Reflow profile optimization of <b><i>μ</i></b>BGA solder joints considering reflow temperature and time coupling

Tao, Bo; Yin, Zhouping; Ding, Han; Wu, Yiping

doi:10.1108/09540910910989420

Cited by 6 publications

(4 citation statements)

References 16 publications

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“…The interval width used in each iteration is based on the golden ratio (i.e. 0.618), which offers maximal efficiency (Bo et al , 2009). The peak temperature measured with the initial recipe is used to inversely seek the heat capacities of the package and PCB.…”

Section: Application Of the Reflow Recipe Generatormentioning

confidence: 99%

Reflow profiling with the aid of machine learning models

Lai

Park

2023

SSMT

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Purpose This paper aims to propose a method to quickly set the heating zone temperatures and conveyor speed of the reflow oven. This novel approach intensely eases the trial and error in reflow profiling and is especially helpful when reflowing thick printed circuit boards (PCBs) with bulky components. Machine learning (ML) models can reduce the time required for profiling from at least half a day of trial and error to just 1 h. Design/methodology/approach A highly compact computational fluid dynamics (CFD) model was used to simulate the reflow process, exhibiting an error rate of less than 1.5%. Validated models were used to generate data for training regression models. By leveraging a set of experiment results, the unknown input factors (i.e. the heat capacities of the bulkiest component and PCB) can be determined inversely. The trained Gaussian process regression models are then used to perform virtual reflow optimization while allowing a 4°C tolerance for peak temperatures. Upon ensuring that the profiles are inside the safe zone, the corresponding reflow recipes can be implemented to set up the reflow oven. Findings ML algorithms can be used to interpolate sparse data and provide speedy responses to simulate the reflow profile. This proposed approach can effectively address optimization problems involving multiple factors. Practical implications The methodology used in this study can considerably reduce labor costs and time consumption associated with reflow profiling, which presently relies heavily on individual experience and skill. With the user interface and regression models used in this approach, reflow profiles can be swiftly simulated, facilitating iterative experiments and numerical modeling with great effectiveness. Smart reflow profiling has the potential to enhance quality control and increase throughput. Originality/value In this study, the employment of the ultimate compact CFD model eliminates the constraint of components’ configuration, as effective heat capacities are able to determine the temperature profiles of the component and PCB. The temperature profiles generated by the regression models are time-sequenced and in the same format as the CFD results. This approach considerably reduces the cost associated with training data, which is often a major challenge in the development of ML models.

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Section: Application Of the Reflow Recipe Generatormentioning

confidence: 99%

Reflow profiling with the aid of machine learning models

Lai

Park

2023

SSMT

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“…The vapour temperature is constant and depends only on the boiling point of the working fluid. The spatial variation of temperature over the vapour area is used to regulate the temperature of the sample according to the desired temperature profile of the reflow soldering alloy (Bo et al, 2009;Livovsky et al, 2008). The Department of Technologies in Electronics had designed and built an experimental (laboratory) VPS chamber (Figure 3).…”

Section: Laboratory Self-developed Vapour Phase Soldering Chambermentioning

confidence: 99%

“…VPS, also well-known as condensation soldering, was used at the beginning of the early 1980s as one choice in which inert liquids based on fluorinated hydrocarbons or perfluoropolyethers are heated to a precisely defined boiling temperature. The temperature of the saturated vapour zone is the same as the boiling point of the vapour phase liquid (Géczy et al, 2016;Bo et al, 2009;Géczy et al, 2014). Standard VPS uses the latent heat of liquid vaporization to provide heat for soldering and hence to obtain reliable metal joints.…”

Section: Introductionmentioning

confidence: 99%

Real-time profiling of reflow process in VPS chamber

Livovský

Pietriková

2017

SSMT

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Purpose This paper aims to present a new method of real-time monitoring of thermal profiles applied in vapour phase soldering (VPS) reflow processes. The thermal profile setting is a significant variable that affects the quality of joints. The method allows rapid achievement of a required thermal profile based on software control that brings new efficiency to the reflow process and enhanced joint quality, especially for power electronics. Design/methodology/approach A real-time monitoring system based on computerized heat control was realized in a newly developed laboratory VPS chamber using a proportional integral derivation controller within the soldering process. The principle lies in the strictly accurate monitoring of the real defined reflow profile as a reference. Findings Very accurate maintenance of the required reflow profile temperature was achieved with high accuracy (± 2°C). The new method of monitoring and control of the reflow real-time profiling was verified at various maximal reflow temperatures (230°C, 240°C and 260°C). The method is feasible for reflowing three-dimensional (3D) power modules that use various types of solders. The real-time monitoring system based on computerised heat control helped to achieve various heights of vapour zone. Originality/value The paper describes construction of a newly developed laboratory-scale VPS chamber, including novel real-time profiling of the reflow process based on intelligent continuously measured temperatures at various horizontal positions. Real-time profiling in the laboratory VPS chamber allowed reflow soldering on 3D power modules (of greater dimensions) by applying various flux-less solder materials.

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“…It is known that the height of the saturated steam above the boiling liquid can vary by changing the heater's power input (Livovsky and Pietrikova, 2017). This area is characterised by different relative permittivity, dielectric losses and different amounts of dipole molecules, respectively, compared to the area over saturated vapours and polarising particles (Bo et al, 2009;Géczy et al, 2013;Illes and Geczy, 2012).…”

Section: Introductionmentioning

confidence: 99%

Measurement and regulation of saturated vapour height level in VPS chamber

Livovský

Pietriková

2019

SSMT

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Purpose The purpose of this paper is to investigate measurement and regulation of saturated vapour height level in vapour phase soldering (VPS) chamber based on parallel plate capacitor and retaining a stable saturated vapour level above the boiling fluid, regardless of the quantity and size of assembled components. Design/methodology/approach Development and realisation of capacitance sensor that sensitively senses the maximum height level of saturated vapour above the boiling fluid in the VPS chamber was achieved. Methodology of measurement is based on capacitor change from single air to a parallel plate, filled with two dielectric environments in a stacked configuration: condensed fluid and vapour (air). Findings An easy air plate capacitor immersed in the saturated vapour above the boiling fluid can serve as a parallel plate capacitor owing to the conversion of the air to the parallel plate capacitor. A thin film of fluid between the two capacitor plates corresponds to the height of the saturated vapour, which changes the capacity of the parallel plate capacitor. Originality/value Introducing the capacitive sensor directly into the VPS work space allows to achieve a constant height level of saturated vapour. Based on the capacity change, it is possible to control the heating power. There is a lack of information regarding measurement of stable height of vapour in the industry, and the present article shows how to easily improve the way to regulate the bandwidth of saturated vapour in the VPS process.

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Reflow profile optimization of μBGA solder joints considering reflow temperature and time coupling

Cited by 6 publications

References 16 publications

Reflow profiling with the aid of machine learning models

Reflow profiling with the aid of machine learning models

Real-time profiling of reflow process in VPS chamber

Measurement and regulation of saturated vapour height level in VPS chamber

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