ABSTRACT Multilayer ceramic capacitors (MLCCs) are increasingly used in harsh environments. For example, battery electric vehicles typically employ up to five times more MLCCs than an equivalent internal combustion engine vehicle. However, with exposure to humid or condensing environments, failure by electrochemical migration is an increasing issue as electronic feature sizes diminish, and voltages and environmental stresses increase. Contamination and bias in the presence of moisture facilitate electrochemical corrosion that results in lower surface insulation resistance (SIR) and this can be greatly accelerated in the presence of condensation. Therefore, it is crucial to develop rapid and dependable tests to predict the reliability of electronic components, in condensing environments. Nevertheless, reproducing repeatable levels of condensation during testing can be challenging, as most humidity chambers are designed to achieve stable, well controlled humidity and temperature conditions, but they do not offer controlled condensing options. This study employs a rapid condensation test that enables the creation of various levels of controlled condensation environments. This method uses the approach in which the test board is mounted on a platen whose temperature can be controlled independently of the humidity chamber. By reducing the test vehicle to a set temperature below the dew-point of the environment, controlled levels of condensation can be produced. This method significantly improves the repeatability and accuracy of electronic component reliability testing under such conditions. For the test, multiple test vehicles were assembled using 0603 sized MLCCs from different manufacturers, no-clean solder paste and reflow soldering. The obtained SIR result for each type of MLCCs at different condensation levels enabled a comparison of their relative performance. The results of this study confirmed that this condensation test, in combination with SIR measurements, can successfully evaluate the reliability of different types of MLCCs under identical conditions. This approach can predict potential failure mechanisms in condensing environments, helping to identify the most reliable options by observing how and when failures occur. These insights can provide a basis for design and manufacturing improvements, as well as component selection for specific applications.

ABSTRACT Screen printed and thermoformable conductive silver inks are one of the key building blocks for producing high performing Flexible Printed Electronics (FPE) and In-mold Electronic (IME) structures. Such novel electronic structures could potentially be used as capacitive touch sensors for Human Machine Interface (HMI) devices in consumer goods, white goods as well as in automotive electronics. In this study, we present the results of the electrical reliability performance of two types of silver inks, which are suitable for polyethylene terephthalate (PET) and polycarbonate (PC) based substrates to produce FPE and IME structures, respectively. Five different types of harsh environmental reliability tests were carried out to evaluate the electrical performance of these silver inks. The effect of various electronic circuit processing conditions, such as drying, thermoforming and injection molding, on the electrical resistance under various reliability test conditions was also evaluated. The results show that the silver inks are stable under such accelerated environmental reliability test conditions and are recommended for use in the construction of FPE and IME structures.

ABSTRACT Reliability is the primary concern of electronic assemblies in many applications today. The risk of electrochemical migration (ECM) is growing with new component packages and the exposition of assemblies to harsh environments. Experience shows that cleaning is the best option to enhance robustness against ECM. Also, it is often proven that cleaning must be thorough, including under components and any spaces between poles of the assembly. Such perfect cleaning requires not only dissolving and removing the flux residues to get the assembly visually clean but also removing the active ionic compounds and non-ionic or weak ionic compounds, which are invisible. Precise control of the rinsing steps is, therefore, inevitable. A previous study [3] showed that the current rinse monitoring by only conductivity is insufficient. Cleaning chemistry and flux contain different non-polar compounds, which cannot be adequately seen by conductivity change. Finally, a growing concentration of these low polar compounds causes not only a lowering of surface tension but also a dropping in surface insulation resistance values. In this study, we would like to show a new method to monitor the (so far not measured) proper function of active carbon filter in the close-looped rinsing system. We introduced the principle of such measuring at the SMTA Harsh conference in 2022. Also, we introduce the engineering method, how to simulate the practical loading of a cleaning machine by pollution of dissolved flux residues in the field, how to shorten and capture such process, and what possible reality distortions can occur.

ABSTRACT Electronic devices are expected to perform optimally in all kinds of locations worldwide, all with different climatic conditions, which heavily contributes to possible failure modes such as high leakage currents and Electro-Chemical Migration (ECM). Variations in temperature and humidity are a major driving force for condensation of ambient moisture on the electronics surface due to the formation and coalescence of water droplets to form larger drops on the PCB surface. This droplet formation causes a bridging pathway between two connector pads, and subsequent direction of growth of conductive dendrites, which form a short-circuit and can endanger device functionality. A test setup using a heat-exchanger allows cooling of custom-designed test PCBs coated with different solder masks (as experimental variation), thus simulating condensation and water layer build-up when in tandem with exposure to high-humidity conditions at room temperature. This build-up of water layer has been tracked using visual (in-situ Digital Microscope), electrical (Impedance and leak current measurements) and gravimetric (weight gain due to condensed water - converted to average water layer thickness) methods, in order to create a correlation to dendrite formation due to Electro-Chemical Migration. Image analysis and gravimetric measurements have been combined to provide insight into the coalesced droplet size (formed by condensing water) and the subsequent bridging of connectors on the solder mask surfaces. Measurement of changes in electrical impedance and leakage current during condensation, and further SEM analysis of the tested PCB surfaces have been used to present a unified theory of the effect of water droplet size on dendrite formation, dendrite morphology and functional electrical properties.

ABSTRACT Microelectronic assembly and packaging have to fulfil multiple roles. They have to support mechanically and to protect against external loads. Furthermore they should have a good transmission of the electrical signal via interconnects. The used materials and technologies are diversifying; scale factors are becoming larger. The technology, including geometrical parameters, physical and chemical properties of materials, is in a fast evolution. The considerations for more robust, reliable and resilient products should encompass strategies for the identification of new failure mechanisms and their interactions, test structure and test method development, specification and validation concepts. Under harsh environment conditions like corrosion, radiation, high temperature and vibration the aging of the components is drastically accelerated. In some cases the tests standards are not sufficient anymore. For instance the AEC-Q100 is not matching the demands of the conditions in e-mobility. Corrosion comes in the focus in drilling, automotive and air vehicles. Nowadays, reliability studies pass through the joint use of experimental evaluation and finite element simulations. Simulation can give a look on special aspects in terms of thermal-electrical-mechanical issues, radiation effects and corrosion sensitivity.

ABSTRACT Electrochemical failure modes result from any chemical or other contaminants on an electrical circuit. The effects of such contamination may be measured using electrical and chemical test methods. Electrochemical failure modes result from the interaction of chemical contaminants with board components under environmental stress. An intricate balance of metallic reactions occurs during the soldering process. Chemical equilibria involving solder melting, complexation, redox, dissolution, decomposition, and vaporization are strongly affected by the reflow profile and atmosphere. The activity of flux activators depends on the thermal profile, component standoff, and reflow environment. The location as well as the type of contaminations is essential for understanding risk. Since residue pooled under a component may still be active and ionic, there is considerable concern regarding the reliability of the finished product in the field. The purpose of this research paper is to present research on test methods that can be used to characterize, validate, control and monitor materials and processes for the presence of ionic contamination before and during assembly.