A.R.E.A. – Component Warpage: Issues with Measurement and Standardization

Miniaturization has been a pivotal trend in the electronics industry since Gordon Moore's prediction of doubling microchip transistor counts every two years. While this trend has driven the development of smaller, lighter electronic devices, recent advancements in semiconductor technology are pushing towards larger and more complex integrated circuit chips. This evolution, necessitated by the need for higher performing semiconductors and enhanced manufacturing processes, introduces significant challenges during reflow attachment to printed circuit boards, particularly concerning component warpage and boards that heat unevenly. Component warpage is a growing challenge when it comes to printed circuit board assembly. Warpage can appear in a “smile, frown, M or W“ shape. Warpage complexity typically increases as component dimensions increase. Warpage during reflow can directly lead to defects such as head-in-pillow (HiP), non-wet opens and bridging. One of the best ways to control, or reduce component warpage is by lowering the peak reflow temperature. Checking the moiré shadow diagram for each component can help ensure that the reflow peak temperature is compatible with the component warpage requirement. The warpage issue extends beyond component size alone; modern circuit boards are also growing in complexity. High-performance IC components require thicker PWB copper traces and take up more board real estate, contributing to densely populated boards with varied component types and shapes. During reflow, these boards often exhibit uneven heating, with standard SAC305 profiles showing temperature differentials ranging from 40-60°C. This temperature variance forces a compromise: while ensuring components with substantial thermal mass reach 240°C, smaller components may inadvertently reach temperatures as high as 300°C. A novel mixed solder powder alloy, referred to as DFLT, has emerged as a crucial solution to these manufacturing complexities. Leveraging advanced alloy technology, DFLT mitigates challenges associated with uneven heating due to varying thermal mass across components. This innovative alloy not only widens the reflow process window, but also can effectively reduce warpage during reflow processes. Moreover, its peak reflow temperature can be 20-40°C lower than SAC305, ensuring quality solder joints without compromising component integrity. In summary, DFLT represents a transformative solution for modern electronics manufacturing, adeptly addressing the intricate demands posed by larger, more complex IC components and high-density circuit boards.

Head-in-pillow (HIP) is ailing the electronic industry when assembling BGAs or CSPs onto PCBs. It is caused by warpage of components or boards at the reflow process, and is aggravated by oxidation. Methods for assessing the potential occurrence of HIP are highly desired by the industry. Besides using BGA rework station, followed by tedious dye and pry treatment, two other simpler methods are introduced in this work - the Tiny Dot Paste method and Ball Onto Paste method. The Tiny Dot Paste method focuses on the assessment of the oxidation barrier capability of solder paste, while the Ball Onto Paste method assesses the combined capability of oxidation resistance and excessive fluxing capacity. Both methods are quick, easy, and close simulation, with the latter being better in real process simulation. Prevention of HIP can be accomplished by (1) designing packages without warpage, (2) printing more paste, (3) using dipping solder paste or flux, (4) using inert reflow atmosphere, (5) reducing the reflow temperature, (6) placing a heat shield on the BGA or CSP, (7) avoiding the use of water-soluble solder paste for BGAs bumped with a no-clean process, (8) using solder bumps or solder powder with an oxidation resistant alloy, (9) using fluxes with a high oxidation barrier capability and high fluxing capacity. Among all the options listed above, using a solder paste with a high oxidation barrier capability and high fluxing capacity is considered to be the most easily implemented approach.

The fair allocation of river pollution assimilation capacity among stakeholders (polluters) is one of the most critical issues in river water quality management. In this study, the bankruptcy rules approach was employed to address this challenge. To this end, the QUAL2Kw water quality simulation model was linked with the particle swarm optimization algorithm, incorporating the four bankruptcy rules [constrained equal awards (CEA), constrained equal loss, proportional (P), and Talmud] as constraints. The objective function of the study is to maintain water quality, measured by biochemical oxygen demand, within standard limits along the river by optimally allocating pollutant loads. The applicability of this method was evaluated in the Abbas-Abad mountainous river, located in a semiarid basin in Iran. The results indicated that, using this modeling approach and based on the bankruptcy rules investigated, river pollution was maintained within standard limits. However, from the perspective of fairness among stakeholders, the P rule appears to be the most equitable, as each point-source polluter discharges a proportionate share of their pollution load into the river. On the other hand, from the perspective of maximizing pollutant discharge while still maintaining water quality standards or, in other words, enhancing the river’s self-purification capacity, the CEA rule is the most effective. This is because it allows for the highest total pollutant discharge, resulting in lower overall treatment costs for polluters and greater reliance on the river’s natural self-purification.

