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Purpose Nowadays, using of material properties for monitoring of phenomena occurring in the surrounding environment is very desirable. Taking into account the dynamic development of Internet of Things and the technological development of printed electronics, research into the using of printed electronic components for sensor applications can be one of the most prominent directions of searching for new innovative solutions. Among others, it is possible to apply them to produce the strain gauges, as well as for construction of advanced sensors for medical applications. The goal of this paper is to present the possibilities and using different constructions of embedded polymer thick-film resistors as the sensors of tension or strain. Design/methodology/approach The investigations were based on the polymer thick-film resistors made of carbon or carbon–silver inks printed on copper pads made on FR-4 material on two sides. The longitudinal samples laminated with resin-coated copper foil material and without lamination were bent on a strength machine. During the tests, the resistors depending on their placement were stretched or compressed. Some of the samples were also tested under high pressure. Under the influence of applied stresses, there was a reversible change in electrical resistance, which was monitored. Findings The study showed that the polymer thick-film resistors are characterized by a measurable piezoresistive effect. By analyzing the value of the observed resistance changes, a magnitude of strain or pressure can be worked out. During the bending, the piezoresistive effect depends on the location and orientation of the resistor. After stopping of the mechanical strains, the electrical resistance of the resistive elements does not return exactly to the initial value. This is probably related to the substrate material and the resistive paste composition. The results are very promising and further research will be done. Originality/value The results provided information about the piezoresistive effect of polymer thick-film resistors printed on the deformable substrate which could be interesting for engineers involved in printed sensor development dedicated for different fields of application. This phenomenon can be used to manufacturing cheap and uncomplicated sensors to monitor deformation. There are several aspects to be solved, but with the use of new types of resistive pastes and substrates, there is a potential possibility of using such resistors as sensors.

Purpose The purpose of this paper is to investigate the behavior of embedded passives under changing temperature conditions. Influence of different temperature changes on the basic properties of embedded passives was analyzed. The main reason for these investigations was to determine functionality of passives for space application. Design/methodology/approach The investigations were based on the thin-film resistors made of Ni-P alloy, thick-film resistors made of carbon or carbon-silver inks, embedded capacitors made of FaradFlex materials and embedded inductor made in various configurations. Prepared samples were examined under the influence of a constant elevated temperature (100, 130 or 160°C) in a long period of time (minimum of 30 h), thermal cycles (from −40 to +85°C) or thermal shocks (from −40 to +105°C or from −40 to +125°C). Findings The achieved results revealed that resistance drift became bigger when the samples were treated at a higher constant temperature. At the same time, no significant difference in change in electrical properties for 50 and 100 Ω resistors was noticed. For all the tests, resistance change was below 2 per cent regardless of a value of the tested resistors. Conducted thermal shock studies indicate that thin-film resistors, coils and some thick-film resistors are characterized by minor variations in basic parameters. Some of the inks may show considerable resistance variations with temperature changes. Significant changes were also exhibited by embedded capacitors. Originality/value The knowledge about the behavior of the operating parameters of embedded components considering environmental conditions allow for development of more complex systems with integrated printed circuit boards.

Prace te w znacznej cześci zostaly zrealizowane dzieki aparaturze i doświadczeniom pozyskanym przy realizacji projektu nr MIME POIG.01.01.02-00-108/09

