The Association Connecting Electronics Industries (IPC) publishes the industry standard for PCB manufacturing—IPC-A-610. It is a comprehensive document that outlines the criteria and requirements for the acceptability of electronic assemblies, guiding manufacturers on quality assurance and inspection processes. The standard lists three classifications of PCB manufacturing requirements: Class 1, 2, and 3.
Frequently, designers may be concerned about whether or not their boards adhere to the highest manufacturing standards. However, it’s essential to recognize that aiming for Class 2 standards may often be sufficient. IPC Class 2 PCBs balance cost-effectiveness and reliability, making them a practical choice for many electronic products.
How IPC-A-610 Class 2 Requirements Compare to Other Classes
The first step in identifying which classification your PCB needs is to understand the differences between the classes and their requirements:
| Class | Description | Manufacturing Requirements | Intended Applications | Notes |
|---|---|---|---|---|
| 1 | General electronic products | Least stringent | Toys, lower-level consumer products | Intended for inexpensive applications, does not expect product longevity, requires low assembly costs |
| 2 | Dedicated service electronic products | More rigorous | Most industrial products, consumer appliances | Intended for assemblies where extended reliability is the goal, it allows for some imperfections that are fully functional electrically and mechanically |
| 3 | High-performance electronic products | Most stringent | Military, aerospace, automotive applications, environments where the PCB experiences harsh conditions | Demands for perfection in assembly, including aesthetic appearance, come at a higher cost to meet all requirements. |
Although Class 3 requirements are necessary for aerospace applications, these boards are not exclusive to that industry. Class 3 requirements for circuit board manufacturing apply to any board used in a harsh environment where its long-term ability to function reliably is mission-critical, i.e., anywhere the PCB experiences a harsh operating environment, such as in a car’s engine compartment. Most PCBs do not require this amount of exacting specifications.
The Advantages of IPC Class 2 PCB Manufacturing
Since more PCBs fit into Class 2 manufacturing requirements, trying to build to Class 3 requirements is an unnecessary expense. Due to the relaxation of specifications, Class 2 PCBs have numerous advantages:
IPC Class 2 PCB Advantages over Class 3
| Class 3 Requirements | Class 2 Advantages | |
|---|---|---|
| Design | Boards must conform to tighter tolerances and specifications, including annular ring sizes. A minimum of 1 mil annular ring width without any breakout is required; increasing pad diameters reduces routing channels and could affect placement. | Allows for some breakout of the hole from the pad provided that the minimum lateral spacing is maintained, offering flexibility with smaller pad diameters that increase space for placement and routing. |
| Manufacturing | Processes often slowed down, causing more time and expense. Standards call for a 75% solder fill in the barrel for thru-hole leads and perfectly aligned surface mount parts. | Only a 50% solder fill in the barrel for thru-hole leads is necessary. Surface mount parts can be slightly off-center if it doesn’t impact electrical or mechanical function. |
| Inspection | Must pass more rigid requirements, increasing inspection times and additional costs. Tight tolerances on annular rings, perfectly aligned surface mount parts, and thru-hole leads filled to 75% must be inspected and verified. | Less stringent than Class 3, with allowances for slight imperfections that do not affect electrical or mechanical functionality |
Most PCBs need not conform to the highest standard—Class 3. Designers may get better overall results by building for the requirements of an IPC-A-610 Class 2 PCB instead. Consider a closer look at the differences between these three classifications and how they can affect PCB manufacturing. Class 2 requirements are the standard for most products that demand high reliability, such as network equipment, industrial electronics, and many electronic medical devices. Not only is the production line much quicker for a Class 2 board, but the requirements are well-known and easier to work with for manufacturers, which also increases the throughput of the manufacturing process.
Finding an Assembly Partner for Your IPC Class 2 PCB
Some PCB designers may confuse Class 3 requirements as necessary for a high-quality, reliable product regardless of application. The truth is that IPC Class 2 PCB requirements often meet quality and reliability needs at a significantly lower price point. Class 2 is the appropriate choice in most applications and will meet the performance expectations designers seek. Minor issues, such as slightly misaligned surface mount parts, are entirely acceptable for Class 2 boards. Often, attempting to “fix” them is unnecessary and poses too much of a risk to the integrity of the finished product.
Another important point regarding Class 2 manufacturing is that contract manufacturers with well-controlled assembly processes will produce Class 2 circuit boards built to the higher-quality levels that approach Class 3 boards, especially in their surface mount technology processes. This nuance doesn’t mean that they are building Class 3 boards; their processes are such that they exceed the standards of the Class 2 requirements.
Designers who are looking for a high level of quality require a CM who is skilled and experienced in their manufacturing processes. At VSE, we’re a team of engineers committed to building electronics for our customers and guiding them through the DFM process. We’ve produced life-changing and life-saving designs with our manufacturing partners for over forty years.
