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Article
Publication date: 27 March 2023

Y. Wu, Z.J. Zhang, L.D. Chen and X. Zhou

Laser soldering has attracted attention as an alternative soldering process for microsoldering due to its localized and noncontact heating, a rapid rise and fall in temperature…

Abstract

Purpose

Laser soldering has attracted attention as an alternative soldering process for microsoldering due to its localized and noncontact heating, a rapid rise and fall in temperature, fluxless and easy automation compared to reflow soldering.

Design/methodology/approach

In this study, the metallurgical and mechanical properties of the Sn3.0Ag0.5Cu/Ni-P joints after laser and reflow soldering and isothermal aging were compared and analyzed.

Findings

In the as-soldered Sn3.0Ag0.5Cu/Ni-P joints, a small granular and loose (Cu,Ni)6Sn5 intermetallic compound (IMC) structure was formed by laser soldering regardless of the laser energy, and a long and needlelike (Cu,Ni)6Sn5 IMC structure was generated by reflow soldering. During aging at 150°C, the growth rate of the IMC layer was faster by laser soldering than by reflow soldering. The shear strength of as-soldered joints for reflow soldering was similar to that of laser soldering with 7.5 mJ, which sharply decreased from 0 to 100 h for both cases and then was maintained at a similar level with increasing aging time.

Originality/value

Laser soldering with certain energy is effective for reducing the thickness of IMCs, and ensuring the mechanical property of the joints was similar to reflow soldering.

Details

Microelectronics International, vol. 41 no. 1
Type: Research Article
ISSN: 1356-5362

Keywords

Article
Publication date: 24 January 2023

Guisheng Gan, Shi-qi Chen, Liujie Jiang, Cong Liu, Peng Ma, Tian Huang, Dayong Cheng and Xin Liu

This study aims to research properties of Cu/SAC0307 mixed solder balls/Al joints with different bonding temperature under ultrasonic-assisted.

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Abstract

Purpose

This study aims to research properties of Cu/SAC0307 mixed solder balls/Al joints with different bonding temperature under ultrasonic-assisted.

Design/methodology/approach

A new method that 1 mm Zn particles and Sn-0.3Ag-0.7 (SAC0307) with a particle size of 25–38 mm were mixed to fill the joint and successfully achieved micro-joining of Cu/Al under ultrasonic-assisted.

Findings

The results indicated that when the bonding temperature was 180°C, there was only one layer of CuZn5 intermetallic compounds (IMCs) at the Cu interface. However, when the bonding temperature was 190°C, 200°C and 210°C, the Cu interface IMCs had two layers: for one layer, the IMCs near the Cu substrate were Cu5Zn8 and for another layer, the IMCs near the solder were CuZn5. In addition, the thickness of the Cu interfacial IMCs increased with the bonding temperature. In particular, the thickness of IMCs at the Cu interface of the Cu/Al joints soldered at 210°C was 4.6 µm, which increased by 139.6% compared with that of the Cu/Al joints soldered at 180°C. However, there was no IMC layer at the Al interface, but there might be a Zn–Al solid solution layer. The shear strength of Cu/Al joints soldered at 180°C was only 15.01 MPa, but as the soldering temperature continued to increase, the shear strength of the Cu/Al joints increased rapidly. When the soldering temperature was 200°C, the shear strength of the Cu/Al joints reached the maximum of 38.07 MPa, which was 153.6% higher than that at 180°C. When the soldering temperature was 180°C, the fracture of Cu/Al joints was mainly on the Al side. However, when soldering temperature was 190°C, 200°C and 210°C, the fracture of Cu/Al joints was mainly broken in the Zn particles layer.

Originality/value

A new method that 1 mm Zn particles and Sn-0.3Ag-0.7 (SAC0307) with a particle size of 25–38 mm were mixed to fill the Cu/Al joint at 210°C.

Details

Soldering & Surface Mount Technology, vol. 35 no. 4
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 7 March 2023

Tian Huang, Guisheng Gan, Cong Liu, Peng Ma, Yongchong Ma, Zheng Tang, Dayong Cheng, Xin Liu and Kun Tian

This paper aims to investigate the effects of different ultrasonic-assisted loading degrees on the microstructure, mechanical properties and the fracture morphology of…

Abstract

Purpose

This paper aims to investigate the effects of different ultrasonic-assisted loading degrees on the microstructure, mechanical properties and the fracture morphology of Cu/Zn+15%SAC0307+15%Cu/Al solder joints.

Design/methodology/approach

A new method in which 45 μm Zn particles were mixed with 15% 500 nm Cu particles and 15% 500 nm SAC0307 particles as solders (SACZ) and five different ultrasonic loading degrees were applied for realizing the soldering between Cu and Al at 240 °C and 8 MPa. Then, SEM was used to observe and analyze the soldering seam, interface microstructure and fracture morphology; the structural composition was determined by EDS; the phase of the soldering seam was characterized by XRD; and a PTR-1102 bonding tester was adopted to test the average shear strength.

