Contrast Inversions in Scanning Acoustic Microscopy (C-SAM) of Glue Die-Attach

2000 ◽  
Author(s):  
Boris Plikat
Keyword(s):  
Electrical Transport ◽  
General Rule ◽  
Acoustic Microscopy ◽  
Frequency Variation ◽  
Lead Frame ◽  
Power Devices ◽  
Layer Model ◽  
Die Attach ◽  
Almost All

Abstract The quality of the die attach is crucial for almost all power devices, as in most cases thermal and electrical transport is vertical through the die and its backside. For glue inspection, C-SAM through the lead frame is widely used. Ordinarily, one of the three following states of delamination is found: (A) no delamination, (B) delamination at the die, or (C) delamination at the lead frame. A general rule for the assignment of the brightness in C-SAM amplitude images to these states of delamination cannot be given. This is evidenced by contrast inversions observed with frequency variation of the applied ultrasound or variation of the glue thickness. Contrast inversions at images through the lead frame occur between areas of states (A) and (B). The calculation of ultrasonic echoes for a three-layer model (copper, glue, silicon) shows that the contrast inversions are connected to the first resonance of the glue in state (B). Here complicated shapes of the echoes are found in experiments and calculations, which helps to correctly assign brightness levels to delamination states. Additionally a flow for reliable glue investigation with the use of through-transmission SAM inspection is proposed.

Evaluation of Low Cost, High Temperature Die and Substrate Attach Materials for Silicon Carbide (SiC) Power Modules

2018 ◽  
Vol 2018 (1) ◽  
pp. 000317-000325
Author(s):  
Sayan Seal ◽  
Brandon Passmore ◽  
Brice McPherson
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Operating Conditions ◽  
Acoustic Microscopy ◽  
Switching Frequency ◽  
Power Devices ◽  
Formidable Challenge ◽  
Die Attach ◽  
Power Modules ◽  
High Switching Frequency

Abstract The performance of SiC power devices has demonstrated superior characteristics as compared to conventional Silicon (Si) devices. Some of the advantages of SiC power devices over Si include higher voltage blocking capability, low specific on-resistance, high switching frequency, high temperature operation, and high power density. Thus, SiC modules are capable of processing significant levels of power within much smaller volumes compared with its Si counterparts. These high thermal loads present a formidable challenge in integrating SiC devices in power modules. For example, known-good materials and processes for silicon power modules are not rated at the aggressive operating conditions associated with SiC devices. Two of the most critical interfaces in a power electronics module are the die-attach and substrate- attach. A degradation in these interfaces often results in potentially catastrophic electrical and thermal failure. Therefore, it is very important to thoroughly evaluate die-attach materials before implementing them in SiC power modules. This paper presents the methodology for the evaluation of die attach materials for SiC power modules. Preforms of a lead-free high-temperature attach material were used to perform a die and substrate attach process on a conventional power module platform. The initial attach quality was inspected using non- destructive methods consisting of acoustic microscopy and x-ray scanning. Die attach and substrate attach voiding of < 5% was obtained indicating a very good attach quality. Cross-sectioning techniques were used to validate the inspection methods. The initial attach strength was measured using pull tests and shear tests. The measurements were repeated at the rated temperature of the module to ensure that the properties did not degrade excessively at the service temperature. At the rated module temperature of 175 °C, the die bonding strength was found to be ~ 75 kg. This was only 25% lower than the strength at room temperature. In addition, the contact pull strength was measured to be > 90 kg at 175 °C, which was 25% lower than the value measured at room temperature. The effect of power cycling and thermal cycling on the quality and strength of the die and substrate attach layers was also investigated.

