Thermal Cycling Fatigue Investigation of Surface Mounted Components with Eutectic Tin-Lead Solder Joints
AffiliationCalifornia Institute of Technology
KeywordsEutectic tin-lead solder
surface mounted component (SMC)
dual in-line (DIP) package
leadless ceramic chip carrier (LCCC)
gull wing leaded quad flatpack (QFP)
J-lead leaded chip carrier
solder joint lead compliance
printed wiring board (PWB)
FR-4 epoxy/fiberglass PWB
printed wiring assembly (PWA)
solder joint failure
solder joint reliability
thermal fatigue failure
gull wing lead configuration
butt mount lead configuration
coefficient of thermal expansion (CTE)
difference in CTE
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AbstractEutectic (63% tin-37% lead) or near-eutectic (40% tin-60% lead) tin-lead solder is widely used for creating electrical interconnections between the printed wiring board (PWB) and the components mounted on the board surface. For components mounted directly on the PWB mounting pads, that is, surface mounted components, the tin-lead solder also constitutes the mechanical interconnection. Eutectic solder has a melting point of 183°C (361°F). It is important to realize that its homologous temperature, defined as the temperature in degrees Kelvin over its melting point temperature (T(m)), also in degrees Kelvin, is defined as T/T(m). At room temperature (25°C = 298K), eutectic solder's homologous temperature is 0.65. It is widely acknowledged that materials having a homologous temperature ≥ 0.5 are readily subject to creep, and the solder joints of printed wiring assemblies are routinely exposed to temperatures above room temperature. Hence, solder joints tend to be subject to both thermal fatigue and creep. This can lead to premature failures during service conditions. The geometry, that is, the lead configuration, of the joints can also affect failure. Various geometries are better suited to withstand failure than others. The purpose of this paper is to explore solder joint failures of dual in-line (DIP) integrated circuit components, leadless ceramic chip carriers (LCCCs), and gull wing and J-lead surface mount components mounted on PWBs.
SponsorsInternational Foundation for Telemetering
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