Development of Sn-9Zn Solder Alloy by Adding Bismuth

Tin-Zinc based on solder is a probable changing of lead element solder as a result of its enhanced mechanical characteristics. This alloy needs to be studied and explored to get a usable solder alloy having better properties. In this work Our objective of the accompanying investigation for alteration the warm, physical and bind qualities of eutectic tin-9Zinc fastening alloy by expansion various ratios of bismuth content to give elective without lead solder alloy to utilize this compound for efferent electronic ventures. We found that the addition of bismuth element content improved the thermal, physical and electrical features and qualities. We got the mentioned results by using x-ray diffractometer, differential scanning calorimetry and LCR instrument to calculate electric resistivity and the contact edge (CA) is the most important factor used for assessing the solid surfaces wettability. Sn91Zn3Bi6 alloy has best solder properties as low melting temperature, pasty range and contact angle. And has the beast soldering properties for electronic application compared to commercial Pb- Sn alloy

Effects of Bismuth Content on the Microstructure, Shear Strength and Thermal Properties of Sn-0.7Cu-0.05Ni Solder Joints

The effects of bismuth content on the microstructure, shear strength and thermal properties of Sn-0.7Cu-0.05Ni solder joints were investigated. Adding 2 wt% elemental Bi to Sn-0.7Cu-0.05Ni solder joints reduced peak temperature by about 6.7 °C, increased pasty range by 4.2 °C and raised undercooling by 3.1 °C. The microstructure of the interfacial layer between solder and Cu substrate was composed of (Cu,Ni)6Sn5 and (Cu,Ni)3Sn intermetallic compounds (IMCs). The solder joint included a phase of SnBi and Cu6Sn5 IMCs. The addition of elemental Bi increased shear strength and suppressed the growth of IMCs in the interfacial layer of the solder joints.

Effects of Antimony and Indium Addition on Wettability and Interfacial Reaction of Sn-3.0Ag-0.5Cu Lead Free Solder on Copper Substrate

The effects of antimony and indium addition on wettability and interfacial reaction of Sn-3.0Ag-0.5Cu lead free solder on copper substrate were investigated. The experimental results showed the melting point of solder alloy containing 0.5 wt.% In and 0.5 wt.% Sb were slightly increased about 3.66°C. The pasty range of solder alloys were increased about 6°C while the undercooling of solder alloys were decreased. The microstructures of solder alloy were contained of In and Sb consists of Ag3Sn, Cu6(Sn,In)5, SnIn, Ag3(Sn,In) and SnSb intermetallic compounds (IMCs) dispersed on Sn-rich phase. The wettability of solder alloys were improved by increasing soldering times. In addition, the thickness of intermetallic compounds (Cu6Sn5) were obviously increased with increasing soldering times.

Voiding and Reliability of Assembly of BGA with SAC and 57Bi42Sn1Ag Alloys

Low melting 57Bi42Sn1Ag (BiSnAg) was explored for replacing SAC solders as a low-cost solution. In this study, BGAs with SAC105, SAC305, and BiSnAg balls were assembled with SAC105, SAC305 or 57Bi42Sn1Ag solder paste. Joint mechanical strength, drop test performance, and voiding performance were evaluated against the reflow profile. SnPb was included as a control. The findings are as follows: (1) The microstructure of solder joints showed that, among all of the combinations, only BiSnAg-105 LT and BiSnAg-305 LT exhibited well-distinguishable alloy regions. For SAC-BiSnAg systems, Sn-dendrites were noticeable at LT, while Ag3Sn needles developed at HT. The joints were homogeneous for the rest of the combinations. (2) In the shear test, combinations involving BiSnAg solder were brittle, regardless of the Bi alloy location and reflow profile, as evidenced by stress-strain curves and morphology of the ruptured surface. The strong influence of Bi on the rupture site may have been caused by the stiffening effect of solder due to the homogenized presence of Bi in the joint. With the stiffened solder, the brittle IMC interface became the weakest link upon shearing, although the brittle BiSn crystalline structure also contributed to the rupture. (3) In the drop test, all Bi-containing solder joints performed poorly compared with Bi-free systems, which was consistent with shear test results. Drop numbers increased with increasing elongation at break of solder bumps as measured in the shear test. (4) Voiding was affected by flux chemistry and reduced by low alloy homogenization temperatures and solid top factors, but was increased by low surface tension factor, melting sequence factor, overheating factor and wide pasty range factor. Compared to SAC or SnPb systems, the BiSnAg system is low in voiding if reflowed at LT. In this study, voiding had an insignificant effect on shear strength and drop test performance.

Superior Drop Test Performance of BGA Assembly Using SAC105Ti Solder Sphere

Board-level drop test performance was evaluated and compared for the following four different solder combinations in BGA/CSP assembly: 1) SnPb paste with SnPb balls, 2) SnPb paste with SAC105Ti balls, 3) SAC305 paste with SAC105Ti balls, and 4) SAC305 paste with SAC105 balls. Presence of Ti improved the drop test performance significantly, despite the voiding side effect caused by its oxidation tendency. It is anticipated that the voiding can be prevented with the development of a more oxidation resistant flux. The consistently poor drop test performance of 105Ti/SnPb is caused by the wide pasty range resulted from mixing SAC105 with Sn63 solder paste. The effect of Ti in this system is overshadowed by the high voiding outcome due to this wide pasty range material. In view of this, use of SAC105 BGA with SnPb solder paste is not recommended, with or without Ti addition. High reflow temperature drove fracture shift to interface at package side, presumably through building up IMC thickness beyond the threshold value. A lower reflow temperature is recommended. Electrical response is consistent with complete fracture data. But, complete fracture trend is inconsistent with that of partial fracture trend, and neither data can provide a full understanding about the failure mode. By integrating complete fracture and partial fracture into “Virtual Fracture”, the failure mechanism becomes obvious and data sets become consistent with each other.