Findings

The results manifest that Al–Zn solid solution is formed on the Al side of the Cu/SACZ/Al joints, while the interface IMC (Cu5Zn8) is formed on the Cu side of the Cu/SACZ/Al joints. When single ultrasonic was used in soldering, the interface IMC (Cu5Zn8) gradually thickens with the increase of ultrasonic degree. It is observed that the proportion of Zn or ZnO areas in solders decreases, and the proportion of Cu–Zn compound areas increases with the variation of ultrasonic degree. The maximum shear strength of joint reaches 46.01 MPa when the dual ultrasonic degree is 60°. The fracture position of the joint gradually shifts from the Al side interface to the solders and then to the Cu side interface.

Originality/value

The mechanism of ultrasonic action on micro-nanoparticles is further studied. By using different ultrasonic loading degrees to realize Cu/Al soldering, it is believed that the understandings gained in this study may offer some new insights for the development of low-temperature soldering methodology for heterogeneous materials.

Details

Microelectronics International, vol. 40 no. 2
Type: Research Article
ISSN: 1356-5362

Keywords

Article
Publication date: 14 October 2022

Meng Xiao, Nian Cai, Zhuokun Mo, Shule Yan, Nili Tian, Jing Ma and Han Wang

Statistical modeling has been successfully applied to integrated circuit (IC) solder joint inspection. However, there are some inherent problems in previous statistical modeling…

Abstract

Purpose

Statistical modeling has been successfully applied to integrated circuit (IC) solder joint inspection. However, there are some inherent problems in previous statistical modeling methods. This paper aims to propose an adaptive statistical modeling method to further improve the inspection performance for IC solder joints.

Design/methodology/approach

First, different pixels in the IC solder joint image were modeled by different templates, each of which was composed of the hue value of the pixel and a proposed template significance factor. Then, the potential defect image was obtained by adaptive template matching and the potential defect threshold for each pixel. It was noted that the number of templates, matching distance threshold, potential defect threshold and updating rate were adaptively updated during model training. Finally, the trained statistical model was used to inspect the IC solder joints by means of defect degree.

Findings

Experimental results indicated that the proposed adaptive schemes greatly contributed to the inspection performance of statistical modeling. Also, the proposed inspection method achieved better performance compared with some state-of-the-art inspection methods.

Originality/value

The proposed method offers a promising approach for IC solder joint inspection, which establishes different numbers of templates constructed by pixel values and template significance factors for different pixels. Also, some important parameters were adaptively updated with the updating of the model, which contributed to the inspection performance of the model.

Details

Soldering & Surface Mount Technology, vol. 35 no. 3
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 27 June 2022

Paulina Araújo Capela, Maria Sabrina Souza, Sharlane Costa, Jose C. Teixeira, Miguel Fernandes, Hugo Figueiredo, Isabel Delgado and Delfim Soares

In a printed circuit board assembly (PCBA), the coefficient of thermal expansion (CTE) mismatch between the solder joint materials has a detrimental impact on reliability. The…

Abstract

Purpose

In a printed circuit board assembly (PCBA), the coefficient of thermal expansion (CTE) mismatch between the solder joint materials has a detrimental impact on reliability. The mechanical stresses caused by the thermal changes of the assembly lead to fatigue and sometimes the failure of the solder joints. The purpose of this study is to propose a novel pad design to obtain an interrupted solder/substrate interface, to improve the PCBA reliability.

Design/methodology/approach

An interruption in the continuous intermetallic compound (IMC) layer of a solder joint was implemented, by the deposition of a silicone film in the pad, changing its geometry. That change allows a redistribution of stresses in the most ductile zone of the solder joint, the solder. The stress concentration at the solder/substrate interface is reduced, as well as the general state of stress at the solder joint.

Findings

A new way was developed to reduce the stress on the solder joints, caused by thermal variations, because of the different components CTEs mismatch. This new method consists of interrupting the IMC layers of the solder joint, strategically, redirecting the usual stresses to a more ductile area of the joint, the solder. This is an innovative method that allows increase the lifetime of PCBAs and the equipments.

Originality/value

In this study, a new pad design concept for higher solder joint reliability was developed to reduce the shear stress in the solder joints because of the CTE mismatch between all the solder joint components.

