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압연을 이용한 Sn-37 Pb 와 Sn-3.5 Ag 솔더의 무플럭스 솔더링에 관한 연구
강춘식,정재필,홍순민,박창배,Ekere, Ndy N.,Rajkumar, D. 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.7
UBM-coated Si-wafer was fluxlessly soldered with glass substrate in N₂ atmosphere using rolled solder sheet. The bulk Sn-37wt%Pb and Sn-3.5wt%Ag solders were rolled to the sheet of 100㎛ thickness in order to achieve a bonding to Si-wafer by fluxless reflow process. The oxide layer on the solder surface was analysed by AES(Auger Electron Spectroscopy). Through rolling, the oxide layer on the solder surface became thin. It was possible to bond a solder disc to the Si-wafer with fluxless process in N₂ gas. Wetting angle of the fluxless soldered disc on the Si-wafer was about 9∼10°. The Si-wafer with a rolled solder was bonded to glass without flux in N₂ atmosphere. The joint was sound, and the thicknesse of intermetallic compound along the interface of Si-wafer was less than 2㎛.
A Study on the Comparison of Solderability Assessment
B. Salam,N. N. Ekere,J. P. Jung 한국표면공학회 2001 한국표면공학회지 Vol.34 No.2
The purpose of solderability assessment is to predict the effectiveness of soldering process. It is important for companies pursuing zero defects manufacturing because poor solderability is the major cause of two third of soldering failures. The most versatile solderability method is wetting balance method. However, there exist so many indices for wettability in the wetting balance test e.g. time to reach 2/3 values of maximum wetting force, time to reach zero wetting force, maximum withdrawal force. In this study, three solderability assessment methods, which were the maximum withdrawal force. the wetting balance and the dynamic contact angle (DCA), were evaluated by comparing each other. The wetting balance technique measures the solderability by recording the forces exerted from the specimen after being dipped into the molten solder. Then the force at equilibrium state can be used to calculate a contact angle, which is known as static contact angles. The DCA measures contact angles occurred during advancing and withdrawing of the specimen and the contact angles are known as dynamic contact angles. The maximum withdrawal force uses the maximum force during withdrawal movement and then a contact angle can be calculated. In this study, the maximum withdrawal force method was found to be an objective index for measuring the solderability and the experiment results indicated good agreement between the maximum withdrawal force and the wetting balance method.
Printing Morphology and Rheological Characteristics of Lead-Free Sn-3Ag-0.5Cu (SAC) Solder Pastes
Sharma, Ashutosh,Mallik, Sabuj,Ekere, Nduka N.,Jung, Jae-Pil The Korean Microelectronics and Packaging Society 2014 마이크로전자 및 패키징학회지 Vol.21 No.4
Solder paste plays a crucial role as the widely used joining material in surface mount technology (SMT). The understanding of its behaviour and properties is essential to ensure the proper functioning of the electronic assemblies. The composition of the solder paste is known to be directly related to its rheological behaviour. This paper provides a brief overview of the solder paste behaviour of four different solder paste formulations, stencil printing processes, and techniques to characterize solder paste behaviour adequately. The solder pastes are based on the Sn-3.0Ag-0.5Cu alloy, are different in their particle size, metal content and flux system. The solder pastes are characterized in terms of solder particle size and shape as well as the rheological characterizations such as oscillatory sweep tests, viscosity, and creep recovery behaviour of pastes.