Frode Strisland

Wire-bond failure mechanisms in plastic encapsulated microcircuits and ceramic hybrids at high temperatures

Abstract Ceramic hybrids are the preferred solution when long-term high-temperature reliability is required, but standard plastic encapsulated microcircuits (PEMs) are an interesting alternative due to low price and high availability. Test vehicles with standard PEMs were subjected to thermal ageing at 150–175 °C. Six of eight vehicles failed after only three weeks at 175 °C, and the cause of failure was found to be microcracking at the interface between gold ball and aluminium bond pad giving rise to resistance increase. The intermetallic region was formed during high-temperature lead soldering and continued to develop during thermal ageing. The high-temperature performance of aluminium wire bonding to a selection of thick film metallizations on ceramic substrate was also investigated. Gold–palladium has previously been reported as a high-temperature solution, but we found that the mechanical strength of aluminium to gold–palladium (AuPd) degraded seriously at temperatures above 200 °C due to intermetallic formation. Aluminium to silver thick film plated with copper and nickel showed good mechanical strength and unaltered electrical resistance after four weeks thermal ageing at 250 °C.

Vibrational fine structure in the C 1s photoemission spectrum of the methoxy species chemisorbed on Cu(100)

The C 1s photoemission spectrum of methoxy (CH3O) chemisorbed on Cu(100) is demonstrated to contain a resolvable fine structure due to excitation of the molecular C-H normal vibrational mode. The origin of the fine structure is ascertained by substituting hydrogen with deuterium in the methoxy overlayers and by comparison to gas-phase C 1s spectra for methanol (CH3OH). The vibrational fine structure is demonstrated to provide a fingerprint of the hydrocarbon group present on the surface.

Adsorption sites in O and CO coadsorption phases on Rh(111) investigated by high-resolution core-level photoemission

High-resolution core-level spectroscopy is used in combination with low-energy electron diffraction (LEED) and photoelectron diffraction to identify the adsorption sites for three different coadsorbed phases consisting of ordered overlayers of oxygen coadsorbed with CO on the Rh(111) single-crystal surface. The three ordered overlayer structures, which may be denoted as 2O + CO/Rh(111), O + CO/Rh(111) and O+2CO/Rh(111), all show (2 × 2) LEED patterns. In the 2O + CO and O + CO phases the CO molecules are found to occupy only on-top sites while the O + 2CO phase shows CO molecules in both on-top and three-fold hollow sites. In all cases the oxygen atoms are found in three-fold hollow sites. For the O + CO and O + 2CO phases our results confirm previous determinations by LEED, while the 2O + CO phase has not been observed before on Rh(111). The core-level binding energies of the C 1s and O 1s core levels for both adsorbates are characteristics of the adsorption site and are very close to the binding energies found for the pure cases of only oxygen or CO adsorbed on Rh(111). In the coadsorption phases we find that the interaction between the adsorbates has only a minor influence on the core-level binding energies. For the O + 2CO/Rh(111) coadsorption phase we find that a full CO coverage is not obtained; less than 80% of the unit cells contain two CO molecules, in line with previous findings. (Less)

Adsorption properties of a mixed surface studied by high resolution core level photoemission : CO/0.5 ML Pd/Rh(111)

The coverage-dependent adsorption properties of a laterally heterogeneous bimetallic surface have been investigated by high resolution core level photoemission and low energy electron diffraction. The specific system under study was CO adsorbed on a Rh(111) surface onto which 2D Pd islands (coverage 0.5 ML) were formed by vapor deposition. The CO adsorption properties of the heterogeneous surface were compared with CO adsorption on a Rh(111) surface covered with a full Pd monolayer and with previous results for the CO/Rh(111) system. For low exposures CO is only found on the Rh(111) patches which can be explained by diffusion of CO from the Pd islands onto Rh parts in the adsorption process. At higher exposures CO diffusion from Rh to Pd is indicated. The origin of the diffusion processes can be found in the different coverage-dependent CO adsorption energies on the two surface parts.

Adsorption sites in coadsorption systems determined by photoemission spectroscopy: K and CO coadsorbed on Rh(111)

The adsorption sites of coadsorbed K and CO on the Rh(111) surface have been determined using high-resolution core-level spectroscopy, low-energy electron diffraction and site-resolved photoelectron diffraction. For both a (2 × 2)-2CO-1K and a (2√3 × 2√3)-6CO-1K structure, we find that the CO molecules occupy threefold hollow sites and the K atoms on-top sites, contrary to the adsorption sites of K (threefold hollow site) and CO (on-top site below 0.5 monolayers) if adsorbed alone on Rh(111). Deposition of K onto a CO precovered surface is found to induce large shifts towards lower binding energy of the C and O 1s core levels (∼0.7 eV for C 1s and ∼1.5 eV for O 1s). The major part of these shifts is shown to arise from the K-induced site change of the CO molecules. This finding may be of importance in the interpretation of XPS data of related co-adsorption systems. Finally, it is suggested that the C and O 1s binding energies provide useful fingerprints of the CO adsorption site also for co-adsorption systems.

