Qualification of the Samtec SEAM and SEAF connectors for use as a printed circuit board assembly (PCBA) stacking connector in space applications

The Johns Hopkins University Applied Physics Laboratory’s (JHU/APL) modular electronics design on past space missions leverages the through-hole IEH Hypertronics stacking connector. To meet the needs of the upcoming Dragonfly mission to Titan, APL searched for a higher density option because a major limiting factor will be printed circuit board assembly (PCBA) space. The Samtec SEAM and SEAF connectors were identified as the best candidate to flow through a full space environmental test qualification. The connector needed to stack PCBAs together, have 200+ input/output (I/O), survive vibration, shock, and thermal environments, be low outgassing, and accomplish greater than 200 MHz signal integrity. The SEAM and SEAF connector pair were also attractive because of their surface mount instead of through-hole board attachment as well as small pitch (0.050’’). Although the SEAM and SEAF connectors do not fall under the worrisome ‘tuning fork’ category, they do not have a multi-point contact required by EEE-INST-02 so a qualification test was the only way to prove reliability of the connectors for space application.The completed test units undergoing environmental testing consisted of two 5-"slice" test "boxes", one for 240-pin connectors and one for 400-pin connectors. Each slice consisted of SEAM and/or SEAF connectors assembled to a 6.5’’ x 3.7’’ x 0.093’’ printed circuit board (PCB) and mounted into an aluminum frame with a stiffener surrounding the connector to minimize dynamic displacement due to vibration. Additional solder was deposited on the board during the assembly process via stencil as well as jet printing before the connector was hand placed onto the PCBA. Both methods to complement the solder charged connector leads were successful in securely attaching the connectors to the board without shorts or opens as confirmed by X-ray and CT scanning. Each test box contained four SEAM and four SEAF connectors as each end slice only contained one connector to have a closed-loop daisy chain that could be monitored for four-wire resistance to assess continuity and intermittence. The 5-slice boxes were assembled by mating each slice to its adjacent neighbor one at a time followed by the inclusion of end covers and threaded rods.The qualification test followed APL’s test-as-you-fly principle. Prior to box assembly, a 20-cycle mate and demate test was performed on each connector interface between slices to confirm the integrity of each lead’s gold plating. Random vibration to protoflight GEVS 14.1 gRMS and shock testing to 2828 g’s were conducted in all three axes with intermittence monitoring to 50 nanosecond resolution. Subsequently, 400-plus cycles of in-air thermal cycling from -40 to +125 °C was completed to bound the harshest conceivable thermal cycling mission at APL. Every step of the test plan, a four-wire resistance measurement was taken to confirm the daisy chain connection and consequently that the stacking connectors were functioning as intended. Cross-sectioning was pursued to assess solder joint integrity after the rigorous environmental testing and minimal damage is under assessment for further risk mitigation. By completing a connector assembly process followed by a comprehensive qualification test on flight-like test boxes, the SEAM and SEAF connectors will proceed for use in space applications.