Polymer Die Attach Selection Criteria for Low Drift Inertial Measurement Units
Polymer die attach selection governs MEMS IMU bias drift by balancing storage modulus, glass transition temperature, and long-term viscoelastic stress relaxation.
NASA SP-R-0022A
Vacuum Standard
Space agency specifications define the required thermal-vacuum outgassing parameters and evaluation criteria for polymers used in orbit. The document designated as NASA SP-R-0022A establishes the standardized testing methodology for measuring material mass loss and volatile condensation under vacuum conditions. This standard provides a consistent framework for selecting spacecraft materials that will not contaminate sensitive surfaces.
Testing Method
The protocol requires placing a sample in a vacuum chamber at less than twenty-five microtorr and heating it to one hundred and twenty-five degrees Celsius for twenty-four hours. This thermal-vacuum exposure drives off the volatile species, which are then analyzed. The results are calculated based on the starting mass of the specimen to determine the overall mass loss.
Material Acceptance
Spacecraft components must be made from materials that exhibit low volatile emissions to prevent performance loss of thermal control systems. Under NASA SP-R-0022A, materials are approved for space flight if they have a total mass loss below one percent and a collected volatile condensable material below one tenth of a percent. These limits ensure that outgassed molecules will not deposit on optics.
Quality Verification
Manufacturing batches of critical adhesives and potting compounds must be regularly audited to ensure compliance with these outgassing limits. This continuous checking is necessary because small changes in the chemical formulation or curing cycle can cause a batch to fail the NASA SP-R-0022A limits. Certified testing laboratories perform these audits and issue compliance certificates before the materials are released for satellite assembly.
This rigorous quality control process is essential for preventing the failure of optical instruments during long-term space missions.