IPC classes are categories defined by tens of thousands of electronics manufacturing experts to assist manufacturers in controlling PCB quality.
These classes derive meaning from globally accepted PCB standards set by the same experts.
This standardization created a bridge that connects suppliers upstream to customers, improving production efficiency and electronics quality.
So what is an IPC class? And what is the link between these classes and the acceptable standards? Read on to learn more!
What Are IPC Class Definitions?
IPC (Institute for Printed Circuits) is a trade association that standardizes electronics equipment assembly and production requirements.
Formed in 1957 by six PCB manufacturers, the association expanded later and rebranded to “Association Connecting Electronic Industries.”
But the first abbreviation (IPC) stuck. The association now has over 4000 member companies and continues formulating IPC standards for electronics.
These standards cover almost all PCB production phases (design, fabrication, and assembly).
So you can compare the end products by classifying them into these three classes.
IPC Class 1 – General Electronics Products
These electronics products feature boards with the lowest quality requirements.
Generally, the products have a short life cycle, a perfect representation of “get what you pay for.”
But low-quality boards make the electronics affordable.
So you’ll find them in low-cost, high-volume productions. Think of cheap toys like superheroes and RC cars in toy stores.
Basically, with class 1 IPC, throw reliability out the window.
Some manufacturers don’t even try to manufacture these general electronics products because they can taint their reputation.
IPC Class 2 – Dedicated Service Electronics Products
These electronic devices must provide uninterrupted service for an extended life cycle. Think of televisions, mobile phones, computers, air conditioners, and tablets.
A technician repairing a TV’s circuit board
The products are relatively expensive and would make you angry if they fail after a few months or years.
Picture your large-screen TV malfunctioning after six or nine months. You would be red-faced even if the product has a warranty.
IPC Class 3 – High Reliability/Performance Electronics Products
Top-tier electronics that must have a high degree of reliability with no equipment downtime are in this class.
Manufacturers must adhere to strict guidelines when fabricating these devices because of their importance in their application area.
Some examples include medical equipment (life support systems), military equipment (missile systems), aerospace applications, aeronautic components, automotive applications, etc.
An anesthesia machine
Although expensive to make, these devices are mission-critical and must guarantee uninterrupted service.
So they undergo a rigorous electrical testing process and probably additional testing to ensure extended service life.
Compared to the other two, these electronics have the highest level of quality.
Why Use IPC Standards?
With several IPC standards for board design, manufacturing, assembly, and inspection, they build upon one another to create varying combinations.
So depending on the mix, you can get an electronic product that falls in either of the classes above.
Complying with these standards gives several benefits, including the following.
To Enhance Product Quality and Reliability
Designing, fabricating, and assembling electronic equipment to meet these standards can help PCB manufacturers to enhance their products’ quality.
And since the standards create a reference point for comparison, manufacturers compete to outshine each other.
Ultimately, consumers reap the benefits because the standards and competition ensure they get the best products for projects.
A high-tech PCB manufacturing company
But even more importantly, the standards enable product quality consistency.
So regardless of the manufacturer or the time you get your PCB made, there will be some standards to expect.
With improved quality and minimized miscommunication, there are higher chances your board will meet the required operational standards.
So manufacturers and customers won’t have to worry about reworks or delays.
Additionally, standardization enables companies to cut resource wastage and enhance efficiency, which cuts costs.
Since IPC standards are global, adhering to them enhances communication because the customer and fabricator will speak the same language.
So you can talk about expectations while using the same terminology.
The fabricating companies will also have an easier time coordinating operations internally.
For instance, designers and engineers will use the same terminology to discuss changes and improvements.
Boost Reputation and Create New Opportunities
Adhering to internationally recognized standards gives PCB fabricators credibility.
So even if new customers know nothing about your business, there is a high chance they will trust you if you adhere to IPC standards.
Therefore, you will get new business opportunities.
IPC Standards Examples
As stated earlier, IPC standards cover almost all phases of the circuit board production process.
And they include the following.
As the standard guideline for the design process, IPC-2221 covers these aspects.
- Physical properties
- Thermal management
- Mechanical properties
- Parts list, etc.
A PCB in the design phase
And in the 2220 series, there is an IPC standard for rigid, multi-chip module laminated, and flexible circuit boards.
