Flora Somidin
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Preferred name
Flora Somidin
Official Name
Flora, Somidin
Alternative Name
Somidin, F.
Somidin, Flora
Main Affiliation
Scopus Author ID
54973802500
Researcher ID
GPF-4634-2022

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Direct observation of the Ni stabilising effect in interfacial (Cu,Ni)₆Sn₅ intermetallic compounds

2020-03 , Flora Somidin , Hiroshi Maeno , Takaaki Toriyama , Stuart D. McDonald , Wenhui Yang , Syo Matsumura , Kazuhiro Nogita

The polymorphic transformation in interfacial intermetallic compounds in three lead-free solder joints was investigated using in situ heating/isothermal/cooling observation techniques in high-voltage transmission electron microscopy (HVTEM). Here, the hexagonal η- to monoclinic η′-Cu₆Sn₅ polymorphic transformation was visualised systematically through zone-axis electron diffraction patterns and real-space imaging. Cu₆Sn₅ grains obtained in the as-reflowed solder joints that did not contain Ni (Sn–0.7Cu/Cu and Sn–3.0Ag–0.5Cu/Cu) show weak reflections in the diffraction patterns from the η′-Cu₆Sn₅. In Sn–0.7Cu–0.05Ni/Cu joints, no weak reflections were present in the diffraction patterns of the (Cu,Ni)₆Sn₅ grains indicating the presence of Ni prevented the η- to η′-Cu6Sn5 transformation. The movement of bend contours was also observed at around 186 °C in adjacent the grain boundaries in Cu₆Sn₅ but not in the (Cu,Ni)₆Sn₅. We also uncover the origin of the weak reflections and confirm the superstructure of monoclinic η′-Cu₆Sn₅ by obtaining atomic-resolution images within the areas from which the selected area diffraction patterns were obtained.

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Mixed Assembly of Lead-free Solder Joint: A Short Review

2022-01-24 , Rita Mohd Said , Mohd Arif Anuar Mohd Salleh , Ramli M.I.I. , Saud N. , Flora Somidin , Razak N.R.A. , Ismail A.N.

The transition from lead (Pb) to Pb-free solder has arisen the need for the development of the reliability of mixed assemblies solder joint research. Mixed assemblies are defined as solder joints that joint together with different compositions or solder forms for example Ball Grid Array (BGA) and solder paste. During the transition period of solder materials, mixed assemblies are still used in electronic packaging. In addition, Pb-free manufacturing has been forced to release some of the product categories since legislation banning the use of lead solder in electronic assemblies. This phenomenon causes health and environmental concern of the Pb solder used in electronic assembly. Hence, some electronic assemblies will continue to use traditional eutectic Sn-Pb solder paste while others will use Pb-free solder paste. This situation indicates that the use of mixed assemblies in electronics manufacturing is still inevitable. This paper presents a projection of the reliability of mixed assembly's Pb-free solder joint.

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Microstructure study of mix assembly lead-free sn-ag-cu ball grid array and Sn-10Cu solder paste

2022-01-24 , Rita Mohd Said , Sulwarajan K.A.P. , Razak N.R.A. , Flora Somidin , Zaimi N.S.M.

In recent years, electronic technologies have been striving to minimize the use of lead in their manufacturing and production. As a result, the electronic packaging industry is slowly transitioning from lead solder to lead-free solder. Though environmentally lead-free solders are advantageous, there are still needs some work in meeting current technological demand and requirements. In this study, the microstructure analysis on lead-free Sn-Ag-Cu Ball Grid Array (BGA) and Sn10Cu solder paste was done. The main aim of this study is to investigate the effect of isothermal aging on the microstructure of the solder paste joint and evaluate the intermetallic compound (IMC) thickness on the solder joint reliability. Optical Microscope (OM) and ImageJ software have been utilized to study the bulk solder microstructure. The results show that the bulk microstructure consists of β-Sn and Cu6Sn5/β-Sn eutectic phases. The IMC layer has undergone rapid growth with increasing aging temperature and time. The two main IMC layers (Cu3Sn and Cu6Sn5) grew thicker due to high temperature. The growth kinetic of Sn10Cu resulted in 16.70 kJ/mol activation level. Therefore, the significance of the findings from this study might provide a potential answer for future development for highly reliable solder joint applications.

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A short review: reliability issues of lead-free Sn-based alloys for superconducting applications

2023 , Y. P. Tan , Flora Somidin

As the trends of electronic devices are moving to miniaturization which requires high-density electronic packaging and high-speed performance, superconducting solder alloy has attracted considerable interest to fulfill the requirements of advanced electronic packaging as it provides sufficient superconductivity which minimizing the loss of current densities carried by superconductors. In the past few decades, leaded superconducting solder alloy were widely used in the industry due to its satisfied performance. However, development of lead-free solder alloy for superconducting applications is initiated to replace leaded solder alloy due to its toxicity. Sn-based solder alloy is the most popular candidate for replacing leaded solder alloy in the industry, but the reliability of Sn-based solder alloy is concerned. This paper reviewed the reliability issues of lead-free Sn-based superconducting interconnects when subjected to high current stressing. Electromigration, thermo-migration, and the subsequence issues caused by high current stressing are covered. This article also summarized the studies done on minimizing the reliability issues of potential Sn-based superconducting solder alloy caused by high current stressing.

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Microstructural evolution of Cu/Sn-58Bi/Sn-3.0Ag-0.5Cu composite solder joint during isothermal aging

2022-01-24 , Flora Somidin , Bakar M.F.A. , Razak N.R.A.

