Technical Library | 2021-09-21 20:20:22.0
The electronics industry has been using the epoxy puck for the processing of the vast majority of electronics microsections since the 1970s. Minimal advancements have been seen in the methods used for precision micro-sections of PCBs, PCBAs, and device packages. This paper will discuss different techniques and approaches in performing precision and analytical micro-sections, which fuse the techniques and materials common in preparation of silicon wafers and bulk materials. These techniques have not only been found to produce excellent optical results, but transfer effectively to SEM for high magnification inspection and further analysis with minimal post-lapping preparation needed. Additionally, processing time is reduced primarily due to a significant reduction of bulk material removal earlier in the preparation, therefore needing less removal at later lapping steps compared to traditional sectioning methods. Additional techniques are introduced that mitigate some classic challenges experienced by technicians over the decades.
Technical Library | 2023-11-14 19:33:57.0
Wave soldering is an established technology and is commonly used where large unit volumes occur with low product variety. However, if a wave soldering machine is getting old or if technological changes or new PCB designs limits its manufacturing capabilities, consideration should be given to whether selective soldering would be a better choice. Anyone who deals with soldering through-hole and surface mount mixed-technology printed circuit assemblies will quickly discover that a selective soldering machine is not only less expensive that wave soldering, but selective soldering also offers the opportunity to meet customer requirements with significantly more flexibility. One such company is Thomas Preuhs GmbH. Located in Geislingen, Germany, Thomas Preuhs GmbH manufactures a variety of electronic assemblies for solar and HVAC data systems, automotive and white goods products as well as electric drive systems.
Technical Library | 2021-11-26 14:34:07.0
The use of desiccant bags filled with Silica Sand and or Clay beads used in conjunction with a Moisture Barrier Bag to control moisture for storage of printed circuit boards has long been an accepted practice and standard from both JEDEC and IPC organizations. Additionally, the use heated ovens for baking off moisture using the evaporation process has also been a long#2;standing practice from these organizations. This paper on alternative drying methods will be accompanied by completed independent, unbiased tests conducted by Vinny Nguyen, an engineering student (now graduated) from San Jose State University. The accompanied paper will examine the performance levels of different technologies of desiccant bags to control moisture in enclosed spaces. The tests and equipment set were reviewed by an engineer and consultant to the Lockheed Martin Aerospace Division and the IPC - TM-650 2.6.28 test method was review by engineer from pSemi. The tests were designed to mimic performance tests outlined in Mil Spec 3464, which both IPC and JEDEC have adopted for their respective standards. The test examined variables including absorption capacity rates, weight gain and release of moisture back into the enclosed area. The presentation will also address and highlight: • Similarities of PCBs and Heavy Equipment as it applies to Inspections, Causes of Failure, Types of Corrosion and Moisture Collection Points. • Performance Attributes of Different Desiccant Technologies as it applies to shape, texture, change outs, labeling and regeneration. • Venn Diagram of Electromechanical Failure with the circles 1. Current 2. Contamination 3. Humidity Presentation Available
Technical Library | 2018-10-24 18:04:12.0
Polymer Thick Film (PTF)-based printed electronics (aka Printed Electronics) has improved in durability over the last few decades and is now a proven alternative to copper circuitry in many applications once thought beyond the capability of PTF circuitry. This paper describes peak performance and areas for future improvement.State-of-the-art PTF circuitry performance includes the ability to withstand sharp crease tests, 85C/85%RH damp heat 5VDC bias aging (silver migration), auto seat durability cycling, SMT mandrel flexing, and others. The IPC/SGIA subcommittee for Standards Tests development has adopted several ASTM test methods for PTF circuitry and is actively developing needed improvements or additions. These standards are described herein. Advantages of PTF circuitry over copper include: varied conductive material compositions, lower cost and lower environmental impact. Necessary improvements include: robust integration of chip and power, higher conductivity, and fine line multi-layer patterning.
Technical Library | 2016-05-19 16:03:37.0
As consumers become more reliant on their handheld electronic devices and take them into new environments, devices are increasingly exposed to situations that can cause failure. In response, the electronics industry is making these devices more resistant to environmental exposures. Printed circuit board assemblies, handheld devices and wearables can benefit from a protective conformal coating to minimize device failures by providing a barrier to environmental exposure and contamination. Traditional conformal coatings can be applied very thick and often require thermal or UV curing steps that add extra cost and processing time compared to alternative technologies. These coatings, due to their thickness, commonly require time and effort to mask connectors in order to permit electrical conductivity. Ultra-thin fluorochemical coatings, however, can provide excellent protection, are thin enough to not necessarily require component masking and do not necessarily require curing. In this work, ultra-thin fluoropolymer coatings were tested by internal and industry approved test methods, such as IEC (ingress protection), IPC (conformal coating qualification), and ASTM (flowers-of-sulfur exposure), to determine whether this level of protection and process ease was possible.
Technical Library | 2019-01-09 19:19:52.0
The electronics industry has widely adopted Sn-3.0Ag-0.5Cu solder alloys for lead-free reflow soldering applications and tin-copper based alloys for wave soldering applications. In automated soldering or rework operations, users may work with Sn-Ag-Cu or Sn-Cu based alloys. One of the challenges with these types of lead-free alloys for automated / hand soldering operations, is that the life of the soldering iron tips will shorten drastically using lead-free solders with an increased cost of soldering iron tool maintenance/ tip replacement. Development was done on a new lead-free low silver solder rework alloy (Sn-0.3Ag-0.7Cu-0.04Co) in comparison with a number of alternative lead-free alloys including Sn-0.3Ag-0.7Cu, Sn-0.7Cu and Sn-3.0Ag-0.5Cu and tin-lead Sn40Pb solder in soldering evaluations.
