Search results

The purpose of this paper is to study the manufacturing of SAC 305 solder paste with multiwall carbon nanotubes (MWCNT) before and after structure modification and also to investigate the added carbon nanotubes' influence on the technological properties and the microstructure of “nano” solder pastes. This work is a continuation of similar previous studies of SAC solder pastes with silver nanopowder additions.

The authors applied functionalization and esterification methods for the structural modification of the carbon nanotubes. The “nano” solder paste preparation was performed with the use of a two‐stage method of carbon nanotube dispersion in “own‐manufactured” SAC 305 solder paste. To determine the technological properties of the “nano” solder paste, slump, solder ball, wetting and spreading tests were applied according to the existing standards. Standard metallographic procedures were applied for microstructural analysis.

As expected on the basis of the previous studies of SAC solder pastes with silver nanopowders, positive results were obtained for the own‐manufactured SAC 305 solder paste with carbon nanotubes by applying the dispersion method. Also applied were functionalization and esterification methods, whose results showed microstructural changes in the carbon nanotubes. The “nano” SAC solder pastes showed a positive influence on the slump properties, compared to the basic SAC solder paste. The authors proved a negative influence of the carbon nanotubes' addition (dependent on their concentration) on the spreading and wetting of the SAC solder paste on a copper substrate, which provoked the non‐wetting and dewetting phenomena. A slight improvement was observed for the “nano” SAC solder pastes with modified carbon nanotubes. The carbon nanotubes' presence in the solder paste showed a positive effect on the growth reduction of the IMCs' thickness, which depended on the type.

The authors intend to verify the reinforcement effect of the alloys with carbon nanotubes suggested in the literature (the aim of Part II). For this purpose, an assembly process with RC electronic elements on PCBs with Ni/Au and SAC (HASL) finishes will be performed, with the use of the SAC 305 solder paste with modified carbon nanotubes, for the purpose of reflow soldering. Next, measurements of the mechanical strength of the solder joints and their microstructures will be conducted.

It is suggested that further studies of the mechanical properties and the reliability of solder joints are necessary for the practical implementation of the “nano” SAC solder pastes, but taking into account the wetting data, the investigation should be performed only for “nano” pastes with the lowest additions of modified carbon nanotubes.

The paper demonstrates a method of “nano” solder paste preparation by means of a two‐stage dispersion of carbon nanotubes in the own‐manufactured SAC 305 solder paste and a comparison study of the properties of “nano” pastes with the basic SAC solder paste.

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.

The purpose of this paper is to investigate the effect of carbon nanotube (CNT) addition on microstructure, interfacial intermetallic compound (IMC) layer and micromechanical properties of Sn-3.0Ag-0.5Cu (SAC305)/CNT/Cu solder joint under blast wave condition. This work is an extension from the previous study of microstructural evolution and hardness properties of Sn-Ag-Cu (SAC) solder under blast wave condition.

SAC/CNT solder pastes were manufactured by mixing of SAC solder powder, fluxes and CNT with 0.02 and 0.04 by weight percentage (Wt.%) separately. This solder paste then printed on the printed circuit board (PCB) with the copper surface finish. Printed samples underwent reflow soldering to form the solder joint. Soldered samples then exposed to the open field air blast test with different weight charges of explosives. Microstructure, interfacial IMC layer and micromechanical behavior of SAC/CNT solder joints after blast test were observed and analyzed via optical microscope, field emission scanning microscope and nanoindentation.

Exposure to the blast wave induced the microstructure instability of SAC305/Cu and SAC/CNT/Cu solder joint. Interfacial IMC layer thickness and hardness properties increases with increase in explosive weight. The existence of CNT in the SAC305 solder system is increasing the resistance of solder joint to the blast wave.

Response of micromechanical properties of SAC305/CNT/Cu solder joint has been identified and provided a fundamental understanding of reliability solder joint, especially in extreme conditions such as for military applications.

The research on lead-free solder alloys has increased in past decades due to awareness of the environmental impact of lead contents in soldering alloys. This has led to the introduction and development of different grades of lead-free solder alloys in the global market. Tin-silver-copper is a lead-free alloy which has been acknowledged by different consortia as a good alternative to conventional tin-lead alloy. The purpose of this paper is to provide comprehensive knowledge about the tin-silver-copper series.

