IPC-5704: Ion Chromatography Limits for Bare Board Cleanliness

For years, the electronics industry relied on ROSE testing and legacy military specifications to judge whether bare boards were clean enough. The problem? Those methods only measured total ionic contamination as a sodium chloride equivalent. They couldn’t tell you which specific ions were present or whether your boards would actually survive in the field.

IPC-5704 changed that. Released in December 2009, this standard introduced specific ionic contamination limits based on ion chromatography testing. Instead of a single pass/fail number, IPC-5704 breaks down contamination into individual anions and cations, each with its own limit. This gives engineers real data about what’s actually on their boards.

What is IPC-5704?

IPC-5704, officially titled “Cleanliness Requirements for Unpopulated Printed Boards,” defines the recommended cleanliness requirements for bare single-sided, double-sided, and multilayer printed circuit boards. The standard is only 6 pages, but those pages contain the specific ionic limits that have been missing from the industry for decades.

The cleanliness provisions in IPC-5704 were adapted from Delphi Automotive’s C-7000 specification. Delphi had been using ion chromatography criteria for bare boards in automotive applications for 10-15 years before IPC adopted them. Other industry IC experts reviewed those criteria and agreed they represented reasonable starting points for the broader electronics industry.

Why IPC-5704 Matters for Modern PCB Reliability

As conductor widths and spacing continue to shrink, ionic contamination that was acceptable on older designs becomes increasingly problematic. Contamination that might have taken years to cause a failure on boards with 10-mil spacing can cause failures in months or weeks on boards with 3-mil spacing.

The Electrochemical Migration Problem

Ionic contamination enables electrochemical migration (ECM), a failure mechanism where metal ions dissolve at the anode and migrate toward the cathode under the influence of an electric field. This migration creates dendritic growths that can eventually bridge adjacent conductors and cause shorts.

Three conditions are required for ECM:

With tighter geometries, the distance dendrites must travel to cause a short decreases. What was once a non-issue becomes a reliability risk.

Limitations of Legacy Cleanliness Standards

Many assemblers still reference military specifications from 30+ years ago. The commonly cited limit of 1.56 µg/cm² NaCl equivalent was established when conductor spacing was much larger than today’s designs require.

More importantly, ROSE testing (Resistivity of Solvent Extract) and similar methods have fundamental limitations:

IPC-5704 addresses these limitations by requiring ion chromatography testing with specific limits for each ionic species.

Understanding Ion Chromatography Testing

Ion chromatography (IC) is an analytical technique that separates, identifies, and quantifies individual ionic species in a sample. For PCB cleanliness testing, the process works as follows:

The IC Testing Process

1. Extraction: The board surface is washed with a solvent (typically deionized water with isopropyl alcohol) to dissolve ionic residues
2. Separation: The extract is injected into the ion chromatograph, where different ions are separated based on their charge and size
3. Detection: A conductivity detector measures each ion as it elutes from the column
4. Quantification: Peak areas are compared to calibration standards to determine concentration

The test method referenced in IPC-5704 is IPC-TM-650 Method 2.3.28.2, “Bare Printed Board Cleanliness by Ion Chromatography.”

Ions Measured by IC Testing

Ion chromatography can detect and quantify a wide range of ionic species. The ions commonly analyzed for PCB cleanliness include:

Additionally, weak organic acids (WOAs) from flux residues can be analyzed. Common WOAs include adipic, acetic, citric, formic, maleic, and succinic acids.

IPC-5704 Ionic Contamination Limits

The core value of IPC-5704 lies in its specific ionic limits. Rather than a single total contamination number, the standard provides individual limits for each ionic species known to contribute to electrochemical failures.

Anion Limits per IPC-5704

Cation Limits per IPC-5704

Why These Specific Ions Matter

Not all ionic contamination is equally harmful. The ions targeted by IPC-5704 are specifically those known to contribute to electrochemical failures:

Chloride and Bromide: These halides are the most aggressive contributors to corrosion and electrochemical migration. Even small amounts can cause significant reliability problems, which is why their limits are set relatively low at 0.75 µg/cm².