IPC-2222 lists the standards required for rigid organic PCBs. These standards touch on material selection, hole size, and mechanical properties.
A generic standard used to facilitate communication between a board electronic designer and fabricators.
It standardizes the format for exchanging design data between the two to ensure uniformity and consistency of the results.
IPC-4101C specifies the acceptable base materials in multilayer and rigid boards (prepreg or laminate).
Also, it covers the PCB properties and dimensions.
States the performance and qualification requirements for fabricating rigid circuit boards. Some of the specified parameters include the following.
- PCB surface finish/coating
- Structural integrity
- Conductor spacing
An ENIG gold surface finish board
States the acceptance criteria standards for all circuit board parts (acceptable, non-conforming observable conditions).
For instance, it defines how gold fingers and copper plating should appear.
IPC-A-610 is the most widely used IPC industry standard. It provides the conditions for accepting electronic assemblies.
A-620 provides the criteria for accepting wire, cable, and harness assemblies.
It does not directly link to circuit boards, so you can use it as a standalone document when buying wires.
This standard gives guidelines for testing various circuit board aspects, such as:
- Surface electrochemical migration
- Ionic cleanliness on bare PCBs
Defines the methods, materials, and other conditions for soldering high-quality joints.
These include Lead and Lead-free soldered joints. The standard also focuses on process control while stating the requirements for various electronic product types.
Design Rules for IPC PCBs
If designing a PCB, ensure you follow these IPC design rules.
- Ensure the PCB copper pads meet the required lateral spacing and tolerance specifications.
- Verify the drill holes meet the size and quality requirements. The manufacturer’s equipment should align with yours (aspect ratio).
- Check the solder mask specifications (ensure it is within the recommended tolerances). And comply with the required class.
- If designing a class 3 board, stick to the specifications stipulated in the standards.
- Go through and understand all rules and requirements for all class types.
- Ensure your manufacturer has high cleanliness standards because electronic components might not function effectively on unclean boards. Also, check whether the fabricator prioritizes quality control, such as X-ray and automatic optical inspection.
A visual measuring system inspecting a circuit board
IPC Defects in Circuit Boards
Printed circuit boards are challenging to build because of the thin layers, thin conductive tracks, electrical properties, vias, etc. So it is almost impossible to get everything 100% right.
IPC (the association) knows this challenge and incorporated some acceptable manufacturing/assembly defects.
Some are cosmetic defects, while others are visual. They include the following.
IPC standards on annular rings state factors like the condition of the central hole and ring width around the hole.
For class 1 boards, the allowed defect is a 180° ring breakout.
This breakout angle reduces to 90° for class 2 PCBs. But the acceptable annular rings in class 3 boards should be at least 0.05mm around the hole.
As expected, the acceptable annular ring defects become more stringent as you move from class 1 to class 3.
Through-hole components rarely get misaligned because the lead goes through a hole.
But SMT devices float on the solder when molten and can overhang or tombstone before the molten metal solidifies.
IPC has guidelines for this defect, which are:
- 50% or less of the termination or pad width for class 1 & 2 products
- 25% or less of the termination or pad width for class 3 products
A machine for positioning SMT components on a circuit board
The condition for class 1 products is not that strict, and some manufacturers ignore it.
But they must strictly adhere to the rules set for class 2 & 3 electronic products.
Solder joint defects usually occur if the joints don’t get enough heat when soldering.
It could be due to the soldering iron not providing enough heat. And low temperatures affect the lead pin or pad wetting.
Failed solder joints
Class 1 has no IPC specification, but classes 2 & 3 require 180° and 270°, respectively.
Where To Get IPC Standards
IPC standards are available on the IPC website, where you can search by different criteria, such as:
- Type of product
You can also access learning resources and training materials on the website for different areas of the PCB production process.
IPC sells memberships to companies, not individuals.
So you can register your company, provided it contributes to the electronics-manufacturing-industry supply chain.
And the membership fee depends on your company’s global annual revenue.
In conclusion, IPC standards define critical requirements manufacturers must follow to manufacture high-quality circuit boards.
And depending on the quality, the circuit board can fall into one of three classes.
That’s it for this article. Contact us if you need further clarification on the topic. We’ll be happy to help.