The approach of this study reviews the microstructure and some other properties of tin-silver-copper series after the addition of indium, titanium, iron, zinc, zirconium, bismuth, nickel, antimony, gallium, aluminium, cerium, lanthanum, yttrium, erbium, praseodymium, neodymium, ytterbium, nanoparticles of nickel, cobalt, silicon carbide, aluminium oxide, zinc oxide, titanium dioxide, cerium oxide, zirconium oxide and titanium diboride, as well as carbon nanotubes, nickel-coated carbon nanotubes, single-walled carbon nanotubes and graphene-nano-sheets.

The current paper presents a comprehensive review of the tin-silver-copper solder series with possible solutions for improving their microstructure, melting point, mechanical properties and wettability through the addition of different elements/nanoparticles and other materials.

This paper summarises the useful findings of the tin-silver-copper series comprehensively. This information will assist in future work for the design and development of novel lead-free solder alloys.

The purpose of this paper is to investigate the influence of silver nanoparticle additions on the wetting properties of Sn‐Ag‐Cu (SAC) solder paste. In this investigation, the basic solder paste contained 85 wt.% of commercial Sn 96.5 Ag 3 Cu 0.5 powder (with the particle sizes in the range of 20‐38 μm) and 15 wt.% of self‐prepared middle activated rosin flux. To this paste was added 0.5, 1, 2 and 4 wt.% of self‐prepared silver nano‐powders of different grain sizes (from 9 to 138 nm). After the pastes had stabilized, their wetting properties were tested. The main goal of these investigations was to improve the wetting properties of SAC solder paste and to find correlations between the results of the wetting of solder paste with nanoparticles on the copper substrate with the microstructure of the solder joints.

The following methods were applied for the wetting solder paste investigation: spreading on the copper substrate, contact angle measurement on the copper and wetting on a FR‐4 laminate double sided with an 18‐μm thick copper foil. The investigations were performed at temperatures of 220, 230, 240 and 250°C. Cross‐sectioning was performed on the solder paste after reflow on the copper substrate. For the microstructural analysis of the “nano” modified solder joints obtained at 250°C, standard metallographic procedures were applied. Changes in the microstructure, the thickness of the inter‐metallic compounds (IMCs) and their chemical compositions were observed by means of scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS).

As expected, a higher silver nanoparticle addition to the SAC solder paste resulted in better wetting properties on copper. The results indicated the possibility of an improvement of the reflow soldering process by using SAC solder paste with silver nanoparticles and by lowering its soldering temperature. An improvement was also observed in the wettability with a decrease in the silver nanoparticle grain size. Also, the wettability proceeded at a lower temperature (20°C lower) than that for the SAC paste, without the nano‐additives. For the 4 per cent silver nanoparticle addition, Ag₃Sn star‐like IMCs were also found, which grew with the lowering of the silver nanoparticle grain size.

Further studies are necessary for confirmation of the practical application, especially of the mechanical properties, as well as the reliability properties of the solder joints, for the chosen solder paste with silver nanoparticles.

Taking into account the wetting data, the best results of the “nano” SAC solder pastes were obtained for the highest addition of the silver nanoparticles. It was found that the spreading on copper was higher and the contact angles were lower for the SAC solder paste with 4 per cent (by wt.) of 138‐nm grain size silver nanoparticles. A comparison of SAC solder pastes with a 4 per cent silver nanoparticle addition but of a different grain size (138‐9 nm), suggested a further improvement in wetting properties with lowering of the silver nanoparticle grain size. The results suggested the possibility of an improvement in the reflow soldering process by using SAC solder paste with silver nanoparticles and by lowering its soldering temperature.

Spreading, wetting and contact angle measurement methods were used for the wetting determination of the SAC solder paste with the silver nanoparticles on copper under the same temperature conditions. Also, the microstructure of the solder joints obtained at 250°C was determined with the use of SEM and EDS methods. The results obtained made it possible to draw conclusions regarding the correlation between the output of the wetting results and the amount and the grain size of the added silver nanoparticles, and also the microstructure and thickness of the IMCs of the “nano” solder joints.