Purpose The purpose of this paper is to investigate the basic functional parameters of passive embedded components in printed circuit boards (PCBs) under environmental exposures such as thermal-humidity and thermal exposure. Design/methodology/approach The investigations were based on the thin-film resistors made of NiP alloy, thick-film resistors made of carbon or carbon–silver inks, embedded capacitors made of FaradFlex materials and embedded inductor made in various configurations. The capacitors and thin- and thick-film resistors were tested in the climatic chamber in conditions of thermal-humidity exposure at 85°C and 85 per cent RH for 500 h. The embedded inductors were tested in two different environmental conditions: thermal-humidity exposure at 60°C and 95 per cent RH, and thermal exposure at 150°C and additionally at the temperature in the range of +25°C to +150°C. Findings Studies show that in the case of embedded capacitors, the changes caused by exposure to thermal-humidity are durable and lead to the capacity increase. The embedded thin-film resistors behave in the same manner, whereas the thick-film resistors were the least resistant to the conditions of exposure. Most of the polymer thick-film resistors have been damaged. The changes of coils' properties during aging are small, and what is most important is that, after some time of exposure, their parameters stabilize at a particular level. The changes resulting from the increase in temperature are typically related to the change of material resistance (Cu) of which coils are made, and as such, they cannot be avoided but they can be predicted. Research limitations/implications The realized studies allowed determination of the properties of the embedded passive elements with respect to specific environmental exposures. The studies show that embedded resistors can be used interchangeably with chip passive elements. It allows saving the area on the surface of PCB, occupied by these passive elements, for assembly of active elements integrated circuits (ICs) and thus enabling the miniaturization of electronic devices. Originality/value The knowledge about the behavior of the operating parameters of embedded components, considering the environmental conditions, allows for development of more complex systems with integrated PCBs.

Purpose The purpose of this paper is to evaluate the influence of solder powders sizes applied in soldering materials used for Package-on-Package (PoP) system manufacture as well as other factors on reliability and mechanical strength of created solder joints in three-dimensional (3D) PoP structures. Design/methodology/approach The design of experiments based on the Genichi Taguchi method were used in the investigation. The main factors covered different printed circuit board (PCB) coatings, soldering materials with solder powders sizes from Types 3 to 7 and soldering profiles. The reliability of 3D PoP structures was determined by measurements of resistance of daisy-chain solder joints systems during thermal shocks (TS) cycles. The mechanical strength of solder joints in 3D PoP structures was determined by measurements of a shear force of “Top” layer of 3D structures at T0 and after 1,500 TS. The ANOVA was used for results assessment. Findings The size of solder powders applied in soldering materials had small (10 per cent) influence on mechanical strength of solder joints in 3D PoP structures. Small size of solder powder had positive effect on solder joints reliability in 3D PoP structures. Especially important was the selection of solder paste for “Bottom” layer of 3D PoP system (influence 17 per cent). Incorrect soldering profile (influence 46 per cent) or wrong selected PCB coating (influence 35 per cent) can very easily reduce the positive impact of soldering materials on solder joints reliability. It was stated that as low as possible soldering profile and organic solderability preservative (OSP) coating in the case of single-sided PCB are the best for 3D PoP structures due to their reliability. Originality/value This paper explains how different sizes of solder powders used nowadays in solder pastes influence on reliability and mechanical strength of the solder joints in 3D PoP structures. The contribution, in numerical values, of soldering materials, soldering profile and PCB coating on 3D PoP structures solder joints reliability as well as recommendations improving reliability of 3D PoP structures solder joints were presented.

Purpose – The purpose of this paper is to determine the dependence of mechanical strength of solder joints on printed circuit boards from the soldering process parameters and operating conditions of the electronic device. Design/methodology/approach – The research was performed using the Taguchi method of planning of experiments. Evaluation of the quality of solder joints was made on the basis of microscopic observations, X-ray analysis and measurements of shear force of solder joints. Findings – The carried out research has shown the influence of the individual parameters of the soldering process on the mechanical strength of solder joints and the mechanism of damage of solder joints under the influence of shear force. Originality/value – The authors present results of their research using advanced techniques of experimental design and analysis of results. In this study, original approach was used to simulate the operational conditions of electronic devices including thermal imaging technology.

