Mechanical reliability of self-aligned chip assembly after reflow soldering process

Abstract

Purpose This paper focuses on the reliability of the solder joint after the self-alignment phenomenon during reflow soldering. The aim of this study is to analyse the joint quality of the self-alignment assemblies of SnAg alloy solder joints with varying silver content. Design/methodology/approach The shear strength assessment was conducted in accordance with the JIS Z3 198-7 standard. The standard visual inspection of IPC-A-610G was also performed to inspect the self-alignment features of the solder joint samples. Statistical analysis was conducted to determine the probabilistic relationship of shear strength of the misalignment components. Findings The results from the mechanical reliability study indicate that there were decreasing trends in the shear strength value as misalignment offset increased. For shift mode configuration in the range of 0-300 µm, the resulting chip assembly inspection after the reflow process was in line with the IPC-A-610G standard. The statistical analysis shows that the solder type variation was insignificant to the shear strength of the chip resistor. The study concluded that the fracture occurred partially in the termination metallization at the lower part of the chip resistor. The copper content of the joint on that area shows that the crack occurred in the solder joint, and high silver content on the selected zone indicated that the fracture happened partially in the termination structure, as the termination structure of the lead-free chip resistor consists of an inner layer of silver and an outer layer of tin. Practical implications This study’s findings provide valuable guidelines and references to engineers and integrated circuit designers during the reflow soldering process in the microelectronics industry. Originality/value Studies on the effect of component misalignment on joint mechanical reliability are still limited, and studies on solder joint reliability involving the effect of differing contents of silver on varying chip component offset are rarely reported. Thus, this study is important to effectively bridge the research gap and yield appropriate guidelines in the potential industry.

Effects of alloying element on mechanical properties of Sn-Bi solder alloys: a review

“…The resistance of the solder joint to shear load before failure is measured as the shear strength of the solder joint. Shear strength also measures the actual configuration of the soldered structure (Ali Mokhtar et al , 2021) and is used to show the reliability of the solder joint (Frear et al , 2001). Excessive deformation in the solder composition affects the shear strength of the solder joint.…”

Reliability modeling and assessment of solder joints of electronic assemblies under mixed exposure to mechanical loads

“…The power electronic converter under the test (PECUT) consists of several parts including power semiconductor, electrolytic capacitors, and power inductors and controlling system. The most critical part in the PECUT is the solder joints of the components and the printed circuit boards (PCB) (Yang et al, 2020;Mohammad, 2020;Ali Mokhtar et al, 2020). In this regard, we considered three different chemical compositions for solder, namely Sn63Pb37, SAC387 and SAC405, in order to estimate the strength of the soldering under different conditions.…”