Rita Mohd Said
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Preferred name
Rita Mohd Said
Official Name
Rita, Mohd Said
Alternative Name
Mohd Said, Rita
Said, Rita Mohd
Said, R. M.
Mohd Said, R.
Said, R. Mohd
Main Affiliation
Scopus Author ID
56353112100

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Development of a robust Sn-Cu based lead-free solder paste

2019 , Rita Mohd Said

During services and/or storage, solder joint is frequently exposed to operational conditions such as temperature, mechanical load, and electrical current. These conditions increase the demand for solder material which has high performance value in physical, mechanical, electrical and thermal stability. Thus, this research was motivated to develop Sn-Cu solder paste for robust solder joint through micro-alloying, composite and transient liquid phase soldering (TLPS) approaches. The aims of this study are to investigate the thermal properties, the phases that exist, the solderability, the microstructure evolution and also the shear strength of the new robust Sn-Cu based solder paste. The thermal stability of each solder paste has been investigated by determining the intermetallic compound (IMC) growth kinetic during isothermal aging. Isothermal aging was conducted for 24, 240 and 480 hours at a temperature of 75, 125, and 150 °C respectively. The robust solder paste was synthesized by using Sn-0.7Cu (SC), Sn-0.7Cu-0.05Ni (SCN), Sn-0.7Cu-0.05Ni-1TiO₂ (SCNT) and Sn-10Cu (SC10) TLPS bonding system. Findings reveal the reduction of about 1.5°C - 33.5°C in undercooling of solder paste with third element addition; Ni, TiO₂, and 10Cu. Result also reveals the improvement in contact angle for about 1.3°, 14.9°, and 9.5° for SCN, SCNT and SC10 solder respectively. The addition of Ni and TiO₂helps in refining the microstructure which had improved the mechanical properties. Furthermore, the IMC formation for TiO2 reinforced solder paste has been suppressed for 13.9%. The lowest growth rate was presented by SCNT (0.280, 1.390 and 2.800 0 ms-1 at aging temperature 75, 125 and 150°C respectively) and the SCNT solder also displays the highest activation energy which was 37.35 kJmol-1 compared to the other solders. The thickening of interfacial IMCs thickness occurred with prolong aging time has caused a decreasing in shear strength for all solder joints. Nevertheless, the highest strength was observed in SC10 TLPS. Overall, owing to excellent in solderability, thin IMC thickness, finer microstructure, and high shear strength have proven the SCNT solder paste composite a potential solder interconnect to be applied in typical electronic assemblies. In addition, SC10 TLPS could be established as a promising candidate for TLPS solder alloy for high power electronic assemblies.

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Superconducting lead-free solder joint: a short review

2020 , Rita Mohd Said , Mohd Arif Anuar Mohd Salleh , Norainiza Saud , Mohd Izrul Izwan Ramli

Superconducting solders are widely used as joining material to connect superconducting wires such as Niobium-titanium (NbTi) and Niobium-tin (Nb3Sn) wires in commercial superconducting magnet applications. The physical and superconducting properties of the solder materials are very important since it influence the overall performance of the joint during service. Pb-Bi solder alloy widely used due to their good properties suitable for the superconducting application, however, the restriction on the use of Pb in industry lead to the development of new Pb-free solder material. This paper reviews the superconducting Pb-free solder alternatives, including In-Sn based solder. Besides that, the effect of bismuth (Bi) and antimony (Sb) addition to the binary In-Sn solder alloy were also discussed.

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The effect of thermal annealing on the microstructure and mechanical properties of Sn-0.7Cu-xZn Solder Joint

2021 , Mohd Izrul Izwan Ramli , Mohd Arif Anuar Mohd Salleh , Rita Mohd Said , Marcin Nabiałek , Mohd. Mustafa Al Bakri Abdullah , Norainiza Saud , Dewi Suriyani Che Halin

The microstructural properties of a Pb-free solder joint significantly affect its mechanical behaviours. This paper details a systematic study of the effect of the annealing process on the microstructure and shear strength of a Zn-added Sn-0.7Cu solder joint. The results indicated that the IMC layer’s thickness at the solder/Cu interface increases with annealing time. The interfacial IMC layer of the Sn-0.7Cu solder joint gradually thickened with increasing annealing time and annealing temperature, while the interfacial IMC layer’s morphology changed from scallop-type to layer-type after the annealing process. However, the addition of 1.0 wt.% and 1.5 wt.% Zn in the Sn-0.7Cu effectively altered the interfacial IMC phase to Cu-Zn and suppressed the growth of Cu3Sn during the annealing process. The single-lap shear tests results confirmed that the addition of Zn decreased the shear strength of Sn-0.7Cu. The interfacial IMC of the Cu6Sn5 phase in Sn-0.7Cu changed to Cu-Zn due to the addition of Zn. The shear fractures in the annealed solder joint were ductile within the bulk solder instead of the interfacial IMC layer. Increased annealing time resulted in the increased presence of the Cu-Zn phase, which decreased the hardness and shear strength of the Sn-0.7Cu solder joint.

