IPC Design Guide

High-reliability PCBs for the aerospace and military industries

Which class of board do I choose? IPC class 2 or IPC class 3 standard? Does it really make any difference? Are manufacturers solely responisble for the board quality? Do designers play any role in it?

If you have all these questions on your mind then this design guide will help you clear up that ambiguity.

PCB designers often wonder about the differences between the IPC classes. It is always the end application of the product that determines the type of board to be used in that particular design.

When we talk about IPC classes, like class 1, class 2, and class 3, we are speaking about the level of inspection that defines the manufactured board’s precision and reliability. The three classes are categorized based on the criticality of the application, the tolerances to the harsh environment, and so on.

In short, the three classes determine the quality of the board. With IPC class 3 being the highest in quality and class 1 being the lowest. The other important thing that we would like to state here is that we cannot explain just about IPC class 3 without understanding the other two classes. Hence, in this design guide, we mention class 1 and class 2 for your better understanding.

See What’s Inside


8 Chapters

24 Pages

500+ Downloads



1. Introduction

2. What is IPC?

3. Class 1, Class 2, and Class 3 PCBs

4. IPC Guidelines for Manufacturing Defects

    4.1 IPC Standards for Annular Ring
    4.2 Design Rules for Annular Rings

5. IPC Standards for Assembly Process

    5.1 IPC Standards for Solder Joints

6. Common Differences Between IPC Classes

7. PCB Cross-Section Verification

8. IPC Documents to Set the Level of Acceptance Criteria


About Us

Sierra Circuits has been faithfully serving PCB designers and engineers since 1986, and has worked with over 20,000 customers since then. We specialize in PCB design, manufacturing and assembly and High-Density Interconnect technology. From PCB layout and design to assembly and manufacturing, Sierra Circuits handles all aspects of PCB production. We provide our customers with unprecedented quality, reliability, and a single point of support.



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