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.
Desorption Bake Cycle
Thermal Process
Thermal processing removes adsorbed moisture or volatile contaminants from a substrate or package through controlled heating. A desorption bake cycle operates by increasing the kinetic energy of water molecules trapped within porous materials. This elevation in temperature allows the molecules to overcome surface binding forces and exit the material as vapor.
Implementation Protocol
Execution involves placing components in a vacuum or dry nitrogen environment to prevent re-absorption or oxidation during the heating phase. The desorption bake cycle requires specific ramp rates to avoid internal pressure build-up that could fracture delicate ceramic or plastic housings. Standard industrial profiles often hold the temperature at 125 degrees Celsius for durations ranging from several hours to several days depending on the moisture sensitivity level of the device.
Moisture Management
Material thickness determines the necessary soak time because moisture diffusion rates follow a square-law relationship with depth. If the desorption bake cycle is truncated, residual internal water may lead to delamination during subsequent high-temperature soldering.
Yield Limitation
Verification of effectiveness relies on mass-balance weighing or residual gas analysis. A desorption bake cycle is considered complete when the rate of mass loss falls below a specified threshold defined by the assembly standard.