Trelic’s picture of the week – 08/2017

Can you guess what does this picture represent?

 

Use environment of electronics products can nowadays be practically anything. Lots of applications containing electronics are used in harsh environments, possibly causing reliability issues for the products. Corrosive environment is one of the most demanding use conditions. Air pollution, salt and dust with high levels of humidity often exists in use environments especially for industrial electronics causing corrosion. In addition to the use conditions, impurities from the processing or use of a product are often critical promoters for corrosion processes.

Corrosion may be a major reliability risk for new components and materials. Therefore, corrosion testing can be crucial especially for new designs which may not have any field data! Corrosion can be tested with several tests depending on the critical factors in the use environment. Possibilities include for example mixed flowing gas (MFG) testing, salt spray testing, high humidity testing and dust testing.

The picture above is taken from a test sample tested in mixed flowing gas (MFG) testing. This test is mimicking exposures to atmospheric pollution. Corrosive gases used in the test were hydrogen sulfide (H2S), sulfur dioxide (SO2), chlorine (Cl2) and nitrogen dioxide (NO2). The studied structure is an immersion silver (ImAg) plated copper area on PCB after six weeks of MFG testing. Severe corrosion can be seen to have occurred!

It is good to bear in mind that surface finishes and coatings play a major role in protection against corrosion. There are plenty of different surface finishes available for printed circuit boards (PCB). Other surface finishes may provide better protection against corrosive environments compared to ImAg shown in the picture. However, it is important to consider the use environment, since different surface finishes behave differently in different conditions. Additionally, in many applications good-quality conformal coating may also prevent corrosion or slow down the rate of corrosion.

P.S. Our MFG tester has currently open testing spots available! Please contact juha.pippola@trelic.fi for more information about MFG testing!