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The purpose of this paper is to present the result of research on a new fabrication technology of printed circuits board and electronics modules. The new method is based on inkjet printing technique on flexible substrates using new generations of heterophase inks. New fabrications method was used to print microwave waveguides and signal splitters as new technology demonstrators.

A fully Inkjet printed filter was printed on a flexible, transparent Kapton foil using heterophase inks developed in Instytut Technologii Materiałów Elektronicznych (ITME) for the purpose of this research based on graphene and silver nanoparticles.

A microwave module was printed using two types of Inkjet printers – PixDro LP50 with KonicaMinolta 512 printhead – and developed in an Instytut Tele- i Radiotechniczny (ITR) laboratory printer using MicroDrop a 100-μm glass nozzle printhead. Fully printed microwave circuits were evaluated by their print quality and electrical properties.

Fully Inkjet printed microwave circuits using the heterophase graphene ink were evaluated by their print quality and electrical properties.

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 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 work is to investigate the influence of carbon nanotube additions to solder paste on the solder joints mechanical strength and their microstructure. In our investigation, the basic solder paste contains 85 wt.% of the commercial Sn96.5Ag3Cu0.5 powder (with the particle sizes in the range of 20‐38 μm) and 15 wt.% of the self‐prepared middle activated rosin flux. To this paste we added the 0.01, 0.05 and 0.1 wt.% of the self‐modified CNT by functionalized them by mineral acid and than esterificated by methanol (FCNT_Met) or polyethylene glycol 400 (FCNT_PG). After the pastes had stabilized, the reflow soldering process of “zero ohm” chip resistors on PCBs with Ni/Au and SAC (HASL) finishes was carried out and then shear strength of the solder joints was measured. The correlations between the mechanical strength of solder joins without and with the carbon nanotubes and their microstructure were analysed.

For shear strength measurement of solder joints, the printed circuit boards with Ni/Au and SAC (HASL) finishes was applied. The SAC solder paste with different carbon nanotubes and the basic SAC solder paste as reference were used for this experiment. The automatic SMT line was applied for the paste screen printing; “zero ohms” chip resistors: 0201, 0402, 0603 and 0805 were placing on PWBs and then reflowing according to appropriate time – temperature profile. The shear strength of the solder joints was measured. For the solder joints microstructure analysis, the standard metallographic procedures were applied. Changes in the microstructure, the thickness of the intermetallic compounds and their chemical compositions were observed by means of the SEM equipped with EDS.

As the authors expected, the SAC solder paste with the carbon nanotubes addition improve the solder joints shear strength of the chip resistors mounted on PCBs with Ni/Au and SAC (HASL) finishes. The carbon nanotubes addition positive effects on IMCs thickness because of blocking their excessive growth.

It is suggested that further studies are necessary for the confirmation of the practical application, especially of the reliability properties of the solder joints obtained using solder paste with chosen carbon nanotubes.

Taking into account the shear strength data, the best results of the “nano” SAC solder pastes were obtained for the lowest addition of the carbon nanotubes modified by esterification process, especially by the methanol compared to the polyethylene glycol 400.

The obtained results made it possible to draw conclusions regarding the correlation between the output of the mechanical results and the amount of the added carbon nanotubes, and also the microstructure and thickness of the IMCs of the “nano” solder joints. It can be useful from practical point of view.