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|Leakage Rates through LTCC Substrates for Extreme Environment Applications|
|Keywords: Leakage rates, Krypton-85, LTCC|
|A key challenge with many extreme environment applications is the development of substrate technologies that provide the necessary electrical interconnect but also are reliable. Many of these applications also have a requirement for hermetic packaging. As a result, one logical solution is the use of ceramics such as Low Temperature Cofired Ceramics (LTCC) that are very stable and have proven to be reliable under a wide variety of external conditions such as elevated temperatures, and mechanical shock. A popular approach is to mount components on one side of an LTCC substrate that is then sealed with a lid to create a hermetic environment for those components. Electrical interconnects are generally then feed through the LTCC to the bottom surface. However, a persistent difficulty affecting many applications is that the leak rates of gases or moisture introduced and retained within these structures are difficult to measure accurately using conventional tracer gas technologies. For example a small crack between the via metallization and the ceramic sidewall could create a pathway into the hermetic volume with a very small leakage rate. Therefore, the ability to quantify these leak rates is critical to high reliability applications. To resolve this issue the researchers have investigated leak rates through LTCC substrates using krypton-85 tracer gas technology. An important advantage of this technology is that the quantity of gas introduced into a device may be measured directly, thereby allowing detection of gases introduced into and retained in interfacial voids, traces, and other microscopic interstitial passages and connections that may be present in these substrates. This paper will report experimental results using krypton-85 tracer gas technology to identify and quantify very small leakage rates in LTCC substrates both prior to and after exposure to extreme environmental conditions.|
|Karl Rink, Professor
University of Idaho