FEATURE PARTNER FOCUS
CHANGING SPECIFICATIONS, CHANGING INSPECTIONS
Markus Fabich, strategic marketing manager at Olympus Europa SE & Co. KG takes a closer look at microscopy inspection in electronics
The way in which high roughness leads I
nspection of goods along the supply chain has always been an important
element in ensuring quality of the final product. Because although a good product is more than the sum of its parts, quality in every part is still the hallmark of a good product. But is it even possible to define a ‘good part’ or a ‘good material’? Material specifications vary enormously for different applications and, as technology evolves, specifications can also change rapidly over time. Then there’s the issue of checking
specifications using quantifiable data. In some cases, definitions are clear and measurement is easy; in many cases they are not. Take roughness for example. Everyone knows the difference between a rough and a smooth surface, but finding one single parameter that can be used to set a reliable cutoff value for roughness is surprisingly hard – and its importance in electronics manufacturing is increasing.
PCB MANUFACTURING IN THE AGE OF 5G One application where roughness plays an important and changing role is the copper used for the manufacture of printed circuit boards (PCBs). Low- roughness copper has always been beneficial in the production of PCBs, but with the advent of 5G, specifications are becoming tighter. A key reason for these tighter
specifications is that signal transmission strength changes in materials with a high roughness as the frequency of the signal changes. As a result, materials that have acceptable transmission properties at 4G frequencies (<3.5GHz) might struggle when used in 5G applications (e.g. 3.7GHz, 4.5GHz or 28GHz, depending on the country).
8 NOVEMBER 2020 | ELECTRONICS Figure 1.
As the frequency of a signal increases, surface properties become more important in determining transmission strength
to signal loss at high frequencies is called the skin effect (figure 1). At lower frequencies (e.g. 4G), the signal flows through the whole circuit, which means that there is little need for considering surface signal loss. At higher frequencies, however, the signal flows mainly near the surface and will be more affected by roughness.
MEASURING ROUGHNESS The roughness of a surface can be assessed in many different ways, but most detailed methods rely on acquiring a high-resolution 3D map of a specimen first. These maps offer more detailed information than line profile methods and are also easier to interpret. Inspectors can create these maps using multiple technologies, but one that lends itself well to the needs of high- throughput electronics inspections is confocal microcopy. Industrial confocal microscopes are the
Figure 2:
The LEXT OLS5100 can carry out fast roughness measurements with sub- micrometer resolution
most accurate and precise microscopy method for looking at surfaces. These microscopes can measure the shape and roughness of surfaces at the submicron level without affecting the surface in any way. Their high lateral resolution means that they can capture data of a rough surface more accurately than alternative techniques such as white light interferometry.
To combine these benefits with an easy
setup and simple operation, Olympus has developed the LEXT OLS5100 confocal microscope (figure 2). It can measure roughness parameters with a resolution below 5nm, exceeding the standards for ISO 25178 – while also providing smart scanning algorithms for improved throughput and smart tools that make the microscope easy to use. This combination makes the OLS5100 well suited for electronic inspections – not just in PCB manufacturing but also in inspection of, for example, electrodes of batteries or memory cards. For an even more versatile microscopy
solution for electronics inspections, digital microscopes can be used, which show the image of a specimen directly on-screen without the need for oculars. For example, Olympus’ DSX1000 digital microscope enables inspectors to view a specimen under six different observation methods at all magnifications. It also makes inspections faster with objectives that can be exchanged in seconds, while providing a long working distance and high resolution. This digital microscope can also be used for accurate measurements in the micrometer range thanks to its telecentric optical system, which avoids parallax and other distortions from occurring when adjusting the focus.
A CLEAR VIEW Detailed inspection is a key driver of quality in electronics manufacturing – and one that is constantly changing as new technologies, methods and applications emerge. Specialised industrial microscopy systems, such as confocal and digital microscopes, are excellently placed to tackle these challenges – now and in the future – by combining high-precision measurement capabilities with the versatility to support inspectors across the electronics industry.
Olympus Europa SE & Co. KG
www.olympus-europa.com
/ ELECTRONICS
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