ultrasonic bonding of aluminium ribbons to … bonding of aluminium ribbons to molybdenum back...

Ultrasonic bonding of aluminium ribbons to molybdenum back contacted CIGS modules Hassan Basher 1,2 , Jorne Carolus 1,2 , Veronique Gevaerts 3 , Marc Meuris 2 and Michaël Daenen 1,2 Sample preparation In order to interconnect TFPV modules, a complete removal of the CIGS layer without damaging the Mo layer underneath is necessary. In this work the CIGS stack was removed mechanically. Literature has shown that the MoSe 2 layer can remain present after mechanical brushing. Measurement method The transmission line method (TLM) was used to measure Rc between the ribbon and the Mo layer. The four-point method was used to measure the resistance in the TLM measurements 1 . Experimental realization A Schunk DS-35 ultrasonic bonder was used. Ultrasonic bonding has three main variables that have an impact on welding quality which are; pressure, amplitude and maximum energy. Each parameter has a different impact on the interconnection. By changing the parameter values and measuring the Rc between Mo and the Al ribbon the interconnection quality can be optimized. Design of experiment (DOE) in JMP software was used for optimal parameter prediction 1 Hasselt University, IMO-IMOMEC, Wetenschapspark 1, 3590 Diepenbeek, Belgium 2 IMEC vzw, IMO-IMOMEC, Wetenschapspark 1, 3590 Diepenbeek, Belgium 3 ECN Solliance, High Tech Campus 21, 5656 AE Eindhoven, The Netherlands [email protected] Variables impacts - Graph builder of Rc Conclusion As a result of ultrasonic bonding tests that have been performed it can be concluded that the pressure has the highest impact on Rc, while the maximum energy has the lowest impact. Future potential • Peel tests will be carried out to identify the optimal ultrasonic parameters that give good pull strength in a 90° peel test. • Thermal cycling will be applied to investigate the influence of thermal mismatch on the Rc and pull strength Reference 1. Fadong Yan, D. J. ( 2013 EEEI .sdohteM nocennocretnI lleC SGIC fo noaulavE .) 39 th Photovoltaic Specialists Conference (PVSC). Tampa, FL, USA: IEEE Xplore. 2. A., B. S. (1998). Study of Indium Tin Oxide (ITO) for Novel Optoelectronic Devices. Bengal Telecommunication and Electric Corp (Betelco). Introduction The connection of the output terminals of thin film photovoltaic (TFPV) modules with a molybdenum (Mo) back contact is challenging because of the molybdenum diselenide (MoSe 2 ) layer which is formed during the selenization process. MoSe 2 is known to be highly resistive and previous research showed that high temperature soldering is not favourable for CIGS. In this work, we present the possibilities of ultrasonic bonding in order to create a low resistive and reliable connection of the output terminals. L 1 L 2 L 3 L 4 0 0.05 0.1 0.15 0.2 0.25 -5 0 5 10 15 20 Total Resistance (Ω) Pad Spacing (L) 2R c L x V I L 1 L 2 R s R c R c Mo layer Glass Al ribbon

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Ultrasonic bonding of aluminium ribbons to molybdenum back

contacted CIGS modules

Hassan Basher1,2, Jorne Carolus1,2, Veronique Gevaerts3, Marc Meuris2 and Michaël Daenen1,2

Sample preparationIn order to interconnect TFPV modules, a complete removalof the CIGS layer without damaging the Mo layerunderneath is necessary. In this work the CIGS stack wasremoved mechanically. Literature has shown that the MoSe2

layer can remain present after mechanical brushing.

Measurement methodThe transmission line method (TLM) was used to measureRc between the ribbon and the Mo layer. The four-pointmethod was used to measure the resistance in the TLMmeasurements1.

Experimental realizationA Schunk DS-35 ultrasonic bonder was used. Ultrasonicbonding has three main variables that have an impacton welding quality which are; pressure, amplitude andmaximum energy. Each parameter has a differentimpact on the interconnection. By changing theparameter values and measuring the Rc between Moand the Al ribbon the interconnection quality can beoptimized. Design of experiment (DOE) in JMPsoftware was used for optimal parameter prediction

1Hasselt University, IMO-IMOMEC, Wetenschapspark 1, 3590 Diepenbeek, Belgium2IMEC vzw, IMO-IMOMEC, Wetenschapspark 1, 3590 Diepenbeek, Belgium

3ECN Solliance, High Tech Campus 21, 5656 AE Eindhoven, The [email protected]

Variables impacts - Graph builder of Rc

ConclusionAs a result of ultrasonic bonding tests that havebeen performed it can be concluded that thepressure has the highest impact on Rc, whilethe maximum energy has the lowest impact.

Future potential• Peel tests will be carried out to identify the optimal ultrasonic

parameters that give good pull strength in a 90° peel test.• Thermal cycling will be applied to investigate the influence of

thermal mismatch on the Rc and pull strength

Reference 1. Fadong Yan, D. J. ( 2013 EEEI .sdohteM noticennocretnI lleC SGIC fo notiaulavE .)39 th Photovoltaic Specialists Conference (PVSC). Tampa,

FL, USA: IEEE Xplore.2. A., B. S. (1998). Study of Indium Tin Oxide (ITO) for Novel Optoelectronic Devices. Bengal Telecommunication and Electric Corp (Betelco).

IntroductionThe connection of the output terminals of thin film photovoltaic (TFPV) modules with a molybdenum (Mo) back contact is challengingbecause of the molybdenum diselenide (MoSe2) layer which is formed during the selenization process. MoSe2 is known to be highlyresistive and previous research showed that high temperature soldering is not favourable for CIGS. In this work, we present thepossibilities of ultrasonic bonding in order to create a low resistive and reliable connection of the output terminals.

0.05

0.1

0.15

0.2

0.25

-5 0 5 10 15 20

tal R

esis

tan

ce (Ω

)

Pad Spacing (L)