IPC Class 2 vs. Class 3: What's the Difference?

2025-05-14

IPC Class 2 vs. Class 3: What's the Difference?

In the electronic interconnection industry, IPC stands for the global trade association. The primary goal of the IPC Class is to standardize the assembly, production process, and requirements of electronic components. In 1957, it was established under the Institute of Printed Circuits, which was later changed into the Institute for Interconnecting and Packaging Electronic Circuits.
The organizations publish the specifications and requirements regularly. The IPC standard is one of the most accepted protocols in the electronic industry. This IPC standard helps design and fabricate reliable, safe, high-quality PCB products.

We always talk about IPC Class 2 vs Class 3. What are the main differences between them in PCB manufacturing services?

Generally speaking, IPC Class 2 is the normal standard for most electronics, such as consumer electronics, industrial equipment, medical equipment, communication electronics, power and control, transportation, computers, testing, etc, while Class 3 is required for more electronics needed more reliability, such as automotive, militarily, marine aerospace, etc.

Voids in PTH-Copper Plating

Class 3–PCB Manufacturing	Class 2–PCB Manufacturing
PTH holes are plated perfectly. No void in the PTH hole at all.	Max. 1 void in 1 PTH hole. The void should be small. Void less than 5% of the PTH hole size. Max. 5% holes with voids. The void is less than 90 degrees from the drill.

Voids in PTH – Finished Coating

Class 3–PCB Manufacturing	Class 2–PCB Manufacturing
No void at all. Max. 1 void in 1 hole. Max. 5% holes with voids can be seen. The void length is less than 5% of the hole. The biggest void length is less than 5%	Max. 3 voids all in one hole. Max. 15% holes with voids can be seen. The void length is less than 10% of the hole. The biggest void length is less than 5%

Etched Marking (components notation)

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Class 3–PCB Manufacturing	Class 2–PCB Manufacturing
Etched marks are clear Etched marks are a little blurry, but they can be recognized. Etched marks have no affection for other copper traces.	Etched marks are not clear, but they can be recognized. If there is any part missing, not exceed 50% of the character. Etched marks have no affection for other copper traces.

Soda Strawing (the gap between the solder mask and base material)

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Class 3–PCB Manufacturing	Class 2–PCB Manufacturing
The solder mask connected with the base material is in good condition. There is no gap between the solder mask and the base material.	The copper width remains the same. Copper trace is covered by a solder mask, and no solder mask peels off.

Conductor (copper trace) Spacing

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Class 3–PCB Manufacturing	Class 2–PCB Manufacturing
Copper trace width is the same as the design. Extra copper is less than 20% of the total copper trace width.	Max. extra copper is less than 30% of the total copper trace width.

Out Layer Annular Ring-Supported Holes

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Class 3–PCB Manufacturing	Class 2–PCB Manufacturing
Holes in the center of the pads. The minimum ring size is 0.05mm.	No ring breakout. Ring breakout less than 90 degrees.

Out Layer Annular Ring-Unsupported Holes

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Class 3–PCB Manufacturing	Class 2–PCB Manufacturing
Drill in the centre of the pads. The minimum ring size is 0.15mm.	No ring breakout. Ring breakout is less than 90 degrees.

Surface Conductor Thickness (base and plating)

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Class 3–PCB Manufacturing	Class 2–PCB Manufacturing
Min. Copper plating is 20um.	Min. Copper plating is 25 um.

Wicking (plating residue)

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Class 3–PCB Manufacturing	Class 2–PCB Manufacturing
No wicking (plating residue) when we make cross sections. If there is any wicking, the max. The size is 80um.	No wicking (plating residue) when we make cross sections. If there is any wicking, the max. The size is 100um.

Solder Residue

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Class 3–PCB Manufacturing	Class 2–PCB Manufacturing
Max. Solder residue under the cover is 0.1mm. No solder wicking (residue) at the bendable parts. No effect on the copper trace or function.	Max. Solder residue under the cover is 0.3mm. No solder wicking (residue) at the bendable parts. No effect on the copper trace or function.

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