The present study was carried out to assess the drinking water quality, hygiene and human health existing in the city of Jodhpur. About 89.8% of houses use household drinking water from supply, and the remaining 10.2% houses depend on public taps or other water sources. Similar results for sanitation and hygiene observed as 97% of houses did not have any garbage disposal facility and in all 10.6% did not have easy access to a sanitary facility. The results of physical and chemical parameters of ground water were above the drinking water standards, whereas in the case of household drinking water were within standard limits. The presence of total coliform, faecal coliform and faecal streptococci were showing water contamination which may be the cause of significant prevalence 5.0% (p < 0.001) of gastrointestinal infections.

E-Prescribing Collaboration in Massachusetts: Early Experiences from Regional Prescribing Projects

Denitrification of nitrate-contaminated groundwater in an anoxic rotating biological contactor: a case study

Urbanization and industrialization enhance the degradation of the groundwater quality due to the discharge of domestic and industrial effluents in the aquatic bodies or on the surface of ground either in treated or untreated form. Therefore, the present study was carried out to assess the groundwater quality at the Laksar block of district Haridwar in Uttarakhand. Groundwater samples (SS-1-10) were collected from the hand pumps of the study area. The sampling site (SS-1) was taken as control. The distance of all sampling sites from control site ranged from 6.3Km to 18.3Km. The samples were analyzed for various physicochemical parameters viz Temperature, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Total Solids (TS), pH, Dissolved Oxygen (DO), Total Hardness (TH), Calcium Hardness (CaH), Chloride (Cl), Sulphate (SO4--), Nitrate (NO3---), Acidity, and Iron (Fe) for two years (2017 to 2019). The data obtained after analysis was simplified using Water quality index (WQI). The maximum concentration of TDS, TS, TH, CaH, and Fe was observed at SS-6 that may be due to the direct industrial discharge of Sugar mill effluent on the ground. Based on WQI value, SS-6 (WQI value-150.27) was found most polluted site. Hardness was found above the standard limit (250mg/l) at SS-6 to SS-10. The Fe was also found above the standard limit of WHO and BIS (0.3mg/l) at SS-6 to SS-10. The study may be useful for managing the groundwater quality of the study area.

The study presented in this paper is part of a digitization project developed for the University of Padua. It aims at demonstrating how IFC (Internet Foundation Classes) ISO Standard can be used as a reliable data model to support Performance Analysis (PA) and code checking for construction disciplines. Fire Safety Engineering (FSE) is analyzed as a challenging test field because it highly affects different building aspects and highlights interoperability issues. The methodology proposed in the study consists in checking a digital approach to PA based on information classes that can express both users’ requirements and performance specification of technical elements to develop computational code checking. This method is developed by creating virtual classes representing built systems and using relation classes and performance attributes to check if technical elements fulfil users’ requirements. By forcing the model to be based on standardized information classes, the study verifies if IFC, as an ISO standard, can be used as a universal and scalable reference model for performance analysis and code checking. More specifically, the study focuses on the availability of IFC’s information classes and attributes that define a PA model. This research verifies the achievement of the proposed goals for FSE (Section 2) and then highlights the interoperability limits that affect an IFC-based approach to computational FSE code checking (Section 3). Finally, the technical feasibility of the methodology’s market implementation is presented (Section 4). The study’s innovative approach is related to the fact that IFC is often analyzed as an information exchange format, not as a data model, where standardized relations between building ontologies can be simulated. Digital ontologies of relational aspects are experimented with by following this approach. These reports support code conformance analyses of the technical element performance specification. The study then indicates how the information modelling discipline could be shaped to encourage standardized code checking better.

