• Journal of Welding and Joining
• /
• v.18 no.6
• /
• pp.42-47
• /
• 2000

The object of this study is to estimate Sn-Ag-Bi-Ga solder alloy as a substitute for Sn-37Pb alloy. For Sn-Ag-Bi-Ga alloys, Ag, Bi and Ga contents are varied. (Ag : 1~5%, Ga : 3%, Bi : 3~6%) Comparing to Sn-37Pb alloy Sn-Ag-Bi-Ga alloys have wider melting temperature range up to max. $18.7^{\circ}C$. With increasing Ag, Bi contents, the wettability of the alloys increased up to max. 6.6 mN. The vickers hardness of the alloys was max. 46.4 Hv. The ultimate tensile stress of the alloys was max. 60.3 MPa and the elongation was max. 1.2%. The joint strength between circuit board and solder was max. 55.5 N and the joint strength between connector and solder was max. 176.1 N. There were no cracks in this alloys after thermal shock test.

• Korean Journal of Materials Research
• /
• v.15 no.9
• /
• pp.598-603
• /
• 2005

To develope new lead-free solders with the melting temperature close to that of Sn-37Pb$(183^{\circ}C)$, Sn-0.7Cu-5Pb-1Ga, Sn-0.7Cu-5Pb-1Ag, Sn-0.7Cu-5Pb-5Bi-1Ag, and Sn-0.7Cu-SBi-1Ag alloys were composed by adding low-netting elements such as Ga, Bi, Pb, and Ag to Sn-0.7Cu. Then the melting temperatures, microstructures, wettability, and adhesion properties of these alloys were evaluated. DSC analysis showed that the melting temperature of Sn-0.7Cu-SPb-1Ga was $211^{\circ}C$, and those of other alloys was in the range of $192\~200^{\circ}C$. Microstructures of these alloys after heat-treatment at $150^{\circ}C$ for 24 hrs were basically composed of coarsely- grown $\beta-Sn$ grains, and $Cu_6Sn_5$ and $Ag_3Sn$ intermetallic precipitates. Sn-0.7Cu-5Pb-1Ga and Sn-0.7Cu-5Pb-5Bi-1Ag showed excellent wettability, while Sn-0.7Cu-5Bi-1Ag and Sn-0.7Cu-5Pb-5Bi-1Ag revealed good adhesion strength with the Cu substrates. Among 4 alloys, Sn-0.7Cu-5Pb-5Bi-1Ag with the lowest melting temperature $(192^{\circ}C)$ and relatively excellent wettability and adhesion strength was suggested to be the best candidate solder to replace Sn-37Pb.

• Journal of Welding and Joining
• /
• v.16 no.3
• /
• pp.148-156
• /
• 1998

The purpose of this study is to investigate the characteristics of Pb-Free Sn-2%Ag-Bi solder alloys. The solder alloys used in this study is Sn-2%Ag-(3,5,7,9%) Bi It is examined that their properties such as melting range, wettability, microstructure, microhardness, and tensile property. The addition of Bi(3,5,7,9%) lowered the melting point of the solder and the melting range was 196~203$^{\circ}C$. The wettability of the solder as equal to that of Sn-37% Pb solder. The morphology of structure did not change largely by addition of Bi. But the structure of cellular dendrite of linear type displayed. The tensile strength of the solder was superior to that of Sn-37%Pb solder. But the elongation was inferior to that of Sn-37%Pb solder. The hardness of Sn-2%Ag solder was tow times and that of Sn-2%Ag-Bi solder was three times of that in Sn-37%Pb solder. But the effect of increment of Bi content did not change largely.

• Korean Journal of Metals and Materials
• /
• v.49 no.3
• /
• pp.211-220
• /
• 2011

To improve the low ductility and high strain-rate sensitivity in Sn-Bi based solder alloys, the influences of the minor additions of alloying elements (Ag, Mn, In) were investigated. The strain-stress curves of various Sn-40Bi(-X) alloys, including a pre-suggested Sn-40Bi-0.1Cu composition were measured using a tensile testing machine. As a result, the elongation and ultimate tensile strength (UTS) values were compared. The small addition (0.5 wt.%) of Ag significantly enhanced the ductility and high strain-rate sensitivity of the alloys at strain rates of $10^{-4}$ to $10^{-2}\;s^{-1}$ mainly due to the increase and refinement of eutectic lamellar structures. The microstructure change increased the area of grain boundaries, thus ameliorating the grain boundary sliding mode. It was also found that Mn is an effective element in enhancing the ductility, especially at the strain rates of $10^{-3}$ to $10^{-2}\;s^{-1}$ The enhancement is likely attributed to the fine and homogeneous microstructure in the alloys containing Mn.

