Electronics Manufacturing Technical Articles

Material & Process Influences on Conductive Anodic Filamentation (CAF)

Mar 16, 2023 | Alun Morgan and Doug Trobough

HISTORY: * In the late 1970s an abrupt unpredictable loss of insulation resistance was observed in PCBs, which were subject to hostile climatic conditions of high relative humidity and temperature while having an applied voltage. * The loss of resistance, even leading to a short circuit was observed to be due to the growth of a subsurface filament from the anode to the cathode. * The term "Conductive Anodic Filamentation" (CAF) was coined....

Publisher: Isola Group

Conductive Anodic Filament (CAF) Formation: A Potential Reliability Problem for Fine-Line Circuits

Mar 16, 2023 | Laura J. Turbini, W. Jud Ready & Brian A. Smith

Outline * Introduction & Background * Factors Affecting CAF Formation * CAF Formation ** Catastrophic Field Failure of Military Hardware ** Laboratory Experiments * Conclusion...

Publisher: Georgia Institute of Technology

Conductive Anodic Filament Failure: A Materials Perspective

Mar 16, 2023 | Laura J. Turbini and W. Jud Ready

Conductive anodic filament (CAF) formation was first reported in 1976.1 This electrochemical failure mode of electronic substrates involves the growth of a copper containing filament subsurface along the epoxy-glass interface, from anode to cathode. Despite the projected lifetime reduction due to CAF, field failures were not identified in the 1980s. Recently, however, field failures of critical equipment have been reported.2 A thorough understanding of the nature of CAF is needed in order to prevent this catastrophic failure from affecting electronic assemblies in the future. Such an understanding requires a comprehensive evaluation of the factors that enhance CAF formation. These factors can be grouped into two types: (1) internal variables and (2) external influences. Internal variables include the composition of the circuit board material, and the conductor metallization and configuration (i.e. via to via, via to surface conductor or surface conductors to surface conductors). External influences can be due to (1) production and (2) storage and use. During production, the flux or hot air solder leveling (HASL) fluid choice, number and severity of temperature cycles, and the method of cleaning may influence CAF resistance. During storage and use, the principal concern is moisture uptake resulting from the ambient humidity. This paper will report on the relationship between these various factors and the formation of CAF. Specifically, we will explore the influences of printed wiring board (PWB) substrate choice as well as the influence of the soldering flux and HASL fluid choices. Due to the ever-increasing circuit density of electronic assemblies, CAF field failures are expected to increase unless careful attention is focused on material and processing choices....

Publisher: Georgia Institute of Technology

Paper Substrates and Inks for Printed Electronics

Mar 13, 2023 | Laura K. Wood†, Erika Hrehorova, Thomas W. Joyce†, Paul D. Fleming, Margaret Joyce†, Alexandra Pekarovicova and Valery Bliznyuk

The present work explores the effects of paper properties on conventional silver-based conducting inks. The effects of smoothness, relative humidity, porosity, permeability and wettability on electrical properties of silver inks on different paper substrates were studied. Another objective of this work was to prepare and study polyaniline synthesized in the presence of different lignosulfonates....

Publisher: Western Michigan University

Printed Electronics: Manufacturing Technologies and Applications

Mar 13, 2023 | Chuck Zhang

Translational Research in Additive Manufacturing at GTMI * Additive manufacturing/3D printing process and equipment development (e.g., metal, polymer and composites part manufacturing) * Computational modeling and simulation of additive manufacturing/printed electronics processes * Advanced materials development for additive manufacturing/printed electronics * Application development and demonstration of additive manufacturing/printed electronics...

Publisher: Georgia Institute of Technology

Modeling Resistance Increase In A Composite Ink Under Cyclic Loading

Mar 13, 2023 | Q Li, E Chung, A Antoniou and O Pierron

The electrical performance of stretchable electronic inks degrades as they undergo cyclic deformation during use, posing a major challenge to their reliability. The experimental characterization of ink fatigue behavior can be a time-consuming process, and models allowing accurate resistance evolution and life estimates are needed. Here, a model is proposed for determining the electrical resistance evolution during cyclic loading of a screen-printed composite conductive ink. The model relies on two input specimen-characteristic curves, assumes a constant rate of normalized resistance increase for a given strain amplitude, and incorporates the effects of both mean strain and strain amplitude. The model predicts the normalized resistance evolution of a cyclic test with reasonable accuracy. The mean strain effects are secondary compared to strain amplitude, except for large strain amplitudes (>10%) and mean strains (>30%). A trace width effect is found for the fatigue behavior of 1 mm vs 2 mm wide specimens. The input specimen-characteristic curves are trace-width dependent, and the model predicts a decrease in Nf by a factor of up to 2 for the narrower trace width, in agreement with the experimental results. Two different methods are investigated to generate the rate of normalized resistance increase curves: uninterrupted fatigue tests (requiring ∼6–7 cyclic tests), and a single interrupted cyclic test (requiring only one specimen tested at progressively higher strain amplitude values). The results suggest that the initial decrease in normalized resistance rate only occurs for specimens with no prior loading. The minimum-rate curve is therefore recommended for more accurate fatigue estimates....