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The microstructure evolution and activation energy study of Cu₆Sn₅ and Cu₃Sn intermetallic compound layer of Sn-10Cu/Cu solder joint

2024-03 , Muhammad Amirul Aiman A. Ramlee , Rita Mohd Said , Nur Syahirah Mohamad Zaimi , Norainiza Saud

The electronic packaging industry is gradually moving away from lead solder to lead-free solder, which is more environmentally friendly. However, there is still work to be done to ensure that lead-free solder meets the demands and requirements of the latest technology. The present study demonstrates the analysis of the microstructure formation of Cu₆Sn₅ and Cu₃Sn intermetallic compound layers in Sn-10Cu/Cu solder joints. Therefore, the key objective of this research is to determine the growth rate and activation energy of the Cu₆Sn₅ and Cu₃Sn intermetallic compound layer of the Sn-10Cu/Cu solder joint. The investigation on the bulk solder microstructure which consists of Cu₆Sn₅ and Cu₃Sn intermetallic compound layer was carried out using Optical Microscope (OM), Scanning Electron Microscope (SEM) with EDX and ImageJ software. The IMC layer undergoes rapid growth with increasing aging temperature and duration and the two main IMC layers (Cu₆Sn₅ and Cu₃Sn) grew thicker. The growth kinetic solder joints for Sn-10Cu and Sn-0.7Cu are 22.44 kJ/mol and 31.20 kJ/mol, respectively. Hence, the findings from this study may offer useful information for the development of high-reliability solder joints in future applications.

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Microstructure and growth kinetic study in Sn–Cu transient liquid phase sintering solder paste

2020 , Rita Mohd Said , Mohammad Zikry Ramli , Mohd Arif Anuar Mohd Salleh , H. Yasuda , Norainiza Saud , K. Nogita

The feasibility of the highly reliable and replicable microstructure formation of the transient liquid phase sintering (TLPS) paste during the early soldering and isothermal aging on the Cu substrate had been successfully investigated in this study. By using the Sn–0.7 wt% Cu (SC) solder paste as the base material and the Cu particles in the production of the TLPS Sn–10 wt% Cu (SC10) solder paste, the ensuing Cu6Sn5 phase from the isothermal aging process was found to have reduced the β-Sn area of the bulk SC10 solder microstructure. The growth kinetic for TLPS SC10 resulted in a 26.76 kJ/mol of activation energy level. The real-time synchrotron radiation imaging technique that was employed in studying the growth and formation of the primary intermetallic phases at the solder joints had also discovered the primary intermetallic in TLPS SC10 was not only found to have experienced an early nucleation just after the solder had melted, but its growth was also restricted prior to the solidification of the liquid solder. Therefore, the relevance of the results that were obtained from this research may offer a possible solution for aiding the future development of highly reliable solder joints in high temperature solder applications.

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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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Performance of Sn-3.0Ag-0.5Cu composite solder with kaolin geopolymer ceramic reinforcement on microstructure and mechanical properties under isothermal ageing

2021 , Nur Syahirah Mohamad Zaimi , Mohd Arif Anuar Mohd Salleh , Andrei Victor Sandu , Mohd Mustafa Al Bakri Abdullah , Norainiza Saud , Shayfull Zamree Abd Rahim , Petrica Vizureanu , Rita Mohd Said , Mohd Izrul Izwan Ramli

This paper elucidates the effect of isothermal ageing at temperature of 85 °C, 125 °C and 150 °C for 100, 500 and 1000 h on Sn-3.0Ag-0.5Cu (SAC305) lead-free solder with the addition of 1 wt% kaolin geopolymer ceramic (KGC) reinforcement particles. SAC305-KGC composite solders were fabricated through powder metallurgy using a hybrid microwave sintering method and reflowed on copper substrate printed circuit board with an organic solderability preservative surface finish. The results revealed that, the addition of KGC was beneficial in improving the total thickness of interfacial intermetallic compound (IMC) layer. At higher isothermal ageing of 150 °C and 1000 h, the IMC layer in SAC305-KGC composite solder was towards a planar-type morphology. Moreover, the growth of total interfacial IMC layer and Cu3Sn layer during isothermal ageing was found to be controlled by bulk diffusion and grain-boundary process, respectively. The activation energy possessed by SAC305-KGC composite solder for total interfacial IMC layer and Cu3Sn IMC was 74 kJ/mol and 104 kJ/mol, respectively. Based on a lap shear test, the shear strength of SAC305-KGC composite solder exhibited higher shear strength than non-reinforced SAC305 solder. Meanwhile, the solder joints failure mode after shear testing was a combination of brittle and ductile modes at higher ageing temperature and time for SAC305-KGC composite solder.

