Humidity control inside electronic enclosures: Developing design principles based on empirical understanding

Salil Joshy*

*Corresponding author for this work

    Research output: Book/ReportPh.D. thesis

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    This PhD work was supported by Innovation fund Denmark and was part of IN-SPE (Innovation consortium for sustained performance of electronics) project. The aim of this PhD work was to understand the humidity build-up inside electronic enclo-sures and study suitable humidity control methods to improve climatic reliability of electronics. In this regard, the main focus of the work was the effect of enclosure design and packaging related parameters on humidity build up and humidity control.
    The use of electronic control units and devices in wide variety of applications and also in different climatic regions has led to more and more humidity related failures in electronics. Currently, the enclosure design for electronics are based on experi-ence gained over the years at major electronic manufacturers, rather than based on scientific knowledge. This work aims to contribute to the scientific understanding of humidity build up and humidity control techniques at enclosure level.
    Chapter 1 introduces the background to humidity related reliability issues in electronics. Also explained are the objectives of the current work and structure of this thesis. Chapter 2 reviews literature on water layer formation on printed circuit board assemblies (PCBA), humidity related failures and mechanisms of humidity transport into electronic enclosures. Chapter 3 reviews the methods currently used to prevent humidity related failures and suitable humidity control techniques in electronics. Chapter 4 summarises the materials and experimental methods used in this work. Results of the PhD work were appended with this thesis as individual research papers in chapters 5, 7, 9 and as non-manuscript form in chapters 6 and 8.
    Paper-1 studied forced condensation as a humidity control method in electronic applications. The effect of enclosure related parameters like opening sizes, enclosure volumes, cooler surface area and cooling temperature on relative humidity (RH) were studied. Paper-2 studied the effect of enclosure related parameters like opening size, inter-PCB spacing, heat capacity and power dissipation on humidity accumulation, condensation and degradation of surface insulation resistance (SIR) in an electronic enclosure with parallel arrangement of PCBs. The work in chapter 6 was done to answer fundamental questions on humidity transfer from warm to cold. The parameters studied were warm temperature, cold temperature and connecting hole size. Chapter 8 studied humidity and temperature inside an electronic enclosure with retained water.
    The investigations have demonstrated humidity transfer from warm to cold and have shown that preferential condensation based humidity control techniques were suitable for electronic applications. By suitable sizing of various enclosure openings and cooling temperature the RH inside the electronic enclosure can be reduced to prevent humidity related failures. Electronic enclosure related parameters like opening size, PCB spacing and heat capacity were found to affect humidity related reliability of electronics.
    Paper-3 studied a methodology to predict humidity and contamination related failures in common electronic circuits using experimental data of SIR. The method-ology was also used to identify more reliable circuit topologies.
    Original languageEnglish
    Place of PublicationKgs. Lyngby
    PublisherTechnical University of Denmark
    Number of pages102
    ISBN (Electronic)978-87-7475-553-1
    Publication statusPublished - 2018


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