Palladium Bumping: A Key to Tougher Tags

The wider the scope of applications for RFID grows, the more demanding some use conditions get. SMARTRAC’s exclusive and patented Palladium Bumping technology holds the key to manufacturing RFID transponders that last as long as the products they tag.


Products such as garments that are connected to the Internet of Things, providing a new means of communication between the brand and the consumer, depend for their functionality on RFID tags that last as long as the products do. Similarly, eID documents must not compromise on their RFID inlay’s reliability; and even “fun” tagging applications such as wristbands, tickets or access cards for theme and water parks must stand up to rough handling and difficult environments. These are just a few examples of how crucial durability and reliability are for RFID transponders. Both features are heavily influenced by the quality of the interconnection between the transponder’s IC and its antenna.


Technology of Choice for Harsh Conditions

As the world’s leading manufacturer of RFID transponders, SMARTRAC uses several technologies to connect the antenna to a transponder's chip. One proprietary method is Palladium Bumping, which in principle is a straightforward wafer bumping process that most if not all RFID manufacturers use. Material-wise, there is of course a major difference, as palladium normally is a material used in the diffusion layer, while bumps typically consist of gold, nickel plus gold, or alloys of tin, silver and copper.


Minimizing Dropout Rates

Due to the specific characteristics of palladium as a bumping material, the contact bumps applied on the wafer (chip) surface stand out for their exceptional roughness and formation of a lifted peripheral structure (crown), both of which are clearly visible on electron micrographs. This creates a substantially larger contact area between bump metal and antenna metal, reducing contact resistance and allowing the palladium bumped chip to be pressed directly onto the antenna structure. Non-Conductive Adhesives are also used, but only to provide mechanical stabilization and protection against moisture.


Cross-section micrograph - comparison between interconnection for an Ni/Au bump with ACP adhesive (left) and Pd Bump + NCA (right)
Micrograph view - Bump surface structure for an Ni/Ai bump (left) and Pd Bump (right)


This approach works exceptionally well. Wherever transponders have to cope with wet or hot/cold conditions that cause extensive aging and accelerate loss of connection between IC and antenna if conductive adhesive is used, Palladium Bumping excels. Comprehensive tests under such harsh environments prove that transponders utilizing SMARTRAC’s Palladium Bumping technology maintain a more stable read-range under thermal stress, and exhibit significantly lower dropout rates than transponders with nickel/gold bumps.


Fast Temperature Cycle Test 500 cycles by -40ºC/+85ºC (TC) for UHF inlays, blue dots Pd, Orange dots Ni/Au  Study Source: TU Dresden/Smartrac


Proven Technology, Excellent Perspectives

To date, SMARTRAC has produced more than 350 million palladium bumped HF and UHF transponders at its manufacturing site in Dresden, Germany, which are used in a wide range of application areas – primarily those that require superior durability and reliability. In the near future, advanced assembly technologies such as adhesive-free pressing-in and lamination will enable new, wearable products that activate an enhanced customer experience over the entire product lifecycle.

Palladium Bumping is feasible for wafers from several leading IC manufacturers. Interested in transponders that offer maximum durability and reliability?
For further information, please contact our sales and customer service team.

Palladium: A Valuable and Versatile Metal


Palladium is a rare and lustrous silvery-white metal which, together with platinum, rhodium, ruthenium, iridium and osmium, is a member of a group of elements referred to as the platinum group metals. These have similar chemical properties, but palladium has the lowest melting point and is the least dense. Palladium is widely used in catalytic converters and fuel cells, in dentistry, medicine, hydrogen purification, chemical applications, groundwater treatment and jewelry. In electronics, palladium can be found in multilayer ceramic capacitors in which palladium (and palladium-silver alloy) is used for electrodes. It is used for component and connector plating in consumer electronics and in soldering materials.