Hari Polu, president, OKOS
Manufacturers of high-end electronic products used in consumer, industrial and military applications have long relied on precise testing methods to identify the location of defects such as voids, cracks and the delamination of different layers in a microelectronic device, also known as a chip. Scanning acoustic microscopy (SAM), a non-invasive and non-destructive ultrasonic testing technique, has become a standard method for detecting and analysing flaws during various chip production steps and final quality inspection after packaging. It is also often used for identifying the root cause of a device failing during use.
In addition to semiconductor components, today’s electronic products contain various speciality metal, alloy, plastic, composite 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, dis-bonds, cracks and other irregularities in speciality material components, these constituting the packaging of the semiconductor components.
Now that the same rigor of failure analysis and quality testing used for semiconductor components can be applied to speciality material components, both the production yield and overall reliability of electronic products have improved significantly. This has meant that projects are completed in less time and potential points of failure are eliminated. The reality is that a failure in an electronic product package or a non-semiconductor component can be just as catastrophic as a failure in the semiconductor component.
SAM is a powerful non-invasive and non-destructive method for inspecting internal structures in optically opaque materials. Depth-specific information can be extracted and applied to create two- and three-dimensional images without the need for time-consuming tomographic scan procedures and more costly X-rays.
Advantages of SAM include:
- penetration deep into the material;
- detection of discontinuities in thickness; and
- detection of moisture-related defects.
The OKOS NDT CF-300 multi-axis scanner for research.
SAM works by directing focused, ultra-high frequency sound from a transducer at a tiny point on a target object. The transducer probe is the main part of the ultrasound machine and creates the sound waves and receives the echoes. Transducers differ for specific applications; selection is based on sample thickness, sample materials and number of sample layers. As a result, transducer probes come in many shapes and sizes. The shape of the probe determines its field of view, and the frequency of emitted sound waves determines how deep the sound waves penetrate and the resolution of the image.
Ultrasonic testing (UT) is a family of non-destructive testing techniques based on the propagation of ultrasonic waves in the object or material tested. 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 and its distance are determined. Three-dimensional images are created by scanning point by point and line by line on an object. Scan data is 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 testing methods considered inferior to those used in today's semiconductor industry. However, SAM equipment allows manufacturers of speciality material components to achieve the same level of failure testing as manufacturers of semiconductor components.
OKOS has adapted its SAM systems to accommodate various form factors as well as speciality metal, alloy, plastic, composite, glass and other materials for customers in industrial markets. These systems allow for inspection at one to two orders of magnitude greater for the detection of previously undetectable flaws.
Today, most SAM systems are capable of inspecting unique product geometries and sizes, from crystal ingots, wafers and electronics packages to miniature physical packaging, metal bars/rods/billets, turbine blades, etc. However, as important as the physical and mechanical aspects of conducting a scan are, it should be remembered that the software is key to analysing the information to produce detailed scans.
ODIS (OKOS digital imaging system) WinSAM software supports transducer frequencies ranging from 2.25 to 230 MHz. It delivers advanced analysis through quantitative tools for measurement and classification of parts. Defect detection is possible in multiple zones, namely near-surface, sub-surface and inside of parts.
OKOS SAM systems’ multi-axis scan options enable A, B and C scans, contour following, off-line analysis and virtual rescanning for metals, alloys, plastics, composites and glass, resulting in highly accurate internal and external inspection for defects and thickness measurement via the software.
Every company will eventually move towards this level of failure analysis because of the level of detection and precision required for speciality materials. SAM systems have an integral role in semiconductor component manufacturing based on their precision, usability and time and cost-saving advantages over other non-destructive testing (NDT) options. Extending this testing methodology beyond semiconductor components to speciality material components throughout a semiconductor device can provide more robust failure detection capability for manufacturers of consumer, industrial and military electronic products.
The OKOS NDT XYZ-TT-GS multi-axis immersion scanner for industrial use.
OKOS