edfas.org 11 ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 28 NO. 3 MOISTURE AND MICROELECTRONIC DEVICES Philipp wh Schuessler Consultant, retired, Preston Hollow, New York philippwhschuessler@gmail.com EDFAAO (2026) 3:11-14 1537-0755/$19.00 ©ASM International® INTRODUCTION This article covers some of the milestones and pitfalls encountered over the past half century in the endeavor to accurately ascertain moisture levels in high reliability microelectronics. As the history is unveiled, one will hopefully gain insight into how a simple molecule of just three atoms (i.e., water) has confounded the microelectronics community, and how previous practices and assumptions in the manufacturing line have been shown to be the death knell for a product. One of the subsequent conclusions regarding moisture in microelectronics for all to keep in mind is that “chemistry happens,” and it does so continuously over time. That conceptually simple water molecule is ubiquitous and contributes significantly to changes occurring within a sealed device. The following history is divided into three sections: (1) the early days, when microelectronic packaging concepts and processes were being developed; (2) the problems with creating a hermetic package; and (3) the analytics developed to prove the precision and accuracy of moisture content data. THE EARLY YEARS By the mid-1950s, transistors were becoming the basis for the emerging microelectronic community. New packaging concepts for these devices were also being developed as plastics and polymers were also rapidly evolving. By the 1960s, it was realized that these devices needed to be kept dry. The early solution to moisture-related problems was to require all microelectronic devices to be hermetic and free of all organic compounds. Solutions available at that time were unfortunately expensive, design limiting, and impossible to prove. At the same time, the plastics industry wanted to be involved with the booming microelectronics industry and advertised numerous moisture “resistant” capabilities. Despite many new materials and their improved barrier properties, it was realized in the early 1970s that no polymer is impermeable to water, regardless of the supplier’s claims. The problem of maintaining hermeticity and cleanliness in the early days was best exemplified when a Saturn rocket failed to launch. Subsequent failure analysis showed that the problem was due, in part, to corrosion of a microcircuit. During the subsequent failure analysis, a circuit line within an onboard microcircuit device was found to have a spot of dried spittle (Fig. 1). The moisture (and most probably, the ionic species within it) from a suspected sneeze was more than sufficient to corrode the circuit, and the heavy vibrations within the rocket during the final seconds of launch caused the circuit line to break. The subsequent costs of failure analysis, stand down of the mission, refit, etc. exceeded $10,000,000. As the manufacturing of hermetic metal and/or ceramic devices became the accepted packaging concept for high reliability use in military and aerospace applications, the need to prove that the cavity of a device was truly dry became a necessity. In the mid to late 1970s, formal Fig. 1 A photo of a Saturn 9 rocket circuit trace that failed due to unwanted moisture.[2]
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