Norocel Codreanu

VPS solution for lead-free soldering in EMS industries

The goal of an EMS company is to assure maximum assembling quality by minimum costs. This means minimizing losses on technological lines, minimizing defects and re-work time, optimizing assembling process in order to use minimum proceedings. The challenges are the lead-free technology with its increased temperature - could be up to 260degC when using infrared/convection techniques (IR/C) - and the appearance of circuits on glass or metal core (Copper, Aluminum) with its increased thermal mass. The paper is the result of seeking the optimum solution to assemble electronic components using lead-free technology on these kinds of printed circuits boards. Vapour Phase Soldering (VPS) is an old and forgotten technique especially due to the environment impact and to its low productivity. VPS was brought in front by lead-free technology by some major advantages: - the accurate control of the temperature at the maximum 230degC; - simultaneously, continuously and uniform heating of the surfaces, regardless the shape, color and thermal mass of printed circuit board (PCB), solder paste and components; - the remove of the oxygen or other gas molecules from soldering zone eliminating thus the need of using nitrogen.

Advanced investigations on PCB traces fusing in high power applications

The paper presents the virtual and real investigations related to the fusing of PCB traces in high power applications. The reason of performing the research and related tests is that in real applications the current carrying capacity of PCB traces is different than the value presented in standards and datasheets or obtained after solving thermal equations. Based on the experimental results, the authors want to offer a first practical resource in the case of traces/tracks fusing, in order to avoid failures of electronic systems during the operation and, why not, to offer a design guide of developing PCB fuses, which could be interesting in some specific or low cost applications. In addition, the contribution introduces finally a few “rules of thumb”, useful to designers, fabricators and hardware engineers, which will deliver practice oriented advices for specialists involved in electronic design and manufacturing.

Solar powered wireless multi-sensor device for an irrigation system

The paper presents the design and experiments of a multi-sensor device for use in agriculture crop irrigation. The soil and environment parameters are determined by specific sensors under the supervision of a microcontroller and sent through wireless communication to a central unit. The novelty is the assembly of all the sensors on a single structure, together with the wireless communication circuitry to permit the power management of the electronics in order to allow an autonomous supplying from a solar cell in parallel with a Li-Ion accumulator. The design of the power source was done to assure a 3.3V voltage. The research work was firstly focused on soil parameters: moisture and temperature. The main experiments were performed in order to calibrate the method used for sensing the soil moisture.

Training microsystems technologies in an European eLearning environment

The paper presents the ongoing activities within an European project for development of eLearning courses in microsystem technologies. It is a two-year project within the Leonardo da Vinci programme and the partners are from small and medium enterprises in microelectronics, training organizations and universities from four European countries — Romania, Bulgaria, France and Germany. The project is aimed at implementation of innovative approaches for performance- centred learning and development of new instruments in instructional design of task-performance-centred courses for education in Microsystems design and technology.

Advanced post–layout analysis laboratory platform

The laboratory platform developed and presented in this paper is destined to teach and train the under-graduate students on the importance of post-layout analysis in advanced PCB/HDI design. The electronic project consists in a digital high speed pseudo-random generator, designed with high-speed logic families and operating at 50 MHz. Two (of four) modules of the platform, one non-optimized (“wrongly”) created (NO4L-PCB) and one with an optimized design (O4L-PCB), were investigated after manufacturing for highlighting the special signal integrity issues.

Simulating an optoelectronic sensor with intensity modulation using the PSpice-MATLAB/Simulink interface

The paper presents the results obtained by the authors in the field of the system cosimulation of optoelectronic sensors. The aim was to make investigations in the multidomain simulation of the optoelectronic components and devices using PSpice and MATLAB/Simulink environments. The conclusion of this study is that a co-simulation environment allows to simulate the whole system using accurate models for the electronic devices.

New practice-oriented approach for teaching organic and printed electronics in the electronics/optoelectronics university education

Organic Electronics (OE), named also FOLAE (Flexible, Organic, (Printed) and Large Area Electronics), is a new branch of electronics, dealing with polymers and plastics, in contrast with traditional electronics, which is based on silicon, copper, oxides, etc. OE acts as a catalyst for the cost effectiveness on the market, being an emerging and fast growing field with high potential in industry. Some OE products (as OLED displays) are already on the market and others (as solar cells, lighting, transistors, etc.) are ready for it, being in the small volume manufacturing stage. Europe has a leading position in OE, mainly due to R and D collaboration, and various European projects try to strengthen this position. On these terms, the paper wants to offer an overview in teaching OE for development of future electronic systems, being destined not only to academia, but also to SMEs, professional associations, and research institutes for exploiting the synergies and complementarities of traditional electronics and OE [6].].

Performance evaluation of a thermoelectric cooler using finite element analysis

The paper presents the results of investigations on heat transfer in electronic packaging using thermoelectric cooling. The elements used for cooling, the so called Péltier elements, acts as a heat pump and transfer the heat between the “cold” zone and the “hot” zone. The thermoelectric elements are normally not used as stand alone devices, but integrated in a cooling module which includes the thermoelectric element, the heat source and the heatsink or fan. The balance between the ability of the cooler element to transport the heat and the self heating and heat spreading due to thermal transfer will determine the factor of merit for a certain cooling assembly. The new approach is the use of finite element software features in order to include thermoelectric specific effects by performing a thermal-electric coupled analysis. This offers the possibility to determine the efficiency parameters for the whole system in only one simulation environment.

Electroluminescent lamps driver on compatible flexible substrates

The electroluminescent lamps became more and more used in automotive industry and also in advertising industry domain or as backlight for LCDs. An electroluminescent lamp is basically a capacitor that contains a phosphor layer located between conductive layers that form the plates. With increasing field strength the phosphor absorbs energy and produces light. One of the capacitor electrodes is transparent and this way it is possible to use the structure as a light source. In most cases there are more lamp structures, manufactured together and presented as electroluminescent foils. The scope of the paper is to design a power supply capable to provide power to these foils under different conditions and under different environment factors. In this sense, measurement of electrical characteristics of these foils will be made. The influence of electrical parameters on light emission will be investigated.

Comparison of synthetic air jet vs. passive heat sinks for cooling COB LED modules

The use of COB (chip on board) LEDs in general lighting is increasing due to the favorable emitted light to source size ratio. COB LEDs are compact, modular and provide a generally homogenous light. However, due to compactness, the power densities can be quite large and as such efficient cooling solutions must be found. Active cooling is an attractive solution; however it falls short of the required lifespan which needs to be comparable with that of the LEDs. This paper compares two cooling methods: the first uses a passive heat sink and the second is based on synthetic air jets. The paper shows how a synthetic jet cooler can be used to cool high power LEDs, with an energy consumption that is comparable with that of the LED, and without increasing the size and the complexity of the light fixture significantly. Although the use of a synthetic jet cooler for power LED cooling is not new, the aim in this material is to perform a quantitative comparison between the two methods in terms of LED temperature, total energy consumption and lighting parameters.