Studying heat transfer on inclined printed circuit boards during vapour phase soldering

Géczy, Attila; Nagy, Daniel; Illés, Béla; Fazekas, Laszlo; Krammer, Olivér; Busek, David

doi:10.1108/ssmt-11-2016-0029

Cited by 9 publications

(5 citation statements)

References 23 publications

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“…In production, it often occurs that the printed circuit board is assembled with components with very different heights. This is a problem of inhomogeneity of the distribution of the temperature fields because of the different heat consumption in the soldering process (Geczy et al, 2017). 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).…”

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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Section: Introductionmentioning

confidence: 99%

Measurement and regulation of saturated vapour height level in VPS chamber

Livovský

Pietriková

2019

SSMT

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“…Katsis and van Wyk (2013) investigate the effect of voids on the heat flow in power semiconductor packages, and they conclude that voids increase thermal impedance of the die-attach solder layer and reduce heat conduction from the silicon junction to the heat spreader. Many other items concerning simulations of heat and mass transport in the processes of vacuum VP soldering systems have been found in the literature such as Géczy et al (2017); Illés et al (2016), Illés et al (2017). The experimental results of solder joints thermal conductivity in relation to void contents have been presented by Górecki et al (2017).…”

Section: Introductionmentioning

confidence: 99%

Experimental approach to thermal conductivity of macro solder joints with voids

Sobolewski¹,

Dziurdzia

2019

SSMT

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Purpose The purpose of the paper is to experimentally evaluate the impact of voids on thermal conductivity of a macro solder joint formed between a copper cylinder and a copper plate by using reflow soldering. Design/methodology/approach A model of a surface mount device (SMD) was developed in the shape of a cylinder. A copper plate works as a printed circuit board (PCB). The resistor was connected to a power supply and the plate was cooled by a heat sink and a powerful fan. A macro solder joint was formed between a copper cylinder and a copper plate using reflow soldering and a lead-free solder paste SAC305. The solder paste was printed on a plate through stencils of various apertures. It was expected that various apertures of stencils will moderate the various void contents in solder joints. K-type thermocouples mounted inside cylinders and at the bottom of a plate underneath the cylinders measured the temperature gradient on both sides of the solder joint. After finishing the temperature measurements, the cylinders were thinned by milling to thickness of about 2 mm and then X-ray images were taken to evaluate the void contents. Finally the tablets were cross-sectioned to enable scanning electron microscopy (SEM) observations. Findings There was no clear dependence between thermal conductivity of solder joints and void contents. The authors state that other factors such as intermetallic layers, microcracks, crystal grain morfologyof the interface between the solder and the substrate influence on thermal conductivity. To support this observation, further investigations using metallographic methods are required. Originality/value Results allow us to assume that the use of SAC305 alloy for soldering of components with high thermal loads is risky. The common method for thermal balance calculation is based on the sum of serial thermal resistances of mechanical compounds. For these calculations, solder joints are represented with bulk SAC305 thermal conductivity parameters. Thermal conductivity of solder joints for high density of thermal energy is much lower than expected. Solder joints’ structure is not fully comparable with bulk SAC305 alloy. In experiments, the average value of the solder joint conductivity was found to be 8.1 W/m·K, which is about 14 per cent of the nominal value of SAC305 thermal conductivity.

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“…After establishing vacuum in the vacuum chamber, the assembly is kept there for some time (50 mbar, 10 s) and then it is transported into a cooling zone. Many aspects of vapour phase soldering have been reported recently, for example, the numerical modelling of the heat and mass transport processes in a vacuum vapour phase soldering system (Illés et al, 2017), studying heat transfer on inclined PCBs during vapour phase soldering (Géczy et al, 2017), influence of vapour phase soldering fluid Galden on wetting forces (Dušek et al, 2018). The issue of voids inside the solder joints was investigated by Skwarek et al (2013) and Synkiewicz et al (2014) where elimination of voids was achieved by applying vacuum at the end of the heating ramps of the vapour phase soldering process.…”

Section: Introductionmentioning

confidence: 99%

Convection vs vapour phase reflow in LED and BGA assembly

Dziurdzia

Sobolewski²,

Mikołajek³

2018

SSMT

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Purpose The aim of this paper is to evaluate using statistical methods how two soldering techniques – the convection reflow and vapour phase reflow with vacuum – influence reduction of voids in lead-free solder joints under Light Emitted Diodes (LEDs) and Ball Grid Arrays (BGAs). Design/methodology/approach Distribution of voids in solder joints under thermal and electrical pads of LEDs and in solder balls of BGAs assembled with convection reflow and vapour phase reflow with vacuum has been investigated in terms of coverage or void contents, void diameters and number of voids. For each soldering technology, 80 LEDs and 32 solder balls in BGAs were examined. Soldering processes were carried out in the industrial or semi-industrial environment. The OM340 solder paste of Innolot type was used for LED soldering. Voidings in solder joints were inspected with a 2D X-ray transmission system. OriginLab was used for statistical analysis. Findings Investigations supported by statistical analysis showed that the vapour phase reflow with vacuum decreases significantly void contents and number and diameters of voids in solder joints under LED and BGA packages when compared to convection reflow. Originality/value Voiding distribution data were collected on the basis of 2D X-ray images for test samples manufactured during the mass production processes. Statistical analysis enabled to appraise soldering technologies used in these processes in respect of void formation.

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Studying heat transfer on inclined printed circuit boards during vapour phase soldering

Cited by 9 publications

References 23 publications

Measurement and regulation of saturated vapour height level in VPS chamber

Measurement and regulation of saturated vapour height level in VPS chamber

Experimental approach to thermal conductivity of macro solder joints with voids

Convection vs vapour phase reflow in LED and BGA assembly

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