The vadose zone of a trinitrotoluene (TNT) and dinitrotoluene (DNT) contaminated site was investigated to assess the mobility of those explosives under natural conditions. Located in the left margin of the River Tejo Basin, Portugal, the site is located on unconsolidated sediments. Wastewaters associated with the 50-year explosives production were disposed in excavated ponds, from where water would infiltrate and pollute the unsaturated and saturated parts of the local aquifers. Two boreholes were drilled to 9 m depth in such a former waste pond to investigate the contaminant’s fate in the vadose zone. Sediment samples were taken every 1–2 m for analysis of the poly-nitroaromatics (p-NACs) and organic volatile compounds, pH, organic carbon content, cation exchange capacity and grain size analysis. The main contaminant was TNT representing >70 % of the total p-NACs concentration that peaked approximately 7 mg/kg in one borehole, even if the median in both boreholes was of ~1 mg/kg. DNT was 4–30 % of the total p-NACs and nitrotoluene (NT), up to 5 %. No other (volatile) organic compound was detected. The predominance of TNT as the main contaminant implies that any natural mass reduction has been inefficient to clean the site. Several 1-D model simulations of p-NACs cleaning of the vadose zone under natural conditions indicated that the most probable scenario of combined advection and partitioning will only remove TNT after 10’s of years, whereas DNT and NT will hardly be removed. Such low concentrations and long times for the p-NACs removal, suggest that by now those compounds have been washed-out to a level below standard limits.

Ensuring power quality and demand-side management through IoT-based smart meters in a developing country

Coastal contamination became a growing public health concern. Enteric illness outbreaks, and the occurrence of dermatitis and mycoses during the summer season in leisure areas, were usually related to seawater pollution. Pathogenic microorganisms can reach coastal areas through sewage discharges, compromising marine water, and beach quality. Although sand transmission of enteric illness is still unclear, there is an expressed concern that sand may act as reservoirs or vectors for humans infection. In this context, the main hypotheses of this study were: (i) fecal coliforms density changes within beach compartments; (ii) dry sand is the most contaminated beach compartment; (ii) fecal coliforms densities are within international standard limits for sand. Therefore, this case study quantified and compared within three months total fecal bacteria (TC) and thermotolerant coliforms (TEC) densities in seawater, wet, and dry sand of a chosen touristic beach from Rio de Janeiro, Brazil. Furthermore, to contribute to coastal beach management, sand contamination data surveyed were compared with the standard limits ruling worldwide until April 2018 to check suitableness. Vermelha beach should be considered as a reference beach for sand monitoring in Brazil. Despite being a buffer zone from the MONA Pão Açucar conservation unit, it is subjected to intense touristic pressure. Even though, fecal bacteria densities quantified in Vermelha beach were within the standards of “excellent” quality sand and water according to current legislation/guidelines. However, dry sand was the most contaminated compartment, followed by seawater and wet sand. The bacterial density in dry sand was up to 4,600 times higher than wet sand. Except for Rio de Janeiro city, recreational guidelines for beach quality is exclusive for seawater contamination. There are no established parameters for recreational beach sand classification, only recommendations, including Portugal. Monitoring recreational beach dry sand is critical to reducing the risk of beachgoer exposure to pathogens.

For portable and wearable devices, having good functionality and being lightweight are a must. To improve the functionality of the device, System-in-Package (SiP), Package-on-Package (PoP), Multi-Chip-Module (MCM), or Chip-on-Wafer-on-Substrate (CoWoS) are good packaging options. These devices and their printed circuit boards (PCBs) are designed to be thin and lighter for many applications and the severe warpage is one of the serious reliability concerns. The warpage has caused reliability issues such as soldering defects, bridging, stretching, head-in pillow, and non-wet opens. The warpage is caused by the CTE mismatches of the materials under temperature excursion during the manufacturing process of the package. Therefore, a good selection of materials or operating temperatures may help mitigate the deformation. Unfortunately, this type of warpage control is very difficult and complex for SiP, PoP, or McM packages because there are many components to be soldered together using different processing temperatures. To address the serious issue of warpage, we have developed a reflowable jig holder which can hold an array of MCM packages. Our jig holder is different from traditional ones that use end-clamping or only have clamp force in the inactive regions outside the functional package areas. Our reflowable jig holder implements magnets to apply forces on both inactive and active regions. With a Sm-Co magnet inside the reflowable jig at the bottom and a ferromagnetic cover on the top, we were able to better control the warpage. Experimentally, we have designed, fabricated, and tested four different magnetic jigs. Two different magnets having different diameters and weights, and two jigs with different thicknesses and materials were used. The magnetic flux densities and magnetic forces as a function of components’ structure or material were analyzed to optimize the performances. After the manufacturing of the packages with our innovative reflowable magnetic jig, the amount of warpage and shape of the package were inspected by Thermal Shadow Moire (TSM). The integrity of solder joints was inspected by X-ray and cross-section analyses. We have compared the warpage data of the packages using our innovative reflowable jig with those using a traditional reflowable jig. The experimental results show that the number of magnets and their configurations impact not only the local warpage but also the overall warpage. A reflowable jig with stronger magnetic force results in smaller warpage of the package. In conclusion, our innovative magnetic reflowable jig is a good method to control the warpage of these complex packages during the reflow process.

