Reliability aspects of electronic devices for advanced requirements

Purpose – This paper aims to detail the qualification of alternative substrate materials and reliability aspects for quad flat no lead (QFN) packages for highly stressed electronic devices, e.g. for use in automotive applications. Design/methodology/approach – Detailed information is given on the advanced climatic and mechanical requirements that electronic devices have to withstand during life cycle testing to qualify for the automotive industry. Studies on the suitability of high-temperature thermoplastics as substrate materials for printed circuit boards and the qualification of QFN packages for advanced requirements are described. In addition, information on cause-effect relationships between thermal and vibration testing are given. Findings – With respect to adhesion of metallization on high-temperature thermoplastics and the long-term stability of the solder joints, these substrate materials offer potential for use in electronic devices for advanced requirements. In addition, the long-term stability of the solder joints of QFN packages depends on the design of the landings on the PCB and the separation process of the components during manufacturing. Research limitations/implications – The paper covers only a selection of possible high-temperature thermoplastic materials that can be used in electronics production. Also, this paper has a focus on the new packaging type, QFN, in the context of qualification and automotive standards. Originality/value – The paper details the requirements electronic devices have to meet to be qualified for the automotive industry. Therefore, this contribution has its value in giving information on possible substrate alternatives and the suitability for the usage of QFN components for highly stressed electronic devices

Whole brain radiation therapy alone versus radiosurgery for patients with 1–10 brain metastases from small cell lung cancer (ENCEPHALON Trial): study protocol for a randomized controlled trial

Background: Conventional whole brain radiotherapy (WBRT) has been established as the treatment standard in patients with cerebral metastases from small-cell lung cancer (SCLC), however, it has only modest efficacy and limited prospective data is available for WBRT as well as local treatments such as stereotactic radiosurgery (SRS). Methods/design: The present single-center prospective randomized study, conducted at Heidelberg University Hospital, compares neurocognitive function, as objectively measured by significant deterioration in Hopkins Verbal Learning Test – Revised total recall at 3 months. Fifty-six patients will be randomized to receive either SRS of all brain metastases (up to ten lesions) or WBRT. Secondary endpoints include intracranial progression (local tumor progression and number of new cerebral metastases), extracranial progression, overall survival, death due to brain metastases, local (neurological) progression-free survival, progression-free survival, changes in other cognitive performance measures, quality of life and toxicity. Discussion: Recent evidence suggests that SRS might be a promising treatment option for SCLC patients with brain metastases. The present trial is the first to prospectively investigate the treatment response, toxicity and neurocognition of WBRT and SRS in SCLC patients. Trial registration: Clinicaltrials.gov NCT03297788 . Registered September 29, 2017

Selective light sintering of Aerosol-Jet printed silver nanoparticle inks on polymer substrates

Printing silver nanoparticle inks to generate conductive structures for electronics on polymer substrates has gained increasing relevance in recent years. In this context, the Aerosol-Jet Technology is well suited to print silver ink on 3D-Molded Interconnect Devices (MID). The deposited ink requires thermal post-treatment to obtain sufficient electrical conductivity and adhesion. However, commonly used oven sintering cannot be applied for many thermoplastic substrates due to low melting temperatures. In this study a new sintering technology, selective light sintering, is presented, based on the focused, continuous light beam of a xenon lamp. Sintering experiments were conducted with Aerosol-Jet printed structures on various polycarbonate (PC) substrates. Especially on neat, light transparent PC, silver tracks were evenly sintered with marginal impact to the substrate. Electrical conductivities significantly exceed the values obtained with conventional oven sintering. Adhesive strength is sufficient for conductive tracks. Experiments with non-transparent PC substrates led to substrate damage due to increased light absorption. Therefore a concept for a variation of light sintering was developed, using optical filters. First experiments showed significant reduction of substrate damage and good sintering qualities. The highly promising results of the conducted experiments provide a base for further investigations to increase adhesion and qualifying the technology for MID applications and a broad spectrum of thermoplastic substrates

Automatic in-situ error correction for 3D printed electronics

Defects are a major issue in 3D printed electronics because even a tiny inaccuracy will lead to a faulty electronic circuit. This article presents a novel approach to correct printing defects with a neural network based automatic error correction. The errors are detected during printing by recording images of each wire with a high-resolution camera and segmenting the wires using convolutional neural networks. The neural network is trained with a dataset of printed wires with marked wire positions. A novel error detection algorithm then identifies connection breaks and generates repair paths for every connection break in the circuit, which are then executed by the printer. Multiple objects with deliberately inserted defects were printed and automatically repaired on different substrates using a Neotech AMT PJ15X printer to evaluate the performance. The algorithm detected all connection breaks, generated repair paths, and successfully repaired the faulty wires. This article also shows this approach's limitations and areas for future research, like complex circuits printed on 5-axis machines. The automatic error correction is highly reliable and is an important step towards a first-time-right production

A look at membrane patches with a scanning force microscope

We combined scanning force microscopy with patch-clamp techniques in the same experimental setup and obtained images of excised membrane patches spanning the tip of a glass pipette. These images indicate that cytoskeleton structures are still present in such membrane patches and form a strong connection between the membrane and the glass wall. This gives the membrane patch the appearance of a tent, stabilized by a scaffold of ropes. The lateral resolution of the images depends strongly on the observed structures and can reach values as low as 10 nm on the cytoskeleton elements of a (inside-out) patch. The observations suggest that measurements of membrane elasticity can be made, opening the way for further studies on mechanical properties of cell membranes