Ultrasonic-Assisted Soldering of Low-Ag SAC Lead-Free Solder Paste at Low-Temperature

Abstract

SAC0307 (Sn-0.3mass%Ag-0.7mass%Cu) lead-free solder pastes were used to complete Cu/Cu joint by ultrasonic-assisted. Effect of nano-Ni particles and temperature on the performance of joint by ultrasonic-assisted with lead-free solder paste were investigated. The experimental results have shown that interfacial IMC of joint with SACP were typical scallop-type, but the type of interfacial IMC were serrated and became smoother after added nano-Ni particles. The IMC thickness was not more than 6.00 μm and the IMC thickness of SACP joint was slightly thick comparing with SACPC joint at the same temperature. Interfacial IMC of SACP joint at 210 C was mainly composed of a layer of thick Cu 6 Sn 5 and thin Cu 3 Sn, and the concentration gradients of Cu and Sn in IMC were also obviously. The composition of IMC was Cu 3 Sn 7 in SACPC joint at 210 C, there were no different and the composition was Cu 42.5 Sn 57.5 whether nano-Ni particles were added at 240 C. The strength of two kinds of joints were increased rst and then decreased with the increase of ultrasonic time at 210 C 220 C, but decreased in both joints at 240 C. The shear strength of SACP joint was only 31.59 MPa, but the shear strength of SACPC joint reached the peak value of 41.20 MPa at 5 s by ultrasonic-assisted at 210 C, were about 0.32 and 19.80 percent more than that of no ultrasonic-assisted. The shear strength of SACP joint and SACPC joint reached the peak value of 38.80 MPa and 41.96 MPa after ultrasonic vibration for 0 s at 240 C, but decreased to the minimum of 22.47 MPa and 21.11 MPa after ultrasonic-assisted at 5 s and 10 s, were about 42.09 and 49.69 percent less than that of no ultrasonic-assisted respectively. Ultrasound can help ll the solder seam to increase the shear strength, but slag inclusion and foreign gases would gather and grow up to lead decreasing of the shear strength at 210 C 220 C. Slag inclusion and foreign gases were wrapped into the seam and not easy to over ow under the liquid state in the liquidus nearby, would gather to the interface of IMC/solder and grow up to lead decreasing of the shear strength under the the ultrasonic vibration at 240 C. Nano-Ni particles also played a part in increasing the strength of joints.

Properties of Cu/Zn+15%SAC0307+15%Cu/Al joints by different ultrasonic-assisted degrees

“…Nowadays, ultrasonic soldering technology has aroused ever-increasing attention and intense efforts (Zulkifli et al, 2019). Especially in electronic packaging industry, research mainly focus on metal substrates such as Al (Guo et al, 2017), Cu (Gan et al, 2019), ceramic materials igure 2 Soldering seam of joints by different ultrasonic loading degrees (Kolenak et al, 2021) or soldering of metals and ceramics (Yi et al, 2022;Li et al, 2022a). , the maximum shear strength of joint could reach 22.76 MPa under a 30 s ultrasonic-assisted time.…”

“…Gan et al (2021bGan et al ( , 2020 adopted a new approach by mixing 45 mm Zn particles with 20-38mm SAC0307 particles to form a sold-filled joint, successfully realizing the low-temperature soldering of Cu-Cu at 220°C by ultrasound-assisted soldering, where the shear strength of joint could reach 34.2 MPa. In addition, 0.5% Ni nanoparticles (80 nm) were added to the SAC0307 particles to improve the joint performance, and the Cu-Cu joint with shear strength up to 41.20 MPa was obtained under the conditions of 5 s and 210°C with ultrasonic-assisted soldering (Gan et al, 2018). Jiang et al (2021) has successfully realized the high-quality soldering of Cu and Al at a low temperature of 220°C by using the dual ultrasonic-assisted technology.…”

Influence of aging temperature on the properties of Cu/(SAC0307 powder +Zn-particles)/Al joints ultrasonic-assisted soldered at low temperature

“…However, investigations have found that, as the Ag content decreases, SAC solders also have some disadvantages, such as a high melting temperature, thick intermetallic compounds (IMCs) and insufficient oxidation resistance characteristics, which can lead to poor reliabilities of solder joints (Ma et al, 2019;Jing et al, 2017). A lot of research has been conducted to solve these problems (Sun et al, 2016;Gan et al, 2013aGan et al, , 2013bGan et al, 2018). However, these researches had little effect in improving solder performance, and, for the solderability and the melting temperature of the solder, it was difficult to achieve satisfactory results.…”

Properties of Cu/SAC0307 mixed solder balls/Cu joints with different Zn-particles content at low-temperature under ultrasonic assisted

“…However, these studies had little effect in improving the solder performance, solderability and the melting temperature (Jing et al, 2017;Ma et al, 2017; The current issue and full text archive of this journal is available on Emerald Insight at: https://www.emerald.com/insight/0954-0911.htm Zhao et al, 2016). Recently, several different methods were proposed to decrease soldering temperatures including using composite solder (mixed by high-and low-temperature solder) (Shen et al, 2019), nanosolders (Roshanghias et al, 2015), nanoparticle reinforced composite solder or solder paste (Rajendran et al, 2022;Min et al, 2019), nanoparticle reinforced solders or solder pastes and low-temperature stir soldering simultaneously (Gan et al, 2013a;Gan et al, 2013b;Gan et al, 2013c), nanoparticle reinforced solder or solder paste and ultrasonic soldering simultaneously (Gan et al, 2019;Gan et al, 2018;Gan et al, 2017) and so on. But all needed flux.…”