Fabrication and Reliability Assessment of Cu Pillar Micro-bumps with Printed Polymer Cores

Cu pillar micro-bumps with polymer cores have been demonstrated to effectively reduce thermomechanical stress and improve joint reliability. Fabricating polymer cores by a printing approach was proposed to overcome the limitations in conventional fabrication process. Cylindrical polymer cores with diameter of 20 µm and height of 30 µm were successfully printed. Surface metallization was subsequently applied on the printed polymer cores and Cu pillar micro-bumps with printed polymer cores with diameter of 35 µm and height of 35 µm were eventually achieved. To study the reliability performance of the interconnect joints made of Cu pillar micro-bumps with printed polymer cores, flip-chip bonding technology was successfully introduced and the interconnect joints between a designed BT substrate and a silicon chip were formed. The interconnect joints made of conventional Cu pillars with identical dimensions were prepared for comparison. The reliability performance of the joints was investigated under temperature cycling condition and drop condition, respectively. Printed polymer cores increased the characteristic life by 32% in a temperature cycling test (0°C-100°C), while the drop test showed that printed polymer cores increased the characteristic life by 4 times due to the extra compliance provided by the printed polymer cores. It can be concluded that Cu pillar micro-bumps with printed polymer cores can effectively reduce stress and improve joint reliability.

Possible health impacts due to animal and human fecal pollution in water intended for drinking water supply of Rio de Janeiro, Brazil

Fecal matter is considered as one of the worst pollutants in waterbodies due to the potential spread of waterborne diseases. This study aimed to determine the host-specific fecal contamination in two Brazilian watersheds and to predict the possible impacts on human health. Fecal sources were enumerated using host-specific genetic markers to swine (16S rRNA), human and bovine (archaeal nifH), and equine (archaeal mcrA). A single cycling condition was established for four markers aiming to decrease the analysis time. Fifteen samples from São João watershed (75%) and 25 from Guandu (62.5%) presenting Escherichia coli enumeration in compliance with Brazilian guidelines (<1,000 MPN/100 mL) showed the human marker. Furthermore, the bovine, swine, and equine markers were present in 92% (59/64), 89% (57/64), and 81% (52/64) of the water samples, respectively. The molecular markers proposed for qPCR in our study were sensitivity and specific enough to detect host-specific fecal pollution in all samples regardless of E. coli levels reaffirming the low correlation among them and supporting their use in water quality monitoring programs. To our knowledge, this is the first study using this approach for quantification of nifH, mcrA, and rrs gene-associated human and animal fecal pollution in waters intended for drinking water supply in Brazil.

Analyzing and Eliminating Die Passivation Crack in a Power Leadframe Package using Submodeling Approach

This paper presents the submodeling approach in thermo-mechanical simulation of the die passivation crack encountered in a power leadframe package subjected to temperature cycling condition. Without using modeling and simulation in resolving semiconductor package development issues, the process would be very costly and time-consuming. For die passivation crack, the details of the different layers of the die passivation need to be modeled and this would result in a large simulation model with considerable solution time. However, a technique known as submodeling can be used to reduce solution time without sacrificing accuracy of results. In this study, submodeling was successfully used to analyze the stresses in the critical passivation layer that resulted in the best design that eliminated the passivation crack. The modeling result showed that the crack could be eliminated by using the right passivation material layer combination and thickness. An increase in the thickness of the material layers and the additional of sublayers have provided significant stress reduction in the topmost critical passivation layer resulting in crack elimination.

Recent Advances and Trends in Fan-Out Wafer/Panel-Level Packaging

The recent advances and trends in fan-out wafer/panel-level packaging (FOW/PLP) are presented in this study. Emphasis is placed on: (A) the package formations such as (a) chip first and die face-up, (b) chip first and die face-down, and (c) chip last or redistribution layer (RDL)-first; (B) the RDL fabrications such as (a) organic RDLs, (b) inorganic RDLs, (c) hybrid RDLs, and (d) laser direct imaging (LDI)/printed circuit board (PCB) Cu platting and etching RDLs; (C) warpage; (D) thermal performance; (E) the temporary wafer versus panel carriers; and (F) the reliability of packages on PCBs subjected to thermal cycling condition. Some opportunities for FOW/PLP will be presented.

Executive Function Performance in Young Adults When Cycling at an Active Workstation: An fNIRS Study

Background: This study aimed to investigate the effects of self-paced cycling at an active workstation on executive functions and cortical activity. Methods: In a crossover study design, 37 young adults (45.9% females) were randomly assigned to the following two task conditions: (1) performing cognitive tests during sitting, (2) performing cognitive tests while cycling at an active workstation. Executive functions were assessed by the Stroop color and word test and the task-switching paradigm. Cortical activity was monitored using a multi-channel functional near-infrared spectroscopy (fNIRS) system. Results: The behavioral results showed that there were no significant differences on the Stroop interference effects (P = 0.66) between the sitting and the cycling conditions. In all probability, no differences on the global switch costs (P = 0.90) and local switch costs (P = 0.67) were observed between the sitting and the cycling conditions. For the fNIRS results, the oxygenated hemoglobin (oxy-Hb) in response to the Stroop interference in channels 5, 10, and 12 were decreased during the cycling condition (all Ps < 0.05, FDR-corrected). Conversely, the oxy-Hb associated with the global switch costs in channels 3, 29, and 31 were increased during the cycling condition (all Ps < 0.05, FDR-corrected). Conclusions: The findings indicated that behavioral performances on executive functions were not affected by cycling at an active workstation, while cognitive resources were reallocated during cycling at an active workstation.