Journal of Powder Metallurgy & Mining
Open Access

Graphene; Graphene nanoplatelets; Aluminum carbide; Greasepaint metallurgy

Introduction

Graphene achieves tremendous attention since its discovery, due to its excellent parcels, similar as high Young's modulus (1 TPa), excellent fracture strength (125 GPa), super thermal conductivity (5000 W m-1K- 1) and high charge- carrier mobility(,000 cm2 V-1s-1). Meanwhile, graphene is the perfect two- dimensional (2- D) material, with chassis of sp2- clicked carbon tittles [4]. In comparison with fullerene and carbon nanotubes, graphene is of lamellar structure, being salutary to load transferring. And therefore, GNPs are extensively applied as underpinning accoutrements for high- performance structural functional mixes. The natural mechanics of the GNPs, their crumpling, wrinkling and folding, and whether they can be reused to be unfolded are the subject of ferocious studies [5]. Aluminum (Al) is one of the most extensively used nonferrous essence. High specific strength, excellent malleability, low measure of thermal expansion, applicable heat and electrical conductivity coupled with low viscosity and cost are the crucial factors that expansive operations of Al. Growing enterprises on the energy issues and environmental developments keep inspiring us to develop new light weight blends with outstanding physical and mechanical parcels [6]. GNPs corroborated Al (GNPs Al) mixes would realize immolating or perfecting physical parcels, accompanying distinctly adding of mechanical parcels in comparison with pure Al prepared by the same system. Still, for the purpose of maintaining excellent physical parcels, strength and malleability are important poorer than other examinations only fastening on perfecting mechanical parcels. Meanwhile, as structural functional mixes, methodical disquisition about GNPs/ Al mixes, paying attention to goods of microstructure on mechanical and physical parcels at the same time, is extremely essential. There have been some attempts to achieve GNPs Al mixes [7]. As two- dimensional structure accoutrements, the morphology of GNPs is a pivotal indicator to both mechanical and physical parcels(,19). At present, it's still a great challenge to realize the invariant distribution and unfolding of the GNPs efficiently. And in comparison with casting system, greasepaint metallurgy has unequaled advantage in fabricating GNPs Al mixes. Up to now, ball milling, mechanical shifting, ultrasonication and chemical system were applied to gain GNPs/ Al compound maquillages. During ball milling procedure, the more slightly the GNPs distribute, the further structural damage of GNPs would get. Mechanical shifting processing always accompanies with ultrasonic dissipation processing, which would damage GNPs and reduce product effectiveness ineluctably [8]. In chemical system, graphene oxide cannot be reduced fully and some contaminations are also conspicuous. Therefore, the mentioned amiss structure of GNPs together with contamination during compound maquillages medication processing privately linked to lowering physical parcels of GNPs/ Al mixes. Consequently, a new approach is developed to prepare GNPs Al mixes. During compound maquillages preparing procedure, GNPs get unfolded with no structure damage and distribute slightly in Al matrix. Totally, goods of microstructure on both strengthening mechanisms and electric and thermal conductivities were anatomized by comparing with pure Al with the same fabricating system. The instigative results that substantial enhancement of strength accompanies with maintaining high physical parcels have been realized [9].

Method

Synthesis of alloys

To synthesize the lead-free solders, Sn antipode(99.9), Cu(99.9), Bi(99.9), and Cr(99.9) were used as the raw accoutrements . First, the Sn – Cr master amalgamation was prepared using a medium frequence induction furnace. also it was used for synthesizing solders. The asked quantum of each element was ladened and rolled with the Sn antipode. The weighted accoutrements were put in the gauntlet and the induction furnace was used for casting (200v, 21A, 6293Hz, and 3 kW). After the homogenizing process, the casting blends were cooled down in the earth. The chemical composition of the set solders was detected by inductively coupled tube (ICP) analysis

Characterization of physical properties

Metallography

For phase identification in each amalgamation, XRD analysis was used by a PhilipsX-ray-XPERT diffractometer. To probe the microstructure of solders, the as- cast samples were sectioned and mounted. The samples were fabricated by polishing and etching. The etchant was prepared by mixing 97 ethanol, 2 HCl and 1 HNO3. Eventually, the microstructure of solders was observed by means of surveying electron microscopy (SEM) [10].

