02/01/2010, Irvine, California

 

Photovoltaic Modules get a Charge from New Electrically Conductive Adhesives

For high reliability applications such as satellite, automotive, medical and telecom products, electrically conductive adhesives are often used as an alternative to traditional solders. Their benefits are many but, for these applications, conductive adhesives deliver low temperature processing, fine-pitch capability and improved thermal cycling resistance.

These advantages are arguably compelling, but electrically conductive adhesives have had limited success on common electronic metals such as copper and Sn and, therefore, have been used most often on noble metallizations like gold and silver palladium on ceramic substrates. While conductive adhesives may also provide benefits to the thin film solar cell market and the silicon solar cell segment, their limitations on copper and Sn have slowed their adoption.

To address this limitation, new development work has resulted in the formulation of electrically conductive adhesives that overcome the drawbacks of older-generation systems. Recent work has shown that the unstable contact resistance of electrically conductive adhesives on copper and tin is due to electrochemical corrosion of these metals under elevated temperature and humidity conditions. Based on these fundamental understandings, Henkel has developed a new class of conductive adhesives which exhibit exceptional contact resistance stability on surfaces including OSP copper, Sn alloys and even 100% Sn. The result is a new electrically conductive adhesive product – called Hysol ECCOBOND CE 3103WLV -- for use on thin film solar substrates.

To demonstrate the performance of Henkel’s new electrically conductive adhesives for thin-film solar cell applications, a test device with indium tin oxide (ITO) terminations was bonded to non- noble metal (Sn) interconnection tabs using the electrically conductive adhesives. All of the other adhesives that were tested were unable to provide a stable electrical contact resistance.
As the electrically conductive adhesives are processed at temperatures significantly below the melting temperature of traditional SnPb and lead-free SnAg solders, the reliability data from this report indicate that electrically conductive adhesives containing new corrosion inhibitors are a viable alternative to solder interconnections for applications requiring low-temperature processing.

These results are very encouraging for the photovoltaic market sector, as manufacturers can now incorporate a low temperature process into their operations without risking any performance sacrifice. Henkel’s Hysol ECCOBOND CE 3103WLV is the ideal answer to address the requirements of next-generation solar cell manufacture.

For more information on Henkel’s complete line of solar cell adhesives, please call Henkel at 949-789-2500 or log onto www.henkel.com/electronics.