ESUMS: A mobile system for continuous home monitoring of rehabilitation patients

The pressure on the healthcare services is building up for several reasons. The ageing population trend, the increase in life-style related disease prevalence, as well as the increased treatment capabilities with associated general expectation all add pressure. The use of ambient healthcare technologies can alleviate the situation by enabling time and cost-efficient monitoring and follow-up of patients discharged from hospital care. We report on an ambulatory system developed for monitoring of physical rehabilitation patients. The system consists of a wearable multisensor monitoring device; a mobile phone with client application aggregating the data collected; a service-oriented-architecture based server solution; and a PC application facilitating patient follow-up by their health professional carers. The system has been tested and verified for accuracy in controlled environment trials on healthy volunteers, and also been usability tested by 5 congestive heart failure patients and their nurses. This investigation indicated that patients were able to use the system, and that nurses got an improved basis for patient follow-up.

Automatic EEG processing for the early diagnosis of Traumatic Brain Injury

Traumatic Brain Injury (TBI) is recognized as an important cause of death and disabilities after an accident. The availability a tool for the early diagnosis of brain dysfunctions could greatly improve the quality of life of people affected by TBI and even prevent deaths. The contribution of the paper is a process including several methods for the automatic processing of electroencephalography (EEG) data, in order to provide a fast and reliable diagnosis of TBI. Integrated in a portable decision support system called EmerEEG, the TBI diagnosis is obtained using discriminant analysis based on quantitative EEG (qEEG) features extracted from data recordings after the automatic removal of artifacts. The proposed algorithm computes the TBI diagnosis on the basis of a model extracted from clinically-labelled EEG records. The system evaluations have confirmed the speed and reliability of the processing algorithms as well as the systems ability to deliver accurate diagnosis. The developed algorithms have achieved 79.1% accuracy in removing artifacts, and 87.85% accuracy in TBI diagnosis. Therefore, the developed system enables a short response time in emergency situations and provides a tool the emergency services could base their decision upon, thus preventing possibly miss-diagnosed injuries.

Printed organic conductive polymers thermocouples in textile and smart clothing applications

This work reports on an experimental investigation of the potential of using selected commercially available organic conductive polymers as active ingredients in thermocouples printed on textiles. Poly(3, 4-ethylenedioxythiophene): poly(4 styrenesulfonate) (PEDOT:PSS) and polyaniline (PANI) were screen printed onto woven cotton textile. The influence of multiple thermocycles between 235 K (−38°C) and 350 K (+77°C) on resistivity and thermoelectric properties was examined. The Seebeck coefficients of PEDOT:PSS and PANI were found to be about +18 μV/K and +15 uV/K, respectively, when “metal-polymer” thermocouples were realized by combining the polymer with copper. When “polymer-polymer” thermocouples were formed by combining PEDOT:PSS and PANI, a thermoelectric voltage of about +10 μV/K was observed. A challenge recognized in the experiments is that the generated voltage exhibited drift and fluctuations.

Development of a wearable multisensor device enabling continuous monitoring of vital signs and activity

This paper reports on the development and testing of a wearable device intended as a component in an ambulatory system for health monitoring of physical rehabilitation patients. The device measures heart rate, skin temperature, activity level and posture on the users chest. The wearable device has been run through a set of verification tests and the accuracy has been validated in controlled environment on 12 healthy volunteers. A long term user pilot with 5 congestive heart failure patients and their nurses was performed to test the whole system. The conclusion from the performed tests is that the developed wearable multisensor monitoring device is reliable, accurate, easy to use and fit for the purpose.

The surface core-level shift of the Nb(110) surface

The surface core-level shift (SCLS) of the Nb(110) surface has been determined by means of high-resolution core-level photoelectron spectroscopy of the Nb 3d5/2 core level. A SCLS of 180 +- 15 meV towards higher binding energy with respect to the bulk component was estimated by curve fitting the Nb 3d5/2 core-level spectra taken using several photon energies. The sign of the SCLS agrees with recent ab initio calculations including both initial- and finalstate effects, but the shift is significantly smaller than predicted in these calculations.