IPC-9201 SIR Handbook – Overview, Test Procedures & Requirements

If you’ve ever dealt with field failures caused by dendrite growth or mysterious shorts on your PCB assemblies, you already know how critical Surface Insulation Resistance (SIR) testing is. The IPC-9201 standard is the go-to handbook that covers everything you need to understand about SIR testing—from the fundamentals to troubleshooting real-world failures.

In this guide, I’ll walk you through what IPC-9201 covers, why it matters for your manufacturing process, and how to apply it effectively. Whether you’re qualifying a new flux, validating a cleaning process, or investigating a customer return, this handbook is essential reading.

What is IPC-9201?

IPC-9201, officially titled the “Surface Insulation Resistance Handbook,” is a comprehensive document published by IPC (Association Connecting Electronics Industries). The current version is Revision A, released in September 2007, containing 86 pages of detailed guidance on SIR testing methodology.

The handbook covers the terminology, theories, test procedures, and test vehicles used for SIR testing. It addresses both Temperature-Humidity (TH) and Temperature-Humidity-Bias (THB) testing methods, along with discussions on failure modes and troubleshooting strategies.

Unlike prescriptive standards that simply tell you what values to hit, IPC-9201 focuses on understanding SIR testing—the science behind it, the variables that affect results, and how to interpret what you’re seeing.

IPC-9201 Document Overview

Why SIR Testing Matters for PCB Reliability

Every electronic assembly goes through numerous chemical, thermal, and mechanical processes during manufacturing—often more than 20 chemical steps alone. Soldering fluxes, cleaning agents, solder masks, and conformal coatings all leave residues that can affect long-term reliability.

SIR testing measures the electrical resistance across circuit traces to detect ionic contamination and predict electrochemical behavior under stress conditions. Low SIR values indicate a higher likelihood of corrosion or electrochemical migration (ECM)—the very failure mechanisms that can cause field returns years down the road.

Common Failure Mechanisms Detected by SIR Testing

SIR testing helps identify several critical failure modes:

Electrochemical Migration (ECM): Under applied voltage and humidity, metal ions migrate between isolated conductors, forming conductive dendrites that cause shorts. Studies show ECM can reduce SIR from a safe level of over 10⁹ ohms to a dangerous 10⁶ ohms or lower in just a few hundred hours under accelerated conditions.

Conductive Anodic Filament (CAF) Formation: This occurs when copper salts grow along glass fibers in the PCB substrate material, creating internal short circuits that are nearly impossible to detect visually.

Electrolytic Corrosion: Moisture combined with ionic contamination creates an electrolyte that attacks copper traces, eventually leading to open circuits or degraded signal integrity.

IPC-9201 Key Sections and Contents

The handbook is organized into logical sections that build from fundamentals to practical application. Here’s what you’ll find:

Section 1: Introduction and Scope

Covers the purpose of SIR testing and when to use it. The handbook addresses temperature-humidity testing broadly, with guidance on proper testing techniques. Revision A expanded coverage to include international test specifications like IEC and ISO methods.

Section 2: Applicable Documents

References related standards including IPC-TM-650 test methods, J-STD-001, and international specifications. Understanding these cross-references helps you navigate the broader quality system.

Section 3: Surface Insulation Resistance Fundamentals

This is the meat of the handbook. It covers:

• Terminology and definitions specific to SIR testing
• Metal migration and filament formation mechanisms
• Electrochemical corrosion principles
• Basic concepts like sheet resistance and ohms per square
• Test factors affecting results (wiring, sample orientation, voltage, temperature, humidity)
• Known process effects on SIR levels from precleaning through curing

Section 4: Assessment of SIR Test Methods

Explains different test approaches including cyclical test environments and harsh static environments. Understanding when to use each approach is critical for getting meaningful data.

Section 5-7: Practical Application

Covers incoming inspection procedures, process qualification methods, and determining acceptance criteria. This is where theory meets practice.

Section 8: Recommendations for Prevention of SIR Failures

Perhaps the most valuable section for troubleshooting. Covers typical SIR failures, contingencies, and practical recommendations based on decades of industry experience.

Section 9: Testing Non-PWB Materials

Extends SIR testing concepts to alternative substrates, integrated circuits, and multi-chip modules.

IPC-9201 Test Vehicles and Equipment

One challenge with SIR testing has always been correlating test coupon results to actual production assemblies. IPC-9201 addresses this by discussing available test vehicles and their appropriate applications.

Standard IPC Test Vehicles Covered in IPC-9201

The IPC-B-52 deserves special attention because it addresses a major shortcoming of earlier test vehicles—the lack of components that act as entrapment sites for flux residues. Real assemblies trap contaminants under QFPs, BGAs, and connectors. A bare test coupon simply doesn’t replicate these conditions.

Typical SIR Test Conditions

Most SIR testing follows standardized environmental conditions:

How IPC-9201 Relates to Other IPC Standards

IPC-9201 doesn’t exist in isolation. It works alongside several related documents that together form a complete SIR testing framework.

IPC-9201 vs. IPC-9202 vs. IPC-9203

If you’re new to SIR testing, start with IPC-9201 to understand the fundamentals. Once you’re ready to implement testing, IPC-9202 and IPC-9203 provide the specific protocols and guidance for using the IPC-B-52 test vehicle.

