Pan Pacific Symposium Conference Proceedings

Simultaneous Analysis of Package Warping and Internal Defect Condition Using Acoustic Micro Imaging

Author: Janet E. Semmens
Company: Sonoscan, Inc.
Date Published: 2/11/2014   Conference: Pan Pacific Symposium

Abstract: The trend in microelectronics is toward increasingly thinner devices and assemblies. Acoustic micro imaging has been used in the microelectronics industry to evaluate the quality of devices by imaging the internal structures and defects. Lately, acoustic methods have been developed to investigate other properties such as warping. In thin devices flatness can be a critical factor. Analysis of both data scans can provide important perspective as to whether warping of a package is causing stresses that affect the condition of internal structures such as flip chip bonds and both types of acoustic information can be collected simultaneously saving inspection time.

AMI (Acoustic Micro Imaging) is a non-destructive test method that utilizes high frequency ultrasound in the range of 5 MHz to 500 MHz. Ultrasound is sensitive to variations in the elastic properties of materials and is particularly sensitive to locating air gaps (delaminations, cracks and voids). AMI typically involves producing images at specific depths in a device based on the location of reflected ultrasound echoes from the internal interfaces. The initial echo information is presented in the A-scan which represents a single point depth profile in the part. The shape and amplitude of the echoes at the interface give the condition at the interface. The information contained in the A-scan can also be used for other types of analyses. The distance of the surface echo from the sample relative to the transducer can be used to measure the flatness of the sample surface.

This paper will provide examples showing that measuring the flatness of an assembly and viewing variations in the condition of the subsurface interfaces can provide useful insight as to the quality of the devices.

Key Words: 

Acoustic Micro Imaging (AMI), Defect Detection, Surface Flatness Analysis

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