Pressureless Silver Sintering Technology from Henkel
Sintering is a process in which particles are joined together by heating the material in a sintering furnace below its melting point until there is particle adhesion. Conventional Ag sintering is achieved by applying both heat and pressure to the material, or device, until the metal joint is formed. The drawback to the pressure application technique in semiconductor packaging, however, is its volume limitation, as devices must be processed individually on capital-intensive die bonding systems. With Ablestik SSP2000, because the silver particles are joined via a unique surface tension mechanism, the pressure requirement is eliminated and the material can be cured in a standard batch oven at a temperature as low as 200 degree centigrade. In addition, Ablestik SSP2000 can be processed on standard die bonding systems, eliminating the need to reinvest in specialist equipment and making the transition from existing materials simple, fast and cost-effective.
“The ability to now exponentially increase UPH from traditional silver sintering techniques at roughly 30 units per hour to a remarkable 6,000 units per hour with the Henkel technology is incredible,” enthusiastically explains Henkel’s Dr. Michael Todd, Vice-President of Product Development and Engineering. “Now, semiconductor packaging specialists can have high volume and high reliability with a silver sintering material.”
While high UPH is a central advantage of Ablestik SSP2000, even more notable is the material’s thermal resistance and reliability. When compared to high-lead soft solders, which are the current material of choice for power semiconductor devices, Ablestik SSP2000 has far superior power cycling reliability. In power cycle testing where solder failed at 200 cycles, Henkel’s Ag sintering technology was able to reach more than 2,000 cycles before the first failure. With thermal conductivity and thermal resistance that are superior to that of solder, Ablestik SSP2000 offers better performance and reliability. For high power devices such as IGBTs, that presents tremendous latitude as compared to traditional solutions.
“Because of Ablestik SSP2000’s superior power handling performance, IGBT designers and manufacturers are now able to reduce the number of chips in a package and save on valuable device real estate,” comments Todd. “This material provides a technical solution that popular high-lead soft solders simply don’t have. What’s more, all the performance is achieved in a non-pressure process with lower curing temperatures, which is icing on the cake!”
Not only do semiconductor packaging specialists want higher throughput, higher performance materials, but are also actively seeking viable replacements to high-lead solders – particularly in the power device segment. The RoHS deadline for the elimination of lead-based materials from the power device market is currently set for 2014, which means that in less than three years suitable alternatives must be in place. For power device manufacturers, Henkel already has the solution with the first Ag sintering die attach material of its kind.
As Todd concludes, the flexibility of Henkel’s solution is simply untouchable. “The lead-free advantage, design latitude, thermal and electrical performance, reliability and high UPH capability – it’s all there. Our silver sintering technology is already proving its worth in the power device market, has shown great promise in the high power LED market and, frankly, is ideal for any application that requires high thermal capability in high volume. This will no doubt be a game-changer.”