Crisis and Little Review, I argue that it is periodicals’ status as metaobjects that makes them modernist. Their editors’ material choices and continued self-conscious references to the magazine as object (often with a set object) produce uniquely subjective, live reading experiences which characterize magazines as indelibly modern. Their modernisms—able to be experienced just through reading the magazine – are therefore timeless and can be replayed again and again.

Additively Printed Multilayer Substrate Using Aerosol-Jet Technique

Printing technologies, such as aerosol-jet, open possibilities of miniaturizing interconnects and designing circuits on nonplanar surfaces. Aerosol-jet is a direct-printing technique that provides an alternative manufacturing option to traditional subtractive methods that entail lithography or etching. Additionally, the aerosol-jet technique allows the circuits fabrication using noncontact method. Wide impact areas range from healthcare to wearables to future automotive applications. The aerosol-jet printer from Optomec utilized in this study consists of two types of atomizers, depending on ink viscosity. The ultrasonic atomizer, supports ink with a viscosity range of 1–5 cP, and the pneumatic atomizer that has a larger range of 1–1000 cP. This paper focuses on utilizing the aerosol-jet technique, using both atomizers to develop process parameters, in order to successfully print bimaterial, multilayer circuitry. The insulating material between two conductive lines used in the paper is of very high viscosity of 350 cP, which is suitable for the pneumatic atomizer and silver nanoparticle ink with comparatively low viscosity of 30 cP for the ultrasonic atomizer as a conductive ink. This paper also presents a statistical modeling approach that predicts line attributes, including microvia-diameter, before starting the print process, enabling us to pre-adjust the dimensions in computer-aided design for the desired output. Process parameters can obtain a fine print with satisfactory electrical properties, which develops improved dimensional accuracy. The importance of precleaning the substrate in addition to the printing process efficiency gaged as a function of process capability index and process capability ratio is also presented.