Publisher: Georgia Institute of Technology

An Introduction To The Process Of Printed Electronics

Mar 13, 2023 | S.G.R. Avuthu, Ph.D., M. Gill, N Ghalib, M. Sussman, G. Wable, J. Richstein, Ph.D.

Printed electronics (PE) is impacting almost every branch of manufacturing. The printing of electronics on mechanically flexible substrates such as plastic, paper and textile, using traditional printing techniques, provides novel applications for wearable and stretchable electronics. Government sponsored consortiums, universities, contract printers, startups and global manufacturers are developing processes to bring this technology to market faster, more costeffectively and at scale. By increasing the speed of technology adoption while following industrialization best practices, industry researchers aim to create processes that ramp up the scale of production for simple circuits and integrated conductive structures....

Publisher: Jabil Circuit, Inc.

Printable Electronics: Towards Materials Development And Device Fabrication

Mar 13, 2023 | Rabindra N. Das, How T. Lin, John M. Lauffer and Voya R. Markovich

Purpose – There has been increasing interest in the development of printable electronics to meet the growing demand for low-cost, large-area, miniaturized, flexible and lightweight devices. The purpose of this paper is to discuss the electronic application of novel printable materials. Design/methodology/approach – The paper addresses the utilization of polymer nanocomposites as it relates to printable and flexible technology for electronic packaging. Printable technology such as screen-printing, ink-jet printing, and microcontact printing provides a fully additive, non-contacting deposition method that is suitable for flexible production....

Publisher: i3 Electronics

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Mar 04, 2023 | Management representative

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Publisher: Hiflo Solders Private Limited

PCB terminology you must know

Feb 28, 2023 | FS PCBA

With the popularization of electronic products, more and more people know the importance of printed circuit board (PCB), but it is a very complicated and huge knowledge system. In this article, we will discuss some terms about the PCB industry so that you can better understand the circuit board. Printed circuit board professional noun Array: Usually we also refer to it as panelized, stepped or palletized PCB, which refers to the combination of multiple copies of the PCB into a connected matrix of circuit boards. Usually we refer to the PCB as the bare board of the circuit board, that is, the part that does not contain components, it is not working, and the electronics manufacturer needs to find a suitable PCBA processing plant to complete the assembly after completing the PCB manufacturing. Through the above-mentioned assembly method, PCBA company can complete the assembly work faster. https://www.fs-pcba.com/ Board Aspect Ratio: It is the ratio between board thickness and minimum via diameter, which is very important. We know that a circuit board is an electronic product that contains circuit images, and the circuit diagrams are formed during production through methods such as SUV exposure. In order to ensure the accuracy of circuit images and assembly work, designers need to ensure a lower aspect ratio to reduce potential risks that may arise. Cable: It is used for the transmission of electric current just like the wires in our daily life. There are various wires in electronic products, these wires connect different components, and they are electrically connected to each other to operate. https://www.fs-pcba.com/manufacturing-pcb/ Main body: As mentioned above, the PCB board cannot operate alone, but the components are mounted on the surface of the bare board through PCB assembly. These components are very small, but when they are installed, there are many extra parts such as: pins, leads and accessories. In order to accurately express their views, designers usually use the main body of the component to represent the central part of the electronic component. https://www.fs-pcba.com/assembly-pcb/ More Interesting Board Articles The PCB industry involves a lot of content. In order to complete a complete PCBA board, we need to go through multiple links, such as design, manufacturing, assembly, testing, etc., and there are more categories under each link. If you want to know more about this industry, it will be helpful for you to read more about PCB....

Publisher: FS Technology

Printed Circuit Board (PCB) Micro-Sectioning For Quality Control

Feb 27, 2023 | Nanu Vahora

Quality control in Printed Circuit Board (PCB) manufacturing is very important, including but not limited to drilling hole quality, Desmearing of drilled hole, plating thickness of various metals and integrating of the final production board. During the manufacture of printed circuit boards, test coupons are introduced in each production panel. This allows each panel to be tested without wasting actual production board. The coupon is separated from the panel to confirm product specifications have been met.

Publisher: Buehler, a division of Illinois Tool Works Inc.

