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.
Leadframe Plating
Coating Composition
A thin metallic layer deposited onto a copper or iron alloy substrate provides corrosion protection and ensures solderability for semiconductor packaging. During manufacturing, leadframe plating processes apply layers of nickel, palladium and gold to the outer leads to enable reliable wire bonding and printed circuit board attachment. This coating must be uniform across all leads to prevent variation in solder joint quality.
Solderability Retention
The deposited layers act as a barrier against oxygen diffusion, preventing the underlying copper alloy from oxidizing before assembly. High-quality plating maintains its soldering performance even after prolonged storage in uncontrolled warehouse environments. If the plating is too thin or uneven, copper atoms can migrate to the surface and form oxides that resist solder wetting.
Thickness Control
X-ray fluorescence instruments measure the thickness of each metallic layer to verify compliance with semiconductor packaging specifications. Measuring the palladium and gold layers ensures that they are thick enough to protect the nickel barrier but thin enough to avoid brittle solder joints. If the gold layer exceeds the specification, gold embrittlement can occur in the reflow solder joints.
Adhesion Test
The strength of the plating bond is evaluated by bending the leads and inspecting for flaking or peeling. This test guarantees that the metallic layers remain intact during subsequent lead forming and trim operations.