Thermal analysis

According to the ASTM D3418 standard, the Differential Scanning Calorimetry (DSC) test was done by Thermo scientific iCAP 6000. The examination was in a Nitrogen atmosphere in form of exothermicendothermic with 10°C/ min adding temperature rate and the maximum temperature was 300°C.

Wettability

To estimate the wetting down characteristics similar as contact angle and spreading rate, the IEC 60068-2-58, IPC- TM- 650, and JIS Z 3198- 3 were used. The solder balls of each synthesized solder (250 mg) were prepared and also they were put on the center of Cu substrates with RMA flux coating. These samples were transferred to the furnace and the thermal cycle was applied [11]. The disquisition of the samples was done after cooling to the room temperature. The spreading rate (SR) was calculated where H and D are the maximum height and the periphery of solder balls on the Cu tickets, independently. There were three samples for each solder and each sample was mugged in four directions and end up the average result was reported.

Results and Discussion

Phase determination and microstructure

According to the Sn-Cu pattern, the peaks of Cu6Sn5 and the β- Sn phase were detected. By the addition of Bi to the Sn-Cu, the Bi phase is formed in the β- Sn matrix without any redundant phase transition and its peaks were observed. The pattern of solders having Cr has further peaks than reference samples which are totems of the new IMC conformation. In thex-ray diffraction pattern of Sn-Cu-Bi-0.01 Cr solder at angles of38.87°,40.65°, and50.62°, and also in the pattern of Sn-Cu-Bi-0.1 Cr solder at an angle of45.71° peaks related to the Cr2Sn3 emulsion were linked. But under bitsy examination, these composites weren't observed, which is presumably due to the dissipation and veritably small size of these composites. As well as a peak was linked at about 2θ = 21.33°, but they didn't correspond to the composites in the software database. According to former exploration in this field and not being streamlinedX'Pert database, it can be assumed that this peak is the same peak related to the CrSn2 emulsion [12]. According to these results, it can be said that the presence of Cr along with Bi has affected on c/ a rate and the consequences of this effect will be reviewed in thermal and mechanical sections.

Thermal properties

One of the vital and determining factors in the soldering process is the solder melting point. One of the oldest and most extensively used criteria for estimating the melting point of solids is Lindermann Melting Law. According to this criterion, a solid material melts when the mean forecourt of the infinitesimal oscillation breadth exceeds its equilibrium state. By the addition of Cr along with Bi, the melting point dwindling compared to base reference solder has been achieved. thus, it can be assumed that the alloying rudiments have affected the infinitesimal oscillations of the Sn and accordingly reduced the melting point of blends. As it's egregious, Cr melting point is advanced than other habituated rudiments, but presence of Bi helps to not adding the melting point [13]. Some other exploration stated that addition Cr along with Pd didn't change the melting point, so it can ameliorate our supposition that presence of alternate alloying element can depress the effect of Cr on adding the melting point. The Sn – Cu solder melting point and doughy range are about 231.7 and 13.3°C, independently, which have been deceased by adding alloying rudiments. The addition of Bi reduced the doughy range to 9.1°C. By adding the element Cr to Sn – Cu – Bi, the doughy range value is reduced along with the melting point, so that the melting point of Sn – Cu – Bi-0.01 Cr solder is 227°C and its doughy range is 12.7°C. This quantum of doughy range means if the solder is cooled from the melting point to nearly 214°C, it'll not be solidified fully. The narrower doughy range of the amalgamation makes the solder further suitable because the joint conformation becomes briskly, easier, and more dependable [14]. The addition of Cr along with Bi reduced the melting point about 2 compared to the Sn- Cu solder, and by adding the quantum of Cr tenfold from0.01 to0.1wt., the quantum of doughy range reduction has changed from4.5 to15.7. The undercooling parameter (TSolidus- Tonset- cooling) indicates the solder solidification geste, which determines the degree of nucleation ease. The lower undercooling facilitates the nucleation during cooling. The addition of the Bi has reduced the undercooling 9°C (about 17), while the presence of0.01 wt. of the Cr element along with Bi has dropped undercooling about49.1, and0.1 wt. of this element has dropped it about 70, which indicates the positive effect of the Cr on the doughy range and undercooling. This positive effect can be justified by considering two reasons the addition of Cr has increased the c/ a rate of the Sn about 0.037 and accordingly the effect of infinitesimal distance on the melting point. still, contrary to the results attained in one former exploration on Sn-0.7Cu-0.2 Cr solder and Sn-0.7 Cu solder, the melting temperature has been reported 231°C and 228°C independently, which indicates the adding Cr increases the melting point [15].

