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February 2017 • The PCB Magazine 89 for measuring these properties is IPC-TM-650, method 2.4.24: Glass Transition Temperature and Z-Axis Thermal Expansion by TMA [6] . In addition to measuring the specific thermal ex- pansion values, obtaining information about the board's ability to withstand delamination of its layers at elevated temperature can also be investigated via TMA. There is a group of test methods for this type of delamination testing, with IPC-TM-650, method 2.4.24.1: Time to Delamination (TMA Method) [7] the most com- monly used. Clearly, a variety of steps that can be taken to help ensure you're getting what you paid for…and doing any testing is honestly better than doing none at all. PCB References 1. IPC-A-600 2. IPC-6012 3. J-STD-003B 4. IPC-TM-650, method 2.6.8E 5. IPC-TM-650, method 2.4.25c 6. IPC-TM-650, method 2.4.24c 7. IPC-TM-650, 2.4.24.1 Keith M. Sellers is operations manager with NTS in Baltimore, Maryland. To read past columns or to contact Sellers, click here. HOW STRONG IS YOUR FOUNDATION? NASA has select- ed two missions that have the potential to open new windows on one of the earli- est eras in the history of our solar system— a time less than 10 million years after the birth of our sun. The missions, known as Lucy and Psyche, were chosen from among five finalists and will proceed to mission formulation, with the goal of launching in 2021 and 2023, respectively. "Lucy will visit a target-rich environment of Ju- piter's mysterious Trojan asteroids, while Psyche will study a unique metal asteroid that has never been visited before," said Thomas Zurbuchen, as- sociate administrator for NASA's Science Mission Directorate in Washington. "This is what Discov- ery Program missions are all about—boldly going to places we have never been, to enable ground- breaking science." Lucy, a robotic spacecraft, is scheduled to launch in 2021. It's slated to arrive at its first des- tination, a main belt asteroid, in 2025. From 2027 to 2033, Lucy will explore six Jupiter Trojan as - teroids trapped by Jupiter's gravity in two swarms shar- ing the planet's or- bit, one leading and one trailing Jupiter in its 12-year solar cir- cuit. The Trojans are thought to be relics of an earlier era in the history of the solar system, and may have formed far beyond Jupiter's current orbit. The Psyche mission will explore a giant metal asteroid, known as 16 Psyche, about three times farther away from the sun than is the Earth. This asteroid measures about 130 miles in diameter and, unlike most other asteroids that are rocky or icy bodies, is thought to be comprised mostly of metallic iron and nickel, similar to Earth's core. Scientists wonder whether Psyche could be an ex- posed core of an early planet that could have been as large as Mars. NASA Selects Two Missions to Explore the Early Solar System