Effect of No-Clean Flux Residues on the Performance of Acrylic Conformal Coating in Aggressive Environments

Rathinavelu, Umadevi; Jellesen, Morten Stendahl; Møller, Per; Ambat, Rajan

doi:10.1109/tcpmt.2012.2186456

Cited by 25 publications

(10 citation statements)

References 8 publications

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“…The typical soldering temperatures used in this study for the estimation of degradation tendencies between various contamination types turned out to be insufficient for reducting the residue amount. Typically, the temperatures experienced by the top and bottom parts of a PCBA (175°C and 250°C, respectively) last for only approximately 45 s (Piotrowska et al (2017) (Verdingovas et al , 2015a) (Hansen et al , 2009) (Verdingovas et al , 2015b) (Rathinavelu et al , 2012) (Minzari, 2010) during soldering. The levels of activators present on the surface after 45 s treatments were still relatively high (Figures 3, 5 and 6), and only prolonged heating at 245°C resulted in a significant residue amount reduction.…”

Section: Discussionmentioning

confidence: 99%

“…Due to the hygroscopic nature of WOAs, the adsorption and absorption of moisture on the PCBA surface is facilitated (Verdingovas et al , 2013) at the critical relative humidity (RH) levels characteristic for each WOA. This results in the formation of a water layer with varying conductivity, depending on the type of WOA (Rathinavelu et al , 2012). Under bias conditions, the presence of an electrolyte between the conductors leads to leakage currents and reduction in the surface insulation resistance (SIR), which may eventually result in corrosion effects such as ECM (Verdingovas et al , 2015a) (Jellesen et al , 2012) (Zhan et al , 2008) (Jellesen et al , 2010) (Galvan et al , 1996) (Schmitt-Thomas and Schmidt, 1994) (Turbini et al , 1992).…”

Section: Introductionmentioning

confidence: 99%

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Thermal decomposition of binary mixtures of organic activators used in no-clean fluxes and impact on PCBA corrosion reliability

Piotrowska

Ambat

2019

SSMT

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Purpose The purpose of this paper is to investigate the decomposition behavior of binary mixtures of organic activators commonly used in the no-clean wave flux systems upon their exposure to thermal treatments simulating wave soldering temperatures. The binary blends of activators were studied at varying ratios between the components. Design/methodology/approach Differential scanning calorimetry and thermogravimetric analysis were used to study the characteristics of weak organic acid (WOA) mixtures degradation as a function of temperature. The amount of residue left on the surface after the heat treatments was estimated by gravimetric measurements as a function of binary mixture type, temperature and exposure time. Ion chromatography analysis was used for understanding the relative difference between decomposition of activators in binary blends. The aggressivity of the left residue was assessed using the acidity indication gel test, and effect on reliability was investigated by DC leakage current measurement performed under varying humidity and potential bias conditions. Findings The results show that the typical range of temperatures experienced by electronics during the wave soldering process is not sufficient for the removal of significant activator amounts. If the residues contain binary mixture of WOAs, the final ratio between the components, the residue level and the corrosive effects depend on the relative decomposition behavior of individual components. Among the WOA investigated under the conventional wave soldering temperature, the evaporation and removal of succinic acid is more dominant compared to adipic and glutaric acids. Practical implications The findings are attributed to the chemistry of WOAs typically used as flux activators for wave soldering purposes. The results show the importance of controlling the WOA content and ratio between activating components in a flux formulation in relation to its tendencies for evaporation during soldering and the impact of its residues on electronics reliability. Originality/value The results show that the significant levels of flux residues can only be removed at significantly higher temperatures and longer exposure times compared to the conventional temperature range used for the wave soldering process. The potential corrosion issues related to insufficient flux residues removal will be determined by the residue amount, its composition and ratio between organic components. The proper time of thermal treatment and careful choice of fluxing formulation could ensure more climatically reliable product.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermal decomposition of binary mixtures of organic activators used in no-clean fluxes and impact on PCBA corrosion reliability

