The Effects of Entrapped Bubbles in Solder Used for the Attachment of Leadless Ceramic Chip Carriers

DerMarderosian, Aaron; Gionet, Vincent

doi:10.1109/irps.1983.361989

Cited by 9 publications

(2 citation statements)

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“…Voiding in solder joints is a major reliability threat, mainly due to its role as a stress concentrator, hence it either initiates crack formation or facilitates the crack propagation, and eventually results in joint failure (Novick, 1973; der Marderosian and Gionet, 1983; Tvergaard, 1989; Mahalingham et al , 1984). The problem intensifies with the introduction of microvias and lead‐free soldering.…”

Section: Introductionmentioning

confidence: 99%

Effect of SnAgCu composition on soldering performance

Huang

Dasgupta

Lee

2005

Soldering &Amp; Surface Mount Technology

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PurposeTombstoning and voiding have been plaguing the surface mount assembly industry for decades. The recent global move toward lead‐free soldering and the extensive adoption of microvia technology further aggravate the problems. The present study investigates the impact of SnAgCu (SAC) alloy composition on these important issues.Design/methodology/approachIn this study, tombstoning and voiding at microvias are studied for a series of SAC lead‐free solders, with an attempt to identify a possible “composition window” for controlling these problems. Properties which may be related to these problems, such as alloy surface tension, alloy melting pattern, and solder wetting behaviour, were investigated in order to assess the critical characteristics required to control these problems.FindingsThe results indicate that the tombstoning of SAC alloys is greatly influenced by the solder composition. Both the wetting force and the wetting time at a temperature well above the melting point have no correlation with the tombstoning frequencies. Because the tombstoning is caused by imbalanced wetting forces, the results suggest that the tombstoning may be controlled by the wetting at the onset of the paste melting stage. A maximum tombstoning incidence was observed for the 95.5Sn3.5Ag1Cu alloy. The tombstoning rate decreased with increasing deviation in Ag content from this composition. A differential scanning calorimetry (DSC) study indicated that this was mainly due to the increasing presence of the pasty phase in the solders, which result in a slower wetting speed at the onset of solder paste melting stage. Surface tension plays a minor role, with lower surface tension correlating with a higher tombstoning rate. The voiding rate at the microvias was studied by employing simulated microvias. The voiding level was lowest for the 95.5Sn3.8Ag0.7Cu and 95.5Sn3.5Ag1Cu alloys, and increases with a further decrease in the Ag content. The results indicate that voiding at microvias is governed by the via filling and the exclusion of fluxes. The voiding rate decreased with decreasing surface tension and increasing wetting force, which in turn is dictated by the solder wetting or spreading. Both low surface tension and high solder wetting prevents the flux from being entrapped within a microvia. A fast wetting speed may also facilitate reducing voiding. However, this factor is considered not as important as the final solder coverage area.Research limitations/implicationsIn general, compositions which deviate from the ternary eutectic SAC in Ag content, particularly with a Ag content lower than 3.5Ag, exhibit a greater solid fraction at the onset of melting, resulting in a lower tombstoning rate, presumably due to a slower wetting speed. The SAC compositions with an Ag content lower than 3.5 per cent, such as 2.5Ag, resulted in a lower tombstoning rate with minimal risk of forming Ag3Sn intermetallic platelets. On the other hand, ternary eutectic SAC exhibits a lower surface tension resulting in an easier solder spread or solder wetting...

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Section: Introductionmentioning

confidence: 99%

Effect of SnAgCu composition on soldering performance

Huang

Dasgupta

Lee

2005

Soldering &Amp; Surface Mount Technology

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“…Presence of voids have been reported to affect the mechanical properties of joints [5] and deteriorate the strength, ductility, creep, and fatigue life [6,7], due to the growth in voids, which could coalesce to form ductile cracks and consequently lead to failure. In this study, the effect of voiding on elongation at break (see Fig.…”

Section: Drop Testmentioning

confidence: 99%

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

Liu

Keck

Page

et al. 2013

International Symposium on Microelectronics

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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.

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Package-to-Board Interconnections

Reiley¹,

Shih²

1989

Microelectronics Packaging Handbook

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The Effects of Entrapped Bubbles in Solder Used for the Attachment of Leadless Ceramic Chip Carriers

Cited by 9 publications

References 0 publications

Effect of SnAgCu composition on soldering performance

Effect of SnAgCu composition on soldering performance

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

Package-to-Board Interconnections

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