Solder wetting measurement of back contact paste using a wetting balance

In this work we present the impact of Watts-type nickel electrolytes on the contact microstructure of the screen-printed silver contacts of silicon solar cells. Both an SEM and TEM analysis were used to investigate the reasons for poor contact adhesion following nickel plating. A failing interface was identified and located exactly between the glass frit and the bulk silver inside the contact. A clearly visible gap occurs at this interface due to a chemical dissolution of the boundary layer between the glass and the silver. In TEM measurements, no distinctive features in the elemental composition were identified at the failing interface that might be responsible for the site-specific dissolution. This suggests that the dissolution starts at the very thin oxide layer between the glass and the silver. Furthermore it became clear that the electrolyte reaches the identified failing interface via pores and cavities in the screen-printed silver layer. Closing these cavities prior to nickel electrolyte exposure thus lead to significantly better contact adhesion values.

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“…[4][5][6] Due to this power loss and delamination of the front side contacts have also been observed. 7,8…”

mentioning

confidence: 99%

Microstructure Analysis of the Interaction between Watts-Type Nickel Electrolyte and Screen Printed Solar Cell Contacts

Kraft

Pernia

et al. 2014

ECS J. Solid State Sci. Technol.

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The impact of material composition and process parameters on the cSi solar cell interconnection

Schindler

Schneider

Klengel

et al. 2012

2012 4th Electronic System-Integration Technology Conference

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In this paper the effects of soldering process parameters and used materials on wettability characteristics and the mechanical properties in photovoltaics solder joints were investigated. The soldering and wetting behaviour of solder joints and its industry standard testing methods has been well studied in electronics packaging applications [1-3]. In photovoltaics lesser extent is made to characterize solder joint formation and their influencing parameters, such as process parameters, surface finishes, fluxes, solder composition, etc. [4-6]. In several experiments we focused on a comparative characterization of different process parameters, a variation in solder alloys and the aspects of different solar cells for solar cell string assembly. The mechanical strength of the solder joint interconnection was measured by mechanical pull tests, correlating the force-way-sequence with the fracture mode alongside the pad structure. We conducted wetting balance and surface measur ements on solar cell metallizations, indicating the significant difference between used cells and surface finishes on the interconnection process for the equipment suppliers

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Novel Approaches to Benchmarking Solar Cell Tabbing Solderability

Pfluke¹,

Lathrop²

2011

26th European Photovoltaic Solar Energy Conference and Exhibition; 1403-1408

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Solder wetting measurement of back contact paste using a wetting balance

Cited by 4 publications

References 3 publications

Microstructure Analysis of the Interaction between Watts-Type Nickel Electrolyte and Screen Printed Solar Cell Contacts

Microstructure Analysis of the Interaction between Watts-Type Nickel Electrolyte and Screen Printed Solar Cell Contacts

The impact of material composition and process parameters on the cSi solar cell interconnection

Novel Approaches to Benchmarking Solar Cell Tabbing Solderability

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