Physicochemical and bacteriological characterization of hospital effluents and their impact on the environment

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Human Health ◽  
Fecal Coliforms ◽  
Chemical Pollution ◽  
Hospital Effluents ◽  
Biological Contaminants ◽  
Almost All ◽  
Direct Discharge ◽  
Significant Chemical

Liquid effluents discharged by hospitals may contain chemical and biological contaminants whose main source is the different substances used for the treatment of patients. This type of rejection can present a sanitary potentially dangerous risk for human health and can provoke a strong degradation of diverse environmental compartments mainly water and soils. The present study focuses on the quality of the liquid effluents of Hassani Abdelkader’s hospital of Sidi Bel-Abbes (West of Algeria). The results reveal a significant chemical pollution (COD: 879 mgO2/L, BOD5: 850 mgO2/L, NH4+ : 47.9 mg/l, NO2- : 4.2 mg/l, NO3- : 56.8 mg/l with respect to WHO standard of 90 mgO2/L, 30 mgO2/L, 0.5 mg/l, 1 mg/l and 1 mg/l respectively). However, these effluents are biodegradable since the ratio COD/BOD5 do not exceeded the value of 2 in almost all samples. The presence of pathogen germs is put into evidence such as pseudomonas, the clostridium, the staphylococcus, the fecal coliforms and fecal streptococcus. These results show that the direct discharge of these effluents constitutes a major threat to human health and the environment.

Counterfeit Parts Recognition and Detection for Failure Analysts

2010 ◽  
Author(s):  
Katherine V. Whittington
Keyword(s):  
Thermal Cycle ◽  
Visual Inspection ◽  
Acoustic Microscopy ◽  
Scanning Acoustic Microscopy ◽  
3D Measurement ◽  
X Ray ◽  
Wide Range ◽  
Electronic Parts ◽  
Testing Awareness

Abstract The electronics supply chain is being increasingly infiltrated by non-authentic, counterfeit electronic parts, whose use poses a great risk to the integrity and quality of critical hardware. There is a wide range of counterfeit parts such as leads and body molds. The failure analyst has many tools that can be used to investigate counterfeit parts. The key is to follow an investigative path that makes sense for each scenario. External visual inspection is called for whenever the source of supply is questionable. Other methods include use of solvents, 3D measurement, X-ray fluorescence, C-mode scanning acoustic microscopy, thermal cycle testing, burn-in technique, and electrical testing. Awareness, vigilance, and effective investigations are the best defense against the threat of counterfeit parts.

Transformative Learning in Mastery-Oriented CS0 Course

2021 ◽  
pp. 234763112110072
Author(s):  
Srinivasan Lakshminarayanan ◽  
N. J. Rao ◽  
G. K. Meghana
Keyword(s):  
Transformative Learning ◽  
First Year ◽  
Guided Discovery ◽  
Engineering Programs ◽  
Transformative Experiences ◽  
Significant Difference ◽  
Cognitive Levels ◽  
Almost All ◽  
Core Course

The introductory programming course, commonly known as CS1 and offered as a core course in the first year in all engineering programs in India, is unique because it can address higher cognitive levels, metacognition and some aspects of the affective domain. It can provide much needed transformative experiences to students coming from a system of school education that is dominantly performance-driven. Unfortunately, the CS1 course, as practiced in almost all engineering programs, is also performance-driven because of a variety of compulsions. This paper suggests that the inclusion of a course CS0 can bring about transformative learning that can potentially make a significant difference in the quality of learning in all subsequent engineering courses. The suggested instruction design of this course takes the advantage of the unique features of a course in programming. The proposed CS0 course uses “extreme apprenticeship” and “guided discovery” methods of instruction. The effectiveness of these instruction methods was established through the use of the thematic analysis, a well-known qualitative research method, and the associated coding of transformative learning experiences and instruction components.

scholarly journals Noise at the time of COVID 19: The impact in some areas in Rome and Milan, Italy

Noise Mapping ◽  
2020 ◽  
Vol 7 (1) ◽  
pp. 248-264
Author(s):  
Rosa Maria Alsina Pagès ◽  
Francesc Alías ◽  
Patrizia Bellucci ◽  
Pier Paolo Cartolano ◽  
Ilaria Coppa ◽  
...  
Keyword(s):  
Sound Pressure ◽  
Traffic Noise ◽  
Motor Vehicles ◽  
Acoustic Environment ◽  
Commercial Activities ◽  
Real Time Traffic ◽  
Italian Regions ◽  
Almost All ◽  
The Impact

