Land grid array sockets for server applications

Corbin, J. S.; Ramirez, C. N.; Massey, D. E.

doi:10.1147/rd.466.0763

Cited by 24 publications

(21 citation statements)

References 5 publications

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“…This method integrates the squared error between the signals, and then normalizes this integrated value by the total energy of the reference signal. The equation is shown as, (1) where f(t) is the measured signal, and r(t) is the reference signal. The scale of the ER depends on the devices being tested and should only be used for the relative comparison between similar product types.…”

Section: Correlation Coefficient Methodsmentioning

confidence: 99%

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Board-Level Solder Joint Reliability Study of Land Grid Array Packages for RF Applications Using a Laser Ultrasound Inspection System

Yang

Zhang

Ume

et al. 2007

2007 Proceedings 57th Electronic Components and Technology Conference

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Microelectronics packaging technology has evolved from through-hole, and bulk configuration to surface-mount, and small-profile ones. Today's electronics industry is also transiting from SnPb to Pb-free to meet environmental requirements. Land grid array (LGA) package has been becoming popular in portable electronics in terms of low profile on the printed wiring boards and direct Pb-free assembly process compatibility. With package profile shrinking and operating power dramatically increasing, solder joint quality and reliability has become a major concern. Solder joint failure at the package level or board level will cause electronic devices not to function during service. In this paper, board-level solder joint reliability of the LGA packages under thermal loading is studied with thermal cycling tests. A novel laser ultrasound-interferometric system developed by the authors at Georgia Tech is applied to inspect solder joint quality during the thermal cycling tests. While the laser ultrasound inspection technique has been applied successfully to flip chips and chip scale packages, this study is the first application of this technique to over-molded packages. In this study, it is found out that the LGA packages can withstand 1000 temperature cycles without showing crack initiation or other failure mechanisms in solder joints. The laser ultrasound inspection results match the visual observation and X-ray inspection results. This study demonstrates the feasibility of this system to solder joint quality inspection of over-molded packages. In particular, the devices constituting the object of this study are radio frequency (RF) modules, which are encapsulated through over-molding and are mounted on a typical four-layer FR4 board through LGA terminations.

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Section: Correlation Coefficient Methodsmentioning

confidence: 99%

“…Since LGA has lower standoff height and different material properties compared with the conventional ball grid array (BGA) package, LGA package gains attention on its reliability characteristics [1][2][3]. A major concern is board-level solder joint reliability of the LGA packages under thermal loading.…”

Section: Introductionmentioning

confidence: 99%

Board-Level Solder Joint Reliability Study of Land Grid Array Packages for RF Applications Using a Laser Ultrasound Inspection System

Yang

Zhang

Ume

et al. 2007

2007 Proceedings 57th Electronic Components and Technology Conference

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“…A land grid array (LGA) socket is used in conjunction with an LGA component, which can accommodate high I/O counts and is therefore popular for microprocessor applications. Use of LGA sockets allows the microprocessor component to be easily upgraded or repaired and eliminates the reliability risks to the package associated with soldering [1,2].…”

Section: Introductionmentioning

confidence: 99%

“…LGA sockets are available in conductive elastomer, wire wound and stamped metal designs [1,2]. In the elastomer design each contact button is made of an elastomer filled with conductive particles that make contact on compression.…”

Section: Introductionmentioning

confidence: 99%

Stress relaxation in a commercial stamped metal land grid array socket

Challa

Osterman

Pecht

et al. 2008

2008 58th Electronic Components and Technology Conference

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Land grid array (LGA) sockets provide a solderless printed circuit board (PCB) attachment method for microprocessors that require high interconnect density. Stamped metal LGA sockets consist of metal contacts embedded in a plastic housing, that form the electrical and mechanical connection between the component and PCB by means of compression.To achieve a stable contact interface between the socket and component/PCB, it is necessary to maintain a minimum normal force. Stress relaxation results in a loss of normal force, and could cause an increase in contact resistance, potentially leading to a failure. Contact alloy manufacturers report stress relaxation data for the alloy in strip form. This data may not be an appropriate measure of the stress relaxation in an LGA socket because it does not take into account the geometry of the increasingly miniaturized contacts or the effect of the surrounding polymer. This paper therefore aims to study the stress relaxation of stamped metal LGA sockets, by testing the actual socket in its final processed form and capturing the effect of the polymer on stress relaxation. Furthermore, by testing small pieces of the socket, independent of the loading assembly, a method of studying the temperature and load dependence of stress relaxation and the effect on the socket's electrical behavior was demonstrated, without the need for system level testing.

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“…In the long-term such a structure can potentially be implemented by using low profile land grid array (LGA) style interconnections. Insertion force and mechanical stress is a problem in high pin count interconnections and this can be addressed by using inductively coupled elements for high speed signal connections while using fuzz buttons for power, ground connections and to provide a rigid mechanical interface [5].…”

Section: Introductionmentioning

confidence: 99%