Six-layer boards are widely used in high-speed signal transmission, differential signal applications, and high-frequency circuits. Impedance control and electrical performance are mandatory inspection items. This article explains industry-standard specifications for impedance, electrical testing, high voltage, and ionic contamination.

### I. Impedance Control Inspection Standards

**Single-ended Impedance**

- Standard: ±10%

- High Precision: ±5%

**Differential Impedance**

- Mainly 90Ω, 100Ω, and 120Ω

- Tolerance same as above

**Impedance Testing Requirements**

- At least one test coupon per panel

- Impedance report required for each batch

**Consequences of Impedance Non-conformance:** Signal distortion, packet loss, interference, incompatibility.

### II. Electrical Open/Short Circuit Testing

- 100% coverage with flying probe testing

- No opens, shorts, or missed defects allowed

- Test data archived for traceability

### III. High Voltage Insulation Test

- Adjustable from 100V to 500V based on customer standards

- No breakdown, leakage current, or flashover

- Ensures safe operation in high-voltage environments

### IV. Ionic Contamination Test

- Standard: ≤ 6.5 μg/cm²

- High ionic contamination can lead to electrochemical migration, CAF failure, and short circuits.

### V. Solderability Test

- Uniform solder wetting on pads

- No poor wetting, dewetting, or solder masking

- No oxidation or discoloration

The electrical performance of six-layer boards directly determines product functionality and stability. **Impedance control, electrical testing, high voltage, and ionic contamination must be 100% inspected and合格 before shipment.**

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### Final Outgoing Quality Control Standards

*Applicable for Quality Departments, Customer IQC, and Procurement Acceptance.*

#### I. Visual Inspection Standards

**Board Surface**

- No scratches, dents, oxidation, or stains

- No white spots, blistering, or delamination

**Solder Mask**

- Uniform color, no whitening, pinholes, blistering, or peeling

- No misalignment, no solder mask on pads

**Silkscreen**

- Clear characters, correct orientation, not overlapping pads

**Surface Finish**

- Uniformity for ENIG, HASL, OSP; no oxidation

#### II. Dimensions and Warpage

- Outline dimensions: ±0.1mm

- Slot and hole positions: ±0.05mm

- Board bow and twist: ≤ 0.7%

#### III. Reliability Verification Standards

**Thermal Stress Test**

- 288°C for 10 seconds, 3 cycles: No delamination, no hole wall cracking

**Adhesion Test**

- 3M tape test for solder mask and silkscreen: No peeling

**Impedance Test**

- Report required, must meet specifications

**Micro-section Test**

- Hole copper thickness, lamination quality, dielectric layers must meet requirements

#### IV. Outgoing Packaging Inspection

- Anti-static packaging

- Protection against moisture, scratching, and bending

- Labels clear: Part number, quantity, revision, date code

#### V. Final Release Principle

Six-layer boards must meet all criteria for release:

- Inner layer inspection合格

- Lamination inspection合格

- Drilling and plating inspection合格

- Impedance test合格

- Electrical test合格

- Visual inspection合格

- Reliability test合格

As high-reliability boards, six-layer PCBs must undergo **full-item, high-standard, and traceable** final inspections to ensure the long-term stability, safety, and reliability of the end product.