AbstractThe COVID-19 pandemic was confirmed in Italy at the end of January 2020, when the first positive cases for the virus were identified. At the beginning of March, the virus had spread to all Italian regions and on 10 March 2020 the lockdown phase began, limiting the movement of people and prohibiting almost all commercial activities, businesses and non-essential industries. As a result, millions of people were forced to stay at home, causing a drastic drop in traffic volume, which significantly changed the acoustic environment and air quality of cities. On 4 May 2020, the lockdown was partially lifted and activities were progressively reopened. Therefore, traffic gradually started to increase and, consequently, the noise emitted by motor vehicles. This behaviour was confirmed by the data collected by the DYNAMAP system, an automatic platform developed within the LIFE DYNAMAP project, providing real time traffic noise maps in terms of sound pressure levels and impacts at receivers (people and dwellings exposed to noise level bands). In this paper traffic and non-traffic-related noise events in the cities of Rome and Milan from March to May 2020 are analysed and compared to the corresponding values in 2019 to evaluate the effects of the lockdown period.

scholarly journals Research Regarding the Quality of Lambs Carcass Resulted from Tsigaia Purebred Compared with Hybrids of Tsigaia Ewes Crossed with Blanc du Massif Central Rams

2017 ◽  
Vol 74 (1) ◽  
pp. 7
Author(s):  
Mihai Marian BORZAN ◽  
Dana PUSTA ◽  
Liviu BOGDAN ◽  
Alexandra TABARAN ◽  
Attila MATE ◽  
...  
Keyword(s):  
Body Weight ◽  
Chemical Composition ◽  
Massif Central ◽  
Live Body Weight ◽  
Almost All ◽  
Qualitative Characteristics

Abstract: The research aims to compare some qualitative characteristics of purebred Tsigaia lambs and Tsigaia crossed with Blanc du Massif Central lambs. The criteria assessed were: chemical composition of purebred and Tsigaia crossed meat, the live body weight, the slaughtering performance, the weight of different carcass cut. For almost all criteria chosen the crossed individuals registered better results.

scholarly journals Impact of Demerger on Shareholders’ Wealth

2009 ◽  
Vol 1 (1) ◽  
Author(s):  
Ranjit SINGH ◽  
Amalesh BHOWAL ◽  
Varun BAWARI
Keyword(s):  
Value Creation ◽  
Stock Exchange ◽  
Specific Character ◽  
Average Price ◽  
Share Prices ◽  
The Subject ◽  
Time Specific ◽  
Almost All ◽  
Total Wealth

Purpose – The purpose of this paper is to investigate the change in the level of the wealth of the shareholders’ before the demerger and after the demerger.Design/methodology/approach – In the present study the data relating to share prices has been taken from the official website of Bombay Stock Exchange. Here the average of the six months price of the demerged company before demerger and average six months price or the average price upto 31st of July, 2007 has been collected of demerged and resultant company after demerger. Findings – It is found that after demerger there is increase in the total wealth of the shareholders in almost all the cases.Research limitations/implications – Given the nature of this study, generalizations cannot be made as the study is conducted in a bullish market. The time specific character of the subject matter is an opportunity for future longitudinal research.Practical implications – Presently de-mergers are creating enormous wealth for shareholders. It is because of the negative synergy. Due to the demerger this negative synergy is removed and the value is unlocked. However, Investors should differentiate between genuine attempts at value creation and de-mergers undertaken to create hype around the stocks. Stay away from dubious companies that want to manipulate prices. Investors should focus on the quality of management and corporate governance record of the companyOriginality/value – The study is the first of its kind and hence original in nature.Article Type: Research paperKeyword(s): Demerger, Demerged Company, Resultant Company, Negative Synergy, Shareholders Wealth.

scholarly journals Teledermatology in Times of COVID-19 Confinement: Comparing Patients’ and Physicians’ Satisfaction by the Standardized Brest Teledermatology Questionnaire