ALD Atomic Layer Deposition for space applications

Feb 19, 2023 | Marko Pudas

ALD – Atomic Layer Deposition

- Is a batch coating process with surface chemistry
- Wide range of material, e.g. Al2O3, TiO2, M-, M-C,M-N
- Typical; 100 nm up to ~0,5 μm
- True 3D down to nanopores, no pinholes
- Vacuum deposition process
-- Substrates are degassed & heated (degas analyzed)
-- ~40 C – 125C – 400 C
- Mature IC manufacturing process
- Extremely repeatable in thickness & quality over time
- Chemically adhesion; will not peal off/flak
-- Dense,
-- Pinhole- and defect-free films
-- Digitally repeatable process

Publisher: Picosun Oy

Atomic Layer Deposition (ALD) to Mitigate Tin Whisker Growth and Corrosion Issues on Printed Circuit Board Assemblies

Feb 19, 2023 | TERHO KUTILAINEN, MARKO PUDAS, MARK A. ASHWORTH , TERO LEHTO, LIANG WU, GEOFFREY D. WILCOX, JING WANG, PAUL COLLANDER, and JUSSI HOKKA

This paper presents the results of a research program set up to evaluate atomic layer deposition (ALD) conformal coatings as a method of mitigating the growth of tin whiskers from printed circuit board assemblies. The effect of ALD coating process variables on the ability of the coating to mitigate whisker growth were evaluated. Scanning electron microscopy and optical microscopy were used to evaluate both the size and distribution of tin whiskers and the coating/whisker interactions. Results show that the ALD process can achieve significant reductions in whisker growth and thus offers considerable potential as a reworkable whisker mitigation strategy. The effect of ALD layer thickness on whisker formation was also investigated. Studies indicate that thermal exposure during ALD processing may contribute significantly to the observed whisker mitigation....

Publisher: Poltronic Inc

Investigation of the Atomic Layer Deposition of the Titanium Dioxide (TiO2) Film as pH Sensor Using a Switched Capacitor Amplifier

Feb 19, 2023 | Mozhdeh Nematzadeh , Ola Nilsen , Philipp Dominik Häfliger and Veronica Anne-Line Kathrine Killi

The electrical and chemical properties of the titanium dioxide (TiO2) coated spirals grown by the atomic layer deposition (ALD) technique in two different temperatures of 150 °C and 300 °C are studied. The thickness of the TiO2 layers studied are 20, 40, and 80 nm. A switched capacitor amplifier is used to investigate the pH response and the capacitance of the samples. It is found that the performance of the TiO2 samples depends on either the thickness or the deposition temperature due to the differences in the physical properties of the oxide layer such as surface roughness and film density. The high temperature samples are more crystalline, whereas the low temperature samples are more amorphous. Since there is a low pass filter effect in the electrolyte–sample interface, the TiO2 coated samples show the better response to the pH change for the high temperature samples as the sensor surface area for binding the hydrogen ions is larger and the charge transfer resistance is smaller. Furthermore, more roughness on the surface can be obtained by increasing the thickness, which reduces the charge transfer resistance. In this study, the 80 nm sample deposited at 300 °C gives the best pH response of 40 mV/pH.

Publisher: University of Oslo

Atomic Layer Deposition for Encapsulation and Hermetic Sealing of RF and Power Electronics

Feb 19, 2023 | Forge Nano

Radio frequency (RF) and power electronics are vital to an array of industries, from telecom and consumer electronics to transportation and energy distribution. As energy diversification and the prevalence of high-speed electronics continue to grow, RF and power electronics are expected to reach a global market of $36.6 billion by 2027.1 Extreme environments such as high temperatures, ultra-violet radiation, oxygen, salinity and moisture are all threats that degrade and corrode active components causing early failure. Atomic layer deposition (ALD) has created substantial improvements to the reliability and performance of RF and power electronics. Using ALD as an encapsulation layer at the wafer level or as a final hermetic seal at the chip/module/PCB level has been shown to substantially improve electronic performance and lifetime.2,3 ALD layers enable longer lifetimes, higher performance and lower cost without adding the considerable mass gain and high temperature processing associated with conventional hermetic coatings.

Publisher: Forge Nano

Potting-optimized component design

Feb 15, 2023 | Scheugenpflug

With regard to potting, the design of electronic assemblies and components has a significant impact on economical and sustainable production. Key aspects in this respect are pottability, material use, cycle times, quality and the process technology needed. Optimized, bubble-free potting contributes greatly to the function and longevity of products. It is best practice during the design and development phases therefore to follow the potting tips contained in this White Paper....

Publisher: Scheugenpflug Inc.

Generation of Sn Whiskers During Electrodeposition

Feb 13, 2023 | M. Saitou

Sn whiskers generated during electrodeposition on a Cu plate within a range of the deposition temperature from 273 to 303 K were investigated using scanning electron microscopy and X-ray diffraction. The critical film thickness for the formation of Sn whiskers on a Sn thin film was determined (1.9 um). The critical film thickness was found to be independent of the deposition temperature. At the film thicknesses more than 5 um, the (220) dominant crystallographic plane transformed the (112) plane parallel to the Cu plate. This can be attributed to the morphological change (coarse to dense Sn whiskers). This suggests that the Sn whiskers with the (220) plane acted as crystal seeds to generate the Sn whiskers with the (112) plane. The fine string-like Sn whiskers generated at 303 K during the electrodeposition showed an anomalous growth rate of 45 nm s-1 at least.

