Electronic Packaging Interconnect Technology

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Authors: Shi Qian Liu, Dong Dong Qu, Stuart D. McDonald, Kazuhiro Nogita
Abstract: Ga and Ga-based alloys appear to be promising materials for low temperature soldering in microelectronics. This research involved an analysis of the joint interfaces that resulted from reactions between a eutectic Ga-Sn alloy and Au coated Cu substrates at both room temperature and 100°C. At both temperatures the intermetallic CuGa2 accounted for the majority of the interfacial microstructure. This study has shown the possibility of using eutectic Ga-Sn alloys in low temperature soldering applications, as well as the advantages of Synchrotron XFM techniques in characterising trace element distributions in solder joints.
Authors: Quy Tran Xuan, Mohd Arif Anuar Mohd Salleh, Stuart D. McDonald, Kazuhiro Nogita
Abstract: Additions of trace elements such as Phosphorus (P) and Germanium (Ge) are common practice to improve the oxidation resistance in Tin-Copper (Sn-Cu) wave solder systems, however, little insights are available regarding their combined role. In this article, the effect of trace P (<100ppm), in the presence of Ge (<100ppm), on the phase composition and microstructure of Sn-Cu-Ni wave solder dross is studied using various techniques including Synchrotron XRPD, SEM, FIB and TEM. We find that P additions, in the presence of Ge, result in the formations of SnO, SnO2 and Ni2SnP intermetallic in the dross whereas only SnO is present in the P-free equivalent. The crystal structure of Ni2SnP is identified as orthorhombic with the space group Pnma. Based on the findings, it is evident that P not only influences the oxidation state of tin oxides but also reduces the concentration of effective Ni in the alloys via the formation of Ni2SnP intermetallic.
Authors: Flora Somidin, Stuart D. McDonald, Kazuhiro Nogita
Abstract: This paper presents the use of the transient liquid phase concept to grow the high temperature Cu6Sn5 intermetallic compound between Cu3Sn-rich powdered alloys and molten Sn. In this study, high temperature powdered alloys containing high fractions of Cu3Sn were fabricated from a chill-cast Sn-60 wt.%Cu alloy. A ternary alloy with composition of Sn-59 wt.%Cu-1 wt.%Ni was also prepared to investigate the effect of Ni. The reaction products were obtained at 250°C over a period of 30 minutes. The results provide new insight into the mechanism of the interfacial reaction between liquid Sn and solid Cu3Sn-rich alloy with and without Ni additions.
Authors: Xin Fu Tan, Mohd Arif Anuar Mohd Salleh, Stuart D. McDonald, Kazuhiro Nogita
Abstract: This paper investigated the effect of trace addition of Al and Mg on the grain refinements of Cu6Sn5 in Sn-3wt%Ag-5wt%Cu high temperature solder alloys. Furthermore, the effect of Al and Mg addition on the Sn/Ag3Sn eutectic were also investigated. It was found that the addition of both Al and Mg successfully refined the Cu6Sn5 in Sn-3wt%Ag-5wt%Cu solder alloy. In addition, Al suppresses the formation of Ag3Sn in the Sn/Ag3Sn eutectic; while Mg promotes the formation of fine Sn/Ag3Sn eutectic microstructure. The refinement of Cu6Sn5 is believed to be due to heterogeneous nucleation by Al and Mg rich intermetallic particles respectively. Effect of Al and Mg addition on the undercooling of the Sn/Ag3Sn eutectic was found to be similar, both reducing undercooling effectively at a low addition rate of 0.025wt%. The addition of Al and Mg have mixed effect on the nucleation temperature of Cu6Sn5. It is found that the nucleation temperature of Cu6Sn5 is increased with 0.025wt% Al and 0.1wt% Mg addition to the unmodified alloy, while the nucleation temperature slowly decreases again as the trace element addition rate increases.
