The Differences between IPC Class 2 and Class 3 for the Printed Circuit Board (PCB) Inspection

The Differences between IPC Class 2 and Class 3 for the Printed Circuit Board (PCB) Inspection

Item PCB Inspection Description Class 2 Class 3
1 PCB Hole Void Each hole should not have more than one void within
5% of the total number of holes in the PCB.		 Void not allowed.
2 PCB Surface Treatment: exposed copper on voids Each hole should not have more than three voids within 5% of the total number of holes in the PCB. Each hole should not have more than one void within 5% of the total number of holes in the PCB.
3 Minimum copper annual ring for PCB outer layer plated holes
  1. When inspecting the PCB visually, the angle of the broken ring on the solder pad should not exceed 90 degrees.
  2. The reduction at the junction of the PCB solder pad and conductor should not exceed 20% of the conductor width.
  3. The connection at the PCB solder pad and conductor must not be less than 0µm (1,969µin) or smaller than the minimum conductor width, whichever is smaller.
  1. The minimum annular ring width on the PCB is 50µm (1,969µin).
  2. In isolated defect areas, the minimum annular ring width on the outer layers can be reduced by up to 20%.
4 Minimum annual ring width for PCB inner layer plated holes If the reduction in width at the junction of the PCB solder pad/conductor is less than 20% of the conductor width, a broken ring within a 90-degree range is acceptable. The minimum annular ring width on the PCB inner layers should be 25µm (984µin).
5 Non-plated through-holes on the outer layer of the PCB
  1. The broken ring on the solder pad must not be more than 90 degrees during visual inspection.
  2. The reduction at the junction of the solder pad and conductor must not exceed 20% of the conductor width.
  1. The minimum annular ring width on the PCB is 150µm (5,906µin).
  2. In isolated defect areas, the minimum annular ring width on the outer layers can be reduced by up to 20%.
6 Copper plating thickness for PCB tented vias. 5µm (0.0002in) 12µm (472µin)
7 Maximum depth of dent on plated through-holes after filling. 127µm (0.005in) 76µm (0.003in)
8 PCB copper plating area (holes and surfaces): average copper thickness 20µm 25µm
9 PCB copper plating area (holes and surfaces): minimum thickness. 18µm 20µm
10 PCB wicking Maximum 100µm (3,937µin) Maximum 80µm (3,150µin)
11 PCB inner layer contaminants Not allowed on the PCB.
12 PCB inner layer copper foil cracks. Not allowed on the PCB.
13 PCB outer layer copper plating cracks. Not allowed on the PCB.
14 PCB hole wall / corner cracks. Not allowed on the PCB.
15 PCB inner layer delamination Not allowed on the PCB.
16 PCB plating delamination Not allowed on the PCB.
Printed Circuit Board (PCB) manufacturers often receive inquiries from customer designers about the differences between IPC Class 2 and Class 3. IPC Class is a classification system used to differentiate the product types and levels for the manufactured PCBs life, performance, reliability, and appearance.

Differentiation of Printed Circuit Board (PCB) between Product Types and Levels:

Three classes of Printed Circuit Board (PCB) are listed in IPC-6011, includes:
Class 1: consumer electronic product. It refers to PCBs with limited lifespan and simple functionality, like PCBs used in remote controllers.
Class 2: dedicated service electronic product. It refers to PCBs have a longer lifespan and are used in products like laptops, TV and air conditioners.
Class 3: high-performance electronic product. It refers to PCBs with continuous high performance or they are essential critically, that product downtime is un-acceptable, and the usage environment may be extremely harsh. These Printed Circuit Boards (PCBs) must have high reliability requirements and are used in military or medical fields.

Compared to Class 1 and Class 2, Class 3 has the strictest tolerance and performance requirements. In addition, a new category level, Class 3/A is mentioned in IPC-6012, which includes space and military aerospace electronic equipment. This represents the highest level of the Printed Circuit Board (PCB) classification. The specification and requirements for Class 1, 2, 3 and 3/A are detailed in the IPC-6012 Rigid Printed Circuit Board (RPCB) performance specification.

Quality requirements for IPC Class 1, 2, 3, and 3/A:

Class1：Consumer Electronic Product
Class 1 Printed Circuit Board (PCB): It refers to PCBs with limited lifespan and simple functionality. This category of product includes the daily necessities, where various cosmetic defects are allowed as long as they do not affect the functionality of the Printed Circuit Board (PCB). In these types of PCBs, product reliability is not a critical factor. For example, TV remote controllers, LED lights and toys…etc. They are the lowest-cost PCBs in the industry and have a limited lifespan.

Class2：Dedicated Service Electronic Product
Class 2 Printed Circuit Board (PCB) has higher reliability and longer lifespan requirements. Compared to Class 1 product, Class 2 has stricter standards while allowing for some cosmetic defects. Continuous operation is necessary but not critical, since Class 2 products are not exposed to extreme environment conditions. Such products include laptops, smartphones, tablets and other communication devices.

Class3：High-performance Electronic Product
Class 3 Printed Circuit Board (PCB) must provide continuous or on-demand performance. Equipment downtime is not allowed since these PCBs may be exposed to the extremely harsh operating environment. These PCBs undergo high-level inspection and testing according to the strict standards to ensure the stable reliability and dependability. Such products include life support systems, military equipment, electronic monitor system, automotive PCBs and other essential application.

IPC–6012 3/A Product
IPC-6012 3/A is a relatively new level which includes space station and military aerospace equipment. It represents the highest level of the Printed Circuit Board (PCB) classification. The production standards for Class 3/A Printed Circuit Boards (PCBs) are extremely strict because they must operate under critical conditions like outer space. Compared to other levels, the manufacturing cost for Class 3/A Printed Circuit Boards (PCBs) is very high due to their near-perfect requirements. These products are used in aviation, aerospace, military aircraft systems and missile systems. (Source: IPC-6012 Qualification and Performance Specification for Rigid Printed Circuit Board (RPCB).