Technical Library | 2021-04-08 00:30:49.0
As the electronic industry moves to lead-free assembly and finer-pitch circuits, widely used printed wiring board (PWB) finish, SnPb HASL, has been replaced with lead-free and coplanar PWB finishes such as OSP, ImAg, ENIG, and ImSn. While SnPb HASL offers excellent corrosion protection of the underlying copper due to its thick coating and inherent corrosion resistance, the lead-free board finishes provide reduced corrosion protection to the underlying copper due to their very thin coating. For ImAg, the coating material itself can also corrode in more aggressive environments. This is an issue for products deployed in environments with high levels of sulfur containing pollutants encountered in the current global market. In those corrosive environments, creep corrosion has been observed and led to product failures in very short service life (1-5 years). Creep corrosion failures within one year of product deployment have also been reported. This has prompted an industry-wide effort to understand creep corrosion
Technical Library | 2013-10-10 16:28:21.0
In the past 15 years, stretchable electronic circuits have emerged as a new technology in the domain of assembly, interconnections, and sensor circuit technologies. In the meantime, a wide variety of processes using many different materials have been explored in this new field. In the current contribution, we present an approach inspired by conventional rigid and flexible printed circuit board (PCB) technology.
Technical Library | 2022-10-31 17:25:37.0
Mixed formulation solder alloys refer to specific combinations of Sn-37Pb and SAC305 (96.5Sn–3.0Ag–0.5Cu). They present a solution for the interim period before Pb-free electronic assemblies are universally accepted. In this work, the surfaces of mixed formulation solder alloys have been studied by in situ and real-time Auger electron spectroscopy as a function of temperature as the alloys are raised above the melting point. With increasing temperature, there is a growing fraction of low-level, bulk contaminants that segregate to the alloy surfaces. In particular, the amount of surface C is nearly _50–60 at. % C at the melting point. The segregating impurities inhibit solderability by providing a blocking layer to reaction between the alloy and substrate. A similar phenomenon has been observed over a wide range of (SAC and non-SAC) alloys synthesized by a variety of techniques. That solder alloy surfaces at melting have a radically different composition from the bulk uncovers a key variable that helps to explain the wide variability in contact angles reported in previous studies of wetting and adhesion. VC 2011 American Vacuum Society. [DOI: 10.1116/1.3584821]
Technical Library | 2010-07-08 19:56:15.0
As technology becomes increasingly reliant on electronics, understanding the reliability of lead-free solder also becomes increasingly important. This research project focused on phase transformation kinetics with the lead-free solder SAC 305. Today in the electronics industry, SAC 305 is the most widely used solder, making it a high priority to understand its long-term stability and performance in a variety of service conditions. Recent evidence has shifted the focus from thermal aging to reflow temperature and time above liquidus values during initial solder melting.
Technical Library | 2013-08-22 14:28:58.0
Tin-rich solders are widely applied in the electronic industry in the majority of modern printed circuit boards (PCBs). Because the use of lead-tin solders has been banned in the European Union since 2006, the problem of the bridging of adjacent conductors due to tin whisker growth (limited before by the addition of Pb) has been reborn. In this study tin alloys soldered on glass-epoxy laminate (typically used for PCBs) are considered. Scanning ion microscopy with Focused Ion Beam (FIB) system and energy-dispersive X-ray spectroscopy (EDXS) were used to determine correlations between spatial non-uniformities of the glass-epoxy laminate, the distribution of intermetallic compounds and whisker growth.
Technical Library | 2013-09-05 17:44:14.0
Surface plasmon polaritons (SPPs) are localized surface electromagnetic waves that propagate along the interface between a metal and a dielectric. Owing to their inherent subwavelength confinement, SPPs have a strong potential to become building blocks of a type of photonic circuitry built up on 2D metal surfaces; however, SPPs are difficult to control on curved surfaces conformably and flexibly to produce advanced functional devices. Here we propose the concept of conformal surface plasmons (CSPs), surface plasmon waves that can propagate on ultrathin and flexible films to long distances in a wide broadband range from microwave to mid-infrared frequencies.
Technical Library | 2021-02-17 22:13:39.0
The development of various biosensors has revolutionized the healthcare industry by providing rapid and reliable detection capability. Printed circuit board (PCB) technology has a well-established industry widely available around the world. In addition to electronics, this technology has been utilized to fabricate electrical parts, including electrodes for different biological and chemical sensors. High reproducibility achieved through long-lasting standard processes and low-cost resulting from an abundance of competitive manufacturing services makes this fabrication method a prime candidate for patterning electrodes and electrical parts of biosensors. The adoption of this approach in the fabrication of sensing platforms facilitates the integration of electronics and microfluidics with biosensors. In this review paper, the underlying principles and advances of printed board circuit technology are discussed. In addition, an overview of recent advancements in the development of PCB-based biosensors is provided. Finally, the challenges and outlook of PCB-based sensors are elaborated. doi:10.3390/bios10110159
Technical Library | 2020-12-16 18:50:42.0
System operating speeds continue to increase as a function of the consumer demand for such technologies as faster Internet connectivity, video on demand, and mobile communications technology. As a result, new high performance PCB substrates have emerged to address signal integrity issues at higher operating frequencies. These are commonly called low Dk and/or low loss (Df) materials. The published "typical" values found on a product data sheet provide limited information, usually a single construction and resin content, and are derived from a wide range of test methods and test sample configurations. A printed circuit board designer or front end application engineer must be aware that making a design decision based on the limited information found on a product data sheet can lead to errors which can delay a product launch or increase the assembled PCB cost. The purpose of this paper is to highlight critical selection factors that go beyond a typical product data sheet and explain how these factors must be considered when selecting materials for high speed applications
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