This paper is in English and Chinese languages. There have been many publications, industry workshops, and symposia that describe process mitigation techniques for minimizing the occurrence of Head-on-Pillow (HoP) defects during surface mount assembly. These include inspection effectiveness as covered in Part 1 of this two paper set. This second paper addresses the root cause of the HoP defect; specifically the link between HoP defects and component warpage. Multiple case studies contributed by the participating companies are presented to support the proposal that the current industry warpage standard needs to be revised and to demonstrate that further work is needed by the industry to understand the root cause of this defect better. Based on the data from the case studies, the authors propose revised acceptance criteria that set the maximum warpage at O.090mm (3.5mil) for BGA of O.8mmpitch and above.

Septage comprises the solid and liquid constituents of any primary treatment system, including a Septic Tank. In this study, the wastewater collected from a septic tank is passed through a partially converted anaerobic filter, and a vertical flow constructed wetland (VFCW) before being sent to a soak pit. The main objective of this case study was to check the effectiveness of incorporating a VFCW between a septic tank and a soak pit to bring down the consequences created due to effluent seepage from soak pits to the groundwater. Conventionally, the effluent gets directly passed to soak pits after primary onsite treatment in the septic tank. The soak pit walls made of porous materials allow the gradual seepage of final effluent into the ground, polluting the groundwater reserves. We analyzed the septic tank effluent from 60 households wherein the effluent was let off into the soak pits. The various parameters analyzed with their averages were 393.83 ± 293.41 mg.L-1 for COD, 151.48 ± 94.37 mg.L-1 for BOD, 30.81 ± 13.05 mg.L-1 for NO3-, 23.35 ± 13.54 mg.L-1 for PO43-, 7.35 ± 0.31 for pH, 184.05 ± 163.20 mg.L-1 for TSS, 3.05 x 107± 2.04 x 108 CFU.100mL-1 for TC. Therefore, it is certain that the final effluent being sent into soak pits after primary treatment does not meet the Central Pollution Control Board (CPCB) discharge standards. In this case study, we were able to obtain final effluent values after VFCW treatment as 55.72 mg.L-1 for COD, 12.12 mg.L-1 for BOD, 10.2 mg.L-1 for NO3-, 3.74 mg.L-1 for PO43-, 7.41 for pH, 8.37 mg.L-1 for TSS, 379.27 mg.L-1 for TS and 51.9 CFU.100mL-1 for TC. With this case study, we were able to resolve this impediment by bringing down the values of all the parameters considered while analyzing under the limits of discharge standards set by CPCB. The removal efficiency of COD, BOD, NO3-, PO43-, pH, TSS, and TC after wetland was found to be 89.46%, 88.051, 63.484, 44.37%, 3.41%, 98.47%, 97.71%, 97.19% respectively. The study has proven that with the introduction of another decentralized treatment system between a septic tank and soak pit, it is safe to dispose of the effluent into soak pits, thereby reducing the chances of groundwater pollution considerably.

Effect of strain path change on formability and microstructural characteristics of AZ31B automotive magnesium sheet material is studied at 300°C. The standard forming tests are carried out using Nakazima tests within the environmental chamber. The strain path change tests are performed by in-plane uniaxial, plane strain and balanced biaxial pre-strained specimens in the first stage and Nakazima test in the second stage. The enhancement in the activity of prismatic and pyramidal <c + a> slip as well as a reduction in material anisotropy with increase in temperature is responsible for improvements in formability. Compared to the standard FLD, all uniaxial, plane strain, and balanced biaxial pre-strained materials exhibit higher limit strains. This rise in FLD also incorporates the effect of additional annealing during temperature rise period prior to testing which cannot be avoided with the present experimental set-up and test methodology. The pre-strain effect is reduced by additional annealing effect caused by elevated temperature soaking time. At 300°C, the pre-strained material is almost fully recovered and behaves as the as-received material. Also, significant dynamic recrystallization is observed at 300°C.