Abstract: Due to environmental concerns, lead-free solders were introduced to replace the lead-based solders in microelectronics devices technology. Although there are many lead-free solders available, the Sn-Ag-Cu solders are considered the best replacement due to their good wettability and joint strength. Although the Sn-Ag-Cu solders are accepted widely, but there are still some room for improvement. In this study, 1wt% Zn, which can be considered high percentage for a dopant, was added into the solder via powder metallurgy route. The effects of adding this dopant into the Sn-3.5Ag-1.0Cu solder on the interface intermetallic and thickness were investigated. The intermetallics phases formed were observed under Scanning Electron Microscope (SEM) and their thicknesses were measured. The SEM results showed the presence of Cu6Sn5, Cu3Sn and (Cu,Zn)6Sn5 intermetallics. It can be concluded that Zn behaved as retarding agent and significantly retarded the growth of Cu-Sn intermetallics.
Abstract: The wettability of Sn-Cu-Ni with Germanium (Ge) additions of 0 ppm, 10 ppm, 60 ppm, 100 ppm and 200 ppm were investigated with Gen3 machine. The range of the wettability shows the lowest and the highest reading of wetting time and maximum force. Three different conditions were investigated which consist of as soldered, reflowed and aged. Further interfacial IMC observation was done for 0 ppm and 60 ppm of Ge to investigate the growth of interfacial IMC after thermal aging. From the measurement, the thickness of IMC for 0 ppm Ge is 2.075μm, 3.936μm and 4.502μm with aging time at 24,120 and 240 hours respectively. While for 60 ppm Ge, the IMC thickness are much lower with 1.8μm, 3.11μm and 4.154μm at the same aging time with 0ppm Ge. The results indicate that 60 ppm of Ge in Sn-Cu-Ni has the lowest wetting time, higher maximum force and slow IMC growth.
Abstract: The attempt to produce various types of lead-free solder has been actively investigated around the world in order to substitute the harmful SnPb solders. The effects of Zn addition on the microstructure, melting point and microhardness of Sn-0.7Cu lead-free solder were investigated with 1 wt% and 5 wt% of Zn additions. Powder metallurgy (PM) method was used to fabricate these Sn-0.7Cu-Zn lead-free solders. The results revealed that the addition of Zn was able to improve the solder properties. The melting point of Sn-0.7Cu-Zn lead-free solder was decreased drastically as the increasing of Zn additions. The Zn particles were distributed homogenously along the grain boundaries and produced refined dendrite β-Sn, which also lead to a superior microhardness values of solders.
Abstract: In this study, the microstructure of prepared AMCs with the homogenous distribution of fly ash analyzed using optical microscope. The microstructure having refinement of structure with the decreasing of Si-needle structure and increasing the area of eutectic α-Al matrix as shown in Figure 3. Besides, as the increasing amount of fly ash incorporated, there are more petal-like dark structure existed in the microstructure. The density of the AMCs decreased as the incorporation of fly ash increased. While the hardness strength of the AMCs increased with the incorporation of fly ash. The addition of fly ash particles improved the physical and mechanical properties of the AMCs.
Abstract: This paper reported the investigation on gallium, Ga addition into In-4.8Zn lead-free solder to improve its wettability performances. The effect of addition of Ga in In-4.8Zn solder alloy was studied. The results show with the addition of 0.5% Ga into the In-4.8Zn composition, the spreading area of In-4.8Zn-0.5Ga solder on copper increase between 35.71 and 43.75 %. Hence, as the spreading area increases, the contact angle decreased from between 22.09 to 39.71 %. Additionally, the addition of Ga as dopant increased the thickness of IMCs layer.
Abstract: The soldered bonding between the Sn-Zn-Cu-Bi system and a Cu substrate was studied and reported herein. The alloying compositions were varied to investigate the effects of Zn, Cu, Bi contents on the solders’ melting temperature (Tm), microstructures, wettability and the intermetallic-compound (IMC) bonding with a Cu substrate. The Sn-7Zn and Sn-9Zn exhibited low Tm (198 °C), but poor wettability on the Cu substrates. Both Cu and Bi additions significantly improved the solder wettability. However, the Tm of the Sn-Zn-Cu series increased sharply to about 225 °C by the addition of 4-wt% Cu. The addition of 3-wt% Bi lowered Tm of the Sn-Zn-Cu alloys by 5 °C. The thickness of the IMC layers between solder and substrate was maximum for Sn-9Zn and significantly decreased with the Cu addition. With the addition of Bi to Sn-Zn-Cu, the IMC thickness increased. The aging of 150 °C for 150 hours minimally affected the IMC-bonding thicknesses of most samples; however, micro crack could be observed along the aged IMC layers.
Abstract: The effect of high temperature storage of gold ball bonds towards micromechanical properties has been investigated. Gold wire from thermosonic wire bonding exposed to high temperature storage at 150 °C for 10, 100 and 1000 hours. The nanoindentation test was used in order to evaluate the high temperature storage effect on wire bonding in more details and localized. Prior to nanoindentation test, the specimens were cross-sectioned diagonally. The constant load nanoindentation was performed at the center of gold ball bond to investigate the hardness and reduced modulus. The load-depth curve of nanoindentation for the high temperature storage gold wire has apparent the discontinuity during loading compared to as-received gold wire. The hardness value increased after subjected to high temperature storage. However, the hardness decreased when the storage period is extended. The decreasing in the hardness value may due to the grain size of Au metal which recrystallized after subjected to high temperature storage. The results obtained from nanoindentation is important in assessing the high temperature storage of wire bonding.
Abstract: Directional growth behavior of intermetallic compound (IMC) layer of Sn3.0Ag0.5Cu (SAC305) on immersion tin (ImSn) surface finished Cu substrate was investigated. The samples of SAC305 on ImSn/Cu substrate were subjected to thermal cycling at temperatures between 0 °C and 100 °C for 0 cycle up to 500 cycles. The cross-sectioned microstructures of soldered samples, SAC305 on ImSn/Cu were observed using optical microscope. The shape and orientation of IMC growth on the SAC305 on ImSn/Cu indicates that the orientation of IMC growth were observed to be non-uniform and dispersed throughout the solder joint with longer thermal cycling test.
Abstract: This study used nanoindentation technique in order to examine the micromechanical properties of Sn3.0Ag0.5Cu (SAC305) on Electroless Nickel Immersion Gold (ENIG) surface finished Cu substrate subjected to high temperature storage. Lead free solder paste of SAC305 were soldered on ENIG substrate by reflow soldering at 215 °C for 8 second. The soldered samples were exposed to high temperature storage at 180 °C for 0, 200, 400, 600, 800 and 1000 hours. Micromechanical properties show that the solder hardness is decreasing with the HTS time from 239.13 MPa for 0 hour to 178.96 MPa for 1000 hours while the reduce modulus results has increased from 62. 16 x 103 MPa for 0 hour to 82.13 x 103 MPa for 1000 hours. The value of hardness and reduced modulus from nanoindentation approach indicate the occurrence of plastic and elastic deformation throughout the test.