SMT Packaging Moisture Sensitivity Level Classifications and Bake Desorption Profiles
Exceeding component floor life limits risks catastrophic reflow popcorning; restore parts via J-STD-033 validated bake profiles before surface mount assembly.
Package Outgassing
Gaseous Emission
The release of volatile organic compounds and moisture from the plastic or adhesive materials of an integrated circuit package occurs when the device is subjected to high temperatures or low-pressure environments. This phenomenon, known as package outgassing, can deposit thin films of contaminants onto sensitive optical elements, contacts or nearby solder joints. It is a major concern in high-vacuum space applications and high-reliability aerospace environments.
This emission ceases once the volatile components have been completely driven off. The outgassing characteristics of epoxy underfill materials and glob tops are also profiled using thermal gravimetric analysis to ensure thermal stability.
Contamination Mechanism
Condensation of the released vapors on cold surfaces within a sealed enclosure creates a layer of residue. This residue degrades the performance of laser lenses and sensor windows. It can also cause electrical leakage across close-spaced traces or compromise the adhesion of conformal coatings.
Choosing materials with low outgassing characteristics is necessary for sealed electronic assemblies.
Mitigation Procedure
Laminates and packages are subjected to high-vacuum baking before final assembly to drive off volatile elements. Standard tests measure the total mass loss and the collected volatile condensable material to certify components. Materials that lose more than one percent of their total mass are generally rejected for space use.
This verification step prevents failure in extreme environments.