Details

Soldering & Surface Mount Technology, vol. 35 no. 2
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 4 May 2023

Muhammad Asyraf Abdullah and Siti Rabiatull Aisha Idris

Pb-free solders have been developed to replace the standard Sn–Pb eutectic solder since the prohibition on Pb used in solders. The Sn–Ag–Cu series of lead-free solders is the most…

Abstract

Purpose

Pb-free solders have been developed to replace the standard Sn–Pb eutectic solder since the prohibition on Pb used in solders. The Sn–Ag–Cu series of lead-free solders is the most extensively used in the electronics industry. The Ag3Sn, which forms during isothermal ageing, can significantly degrade solder joint reliability. Sn–Ag–Cu solder’s high price further hindered its use in the electronics industry. This paper aims to investigate different copper percentages into Sn–xCu solder alloy to improve its microstructure and strength performance.

Design/methodology/approach

The solder alloys used in this work were Sn–xCu, where x = 0.0, 0.3, 0.5, 0.7, 1.0 Wt.%, which was soldered onto electroless nickel immersion gold (ENIG) substrate using carbon dioxide (CO2) gas laser. Then these samples were subjected to isothermal aging for 0, 200, 500, 1,000 and 2,000 h. The Sn–xCu solder alloy was fabricated through a powder metallurgy process.

Findings

Microstructure characterization showed that Cu addition resulted in fine and rounded shape of Cu–Sn–Ni particles. Shear strength of Sn–xCu solder joints was increased with increasing Cu content, but at aging duration of 1,000 h, it dropped slightly. It is believed that the strength improved due to the increment of diffusion rate during isothermal aging.

Practical implications

In a Cu–Sn solder, the recommended amount is 1.0 Wt.% of Cu. In extensive aging procedures, it was discovered that Sn1.0Cu solder improved the reliability of solder joints. The findings indicated that the innovative solder alloys might satisfy the needs of high-reliability applications.

Originality/value

The study shows that the right amount of Cu enhances the solidification of Sn–Cu solder, increasing the shear force of the Cu–Sn solder joint. The Sn1.0Cu exhibits a ductile fracture on the top microstructure, improving the joint’s average shear strength.

Details

Soldering & Surface Mount Technology, vol. 35 no. 4
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 1 December 2022

Asyraf Abdullah and Siti Rabiatull Aisha Idris

This study aims to review the effect of copper percentage in Sn-based solder alloys (Sn-xCu, x = 0–5 Wt.%) on intermetallic compound (IMC) formation and growth after laser…

Abstract

Purpose

This study aims to review the effect of copper percentage in Sn-based solder alloys (Sn-xCu, x = 0–5 Wt.%) on intermetallic compound (IMC) formation and growth after laser soldering.

Design/methodology/approach

This study reviews the interfacial reactions at the solder joint interface, solder joint morphology and the theory on characterizing the formation and growth of IMCs. In addition, the effects of alloying and strengthening mechanism, including wettability, melting and mechanical properties are discussed.

Findings

This paper presents a comprehensive overview of the composition of tin-copper (Sn-Cu) solders with a potential to enhance their microstructure, mechanical characteristics and wettability by varying the Cu percentage. The study found that the best Cu content in the Sn-xCu solder alloy was 0.6–0.7 Wt.%; this composition provided high shear strength, vibration fracture life value and ideal IMC thickness. A method of solder alloy preparation was also found through powder metallurgy and laser soldering to improve the solder joint reliability.

Research limitations/implications

This study focuses on interfacial reactions at the solder joint interface, solder joint morphology, modelling simulation of joint strength and the theory on characterising the formation and growth of IMC.

Originality/value

The paper comprehensively summarises the useful findings of the Sn-Cu series. This information will be important for future trends in laser soldering on solder joint formation.

Details

Soldering & Surface Mount Technology, vol. 35 no. 3
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 1 January 2024

Rilwan Kayode Apalowo, Mohamad Aizat Abas, Muhamed Abdul Fatah Muhamed Mukhtar, Fakhrozi Che Ani and Mohamad Riduwan Ramli

This study aims to investigate the reliability issues of microvoid cracks in solder joint packages exposed to thermal cycling fatigue.

Abstract

Purpose

This study aims to investigate the reliability issues of microvoid cracks in solder joint packages exposed to thermal cycling fatigue.

Design/methodology/approach

The specimens are subjected to JEDEC preconditioning level 1 (85 °C/85%RH/168 h) with five times reflow at 270°C. This is followed by thermal cycling from 0°C to 100°C, per IPC-7351B standards. The specimens' cross-sections are inspected for crack growth and propagation under backscattered scanning electronic microscopy. The decoupled thermomechanical simulation technique is applied to investigate the thermal fatigue behavior. The impacts of crack length on the stress and fatigue behavior of the package are investigated.

Findings

Cracks are initiated from the ball grid array corner of the solder joint, propagating through the transverse section of the solder ball. The crack growth increases continuously up to 0.25-mm crack length, then slows down afterward. The J-integral and stress intensity factor (SIF) values at the crack tip decrease with increased crack length. Before 0.15-mm crack length, J-integral and SIF reduce slightly with crack length and are comparatively higher, resulting in a rapid increase in crack mouth opening displacement (CMOD). Beyond 0.25-mm crack length, the values significantly decline, that there is not much possibility of crack growth, resulting in a negligible change in CMOD value. This explains the crack growth arrest obtained after 0.25-mm crack length.

