Reflow soldering and isothermal solid-state aging of Sn-Ag eutectic solder on Au/Ni surface finish

As sapphire is an important substrate material, stringent surface quality requirements (i.e., surface finish and flatness) are required. In order to acquire the higher material removal rate and the better surface quality of sapphire, the solid state-reaction were introduced in this paper; abrasive of SiO2 and SiO2 with mixing the MgF2 power were compared to polish sapphire. The result showed that abrasive of SiO2 with mixing the MgF2 can obtain higher material removal rate and better surface quality. The result of the pr

Download Full-text

Microstructural evolution and interfacial reactions of fluxless-bonded Au-20Sn/Cu solder joint during reflow and aging

Journal of Materials Research ◽

10.1557/jmr.2007.0352 ◽

2007 ◽

Vol 22 (10) ◽

pp. 2817-2824 ◽

Cited By ~ 11

Author(s):

Jeong-Won Yoon ◽

Hyun-Suk Chun ◽

Hoo-Jeong Lee ◽

Seung-Boo Jung

Keyword(s):

High Temperature ◽

Solid State ◽

Intermetallic Compound ◽

Solder Joint ◽

Microstructural Evolution ◽

Surface Finish ◽

Solder Matrix ◽

Interfacial Reactions ◽

Cu Substrate ◽

Study Results

The microstructural evolution and interfacial reactions of fluxless-bonded, Au-20wt%Sn/Cu solder joint were investigated during reflow and aging. After reflowing at 310 °C, only one thick and irregularly shaped ζ(Cu) layer was formed at the interface. After the prolonged reflow reaction, the AuCu layer was formed between the ζ(Cu) layer and the Cu substrate. During reflowing, the Cu substrate reacted primarily with the ζ-phase in the solder matrix. The solid-state interfacial reaction was much faster at 250 °C than at 150 °C. After aging at 250 °C for 100 h, thick ζ(Cu), AuCu and AuCu3 IMC layers were formed at the interface. The formation of the AuCu3 intermetallic compound (IMC) was caused by Cu enrichment at the AuCu/Cu layer interface. After aging for 500 h, cracks were observed inside the interfacial AuCu layer. The study results clearly demonstrate the need for an alternative surface finish on Cu, to ensure the high temperature reliability of the Au-20Sn/Cu solder joint.

Download Full-text

Influence of Flux and Related Factors on Intermetallic Layer Growth within SAC305 Solder Joints

Materials ◽

10.3390/ma14247909 ◽

2021 ◽

Vol 14 (24) ◽

pp. 7909

Author(s):

Karel Dušek ◽

Petr Veselý ◽

David Bušek ◽

Adam Petráč ◽

Attila Géczy ◽

...

Keyword(s):

Image Analysis ◽

Layer Thickness ◽

Surface Finish ◽

Intermetallic Layer ◽

Layer Growth ◽

Solder Paste ◽

Sac305 Solder ◽

Related Factors ◽

Reflow Soldering ◽

Solder Mask

Flux contained in solder paste significantly affects the process of solder joint creation during reflow soldering, including the creation of an intermetallic layer (IML). This work investigates the dependence of intermetallic layer thickness on ROL0/ROL1 flux classification, glossy or matt solder mask, and OSP/HASL/ENIG soldering pad surface finish. Two original SAC305 solder pastes differing only in the used flux were chosen for the experiment. The influence of multiple reflows was also observed. The intermetallic layer thicknesses were obtained by the image analysis of micro-section images. The flux type proved to have a significant impact on the intermetallic layer thickness. The solder paste with ROL1 caused an increase in IML thickness by up to 40% in comparison to an identical paste with ROL0 flux. Furthermore, doubling the roughness of the solder mask has increased the resulting IML thickness by 37% at HASL surface finish and by an average of 22%.

