Microstructure and Composition of Au-Sn Eutectic Solder Electroplated from a Single Solution
- PDF / 369,234 Bytes
- 5 Pages / 595 x 842 pts (A4) Page_size
- 53 Downloads / 176 Views
0894-LL03-16.1
Microstructure and Composition of Au-Sn Eutectic Solder Electroplated from a Single Solution G. H. Jeong, J. H. Kim, Duhyun Lee, S. J. Suh AMPIT, Dept. of Advanced Materials Engineering, Sungkyunkwan University, 300, Chunchun-dong, Suwon, 440-746, South Korea ABSTRACT In this study, we produced Au-Sn alloy electroplated from a single solution and optimized the composition. The composition of electroplated Au-Sn alloy was Au-31.02 at.% Sn at the condition of 6 ms on - 4 ms off pulse current, 50 ℃ and 10 mA/cm2. Results in XRD analysis showed that Au-Sn alloy electroplated at DC 10 mA/cm2 had AuSn phase (ξ′) only and Au5Sn phase (δ) appeared with decreasing the pulsed current on time. Also micropatterned Au-Sn solder bump was produced by photolithography. Though it’s composition of Au-35.98 at.% Sn was not optimum, we tried to bond between Au-Sn solder bump and Si wafer that was coated with Ti (100 nm)/Au (300 nm). INTRODUCTION Gold-tin eutectic solder (Au-30 at.% Sn) has been widely used in optoelectronics and microelectronics industries for integrated chip or die bonding because it has a relatively high melting temperature (280 ℃), resistance for thermal fatigue, good creep behavior and corrosion resistance and wetting behavior. Conventionally Au-Sn alloys were deposited with two methods, one is the sequential electroplating of Au and Sn layers onto Au seed layers [13] and the other is the sequential vapor deposition technique. Au-Sn eutectic solder has been deposited preferentially with the former because it has economic advantage relative to the latter. But the sequential electroplating has disadvantages of post-deposition annealing, process complexity, cross-contamination between two bath and Sn layer oxidation [4]. Thus, the electroplating of Au-Sn alloy from a single solution has been investigated as an alternative to conventional methods for depositing Au-Sn alloy [5,6]. In this work, we produced Au-Sn alloy electroplated from a single solution and optimized the composition and the microstructure of near eutectic Au-Sn alloy. Also we produced the micro-patterned solder bump and tried to apply bonding process for wafer level packaging. EXPERIMENTAL DETAIL The solution used for electroplating of Au-Sn alloy was cyanide-based solution and
0894-LL03-16.2
contained gold (6 g/L) and tin (18 g/L). Platinum foil was used as the anode. The cathodes were Si wafers coated with Ti (100 nm)/Cu (300 nm). The area in cathodes was defined by a photoresist mask. Electroplating experiments were carried out under the direct current (DC) and the pulsed current (PC) conditions. The process temperature was varied from 40 ℃ to 60 ℃ and the current density was 5 mA/cm2 and 10 mA/cm2. Also on time of pulsed current was varied from 2 ms to 8 ms and cycle period was maintained at 10 ms. Photolithography was carried out for micro-patterning using the negative photoresist of PMER NCA9000 with the thickness of 15 ㎛. The size of solder bump patterned was 86×86 ㎛2 and conditions of electroplating were temperature of 50 ℃,
Data Loading...
