Sn3Ag0.5Cu (SAC305)is the major solder alloy after RoHS was adopted by the European Union. Since its melting temperature is relatively higher than eutectic SnPb alloy, the peak reflow temperature increases. This transformation in the assembly industry impacts the component requirement, where the deformation probability (warpage) of a flat component is increased, which impacts the production yield. A lead-free, low-temperature SMT solder is needed to resolve this dilemma.

Low-temperature SMT assembly refers to the reflow process with a peak temperature less than 200°C. The new process provides a few advantages like reducing energy consumption, reducing BGA component warpage during reflow and diminishing non-wetting open (NWO) and head-on-pillow (HoP) defects. The SnBi alloy is one of the candidates used in low-temperature SMT assembly. However, the brittle mechanical property of conventional SnBi alloys will degrade the reliability of the assembly. The SnBi alloy properties can be altered via several means.

In this paper, the roles of additive and bismuth content will be discussed. Eutectic SnBi and three newly designed SnBi-based alloys (Sn57Bi1AgX, Sn48Bi1AgX and Sn40Bi1AgX, X represents <0.5wt.%of additive element) were experimented upon. Solder pastes that were blended with the aforementioned alloys and flux were used to assemble on the PCB with BGA components that have SAC305 solder spheres pre-mounted. The same reflow profile was used for all pastes. Cross-sectional analysis, shear testing, drop testing and thermal cycling testing were conducted to determine the microstructure, shear force, drop reliability and thermal reliability. The results show that the microstructure, especially the bismuth-rich phase, became finer and the shear force was elevated when the additive was added. On the other hand, the drop reliability improved with decreasing bismuth content, and the thermal reliability improved with increasing bismuth content.

The world as we know it is changing. Electronic megatrends are impacting the world and rapidly changing the way we experience day-to-day life. The imminent 5Gwireless infrastructure will be a critical enabler for so many electronics megatrends, including autonomous vehicles, the Internet of Things (IoT), big data storage farms, artificial intelligence (AI)and AR/VR.5Gisalsoprojected to deliver faster data rates at 100Xhigher frequencies and with over 1000X more data traffic and will require novel manufacturing solutions for mm Wave length signals, and far higher levels of signal integrity and impedance control than ever before.  The major trends that are driving more accurate, efficient and smart production equipment are smartphones, automotive, 5G, data storage, and Industry 4.0.

This paper highlights changes in PCB technologies such as advanced high-density interconnect (HDI)PCBs–also referred to as Substrate-Like PCB–and flex PCBs, and the need to focus on tighter impedance control for mm Wave signals and production data traceability and analysis.  All of these industry trends have generated the need for new PCB production solutions focused on inspection, measurement, metrology and data traceability and analysis.

This paper presents assembly challenges of mixed area array technologies covering Very Thin ChipArray® Ball Grid Array (CVBGA) and its Land Grid Array version (CV-LGA), embedded Wafer Level Land Grid Array (eWLP-LGA), and Copper-Pillar Flip-Chip (CP-FC) die—all with daisy-chain patterns to enable thermal cycle reliability monitoring for solder-joint failure evaluation. Twenty-seven (27) PCBs were assembled with a large number of variables in the design of experiment (DOE) to address: (1) assembly of mixed die and die-size array, (2) the effect of daisy-chain patterns on top layer or second layer bymicrovia-in-pad connections, (3) the effect of underfilling on improving resistance to thermal cycling, (4) challenges of single--and double-sided assembly processes, and (5) the effect of double-sided assembly on thermal cycle reliability. Acceptable assemblies with and without underfill were subjected to thermal cycling between –40°C and 125°C for solder-joint reliability characterization and failure-mechanism assessments. The paper will present details of DOE assembly parameters with the status of thermal cycle evaluation.

