IPC-CH-65 Standard: What Engineers Need to Know About PCB Assembly Cleaning

If you’ve been in electronics manufacturing long enough, you’ve probably heard someone say “it’s no-clean flux, so we don’t need to clean it.” That statement has caused more field failures than I care to count. The truth about PCB cleaning is more nuanced, and that’s exactly why IPC-CH-65 exists.

IPC-CH-65 is the industry’s comprehensive guideline for cleaning printed boards and assemblies. Whether you’re dealing with lead-free solder residues, trying to figure out if you really need to clean that no-clean flux, or setting up a cleaning line for Class 3 aerospace assemblies, this standard has the answers. Let me walk you through what’s inside and how to apply it.

What is IPC-CH-65?

IPC-CH-65, officially titled “Guidelines for Cleaning of Printed Boards and Assemblies,” is a 200-page document that consolidates everything the electronics industry knows about cleaning PCBs and electronic assemblies. The current version, IPC-CH-65B, was released in July 2011 and represents a major overhaul of earlier cleaning guidance.

What makes IPC-CH-65B significant is that it replaced and consolidated five separate IPC documents into one comprehensive resource:

Before IPC-CH-65B, engineers had to reference multiple documents to piece together a complete cleaning strategy. Now everything lives in one place, updated for modern challenges like lead-free soldering, no-clean flux residues, and environmental regulations.

Why PCB Cleaning Matters More Than Ever

The electronics industry went through a major shift in the 1990s when no-clean fluxes became popular. Many manufacturers concluded that cleaning was no longer necessary. That conclusion turned out to be dangerously oversimplified.

Several trends have made cleaning more important, not less:

Tighter Component Spacing

Modern PCBs pack components closer together than ever before. QFN packages, BGAs, and 0201 chip components create tight spaces where flux residues can become trapped. These residues may look harmless, but under the right conditions they become reliability killers.

Higher Reflow Temperatures

The transition to lead-free soldering pushed reflow temperatures significantly higher. This changes the character of flux residues. Higher temperatures can partially activate flux that was designed to remain benign, creating residues that are harder to clean and more likely to cause problems.

Increased Reliability Demands

Products that once would have been Class 1 consumer electronics are now expected to last years in demanding environments. Automotive electronics, medical devices, and IoT products all face stricter reliability requirements than their predecessors.

Conformal Coating Adhesion

Many assemblies require conformal coating for environmental protection. Flux residues, even from no-clean formulations, can prevent proper coating adhesion. The coating may look fine initially but will delaminate over time, leaving components exposed to moisture and contaminants.

Types of Contamination Covered in IPC-CH-65

IPC-CH-65 addresses the full spectrum of contamination that can affect PCB reliability. Understanding these contamination types helps you select the right cleaning approach.

Ionic Contamination

Ionic contamination consists of charged particles that can conduct electricity when moisture is present. Sources include:

• Flux activators and residues
• Plating bath chemicals
• Etchant residues
• Fingerprint oils and salts
• Environmental deposits

Ionic contamination is particularly dangerous because it enables electrochemical migration (ECM) and dendritic growth. Under bias voltage and humidity, metal ions can migrate across insulating surfaces, eventually forming conductive dendrites that short adjacent traces.

The accepted limit for ionic contamination on bare boards is typically less than 1.56 µg/cm² sodium chloride equivalent. For assembled boards, limits may vary based on the application class and customer requirements.

Non-Ionic Contamination

Non-ionic residues don’t conduct electricity but can still cause problems:

• Oils and greases
• Resin from flux
• Dust and particulates
• Mold release agents
• Adhesive residues

These contaminants can interfere with conformal coating adhesion, trap ionic materials against the board surface, and create visual defects that complicate inspection.

White Residue

White residue formation is one of the most common post-soldering defects and gets dedicated attention in IPC-CH-65. This hazy or powdery deposit typically results from:

• Incomplete flux activation during reflow
• Moisture absorption by flux residues
• Chemical reactions between cleaning agents and flux
• Outgassing from substrates

White residue is often cosmetically objectionable even when it doesn’t affect reliability, but it can also indicate underlying cleanliness problems that require investigation.

The No-Clean Flux Debate

Perhaps no topic in PCB cleaning generates more confusion than no-clean flux. IPC-CH-65 directly addresses this issue, and the guidance might surprise you.

What “No-Clean” Actually Means

No-clean flux is formulated to leave minimal residue that, under ideal conditions, won’t require removal. The residues are designed to be non-conductive and non-corrosive after the soldering process converts them to a benign state.

However, “no-clean” doesn’t mean “never clean.” It means cleaning may not be required under certain conditions. When those conditions aren’t met, cleaning becomes essential.

