UNSW researchers have investigated the impact of two types of soldering cluxs on Topcon-Zonnemodules under moist heat conditions and have shown that “non-clean” soldering colues can cause serious corrosion of silver-aluminum contacts for the front. The researchers have also discovered that denser metallization structures and the lower aluminum content improve corrosion resistance.
Researchers from the Australia’s University of New South Wales (UNSW) have assessed the impact of solder flux on the corrosion of metal contacts in solar cells based on tunneloxide -passivated contact (topcon) design under humid (dh) conditions.
The DH test is an accelerated test that test the reliability of modules under extreme humidity and heat. In its standard shape, the PV is placed in a controlled room with a temperature of 85 ° C and humidity of 85% for at least 1,000 hours.
“Our study PRovides PV manufacturers with fast, cheap diagnostics to detect solder-related reliability problems early in production, ”said the corresponding author of the research, Bram Hoex, said PV -Magazine. “It also helps industry to reduce warranty claims and performance losses as a result of fluid -caused corrosion.”
Solder fluxes are used to remove the oxide from the tab ribbons or bus ribbons during the module assembly process.
The scientists concentrated their analysis on the so -called “no -clean” fluxing, which should not be cleaned after soldering to simplify the production process. These fluxes remove oxides and create strong metallurgical bonds and leave minimal, non-conducting residues.
For testing, they used two commercial fluxes called Flux A and Flux B, where the last one is based on L-meal acid and the first on carbonic acid. They also used three commercial concon cells produced via the so-called laser-improved contact optimization (LECO) process in 2019, 2022 and 2023.
“All three n-type topcon cells show a similar structural design, in which the front has covered a boron-doted (P+) emitter by aluminum oxide (AL2O3) and hydrogenated silicon nitride (sinx), along with an H-pattern silver grid.” silicon dioxide (SIO2), phosphorus doped (N+) polysilicium, sinx and a similar H-pattern silver grid. “
The cells were divided into three groups: G1) Flux a front exposure; G2) Flux B exposure at the front; G3) Flux an exposure at the rear; G4) Flux B exposure at the rear; and G5) Control group without exposure to Flux. Fluxes were applied via spraying, where drying was executed on a hot plate at 85 ° C for a maximum of 10 m.
“Our analysis showed that rEssidues of ‘no-clean’ soldering flux can cause a serious corrosion of Topcon Front Silver-Aluminum (AG-AL) contacts under exposure to DH, increasing the resistance of the series and reducing efficiency, “said Hoex.” “Flux A, with halogens, is considerably more corrosive than Flux B, but both cause remarkable breakdown. “
The research team also showed that breakdown is largely absent on the AG AG pasta, which is more chemically stable, and that denser metallization structures and the lower aluminum content improve the corrosion resistance.
As possible solutions for these relegation problems, the academics suggested Non-Rapseld, DH tests at cell level to quickly identify flux-related risks before module assembly and select Flux formulases with minimal halogens and optimized acid content to reduce corrosion potential.
“We also recommend optimizing the composition and structure of the metallization paste to limit Flux infiltration,” Hoex concluded.
The research findings are available in the study “Assessment of the impact of Solar Energy Materials and Solar cells by solder Flux-Induced Corrosion on Topcon sun cells“Published in Solar energy materials and solar cells.
In February, researchers from the UNSW and the Chinese Canadian PV modulemaker Canadian-Zonne-Zonne-Energie investigated the effect of soldering flux on both top-cone and hetero junction (HJT) solar cells and have determined that the choice of this component is the key to prevent potential modulal plates.
Through this work, the scientists discovered that power losses in the HJT cells were caused by holes in the metallization layer, which facilitate the penetration of the solder clux, which led to chemical reactions that break down the performance. Moreover, this study has also established that the ITO layer in HJT cells is very susceptible to damage caused by solder flux.
A few months later, a group of researchers from the Korea Electronics Technology Institute (Keti) investigated how commercially available soldering fluxes indium tinoxide (ITO) electrodes in HJT can corrode and discover that there is a considerable risk of early demolition during the cell connection process.
Previous research by UNSW showed the impact of UV-induced demolition (UVID) in topcon cells, Relegation mechanisms of industrial-concon-zonnemodules encapsulated with ethylene vinylacetate (EVA) under accelerated damp conditionsAs well as the vulnerability of Topcon sun cells to contact corrosion and three types of Topcon sun module disruptions that were never detected in perc panels.
In addition, UNSW scientists investigated the breakdown of topcon sun cells induced by sodium under exposure to moist heating and the role of ‘hidden contaminants’ in the demolition of both top-cone and hetero junction devices.
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