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The effect of Ni and Bi additions on the solderability of Sn-0.7Cu solder coatings

2019 , Mohd Izrul Izwan Ramli , Mohd Arif Anuar Mohd Salleh , P. Narayanan , Mohd. Mustafa Al Bakri Abdullah , J. Chaiprapa , Rita Mohd Said , S. Yoriya , K. Nogita

The present investigation explores the influence of Ni and Bi on the solderability of Sn-0.7Cu solder coatings. The minor addition of 0.05 wt.% Ni into the Sn-0.7Cu solder alloy results in an improvement in the wettability based on dipping tests. The solderability investigation using a globule mode shows the influence of Ni and Bi on the interfacial intermetallic compound (IMC). The addition of Ni to a Sn-0.7Cu solder coating resulted in a (Cu,Ni)6Sn5 interfacial IMC, which enhanced the solderability performance during the globule test. With an increasing amount of Bi in the Sn-0.7Cu-0.05Ni-xBi solder ball, the surface energy of the solder alloy can be reduced, and this improves the solderability. The synchrotron micro-XRF results indicate that Ni is found in a relatively high concentration in the interfacial layer. Additionally, Bi was found to be homogenously distributed in the bulk solder, which improved solderability.

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The effect of thermal annealing on the microstructure and mechanical properties of Sn-0.7Cu-xZn solder joint

2021 , Mohd Izrul Izwan Ramli , Mohd Arif Anuar Mohd Salleh , Rita Mohd Said , Mohd. Mustafa Al Bakri Abdullah , Dewi Suriyani Che Halin , Norainiza Saud , Marcin Nabiałek

The microstructural properties of a Pb-free solder joint significantly affect its mechanical behaviours. This paper details a systematic study of the effect of the annealing process on the microstructure and shear strength of a Zn-added Sn-0.7Cu solder joint. The results indicated that the IMC layer’s thickness at the solder/Cu interface increases with annealing time. The interfacial IMC layer of the Sn-0.7Cu solder joint gradually thickened with increasing annealing time and annealing temperature, while the interfacial IMC layer’s morphology changed from scallop-type to layer-type after the annealing process. However, the addition of 1.0 wt.% and 1.5 wt.% Zn in the Sn-0.7Cu effectively altered the interfacial IMC phase to Cu-Zn and suppressed the growth of Cu3Sn during the annealing process. The single-lap shear tests results confirmed that the addition of Zn decreased the shear strength of Sn-0.7Cu. The interfacial IMC of the Cu6Sn5 phase in Sn-0.7Cu changed to Cu-Zn due to the addition of Zn. The shear fractures in the annealed solder joint were ductile within the bulk solder instead of the interfacial IMC layer. Increased annealing time resulted in the increased presence of the Cu-Zn phase, which decreased the hardness and shear strength of the Sn-0.7Cu solder joint.

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Performance of Sn-3.0Ag-0.5Cu composite solder with Kaolin geopolymer ceramic reinforcement on microstructure and mechanical properties under isothermal ageing

2021 , Nur Syahirah Mohamad Zaimi , Mohd Arif Anuar Mohd Salleh , Andrei Victor Sandu , Mohd. Mustafa Al Bakri Abdullah , Norainiza Saud , Shayfull Zamree Abd. Rahim , Petrica Vizureanu , Rita Mohd Said , Mohd Izrul Izwan Ramli

This paper elucidates the effect of isothermal ageing at temperature of 85 °C, 125 °C and 150 °C for 100, 500 and 1000 h on Sn-3.0Ag-0.5Cu (SAC305) lead-free solder with the addition of 1 wt% kaolin geopolymer ceramic (KGC) reinforcement particles. SAC305-KGC composite solders were fabricated through powder metallurgy using a hybrid microwave sintering method and reflowed on copper substrate printed circuit board with an organic solderability preservative surface finish. The results revealed that, the addition of KGC was beneficial in improving the total thickness of interfacial intermetallic compound (IMC) layer. At higher isothermal ageing of 150 °C and 1000 h, the IMC layer in SAC305-KGC composite solder was towards a planar-type morphology. Moreover, the growth of total interfacial IMC layer and Cu3Sn layer during isothermal ageing was found to be controlled by bulk diffusion and grain-boundary process, respectively. The activation energy possessed by SAC305-KGC composite solder for total interfacial IMC layer and Cu3Sn IMC was 74 kJ/mol and 104 kJ/mol, respectively. Based on a lap shear test, the shear strength of SAC305-KGC composite solder exhibited higher shear strength than non-reinforced SAC305 solder. Meanwhile, the solder joints failure mode after shear testing was a combination of brittle and ductile modes at higher ageing temperature and time for SAC305-KGC composite solder.

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