Publisher: University of the Ryukyus

Effects of Tin Whisker Formation on Nanocrystalline Copper

Feb 13, 2023 | David M. Lee, Lesly A. Piñol

Spontaneously forming tin whiskers, which emerge unpredictably from pure tin surfaces, have regained prevalence as a topic within the electronics research community. This has resulted from the ROHS-driven conversion to "lead-free" solderable finish processes. Intrinsic stresses (and/or gradients) in plated films are considered to be a primary driving force behind the growth of tin whiskers. This paper compares the formation of tin whiskers on nanocrystalline and conventional polycrystalline copper deposits. Nanocrystalline copper under-metal deposits were investigated, in terms of their ability to mitigate whisker formation, because of their fine grain size and reduced film stress. Pure tin films were deposited using matte and bright electroplating, electroless plating, and electron beam evaporation. The samples were then subjected to thermal cycling conditions in order to expedite whisker growth. The resultant surface morphologies and whisker formations were evaluated....

Publisher: Johns Hopkins Applied Physics Laboratory

DoD/EPA/DOE SERDP WP-2213: Novel Whisker Mitigating Composite Conformal Coat Assessment

Feb 13, 2023 | Dr. Stephan Meschter, Dr. Polina Snugovsky, Dr. Abdullah Ekin, Dale Starkey,Dr. Junghyun Cho

Technology Focus: Develop and evaluate nanoparticle filled conformal coatings designed to provide long term whisker penetration resistance and coverage on tin rich metal surfaces prone to whisker growth in commercial lead-free electronics used in modern DoD systems. Research Objectives: Identify the fundamental mechanisms by which conformal coatings provide long-term tin whisker penetration resistance and inhibit nucleation/growth. Correlate mechanical properties and coverage thickness to whisker penetration resistance. Project Progress and Results: Functionalized nanosilica and non-functional nanoalumina enhanced polyurethane conformal coatings have shown improved spray coating coverage characteristics and crack resistance during thermal cycling fatigue testing. Lead-free assembly whisker mitigation validation testing is in process. Technology Transition: Current project partners provide coating materials to industry. SERDP test data will be considered during updates to the DoD adopted IPC standards for coating materials and coverage....

Publisher: BAE SYSTEMS

Strategies To Mitigate The Tin Whisker Phenomenon

Feb 13, 2023 | Patrick Laver

The tin whisker phenomenon is a failure mode associated with all electronic devices that use a number of low melting point elements (e.g., Sn, Cd, In) in operations such as soldering. Recognized many years ago, the problem was minimized by adding lead, now identified as a hazardous substance and banned...

Publisher: Vicor Corporation

Whisker Formation Induced by Component and Assembly Ionic Contamination

Feb 13, 2023 | POLINA SNUGOVSKY, STEPHAN MESCHTER, ZOHREH BAGHERI, EVA KOSIBA, MARIANNE ROMANSKY, and JEFFREY KENNEDY

This paper describes the results of an intensive whisker formation study on Pb-free assemblies with different levels of cleanliness. Thirteen types of as-received surface-mount and pin-through-hole components were cleaned and intentionally contaminated with solutions containing chloride, sulfate, bromide, and nitrate. Then the parts were assembled on double-sided boards that were also cleaned or intentionally contaminated with three fluxes having different halide contents. The assemblies were subjected to high-temperature/high-humidity testing (85_C/85% RH). Periodic examination found that contamination triggered whisker formation on both exposed tin and solder fillets. Whisker occurrence and parameters depending on the type and level of contamination are discussed. Cross-sections were used to assess the metallurgical aspects of whisker formation and the microstructural changes occurring during corrosion....

Publisher: Celestica Corporation

Via Hole Filling Technology for High Density, High Aspect Ratio Printed Wiring Boards Using a High Tg, low CTE Plugging Paste

Feb 06, 2023 | Michael Carano

The continued fast pace towards miniaturization is leading circuit board designers to push the envelope on integration density. This trend is driving fabricators to closely look at methods and processes that will enable the move towards sequential lamination and blind and buried via technology. Circuit board fabricators particularly in North America are adopting techniques such as via filling capability with nonconductive, high Tg, low CTE plugging pastes. This paper describes the implementation of the via filling process in a highly effective and reliable fashion for high density, high aspect ratio printed wiring boards. Close attention is paid to use of these via filling materials under high temperature assembly conditions. In addition, via plugging material requirements, equipment considerations and process limitations will be presented. Further, the pros and cons of different filling techniques are discussed. Finally, desmear and metallization techniques to insure adhesion of the plating to the filled via are presented in the context of “Best Practices.”

Publisher: Omg Electrochemicals / Macdermid Alpha

PCB Quality Metrics that Drive Reliability

Jan 23, 2023 | Bhanu Sood, Ph.D.