KEY WORDS: ball grid array, BGA, chip array BGA, embedded wafer level package, eWLP, land grid array, LGA,

Board level reliability testing is becoming a requirement amongst users for acceptance of components and packages. Standard component level JEDEC tests are not sufficient to qualify a supplier, this must be accompanied with board level reliability data to ensure assembly and field reliability. The paper presents a summary of board level reliability test performed on RF packages, the assembly process controls and monitoring, mechanical and environmental reliability tests, understanding of failure modes and lessons learned.

In recent years there has been an increased demand for electronic products with high reliability solder alloys having improved performance in thermal cycle resistance for harsh working environments. Traditional thermal cycling tests have used 40°C to +125°C for automotive type applications. There has been an increased focus on increasing temperature cycling test range to a higher temperature to account for increased product temperatures in the field. The work discusses thermal cycling results from -40°C to +150°C for soldered QFN/BTC and chip components with lead-free Sn3.5Ag0.5Bi6In0.8Cu (SABIX) and Sn3Ag0.5Cu solder alloys and ageing results at 150°C.

Reliability tests were undertaken by Thermal Cycling (-40°C to +150°C, 3,000 cycles) and Shear Strength testing with analysis of the amount of solder joint micro-cracking during thermal cycling. Thermal ageing tests were also undertaken at 150°C for 32 days (768 hours) for soldered chip components with Shear Strength testing during the thermal ageing tests and microstructural analysis. Cross-sectional and EBSD (Electron Back Scattered Diffraction) analysis were also undertaken on as-received (Time zero) and thermally cycled soldered chip component boards.

Tests done with the no-clean lead-free high reliability alloy (Sn3.5Ag0.8Cu0.5Bi6In (SABIX)) paste included Printability, Viscosity, Wetting and Void Occurrence after reflow for Power Transistor/BTC, BGA and chip components and Electrical ECM reliability. The results of the work are reported.

Keywords: Thermal cycling, high reliability alloy, ageing, shear testing, cross-sectioning, lead-free

Advanced Packaging is one of the key growing segments with high adoption rates and strong technology advantages and offersa pathway moving forward to support industry roadmaps. Sputtered seed layers – replacing chemical seed layers – are opening up a whole new range of possibilities, thus both OEM and manufacturers of next generation IC Substrate and Substrate-like PCBs are implementing sputtered seed layer as an enabling technology for smaller and more precise structures and improved reliability. Integrating new materials into packages – such as glass core with Through Glass Via (TGV) – and developing the next generation of Chiplet-Packages are interesting challenges that lay ahead.

Processing substrates with high organic load requires distinct process capabilities and well aligned process steps. This paper explains the most important do’s and don'ts for vacuum processing of organic substrates and its impact on the final devices.

PCB (Printed Circuit Board) and CCL (Copper Clad Laminates) industries are facing environmental issues and cost reduction challenges. Consumable release sheets are an important aid for many demanding lamination processes of those industries. Today, the release sheet market is exclusively composed of plastic films which are not environmentally sustainable. In addition, standard plastic films become brittle and difficult to manipulate at temperatures above 200°C; a temperature often required for the PCB and CCL pressing processes. In close collaboration with various stakeholders of the value chain in this market the authors’ companies harnessed their combined expertise in natural fibers, the Genuine Vegetable Parchment Technology, lamination and prototyping to create a new kind of lamination processing aid that rises up to the sustainable challenges of the PCB and CCL pressing industry.

The objectives of this partnership were to create a disruptive innovation leading to a greener alternative to the standard plastic release films at a lower cost. Last, but not least, the goal of this study was to determine if the sustainable release sheet developed could replace the traditional plastic release film used during the lamination step without any compromise on the process and the PCB performance.

This technical paper will detail the different tests and methodologies developed to ensure the performance of the release aid for the pressing of highly technical PCB components; including pressure and temperature test qualification with several types of base materials in a vacuum press but also the final performance check with visual inspection and mandatory quality control of the final PCB.

Ultimately, each step of the IPC-Class II Rigid PCB production was evaluated and benchmarked to make sure the new release aid delivers the same protection and performance as the current PE release film.

