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This paper aims to present the results of investigations of inkjet-printed electronic circuits fabricated on a flexible substrate (KAPTON foil) using silver nanoparticles ink.

Fully inkjet-printed conductive circuit tracks were printed on a flexible, transparent KAPTON foil, using a commercial 40LT-15 C nanosilver ink as well as a PixDro LP50 inkjet printer with KonicaMinnolta 512 printhead. After cure, electrical properties by resistance measurements and printing quality by optical and SEM microscopic observation of conductive tracks were examined. Afterwards, the tested samples were annealed for 1, 2 and 3 h at 150°C or subjected to cycling bending.

It was found that silver nanoparticles ink could be used for the preparation of electronic circuits using the inkjet printing technique. The obtained patterns had appropriate mapping and good quality. It was also noticed that thermal annealing caused a decrease in resistivity values of the tested lines irrespective of their width. Approximately 34 per cent decrease was achieved in the values of resistivity of all the tested lines after the first hour of thermal annealing. After the second hour, the values of resistivity decreased by another 50 per cent. There were no visible changes in resistivity values after 1,000 cycles of bending.

In this paper, the results of thermal annealing and bending tests of inkjet-printed silver nanoparticle conductive tracks on flexible substrate were presented. That is very important information for producing printed circuit boards using ecological, rapid and low-cost inkjet printing techniques, particularly during the production of printed circuit boards on flexible substrates working in different conditions of mechanical and thermal stresses.

The aim of this paper is to present thermal and mechanical durability of conductive tracks screen-printed with silver polymer pastes on flexible magnetic sheets.

A test pattern that consisted of three straight lines was printed with two different silver pastes on a flexible magnetic sheet and a polyethylene naphthalate (PEN) foil for comparison. Electrical properties of these lines were examined by resistance measurements and their thickness was measured with a digital microscope on cross sections. Cyclic bending was performed to investigate mechanical properties of prepared samples as well as thermal shocks to analyse their thermal durability. Further, samples after thermal shocks underwent cyclic bending to test influence of thermal exposure on mechanical properties of the prepared samples. Changes in the test lines after the thermal and mechanical tests were assessed by resistance measurements and microscopic analysis of surface and internal structure of the test lines.

It was found that the most important factor having an impact on electrical, mechanical and thermal properties of the conductive tracks screen-printed on magnetic sheets is a type of paste used. The samples made with the paste PM-406 exhibited lower resistance because of a higher layer thickness compared to the lines printed with the paste PF-050. The PM-406 layers were revealed to be less durable to mechanical and thermal exposures. An analogical relationship was noticed for the samples made with PM-406 and PF-050 on a PEN foil after thermal shocks and cyclic bending. When magnetic sheets were used as a substrate, a bigger degree of damage was observed for the PF-050 samples, which even lost their electrical continuity after 1,000 bending cycles and thermal cycles, irrespective of their number. Some damage was also noticed in the magnetic sheet after the bending and thermal cycles.

Further investigations are required to examine the influence of other types of thermal exposure on electrical properties of lines printed on magnetic sheets. Other types of magnetic sheets are also recommended to be investigated as substrate materials.

The results reported in this study can be useful among others for designers of radio frequency identification (RFID) systems, which are intended to operate in a challenging environment with strong mechanical and thermal exposures.

This paper contains valuable information concerning mechanical and thermal properties of conductive tracks screen-printed on magnetic sheets which can be used, i.e. for designing of reliable near field communication/high frequency (NFC/HF)-RFID tags suitable for metallic surface.

The purpose of this study is to design and fabricate a simple passive sensor circuitry embedded into a printed circuit board (PCB) and then to examine its properties.

A passive sensor transponder integrated circuit (IC) working in the high frequency (HF) 13.56 MHz frequency band was selected for this study. A loop antenna was designed to make the reported sensor circuitry readable. Next, the sensor circuitry was fabricated and embedded into a PCB with the proposed technologies. Finally, properties of the embedded structures were examined as well-functional parameters of the sensor circuitries.

The described investigation results confirmed that the proposed technologies using an epoxy resin or standard materials used for PCB’s production allowed to successfully produce sensors embedded into PCBs. This technology did not have a negative significant impact either on quality of solder joints of the assembled transponder IC or on functional properties of the embedded sensor. Apart from the identification data, the reported sensor can provide information about a selected property of its environment, e.g. temperature when its internal temperature sensitive element is used or other factors with the use of external sensitive elements, such as humidity.

It is planned to carry on the reported investigations to examine other types of sensor circuitries capable of indicating e.g. humidity level and to evaluate influence of the proposed technology on their functional properties.

The reported sensor circuitries can be successfully used in electronic industry in internet of things systems not only to identify monitored electronic devices, but also to control selected parameters of external environment. This creates opportunity to detect device malfunction by detecting local temperature growth or to analyze its environment, which might allow to predict failure of controlled products using radio waves. This advantage seems to be extremely beneficial for applications, such as space, aviation or military, in which embedded sensor systems may lead to enhancing reliability of electronic devices by reacting on occurred failures in a more efficient way.

