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Article
Publication date: 27 June 2008

Meng‐Kuang Huang and Chiapyng Lee

The purpose of this paper is to describe the board level reliability test results of four IC packages with lead‐free balls/platings, soldered with lead‐free solder paste…

Abstract

Purpose

The purpose of this paper is to describe the board level reliability test results of four IC packages with lead‐free balls/platings, soldered with lead‐free solder paste, during thermal cycling. The board level reliability test results of tin‐lead balled/plated packages soldered with lead‐free solder paste have also been included for comparison.

Design/methodology/approach

Four different packages, i.e. ball grid array (BGA), chip scale package (CSP), quad flat package (QFP) and thin small outline package (TSOP), were assembled on a test printed circuit board (PCB) as the test vehicle. Lead‐free and tin‐lead BGA/CSP packages were equipped with Sn‐3.0Ag‐0.5Cu and Sn‐37Pb solder balls, respectively. The lead‐frames of lead‐free QFP/TSOP leaded‐packages were plated with Sn‐58Bi and those of tin‐lead QFP/TSOP leaded‐packages, Sn‐37Pb. The lead‐free solder paste used in this study was Sn‐3.0Ag‐0.5Cu. Two kinds of surface finishes, immersion gold over electroless nickel (Au/Ni) and organic solderability preservative, were used on the PCBs. The test PCBs were thermal cycled 5,000 times within the temperature range of −40 to 125°C and electrically monitored during the thermal cycling.

Findings

It was found that the tin‐lead balled/plated BGAs, CSPs, QFPs and TSOPs soldered with lead‐free solder paste showed serious board level reliability risks as their abilities to withstand thermal cycling stresses are much weaker than those of entirely lead‐free assemblies. Neither package nor surface finish was found to have any effects on the board level reliability of test vehicles with lead‐free balled/plated BGAs, CSPs, QFPs and TSOPs. Metallographic examinations were conducted to investigate the effect of thermal cycling on the failure modes of solder joints.

Originality/value

The paper is of value by contributing to research in the use of lead‐free solder paste with lead‐containing packages in the industry. Currently, there is a deficiency of knowledge in this area.

Details

Soldering & Surface Mount Technology, vol. 20 no. 3
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 1 September 2005

Meng‐Kuang Huang, Chiapyng Lee, Pei‐Lin Wu and Shyh‐Rong Tzan

The effects of thermal fatigue and printed circuit board (PCB) surface finish on the pull strength, failure modes and reliability of chip scale package (CSP) solder joints…

Abstract

Purpose

The effects of thermal fatigue and printed circuit board (PCB) surface finish on the pull strength, failure modes and reliability of chip scale package (CSP) solder joints were investigated.

Design/methodology/approach

Mechanical pull test, metallographic examination and electrical measurement were used. Tin lead (Sn‐Pb) and lead free (Sn‐Ag‐Cu) alloys were used with Au/Ni and organic solderability preservative (OSP) surface finishes.

Findings

The experimental results showed that the pull strength of the Sn‐Ag‐Cu/(Au/Ni) solder joint did not change noticeably with an increasing number of thermal cycles. However, the pull strength of the Sn‐Pb/(Au/Ni) solder joints drastically degraded and that of the Sn‐Ag‐Cu/OSP and Sn‐Pb/OSP solder joints slightly decreased during thermal cycling. For both Sn‐Ag‐Cu and Sn‐Pb alloys, the solder joint fracture of as‐soldered samples was the main failure mode when an Au/Ni surface finish was used. For the Sn‐Ag‐Cu/(Au/Ni) and Sn‐Ag‐Cu/OSP solder joints, the proportion of component trace tearing considerably decreased, whereas that of PCB trace tearing considerably increased, during thermal cycling. The Weibull lifetimes of the solder joints were increasingly longer in the order of Sn‐Pb/(Au/Ni), Sn‐Pb/OSP, Sn‐Ag‐Cu/OSP, and Sn‐Ag‐Cu/(Au/Ni).

Research limitations/implications

This was not an exhaustive study and all of the findings are for lead free and tin lead CSP solder joints, which perhaps limits the usefulness of the results elsewhere.

Practical implications

A very useful source of information and impartial advice for engineers planning to conduct a switch from tin lead to lead free technology in their production lines.

Originality/value

This paper fulfils an identified information/resources need and offers practical help to an engineer starting out on an engineering development.

Details

Soldering & Surface Mount Technology, vol. 17 no. 3
Type: Research Article
ISSN: 0954-0911

Keywords

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