A composite solder joints made of Cu/Sn-58Bi/Sn-3.0Ag-0.5Cu (in weight percent) was successfully fabricated. The composite solder was made from combining a Sn-3.0Ag-0.5Cu solder ball and Sn-58Bi solder paste. The composite solder was reflowed on Cu-OSP (copper-organic solderability preservatives) substrate to form a composite solder joint. The microstructure evolution of the composite solder joints under different reflow temperature and thermal aging conditions were investigated using an optical microscope. This study shows that a composite solder joint of SAC305/Sn-58Bi can be assembled at lower temperature (160 °C) and gradually mixed through isothermal aging.

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Fabrication and characterization of hybrid microwave assisted sintering Sn-0.7Cu + 1.0wt.% Si₃N₄ composite solder

2015 , Flora Somidin

One of the leading choices in upgrading the properties of existing lead-free solder alloys is by composite technology approach, whereby high technical ceramic particles can be added into the solder alloy matrix. Accordingly, Sn-0.7Cu + 1.0wt.% Si₃N₄ composite solder was synthesized using powder metallurgy routes which consist of blending, compaction and sintering. This research introduced a hybrid microwave assisted sintering process which can sinter ceramic-reinforced composite solder at approximately 185˚C within 2 minutes without holding time and protective inert gas. In order to evaluate the compatibility of hybrid microwave assisted sintering approach in ceramic-reinforced composite solder development, a detailed comparison of the process and properties of conventionally sintered and microwave sintered samples of Sn-0.7Cu + 1.0wt.% Si₃N₄ composite solder was performed. Identical sintering temperature at 185 ˚C was used for both types of sintering, in which conventional sintering was performed using a tube furnace in an argon atmosphere for 2 hours. The monolithic Sn-0.7Cu solder sample was also synthesized as control sample in a similar way. Hybrid microwave assisted sintering method showed significant advantages in processing compared to conventional sintering method, such as rapid heating rate, shortened sintering time, less energy consumption and much less expensive equipment. The influence of different sintering methodologies on Sn-0.7Cu + 1.0wt.% Si₃N₄ bulk solder sample were investigated based on the density, porosity, microhardness, microstructures, wettability and intermetallic compound thickness on Cu-substrate. It was noted that microwave sintering method can densify the Sn-0.7Cu + 1.0wt.% Si₃N₄ composite bulk solder green compact in a short time, however, conventional sintered sample showed better density and porosity. Interestingly, finer and well-distributed precipitates were observed in microwave sintered samples. This has led to higher microhardness performance observed in microwave sintered sample (12.0 ± 0.2 HV) compared to the conventionally sintered sample (11.2 ± 0.1 HV). The wettability performance of Sn-0.7Cu + 1.0wt.% Si₃N₄ composite solder on Cu-substrate was slightly reduced with microwave sintering approach, however, insignificant difference of intermetallic compound thickness was observed in both microwave sintered and conventionally sintered samples. Overall, hybrid microwave assisted sintering showed better processing with promising properties on ceramic-reinforced Sn-0.7Cu + 1.0wt.% Si₃N₄ composite solder.

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In-situ observation of high-temperature Pb-free electric interconnections by synchrotron microradiography

2021-05-15 , Abdul Razak N.R. , Tan X.F. , Flora Somidin , Yasuda H. , McDonald S.D. , Nogita K.

Despite a large amount of research on transient liquid phase (TLP) bonding methods for high operating temperature Pb-free solder electric interconnections using Cu6Sn5 intermetallics (IMCs), two fundamental difficulties remain, namely, slow TLP process kinetics and uncontrolled void formation. Here we observe the TLP processes for rapid Cu6Sn5 growth using a recently developed technique via real-time synchrotron X-ray imaging. The technique enables in-situ characterization of the growth kinetics and real-time observation of the IMC evolution at the molten solder/solid substrate interfaces and the formation of voids and cracking during TLP bonding, which will contribute to the development of products suitable for high reliability and high-temperature applications, e.g., electric vehicles.

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Imaging the polymorphic transformation in a single Cu6Sn5 grain in a solder joint

2018 , Flora Somidin , Hiroshi Maeno , Xuan Tran , Stuart D. McDonald , Syo Matsumura , Kazuhiro Nogita , Mohd Arif Anuar Mohd Salleh

In-situ observations of the polymorphic transformation in a single targeted Cu6Sn5 grain constrained between Sn-0.7 wt % Cu solder and Cu-Cu3Sn phases and the associated structural evolution during a solid-state thermal cycle were achieved via a high-voltage transmission electron microscope (HV-TEM) technique. Here, we show that the monoclinic η′-Cu6Sn5 superlattice reflections appear in the hexagonal η-Cu6Sn5 diffraction pattern upon cooling to isothermal 140 °C from 210 °C. The in-situ real space imaging shows that the η′-Cu6Sn5 contrast pattern is initiated at the grain boundary. This method demonstrates a new approach for further understanding the polymorphic transformation behavior on a real solder joint.

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Influence of Fly Ash Geopolymer Ceramic Powder Addition on Sn-3.0Ag-0.5Cu Solder Joints

2022-01-24 , Flora Somidin , Ilias N.F.N. , Zaimi N.S.M. , Ramli M.I.I. , Razak N.R.A.

This paper reports the effect of 1.0 wt.% fly ash (FA) geopolymer ceramic powder addition in Sn-3.0Ag-0.5Cu (SAC305, in wt.%) solder joint. Powder metallurgy route was used to fabricate the new composite solder. Solder balls were formed from the new composite solder and reflowed on Cu substrate. The effect of FA as ceramic reinforcement on the bulk microstructure and the interfacial intermetallic compound layer formation of solder joints were investigated under optical microscope. Microstructure observation showed that the β-Sn dendrite size was refined in SAC305-1.0FA/Cu bulk solder joint sample than that in the non-reinforced sample. The addition of FA geopolymer ceramic powder into the solder matrix also produced a thinner intermetallic compound layer.

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