Sami T. Nurmi, Janne J. Sundelin, Eero O. Ristolainen and Toivo K. Lepistö
To study the behaviour of voids in PBGA solder joints and their influence on the lifetime of lead‐free solder joints.
Abstract
Purpose
To study the behaviour of voids in PBGA solder joints and their influence on the lifetime of lead‐free solder joints.
Design/methodology/approach
The behaviour of voids was studied using micro via and land pad PWBs, PBGA components, and by measuring voids in the solder joints. The lifetimes of solder joints were tested using accelerated temperature tests.
Findings
Number of factors affecting the solder joint lifetimes were found. The voids were discovered to have a significantly large influence on the solder joints.
Practical implications
The findings can be used to achieve better soldering results, methods, and designs.
Originality/value
In this paper, the effect and the behaviour of voids were studied profoundly. The findings can be valuable to researchers and process personnel.
Details
Keywords
Janne J. Sundelin, Sami T. Nurmi, Toivo K. Lepistö and Eero O. Ristolainen
To provide further knowledge of the effect of solder composition and PCB surface finish on the creep properties of lead‐free SnAgCu solder joints.
Abstract
Purpose
To provide further knowledge of the effect of solder composition and PCB surface finish on the creep properties of lead‐free SnAgCu solder joints.
Design/methodology/approach
Single‐overlap shear specimens were prepared for the creep testing. The test matrix included three different SnAgCu pastes with hypoeutectic, eutectic, and hypereutectic compositions. An Sn63Pb37 solder paste was used as a reference. The PCB finishes used were NiAu, organic solderability preservative (OSP) and immersion tin. The creep tests were performed at 85 and 105°C using a dead‐weight system.
Findings
According to the results, the SnAgCu solder with eutectic or near‐eutectic composition is the safest choice when the creep behaviour of solder joints is considered. Of the three different PCB surface finishes, immersion tin is the most favourable choice for use with SnAgCu joints when creep is the predominant deformation mechanism in the joints. On the NiAu finish the creep properties of SnAgCu solder joints were significantly weaker in eutectic and hypereutectic SnAgCu joints than on Sn and OSP.
Originality/value
The results can be used to enhance the reliability of SnAgCu joints in demanding conditions, when special attention is paid to the choice of PCB surface finish and SnAgCu solder composition.
Details
Keywords
Aulis Tuominen, Eero Ristolainen and Ville Lehtinen
Owing to the incessant demand for reductions in the size of portable electronics, new dense packaging technologies are required. Reflow soldering is still mainly used for…
Abstract
Owing to the incessant demand for reductions in the size of portable electronics, new dense packaging technologies are required. Reflow soldering is still mainly used for component joining on the substrate. In tiny joints such as those in flip chip (FC) assemblies the flux effect is vitally important and needs to pass a narrower performance window than in ordinary surface mount technology (SMT). The determination of the suitability of a flux, as reported in this paper, is twofold; first, the flux must perform well in its intended purpose and second, the flux must not leave harmful residues causing leakage or electromigration. The first test used was the wetting balance test for all fluxes. Fluxes accepted on the basis of the wetting tests were then subjected to the surface insulation resistance test (SIR).