Sulfate: While less aggressive than halides, sulfate can still participate in electrochemical reactions and is commonly found as a residue from plating chemistry.

Sodium and Potassium: These alkali metal ions are hygroscopic, meaning they attract moisture from the environment. Their presence increases the likelihood of creating the electrolyte needed for ECM.

Ammonium: Often present as a residue from alkaline etchants, ammonium can be a marker for inadequate rinsing in fabrication.

IPC-5704 vs ROSE Testing: Key Differences

Understanding how IPC-5704 testing differs from traditional ROSE testing helps explain why the newer standard provides better reliability assurance.

When ROSE Testing Falls Short

ROSE testing can pass boards that would fail IPC-5704 testing because it cannot distinguish between ionic species. A board might have low total ionics but elevated chloride levels that pose a reliability risk. ROSE testing would miss this; IPC-5704 testing would catch it.

Conversely, IPC-5704 provides troubleshooting capability that ROSE cannot. When boards fail, ion chromatography tells you exactly which ions are elevated, pointing directly to the source of contamination in your process.

IPC-5704’s Role in Nonconformance Resolution

The standard specifically states that ion chromatography testing shall be used to disposition nonconformances derived from standard testing methods. This means that when ROSE testing produces questionable results, IC testing per IPC-5704 becomes the referee.

Implementing IPC-5704 in Your Quality Program

Adopting IPC-5704 requires changes to testing procedures, supplier requirements, and potentially incoming inspection practices.

Step 1: Establish Testing Capability

You have three options for obtaining IC testing capability:

For high-volume operations with critical cleanliness requirements, in-house capability often makes sense. For lower volumes or less critical applications, contract laboratories can provide the necessary testing without capital investment.

Step 2: Define Acceptance Criteria

IPC-5704 provides recommended limits, but you may need to adjust these based on your specific applications. Factors to consider:

• End-use environment (humidity, temperature, contamination exposure)
• Service life requirements
• Conductor spacing and geometry
• Conformal coating or other protection

Some applications may require tighter limits than IPC-5704 specifies. Medical devices, aerospace systems, and automotive safety systems often demand ultra-clean boards.

Step 3: Specify Requirements to Suppliers

Update your purchasing documents to reference IPC-5704 requirements. Per IPC-5701 guidance, your specifications should include:

• Reference to IPC-5704 cleanliness limits
• Required test method (IPC-TM-650 Method 2.3.28.2)
• Sample size and testing frequency
• Documentation requirements
• Nonconformance resolution procedures

Step 4: Establish Incoming Inspection Protocol

Decide whether you will test incoming boards yourself or rely on supplier certifications. Many companies use a combination:

• Initial qualification: Full IC testing of new suppliers
• Ongoing monitoring: Periodic IC testing to verify continued compliance
• Supplier certification: Accept supplier test reports for routine shipments

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

Challenges with IPC-5704 Adoption

Despite its technical advantages, IPC-5704 has not achieved widespread adoption. Understanding these challenges helps set realistic expectations.

Cost Barriers

Ion chromatography equipment costs significantly more than ROSE testers. A basic ROSE tester might cost $5,000-15,000, while IC equipment suitable for IPC-5704 testing costs $50,000-150,000. Contract testing costs $50-200 per sample, making extensive testing expensive.

Industry Inertia

Many companies have used ROSE testing for decades and have established processes around those results. Switching to IPC-5704 requires new procedures, training, and potentially renegotiation with suppliers.

Lack of Awareness

The standard was released in 2009 but remains unknown to many engineers. Companies continue specifying outdated military standards or generic ROSE limits simply because they’re unaware of the alternative.

Surface Finish Considerations

IPC-5704 testing is considered non-destructive for most surface finishes but will impact boards coated with organic solderability preservatives (OSPs). Tested boards with OSP should be baked to remove moisture following extraction.

