How to assess the quality of the surface treatment process of a 3D welding platform?

1. Visual Inspection
Observe the surface visually or with a magnifying glass to check for flatness and defects such as scratches, dents, oxidation, or contamination. Critical areas (such as welding contact surfaces) should be free of visible damage, and the surface finish must meet process requirements.
2. Plating Quality Assessment
Thickness measurement: Measure the plating thickness using non-destructive equipment such as an X-ray fluorescence spectrometer (XRF). For example, the ENIG process requires a nickel layer of ≥3-5μm and a gold layer of 0.05-0.15μm; the OSP film thickness needs to be stable at 0.2-0.5μm.
Wetting test: According to the IPC-TM-650 standard, the wetting angle of qualified pads should be <90°, and the solder spreading area should be >75% to prevent cold solder joints.
Foreign matter residue: Detect slump (<10%) using 3D SPI and visually inspect for flux residue or solder balls.
3. Surface Roughness Control
Surface roughness directly affects coating adhesion and is usually controlled within 1/5 to 1/4 of the dry film thickness of the coating. The roughness (Rz) of sandblasting treatment is recommended to be (4-6) × Ra, and the specific value needs to be adjusted according to process requirements. The stylus method is a commonly used detection method that can quickly quantify roughness.
4. Bond Strength Verification
Adhesion test: Using the 3M tape peel test, a plating detachment area of ​​<5% is considered acceptable.
Metallographic section analysis: Observe the plating structure through cross-section analysis; the area of ​​poor bonding at the nickel/gold layer interface should be <5%.
Layer-by-layer cutting test: Cut the coating down to the substrate; if there is no "peeling" between layers, it indicates strong bonding.
5. Process Parameters and Storage Conditions
Electroplating parameters: For example, a forward current density of 2 ASD and a reverse current density of 0.5 ASD in pulse plating can improve plating uniformity.
Storage environment: OSP boards need to be vacuum-packed within 36 hours, and the storage humidity of immersion silver boards should be <60% RH.