This study aims to study the mechanical, photoelectric, and thermal reliability of SAC307 solder joints with Ni-decorated MWCNTs for flip-chip light-emitting diode (LED) package component during aging. By adding nanoparticles (Ni-multi-walled carbon nanotubes [MWCNTs]) to the solder paste, the shear strength and fatigue resistance of the brazed joint can be improved. However, the aging properties of Ni-modified MWCNTs composite solder joints have not been deeply studied. In this research, the mechanical, photoelectric and thermal reliability of SAC307 packaged flip-chip LEDs with Ni-MWCNTs added during aging were studied.

Compared with SAC solder alloys, the effects of different contents (0, 0.05, 0.1 and 0.2 Wt.%) of Ni-MWCNTs on the photoelectric and thermal properties of composite solder joints were examined. To study the aging characteristics of composite solder joints, the solder joints were aged at 85°C/85% relative humidity.

The addition of an appropriate amount of reinforcing agent Ni-MWCNTs reduces the density of the composite solder to 96% of the theoretical value of the SAC solder alloy. In addition, the microhardness increases and the wetting angle decreases. Two different phase compositions were observed in the solder joints with Ni-MWCNTs reinforcement: Cu₃Sn and (Cu, Ni)₆Sn₅. The solder joints of SAC307-0.1Ni-MWCNTs exhibit the highest luminous flux and luminous efficiency of flip-chip LED filaments, the lowest steady-state voltage and junction temperature. And with the extension of the aging time, its aging stability is the best. In short, when the addition amount of Ni-MWCNTs is 0.1 Wt.%, the solder joints exhibit the best wettability and the thinnest intermetallic compound layer. And the shear strength of the tested solder joints is the best, and the void ratio is the lowest. At this time, the enhancement effect of Ni-MWCNTs on the composite solder has been best demonstrated.

The content range of enhancer Ni-MWCNTs needs to be further reduced.

The authors have improved the performance of Ni-modified MWCNTs composite solder joints.

Composite solder with high performance has great practical application significance for improving the reliability and life of the whole device.

The purpose of this paper is to investigate the wettability and intermetallic (IMC) layer formation of Sn-3.0Ag-0.5Cu (SAC305)/CNT/Cu solder joint according to the formulation of solder paste because of different types of fluxes.

Solder pastes were prepared by mixing SAC305 solder powder with different flux and different wt.% of carbon nanotube (CNT). Fourier transform infrared spectroscopy was used to identify functional groups from different fluxes of as-formulated solder paste. The solder pastes were then subjected to stencil printing and reflow process. Solderability was investigated via contact angle analysis and the thickness of cross-sectionally intermetallic layer.

It was found that different functional groups from different fluxes showed different physical behaviour, indicated by contact angle value and IMC layer thickness. “Aromatic contain” functional group lowering the contact angle while non-aromatic contain functional group lowering the thickness of IMC layer. The higher the CNT wt.%, the lower the contact angle and IMC layer thickness, regardless of different fluxes. Relationship between contact angle and IMC layer thickness is found to have distinguished region because of different fluxes. Thus it may be used as guidance in flux selection for solder paste formulation.

However, detail composition of the fluxes was not further explored for the scope of this paper.

The quality of solder joint of SAC305/CNT/Cu system, as indicated by contact angle and the thickness of IMC layer formation, depends on existence of functional group of the fluxes.

In electronic packaging, when solid copper comes in contact with liquid solder alloy, the former dissolves and intermetallic compounds (IMCs) form at the solid‐liquid interface. The purpose of this paper is to study the effect of the presence of molybdenum nanoparticles on the dissolution of copper and the formation of interfacial IMC.

Cu wire having a diameter of 250 μm is immersed in liquid composite solders at 250°C up to 15 min. Composite solder was prepared by adding various amount of Mo nanoparticles into the Sn‐3.8Ag‐0.7Cu (SAC) solder paste. The dissolution behavior of Cu substrate is studied for SAC and Mo nanoparticles added SAC solders. The IMCs and its microstructure between the solder and substrate are analyzed by using conventional scanning electron microscope (SEM) and field emission SEM. The elemental analysis was done by using energy‐dispersive X‐ray spectroscopy.