PDC Outline Section 0: Intro Section 1: What is reliability and root cause? Section 2: Overview of failure mechanisms Section 3: Failure analysis techniques – Non-destructive analysis techniques – Destructive analysis – Materials characterization Section 4: Summary and closure...

Publisher: NASA Office Of Safety And Mission Assurance

The Inline X-Ray Component Counter: The Next Step in SMT Inventory Automation

Jan 22, 2023 | Neotel Technology

The inline X-ray component counter, Neo Counter X800, can receive materials from an automated guided vehicle (AGV) or manually loaded by a trolley. The materials are picked up by a robotic arm and sent to the counter for counting. After the counting process, the software records the results and automatically prints a label with the correct quantity. This label is then attached to the surface of the reel. A stacker stacks the materials before being unloaded by the AGV or trolley. This process ensures accurate counting, efficient labelling, and streamlined material handling, making it a convenient way of managing electronic component inventory....

Publisher: Neotel Technology Co., Ltd

Introducing Closed-loop Nitrogen Control To Solder Reflow

Jan 17, 2023 | David Heller

To achieve higher levels of consistency in PCB output, process engineers are able to maintain tighter controls and reduce process-related defects by using closed-loop process controls. At every stage of assembly, from screen printing through placement to reflow, closed-loop systems help control the variable factors that can have adverse effects on the process....

Publisher: Heller Industries Inc.

How Challenging Conventional Wisdom Can Optimize Solder Reflow

Jan 17, 2023 | Marc Peo

As a manufacturing technology, SMT has acquired a "heritage" of widely accepted assumptions about its processes. However, yesterday'spractices are continually confronted by the shifting paradigms of today's production line....

Publisher: Heller Industries Inc.

The User Benefits of a Supplier Partnership

Jan 17, 2023 | Bjorn Dahle, Marc Peo

EQUIPMENT SUPPLIERS HAVE BECOME A RESOURCE FOR PROCESS CONTROL EXPERTISE, EVEN IN THE REFLOW OPERATION....

Publisher: Heller Industries Inc.

Vacuum Fluxless Reflow Technology for Fine Pitch First Level Interconnect Bumping Applications

Jan 17, 2023 | Yue Deng, Xike Zhao, Liang He, David Wright, Hossein Madanipour, Bret Halbe, Jung Kyu, Fred Tarazi, Gang Duan, Dror Trifon, Rahul Manepalli, David Heller

Heterogeneous integration has become an important performance enabler as high-performance computing (HPC) demands continue to rise. The focus to enable heterogeneous integration scaling is to push interconnect density limit with increased bandwidth and improved power efficiency. Many different advanced packaging architectures have been deployed to increase I/O wire / area density for higher data bandwidth requirements, and to enable more effective die disaggregation. Embedded Multi-die Interconnect Bridge (EMIB) technology is an advanced, cost-effective approach to in-package high density interconnect of heterogeneous chips, providing high density I/O, and controlled electrical interconnect paths between multiple dice in a package. In emerging architectures, it is required to scale down the EMIB die bump pitch in order to further increase the die-to-die (D2D) communication bandwidth. Aa a result, bump pitch scaling poses significant challenges in the plated solder bump reflow process, e.g., bump height / coplanarity control, solder wicking control, and bump void control. It's crucial to ensure a high-quality solder bump reflow process to meet the final product reliability requirements. In this paper, a combined formic acid based fluxless and vacuum assisted reflow process is developed for fine pitch plated solder bumping application. A high-volume production (HVM) ready tool has been developed for this process....

Publisher: Heller Industries Inc.

Flux Management

Jan 17, 2023 | Heller Industries

This paper describes the new flux management systems that Heller Industries introduced in 1999....

Publisher: Heller Industries Inc.

Function and Operational Theory of Condenser Tube Flux Collection System

Jan 17, 2023 | Heller Industries

Heller's new Condenser Tube Flux Recovery System is designed to provide more efficient flux collection than earlier Heller flux collection systems; while providing minimal down time for inspection and cleaning. The entire system easily fits within the rear of the top shell of an 1800-EXL oven. The system utilizes a different set of top shell caps specially designed to provide the best serviceability of both the flux collection system and maintenance of the heater zone blower motors....

Publisher: Heller Industries Inc.

Repeatability of the Temperature Profile under Load Variation

Jan 17, 2023 | Prepared by: John Poling

Repeatability of the Temperature Profile under Load Variation...

Publisher: Heller Industries Inc.

Are You Ready for Lead Free

Jan 17, 2023 | Marc Peo & Don DeAngelo

Various international market trends drive electronics manufacturers and their mate- rials and equipment suppliers to develop new assembly techniques to reduce the industry's environmental impact. Two pri- mary forces in this drive are the movements to lead-free assembly and ISO 14000 cer- tification. In response to these factors, reflow technology advances are enabling manufacturers to meet or anticipate the new environmental mandates....