Authors: Mohd Izrul Izwan Ramli, M.S.S. Yusof, Mohd Arif Anuar Mohd Salleh, Rita Mohd Said, Kazuhiro Nogita
Abstract: The effect of bismuth (Bi) micro-alloying additions on wettability and mechanical properties of Sn-0.7Cu lead-free solder were explored. This paper also investigates the influences of various Bi percentages on the suppression of intermetallic compound formation. Scanning electron microscope (SEM) was used to observe the microstructure evolution of solder joint including the thickness of interfacial intermetallic layers. Overall, with the addition of Bi to Sn-0.7Cu solder, the size of primary Cu6Sn5 become smaller and suppresses the thickness of interfacial intermetallic compound between solder and the Cu substrate. Microhardness value and wetting properties also increased with Bi addition which resulted in smaller size of β-Sn and Cu6Sn5.
Authors: Rita Mohd Said, Mohd Arif Anuar Mohd Salleh, Norainiza Saud, Mohd Izrul Izwan Ramli, Andrei Victor Sandu
Abstract: Microstructure evolution that exhibit from the reaction of Sn Cu pritectic alloys become an interesting phenomenon that need to be explored since the properties of the alloys depend on their microstructures. Due to less understanding on the solidification behavior on peritectic alloys, extensive research are made on this type of alloys to gain more information regarding on the microstructure formation. This paper reviews the mechanisms on peritectic solidification on Sn Cu based peritectic alloys. The changed in peritectic microstructure due to external source such as direct current (DC) field, ultrasonic field and isothermal time are discuss respectively through this paper. The focus is made on peritectic solidification of Sn Cu based alloy since it has a promising potential for high temperature lead-free solder application.
Authors: Nurul Razliana Abdul Razak, Mohd Arif Anuar Mohd Salleh, Norainiza Saud, Rita Mohd Said, Mohd Izrul Izwan Ramli
Abstract: Since the implementation of RoHS in avoidance to useof lead in electronic packaging, the development of lead-free solder has become priority. However, some of the potential candidates for lead-free solder have weaknesses such as slightly higher of melting point, excessive of intermetallic growth (IMC) and uncertainty service reliability that need to overcome. One of the common methods used to improve the characteristic and properties of the lead-free solder is by the addition of another alloying element. One of the promising alloying elements is bismuth (Bi). A few researchers have found out that Bi has a capability to improve the microstructure, reduce the melting temperature and controlled the IMC growth, yet, its advantageous is believed have not been thoroughly explored. Influence of (Bi) in lead-free solder alloys give interest to be studied and understand from different perspective due to its capability to improve the wettability and solder spread, and also reduce the melting temperatures of the solder. In this paper, a review on influence of Bi inSn-based lead-free solder and its advantageous were discussed.
Authors: Nordarina Jumali, Mohd Hafiz Zainol, Ahmad Azmin Mohamad, Muhammad Firdaus Mohd Nazeri
Abstract: The utilization of Sn-Zn based solder on electronic product was only feasible if the corrosion performance of this solder was assured. To achieve this, micro-alloying eutectic Sn-9Zn with Al was proposed. The corrosion performance was evaluated by using potentiodynamic polarization in 1 M HCl at constant scan rate. The microstructure changes due to corrosion exposure was also investigated to further understand the corrosion behaviour changes due to additions of Al. Overall corrosion rate was reduced with the micro-alloying process. Refinement of Zn-rich phase was found to help in producing much lower corrosion current and better passivation film formation on the surface due to the additions of Al. This modification deemed promising and further work should be explored in the future.
Authors: M.N. Ervina Efzan, R. Kamaneeya
Abstract: The corrosion of Sn-Zn-Bi lead free solder in 6M KOH electrolyte was conducted. The study was done using 3 different KOH concentrations (3M, 6M and 9M) and the immersion technique was used to produce corrosion. Due to the nature of immersion, the solder material was prepared by punching it into small billets size after melting it homogenously on a commercial hotplate. The immersion was set to 7, 14 and 21 days. After the specific days have fulfilled the sample billets were removed and tested. The corrosion of this solder was measured using various method such as graphical analysis, surface roughness, corrosion penetration rate (CPR) and optical microscope. In this research, it was found out that the sample billets taken from 6M concentration compared to 3M and 9M showed more corrosion this was supported by the outcome of the test. The 6M believed to provide best corrosion on the solder billets because of its high ionic conductivity value.

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