Inspection | Inspection Standards and Methods for Electroplated Products

1. Film thickness inspection

Film thickness detection is the primary step in electroplating quality control, primarily performed using an X-ray fluorescence spectrometer (X-RAY). This device excites atoms in the coating by emitting X-rays and analyzes the energy intensity of the returned fluorescence spectrum to determine the coating thickness and composition. In actual operation, special attention should be paid to the following:

1. Equipment calibration management: Spectral calibration must be performed daily when the machine is turned on, gold-nickel standard calibration must be performed weekly, and cross-line optical calibration must be completed monthly to ensure that the measurement system error is controlled within ±5%.

2. Establishment of material database: Independent test files need to be established for different substrates (such as C19400 copper alloy, C7025 phosphor bronze, etc.). The files should include substrate composition (such as Sn content 4%), coating structure (such as Au/Ni/Cu) and thickness compensation coefficient.

3. Measurement specifications: The probe must be aligned vertically with the test surface. Each measurement point should be repeated three times to obtain the average value. For special-shaped terminals, key functional surfaces (such as contact areas) must be selected as required measurement points.

2. Adhesion test

Plating adhesion is a core indicator that affects product reliability and requires a combined testing method:

1. Bending test method:

• Use an uncoated copper sheet with the same thickness as the sample as the gasket

• Use electronic digital pliers with an accuracy of 0.01mm to perform 180° bending

• Judgment standard: When the bending radius is ≤1mm, the coating has no cracking or peeling; when observed under a 50x microscope, the coating peeling area is ≤5%

2. Tape test method:

• Use 3M #600 transparent tape and roll it 3 times with a 2kg pressure roller.

• The tearing angle is strictly maintained at 90±5° and the speed is controlled at 300mm/s

• Failure judgment: If the tape adhesion area ≥ 10% of the coating is considered unqualified

3. Failure analysis:

• Use EDX spectrum to analyze the composition of the peeling surface and determine the failure interface (such as Ni/Cu interface)

• Combined with X-RAY to measure the thickness of the residual coating and locate the problem process (such as insufficient pre-nickel plating thickness)

3. Solderability test

Welding performance evaluation requires simulation of actual production process conditions:

1. Direct immersion tin method:

• Use no-clean rosin-based flux (ROSH compliant)

• The tin furnace temperature is controlled at 235±2℃ and the immersion time is 5±0.5s

• Acceptance criteria: Solder climbing height ≥ 2 times the terminal thickness, wetting angle ≤ 35°

2. Aging test:

• Steam aging conditions: 85°C/85%RH environment, for 16 hours

• After aging, 3 welding-desoldering cycles are required

• Products with special requirements must pass the third level acceptance of J-STD-002B standard

4. Appearance Inspection

Adopting a graded inspection system:

1. Class A surface (contact functional area):

• No particles with a diameter greater than 20 μm under a 50x microscope

• Color difference ΔE≤1.5 (compared with standard color plate)

• Surface roughness Ra≤0.2μm

2. Class B surface (non-functional area):

• ≤3 pits with a diameter of <50μm are allowed

• Slight flow mark length ≤1mm

• Slight discontinuous color difference is acceptable

3. Defect classification:

• Fatal flaws: exposed bottom, blistering, cracks

• Main defects: obvious color difference, foreign matter adhesion

• Minor defects: slight scratches, water marks

5. Packaging inspection

Implementing a double-nuclear mechanism:

1. Inner Packing:

• Anti-static carrier tape width tolerance ±0.2mm

• Reel axial runout ≤1mm

• Vacuum packaging humidity indicator card shows ≤10%RH

2. Outer packaging:

• Corrugated cardboard edge compression strength ≥7KN/m

• The stacking test passed the 3-layer 1.5m drop test

• Label information includes RoHS/REACH compliance statement

6. Salt spray test

Select the test method based on the application scenario:

1. Standard Test (NSS):

• 5% NaCl solution, pH 6.5-7.2

• Constant temperature of 35±1℃, sedimentation rate 1.5ml/80cm²/h

• Judgment standard: No substrate corrosion after 96 hours

2. Accelerated test (CASS):

• Add 0.26g/L CuCl₂

• 50±1℃ test temperature

• Acceptance requirements: 8 hours is equivalent to NSS 96 hours effect

3. Failure determination:

• Gold-plated parts: corrosion area ≤ 0.1%

• Tinned parts: discoloration area ≤ 5%

• If red rust appears, it is unqualified.

Special testing requirements

1. Porosity test:

• Gold plating was performed using the nitric acid vapor method (25 μm filter paper)

• Palladium nickel plating using gel electrolysis (0.5V voltage)

• Acceptance criteria: Pore density ≤ 5/cm²

2. Environmental reliability:

• High temperature and high humidity: 85℃/85%RH/1000h

• Temperature cycle: -40℃~125℃/100 times

• Sulfide test: according to ASTM B809 standard