Purpose – This paper aims to present certain issues in direct bonded copper (DBC) technology towards the manufacture of Al2O3 or AlN ceramic substrates with one or both sides clad with a copper (Cu) layer. Design/methodology/approach – As part of the experimental work, attempts were made to produce patterns printed onto DBC substrates based on four substantially different technologies: precise cutting with a diamond saw, photolithography, the use of a milling cutter (LPKF ProtoMat 93s) and laser ablation with differential chemical etching of the Cu layer. Findings – The use of photolithography and etching technology in the case of boards clad with a 0.2-mm-thick Cu layer, can produce conductive paths with a width of 0.4 mm while maintaining a distance of 0.4 mm between the paths, and in the case of boards clad with a 0.3-mm-thick copper layer, conductive paths with a width of 0.5 mm while maintaining a distance of 0.5 mm between paths. The application of laser ablation at the final step of removing the unnecessary copper layer, can radically increase the resolution of printed pattern even to 0.1/0.1 mm. The quality of the printed pattern is also much better. Research limitations/implications – Etching process optimization and the development of the fundamentals of technology and design of power electronic systems based on DBC substrates should be done in the future. A limiting factor for further research and its implementation may be the relatively high price of DBC substrates in comparison with typical PCB printed circuits. Practical implications – Several examples of practical implementations using DBC technology are presented, such as full- and half-bridge connections, full-wave rectifier with an output voltage of 48 V and an output current of 50 A, and part of a battery discharger controller and light-emitting diode illuminator soldered to a copper heat sink. Originality/value – The paper presents a comparison of different technologies used for the realization of precise patterns on DBC substrates. The combination of etching and laser ablation technologies radically improves the quality of DBC-printed patterns.

Purpose – This paper aims to report the investigations of capacitors and inductors embedded into printed circuit boards (PCBs) designed in various layouts. Design/methodology/approach – The research were focused on the components embedded into four-layer PCBs with different structures of the inner layers. Three special capacitive laminates for manufacturing of thin-film embedded capacitors and several types of coils in the form of a spiral, meander and solenoid are described. In addition, a part of the spiral-type coils was formed with an aperture in the center in which the magnetic core, made of soft magnetic composites’ material was placed to increase the coil inductance. Findings – Various constructions of embedded capacitors and coils were designed and manufactured. Capacitance and loss tangent of capacitors to determine the repeatability of the production process were determined. Capacitor’s long-term stability analysis was performed by exposing test samples to elevated temperatures (70, 100 or 130°C), realized with the aid of heating plate, for at least 160 h. The temperature characteristics for the capacitance and loss tangent from 15 to 100°C were determined. Also the induction of different designs and layouts coils was determined. Originality/value – The wide parameters’ characterization of capacitors and coils embedded into PCBs allow the analysis of their properties with regard to their practical application. The promising results of the realized measurements show that the capacitors and induction coils with studied structures can be widely used in the construction of embedded circuits into PCBs (e.g. filters, radio frequency identification systems and generators).

The paper shows the results of investigation of quality and reliability of soldered joints in 3D TMV PoP structures after assembly using corner bonding and underfilling techniques processes. The 3D solder joints reliability studies were realized using thermal shocks (TS). The results showed that underfilling technique the most positive influences on the 3D TMV PoP structures reliability, but other technological and materials parameters have to be taken into consideration during their assembly process planning. The usage of no optimal technological parameters during the 3D TMV PoP structures assembly decreased reliability of their solder joints up to 30%.

Purpose – The purpose of this paper is to investigate the thermal behaviour of thin- and thick-film resistor with different dimensions and contacts embedded into printed circuit board (PCB) and compare them to the similar constructions of discrete chip resistors assembled to standard PCBs. Design/methodology/approach – In investigations the thin- and thick-film embedded resistors with the bar form in different dimensions and configurations of contacts as well as rectangular chip resistors in package 0603 and 0402 were used. In tests were carried out the measurements of dissipated power in temperature of resistor about 40°C, 70°C and 155°C. The power dissipation was calculated as a multiplying of electrical current flowing through the resistor with voltage across the resistor. The dissipation of heat generated by electrical current flowing through resistors was examined by means of the FLIR A320 thermographic camera with lens Closeup×2 and the power source. Findings – The results show that, in case of chip resistors, the intensity of heat radiation strongly depends on dimensions of copper contact lands and also depends on the dimensions of the resistor. In case of embedded resistors, with comparable dimensions to chip resistors, they have lower ability to power dissipation, as well as the copper contact lands dimensions have lower influence. The thermal radiation through resin material is not as effective as it is in case of resistors assembled on PCB. However, the embedded thick-film resistors, especially made of paste Minico M2010, have already the similar parameters to 0402 chip resistors. Research limitations/implications – Research shows that embedded resistors can be used interchangeably with SMD resistors it allows to open up space on the surface of PCB, but it should be taken into account the lower energy dissipation capabilities. It is suggested that further studies are necessary for accurately determining the thermal effects and investigate the structures of embedded passive components that allow for better heat management. Originality/value – Thermal stability of embedded resistors during operation is a critical factor of success of embedded resistor technology. The way of power dissipation and heat resistance are one of the important operating parameters of these components. The results provide information about the power and the energy dissipation of embedded thin- and thick-film resistors compared to the standard surface mount technology.