Density

The viscosity of the Sn-Cu base solder is equal to7.2 g/ cm³. Despite the high viscosity of Bi(9.78 g/ cm³), no significant change was observed in the viscosity value by the addition of this element. With the addition of Cr as0.01wt., the viscosity has been reduced to6.9 g/ cm³ which is lower than SAC305 (2) solder. This reduction can be related to the lower viscosity of Cr(7.19 g/ cm³) than Cu(8.96 g/ cm³) and Bi, and also warrant eutectic composition conformation. As a tenfold increase in this element, the viscosity reached7.05 g/ cm³. Although the viscosity reduction compared to reference samples were observed, the small increase in the viscosity of Sn-Cu-Bi-0.1 Cr solder compared to Sn-Cu- Bi-0.01 Cr solder can be attributed to the conformation of CrSn2 IMCs with a viscosity of8.17 g/ cm³ and the more distribution of Cu6Sn5 with a viscosity of8.45 g/ cm³ [16].

Conclusions

The Sn-Cu-Bi-xCr solder was fabricated and the ensuing results were achieved by physical and mechanical disquisition:

1. By the addition of0.01 wt. Cr as a alternate alloying, the microstructure was changed to colony type. The presence of Cr in this position could help eutectic conformation and beget abecedarian changes in the microstructure. By adding the quantum of Cr as tenfold,0.01 wt. Cr, the phases in the mentioned colonies have come finer and more dispersed, and also blade- suchlike composites have been added to the microstructure. These new IMCs in blade- shape (with21.68 ±3.29 μm as length and1.1 ±0.11 μm as range) observed in the microstructure, had the composition near to CrSn2.

2. By the addition of Cr along with Bi, the melting point dwindling compared to the Sn – Cu solder has been achieved by the effect of the alloying rudiments on the infinitesimal oscillations of the Sn. The addition of Cr along with Bi reduced the melting point about 2 compared to the Sn – Cu solder, and by adding the quantum of Cr from0.01 to0.1wt., the quantum of doughy range reduction has changed from4.5 to15.7. The addition of the Bi has reduced the undercooling 9°C (about 17), while the presence of0.01 wt. of the Cr element along with Bi has dropped undercooling about49.1 and0.1 wt. of this element has dropped it about 70, which indicates the positive effect of the Cr on the doughy range and undercooling. This positive effect can be justified by considering two reasons the addition of Cr has increased the c/ a rate of the Sn about0.037 and accordingly the effect of infinitesimal distance on the melting point.

3. The presence of Cr as0.01 wt. reduced the wetting down angle by 23 and raised the spreading rate by 6 (compared to Sn-Cu). The addition of0.1 wt. Cr has changed the quantum of these two parameters significantly, as the wetting down angle dropped by 34, and the spreading rate increased by 15. The Sn-Cu-Bi-0.1 Cr solder showed the stylish wetting geste among all synthesized solders.

4. The TGA results easily prove that the presence of Cr could ameliorate the oxidation resistance of the solder compared to Sn-Cu solder. The Bi presence also has bettered the oxidation resistance, but the effect of Cr is more considerable. The Sn-Cu-Bi-0.1 Cr showed the stylish oxidation resistance and the Sn-Cu solder was the weakest. It can be said that the Cr element improves wettability by oxidation resistance enhancement of the solder and also solder/ substrate interface pressure reduction.

5. The tensile and yield strength increase have been observed by adding Cr. The elastic modulus and durability increase has also been seen with this alloying. The probable mechanisms to increase the strength situations of Sn-Cu- Bi-Cr solders are similar as the Hall- Petch effect (the effect of Cr element on the fine- graining of solder), the presence of Sn-Cr IMCs (which is one of the tensile strength increase and extension drop factor), the presence of Bi-precipitates, the solid result conformation, the difference in electronegativity of Cr and Sn lesser than the difference between Cu and Sn (which affects the infinitesimal bond strength), and the disruptions conformation because of the presence of Cr and Bi.

