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Impact of Dust on PCB Assembly Reliability
Analysis Lab |
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Authored By:Bo Song, Michael H. Azarian and Michael G. Pecht Center for Advanced Life Cycle Engineering (CALCE) University of Maryland, College Park, MD TranscriptAtmospheric dust consists of solids suspended in air. Dust is well known for its complex nature. It normally includes inorganic mineral materials, water soluble salts, organic materials, and a small amount of water. The impact of dust on the reliability of printed circuit board assemblies is ever-growing, driven by the miniaturization of technology and the increasing un-controlled operating conditions with more dust exposure in telecom and information industries. A fundamental and systematic study on the impact of dust is needed, since not much research has been done in this area. Since dust is always present in the atmosphere, under what conditions is dust a reliability concern for electronics? What are the key characteristics of dust? Are some dust types worse than others? Should there be classifications of dust? How will different combinations of dust, voltage, relative humidity, temperature, and other factors affect electronic materials and circuits? This paper presents some results towards answering these questions. SummaryAtmospheric dust consists of solids suspended in air. Dust is well known for its complex nature. It normally includes inorganic mineral materials, water soluble salts, organic materials, and a small amount of water. The impact of dust on the reliability of printed circuit board assemblies (PCBAs) is ever-growing, driven by the miniaturization of technology and the increasing un-controlled operating conditions with more dust exposure in telecom and information industries. A fundamental and systematic study on the impact of dust is needed, since not much research has been done in this area. We started by asking some basic questions on dust. Since dust is always present in the atmosphere, under what conditions is dust a reliability concern for electronics? What are the key characteristics of dust? Are some dust types worse than others: e.g., dust that is more hydrophilic? Should there be classifications of dust? How will different combinations of dust, voltage, relative humidity (RH), temperature, and other factors affect electronic materials and circuits? This paper presents some results towards answering these questions. We designed a group of experiments using real life dust collected from both indoor and outdoor areas. AC impedance spectroscopy (IS) was employed as the measurement technique for this research. We designed test coupons with adjustable spacing between electrodes and measured their electric properties under different relative humidities. We analyzed aqueous solutions produced from dust samples were using their pH and conductivity. And we further analyzed the compositions of the dust samples. We found that dust had a significant impact on the reliability of PCBA. Relating the test results to the analysis results, indoor dust is more sensitive to the change of relative humidity compared to outdoor dust due to the water soluble salts and particle size. At the same dust deposition density, indoor dust is more susceptible to induce moisture related failure, such as loss of surface insulation resistance, electrochemical migration, and corrosion. ConclusionsWe designed a group of experiments to gain some fundamental understanding of the physics of failure of dust contamination. We used the dust collected from the field instead of a mixture of chemical compounds to simulate the real dust. The test results were more realistic representation of the dust impact on the printed circuit assembly. AC impedance spectroscopy (IS) was employed as the measurement technique for the dust research, as it can provide interfacial and bulk properties of the overall electrochemical system without losing the SIR information measured by DC voltage. To our knowledge we are the first ones to use IS to analyze the effects of dust. The key findings of this paper are listed below.
Initially Published in the IPC Proceedings |
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