Publisher: Heller Industries Inc.

The Greening of the Reflow Process

Jan 17, 2023 | Atsushi Kikuchi

After years of concentration on resolving productivity- related concerns such as increasing speed, consistency and throughput while reducing costs, many of the world's leading electronics manufacturers have added a new mandate to their agendas. They are seeking to minimize the environmental impacts of their assembly processes and final products without sacrificing the high levels of productivity and quality that have been achieved through decades of effort....

Publisher: Heller Industries Inc.

Let's Get the Lead Out

Jan 17, 2023 | Marc Peo

Let's Get the Lead Out...

Publisher: Heller Industries Inc.

A Practical Investigation into the Use of No Lead Solders for SMT Reflow

Jan 17, 2023 | Heller Industries and Soldering Technology David Heller and Jim Raby

A Practical Investigation into the Use of No Lead Solders for SMT Reflow...

Publisher: Heller Industries Inc.

Effect of Reflow Profile on SnPb and SnAgCu Solder Joint Shear Force

Jan 17, 2023 | Jianbiao Pan , Brian J. Toleno , Tzu-Chien Chou , Wesley J. Dee

Reflow profile has significant impact on solder joint performance because it influences wetting and microstructure of the solder joint. The degree of wetting, the microstructure (in particular the intermetallic layer), and the inherent strength of the solder all factor into the reliability of the solder joint. This paper presents experimental results on the effect of reflow profile on both 63%Sn 37%Pb (SnPb) and 96.5%Sn 3.0%Ag 0.5%Cu (SAC 305) solder joint shear force. Specifically, the effect of the reflow peak temperature and time above solder liquidus temperature are studied. Nine reflow profiles for SAC 305 and nine reflow profiles for SnPb have been developed with three levels of peak temperature (230 o C, 240 o C, and 250 o C for SAC 305; and 195 o C, 205 o C, and 215 o C for SnPb) and three levels of time above solder liquidus temperature (30 sec., 60 sec., and 90 sec.). The shear force data of four different sizes of chip resistors (1206, 0805, 0603, and 0402) are compared across the different profiles. The shear force of the resistors is measured at time 0 (right after assembly). The fracture surfaces have been studied using a scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS)...

Publisher: Heller Industries Inc.

Reflow Techniques for Void Reduction

Jan 17, 2023 | David Heller

BTC Void Reduction For Yield and Performance Enhancement...

Publisher: Heller Industries Inc.

THE LAST WILL AND TESTAMENT OF THE BGA VOID

Jan 17, 2023 | David Hillman, Dave Adams, Tim Pearson, Brad Williams, Brittany Petrick, and Ross Wilcoxon Rockwell Collins. David Bernard, Ph.D., John Travis, Evstatin Krastev, Ph.D., and Vineeth Bastin Nordson DAGE

The impact of voiding on the solder joint integrity of ball grid arrays (BGAs)/chip scale packages (CSPs) can be a topic of lengthy and energetic discussion. Detailed industry investigations have shown that voids have little effect on solder joint integrity unless they fall into specific location/geometry configurations. These investigations have focused on thermal cycle testing at 0°C-100°C, which is typically used to evaluate commercial electronic products. This paper documents an investigation to determine the impact of voids in BGA and CSP components using thermal cycle testing (-55°C to +125°C) in accordance with the IPC- 9701 specification for tin/lead solder alloys. This temperature range is more typical of military and other high performance product use environments. A proposed BGA void requirement revision for the IPC-JSTD-001 specification will be extracted from the results analysis....

Publisher: Heller Industries Inc.

THE EFFECT OF VACUUM REFLOW PROCESSING ON SOLDER JOINT VOIDING AND THERMAL FATIGUE RELIABILITY

Jan 17, 2023 | Richard Coyle, Dave Hillman, Michael Barnes, David Heller, Charmaine Johnson, Richard Popowich, Richard Parker, Keith Howell, Joerg Trodler, Adam Murling

A test program was developed to evaluate the effectiveness of vacuum reflow processing on solder joint voiding and subsequent thermal cycling performance. Area array package test vehicles were assembled using conventional reflow processing and a solder paste that generated substantial void content in the solder joints. Half of the population of test vehicles then were re-processed (reflowed) using vacuum reflow. Transmission x-ray inspection showed a significant reduction in solder voiding after vacuum processing. The solder attachment reliability of the conventional and vacuum reflowed test vehicles was characterized and compared using two different accelerated thermal cycling profiles. The thermal cycling results are discussed in terms of the general impact of voiding on solder thermal fatigue reliability, results from the open literature, and the evolving industry standards for solder voiding. Recommendations are made for further work based on other void reduction methods and additional reliability studies....

Publisher: Heller Industries Inc.