Technical Library | 2020-09-23 21:29:25.0
The electronics industry could benefit greatly from using a reliable, manufacturable, reduced temperature, SMT solder material (alloy-composition) which is cost competitive with traditional Sn3Ag0.5Cu (SAC305) solder. The many possible advantages and some disadvantages / challenges are discussed. Until recently, the use of Sn/Bi based materials has been investigated with negative consequences for high strain rate (drop-shock) applications and thus, these alloys have been avoided. Recent advances in alloy "doping" have opened the door to revisit Sn/Bi alloys as a possible alternative to SAC-305 for many applications. We tested the manufacturability and reliability of three low-temperature and one SAC-305 (used as a control) solder paste materials. Two of these materials are doped Sn/Bi/Ag and one is just Sn/Bi/Ag1%. We will discuss the tests and related results. And lastly, we will discuss the prospects, applications and possible implications (based on this evaluation) of these materials together with future actions.
Technical Library | 2021-02-17 22:41:48.0
This review provides an overview of electrochemical sensors for nitrogen species, especially, ammonium, nitrate, and nitrite. Due to the extensive anthropogenic activities, the concentration of nitrogen species has been dramatically increased in the environment. In particular, fertilizers containing ammonium and nitrate have been extensively used in agriculture where as nitrite-included additives or preservatives have been used in food industry. Since excessive nitrogen species have an adverse effect to environment and human health such as eutrophication and methemoglobinemia (blue baby syndrome), efforts have been made to develop efficient monitoring methods. On that account, the U.S Environmental Protection Agency (EPA) established the maximum contaminant level (MCL) for nitrate and nitrite to be 10mg/L nitrate-N and 1mg/L nitrite-N in drinking water, respectively. Typical analytical methods for nitrogen species are chromatography or spectrometry. However, these methods require expensive instrumentations, skilled operator, and considerable sample pretreatment and analysis time. As an alternative approach, electrochemical sensors have been explored to monitor nitrogen species owing to its simplicity, superior sensitivity, versatility, rapidity, field applicability, and selectivity. In this review, electrochemical based detection methods for nitrogen species especially ammonium, nitrate and nitrite are systematically discussed, including the fundamentals of electrochemical techniques, sensing mechanisms, and the performance of each sensor. doi.org/10.1016/j.snr.2020.100022
Technical Library | 2019-03-15 16:26:50.0
While there have been quite dramatic and evident improvements in almost every facet of manufacturing over the last several decades owing to the advent and mass adoption of computer automation and networking, there is one aspect of production that remains stubbornly unaffected. Massive databases track everything from orders, to inventory, to personnel. CAD systems allow for interactive and dynamic 3D rendering and testing, digital troubleshooting, and simulation and analysis prior to mass production. Yet, with all of this computational power and all of this networking capability, one element of production has remained thoroughly and firmly planted in the past. Nearly all manufacturing or assembly procedures are created, deployed, and stored using methodologies derived from a set of assumptions that ceased to be relevant fifty years ago. This set of assumptions, referred to below as the “Paper Paradigm” has been, and continues as the dominant paradigm for manufacturing procedures to this day. It is time for a new paradigm, one that accounts for the vastly different technological landscape of this era, one that provides a simple, efficient interface, deep traceability, and dynamic response to rapidly changing economic forces.This paper seeks to present an alternative. Instead of enhancing and improving on systems that became irrelevant with the invention of a database, instead of propping up an outdated, outmoded and inefficient system with incremental improvements; rewrite the paradigm. Change the underlying assertions to more accurately reflect our current technological capability. Instead of relying on evolutionary improvements, it is time for a revolution in manufacturing instructions.
Technical Library | 2020-10-14 14:33:36.0
Epoxy based adhesives are prevalent interface materials for all levels of electronic packaging. One reason for their widespread success is their ability to accept fillers. Fillers allow the adhesive formulator to tailor the electrical and thermal properties of a given epoxy. Silver flake allow the adhesive to be both electrically conductive and thermally conductive. For potting applications, heat sinking, and general encapsulation where high electrical isolation is required, aluminum oxide has been the filler of choice. Today, advanced Boron Nitride filled epoxies challenge alternative thermal interface materials like silicones, greases, tapes, or pads. The paper discusses key attributes for designing and formulating advanced thermally conductive epoxies. Comparisons to other common fillers used in packaging are made. The filler size, shape and distribution, as well as concentration in the resin, will determine the adhesive viscosity and rheology. Correlation's between Thermal Resistance calculations and adhesive viscosity are made. Examples are shown that determination of thermal conductivity values in "bulk" form, do not translate into actual package thermal resistance. Four commercially available thermally conductive adhesives were obtained for the study. Adhesives were screened by shear strength measurements, Thermal Cycling ( -55 °C to 125 °C ) Resistance, and damp heat ( 85 °C / 85 %RH ) resistance. The results indicate that low modulus Boron Nitride filled epoxies are superior in formulation and design. Careful selection of stress relief agents, filler morphology, and concentration levels are critical choices the skilled formulator must make. The advantages and limitations of each are discussed and demonstrated.
