IPC-A-610 Class 3 PCB Assembly: What It Means and When You Need It

What Is IPC-A-610?

IPC-A-610, "Acceptability of Electronic Assemblies," is the world's most widely used standard for inspecting and accepting PCB assemblies. Published by IPC (the Association Connecting Electronics Industries), it defines visual and dimensional criteria for solder joints, component placement, cleanliness, and mechanical integrity.

The standard defines three product classes based on the intended application and the consequences of failure:

Key Differences: Class 2 vs Class 3

Class 3 imposes stricter acceptance criteria than Class 2 in every inspection category. The most significant differences are:

Solder Joint Acceptance Criteria

For SMT chip components, Class 3 requires a minimum solder fillet height of 25 % of the component termination height (Class 2 allows 0 % — i.e. a flat joint is acceptable). For through-hole joints, Class 3 requires 75 % minimum hole fill (Class 2 requires 50 %).

Component Placement Tolerances

Class 3 requires that SMT components remain within the land pattern with no overhang beyond 25 % of the termination width. Class 2 allows up to 50 % overhang. For fine-pitch ICs, this means Class 3 rejects boards that Class 2 would accept.

Cleanliness and Residue

Class 3 prohibits flux residue that could cause corrosion or dendritic growth in high-humidity environments. All Class 3 boards at Kingdta undergo ionic contamination testing (ROSE test or SIR test) as a standard process step.

Documentation and Traceability

Class 3 assemblies require full lot traceability: component lot numbers, solder paste lot, reflow profile records, and inspection records must be retained. Kingdta's MES (Manufacturing Execution System) captures this data automatically for every board.

When Do You Need Class 3?

Specify Class 3 when your product will be used in any of the following contexts:

• Medical devices — implantable devices, life-support equipment, diagnostic instruments
• Aerospace and defence — avionics, satellite systems, military electronics
• Automotive safety systems — ABS, airbag controllers, ADAS sensors (IATF 16949 often references IPC-A-610 Class 3)
• Industrial safety — emergency shutdown systems, process control in hazardous environments
• High-reliability commercial — servers, telecom infrastructure, power grid equipment where downtime is extremely costly

How to Specify Class 3 in Your Purchase Order

To order Class 3 assembly from Kingdta, include the following in your purchase order or assembly notes:

• "IPC-A-610 Revision [current revision] Class 3 workmanship required"
• Specify whether conformal coating is required (IPC-CC-830 Class 3)
• Specify any additional test requirements (ICT, FCT, burn-in)
• Confirm whether ionic contamination testing is required

Kingdta's IPC-A-610 Class 3 certified operators and inspectors handle all Class 3 orders. Contact our engineering team at info@kingdta.com to discuss your specific requirements before submitting your order.