IPC inspection guidelines

IPC Standards: Ensuring Quality in Printed Circuit Boards

The Institute for Printed Circuits (IPC) was founded in the 1950s. Since that time the name has changed to ‘IPC, the Association Connecting Electronics Industries’.  The Association aims to standardize the assembly and production requirements of electronic equipment.

The IPC has developed comprehensive guidelines for measuring the quality and manufacture of printed circuit boards (PCBs). The IPC has published a range of standards covering General Documents, Design Specifications, Material Specifications, Performance and Inspection, and Flex Assembly. While there is a range of specifications, the two primary documents are the IPC-A-600 and the IPC-6012.

IPC-A-600: The Acceptability of Printed Boards

The IPC-A-600 sets the level of acceptance criteria for each class of PCB. It compiles various PCB specifications such as the Performance and Inspection documents (the IPC-6000 series).  The guideline doesn’t set the performance level for PCBs but is a tool to inspect the mechanisms for PCBs (including internal and external mechanisms). For example, the guide identifies the acceptable condition of the connectors (e.g. gold fingers) to meet the specification requirements. It does not, however, state a required thickness for nickel or gold connectors.

IPC-6012 – Qualification and Performance Specification for Rigid Printed Boards

The IPC-6012 involves the standards performance and qualifications requirements that rigid PCBs should meet. Using this standard ensures manufacturers know the requirements to be met in the fabrication process for each class of PCB.  The standard identifies types of rigid boards, and describes the requirements of three different classes of boards.

Classes of Boards

The class is usually determined by the end use of the product.  The major differences in the classes are the degree of inspection and the level of acceptance to which the boards are inspected.  The IPC-6012 specification requires production coupons on each panel that represents the boards. The coupons are used for inspections throughout the process of manufacture and final inspection. When a coupon passes the test, it confirms that the PCB meets the specification requirements. Higher-class boards are used when the end product requires greater reliability.

Class 1:

Class 1 PCBs have lower requirements, and are designed to meet the requirements of the end-use product is simply functional. The boards are identified as having a ‘limited life’. As a specification example, Class 1 allows for three copper voids per hole in 10% of the holes.

Class 2:

In Class 2 PBCs, continued performance and uninterrupted service are considered to be desirable but not crucial. In the copper void example, the specification of IPC-6012 identifies that one void is allowable in 5% of the holes.

Class 3:

Class 3 PCBs are boards that can’t fail to perform. The class is used for functions such as medical applications, flight systems, and defense systems. In the copper example, Class 3 (and Class 3/A) allow no voids.

Testing and Certification

Manufacturers can be certified as being IPC-6012 compliant by submitting sample products and accompanying coupons to an outside laboratory. The laboratory will measure conformity and provide the manufacturer with certified test results. Regular samples will then be submitted to ensure that the manufacturer meets the specifications on an ongoing basis.