Dermatology ◽  
2021 ◽  
pp. 1-6
Author(s):  
Joachim W. Fluhr ◽  
Annie Gueguen ◽  
Delphine Legoupil ◽  
Emilie Brenaut ◽  
Claire Abasq ◽  
...  
Keyword(s):  
Main Question ◽  
Chronic Patients ◽  
Dermatology Department ◽  
Global Satisfaction ◽  
Technical Parameters ◽  
Face To Face ◽  
Almost All ◽  
Outpatient Settings

The French government imposed the first COVID-19 pandemic lockdown from March 17 until May 11, 2020. Only emergency cases and teledermatology (TD) were allowed in outpatient settings. A standardized questionnaire was developed to compare the satisfaction level of patients and their treating physicians. Our main question was whether the patients would perceive TD as a valid alternative for direct physical face-to-face consultation. Eighty-two patients and their 4 treating dermatologists from one dermatology department participated in the study (43 females, 39 males) with a mean age of 46.6 years (SD ±23.9). The reason for TD was a chronic disease in the majority (87.8%), and mainly as a follow-up (96.3%). Regarding satisfaction, almost all categories rated around 9 on a 0–10 verbal analogue scale. The same level of global satisfaction could be seen between the patients and the physicians as well as for the quality of the patient-physician relation and whether all questions could be addressed during the TC. Physicians showed significantly higher scores than patients only for the category of “length” of the consultation. Gender, age, as well as distance between the clinic and home of the patient were not influencing factors for satisfaction. Regarding the technical parameters, the evaluation was mostly comparable for patients and physicians, but overall lower than the relational satisfaction parameters, especially for image quality. Patients were significantly more motivated to continue the TD after the lockdown than their treating dermatologists. We see an interest for implementing TD in specialized centers with chronic patients coming from remote places for regular follow-ups. TD cannot replace in-person patient-physician interaction, but was helpful during the lockdown. As a result, TD might become part of dermatology training to prepare for future lockdown situations.

CUSTOMERS’ PREFERENCE FOR E – BANKING SERVICES: A CASE STUDY OF SELECTED BANKS IN SIERRA LEONE

2011 ◽  
Vol 01 (04) ◽  
pp. 108-116
Author(s):  
R. A. GBADEYAN ◽  
O. O. AKINYOSOYE GBONDA
Keyword(s):  
Sierra Leone ◽  
Software Verification ◽  
Banking Industry ◽  
Online Banking ◽  
Chi Square ◽  
Frequent Change ◽  
Banking Services ◽  
Chi Square Analysis ◽  
Almost All

The development and the increasing progress that is being experienced in the Information and Communication Technology have brought about a lot of changes in almost all facets of life. In the Banking Industry, it has been in the form of online banking, which is now replacing the traditional banking practice. Online banking has a lot of benefits which add value to customers’ satisfaction in terms of better quality of service offerings and at the same time enable the banks gain more competitive advantage over other competitors. There are some associated risks identified in the study that seem to hinder the success of e-banking services and thus constitute major concern to both financial institutions and customers. This paper therefore, examines, if customers’ choice of banks is influenced by the quality of e–banking services provided. Stratified sampling was used; while the survey Instrument was a developed Questionnaire comprising open ended and Likert type of questions. The Likert type questions have a 4 point scale (indicating 1 = very comfortable and 4 = uncomfortable) divided into two (2) sections: personal details and customers’ e-banking preference in Sierra Leone. The instrument contained 36 items and was administered to about 400 respondents, while 360 completed and returned their Questionnaire. The statistical techniques used for the analysis were the Chi–Square and correlation. The Chi–Square analysis revealed that the quality of e–banking services offered by banks have significant influence on their customers at 95%, 3 degree of freedom. The paper recommends that various measures should be put in place to ensure more security such as installation of encrypted software, verification system of customer’s identification cards, frequent change of password, examining test questions and using mixed password such as the use of alphanumeric amongst others. The paper concludes that e –banking has become important phenomenon in the banking industry and it will continue as more progress and innovations are made in information technology.

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