When You Should Clean No-Clean Flux

IPC-CH-65 and industry experience point to several scenarios where cleaning no-clean residues is necessary:

The Hidden Risk of Partial Cleaning

One critical point from IPC-CH-65: if you’re going to clean no-clean flux, you must clean it completely. Partially removed residues are often worse than residues left in place. The cleaning process can redistribute ionic materials, leaving concentrated contamination in the hardest-to-reach areas.

Cleaning Methods and Equipment

IPC-CH-65 covers the full range of cleaning technologies available to electronics manufacturers. The right choice depends on your contamination type, board design, volume requirements, and budget.

Aqueous Cleaning

Water-based cleaning has become the dominant method for most PCB applications. Aqueous cleaners use surfactants, saponifiers, and other additives to dissolve and remove flux residues.

Advantages:

• Environmentally friendly compared to solvents
• Effective on water-soluble and many no-clean fluxes
• Lower chemical costs
• Easier waste treatment

Considerations:

• Requires thorough rinsing to remove cleaning agent residues
• Must ensure complete drying to prevent moisture-related issues
• May not be effective on all flux types without proper chemistry matching

Solvent Cleaning

Solvent-based cleaning remains important for specific applications, particularly where aqueous methods are ineffective or where components are moisture-sensitive.

Common solvent types:

• Isopropyl alcohol (IPA) – widely available but limited effectiveness
• Engineered flux removers – formulated for specific flux types
• Modified alcohols – enhanced cleaning power
• Vapor degreasing solvents – for specialized applications

Batch vs. Inline Equipment

IPC-CH-65 discusses both batch and inline cleaning approaches. The choice typically depends on production volume and process requirements.

Batch systems seal boards in a chamber for wash, rinse, and dry cycles. They’re ideal for job shops and mixed-production environments. Inline systems move boards on a conveyor through sequential cleaning stages, maximizing throughput for high-volume production.

Ultrasonic Cleaning

Ultrasonic cleaning uses high-frequency sound waves to create cavitation in the cleaning fluid. The imploding bubbles generate mechanical energy that dislodges contamination from surfaces and under components.

Modern ultrasonic systems use sweeping frequencies (typically 40, 80, or 120 kHz) and controlled power density to clean effectively without damaging sensitive components like wire bonds or MEMS devices.

Stencil Cleaning

While not directly a PCB cleaning topic, IPC-CH-65 recognizes that stencil cleanliness directly impacts assembly quality. Solder paste residue on stencils causes printing defects that result in contamination on finished assemblies. The standard addresses stencil cleaning as part of a comprehensive cleanliness strategy.

Proper stencil cleaning prevents:

• Blocked apertures causing solder insufficiency
• Paste smearing causing bridges
• Contamination transfer to board surfaces
• Inconsistent paste deposit volumes

Many facilities use dedicated stencil cleaning equipment with either aqueous chemistries or specialized solvents, complementing under-stencil wiping during production runs.

Cleanliness Testing Methods

IPC-CH-65 emphasizes that cleaning without verification is incomplete. You need to confirm that your process actually achieves the required cleanliness level.

Visual Inspection

The simplest form of cleanliness verification. IPC recommends magnification up to 20X for routine inspection, with 40X as the “referee” magnification for disputes. Visual inspection can catch obvious residues but cannot detect ionic contamination.

ROSE Testing (Resistivity of Solvent Extract)

ROSE testing, defined in IPC-TM-650 Method 2.3.25, measures bulk ionic contamination by extracting residues into a solvent and measuring the resulting conductivity change.

Process overview:

1. Immerse PCB in 75% IPA / 25% deionized water solution
2. Allow extraction time (typically 5-10 minutes)
3. Measure resistivity or conductivity change
4. Calculate contamination level in µg/cm² NaCl equivalent

Limitations:

• Measures total ionic contamination only
• Cannot identify specific contaminants
• Averages contamination across entire board surface
• May miss localized contamination under components

Ion Chromatography

Ion chromatography (IC), covered in IPC-TM-650 Method 2.3.28, provides detailed analysis of specific ionic species present on the board. It’s more expensive than ROSE testing but provides actionable data for troubleshooting contamination sources.

Surface Insulation Resistance (SIR)

SIR testing measures the actual electrical resistance between conductors under accelerated conditions (typically 85°C/85% RH with bias voltage). This test reveals how residues behave under realistic operating stress and is the gold standard for qualifying cleaning processes for high-reliability applications.

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

Environmental and Regulatory Considerations

IPC-CH-65 doesn’t just cover technical cleaning aspects. It also addresses environmental regulations that affect cleaning operations, a topic that has become increasingly important as environmental compliance becomes more complex.

The Shift Away from Ozone-Depleting Substances

The electronics industry once relied heavily on CFC-based solvents for cleaning. Environmental regulations eliminated these options, driving the transition to aqueous and alternative solvent cleaning. IPC-CH-65B reflects this evolution and provides guidance on selecting environmentally compliant cleaning chemistries.