This study demonstrates valuable information for engineers conducting research on sensor components embedded into PCBs. The reported technologies are quite simple and cost-effective because of the use of standard materials known for PCB’s production or an epoxy resin which could be treated as an additional encapsulant material enhancing mechanical properties of the embedded sensor transponder IC.

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.

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.

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.

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.

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.

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).

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.

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.

The aim of this paper is to present non-destructive and destructive methods of failure analysis of epoxy moulded IC packages on the example of power MOSFETs in SOT-227 package.

A power MOSFET in SOT-227 package was examined twice using X-ray inspection, at first as the whole component to check if it is damaged and then after removing the upper part of package by mechanical grinding. The purpose of the second X-ray inspection was to prepare images for estimation of the total number and approximate location of voids in soft solder layers. Finally, power MOSFETs were subjected to decapsulation process using a concentrated sulphuric acid to verify existence of damage areas noticed during X-ray analysis and to observe other possible failures such as cracks in aluminium metallization or wires deformation.

X-ray analysis was revealed to be adequate technique to detect damage (e.g. meltings) in power MOSFETs in SOT-227 package, but only when tested components were analysed in the side view. This type of analysis combined with a graphic software is also suitable for voids estimation in soft solder layers. Moreover, it was found that a single acid (concentrated sulphuric acid) at elevated temperature can be successfully used for decapsulation of power MOSFETs in SOT-227 package without damage of aluminium metallization and aluminium wires. Such decapsulation process enables analysis of defects in wire, die and package materials.

Further investigations are required to examine if the presented methods of failures analysis can be used for other types of components (e.g. high power resistors) in similar packages.

The described methods of failure analysis can find application in electronic industry to select components which are free of damage and in effect which allow to produce high reliable devices. Apart from it, the presented method is applicable to evaluate reasons of improper work of tested electronic devices and to identify faked components.

This paper contains valuable information for research and technical staff involved in the assessment of electronic devices who needs practical methods of failure analysis of epoxy moulded IC packages.

The purpose of this paper is to examine electrical and mechanical properties of radio frequency identification (RFID) chip joints assembled on a flexible substrate and made from isotropic conductive adhesives (ICAs) reinforced with graphene nanoplatelets (GPNs) or graphite nanofibers (GFNs).

The ICAs reinforced with GPNs or GFNs were prepared and screen printed on a test pattern to investigate resistance and thickness of these adhesive layers. Differential Scanning Calorimetry (DSC) was performed to assess a curing behaviour of the prepared ICAs. Then, RFID chips were mounted with the prepared ICAs to the pattern of silver tracks prepared on foil. Shear test was carried out to evaluate mechanical durability of the created chip joints, and resistance measurements were carried out to evaluate electrical properties of the tested ICAs.

The 0.5 per cent (by weight) addition of GFNs or GPNs to the ICA improved shear force values of the assembled RFID chip joints, whereas resistance of these modified adhesives increased. The DSC analysis showed that a processing temperature of the tested adhesives may range from 80 to 170°C with different curing times. It revealed a crucial influence of curing time and temperature on electrical and mechanical properties of the tested chip joints. When the chip pads were cured for too long (i.e. 60 minutes), it resulted in a resistance increase and shear force decrease of the chip joints. In turn, the increase of curing temperature from 80 to 120°C entailed improvement of electrical and mechanical properties of the assembled chips. It was also found that a failure location changed from the chip – adhesive interface towards the adhesive – substrate one when the curing temperature and time were increased.

Further investigations are required to examine changes thoroughly in the adhesive reinforced with GFNs after a growth of curing time. It could also be worth studying electrical and mechanical properties of the conductive adhesive with a different amount of GFNs or GPNs.

The tested conductive adhesive reinforced with GFNs or GPNs can be applied in the production of RFID tags because it may enhance the mechanical properties of tags fabricated on flexible substrates.

Influence of GFNs and GPNs on the electrical and mechanical properties of commercial ICAs was investigated. These properties were also examined depending on a curing time and temperature. New conductive materials were proposed and tested for a chip assembly process in fabrication of RFID tags on flexible substrates.

The purpose of this paper is to investigate screen-printed high-frequency (HF) antennas for radio frequency identification (RFID) on-metal transponders in which a magnetic sheet was used as a substrate material.

A transponder antenna was designed in the form of square coil using a high-frequency electromagnetic software. Then, the antenna was fabricated with screen printing technique on two different magnetic sheets (RFN4 and RFN7) and on polyethylene naphthalate (PEN) foil for comparison. Its printing was carried out with polymer pastes based on silver flakes (PM-406 and SF). Thickness, track width and spacing were examined for the antennas using digital microscope and contact profilometer. Resistance and inductance were also measured, and resonant frequency, quality factor and target values of capacitance to achieve resonant frequency of the tested antenna at 13.56 MHz were calculated. Finally, RFID chips were mounted to the prepared antennas using an isotropic conductive adhesive, and a maximum read distance was measured with a reader installed in a smartphone.

