Stress and Strain Analysis of QFN Solder Joint under Torsional Loading

The 3D finite element analysis model of QFN solder joints was established. The influence of various factors on the torsional stress and strain of QFN solder joints under the same torsional loading conditions was studied by single factor analysis. SAC305 solder joint materials were selected for solder joint materials and analyzed. The effect of the point length, the width of the solder joint and the height of the solder joint on the torsional stress and strain of the solder joint obtained the stress and strain distribution of the QFN solder joint. The results show that the maximum stress of the maximum stress in the QFN solder joints appears on the side in contact with the PCB board when the torsional load is applied to the same displacement load. As the height of the solder joint increases, the maximum torsional stress and strain in the solder joints As the length of the solder joint increases, the maximum torsional stress and strain in the solder joint increases; as the solder joint width increases, the maximum torsional stress and strain in the solder joint decreases.

I. Introduction

With the rapid development of electronic technology, the miniaturization and high density of packaging and the emergence of a variety of new packaging technologies continue to emerge^[1], and the requirements for the quality of electronic assembly are also increasing. QFN (Quad Flat No-lead Package) is an emerging surface mount chip packaging technology with small pad size^[2] , small size and plastic as sealing material. The exposed pad on the bottom of the bottom is soldered to the heat sink of the PCB. This makes QFN have excellent electrical and thermal properties^[3]. However, due to the gradually decreasing solder joint size^[4], various reliability problems are easily brought about, and the solder joints are easily subjected to external forces such as torsional loads, thereby causing corresponding stresses in the QFN solder joints, causing the solder joints to fail, thereby affecting The ultimate reliability of electronic products is therefore necessary to study the reliability of QFN solder joints subjected to torsional loads^[5].