Resolution of broadband transducers in acoustic microscopy of encapsulated ICs: transducer selection

Abstract

The lateral resolution of broadband transducers commonly used in acoustic microscopy is discussed in the context of selecting optimum transducers to make images for the best possible resolution of defects in plastic encapsulated integrated circuit (IC) packages. A predictive model to accurately calculate the effective lateral resolution afforded by a transducer is proposed. The model, which explicitly considers the measured frequency dependent attenuation behavior in water and in encapsulant materials, is a practical tool for the acoustic microscopist interested in selecting a transducer with optimum characteristics for inspecting a particular IC package. Experimental data from plastic quad flat packages (PQFP's) molded with two different encapsulants-Nitto MP8000CH and Sumitomo 6300HJ are presented to demonstrate the validity of the modeling approach. Recommendations for optimum transducer selection are presented based on a parametric study of the effect of various transducer and material parameters on the effective lateral resolution and signal loss.

Non-destructive high-resolution characterization of buried interfaces for advanced interconnect and packaging architectures: Experiments and modeling

“…Fig. 5 shows the surface resolution calculated as a function of ultrasound frequency according to the Sparrow criterion [8]. The spherical aberration due to the velocity mismatch between the lens medium (e.g., sapphire) and the coupling medium (e.g., water) is minimal and can be calculated as outlined by Lemons and Quate [9].…”

Effective Transmission of High Frequency Ultrasound into a Silicon Chip through a Polymer Layer

“…Therefore, both layers were especially effective for transmitting the ultrasound emitted with the 100 MHz transducer. The beam intensity at the point focused by the transducer is estimated by the following effective point-spread function (PSF) (16) :…”

Theory and applications of high frequency broadband ultrasound via a thin layer in contact with a solid

“…The lateral resolution, d PE , is defined by the separation between two sound sources and can be determined from the effective point spread function as follows (Bechou, et al, 1997) and (Canumalla, 1999): …”