Kyung-Yeol Kim

Microstructures and Drop Impact Test of SAC305, Sn58%Bi and Epoxy Sn58%Bi SolderJoint on the OSP Surface Finished PCB Substrate

Lead free Sn3.0%Ag0.5%Cu (SAC305) solder and low temperature Sn58%Bi solder have been widely used to replace lead based solder alloys. Because Sn58%Bi solder has poor ductility and shock absorbance ability, previous researches have tried to improve its mechanical properties by adding additional elements, reinforcements, carbon nano tube (CNT) and polymer. The bonding strength and drop impact reliability of SAC305 solder, Sn58%Bi and epoxy contained Sn58%Bi solder (epoxy Sn58%Bi solder) assembled on the OSP surface finished PCB substrate were investigated using low speed shear and board drop impact tests. After soldering, Cu6Sn5 intermetallic compound (IMC) was formed in the solders and OSP surface finished PCB substrate joints. Bonding strength and drop reliability of epoxy Sn58%Bi solder had superior mechanical properties than those of SAC305 solder and Sn58%Bi solder. The crack in the solder joint of SAC305 after board drop impact testing takes place within the IMC layer. However, the crack at the solder joint of the Sn58%Bi after board drop impact testing occurred on the interface between IMC layer and Sn58%Bi solder and the crack in the solder joint of the epoxy Sn58%Bi presented within the solder, respectively.

Mechanical Property of SAC305 Ball-Grid Array and Epoxy Sn-58Bi Solder Joints with 85 °C/85% Relative Humidity Environmental Conditions

The ball-grid array (BGA) is widely used to reduce component size and it had advantages such as high I/O pins and fine pitch. Typical Sn-Ag-Cu (SAC) solder alloys are used for formation of BGA because SAC solder has excellent characteristics among lead-free solders. However, the electronic components assembled by SAC solder were easily damaged by heat during manufacture process because SAC solder had high melting point of 220 °C. To prevent these thermal damages, SAC305 BGA component assembled by Sn-58Bi solder paste has been studied because Sn-58Bi solder had low melting point of 139 °C. In generally, Sn-58Bi solder was improved by additional elements or polymer such as epoxy because Sn-58Bi had a brittle property. However, the epoxy Sn-58Bi solder did not guaranteed high environmental reliability such as high-temperature high-humidity (HTHH) test. Thus, we evaluated the shear strength of solder joints assembled by SAC305 BGA components with Sn-58Bi solder paste and epoxy Sn-58Bi solder paste. The shear strength of solder joints was evaluated by die shear test after HTHH test at the 85 °C/85% RH conditions. The Cu6Sn5 intermetallic-compound (IMC) at the interface of solder joints was observed by scanning electron microscope (SEM). The IMC thickness of Sn-58Bi solder joints was smaller than that of epoxy Sn-58Bi solder. The shear strength was improved up to 20% by epoxy addition. The shear strength of epoxy Sn-58Bi solder joints dramatically decreased after HTHH test for 100 h.

Effect of Epoxy on Mechanical Property of SAC305 Solder Joint with Various Surface Finishes Under 3-Point Bend Test

Microstructures and mechanical property of Sn-3.0Ag-0.5Cu (SAC305) and epoxy Sn-3.0Ag-0.5Cu (epoxy SAC) solder joints were investigated with various surface finishes; organic solderability preservative (OSP), electroless nickel immersion gold (ENIG) and electroless nickel electroless palladium immersion gold (ENEPIG). Bending property of solder joints was evaluated by 3-point bend test method. Microstructure and chemical composition of solder joints was characterized by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX), respectively. Epoxy did not effect on intermetallic compound (IMC) morphology. Scalloped shaped Cu6Sn5 IMC was observed at OSP surface finish. Chunky-like shaped and needle-like shaped (Ni,Cu)6Sn5 IMC were observed at the solder/ENIG joint and solder/ENEPIG joint, respectively. The bending cycles of SAC305/OSP joint, SAC305/ENIG joints and SAC305/ENEPIG joints were 720, 440 and 481 cycle numbers. The bending cycles of epoxy SAC and three types surface finished solder joints were over 1000 bending cycles. Under OSP surface finish, bending cycles of epoxy SAC solder was approximately 1.5 times higher than those of SAC305 solder joint. Bending cycles of epoxy SAC solder was over twice times higher than those of SAC305 solder with ENIG and ENEPIG surface finishes. The bending property of epoxy solder joint was enhanced due to epoxy fillet held the solder joint.

Effects of multipolar magnetic fields of the internal straight antenna in inductively coupled plasma

Summary form only given, as follows. In order to achieve the performance required for high resolution flat panel display (FPD) devices, especially for TFT-LCD of next generation, improved dry etch processes currently indispensable technology for semiconductor industry are required for volume manufacturing and superior critical dimension control. The plasma sources developed to date for the production of high-density and large-area plasmas are mainly focused on the externally planar ICP sources. However, due to their large inductance with the scale-tip to larger areas and the cost and the thickness of its dielectric material, the conventional ICP device using an external spiral antenna has reached its limit in extending the process area.