It was found that an antenna thickness on the magnetic sheets used was higher than on PEN foil. At the same time, surface roughness of the fabricated antennas on these sheets was revealed to be higher as well. Inductance of the measured antennas exhibited good conformity with the antenna design, but higher divergence was noticed in the measured resistance. Its lowest value was achieved when the antenna was printed with the paste PM-406 on PEN foil and the highest one when it was fabricated with the paste SF on the same substrate. This suggests that high attention needs to be paid to a polymer paste selected for antenna printing. The performed tests showed that the magnetic sheet RFN4 seems to be better substrate for on-metal transponders compared to RFN7 due to lower resistance and higher quality factor of the prepared antennas.

Further investigations are required to examine mechanical and thermal durability of the HF antennas printed on the magnetic sheets.

The investigated HF antennas fabricated on magnetic sheets can find application in near field communication (NFC) transponders designed to be placed on metallic surfaces, e.g. on frames of advertising screens.

Influence of used magnetic sheets and polymer pastes on geometry and electrical properties of HF antennas for RFID on-metal transponders was investigated. The presented investigations can be interesting for NFC/RFID designers who are involved in designing systems suitable for metallic surfaces.

The purpose of this paper is to investigate the durability of radio‐frequency identification (RFID) chips assembled on flexible substrates (paper and foil), with materials evaluated with regard to mechanical stresses and dependence on the applied substrate, antenna materials, chip pad printing and chip encapsulation.

RFID chips were assembled to antennas screen printed on flexible substrates. Shear and bending tests were conducted in order to evaluate the mechanical durability of the chip joints depending on the materials used for mounting the RFID chip structures. X‐ray inspection and cross sectioning were performed to verify the quality of the assembly process. The microstructure and the resistance of the materials used for chip pads were investigated with the aim of determining the conductivity mechanism in the printed layers.

Addition of carbon nanotubes to the conductive adhesive (CA) provided a higher shear force for the assembled RFID chips, compared to the unmodified conductive adhesive or a polymer paste with silver flakes. However, this additive resulted in an increase in the material's resistance. It was found that the RFID substrate material had a significant influence on the shear force of mounted chips, contrary to the materials used for printing antennas. The lower shear force for chips assembled on antennas printed on paper rather than on foil was probably connected with its higher absorption of solvent from the pastes. Increasing the curing temperature and time resulted in an additional increase in the shear force for chips assembled to antennas printed on foil. A reverse dependence was observed for chips mounted on the antennas made on paper. An improvement in the durability of the RFID chip structures was achieved by chip encapsulation. Bending tests showed that a low‐melting adhesive was the best candidate for encapsulation, as it provided flexibility of the assembled structure.

Further studies are necessary to investigate the mechanical durability of RFID chips assembled with a conductive adhesive, with different addition levels and types of carbon nanotubes.

The results revealed that the best candidate for providing the highest RFID chip durability related to mechanical stresses was the low‐melting adhesive. It can be recommended for practical use, as it simplified the assembly process and reduced the curing step in the encapsulation of the RFID devices. From the results of shear testing, conductive adhesives with carbon nanotubes can be used in RFID chip assembly because of their ability to increase the shear force of joints created between the antenna and the chip.

In this paper, the influence of the materials used for antenna, chip pads, encapsulation and the curing conditions on the mechanical durability (shear and bending) of RFID chips was analyzed. Commercial and elaborated materials were compared. Some new materials containing a conductive adhesive and carbon nanotubes were proposed and tested in RFID chip assembly to antennas printed on flexible substrates (paper and foil).

The purpose of this paper was to determine the influence of thermal aging on the stability of organic light-emitting diode (OLED) glass samples made in ambient condition.

The samples with yellow emitting layer (named as ADS5) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) hole transport layer were examined. Some of the devices were ultraviolet-curable epoxy encapsulation directly after performance. All samples were thermally annealed at 70°C for 1, 2, 3 and 4 hours. The characteristics current–voltage for fresh and aging samples in the range of voltage from 0-15 V were made. The temperature of OLEDs samples in real-time with a thermographic camera was measured too. Additionally, scanning electron microscope image of surface Al cathode immediately after OLED performance and after annealing tests was made.

The authors stated, that irrespective of the type, the samples were undergoing the degradation. The decrease in value of the current density was registered. That were about 44 per cent and about 24 per cent after thermally annealing the samples with and without encapsulation, respectively (at tension 13 V). Additionally, there were observed massive delamination of the metal cathode.

Influence of thermal annealing and encapsulation on the dynamic characteristics of the OLED devices fabricated in ambient condition was analyzed. There are not many papers in the literature describing examinations of OLED samples which were made in environmental conditions.