DIMPLED BALL GRID ARRAY PROCESS DEVELOPMENT FOR SPACE FLIGHT APPLICATIONS
Authors: Sharon L. Barr and Atul Mehta Company: Jet Propulsion Laboratory` Date Published: 2/13/2001
Pan Pacific Symposium
Abstract: With smaller and smaller Printed Wiring Board (PWB) form factors, such as CompactPCI, the need for smaller packages with high I/Os has grown significantly. Thus, the use of Ball Grid Array packages has become necessary for space flight applications. A Jet Propulsion Laboratory/NASA technology and system development program that services various spacecraft missions uses a 3U CompactPCI form factor. The System Input/Output board requires a large amount of I/Os and has limited area, so conventional packages, such as quad flat packs will not fit. Thus, the use of Ball Grid Arrays (BGAs) with much smaller package dimensions than leaded packages are needed to meet area requirements and are being evaluated for space flight applications. Since this type of package has not been used in past space flight environments, it was necessary to develop a process that would yield robust and reliable solder joints. The process, developing assembly, inspection and rework techniques, were verified by conducting environmental tests. The test article was a printed wiring assembly (PWA) consisting of four daisy chained D-BGA packages. Visual inspection of the outer solder joints and real time X-ray were used to verify solder quality. Three environmental tests were conducted: random vibration at 0.2 g2/Hz, pyro shock at 2000g for 50 ms, and thermal cycling from -55C to 100C for 200 cycles. The test article was electrically monitored for shorts and opens at or above 1 s during all environmental tests. After testing, Scanning Electron Microscope (SEM) analysis was performed on various D-BGA cross sections to determine the quality of the package-to-board interface. The 472 D-BGA solder attachments passed the above environmental tests meeting the minimum requirements for use on space flight electronics.