Evaluating Desorption Baking Cycles for Moisture Sensitive Integrated Circuits
Baking moisture sensitive ICs requires matching package thickness and carrier heat ratings to balance desorption speed against intermetallic lead oxidation risks.
Heat Deflection Temperature
Thermal Threshold
A standardized polymer metric determines the temperature at which a plastic material deforms by a specified amount under a predetermined mechanical load. To establish the heat deflection temperature of a given polymer, a specimen is placed in a heated oil bath and subjected to a flexural stress of either zero point forty-five megapascals or one point eighty megapascals. The temperature of the bath is raised at a uniform rate until the specimen deflects by zero point twenty-five millimeters.
Stress Application
The choice of applied stress during the test reflects the intended operational environment of the polymer component. Higher stress levels are used to evaluate materials designed for structural roles, while lower stress levels apply to enclosures that experience minor mechanical forces. Standardized test specimens must have precise dimensions to ensure that the flexural stress remains uniform across the sample.
Heating Rate
An accurate temperature ramp of two degrees Celsius per minute is maintained to prevent thermal gradients within the specimen. Inconsistent heating can cause premature deflection or delay the material response, resulting in an inaccurate reading. The oil bath must be stirred continuously to ensure uniform heat distribution.
Material Selection
Design engineers use this thermal measurement to choose appropriate materials for electronic enclosures that must withstand elevated operating temperatures without losing structural rigidity. Exceeding this thermal threshold during operation can lead to casing deformation, misalignment of internal components or mechanical failure of the assembly.