Realistic warpage evaluation of printed board assembly during reflow process

Chung, Soonwan; Kwak, Jae B.

doi:10.1108/ssmt-12-2014-0023

Cited by 21 publications

(7 citation statements)

References 11 publications

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“…It is extremely difficult to generate the geometric model owing to the complexity of the copper patterns. To alleviate this difficulty, homogenization of the complex copper layer has been conducted in existing works [ 16 , 17 , 18 , 19 ]. This method imposes equivalent material properties on the domain instead of modeling the cladding as it is.…”

Section: Methodsmentioning

confidence: 99%

Optimal Dummy Pattern Design Method for PWB Warpage Control Using the Human-Based Genetic Algorithm

Kim¹,

Lee²

2020

Micromachines

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In this work, a method that minimizes printed wiring board (PWB) warpage by dummy pattern design is proposed. This work suggests that dummy patterns are placed on a preset discretized location in the PWB to reduce the warpage. On each discretized candidate area, the dummy pattern can be set or unset. The warpage is numerically simulated based on direct modeling of the as-is PWB patterns to evaluate the warpage alongside the dummy pattern design set. The optimal pattern that minimizes warpage is determined using the human-based genetic algorithm where the objective function is evaluated by the structural simulation. The optimization method is realized in a spreadsheet that allows scripting language with which the input and output files of the simulation tool can be modified and read. Two different cases have been tested and the results show that the method can determine the optimal dummy patterns. The measured and simulated deflections agree well with each other. Moreover, it has been shown that certain dummy pattern designs that should reduce the warpage can be sought by the optimization.

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Section: Methodsmentioning

confidence: 99%

Optimal Dummy Pattern Design Method for PWB Warpage Control Using the Human-Based Genetic Algorithm

Kim¹,

Lee²

2020

Micromachines

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“…An optimised thermal profile and a well-controlled heating factor [practically the integral of the soldering profile above the melting point (Veselý et al , 2018)] are important for optimising the quality and reliability of the resulting joints. Overall, a proper soldering profile is important to enable best joint quality without typical failures [shorts, balling, voiding, microstructural optimizations (Lee, 2001)], and to avoid thermomechanical failures [CTE mismatch, warpage, shrinkage (Chung and Kwak, 2015)].…”

Section: Introductionmentioning

confidence: 99%

Modelling of temperature distribution along PCB thickness in different substrates during reflow

Straubinger

Bozsóki

Busek

et al. 2019

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Purpose In this paper, analytical modelling of heat distribution along the thickness of different printed circuit board (PCB) substrates is presented according to the 1 D heat transient conduction problem. This paper aims to reveal differences between the substrates and the geometry configurations and elaborate on further application of explicit modelling. Design/methodology/approach Different substrates were considered: classic FR4 and polyimide, ceramics (BeO, Al2O3) and novel biodegradables (polylactic-acid [PLA] and cellulose acetate [CA]). The board thicknesses were given in 0.25 mm steps. Results are calculated for heat transfer coefficients of convection and vapour phase (condensation) soldering. Even heat transfer is assumed on both PCB sides. Findings It was found that temperature distributions along PCB thicknesses are mostly negligible from solder joint formation aspects, and most of the materials can be used in explicit reflow profile modelling. However PLA shows significant temperature differences, pointing to possible modelling imprecisions. It was also shown, that while the difference between midplane and surface temperatures mainly depend on thermal diffusivity, the time to reach solder alloy melting point on the surface depends on volumetric heat capacity. Originality/value Results validate the applicability of explicit heat transfer modelling of PCBs during reflow for different heat transfer methods. The results can be incorporated into more complex simulations and profile predicting algorithms for industrial ovens controlled in the wake of Industry 4.0 directives for better temperature control and ultimately higher soldering quality.

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“…The most common assembly method for connecting electronic components to printed circuit boards (PCB) is reflow soldering technology. Depositing solder paste by stencil printing (Lau et al , 2016) onto the solder pads of the PCB (Chung and Kwak, 2015) is one of the most crucial steps of this technology (Skwarek et al , 2015); almost 60 per cent of soldering failures can be traced back to the printing process (Tsai, 2008). The process of stencil printing can be divided into two main parts: the print stroke of the solder paste and the time-gap between the strokes.…”

Section: Introductionmentioning

confidence: 99%

Investigating the thixotropic behaviour of Type 4 solder paste during stencil printing

Krammer

Szilágyi

Storcz

et al. 2017

SSMT

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Purpose A measurement method has been developed to reveal the viscosity change of solder pastes during stencil printing. This paper aimed to investigate thixotropic behaviour, the viscosity change of a lead-free solder paste (Type 4). Design/methodology/approach The viscosity change of the solder paste during stencil printing cycles was characterised in such a way that the time-gap between the printing cycles was modelled with a rest period between every rheological measurement. This period was set as 15, 30 and 60 s during the research. The Cross model was fitted to the measurement results, and the η0 parameter was used to characterise the viscosity change. The number of printing cycles necessary for reaching a stationary state in viscosity was determined for various rest periods. Findings It was found that the decrease in zero-shear viscosity is significant (25 per cent) in the first cycles, and it starts to become stationary at the sixth-seventh cycles. This means a printing process can provide the appropriate deposits only after the 7th cycle with the investigated Type 4 solder paste. Originality/value Time-dependent rheological behaviour of solder pastes was studied in the literature, but only the viscosity change over continuous time at constant shear rates was examined. The time-gap between stencil printing cycles was not considered, and thixotropic behaviour of solder pastes was also neglected. Therefore, the authors developed a measurement set which is able to model the effect of time-gap between printing cycles on the viscosity change of solder pastes.

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Realistic warpage evaluation of printed board assembly during reflow process

Cited by 21 publications

References 11 publications

Optimal Dummy Pattern Design Method for PWB Warpage Control Using the Human-Based Genetic Algorithm

Optimal Dummy Pattern Design Method for PWB Warpage Control Using the Human-Based Genetic Algorithm

Modelling of temperature distribution along PCB thickness in different substrates during reflow

Investigating the thixotropic behaviour of Type 4 solder paste during stencil printing

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