Fatigue-Strength Evaluation of Sn-Ag-Cu Solder Joints in BGA-Type Packages

Electronics devices consist of silicon chips, copper leads, substrates and other parts which are jointed to each other with solder, conductive adhesive or other materials. Each coefficient of thermal expansion is different and it causes strain concentrations and cracks. We analytically investigated the stress reduction structure at the edge of the joints such as Sn-Ag-Cu solder or Cu/Sn alloy between the silicon chip and copper lead. At first, we examined the influence of the joint thickness and fillet at the joint edge on the stress. In the joint without fillet, the stress at the end of the joint increased depending on the thickness of the joint. The fillet of the joint increased the stress of the Cu/Sn alloy joint and the stress was increased depending on the thickness, though the fillet decreased the stress of the solder joint. We suggested the copper lead with slits to reduce the force of constraint. We compared the effects of the structure parameters of the slits on the stress reduction. The height was a more effective parameter than the width and the pitch. In the case of solder joint, the slits of the copper lead reduce the stress more effective in the thick joint than the thin joint. However, in the case of Cu3Sn joints, the slits reduced the stress more effectively in the thin joint than thick joint.

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“…The 4 m thick (a) Cu (b) Sn-Ag-Cu solder Fig. 4 Stress-strain curves used in the structure analysis [10,11].…”

Section: Analysis Resultsmentioning

confidence: 99%

Effects of Material Property and Structural Design on the Stress Reduction of the Joints in Electronics Devices

Matsushima

Nakashima

Fujimoto

et al. 2014

MSF

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“…From the viewpoint of environmental protection, in recent years, Sn-37Pb solder has been replaced by Pb-free solder. Comparative studies of mechanical fatigue life and thermal cycle fatigue life for both Sn-37Pb solder and Pb-free solder have been done (1) - (10) . Crack propagation was observed at an intermetallic compound layer between the interface of solder and its pad for the Sn-Ag-Cu and Sn-Ag-Bi systems (1), (2) .…”

Section: Introductionmentioning

confidence: 99%

“…Test results gave the location of crack occurrence and then relationships between fatigue life and solder materials were examined. Fatigue of BGA joints was estimated from plain specimen fatigue data (10) . However, because sizes of BGA joints are much smaller than plain specimen sizes and there is a large stress gradient, a reference strain for BGA solder joints was evaluated by using mean strain at a certain depth (0.02 mm (3) , 0.05 mm (5) ).…”

Section: Introductionmentioning

confidence: 99%

Fatigue Strength of BGA Type Solder Joints between Package and Printed Wiring Board of Portable Device

Nagano

Yaguchi

Terasaki

2006

JSME Int. J., Ser. A

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Solder joints between a package and a printed wiring board (PWB) of a portable electronic device sustain heat cycling as a result of power on-off operations, cyclic bending by key pad operation, and impact bending by dropping. Therefore, heat cycling, cyclic bending, and cyclic impact bending tests were conducted on the ball grid array solder joints between a chip scale package and a PWB. The evaluated solders were Sn-3Ag-0.5Cu and Sn-37Pb. The tests showed that the life cycles of the Sn-3Ag-0.5Cu solder joints for the heat cycling and cyclic bending tests were approximately twice those of the Sn-37Pb solder joints. For the cyclic impact bending test, however, the life cycle of the Sn-3Ag-0.5Cu joint under large strain was smaller than that of the Sn-37Pb solder joint because of interfacial crack growth between the solder and the PWB. Finally, fatigue lives of the joints were compared with crack initiation and failure lives of plain specimens by calculating local strain ranges in the joints by elastic-plastic finite element analysis.

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Evaluation of Fatigue Strength for Solder Joints on NSMD Pads in Electronic Packages

Naka

Yaguchi

Tanie

et al. 2012

JMMP

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We developed a method for evaluating the life of solder joints for an electronic package with non-solder-mask-defined (NSMD) solder pads. Generally, the thermal-cycling life of a package with NSMD pads is longer than that of a package with solder-mask-defined (SMD) pads, which are usually used in packages. However, the fracture mechanism of joints on NSMD pads has not been sufficiently investigated. Therefore, we conducted mechanical fatigue tests on the joints of NSMD pads. We found that the crack propagation behavior in NSMD joints is different from that in SMD, and that this difference in behavior causes the life span of NSMD joints to be longer than that of SMD. In addition, we found that the relationship between the strain and life in NSMD joints is different from that in SMD, but the life of a package with NSMD pads can be predicted by relating the strain in the solder bumps, analyzed using a finite element method, to life span data from mechanical tests.

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Fatigue-Strength Evaluation of Sn-Ag-Cu Solder Joints in BGA-Type Packages

Cited by 3 publications

References 0 publications

Effects of Material Property and Structural Design on the Stress Reduction of the Joints in Electronics Devices

Effects of Material Property and Structural Design on the Stress Reduction of the Joints in Electronics Devices

Fatigue Strength of BGA Type Solder Joints between Package and Printed Wiring Board of Portable Device

Evaluation of Fatigue Strength for Solder Joints on NSMD Pads in Electronic Packages

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