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.
Solderability Degradation
Surface Oxidation
A progressive reduction in a metal surface’s capacity to be wetted by molten solder occurs due to environmental exposure or aging. Over time, solderability degradation affects component leads and printed circuit board pads as they react with atmospheric moisture and oxygen. This process results in the formation of non-reducible oxides that act as a barrier to solder flow.
Contamination Pathway
In addition to oxidation, organic contaminants from packaging materials or airborne pollutants can deposit on the metal surfaces. These contaminants block the flux from making direct contact with the metal, preventing the chemical reduction of oxides during the reflow process. Proper handling and protective packaging are required to shield the parts from these external agents.
Wetting Evaluation
The solderability of a surface is evaluated using wetting balance testing or the dip and look method. A wetting balance test measures the forces exerted by the molten solder on the test specimen over time, producing a curve that describes the speed and extent of wetting. This quantitative measurement allows manufacturers to predict how the parts will perform during assembly.
By analyzing the force curve, technicians can detect the onset of degradation before the components are used on the production floor.
Storage Limit
To prevent this loss of performance, components are stored in dry cabinets or vacuum-sealed bags with desiccants. These controlled environments extend the shelf life of the parts by slowing down the chemical reactions that cause the surface to degrade.