Related IPC Test Methods (IPC-TM-650)

• IPC-TM-650 2.6.3.7 – Surface Insulation Resistance (primary SIR method)
• IPC-TM-650 2.6.3.3 – Surface Insulation Resistance for Fluxes
• IPC-TM-650 2.6.14.1 – Electrochemical Migration Resistance
• IPC-TM-650 2.3.28 – Ion Chromatography

Read more IPC Standards:

IPC Standards Explained: A Comprehensive Guide to PCB & Electronics Assembly Standards

IPC 2615 Standard Explained: PCB Dimensioning & Tolerancing Requirements

MIL-STD-2000A: Military Soldering Standards for Electronic Assemblies

MIL-STD-1686: ESD Control Program Requirements for Military Electronics

IPC 1791 Standard: Everything You Need to Know About Trusted PCB Certification

MIL-STD-883: Complete Guide to Microelectronics Test Methods

J-STD-048 Explained: Complete Guide to Product Discontinuance Notifications

MIL-STD-750: Semiconductor Device Test Methods Explained

MIL-STD-454: General Requirements for Military Electronic Equipment

IPC 9194: Complete Guide to SPC for PCB Assembly Manufacturing

MIL-STD-202: Electronic Component Testing Methods & Procedures

IPC 4110: Complete Guide to Cellulose Paper Specs for Printed Circuit Boards

Boundary Scan Testing (JTAG) in PCB Design: A Complete DFT Guide

Axiomtek IPC-950 Review: Specs, Features & Performance [2026 Guide]

MIL-PRF-55681: Military Ceramic Chip Capacitor Specification Guide

Practical Tips for Implementing IPC-9201

After working with SIR testing for years, here are some practical insights that go beyond what’s written in the standard:

Test Chamber Setup

Your environmental chamber is critical. Small variations in temperature and humidity distribution can create dramatically different results across test coupons. IPC-9201 Revision A significantly expanded the discussion on test chamber setup—pay attention to this section.

Calibrate your chamber regularly and verify conditions at multiple points. A 2-3% RH variation might seem minor but can be the difference between a passing and failing result near the acceptance threshold.

Sample Preparation

How you handle coupons before testing matters. Fingerprints contain salts and acids that absolutely destroy SIR values. Always use gloves, and consider a controlled cleaning step before testing even “as-received” samples.

Interpreting Results

A sudden drop in SIR during testing doesn’t automatically mean failure. Watch for recovery—sometimes resistance dips during initial exposure as the board acclimates, then recovers. The 24-hour grace period mentioned in many test protocols accounts for this behavior.

Visual inspection after testing is essential. Dendrite formation, discoloration, or white residue deposits tell you as much as the electrical data.

Process Qualification Approach

When qualifying a new assembly process or material set, don’t just run one batch of coupons. Run your production materials through multiple reflow cycles, different cleaning scenarios, and various storage conditions before final SIR testing. This reveals interactions you’d never catch with simple material screening.

Where to Get IPC-9201 and Related Resources

Official Sources for IPC-9201

Related IPC Standards to Consider

Test Equipment and Consumables

Several manufacturers offer SIR testing equipment and IPC-compliant test vehicles:

• GEN3 Systems – AutoSIR automated testing systems
• Topline – IPC-B-24, B-25, B-52 compatible test boards and kits
• Magnalytix – Custom and standard SIR test vehicles with testing services

IPC-9201 Frequently Asked Questions

What is the difference between IPC-9201 and IPC-9202?

IPC-9201 is an educational handbook covering SIR testing theory, terminology, and general procedures. IPC-9202 is a specific test protocol that defines how to perform material and process characterization testing using the IPC-B-52 test vehicle. Think of IPC-9201 as the textbook and IPC-9202 as the lab manual.

What is the minimum acceptable SIR value per IPC standards?

The commonly referenced minimum is 10⁸ Ω (100 megohms) per IEC 61189-5-502. However, IPC-9201 emphasizes that appropriate limits depend on application requirements. Consumer electronics may have different acceptable levels than medical devices or aerospace assemblies.

How long should SIR testing run?

Standard test durations range from 168 hours (7 days) to 504 hours (21 days) depending on the test method and application. The 168-hour test at 40°C/90% RH with 5V bias is common for process qualification. More demanding applications may require the 504-hour test or elevated 85°C conditions.

Can I use IPC-B-24 coupons for process qualification?

IPC-B-24 is acceptable for flux and solder paste screening but has significant limitations for process qualification. It lacks components, through-holes, and solder mask representative of production assemblies. For comprehensive process qualification, the IPC-B-52 test vehicle is strongly recommended because it better represents actual manufacturing conditions.

What causes sudden SIR drops during testing?

Common causes include ionic contamination from flux residues, inadequate cleaning, moisture absorption by hygroscopic materials, or electrochemical migration initiating dendrite growth. IPC-9201 Section 8 provides detailed troubleshooting guidance for various failure scenarios. Visual inspection after testing often reveals the root cause.

Conclusion

IPC-9201 remains the foundational resource for understanding Surface Insulation Resistance testing in electronics manufacturing. Whether you’re dealing with field failures, qualifying new materials, or establishing incoming inspection criteria, the principles in this handbook apply.

The investment in understanding SIR testing pays dividends in reduced field failures, more robust manufacturing processes, and fewer customer returns. Combined with IPC-9202 and IPC-9203 for implementation guidance, IPC-9201 gives you the complete toolkit for electrochemical reliability testing.

If you’re seeing unexplained failures in humid environments or want to proactively validate your assembly process, SIR testing per IPC-9201 methodology should be part of your quality program. The cost of testing is trivial compared to a field recall or loss of customer confidence.