Advanced IPC Class 3 Compliance

While most PCBs are produced and assembled according to IPC-A-600/IPC-A-610 Class 2 standards, which are suitable for consumer electronics, computer peripherals, telecommunications, IoT devices, robotics, LED lighting, test and measurement, and industrial controls, there are specific industries where higher standards are essential. For critical applications such as automotive, medical, military, aerospace, and life support systems, IPC-A-600/IPC-A-610 Class 3 standards are required. In even more demanding environments like military and aerospace, IPC Class 3/A is mandated, offering an elevated level of reliability.

At LEAPPCB, we are fully equipped to deliver PCBs manufactured to IPC Class 3 and IPC Class 3/A standards, ensuring that your products meet the highest industry requirements.

Key Acceptance Criteria for IPC-A-600 Class 3 PCBs:

Minimum copper plating thickness in PTH (Plated Through Hole) walls:
- IPC Class 2: PTH wall thickness ≥ 20 μm
- IPC Class 3: PTH wall thickness ≥ 25 μm

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Stringent IPC Class 3 Standards for PCB Manufacturing

Minimum Annular Ring for PTH:

Copper Conductor Width:

Hole Wall Copper Plating Voids:

Minimum Annular Ring for PTH:

Copper Conductor Width:

Hole Wall Copper Plating Voids:

Solder Mask Straw Gaps:

IPC Class 2: Straw gaps may be acceptable under specific conditions.
IPC Class 3: Absolutely no straw gaps permitted, ensuring a flawless finish.

Copper Plating Wicking:

IPC Class 2: Wicking allowed up to 100 µm.
IPC Class 3: Stricter control with wicking limited to a maximum of 80 µm for enhanced reliability.

Tin Filling in PTH Holes:

IPC Class 2: Requires a minimum of 50% hole wall filling with tin for through-hole pins.
IPC Class 3: Demands a higher standard with at least 75% hole wall filling to ensure superior solder joint reliability.

Design Tip: To achieve optimal tin filling, especially for IPC Class 3, it’s recommended to design PTH holes with a diameter over 15 mils for component pins. This allows for a 7.5 mils clearance on each side, facilitating easier and more consistent solder paste flow and filling. Always adhere to customer specifications and standards for the highest quality assembly.

Wetting on SMT Components: IPC-A-610 Class 3 vs. Class 2

IPC Class 2 Criteria:

Tin presence is required on the vertical surface of SMD components.

IPC Class 3 Criteria:

A higher standard is enforced, with a minimum fillet height of 0.5mm or 25% of the component’s height, ensuring a more robust and reliable solder joint.

Key Insight: Meeting IPC Class 3 requirements ensures superior solder joint integrity, crucial for high-reliability applications.

Side Overhang on SMD Components: IPC-A-610 Class 3 vs. Class 2

IPC Class 2 Criteria:

Side overhang should be less than 50% of the component/pad area.

IPC Class 3 Criteria:

A stricter requirement where side overhang must be less than 25% of the component/pad area, ensuring higher precision and reliability in assembly.

Key Insight: Adhering to IPC Class 3 standards guarantees tighter control over component placement, which is essential for critical applications where performance and durability are paramount.

End Joint Width on SMD Pads:

IPC Class 2 Standard: The end joint width must be a minimum of 50% of the SMD component/pad area.
IPC Class 3 Standard: Requires a more stringent minimum end joint width of 75% of the SMD component/pad area, ensuring stronger and more reliable solder joints.

Side Overhang on IC Pins:

IPC Class 2 Standard: Allows a side overhang of less than 50% of the pin width or a minimum of 0.5mm, whichever is less.
IPC Class 3 Standard: Demands tighter control with a side overhang of less than 25% of the pin width or a minimum of 0.5mm, whichever is less, ensuring higher precision in critical applications.

Key Insight: The stricter requirements of IPC Class 3 standards for end joint width and side overhang are crucial for applications where reliability and durability are non-negotiable. These tighter tolerances help to ensure a robust and consistent performance of the assembled PCBs.

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