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Hari Polu

Metrology

Beyond Microchips: The Growing Value of Scanning Acoustic Microscopy

Ensure the reliability of electronic devices by testing specialty metals and materials

Published: Thursday, July 29, 2021 - 12:03

Manufacturers of high-end semiconductor electronic products used in consumer, industrial, and military applications have long relied on precise testing methodologies to identify the location of defects such as voids, cracks, and the delamination of different layers within a microelectronic device, also known as a microchip. Manufacturers also employ scanning acoustic microscopy (SAM), a noninvasive and nondestructive ultrasonic testing method, which became an industry standard to detect and analyze flaws during various chip-production steps and in the final quality inspection after packaging.

In addition, SAM is often used as a failure analysis method to identify a specific root-cause failure mechanism when a device fails during use.

scanning acoustic microscopy

Beyond semiconductor components themselves, today’s electronics products contain various specialty metals, alloys, plastics, and glass components. All semiconductor components need to be enclosed and packaged in consumer-usable form factors. As a result, SAM equipment has evolved and is now being used to detect subsurface flaws, disbonds, cracks, and other irregularities in materials that constitute “packaging” of semiconductor components.

With the same rigor of failure analysis and quality testing used for semiconductors now being applied to metals and alloys, both the production yield and overall reliability of electronic devices have improved significantly. In doing so, projects are completed in less time while eliminating potential points of failure in the field. This is important because a failure in an electronic product package or a nonsemiconductor component can be just as catastrophic as a failure with the semiconductor itself.

Detecting flaws with SAM

SAM is a powerful noninvasive and nondestructive method for inspecting internal structures in optically opaque materials. Depth-specific information can be extracted and applied to create 2D and 3D images without the need for time-consuming tomographic scan procedures and more costly X-rays.

SAM works by directing focused, ultrahigh frequency sound from a transducer at a tiny point on a target object. The sound as it passes through the material is either scattered, absorbed, reflected, or transmitted. By detecting the direction of scattered pulses and measuring the “time of flight” (TOF), the presence of a boundary or object, as well as its distance, can be determined. Three-dimensional images are created by scanning an object point by point and line by line. Scan data are digitally captured and processed by special imaging software and filters to resolve a specific area of focus in either single or multiple layers.

The industrial sector has traditionally used other methods to inspect internal structures, although they are considered inferior to the methods used in the semiconductor industry. However, with SAM equipment, specialty-materials manufacturers can achieve the same level of failure testing as the companies that make metals, alloys, composites, and titanium plates used in electronic devices.

scanning acoustic microscopy

To accomplish this, companies like OKOS leverage the best practices and tight specifications from the semiconductor world and adapt SAM scanning systems to provide unique solutions for specialty crystalline, metals, and other material for use within industrial markets. With this type of testing, operators can inspect materials at a level one to two orders of magnitude better to discover flaws that were previously undetected.

Today, much of the SAM equipment can inspect various items with unique product geometries or sizes, from crystal ingots, wafers, and electronics packages to miniature physical packaging, metal bar/rods/billets, and turbine blades. However, as important as the physical and mechanical aspects of conducting a scan are, the software is the key to analyzing the information to produce detailed scans. For this reason, OKOS decided early on to deliver a software-driven, ecosystem-based solution. The ODIS Acoustic Microscopy software supports a wide range of transducer frequencies from 2.25 to 230 MHz.

Multi-axis scan options enable A, B, and C-scans, contour following, offline analysis, and virtual rescanning for composites, metals, and alloys. This allows highly accurate internal and external inspection for defects and thickness measurement via the inspection software.

scanning acoustic microscopy

The software-driven model drives down the costs of SAM testing while delivering the same quality of inspection results. As a result, this type of equipment is well within reach of even modest testing labs, R&D centers, and material research groups.

SAM systems play an integral role in semiconductor device manufacturing based on their precision, usability, and time-saving advantages compared to other NDT options. Extending this testing methodology beyond semiconductor components to specialty metals and materials can provide more robust failure-detection capability for manufacturers of consumer, industrial, and military electronic devices.

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About The Author

Hari Polu’s picture

Hari Polu

Hari Polu is the President of OKOS, a Virginia-based manufacturer of scanning acoustic microscopy (SAM) and industrial ultrasonic non-destructive (NDT) systems. OKOS serves the electronics manufacturing, aerospace, and metal/alloy/composite manufacturers, and end-user markets