Optimizing Reflowed Solder TIM (sTIMs) Processes for Emerging Heterogeneous Integrated Packages

Jan 17, 2023 | 2022 IEEE 72nd Electronic Components and Technology Conference (ECTC)

Reflowed indium metal has for decades been the standard for solder thermal interface materials (solder TIMs or sTIMs) in most high-performance computing (HPC) TIM1 applications. The IEEE Heterogeneous Integration Thermal roadmap states that new thermal interface materials solutions must provide a path to the successful application of increased total-package die areas up to 100cm2. While GPU architectures are relatively isothermal during usage, CPU hotspots in complex heterogeneously-integrated modules will need to be able to handle heat flux hotspots up to 1000W/cm2 within the next two years. Indium and its alloys are used as reflowed solder thermal interface materials in both CPU and GPU "die to lid/heat spreader" (TIM1) applications. Their high bulk thermal conductivity and proven long-term reliability suit them well for extreme thermomechanical stresses. Voiding is the most important failure mode and has been studied by x-ray. The effects of surface pretreatment, pressure during reflow, solder flux type/fluxless processing, and preform design parameters, such as alloy type, are also examined. The paper includes data on both vacuum and pressure (autoclave) reflow of sTIMs, which is becoming necessary to meet upcoming requirements for ultralow voiding in some instances....

Publisher: Heller Industries Inc.

New Laser-Based PCB Depaneling Method from Coherent Increases Process Utilization

Jan 16, 2023 | Coherent, Inc.

Technological changes in the materials, thickness, and composition of PCBs are motivating a move away from traditional mechanical cutting and depaneling methods towards laser-based processes. But not all lasers for PCB depaneling are created equal. There are significant differences amongst various lasers in cut characteristics and quality, specifically in terms of heat affected zone (HAZ). This, in turn, affects process utilization since it determines how closely circuits can be placed on a PCB, and can also impact circuit functionality and downstream processes like waterproofing or EMI shielding. This document presents a new nanosecond laser and associated cutting process developed at Coherent Inc. which enables laser PCB depaneling with substantially reduced HAZ compared to other currently available products.

Publisher: Coherent, Inc.

LaserFactory: A Laser Cutter-based Electromechanical Assembly and Fabrication Platform to Make Functional Devices & Robots

Jan 16, 2023 | Martin Nisser, Christina Liao, YuChen Chai et al

LaserFactory is an integrated fabrication process that augments a commercially available fabrication machine to support the manufacture of fully functioning devices without human intervention. In addition to creating 2D and 3D mechanical structures, LaserFactory creates conductive circuit traces with arbitrary geometries, picks-and-places electronic and electromechanical components, and solders them in place. To enable this functionality, we make four contributions. First, we build a hardware add-on to the laser cutter head that can deposit silver circuit traces and assemble components. Second, we develop a new method to cure dispensed silver using a CO2 laser. Third, we build a motion-based signaling method that allows our system to be readily integrated with commercial laser cutters. Finally, we provide a design and visualization tool for making functional devices with LaserFactory. Having described the LaserFactory system, we demonstrate how it is used to fabricate devices such as a fully functioning quadcopter and a sensor-equipped wristband. Our evaluation shows that LaserFactory can assemble a variety of differently sized components (up to 65g), that these can be connected by narrow traces (down to 0.75mm) that become highly conductive after laser soldering (3.2Ω/m), and that our accelerationbased sensing scheme works reliably (to 99.5% accuracy).

Publisher: Massachusetts Institute of Technology

Advanced Laser Microfabrication in High Volume Manufacturing

Jan 16, 2023 | John Bickley

There is increased interest in the laser microfabrication of variable shape and size features for a wide variety of materials. Quality and throughput requirements continue to increase, with tighter tolerances regarding dimensional and positional specifications. Consequently, improved laser sources and manufacturing techniques, with advanced system integration and process control need to be developed to be able to address ever increasing industry requirements.

This paper discusses recent advances enabled by a new generation of IPG Photonics fiber lasers that are resulting in systems having greater flexibility, greater reliability and lower operating cost of ownership than their predecessors, and that are producing machining processing rates up to an order of magnitude faster. Examples are given of using high brightness, high pulse energy, pulsed fiber lasers known as quasi continuous wave (QCW) fiber lasers operating in the near infra red (1070 nm) with pulse durations in the micro to millisecond regime, as well as using green (532 nm) fiber lasers in the nanosecond regime. Applications include high speed drilling of ceramics such as alumina and AlN with sub-50um diameter holes machined at 3000, 750 and 300 holes per second in 100, 381 and 635 microns thick substrates, respectively; high speed cutting and scribing of alumina in 381 and 635 microns substrates, high quality cutting of up to 3 mm thick sapphire substrates, as well as high quality cutting & drilling of polymers from PEEK, to silicone, epoxy, and FR4 are presented. Laser machining techniques and their implementation in a new high-volume manufacturing platform are discussed.