6. The presence of Cr didn't fully shift the fracture to fineness, but it passed as a admixture of ductile-brittle fracture. The hallmark of brittle fracture could also be seen in the form ofmicro-cracks and flat and fractionalization- suchlike areas. With the quantum of Cr increased tenfold, no trace ofmicro-cavities and dimples were observed. The result was fully a brittle fracture along the grain boundary.

1. Abtew M, Selvaduray G (2000) Lead-free solders in microelectronics. Mater Sci Eng R Rep 27: 95-141.

Indexed at, Google Scholar, Crossref

2. Cheng S, Huang CM, Pecht M (2017) A review of lead-free solders for electronics applications. Microelectron Reliab 75: 77-95.

Indexed at, Google Scholar, Crossref

3. Mao DL, Chen X, Li M, Ren XX, Hu AM(2006) Effect of small additions of alloying elements on the properties of Sn-Zn eutectic alloy. J Electron Mater 35: 1734-1739.

Indexed at, Google Scholar, Crossref

4. Shang JK, Liu PL (2001) Interfacial embrittlement by bismuth segregation in copper/tin-bismuth Pb-free solder interconnect. J Mater Res 16: 1651-1659.

Indexed at, Google Scholar

5. Tu KN, Hsiao HY, Chen C (2013) Transition from flip chip solder joint to 3D IC microbump: its effect on microstructure anisotropy. Microelectron Reliab 53: 2-6.

Indexed at, Google Scholar, Crossref

6. Lee HM, Jahyun Koo, Jaewon Chang, Young Woo Lee, Sung Jea Hong, et al. (2014) New Sn–0.7Cu-based solder alloys with minor alloying additions of Pd, Cr and Ca. J Alloys Compd: 126-132.

Google Scholar

7. Limaye BVP, Labie R, Vandevelde B, Vandepitte D (2007) Creep behavior of mixed SAC 405/SnPb soldered assemblies in shear loading. 9th electron Packag Technol Conf.

Indexed at, Google Scholar, Crossref

8. Rizk Mostafa Shalaby (2015) Indium, chromium and nickel-modified eutectic Sn–0.7 wt% Cu lead-free solder rapidly solidified from molten state. J Mater Sci Mater Electron 26: 6625-6632.

Google Scholar

9. Lee CW, Junghwan Bang, Dong-Yurl Yu, Yong-Ho Ko, Jun-Hyuk Son (2019) Intermetallic compound growth between Sn-Cu-Cr lead-free solder and Cu substrate. Microelectron Reliab 99: 62-73.

Google Scholar

10. Bang J, Yu DY, Ko YH, Kim MS, Nishikawa H (2017) Intermetallic compound formation and mechanical property of Sn-Cu-xCr/Cu lead-free solder joint. J Alloys Compd 728: 992-1001.

Google Scholar

11. Christopher M, Wayne Johnson R, John Evans, Peter Jacobsen, James R Thompson (2004) The changing automotive environment: high-temperature electronics. (2004) IEEE Trans Electron Packag Manuf 27: 164-176.

Indexed at, Google Scholar, Crossref

12. Lee CW, Junghwan Bang, Dong-Yurl Yu, Ming Yang, Yong-Ho Ko, et al. (2018) Improvement in thermomechanical reliability of low cost Sn-based BGA interconnects by Cr addition. Metals (Basel) 8: 586.

Indexed at, Google Scholar, Cross ref

13. Andersson C, Sun P, Liu J (2008) Tensile properties and microstructural characterization of Sn–0.7Cu–0.4Co bulk solder alloy for electronics applications. J Alloys Compd 457: 97-105.

Indexed at, Google Scholar, Crossref

14. G RW, Edwin Bradley, Carol Handwerker, Jasbir Bath, Richard D Parker (2007) Lead-free electronics: iNEMI projects lead to successful manufacturing. Illustrate John Wiley & Sons.

Google Scholar

15. Hammad AE, El-Daly AA (2011) Development of high strength Sn–0.7Cu solders with the addition of small amount of Ag and in. J Alloys Compd 509: 8554-8560.

Indexed at, Google Scholar, Crossref

16. Li G, Shi Y, Hao H, Xia Z, Lei Y (2010) Effect of phosphorus element on the comprehensive properties of Sn–Cu lead-free solder. J Alloys Compd 491: 382-385.

Google Scholar