Kamil Janeczek, Aneta Araźna, Wojciech Stęplewski, Marek Kościelski, Krzysztof Lipiec, Ireneusz Rafalik, Sebastian Karolewski, Dorota Liszewska and Anna Sitek
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.
Abstract
Purpose
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.
Design/methodology/approach
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.
Findings
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.
Research limitations/implications
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.
Practical implications
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.
Originality/value
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.
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Janusz Sitek, Marek Koscielski, Janusz Borecki and Tomasz Serzysko
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…
Abstract
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.
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Yan Zhang, Janusz Sitek, Jing-yu Fan, Shiwei Ma, Marek Koscielski, Lilei Ye and Johan Liu
Multiple fillers are adopted to study the filler influences on electrical and mechanical properties of the conductive adhesives. The performances of the developed nano-enhanced…
Abstract
Purpose
Multiple fillers are adopted to study the filler influences on electrical and mechanical properties of the conductive adhesives. The performances of the developed nano-enhanced interconnect materials in printing process are also evaluated. The paper aims to discuss these issues.
Design/methodology/approach
Micron-sized silver flakes are used as the basic fillers, and submicro- and nano-sized silver spheres and carbon nanotubes (CNTs) are adopted to obtain conductive adhesives with multiple fillers. Differential scanning calorimetry measurement is carried out to characterize the curing behavior of the samples with different fillers, four-probe method is used to obtain the bulk resistivity, shear test is conducted for adhesive strength, and environmental loading test is also involved. Furthermore, printing trials with different patterns have been carried out.
Findings
The electrical resistivity of the adhesives with submicro-sized silver spheres does not monotonically change with the increasing sphere proportion, and there exists an optimized value for the ratio of silver flakes to spheres. Samples with relatively small amount of CNT additives show improved electrical properties, while their mechanical strengths tend to decrease. For the printing application, the adhesives with 18.3 volume% filler content behave much better than those with lower filler content of 6 percent. The presence of the nano-particles makes a slight improvement in the printing results.
Research limitations/implications
More detailed printing performance and reliability test of the samples need to be carried out in the future.
Originality/value
The conductive adhesives as interconnect materials exhibit some improved properties with optimized bimodal or trimodal fillers. The additive of the nano-fillers affects slightly on the printing quality of the bimodal conductive adhesives.
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Janusz Sitek, Wojciech Stęplewski, Kamil Janeczek, Marek Kościelski, Krzysztof Lipiec, Piotr Ciszewski and Tomasz Krzaczek
The purpose of this paper is to evaluate the influence of assembly parameters on lead-free solder joints reliability in Package-on-Package (PoP) Technology and demonstrate factors…
Abstract
Purpose
The purpose of this paper is to evaluate the influence of assembly parameters on lead-free solder joints reliability in Package-on-Package (PoP) Technology and demonstrate factors important for this issue.
Design/methodology/approach
Two types of soldering materials and three different assembly procedures were used for assembly of PoP system. The reliability properties of assembled PoP systems were investigated using accelerated aging and periodic resistance measurements of daisy-chain solder joints systems. The purpose of such approach was to determine which soldering material (flux or solder paste) as well as which assembly process parameter (dipping depth of upper component in soldering material), would provide better reliability properties of the solder joints in the PoP system.
Findings
It was stated that both selected flux and solder paste dedicated to assembly of PoP systems can be utilized in soldering of PoP applications. More reliable PoP systems applications require larger attention regarding materials selection and assembly parameters. It is recommended 50 per cent dipping depth of ball’s height into soldering material during upper PoP component assembly for more reliable applications. For less demanding PoP systems, the process window from 30 up to 70 per cent is acceptable. All observed failures after thermal shocks occurred in upper PoP components.
Originality/value
This paper explains how materials and assembly parameters have influence on lead-free solder joints reliability in PoP systems. Especially, influence of process window for dipping procedure of upper components balls into soldering material was presented.
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Krystyna Bukat, Janusz Sitek, Marek Koscielski, Wojciech Niedzwiedz, Anna Mlozniak and Malgorzata Jakubowska
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…
Abstract
Purpose
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 (FCNTMet) or polyethylene glycol 400 (FCNTPG). 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.
Design/methodology/approach
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.
Findings
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.
Research limitations/implications
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.
Practical implications
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.
Originality/value
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.
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Marek Koscielski and Janusz Sitek
The purpose of this paper is to investigate the influence of the properties of new compositions of fluxes for selective soldering on lead-free solder joints quality and…
Abstract
Purpose
The purpose of this paper is to investigate the influence of the properties of new compositions of fluxes for selective soldering on lead-free solder joints quality and microstructures as well as showing which flux properties are the most important.
Design/methodology/approach
The three different types of fluxes were tested, which differed in composition, solids content, amount and type of activators added. The selective soldering process was done with the use of lead-free solder SAC 305. The test boards had two coatings SnCu (HASL) or Au/Ni. Basic chemical and physical properties of fluxes were examined according to the relevant standards. Different types of components from the bulky ones, demanding more heat, to the smaller ones were used during the assembly process. AOI and X-ray analyses as well as cross-sections and SEM analyses were utilized to deeply assess the quality and microstructure of the investigated solder joints.
Findings
The results showed that information about density or static activity of flux is not enough for correct flux assessment. The dynamic activity of flux measured by wetting balance method is the best for this, especially in the case when there is short soldering time and heat transfer is hindered. The quality and the microstructure of lead-free solder joints are related not only with wetting properties of the flux used for soldering but also with other properties like solids content in a flux.
Research limitations/implications
It is suggested that further studies are necessary for the confirmation of the practical application, especially of the reliability properties of the joints obtained with the use of the elaborated fluxes.