Practical implications

This work's contribution is expected to reduce the additional manufacturing cost and lead time incurred in investigating reliability issues in solder joints.

Originality/value

The work investigates crack propagation mechanisms of microvoid cracks in solder joints exposed to moisture and thermal fatigue, which is still limited in the literature. The parametric variation of the crack length on stress and fatigue characteristics of solder joints, which has never been conducted, is also studied.

Details

Soldering & Surface Mount Technology, vol. 36 no. 2
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 26 August 2022

Guisheng Gan, Shiqi Chen, Liujie Jiang, Zhaoqi Jiang, Cong Liu, Peng Ma, Dayong Cheng and Xin Liu

This study aims to evaluate the effect of thermal aging temperature on the properties of Cu/Cu joints.

Abstract

Purpose

This study aims to evaluate the effect of thermal aging temperature on the properties of Cu/Cu joints.

Design/methodology/approach

A new method that 1 um Zn-particles and Sn-0.3Ag-0.7Cu (SAC0307) with a particle size of 25–38 µm were mixed to fill the joint and successfully achieved the micro-joining of Cu/Cu under ultrasonic-assisted at low-temperature, and then the effect of thermal aging temperature on the properties of Cu/Cu joints was researched.

Findings

The composition of the intermetallic compounds (IMCs) on the upper and lower interfaces of Cu/SACZ/Cu joints remained unchanged, which was Cu5Zn8 in aging process, and the thickness of the IMCs on the upper and lower interfaces of the Cu/SACZ/Cu joints increased accordingly. Compared with the as-received joints, the thickness of the upper and lower interfaces IMCs of the soldering aged time for 24 h increased by 404.7% and 505.5% at 150ºC, respectively. The IMCs formation tendency and the IMCs growth rate of the lower interface are larger than those of the upper interface because the soldering seam near the IMCs at the upper and lower interfaces of the as-received joints were mostly white SAC0307 balls black Zn-particles, respectively. The growth activation energy of IMCs in the upper and lower interfaces is about 89.21 and 55.11 kJ/mol, respectively. Under the same aging time, with the increase of the aging temperature, the shear strength of Cu/SACZ/Cu joints did not change significantly at first before 150ºC. When the aging temperature reached 150ºC, the shear strength of the joints decreased significantly; the shear strength of the joints was the smallest at 150ºC for 24 h, which was 39.4% lower than that of the as-received joints because the oxidation degree of Zn particles in the joint with the increase of aging temperature and time.

Originality/value

Cu/Cu joints were successfully achieved under ultrasonic-assisted at low-temperature.

Details

Soldering & Surface Mount Technology, vol. 35 no. 2
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 30 September 2022

Guisheng Gan, Shiqi Chen, Liujie Jiang, Cong Liu, Tian Huang, Peng Ma, Dayong Cheng and Xin Liu

This study aims to research properties of Cu/SAC0307 mixed solder balls/Cu joints with different Zn-particles content at low-temperature under ultrasonic assisted.

Abstract

Purpose

This study aims to research properties of Cu/SAC0307 mixed solder balls/Cu joints with different Zn-particles content at low-temperature under ultrasonic assisted.

Design/methodology/approach

A new method that 1µm Zn particles and Sn-0.3Ag-0.7 (SAC0307) with a particle size of 25–38 µm were mixed to fill the joint and successfully achieved micro-joining of Cu/Cu under ultrasonic-assisted at low temperature.

Findings

The results showed that with a continuous increase in the Zn-particle content, the interfacial intermetallic compounds (IMCs) of the upper and lower interfaces of joints gradually changed from scallop-shaped Cu6Sn5 to wavy-shaped Cu5Zn8. Moreover, the IMC thickness of the upper/lower interface of joints first decreased and then increased with increasing Zn-particle content. The shear strengths of joints increased with Zn-particle content, the shear strength of joints went to a maximum of 29.76 MPa when the Zn-particle content was 40%, an increase of 62.6% compared to joints without Zn particles. However, as the Zn-particle content continued to increase, the shear strengths of the joints decreased. Additionally, when the Zn content increased to 50%, because the oxidation degree of Zn particles increased, the joints were mainly broken among Zn particles.

Originality/value

A new method that 1µm Zn particles and Sn-0.3Ag-0.7 (SAC0307) with a particle size of 25–38 µm were mixed to fill the Cu/Cu joint at 180°C.

Details

Soldering & Surface Mount Technology, vol. 35 no. 3
Type: Research Article
ISSN: 0954-0911

Keywords

1 – 10 of 77