• Journal of the Microelectronics and Packaging Society
• /
• v.8 no.4
• /
• pp.25-33
• /
• 2001

Sn-3.5Ag-xBi alloys with five different levels of Bi (0, 2.5, 4.8, 7.5, 10 wt%) were prepared for evaluating creep properties. Cast alloys were roiled and heat treated to provide stable microstructures during the subsequent creep tests, which were conducted under constant load using dog-bone specimens. For the Bi containing alloys, creep strength showed the maximum around 2.5 wt%Bi and tended to decrease with increasing Bi content. The stress exponent of the alloy was around 4, suggesting typical dislocation creep, but the exponent was 2 for the 10 wt%Bi alloy, suggesting creep assisted by grain boundary Sliding. For the Bi containing alloys, the brittle fracture mode appeared showing small amount of reduction of area, while the ductile fracture mode was true for the Bi free alloy. Microstructural examination of ruptured specimens showed cavitations on grain boundaries normal to the load axis, and a significant of grain boundary sliding for the Bi containing alloys.

• Journal of the Microelectronics and Packaging Society
• /
• v.12 no.1 s.34
• /
• pp.47-52
• /
• 2005

Worldwide movement for prohibition of Pb usage drives imminent implementation of Pb-free solders in microelectronic packaging industry. Reliability information of Pb-free solders has not been completely constructed yet. One of the potential reliability concerns of Pb-free solders is allotropic transformation of Sn known as tin pest. Volume increase during the formation of tin pest could deteriorate the reliability of solder joints. It was also reported that the addition of soluble elements (i.e. Pb, Bi, and Sb) into Sn can effectively suppress the tin pest. However, the mechanical properties of the tin pest resistant alloys have not been studied in detail. In this study, lap shear creep test was conducted with Sn and Sn-0.7Cu based solder alloys doped with minor amount of Bi or Sb. Shear strain rates of the alloy were generally higher than those of Sn-3.5Ag based alloys. Rupture strains and corresponding Monkman- Grant products were largest for Sn-0.5Bi alloy and smallest for Sn-0.7Cu-0.5Sb alloy. Rupture surface Sn-0.5Bi alloy showed highly elongated $\beta$-Sn globules necked to rupture by shear stresses, while elongation of $\beta$-Sn globules of Sn-0.7Cu-0.5Sb alloy was relatively smaller.

• Journal of Welding and Joining
• /
• v.16 no.3
• /
• pp.157-166
• /
• 1998

Recently as environmental pollution caused by Pb has posed a serious threat to the global environment, the trend to regulate the usage of Pb in electronic industry is one the rise. Currently, the solder alloy with high Pb content, Sn-37%Pb, is utilized in the electronic assembly therefore, the objective of this study is to develop an alternative solder alloy for the existing Sn-37%Pb solder alloy. First thing, this work choosed Sn-5%Pb-1.5%Ag, Sn-5%Pb-1.5%Ag-x%Bi(x=1~5%) for candidate solder alloys, and examined their properties such as melting range, wettability, microhardness, tensile property, oxidation behavior and microstructure. Wettability was on the same level of Sn-37%Pb. Dissolution of Pb ion in Sn-5%Pb solder was 0.46ppm. This solder alloy revealed cellular dendrite microstructure $\beta$-Sn matrix, Pb-rich phase, Ag/Sn, and Cu/Sn Intermetallic compounds. The range of solidification temperature was within 3$0^{\circ}C$. Also these alloy displayed higher tensile strength and lower elongation than Sn-37%Pb. The resistance of oxidation in Sn-5%Pb-1.5%Ag solder alloy was superior to that of Sn-37%Pb solder alloy. But that of Sn-5%Pb-1.5%Ag-5%Bi solder alloy was equal to that of Sn-37%Pb solder alloy.

• Proceedings of the KWS Conference
• /
• 1999.10a
• /
• pp.251-254
• /
• 1999

• Proceedings of the KWS Conference
• /
• 1999.05a
• /
• pp.61-62
• /
• 1999

• Journal of the Microelectronics and Packaging Society
• /
• v.26 no.4
• /
• pp.163-169
• /
• 2019

Sn-Pb solder alloys in electronics rapidly has been replaced to Pb free solder alloys because of various environmental regulations such as restriction of hazardous substances directive (RoHS), European Union waste electrical, waste electrical and electronic equipment (WEEE), registration evaluation authorization and of chemicals (REACH) etc. Because Sn58%Bi (in wt.%) solder alloy has low melting point and higher mechanical properties than that of Sn-Pb solder, it has been studied to manufacture electronic components. However, the reliability of Sn58%Bi solder could be lowered because of the brittleness of Bi element included in the solder alloy. Therefore, we observed the microstructures of Sn58%Bi composite solders with various contents of Sn-decorated multiwalled carbon nanotube (Sn-MWCNT) particles and evaluated bonding strength of the FR-4 components assembled with Sn58%Bi composite solder. Also, microstructures and bonding strengths of the Sn58%Bi composite solder joints were evaluated with the number of reflows from 1 to 7 times, respectively. Bonding strengths and fracture energies of the Sn58%Bi composite solder joints were measured by die shear test. Microstructures and fracture modes were observed with scanning electron microscope (SEM). Microstructures in the Sn58%Bi composite solder joints were finer than that of only Sn58%Bi solder joint. Bonding strength and fracture energy of Sn58%Bi composite solder including 0.1 wt.% of Sn-decorated MWCNT particles increased up to 20.4% and 15.4% at 5 times in reflow, respectively.