VOC Regulations

Volatile organic compound (VOC) regulations vary by region and continue to tighten. California’s CARB regulations are among the strictest, but similar requirements exist in Europe and other jurisdictions. IPC-CH-65 helps engineers understand how these regulations affect cleaning agent selection and provides guidance on compliant alternatives.

Wastewater Management

Aqueous cleaning generates wastewater that may contain dissolved metals, cleaning agents, and flux residues. Proper treatment and disposal are essential for regulatory compliance. The standard discusses wastewater considerations and the importance of understanding local discharge requirements before implementing aqueous cleaning processes.

Implementing IPC-CH-65 in Your Process

Reading the standard is one thing. Implementing it effectively requires a systematic approach.

Step 1: Characterize Your Contamination

Before selecting cleaning methods, understand what you’re trying to remove. Different flux types, solder alloys, and board finishes create different residues. Work with your materials suppliers to understand residue characteristics and recommended cleaning approaches.

Step 2: Match Chemistry to Contamination

IPC-CH-65 emphasizes that no single cleaning chemistry works for all situations. Water-soluble flux requires different treatment than rosin-based or no-clean formulations. Verify compatibility between your cleaning agent and all board materials, components, and markings.

Step 3: Establish Process Parameters

Key parameters include:

• Wash temperature
• Chemical concentration
• Wash time
• Rinse quality (conductivity of final rinse water)
• Drying temperature and time

Document your process parameters and establish control limits. Small variations can significantly impact cleaning effectiveness.

Step 4: Validate and Monitor

Use cleanliness testing to validate that your process achieves required cleanliness levels. Establish ongoing monitoring to catch process drift before it causes quality problems. IPC-CH-65 provides guidance on setting up a quality assurance program for cleaning operations.

Resources for Purchasing IPC-CH-65

Here are authoritative sources for obtaining IPC-CH-65B and related documents:

Approximate Pricing

• IPC-CH-65B (PDF): €200-250 depending on vendor
• Print versions and site licenses available at higher price points

Related Documents

• IPC-TM-650 Method 2.3.25 (ROSE Testing)
• IPC-TM-650 Method 2.3.28 (Ion Chromatography)
• J-STD-004 (Flux Requirements)
• IPC-A-610 (Acceptability of Electronic Assemblies)

Frequently Asked Questions About IPC-CH-65

Is IPC-CH-65 a mandatory standard?

IPC-CH-65 is a guideline, not a specification with mandatory requirements. However, many customers and industry standards reference it, making compliance effectively required for certain applications. Military and aerospace programs often invoke IPC-CH-65 as part of their quality requirements.

Does IPC-CH-65 specify cleanliness limits?

IPC-CH-65 provides guidance on cleanliness testing methods and discusses typical acceptance levels, but it doesn’t mandate specific limits. Cleanliness requirements are typically established by the end customer based on the application’s reliability needs. Common limits reference 1.56 µg/cm² NaCl equivalent for bare boards and may vary for assembled product.

How often is IPC-CH-65 updated?

The current version (IPC-CH-65B) was released in 2011. IPC standards are typically reviewed and updated every 5-7 years, but updates depend on technology changes and industry input. Check the IPC website for information on any revision activity.

Can I clean lead-free assemblies with the same process as leaded?

Not necessarily. Lead-free soldering typically requires higher reflow temperatures, which changes flux residue characteristics. IPC-CH-65B specifically addresses lead-free cleaning challenges and notes that processes validated for tin-lead assemblies may not be adequate for lead-free. Validate your cleaning process for each solder alloy you use.

What’s the difference between IPC-CH-65 and J-STD-001 regarding cleaning?

J-STD-001 is the requirements document for soldered electrical and electronic assemblies. It specifies when cleaning is required and references cleanliness criteria. IPC-CH-65 provides the detailed guidance on how to clean and verify cleanliness. The two documents work together, with J-STD-001 setting requirements and IPC-CH-65 providing implementation guidance.

Final Thoughts

PCB cleaning isn’t glamorous, but it’s one of those process steps that separates reliable products from field failures. IPC-CH-65 represents decades of accumulated industry knowledge about what works, what doesn’t, and why.

The standard’s comprehensive approach, covering everything from contamination science to equipment selection to process validation, makes it an essential reference for anyone responsible for electronics manufacturing quality. Even if your current products don’t require aggressive cleaning, understanding IPC-CH-65 prepares you for when requirements change or new products demand higher reliability.

The bottom line: don’t assume “no-clean” means “never clean,” and don’t assume your cleaning process is effective just because it’s been running for years. Use IPC-CH-65 to build a science-based approach to cleanliness, and verify your results with appropriate testing. Your customers and your field failure rates will thank you.