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Presentation Hall ICM - Internationales Congress Center München SEMICON EUROPA > Advanced Packaging Conference > Session 4: New Materials and Processing in Packaging
09:40-10:05 h | ICM - Internationales Congress Center München ICM Room 13b, 1st Floor
Subjects: SEMICON EUROPA
Chairman: Jens Mueller (, Test)
In packaging of power modules and small motors for automobile, surface finishes are required for proper solder joint formation, and Ni/Au or Ni/Pd/Au and so on are generally used as the metallization. As a deposition method of these metals, wet plating is drawing attention because of mass productivity and cost performance. Recently, SiC power devices have been developed to maximize the efficiency of the systems, however it will still take more time for the solution of thermal problems. Therefore some manufacturers has been already starting to evaluate high melting point solder (300 °C or higher). Another technical item to consider is to decrease in Si thickness. In this case, there are some problems regarding increasing wafer warpage after plating, suppression of Sn-Ni IMC thickness and crack after reflow due to the reflow temperature rising by change to high melting point solder. We found that low-P content electroless Ni can solve these issues. i) Improvement of wafer warpageAccording to Ni plated wafer warpage simulation by Stoney’s formula, when Si thickness is halved, the amount of the warpage becomes about four times greater. In our previous research, it was revealed that the differences of thermal expansion coefficient of each layer were more dominant than the internal stress of deposited Ni film for wafer warpage. From further investigation, we also found that thinner Ni improved wafer warpage regardless of P content of Ni deposit. ii) Suppression of Sn-Ni IMC thicknessBy rising reflow temperature, increasing of Sn-Ni IMC thickness and cracks are caused in case of conventional middle-P content electroless Ni. Low-P content electroless Ni deposit can suppress the Ni erosion amount than that of middle-P content. These phenomena are considered to be derived from crystal structure of Ni-P deposit. In this study, we considered the mechanism of technical advantages of Low-P content electroless Ni for thin wafer and high melting point solder.
Yuichi sakuma was employed at the C.Uyemura&Co., LTD. ,after graduated as Master of Science in chemistry from Kindai university ,Osaka Japan in 2007.Our company is the world leader in providing a solderable electroless nickel/immersion gold (ENIG) process in the printed circuit board field, and the knowledge and technique for UBM are supported from this background.