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Research Papers

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

[+] Author and Article Information
Jin Yang, Lizheng Zhang

George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405

I. Charles Ume1

George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405charles.ume@me.gatech.edu

Camil Ghiu

 Jacket Micro Devices, Inc., Atlanta, GA 30308camil.ghiu@jacketmicro.com

George White

 Jacket Micro Devices, Inc., Atlanta, GA 30308

1

Corresponding author.

J. Electron. Packag 132(2), 021006 (Jun 23, 2010) (6 pages) doi:10.1115/1.4001832 History: Received June 01, 2009; Revised April 22, 2010; Published June 23, 2010; Online June 23, 2010

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 the package profile shrinking and operating power increasing, solder joint quality and reliability has become a major concern in microelectronics manufacturing. The 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 through thermal cycling tests. A novel laser ultrasound-interferometric system developed by the authors is applied to inspect solder joint quality during the thermal cycling tests. While the laser ultrasound inspection technique has been successfully applied to flip chips and chip scale packages, this study is the first application of this technique to overmolded 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 the 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 overmolded packages. In particular, the devices constituting the objective of this study are radio frequency modules, which are encapsulated through overmolding and are mounted on a typical four-layer FR4 board through LGA terminations.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Diagram of the laser ultrasound-interferometric inspection system

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Figure 3

Bottom layer schematics of LGA devices: (a) U5 and (b) U6

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Figure 4

Cross section of the LGA package (size not scaled)

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Figure 5

Temperature profile of the thermal cycles

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Figure 6

Inspection patterns of the LGA packages: (a) U5 and (b) U6

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Figure 7

Time-domain response and power spectrum of U5 tested using the LUII system

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Figure 8

Time-domain response and power spectrum of U6 tested using the LUII system

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Figure 9

Modified correlation coefficients after 1000 cycles: (a) U5 and (b) U6

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Figure 10

X-ray results of the samples after 250 thermal cycles: (a) U5 and (b) U6

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Figure 11

X-ray results of the samples after 1000 thermal cycles: (a) U5 and (b) U6

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Figure 12

Time-domain responses of devices U5 and U6 cycled up to 2000 cycles tested using the LUII system

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Figure 13

Power spectrums of the time-domain responses from U5 and U6 cycled up to 2000 cycles

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Figure 14

MCC values after 2000 cycles: (a) U5 and (b) U6

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