Download Full-text

Intermetallic growth and shear strength of SAC305/EN-Boron

Soldering & Surface Mount Technology ◽

10.1108/ssmt-05-2015-0019 ◽

2016 ◽

Vol 28 (3) ◽

pp. 141-148

Author(s):

Hardinnawirda Kahar ◽

Zetty Akhtar Abd Malek ◽

Siti Rabiatull Aisha Idris ◽

Mahadzir Ishak

Keyword(s):

Shear Strength ◽

Solder Joint ◽

Surface Finish ◽

Air Cooling ◽

Slow Cooling ◽

Reflow Soldering ◽

Content Type ◽

Cu Substrate ◽

Lap Shear ◽

Scanning Electron

Purpose This paper aims to study the effect of aging and cooling rate on the reliability of the solder joint using electroless nickel boron (EN-Boron) as a surface finish in the electronic packaging area. Design/methodology/approach EN-Boron was plated on a Cu substrate through electroless plating method. This process was followed by reflow soldering of Sn–3.0Ag–0.5Cu solder alloy on metallized Cu substrate to form a joining. Then, the specimens were cooled using different cooling mediums such as air (slow cooling) with 15.7 °C/min and water (fast cooling) with 110.5 °C/min. After that, the specimens were subjected to isothermal aging at 150°C for 0, 250 and 1,000 h. Finally, they went through a lap shear test following ASTM D1002. Optical microscope and scanning electron microscopy were used for intermetallic compound (IMC) characterization. The type of IMC formed was confirmed by field emission scanning electron microscope-energy-dispersive X-ray spectroscopy (FESEM-EDX). Findings The results showed that the IMC type changed from the combination of Ni3Sn4 and (Ni, Cu)3Sn4 after reflow soldering into fully (Ni, Cu)3Sn4 when aged for 1,000 h. The formation of (Ni, Cu)3Sn4 and Cu3Sn underneath the IMC layer played a role in reducing the shear strength of joining. Overall, water cooling was reported to provide higher shear strength of solder joint compared to air cooling medium. Originality/value The shear strength when using EN-Boron as the surface finish is comparable to the surface finish conventionally used.

Download Full-text

The Effect of Bismuth on Intermetallics Growth between Lead-Free Solders and Electroless Nickel Immersion Silver (ENIMAG) Surface Finish

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.796.183 ◽

2019 ◽

Vol 796 ◽

pp. 183-188

Author(s):

Jaidi Zolhafizi ◽

Osman Saliza Azlina

Keyword(s):

Grain Size ◽

Intermetallic Compound ◽

Surface Finish ◽

Aging Treatment ◽

Electroless Nickel ◽

Optical Microscope ◽

Circuit Board ◽

Lead Free ◽

Reflow Soldering ◽

Immersion Silver

Surface finish is coating layer plated on a bare copper board of printed circuit board (PCB). Among PCB surface finishes, Electroless Nickel/Immersion Gold (ENIG) finish is a top choice among electronic packaging manufacturer due to its excellent properties for PCB. However, the use of gold element in ENIG is very high cost and the black pad issue have not been resolved. Thus, by introducing an Electroless Nickel/Immersion Silver (ENImAg) as alternative surface finish hopefully can reduce the cost and offer better properties. The aim of this study is to investigate the effect of bismuth on interfacial reaction during reflow soldering between Sn-2.5Ag (SA25), Sn-3.4Ag-4.8Bi (SAB3448) and ENIMAG surface finish. Solder balls with sizes of 500μm diameters were used. The characteristics of intermetallic compound (IMC) were analyzed by using scanning electron microscopy (SEM), optical microscope and energy dispersive x-ray (EDX). After reflow soldering, the result revealed that only the irregular circle-shape of (Cu,Ni)6Sn5IMC layer was formed at the interface and change to an irregular rod-like shape meanwhile the irregular needle-shape (Ni,Cu)3Sn4was appeared after aging treatment. The result also indicated that, the grain size and thickness of IMC for SAB3448 is smaller and thinner compared to the SA25. The IMC thickness is proportional to the aging duration and IMC morphology for both solder are became thicker, larger and coarser after isothermal aging. No bismuth particle has been detected on SAB3448 solder during top surface examination. In addition, the Bi has been observed can reduce the grain size and the growth rate of IMC. Keywords: ENIMAG, reflow soldering, lead-free solder, intermetallic compound, bismuth

Download Full-text