Performing a “before a failure” investigation on electronics is typically done for various reasons. One reason is to identify weak components or sub-systems before committing to a full-blown production run and its associated expenses. Comparison testing of similar component parts to reduce costs and increase reliability of existing designs, or against a competitor’s offerings is another reason. A “before a failure” investigation can validate a design to satisfy customer or market specifications, or regulatory obligations, which is common among the aerospace and medical devices fields.
The methods used in any investigation fall into two broad categories: non-destructive physical analysis (NPA) and destructive physical analysis (DPA). The method chosen depends heavily on what is the desired result of a particular investigation.
Some investigations are purposely designed to be destructive, such as comparison testing of components from competing manufacturers, or inputting data for life time and other reliability calculations.
Examples of DPA: specimen cross sectioning, chemical decapsulation, Digital Image Correlation (DIC), “die and pry” solder joint analysis, sheer and pull testing of solder joints and bond wires, shock and vibration of assemblies. The most common DPA activities are cross section analysis of solder joints, PCB laminate construction and semiconductor packaging. The specimen is cut down to a manageable size, potted in epoxy, ground and polished to reveal the area of interest to be inspected.
Non-destructive tests leave the specimen intact for either later testing, actual use as a saleable product, or as evidence in a following investigation.
Examples of NPA: electrical characterization, from simple ohm meter measurements, volt-current (V-I) curve tracing, to surface insulation resistance (SIR) measurements along with various kinds of microscopy inspection – optical, acoustical and scanning electron (SEM). Digital Image Correlation (DIC) is sometimes considered non-destructive, and other times destructive, because it requires painting the test specimen. Additionally, exposure to various temperatures and humidity in conjunction with the above methods will be utilized.
Here are three real life examples why “before a failure” investigations are performed.
1. Market reconnaissance
A marketing team within a manufacturer of network controlled server room power distribution units (PDU) wanted to know how their product compared to the competition. DfR Solutions performed an investigation to help them understand their position in the market in comparison to their competitors. This investigation required two distinct tests -- first, a series of initial tests were performed to benchmark the important performance parameters of each manufacturer. The important performance parameters included how well each unit measured input and output voltages and currents, the accuracy of the calculations for power and efficiency, and reliability of operation at different elevated temperatures.
Following the initial tests, a long duration test at an elevated temperature of the PDUs was conducted for 1000 hours. The data from the two tests was compiled and presented to the customer. The customer used this information to better understand their position in the market and where to concentrate their efforts on making improvements to the product and market position. This was a NDA test because the customer’s test specimen was expected to survived, and did, the testing. Some of the competing units survived as well.
2. Reducing costs
A manufacturer of HVAC systems was performing a cost reduction plan on an existing product, which included comparing capacitors from several different manufacturers. The manufacturer wanted to know if they could change to a lower cost component without impacting reliability. The two significant parameters being investigated were cost and reliability within a group of similar components from different manufacturers. This investigation involved performing a temperature humidity bias (THB) test of various high voltage capacitors from different manufacturers for a measured period of time. This type of testing is an accelerated lifetime test, where the results of operation at the upper extreme of both temperature and humidity for 1000 hours can be used in life time prediction calculations of components operating at lower “real world” levels. This was an example of a DPA because the test was conducted intentionally until a percentage of the population failed.
3. Product surveillance -- qualification and continuous monitoring
Often, a manufacturer will perform a qualification of components from different suppliers, or as part of a continuous quality monitoring program.
A very common example of this is qualifying bare printed circuit boards (PCB) from several suppliers bidding on a product being developed. The PCBs are examined non-destructively using optical and X-ray microscopy, and then cross sectioned and examined with optical or SEM microscopy to judge important parameters such as plating quality thickness, drill hole sharpness, and finish. Using both NPA and DPA methods the quality and reliability of the bare PCB is assessed which aids the customer in making the choice on which supplier is the most economical.
Another common example is a fully assembled printed circuit board assembly (PCBA) examined with non-destructive and destructive methods as above, with an additional test called Ion Chromatography (IC) performed between the two methods. IC is used to measure the existence and level of damaging contaminates that are unavoidably created during the soldering process.
DfR Solutions offers many types of testing services that can help save money and increase customer satisfaction by producing more reliable, long lasting products. Visit the Services section of our website or contact us for a quote today.