Piotrowska

Ambat

2019

SSMT

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“…This is expected, as the ionic contaminants under the coating will influence the water transport through the coating due to osmotic pressure, while the adhesion of the coating is affected by the contamination at the interface. The blisters formed due to water absorption to the interface and delamination of the coating can induce under-film corrosion, which is reported to be more severe than the open corrosion cell formation due to the nature of the occluded solution (Rathinavelu et al, 2012;Pommersheim and Nguyen, 1998). At the gel-polymer interface, an uninterrupted conductive path of coalescing aqueous droplets will be formed in the presence of water-soluble substrate impurities (Tencer, 2000), and water intake through the coating can form an electrolyte at the interface by combining with the ions, eventually leading to corrosion (Rathinavelu et al, 2012;Zhan et al, 2006;Dou et al, 2008).…”

Section: Discussionmentioning

confidence: 99%

Contamination profile on typical printed circuit board assemblies vs soldering process

Conseil

Jellesen

Ambat

2014

Soldering &Amp; Surface Mount Technology

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Purpose – The purpose of this paper was to analyse typical printed circuit board assemblies (PCBAs) processed by reflow, wave or selective wave soldering for typical levels of process-related residues, resulting from a specific or combination of soldering processes. Typical solder flux residue distribution pattern, composition and concentration are profiled and reported. The effect of such contaminants on conformal coating was tested. Design/methodology/approach – Presence of localized flux residues was visualized using a commercial residue reliability assessment testing gel test and chemical structure was identified by Fourier transform infrared spectroscopy, while the concentration was measured using ion chromatography, and the electrical properties of the extracts were determined by measuring the leak current using a twin platinum electrode set-up. Localized extraction of residue was carried out using a commercial critical contamination control extraction system. Findings – Results clearly show that the amount and distribution of flux residues are a function of the soldering process, and the level can be reduced by an appropriate cleaning. Selective soldering process generates significantly higher levels of residues compared to the wave and reflow process. For conformal coated PCBAs, the contamination levels generated from the tested wave and selective soldering process are found to be enough to generate blisters under exposure to high humidity levels. Originality/value – Although it is generally known that different soldering processes can introduce contamination on the PCBA surface, compromising its cleanliness, no systematic work is reported investigating the relative levels of residue introduced by various soldering processes and its effect on corrosion reliability.

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“…The connecting wires should be pulled out through the reserved holes on both sides of the test chamber to guarantee the power supply constantly. In order to avoid damaging the test chamber and assuring the test process, deionized water is added to water storage tank regularly on trail . And the surfaces of target boards are maintained free of contamination.…”

Section: Methodsmentioning

confidence: 99%

Humidity Threshold Model of Numerical Control Multilayer Printed Circuit Board for Electrochemical Migration

Xie

Tang

Chen

et al. 2014

Quality & Reliability Eng

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In this paper, numerical control finished boards are employed as test samples to evaluate the effects of the environment and bias voltage on the surface insulation resistance of printed circuit boards. The results indicate that the surface insulation resistance degradation processes leading to failure exhibit a relative humidity threshold value, which is mostly related to temperature, test patterns, and bias voltage. Then, a humidity threshold model is built on the basis of electrochemical migration to quantify the relationship between the relative humidity threshold and conductor spacing and bias voltage under the controlled environments. Finally, experiments and tests have been carried out to validate the effectiveness and practicability of the model. Furthermore, the residual analysis is applied to check the fitting effect of the proposed model. According to the new model, the humidity threshold value can be obtained to provide the guidance for reliability problems in application. It is crucial to the design and deployment of reliable printed circuit boards. . Her main research interests include reliability analysis, reliability testing, reliability assessment, and reliability growth on numerical control system.Hangjun Zhang holds a Masters degree in Mechanical Engineering from the Tianjin University of Technology and Education, Tianjin, China. He is also a member

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Effect of No-Clean Flux Residues on the Performance of Acrylic Conformal Coating in Aggressive Environments

Cited by 25 publications

References 8 publications

Thermal decomposition of binary mixtures of organic activators used in no-clean fluxes and impact on PCBA corrosion reliability

Thermal decomposition of binary mixtures of organic activators used in no-clean fluxes and impact on PCBA corrosion reliability

Contamination profile on typical printed circuit board assemblies vs soldering process

Humidity Threshold Model of Numerical Control Multilayer Printed Circuit Board for Electrochemical Migration

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