Hongbo Xu, Mingyu Li, Yonggao Fu, Ling Wang and Jongmyung Kim
The aim of the paper is to control the height and shape of solder interconnects employed in electronic packaging applications by an induction heating reflow method, which can…
Abstract
Purpose
The aim of the paper is to control the height and shape of solder interconnects employed in electronic packaging applications by an induction heating reflow method, which can achieve the solder bumping and interconnecting process in a simple way.
Design/methodology/approach
Through the application of a designed induction heating system, a new methodology was forced to exhibit its certain qualities of forming and geometry controlling in the process. The corresponding temperature distribution has been analyzed based on a discussion of skin effects in metal spheres. The local melt phenomenon is observed and identified via the microstructures taken by scanning electron microscope (SEM).
Findings
In this work, barrel‐shaped solder joints with high heights and hourglass‐shaped solder joints can be obtained, which is good for improving the solder joint lifetime. The mechanism of solder joint height and shape control, which can be explained by the local melt phenomenon, is discussed and demonstrated via the different morphologies of Ag3Sn intermetallic compound (IMC).
Originality/value
The findings of this paper will help the understanding of the whole solder interconnecting process during induction heating reflow and the effects of electromagnetic fields on solder joint shape control.
Details
Keywords
Hongbo Xu, Mingyu Li, Yonggao Fu, Ling Wang and Jongmyung Kim
The purpose of this paper is to describe a local melt process of solder bumping employed in electronic packaging applications by an induction heating reflow method, for a combined…
Abstract
Purpose
The purpose of this paper is to describe a local melt process of solder bumping employed in electronic packaging applications by an induction heating reflow method, for a combined numerical and experimental study involving a temperature measurement using an infrared thermometer during the reflow process and microstructural observations after reflow, which can be used to control the height and shape of solder interconnects.
Design/methodology/approach
In the induction heating reflow process, the temperature distribution within the solder ball during the heating phase is of prime importance for the success of the process and the geometry control quality of final joints. This paper investigates the local melt process of solder balls reflowed onto Cu/Ni/Au pads, and focuses on the effect of the inductive heat on the thermal distribution during the melting process. A finite‐element model is applied to simulate the thermal field in a solder bump during the induction heating period in a reflow process. The effects of the coil current and the electromagnetic frequency on the thermal performance are investigated by using the validated thermal model. The local melt phenomenon in the solder joint is observed and identified by the microstructures taken using scanning electron microscopy.
Findings
In this paper, the numerical results match the experimental results quite well to validate the finite element modeling model. The local melt phenomenon predicted by simulation, and verified by experiments, is demonstrated to be capable of controlling the solder joint shape. Several parametric studies are carried out to understand the effects of different frequencies during assembly, and to suggest that a higher frequency is easier to get a greater temperature gradient, thus a more obvious local melt phenomenon, which is good for achieving the geometry control for solder joints.
Originality/value
The findings of this paper will help to understand the detailed solder bumping process during induction heating reflow and the effects of electromagnetic field frequency on solder joint shape controlling.