Generally, the dissolution of the substrate increases with increasing immersion time but decreases with the increase of the content of Mo nanoparticles in the solder. The IMC thickness increases with increasing the reaction time but Mo nanoparticles can hinder the growth of IMC layer. The presence of Mo nanoparticle is found to be effective in reducing the dissolution of copper into SAC solder.

The paper shows that molybdenum nanoparticles in liquid SAC solders have a prominent effect on the substrate dissolution rate and the interfacial IMC between the SAC solder and copper substrate.

The purpose of this paper is to develop a new composite solder to improve the reliability of composite solder joints. Nano-particles modified multi-walled carbon nanotubes (Ni-MWCNTs) can indeed improve the microstructure of composite solder joints and improve the reliability of solder joints. Although many people have conducted in-depth research on the composite solder of Ni-MWCNTs. However, no one has studied the performance of Ni-MWCNTs composite solder under different aging conditions. In this article, Ni-MWCNTs was added to Sn-Ag-Cu (SAC) solder, and the physical properties of composite solder, the microstructure and mechanical properties were evaluated.

In this study, the effect of different aging conditions on the intermetallic compound (IMC) layer growth and shear strength of Ni-modified MWCNTs reinforced SAC composite solder was studied. Compared with SAC307 solder alloy, the influence of Ni-MWCNTs with different contents (0, 0.1 and 0.2 Wt.%) on composite solder was examined. To study the aging characteristics of composite solder joints, the solder joints were aged at 80°C, 120°C and 150°C.

The experimental results show that the content of Ni-MWCNTs affects the morphology and growth of the IMC layer at the interface. The microhardness of the solder increases and the wetting angle decreases. After aging at moderate (120°C) and high temperature (150°C), the morphology of the Cu6Sn5 IMC layer changed from scallop to lamellar and the grain size became coarser. The following two different phase compositions were observed in the solder joints with Ni-MWCNTs reinforcement: Cu3Sn and (Cu, Ni)6Sn5. The fracture surface of the solder joints all appeared ductile dents, and the size of the pits increased significantly with the increase of the aging temperature. Through growth kinetic analysis, Ni-modified MWCNTs in composite solder joints can effectively inhibit the diffusion of atoms in solder joints. In short, when the addition amount of Ni-MWCNTs is 0.1 Wt.%, the solder joints exhibit the best wettability and the highest shear strength.

In this study, the effects of aging conditions on the growth and shear strength of the IMC layer of Ni modified MWCNTs reinforced SAC307 composite solder were studied. The effects of Ni MWCNTs with different contents (0, 0.1 and 0.2 Wt.%) on the composite solder were examined.

The purpose of this study is to investigate the addition of 0.05 Wt.% carbon nanotube (CNT) into the Sn-1.0Ag-0.5Cu (SAC) solder on the intermetallic (IMC) growth. Lead-based solders play an important role in a variety of applications in electronic industries. Due to the toxicity of the lead in the solder, lead-free solders were proposed to replace the lead-based solders. Sn-Ag-Cu solder family is one of the lead-free solders, which are proposed and considered as a potential replacement. Unfortunately, the Sn-Ag-Cu solder faces some reliability problems because of the formation of the thick intermetallic compounds. So the retardation of intermetallic growth is prime important.

The solder joint was aged under liquid state aging with soldering time from 1 to 60 min.

Two types of intermetallics, which are Cu₆Sn₅ and Cu₃Sn were observed under a scanning electron microscope. The morphology of Cu₆Sn₅ intermetallic transformed from scallop to planar type as the soldering time increases. The addition of carbon nanotube into the SAC solder has retarded the Cu₆Sn₅ intermetallic growth rate by increasing its activation energy from 97.86 to 101.45 kJ/mol. Furthermore, the activation energy for the Cu₃Sn growth has increased from 102.10 to 104.23 kJ/mol.

The increase in the activation energy indicates that the growth of the intermetallics was slower. This implies that the addition of carbon nanotube increases the reliability of the solder joint and are suitable for microelectronics applications.