Destructive Physical Analysis of Pi Filters

Gideon Analytical Laboratories was asked specifically to perform Destructive Physical Analysis (DPA) on Spectrum Control and Tusonix Pi filters, respectively, in order to compare performance and reliability. Destructive Physical Analysis includes the dissection of a device to determine construction, assembly, and compliance with certain standards and specifications. DPA on these Pi filters centered around construction and materials analysis.

DPA was performed on the Spectrum Control and Tusonix Pi filters, respectively. Both electronics manufacturers used a ferrite cylinder around a copper lead as the inductor. The lead, as it exited the ferrite cylinder, was soldered to a toroidal capacitor on both ends inside an epoxy hermetic sealed metal structure. The two Pi filters were electrically tested for resistance, capacitance, and inductance before being mechanically separated and examined. SEM-EDS was also conducted to determine material composition.

Cross-sectioning was the next step in DPA. It was started with the Spectrum Control Pi filter. There was voiding in the solder joint and a hairline interfacial crack between the capacitor terminal metal and the solder. This could be indicative of a lack of wetting. Cross-sectioning was also performed on several other Spectrum Control Pi filters, and all solder joints were excellent and free from voiding. Cross-sectioning was also performed on the Tusonix Pi filter. It had no cracks, and the epoxy seal was covered well and had made a good mechanical bond to the lead and body. Pi filters produced by the two different electronics companies had similar electrical characteristics. They both also had similar design and construction for achieving electrical filtering.

Gideon Analytical Laboratories cannot only provide failure analysis but also a variety of other analytical services as well. Analytical results from Destructive Physical Analysis (DPA) can also provide electronics companies with priceless information regarding construction, assembly, materials, and reliability. Whether it is analyzing good parts or bad parts, in production or in the application, Gideon Analytical Laboratories is here to help.