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.
Outgassing Total Mass Loss
Mass Measurement
Gravimetric analysis of material weight before and after exposure to high vacuum and elevated temperature determines the volatility of solid substances. The parameter known as outgassing total mass loss is calculated as the percentage decrease in the specimen’s initial mass after a standardized thermal-vacuum bake-out. This value indicates the amount of volatile matter that has been driven off into the vacuum.
Thermal Vacuum
Specimens are subjected to a temperature of one hundred and twenty-five degrees Celsius for twenty-four hours under a deep vacuum to accelerate the release of volatile compounds. This process releases adsorbed gases, water vapor and low-molecular-weight species that are loosely bound within the polymer matrix. The resulting outgassing total mass loss serves to compare different candidate materials for space flight applications.
Performance Limit
International space agencies enforce a maximum threshold of one percent for this parameter to qualify materials for use on satellites. If the outgassing total mass loss of a material exceeds this value, the material cannot be used in high-vacuum environments due to the risk of structural degradation or contamination of adjacent systems. This limit is verified during pre-flight material screening.
Moisture Compensation
Polymer materials often absorb significant amounts of water vapor from the ambient air prior to testing. To isolate the outgassing total mass loss of the polymer itself from this harmless water loss, the specimen is pre-conditioned and then weighed again after the vacuum test. This protocol ensures that materials are not unfairly rejected due to high ambient humidity during storage.
The resulting corrected value provides a much more accurate representation of the material’s actual stability under space conditions, ensuring reliable selection for long-term orbital missions.