Cell Interconnection

Interconnection Technologies

Automated cell interconnection on industrial cell stringer for 3-5 busbars.
© Fraunhofer ISE

Automated cell interconnection on industrial cell stringer for 3-5 busbars.

High-efficiency module concept using shingled cell interconnection.
© Fraunhofer ISE

High-efficiency module concept using shingled cell interconnection.

In a PV module, solar cells are electrically connected to strings. The interconnection causes ohmic and optical losses in a module and affects the product reliability. In our Module Technology Center (Module-TEC) we use various soldering technologies and industrial stringing equipment for

  • 3, 4 and 5 busbars
  • Full- and half-sized cells
  • Heterojunction cells
  • Optically enhanced ribbons
  • Multi-Wire interconnection
  • Conductive adhesives
  • Shingle interconnection
  • Shaped ribbons and wires for back contact cells
  • MWT cell interconnection through conductive backsheets

Characterization Methods

X-ray analysis of solar cell metallization (front busbar and rear pad).
© Fraunhfoer ISE

X-ray analysis of solar cell metallization (front busbar and rear pad).

Metallographic inspection of solar cell joint (ribbon, solder, metallization paste, wafer).
© Fraunhofer ISE

Metallographic inspection of solar cell joint (ribbon, solder, metallization paste, wafer).

Measuring and optimizing the quality of the joints is primary to implement stable interconnection processes. With access to a wide range of characterization tools we have established specific analysis procedures:

  • Mechanical, optical and microstructural characterization of ribbons
  • Cross-section preparation and metallographic inspection
  • Optical microscopy and SEM
  • X-ray and 3D-µ computer tomography
  • Scanning acoustic microscopy for void detection
  • Kinetics of intermetallic phase formation
  • Electrical resistance mappings, electroluminescence
  • Peel force measurement at 90° and 180° peel angle
  • Conversion of peel forces into adhesive fracture energies
  • SmartCalc.Peel software for fast processing of peel test data
  • SmartCalc.CTM for ribbon dimensioning
  • Finite-Element-Modeling of stresses in solder joints
  • Finite-Element-Modeling of current flow