P. Svasta

PCBs with different core materials assembling in vapor phase soldering technology

The increasing demand for high integration with continuous decreasing dimensions, maintaining quality and low cost for electronic modules brought on the market new types of printed circuits boards (PCBs), having different material core as substrate. Taking into account only rigid PCBs, glass for applications requiring high levels of cleanliness (medical apparatus) or dedicated to work in high humidity environmental conditions. In the practice, the EMS companies become to have difficulties for assembling the PCBs with glass core determined by high differences of the thermophisical properties compare to classical FR4, being hardly to adjust the SMT lines parameters. In this paper it is analyzed the influence of the PCB substrate thermophysical properties over lead-free solder joints quality and reliability as results of two soldering technologies, classical infrared-convection (IRC) and vapor phase (VPS). The experiments emphasize the differences regarding soldering thermal profile determined by the glass core of the PCB substrate. The optimum soldering solution for this PCB type will be provided. The results are undeniably that PCB support material is very important for the statement of the thermal profile of the process.

Simulation of a wireless sensor network using OPNET

We aim to evaluate the performance of a ZigBee wireless sensor network using OPNET. The network is intended for a general application and should be able to collect data from many nodes, every node connected to several sensors. One possible application for such a network is in the medical area. At first the network will be used to display the evolution of blood pressure; the body temperature, the ambient temperature and pressure and the level of the transfusion liquid can be collected as well. The network coordinator will transmit the data to a local server for further processing. The simulation will be used to evaluate the general parameters of the wireless network and to optimise it.

Lead-free electronic system integrated in a Vapour Phase Soldering equipment prototype

The purpose of this paper is to present the applied research work, performed in POLITEHNICA University of Bucharest, Center for Technological Electronics and Interconnection Techniques (UPB-CETTI) in the frame of one European project and two diploma projects, oriented to the development of a VPS (Vapour Phase Soldering) equipment using ecological, lead-free, electronics and tailored to small and medium size electronics companies (SME) needs. The VPS technology seems to be today the most appropriate for many EMS companies, especially for SMEs. The lead-free electronic system developed in UPB-CETTI is in the stage of integration in a VPS equipment prototype, which is under construction in these months. The system can be embedded also in plotters, cutter plotters or milling/drilling equipment for PCB manufacturing.

Thermal investigations of solder joints used in power applications

A good way to characterize the quality of a solder joint is its thermal behavior at different currents and the current capabilities. The electrical current capabilities have been discussed in many other studies, but thermal investigations were not performed very often. The team developed a series of tests on boards with different configurations, and in all cases was proven that the solder joints heat up much less than the components or the tracks, and their temperature increases due to thermal conductivity from the surrounding elements.

Analytical modeling of contact resistance in organic transistors

Organic thin film transistors (OTFTs) are of significant interest for the development of organic electronics. The devices described in this paper, through measurements, analytic extraction of parameters and simulations, are organic transistor having Polytriarylamine (PTAA) as semiconductor. This paper refers to the determination of the source and drain contact resistance of these PTAA organic transistors. The MATLAB Simulink model is based on an analytic model, for which DC Sweep and parametric simulations were employed in order to obtain the total resistance. The results are processed in accordance to the Transfer Line Method (TLM). This mathematical method uses results on the total channel resistance of the thin film transistors with various channel lengths in order to extrapolate the contact resistance. The TLM structures considered here are bottom contact top gate OTFTs with interdigitated electrodes of various channel lengths. The values of the contact resistance are considered equal due to the symmetry of the measured structure.

VPS control module EMC modeling and evaluation

The present paper is the result of studies, experiments, modeling and simulation regarding electromagnetic compatibility (EMC) of an electronic module able to control and vary the power requirements of a Vapor Phase Soldering (VPS) machine in order to obtain the desired thermal profile. The original electronic solution has been designed to obtain very low radiated electromagnetic emission during operation by switching the power device when the AC main is zero-crossing. Electromagnetic compatibility (EMC) performance and field effects have been analyzed using 3D EM simulation software, REMCOM XFdtd by considering the VPS process control module the source of radiations. EMC evaluations of the electronic module regarding conducted and radiated emissions have been done in laboratory in order to validate the modeling and simulations results. In order to complete the design for excellence (DFX) activities in case of new products development processes the authors intend to develop a design methodology which will include modeling and EM simulation for optimum electromagnetic compatibility within the Vapor Phase Soldering system.

Investigations on organic printed resistors based on PEDOT:PSS

The emerging of printed and organic electronics has been proven as a major trend in the last years. The only major commercial issue is represented by the organic light emitting diodes (OLED). In the current paper will be shown the results of electrical investigations of organic resistors based on poly(3,4-ethylenedioxythiophene) doped with polystyrenesulfonic acid (PEDOT:PSS). The influence of the track width and of aspect ratio is also investigated. The samples are prepared by ink-jetting, using two subsequent depositions, one is the silver termination and the second one is the active resistor material. It is expected that the results offer a guidance for organic resistor dimensioning and resistor overall parameters (rated power, temperature coefficient of resistance-TCR).

Physical properties of silver inkjet printed circuits

The paper aims to describe methods of dealing with printing issues related to printing metallic nanoparticle inks with micrometric dimensions. The particular focus is on inks containing metal nanoparticles, complexes and metallo-organic compounds that reach acceptable conductivity for the structures. These need to be sintered, the low temperature representing the novel aspect. The work describes the achievement of such electrical tracks with nanoparticle inks printed with commercially available silver ink EMD5603 from Sunchemical. The electrical tracks were printed with different resolutions, on two flexible substrates and the thermal treatment was performed at different temperatures.

Start Soft Stop for controlling a reversible electric motor used in automotive

Accumulators used in electric vehicles being in production to date have the disadvantage of a limited number of charge-discharge cycles (lead-acid accumulators) or high acquisition price (NiMH, Li-Ion) and long full recharge duration. This paper presents a study on a solution to increase the life cycle of a typical battery pack used in automotive applications by recovering the deceleration energy (power generation control) and its storage in a battery of Electrochemical Double-Layer Capacitor (EDLC). Electronic module named Start Soft Stop (SSS) allows the control of energy transmitted to the electric motor, including the start and stop phases. The method used has minimal electromagnetic interference due to switching of the power semiconductor device as it passes through zero voltage. EDLC allows rapid storage and release of energy of 300–400A if needed without using the energy stored in the battery system.

The modeling & EM simulation assessment as part of DFX methodology

The paper is the result of studies, experiments and simulations regarding electromagnetic compatibility (EMC) performance of an intelligent electronic module used to obtain variable and controllable power injection during the Vapor Phase Soldering process (VPS) including the power-on and power-off phases. The module represents an original solution for low conducted and especially low radiated emissions by switching the power semiconductor devices close to the zero crossing of the mains voltage. The necessity to be optimized from EMC points of view is resolved by modeling and simulating using 3D EM simulation software, REMCOM XFdtd, for evaluating the performance and electromagnetic field effects of the VPS process power control module considered as a radiating device. The modeling process is based on preliminary measurements already taken and validated by other complex measurements which imply the need for the new experiments design. The authors intend to develop a design methodology based on the works presented in the paper which will include modeling and EM simulation, in order to complete the design for excellence (DFX) activities in case of the new products development processes.