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The purpose of the present study was to review the thermo-mechanical challenges of reflowed lead-free solder joints in surface mount components (SMCs). The topics of the review include challenges in modelling of the reflow soldering process, optimization and the future challenges in the reflow soldering process. Besides, the numerical approach of lead-free solder reliability is also discussed.

Lead-free reflow soldering is one of the most significant processes in the development of surface mount technology, especially toward the miniaturization of the advanced SMCs package. The challenges lead to more complex thermal responses when the PCB assembly passes through the reflow oven. The virtual modelling tools facilitate the modelling and simulation of the lead-free reflow process, which provide more data and clear visualization on the particular process.

With the growing trend of computer power and software capability, the multidisciplinary simulation, such as the temperature and thermal stress of lead-free SMCs, under the influenced of a specific process atmosphere can be provided. A simulation modelling technique for the thermal response and flow field prediction of a reflow process is cost-effective and has greatly helped the engineer to eliminate guesswork. Besides, simulated-based optimization methods of the reflow process have gained popularity because of them being economical and have reduced time-consumption, and these provide more information compared to the experimental hardware. The advantages and disadvantages of the simulation modelling in the reflow soldering process are also briefly discussed.

This literature review provides the engineers and researchers with a profound understanding of the thermo-mechanical challenges of reflowed lead-free solder joints in SMCs and the challenges of simulation modelling in the reflow process.

The unique challenges in solder joint reliability, and direction of future research in reflow process were identified to clarify the solutions to solve lead-free reliability issues in the electronics manufacturing industry.

Reflow soldering is one of the most significant factors in determining solder joint defect rate. This study aims to introduce an innovative approach for optimizing the multiple performances of the reflow soldering process.

This study aims to minimize the solder joint defect rate of a ball grid array (BGA) package by using the grey‐based Taguchi method. The entropy measurement method was employed together with the grey‐based Taguchi method to compute for the weights of each quality characteristic. The Taguchi L18 orthogonal array was performed, and the optimal parameter settings were determined. Various factors, such as slope, temperature, and reflow profile time, as well as two extreme noise factors, were considered. The thermal stress, peak temperature, reflow time, board‐ and package‐level temperature uniformity were selected as the quality characteristics. These quality characteristics were determined using the numerical method. The numerical method comprises the internal computational flow that models the reflow oven coupled with the structural heating and cooling models of the BGA assembly. The Multi‐physics Code Coupling Interface was used as the coupling software.

The analysis of variance results reveals that the cooling slope was the most influential factor among the multiple quality characteristics, followed by the soaking temperature and the peak temperature. Experimental confirmation test results show that the performance characteristics improved significantly during the reflow soldering process.

The proposed approach greatly reduces solder joint defects and enhances solutions to lead‐free reliability issues in the electronics manufacturing industry.

The findings provide new guidelines to the optimization method which are very useful for the accurate control of the solder joint defect rate within components and printed circuit board (PCB) which is one of the major requirements to achieve high reliability of electronic assemblies.

The purpose of this paper is to develop a thermal coupling method of a ball grid array (BGA) assembly during a forced convection reflow soldering process.

The reflow oven was modeled in computational fluid dynamic (CFD) software (FLUENT 6.3.26) while the structural heating BGA package simulation was done using finite element method (FEM) software (ABAQUS 6.9). Both software applications were coupled bi‐directionally using the code coupling software MpCCI.

The convective heat transfer coefficient (h) simulated during the reflow process showed a sufficient view of the changing h in the BGA assembly of each reflow oven. The solder joints were found to experience phase change from solid to liquid during heating and liquid to solid during cooling. These phase changes were present at the melting temperature of the solder joint. The effect of the phase transition point was to cause a large range of temperature difference within the BGA assembly. This situation runs the risk of a skewing defect of components. The simulation results were compared with the experimental results and found to be in good conformity. In addition, the maximum thermal stress from simulation results was trapped in the interfaces between the solder joints and substrate, which tended to form the nucleation of initial crack.

The current study provides a methodology for designing a thermal profile for reflow soldering production.

The findings provide new guidelines for the thermal coupling method. This guideline is very useful for the accurate control of temperature distributions within components and printed circuit boards, which is one of major requirements for achieving high reliability in electronic assemblies.

The purpose of this paper is to develop thermal modelling to investigate the thermal response of sample boards (at board level) during the preheating stage of the reflow process and to validate with experimental measurements.

A thermal‐coupling method that adopted the Multi‐physics Code Coupling Interface (MpCCI) was utilized. A forced‐convection reflow oven was modelled using computational fluid dynamic software (FLUENT 6.3.26), whereas structural heating at the board level was conducted using finite‐element method software (ABAQUS 6.9).

The simulation showed a complex flow pattern having characteristics of a free‐jet region, stagnation‐flow region, wall jet‐region, recirculation region and vortices. A sharp maximum heat‐transfer coefficient was detected in the stagnation region of the jet, resulting in a spatial variation of local heat transfer on a thermal profile board (TPB). This coefficient affected the temperature distribution in the TPB with different specific heat capacitances and thermal conductivity of the structure. The simulation results were in good agreement with the experimental data and analytical model. The cold region and temperature uniformity (ΔT) increased with increasing complexity of the TPB. The cold region can occur in two possible locations in the TPB. Both occurrences can be related to the flow field of the reflow oven. ΔT of the TPB decreased when the conveyor speed (v) was reduced. A suitable conveyor speed (1.0 cm/s) was determined to maintain ΔT below 10°C, which prevented the thermally critical package from overheating.

The paper provies a methodology for designing a thermal profile for reflow soldering production.

The findings provide fundamental guidelines to the thermal‐coupling method at the board and package levels, very useful for accurate control of ΔT at the board and package levels, one of the major requirements in achieving a high degree of reliability for electronic assemblies.