Purpose – The purpose of this paper is to investigate the influence of parameters of embedded resistive elements manufacturing process as well as the influence of environmental factors on their electrical resistance. The investigations were made in comparison to the similar constructions of discrete chip resistors assembled to standard printed circuit boards (PCBs). Design/methodology/approach – The investigations were based on the thin-film resistors made of NiP alloy, thick-film resistors made of carbon or carbon-silver inks as well as chip resistors in 0402 and 0603 packages. The polymer thick-film resistive films were screen-printed on the several types finishing materials of contact terminations such as copper, silver, and gold. To determine the sensitivity of embedded resistors versus standard assembled chip resistors on environmental exposure, the climatic chamber was used. The measurements of resistance were carried out periodically during the tests, and after the exposure cycles. Findings – The results show that the change of electrical resistance of embedded resistors, in dependence of construction and base material, is different and mainly not exceed the range of 3 per cent. The achieved results in reference to thin-film resistors are comparable with results for standard chip resistors. However, the results that were obtained for thick-film resistors with Ag and Ni/Au contacts are similar. It was not found the big differences between resistors with and without conformal coating. Research limitations/implications – The studies show that embedded resistors can be used interchangeably with chip resistors. It allows to save the area on the surface of PCB, occupied by these passive elements, for assembly of active elements (ICs) and thus enable to miniaturization of electronic devices. But embedding of passive elements into PCB requires to tackle the effect of each forming process steps on the operational properties. Originality/value – The technique of passive elements embedding into PCB is generally known; however, there are no detailed reports on the impact of individual process steps and environmental conditions on the stability of their electrical resistance. The studies allow to understand the importance of each factor process and the mechanisms of operational properties changes depending on the used materials.

In the paper we propose the idea of “metallization” of the mechanically drilled through holes and the laser drilled blind holes by isotropic conductive adhesives in PCB manufacturing. Such processes can be used instead of electrochemical plating processes and are environmentally friendly. The investigations show that the filled through holes have the average resistance of about 100 mΩ while filled blind vias have average resistance of about 1 Ω in the case of PCBs with pure Cu pads. Better results were obtained if the Au pads metallization was applied onto the Cu layer. In that case the average fill resistance for through holes diameter 0.5 mm and 0.8 mm are about 50 mΩ and for vias 0.3 mm about 150 mΩ. The results are very promising for practical application.

Modern electronic devices are more and more complex and multifunctional. It could be done by producing faster and more reliable active components and increasing number of passives and interconnections’ density. To form such complex devices one can embed components in substrate of printed circuit board (PCB) or build multilayer boards. The other way is to form multi-terminal passive components to spare free surface and decrease number of interconnections. Authors created three-terminal thin-film (TF) resistors embedded in PCBs and investigated their selected properties such as resistance repeatability, long term stability, pulse durability and thermal characteristics.