Originality/value
The results showed that type of flux (ORL or ROL) as well as minor changes in their dynamic activity and solids content might have significant influence on quality of solder joints and their microstructure. It was noted that selective soldering is demanding technique and optimization of soldering process for different type of components and fluxes is important.
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Krystyna Bukat, Janusz Sitek, Marek Koscielski, Zbigniew Moser, Wladyslaw Gasior and Janusz Pstrus
The purpose of this article is to establish why the wetting on PCBs with SnCu (HASL) and Snimm finishes in the presence of a flux is better than the wetting of those on a copper…
Abstract
Purpose
The purpose of this article is to establish why the wetting on PCBs with SnCu (HASL) and Snimm finishes in the presence of a flux is better than the wetting of those on a copper substrate. The practical aspect of the obtained results is the main goal of these investigations.
Design/methodology/approach
The authors applied the wetting balance method for the wetting measurements at 230 and 250°C, in nitrogen atmosphere, in the presence of the ORM0 type flux. The PCBs with the SnCu (HASL) and Snimm finishes were investigated in the state “as received”. To establish the wetting properties of the SnCu (HASL) and Snimm finishes on the PCBs, wetted by the investigated SnZnBiIn alloys, the SEM and EDX analyses were performed.
Findings
The authors obtained very good wetting results of the PCBs with the SnCu and Snimm finishes, wetted by the SnZn7Bi3In4 alloys. By applying the SEM and EDX methods, it was possible to establish that the barrier layer which was created during the HASL process between the copper and the SnCu solder is efficient enough to protect the copper against the influence of the Zn atoms from the SnZn7Bi3In4 solder. This is the reason for an improvement of the wetting properties. An immersion tin finish does not create such barrier layer with the copper. It results in a worse wetting than for the SnCu finishes but a better one than that for the copper. Immersion tin dissolves in the alloys during the soldering and this process delays the reaction between the copper and the Zn atoms from the SnZn7Bi3In4 solder.
Research limitations/implications
It is suggested that further studies are necessary for the confirmation of the practical application, but they should be limited to the reliability of the solder joint performance.
Practical implications
The best wetting results of the PCBs with “tin finishes”, especially with SnCu, wetted by the SnZn7Bi3In4 alloy, at 230 and 250°C and in nitrogen atmosphere, suggest a possibility of a practical usage of the tin‐zinc‐bismuth‐indium alloys for soldering in electronics.
Originality/value
The wetting balance method combined with the SEM and EDX analyses were used as the quickest way to determine the mechanism of the better wettability properties in the case of the PCBs with the SnCu and Snimm finishes, wetted by the SnZn7Bi3In4 alloy, compared to those of the PCBs on the Cu substrate.
Janusz Sitek and Marek Koscielski
The purpose of this paper is to investigate the influence of different micro additives to new compositions of electrically conductive adhesives (ECA) on their printing properties…
Abstract
Purpose
The purpose of this paper is to investigate the influence of different micro additives to new compositions of electrically conductive adhesives (ECA) on their printing properties as well as electric parameters expressed in resistivity of joints cured in low temperatures and obtain recommendations for elaboration of ECA appropriate for printing electronic applications.
Design/methodology/approach
The three different types of silver flakes and two types of micro powders were added to basic matrix of ECA to create ECA composition for investigation. The ECA were printed via stencil on elastic substrate creating the special designed samples which next were cured in 25°C, 50°C or 80°C. The SEM with EDS analysis was utilized for assessment of shapes and sizes of the input materials for ECA. The microscopic observation and resistivity measurements of samples by four-probe method were used for assessment of the influence of ECA compositions on prints quality as well as on electric parameters of adhesives joints.
Findings
The results show that the quality of the prints made with the use of elaborated adhesive compositions is related mainly with the amount and type of filler used in ECA. The electrical properties of joints were dependent from type of silver flakes and amount of micro-additives as well as curing temperature.
Research limitations/implications
It is suggested that further studies are necessary for the confirmation of the practical application, especially of the mechanical and reliability properties of the joints obtained with the use of final composition of the elaborated ECA.
Originality/value
The presented results of analyses provide information regarding the correlation between the composition of ECA, properties of elements creating them and the results of printing and electric parameters of joints produced of them. It showed positive impact of small carbon micro powder addition both on printing results and resistivity of joints. It pointed out also that the purity of silver components of ECA influences significantly on resistivity of ECA's joints. It is valuable information for ECA's designers as well as end-users, from the practical point of view.
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Marek Kościelski, Janusz Sitek, Wojciech Stęplewski, Grazyna Kozioł, Piotr Ciszewski and Tomasz Krzaczek
– The purpose of this paper is to present challenges met during package-on-package (PoP) technology implementation in real surface-mount technology assembly processes.
Abstract
Purpose
The purpose of this paper is to present challenges met during package-on-package (PoP) technology implementation in real surface-mount technology assembly processes.
Design/methodology/approach
The properties and behavior of different combinations of soldering materials, PoP components and soldering profiles were investigated, both in the laboratory and during production trials. The purpose of such an approach was identification of existing problems and challenges in lead-free PoP systems assembly as well as checking which soldering material designed to PoP is more suitable for this technology.
Findings
Technological trials are needed to select adequate soldering materials for PoP systems assembly, as laboratory tests of materials alone were not sufficient. The challenges of PoP technology were associated with the equipment utilized, the soldering materials, operational parameters and the soldering profile used for assembly. The localization of defects in PoP systems is very difficult and, in many cases, destructive methods have to be used on solder joints for the assessment and confirmation of failures.
Originality/value
This paper shows main materials and soldering challenges in lead-free PoP technology. In particular, the problem related with selection of soldering materials and soldering profiles for PoP was presented. Moreover, the issues that have to be taken into consideration during the planning of a PoP system assembly procedure are presented.