Effects of thermal history on the intermetallic growth and mechanical strength of Pb‐free and Sn‐Pb BGA solder balls

Liang, Jin; Dariavach, N.; Callahan, P.; Shangguan, Dongkai

doi:10.1108/09540910710748113

Cited by 8 publications

(7 citation statements)

References 9 publications

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“…Therefore, many Sn-rich alloy systems have been developed as alternative candidate Pb-free solders, which have attracted much research and trial applications in recent years (Abtew and Selvaduray, 2000;Lau et al, 2016). With a combination of process attributes (modest melting point and reasonable solderability), comparable electrical performances and good mechanical properties, the Sn-Ag-Cu system is one of the potential choices (Zhong et al, 2006;Liang et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Wetting properties of Nd:YAG laser treated copper by SAC solders

Hlinka

Berczeli

Buza

et al. 2017

SSMT

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Purpose This paper aims to discuss the effect of surface treatment on the wettability between copper and a lead-free solder paste. The industrial applications of laser technologies are increasing constantly. A specific laser treatment can modify the surface energy of copper and affect the wetting properties. Design/methodology/approach The surfaces of copper plates were treated using an Nd:YAG laser with varying laser powers. After laser surface treatment, wetting experiments were performed between the copper plates and SAC305 lead-free solder paste. The effect of laser treatment on copper surface was analysed using optical microscopy and scanning electron microscopy (SEM). Findings The experimental results showed that the wetting contact angles changed with the variation in laser power. Furthermore, it means that the surface energy of copper plates was changed by the laser treatment. The results demonstrated that the contact angles also changed when a different soldering paste was used. Originality/value Previous laser surface treatment can be a possible way to optimize the wettability between solders and substrates and to increase the quality of the soldered joints.

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Section: Introductionmentioning

confidence: 99%

Wetting properties of Nd:YAG laser treated copper by SAC solders

Hlinka

Berczeli

Buza

et al. 2017

SSMT

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“…Cumulative IMC growth is a direct and known influence of thermal exposure. In a study of the relationship between the thermal history and the intermetallic microstructure for solder balls of ball-grid-array (BGA) components, Liang et al (2007a) observed continuous intermetallic layer growth and morphology changes during thermal exposure, which holds for all solder alloys (eutectic SnPb, high temperature solder 90Pb10Sn, and lead-free 96.5Sn-3.0Ag-0.5Cu), as shown in Figure 7. Multiple reflows were found to be less Source: Mattila et al (2004) detrimental in terms of IMC growth, than prolonged aging at elevated temperatures.…”

Section: Microstructure and Reliabilitymentioning

confidence: 99%

Solidification and reliability of lead‐free solder interconnection

Shangguan²

2013

Soldering &Amp; Surface Mount Technology

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Purpose -As a literature review article, the purpose of this paper is to highlight the intricate interaction and correlation between the interconnection microstructure and the failure mechanism. It is therefore critical to summarize all the challenges in understanding solder solidification of interconnections. Design/methodology/approach -Literature review. Findings -Solidification of solder interconnections is therefore critical because it is the process during which the solder interconnection is formed. The as-solidified microstructure serves as the starting point for all failure modes. Because of the miniaturization of electronics, the interconnection size decreases continuously, already to such a range that solder solidification takes place remarkably differently from the bulk ingot, on which solidification studies have been focused for decades. There are many challenges in understanding the solidification of tiny solder interconnections, including the complex metallurgical system, dynamic solder composition, supercooling and actual solidification temperature, localized temperature field, diverse interfacial IMC formation, and so on, warranting further research investment on solder solidification. Originality/value -This paper provides a critical overview of the concerns in solidification study for lead-free solder interconnection. It is probably an article initiating more attention towards solidification topics.

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“…from the surface of the component, with a pre‐load force of 2.22 N (0.5 lb) for all tests. Precise positioning of the load probe and maintaining the preload force significantly improve the repeatability of the test results due to the effect of the BGA geometry and probe/load cell non‐linear behaviour at small loads (Liang et al , 2007; Coyle et al , 2000; BGA Ball Shear, 2000).…”

Section: Test Samples and Experimental Proceduresmentioning

confidence: 99%

“…Ball grid array (BGA) removal and replacement are required during product development, and for manufacturing and field returns. In general, a single rework on a specific location is permitted without causing excessive damage to solder joint reliability and board materials and adjacent components (Shin et al , 2001; Ho et al , 1999; Liang et al , 2007). However, BGA multiple revisions during a product development may force many engineering development boards to go through multiple removal and replacement cycles on the same BGA locations.…”

Section: Introductionmentioning

confidence: 99%

Effects of multiple BGA rework on strength of solder joints

Dariavach¹,

Liang²,

Barr³

et al. 2010

Soldering &Amp; Surface Mount Technology

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Purpose -The purpose of this paper is to investigate effects of the multiple rework of ball grid array (BGA) components on mechanical strength of BGA balls, as well as any possible intermetallic (IMC) embrittlement, and obtain data correlated with possible estimation on the maximum permitted limits of BGA rework. Design/methodology/approach -In this paper, mechanical strength of BGA components assemblies with multiple numbers of rework operations was evaluated. Mechanical evaluation was conducted using BGA ball shear tests and four-point bending tests of BGA assemblies. Test samples were prepared under the following conditions: virgin, one, two, three and five BGA reworks. Failure mechanism was evaluated using cross-section and SEM analysis. Findings -The results show that both ball shearing tests and four-point bending tests indicates that strength of BGA solder ball itself was not reduced significantly after repair/rework operation from one to five cycles. The IMC structure layer after rework is a mixture of IMC, Sn-rich and Pb-rich phases. This mixture layers with thickness even more than 10 mm in thickness does not show reduction of strength of BGA solder balls and do not cause premature embrittlement. However, the bonding strength of the copper pads to the laminates is reduced with rework/repair operation, with the great reduction coming from the first and second rework operation. Practical implications -In general, the industry recommends two rework cycles for BGA components on the same spot. This study indicates that further rework (up to five) causes little degradation, therefore there is room to increase the total rework cycle limit beyond recommended two for plastic BGA components. Originality/value -Presented test results shows that in most cases industry overestimates risks associated with increased embritlement of the BGA solder joints due to the intermetallics growth after multiple BGA rework operations. Strength reduction of BGA assemblies is mostly associated with reduction of bonding strength of the copper pads to the laminates is reduced with rework/repair operation and number of reworks could be increased in most cases.

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Effects of thermal history on the intermetallic growth and mechanical strength of Pb‐free and Sn‐Pb BGA solder balls

Cited by 8 publications

References 9 publications

Wetting properties of Nd:YAG laser treated copper by SAC solders

Wetting properties of Nd:YAG laser treated copper by SAC solders

Solidification and reliability of lead‐free solder interconnection

Effects of multiple BGA rework on strength of solder joints

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