Often, customers are interested how the actual cross sectioning is performed and how cross section samples preparations should be done. This short text is to give some perspective for product developers and designers and to open up somewhat an unknown concept that the cross sectioning is for many.
No wonder that the failure analysis is found interesting by many since there are plenty of great benefits to it. Strictly speaking it can reduce costs considerably. One of the main key figures to focus on for RnD is the field failure rate. Uncontrollable amount of customer returns can be detrimental for company’s brand image, since nothing is more expensive than failure found by a customer. Hence, continuous inspection and analysis of failures is easily forgettable but at the same time neglecting it can cause great costs after product launch.
Since product development is not an easy process and there are a lot of different aspects to take into account. For instance fulfilling the mechanical requirements of product design and meeting the specification and quality criteria set by marketing. After making sure that everything is as it is supposed to be – that may not be the case. It can be really difficult and nerve wrecking to identify the flawed points, especially without proper equipment. This is where failure analysis, and more specifically, cross section analysis comes real handy.
Cross section procedure
Cross section is one of the best methods of doing a hardware failure analysis. It can be done in two ways. One is to concentrate to a particular point of the design for example the printed wiring boards (PWBs) or electronic components and their solder joints. The features of interest to be analyzed in cross section can be nanometer-scale metal and dielectric layers in semiconductors up to macroscopic pictures. The alternative approach might be concerned much more straightforward; cutting the whole product in half to see if there is something irregular.
Cross sections can be prepared by several methods; typically chosen based on the scale of the feature of interest. First, samples can be cut down into smaller pieces. For example interesting point around the flex or a failed component soldered to a PWB. Second, for sample preparation in cross section analysis the device is filled and submerged in epoxy. This allows us to have a good look inside without harming or having any impact on the components. Naturally, when cutting the product without epoxy, the process would destroy the electronics inside and device covers.
“The cross section is quite intriguing process when trying to find the root cause of a fault. When a fault is found, it is undeniable evidence for the customer and it enables the improvements to be done in the design“, says Mona Hämeenaho an experienced failure analysis at Grant4Com.
Inspection of cross sections
Viewing the internal structures of components, PWB, flex, the component solder joint or some other interesting point with a metallurgy microscope can reveal problems with manufacturing and material quality. For example this analysis can be used to help determine any plausible issues composed during the soldering process that could lead to solder fatigue and failure later. Moreover, solder joint cross sections are commonly prepared during failure analysis to see cracks in the solder. Crack morphology can lead to identification of the type of stress and ultimately the root cause of the solder joint failure.
Anticipating problems is intelligent product development
Failure analysis could be more utilized tool by the product developers. Admittedly, there are plenty of benefits to it such as higher quality and robust products.
“Finding a failure is always a joy. It helps customer who might have struggled a long time trying to troubleshoot an error without proper equipment. Cross section literally brings out the points of error that can be thoroughly investigated by the manufacturer afterwards. It truly speeds up the R&D process” says Mona.
However, every failure analysis is a journey into the unknown and it always teaches something new about manufacturing processes or structure of components. It is great pleasure for both the laboratory worker and customer.
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