Wireless wearable devices can continuously assess and communicate the condition of patients and are crucial components of digital mobile health platforms. General societal trends across the globe, including a shortage of centralized laboratory and medical facilities, aging populations with increasing incidence of infectious and chronic diseases, earlier diagnosis of diseases, personalized medicine, companion testing for pharmaceutical use, government initiatives and insurance acceptance, are all important factors behind the demand for reliable, low-cost, wireless, wearable health monitoring devices. Fortunately, technological building blocks for implementation of these devices have evolved to the point that we believe that such monitoring will progress into a fully mobile approach in the near future, enabling continuous monitoring across acute, ambulatory and home care. In the past decade, a number of wireless physiological monitoring devices have been developed and tested in various clinical settings and a few of them are at early stages of product release. Furthermore, in 2020, due to the unprecedented circumstances of the COVID-19 pandemic, numerous wearable devices were investigated for early infection detection and patient monitoring in hospital and nursing home settings. In spite of this tremendous potential and significant investments by both device developers and government agencies, broad adoption of wearable medical devices has not yet been fully realized. The barriers to broad adoption include device cost and performance challenges, ease of use, integration of devices within the remote care flow system as well as lack of robust reimbursement models. In this paper, we will discuss flexible hybrid electronic manufacturing opportunities and challenges to create low cost, high performance wireless sensor systems for vital signs monitoring. We will highlight the critical need and progress towards enabling the supply chain workflows that allow for sustainable manufacturing solutions at large volumes.

Keywords: Flexible hybrid electronics, continuous vital signs monitoring, on demand interstitial fluid monitoring

To demonstrate the benefits of flexible hybrid technology (FHE) and printed electronics the team of Lockheed Martin Rotary Missions Systems Owego (LMO), Lockheed Martin Space Systems Billerica (LMB) and SUNY Binghamton University (BU) have designed and demonstrated a security RFID tag that utilizes a passive (battery-less) UHF-RFID chip within an FHE structure that contains embedded hardware security features. These features consist of printed high-resistance metal/carbon traces located within the tag substrate that generate a digital identifier for each individual tag. The team utilized LM thin-film security stamp technology to fabricate a multi-layer sensor network and embed anti-tamper/anti-counterfeit features in the substrate that are interrogated during the RFID tag-reader communication. Data is encrypted and stored in the tag and used as key material for the authentication process. In addition, the tag uses an aerosol jet printed optical 2D-barcode matrix printed over the RFID tag such that an external dual-reader (RF and optical) is needed to extract data and then de-encrypt using a secure software algorithm. This report will focus on the overall design and development of the RFID tag, highlighting the benefits of printed and flexible hybrid technology. The RFID tags resistance to different tamper attack vectors (vulnerability assessment) along with proposed refinements will also be shared.

Real-time and in-situ monitoring of the air-quality of confined spaces is a life-saving technology for commercial and government maintenance workers and is conspicuously absent from the commercial market. Existing solutions are not easily worn in confined spaces, lack sensitivity to hazardous gasses, and/or are not intrinsically safe. In response to a particular need by Air Force and Commercial aircraft maintainers, NextFlex has developed wearable chemical sensors which fill this gap. The sensor device detects volatile organic compounds, ambient oxygen level, temperature, and relative humidity. This information is wirelessly transmitted via a printed Bluetooth antenna this so that the worker and their environment can be remotely monitored. Charging and firmware updates are both accomplished wirelessly in the field. The devices are currently fabricated using flexible hybrid electronics approaches including conductors printed onto flexible films via screen printing and off the shelf components placed via standard electronics industry pick-n-place processes. This sensor device is conformal to the wearer and should not interfere with work in confined spaces and is encapsulated with a rugged silicone for protection against liquid and dust ingress. The silicone is applied via a molding process which protects against liquid ingress while allowing air to reach the sensors. This presentation will discuss the design, prototyping, and scale-up efforts on the sensor platform. Special emphasis will be placed on lessons learned in the design and process build up. Intrinsic safety and cybersecurity certification efforts will also be discussed and how they have thus far influenced the design of these low-power wearable sensors.