Impedance Spectroscopy (IS) is a widely used measurement technique for determining the characteristics of a variety of materials and systems. Analysis of object’s AC-response can allow determine of different electrical properties due to its structure. IS can also be used to study electronic components such as gas and humidity sensors, thermistors, varistors, capacitors or resistors. The resulting impedance spectrum can be approximated by electrical equivalent circuit. However, It is difficult to find papers dedicated to the electronic systems investigated by IS method. For this reason authors analyzed properties of RC low-pass filters embedded in printed circuit boards using IS technique. These four-contact structures were made of special Ohmega/FaradFlex® composite material. It consists of a resistive/capacitive core containing OhmegaPly RCM layer (resistive NiP alloy) laminated to FaradFlex dielectric of Oak-Mitsui company. Analysis of the measurements results using impedance spectroscopy allowed a more precise determination of the filter parameters than an analysis using standard method based on ideal components. Additionally selected filters were subjected to one of the aging process (thermal aging or thermal-humidity exposure), and found that this results in a frequency shift of the filter. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Miniaturization trend in modern electronics needs high density interconnect technologies and new materials, like elastic foils as substrates. Packaging on both external or even internal layers of such substrates needs electrically connections between layers. It is usually done by holes filled by electrically conductive materials and named as microvias. In the paper the ink-jet printing technology is proposed for creating the conductive layers of microvias. The interconnection process made by ink-jet printing seems to be very promising because of the same technique can be used for making planar as well as vertical connections in flexible substrates. The holes with diameter from 30 to 60 µm were drilled by laser beam in the polyimide substrates with a thickness of 100 µm and then filled by ink-jet printing. Two types of inks with nanosilver were used. One of them contains silver particles with a very narrow size distribution (from 4 to 10 nm) and needs high temperature for sintering, the second - with much higher silver particles size (tens of nm), but lower temperature to be electrically conductive. The experiments shows, that it is possible to achieve acceptable resistance of microvias

In the recent years the huge demand for miniaturized, highly functional and also more and more reliable electronic equipment is observed. The development of electronic industry strongly depends not only on the scale of electronic components miniaturization but also depends on miniaturization and kind of printed circuit boards (PCBs). Nowadays, the flexible substrates plays more and more important role in electronics. Organic flexible electronics are being developed for computer displays, radio frequency identification tags, sensors and actuators, solar cells and for much other devices. The use of polymer-based substrates, coupled with an inkjet printing technique opens up the possibility of cost-effective processing in high volumes by use of roll-to-roll processing. Double-sided circuits requires the electrically conductive interconnections between both layers. The big challenge is the manufacturing of surface layouts and vertical interconnections in flexible substrates in the same process without an involvement of other technologies. In the current paper the idea of through-hole microvias metallization by using the inkjet printing technique is presented.

In the paper there are presented the theory and aspects of choosing of resistors construction and technology of embedding thin-layer resistors inside multilayer PCBs (Printed Circuit Boards). The two kind of Ohmega-Play® laminates (1R25/1 25Ω/□ and 1A100/1 100Ω/□) were investigated. The results of investigations of applying embedded resistors also are presented. The experiments were focused on achieving the resistances from typical row E12. The deviation of electrical resistance of manufactured resistors not exceed the ranges ± 8 % and -12 % to +2 % with using of RCM materials type 1R25/1 25Ω/□ and 1A100/1 100Ω/□ respectively. The presented results of investigations determine the first part of work made in PCB manufacturing field in Tele and Radio Research Institute.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Extremely quick progress in miniaturization and functionality of electronic components more and more influences design and manufacture of Printed Circuit Boards (PCBs). Especially it concerns miniaturization and increasing of interconnection densities. The quality and reliability of manufactured interconnects depends on metallization technique. The aim of the paper is to describe the different plating techniques of High Density Interconnections (HDI) in PCBs.

The high advanced miniaturization of electronic components determines designers and producers of PCBs (Printed Circuit Boards) to search the new constructions and technologies of HDI (High Density Interconnect) PCBs manufacturing. The researches are concentrated on the problems of miniaturization of PCBs interconnections. Many possibilities in this area are created by using of microvia technology. The microvias can be made by using of several techniques of drilling, but the great problem in this aspect is connected with possibilities of proper and repeatable metallization of microvias. Wide practical techniques of metallization allow to properly metallize of blind microvias which aspect ratio (deep/diameter of microvia) is about 1 or less. In the paper we propose the using of the magnetron sputtering deposition of copper to metallize the high aspect ratio blind microvias. During tests the using of magnetron self-sustaining mode also was investigated. This special mode allow to deposit of thin and very clear (without labour gas particles) electro-conductive layers which can be grown in electroplating processes.