IPC-5704 and Related Bare Board Cleanliness Standards

IPC-5704 is part of a family of documents addressing bare board cleanliness. Each serves a different purpose in the overall cleanliness control ecosystem.

How the Standards Work Together

Think of these standards as complementary pieces:

• IPC-5702 helps you determine how clean your boards need to be based on application requirements
• IPC-5701 helps you communicate those requirements to suppliers
• IPC-5703 helps fabricators control their processes to meet requirements
• IPC-5704 provides the specific limits and test methods for verification

For a complete cleanliness program, all four documents provide valuable guidance.

Where to Purchase IPC-5704

When purchasing IPC-5704, also consider obtaining the companion test method IPC-TM-650 Method 2.3.28.2, which provides detailed procedures for performing the ion chromatography testing.

Frequently Asked Questions About IPC-5704

What is the main difference between IPC-5704 and ROSE testing?

IPC-5704 uses ion chromatography to measure individual ionic species (chloride, bromide, sulfate, etc.) with specific limits for each. ROSE testing measures only total ionic contamination reported as a sodium chloride equivalent. IPC-5704 provides more detailed information about what’s actually on the board and which ions might cause reliability problems.

Why hasn’t IPC-5704 been more widely adopted?

The primary barriers are cost and inertia. Ion chromatography equipment costs significantly more than ROSE testers, and contract testing adds per-sample costs. Many companies also have established processes around ROSE testing and lack awareness of IPC-5704 as an alternative.

Can IPC-5704 testing damage my boards?

Testing is considered non-destructive for most surface finishes. However, boards with organic solderability preservatives (OSP) will be affected by the extraction process. The standard recommends baking OSP-finished boards after testing to remove absorbed moisture.

What should I do if my boards fail IPC-5704 limits?

First, identify which specific ions are elevated. This information points to the contamination source in fabrication. Common culprits include inadequate rinsing after etching (chloride), HASL flux residues (chloride, bromide), and plating chemistry (sulfate, ammonium). Work with your fabricator to address the specific process step causing the problem.

How does IPC-5704 relate to assembled board cleanliness standards?

IPC-5704 addresses only bare board cleanliness before assembly. For assembled boards, refer to IPC-CH-65 for general cleaning guidelines and J-STD-001 for assembly cleanliness requirements. Bare board cleanliness per IPC-5704 contributes to but does not guarantee assembled board cleanliness.

Best Practices for Using IPC-5704 Effectively

Start with Process Baseline

Before implementing IPC-5704 as an acceptance criterion, test your current supply base to understand where you stand. You may find that some suppliers easily meet the limits while others need process improvements.

Use IC Data for Process Improvement

When boards fail, don’t just reject them. Analyze which ions are elevated and work with fabricators to identify the source. Elevated chloride often points to etching or HASL processes. Elevated ammonium suggests alkaline etchant residues. This feedback loop improves quality over time.

Consider Application-Specific Limits

IPC-5704 limits are starting points, not absolute requirements. High-reliability applications may need tighter limits, while less critical applications might accept slightly higher levels. Use IPC-5702 guidance to determine appropriate limits for your specific applications.

Document Everything

Maintain records of IC test results for traceability. When field failures occur, this data becomes invaluable for root cause analysis and supplier corrective actions.

Conclusion

IPC-5704 represents a significant advancement in bare board cleanliness testing. By providing specific ionic limits based on ion chromatography, it gives engineers the detailed contamination data they need to ensure reliability in modern, high-density designs.

While adoption has been slower than ideal due to cost and awareness barriers, the standard offers clear advantages for applications where ionic contamination poses reliability risks. The ability to identify specific ionic species not only enables better pass/fail decisions but also provides actionable data for process improvement.

For engineers serious about board cleanliness, IPC-5704 combined with its companion documents (IPC-5701, IPC-5702, IPC-5703) provides a comprehensive framework for specifying, controlling, and verifying the cleanliness of unpopulated printed boards.