Publisher: IPG Photonics World Headquarters

High Phosphorus ENIG – highest resistance against corrosive environment

Jan 10, 2023 | Sven Lamprecht and Petra Backus

Over the past years there has been consistent growth in the use of electroless nickel / immersion gold (ENIG) as a final finish. The finish is now frequently being used for PBGA, CSP, QFP and COB and more recently gathered considerable interest as a low cost under-bump metallization for flip chip bumping application. One of the largest users for this finish has been the telecommunication industry, were millions of square meters of PCBs with ENIG have been successfully used. The nickel layer offers advantages such as multiple soldering cycles and hand reworks without copper dissolution being a factor. The nickel also acts as a reinforcement to improve through-hole and blind micro via thermal integrity. In addition the nickel layer offers advantages such as co-planarity, Al-wire bondability and the use as contact surface for keypads or contact switching. Especially those pads, which are not covered by solder need a protective coating in corrosive environment – such as high humidity or pollutant gas....

Publisher: A.T.E. Solutions, Inc.

Eliminating Ni Corrosion in ENIG/ENEPIG Using Reduction-Assisted Immersion Gold in Place of Standard Immersion Gold

Jan 10, 2023 | George Milad, Jon Bengston and Albin Gruenwald

Nickel corrosion in ENIG and ENEPIG is occasionally reported; when encountered at assembly it manifests as soldering failures in ENIG and wire bond lifts in ENEPIG. Although not common, it can be highly disruptive, resulting in missed deliver schedules, supply chain disruption, failure analysis investigations, and liability - all very costly....

Publisher: Uyemura International Corporation

EFFECTS OF ENIG NICKEL CORROSION ON WETTING BALANCE TEST RESULTS AND INTERMETALLIC FORMATION

Jan 10, 2023 | Donald Gudeczauskas, George Milad

Since the IPC-4552 rev A for ENIG was introduced there have been many requests for clarification of acceptable and unacceptable levels of nickel corrosion. This paper attempts to further clarify the effects of nickel corrosion on solder wetting balance test results and the resultant intermetallic formed. The study will attempt to produce level 1, level 2, and level 3 corrosion as denoted by IPC-4552 rev A and tabulate wetting balance results and congruity of intermetallic formed....

Publisher: Uyemura International Corporation

BLACKPAD REVISITED

Jan 09, 2023 | M. Simard-Normandin, C. Banks

Since the implementation of lead-free soldering, solderability issues appear to have become more common. The higher soldering temperature releases volatiles creating solder voids. The higher temperature also increases board and component flexing. Surface mount components fall off boards and BGA (Ball Grid Array) balls crack cleanly at the intermetallic interface creating open circuits. Black pad is often found as the root cause of these issues. However, black pad is a catch-all expression used to describe a variety of problems. As common as it is, black pad is not always recognised. What does it look like? How can one differentiate black pad from other soldering defects? We present high resolution optical and SEM (Scanning Electron Microscopy) images of real-life soldering problems, demonstrating the difference between black pad issues, flexing issues and component issues, pointing at specific features identifying the syndrome.

Publisher: MuAnalysis

PCB/Substrate Finishing Overview

Jan 06, 2023 | John Swanson

PCB/Substrate Finishing Overview - iNEMI - PCB Surface Finish Overview. Surface Finish deployment ranked by surface area. OSP greatest. Imm Tin. ENIG. Silver. ENEPIG....

Publisher: MacDermid, Inc.

ACHIEVING A SUCCESSFUL ENIG FINISHED PCB UNDER REVISION A OF IPC 4552 MACDERMID ENTHONE

Jan 06, 2023 | Martin Bunce, Lenora Clark, John Swanson

The 4-14 IPC Standards Committee recently created a revision to the IPC4552 specification for Electroless Nickel/Immersion Gold (ENIG) finished Printed Circuit Boards (PCB). Revision A brings a more comprehensive evaluation of metal layer thicknesses measurement, composition and introduces, for the first time, a quality aspect for nickel corrosion which has been historically connected to a defect called black line nickel or black pad....

Publisher: MacDermid, Inc.

Effect of Silver in Common Lead-Free Alloys

Jan 02, 2023 | Ranjit Pandher, Tom Lawlor

Silver bearing alloys have been used in electronics soldering for many years. Silver has been used in tin-lead solders (Sn62Pb36Ag2) to combat silver scavenging from silver plated electronic components as well as to improve thermal fatigue resistance. Many of the common lead-free alloys contain some amount of silver. Silver bearing alloys have good electrical and thermal conductivity as well as the ability to wet to the common surface finishes used in printed wiring assemblies, thus giving it all the attributes needed for an electronic solder alloy. Presence of silver in Sn based solders increases the bulk solder modulus and is generally believed to improve resistance to fatigue from thermal cycles. Increased solder modulus can be advantageous or disadvantageous depending on the desired performance attribute. For example in high strain rate situations, higher modulus of the bulk solders results in lower life time. A wide variety of leaded and lead-free...

Publisher: Cookson Electronics Assembly Materials