IPC-HDBK-4691 Explained: Electronics Adhesive Bonding Handbook Guide

When I first started working with adhesive bonding in electronics assembly, I made every mistake in the book. Wrong adhesive chemistry for the substrate. Insufficient cure time. Contaminated surfaces. Each failure taught me something, but I wish I’d had a comprehensive reference to consult before making those expensive errors.

IPC-HDBK-4691 is that reference. This handbook consolidates decades of industry experience into a practical guide for selecting, applying, and qualifying adhesives in electronic assembly operations. Whether you’re bonding components to PCBs, staking wire bonds, or sealing enclosures, this document provides the guidance you need to get it right the first time.

What Is IPC-HDBK-4691?

IPC-HDBK-4691, officially titled “Handbook on Adhesive Bonding in Electronic Assembly Operations,” is a guidance document published by IPC in November 2015. Unlike specifications that define pass/fail requirements, this 58-page full-color handbook teaches engineers how to select and apply adhesives effectively for electronics manufacturing.

The handbook was developed by the Electronic Assembly Adhesives Task Group (5-11c) of IPC’s Assembly & Joining Committee to address a critical industry need: practical guidance for adhesive bonding decisions that goes beyond manufacturer data sheets.

Key Characteristics of IPC-HDBK-4691

Attribute	Details
Full Title	Handbook on Adhesive Bonding in Electronic Assembly Operations
Document Number	IPC-HDBK-4691
Document Type	Handbook (guidance document)
Published	November 2015
Pages	58 (full-color)
Publisher	IPC
Price	$124 (member) / $190 (non-member)

Purpose of IPC-HDBK-4691

The handbook serves two primary purposes:

1. Assist decision-makers who must choose adhesive bonding materials and methods for electronic assemblies
2. Guide operators who work in adhesive bonding operations with practical application information

The document provides guidelines for design, selection, and application of adhesive bonding specifically for electronic assembly—not general industrial bonding applications.

What IPC-HDBK-4691 Covers (and What It Doesn’t)

Understanding the scope of IPC-HDBK-4691 helps you know when to use it and when to look elsewhere.

Materials Covered by the Handbook

The handbook addresses liquid, paste, and gel adhesives that require a cure mechanism to achieve full performance. This includes:

Adhesive Format	Description	Common Examples
Liquid Adhesives	Low-viscosity flowable materials	Cyanoacrylates, low-viscosity epoxies
Paste Adhesives	Thixotropic materials for dispensing	Epoxy pastes, silicone pastes
Gel Adhesives	Non-flowing materials	Gel cyanoacrylates
Film Adhesives	Pre-formed sheets requiring cure	B-stage epoxy films

Materials NOT Covered by IPC-HDBK-4691

The handbook explicitly excludes several adhesive categories that are addressed by other IPC documents:

Excluded Material	Reason	Where to Find Guidance
Pressure-Sensitive Tapes	Different bonding mechanism	Separate IPC documents
Underfill Materials	Separate specialized topic	J-STD-030
SMT Adhesives	Covered by dedicated standard	IPC-SM-817
Thermally Conductive Adhesives	Separate specification	IPC-CA-821

This scope limitation ensures the handbook maintains focus on general-purpose structural and non-structural adhesive bonding for electronics.

Adhesive Chemistries in IPC-HDBK-4691

The handbook covers the major adhesive chemistries used in electronics manufacturing, providing guidance on selecting the right chemistry for each application.

Epoxy Adhesives

Epoxies are the workhorse of electronics adhesive bonding, offering excellent strength, chemical resistance, and durability.

Key Characteristics:

• High mechanical strength (tensile, shear, compression)
• Excellent chemical resistance
• Good adhesion to metals, ceramics, and many plastics
• Temperature resistance up to 150-200°C (standard) or 300°C+ (high-temp grades)
• Available in one-part (heat cure) and two-part (room temperature or heat cure) formulations

Common Electronics Applications:

• Component bonding and staking
• Potting and encapsulation
• Structural bonding of housings
• Die attachment
• Glob top protection

Silicone Adhesives

Silicones provide flexibility and wide temperature range performance that rigid adhesives cannot match.

Key Characteristics:

• Excellent flexibility and elongation
• Wide operating temperature range (-65°C to +200°C or higher)
• Good moisture resistance
• Low modulus (stress relief for thermal cycling)
• One-part (moisture cure, heat cure) and two-part formulations available

Common Electronics Applications:

• Conformal coating
• Sealing and gasketing
• Component bonding requiring flexibility
• High-temperature applications
• Vibration damping

Urethane (Polyurethane) Adhesives

Urethanes bridge the gap between rigid epoxies and flexible silicones.

Key Characteristics:

• Good flexibility with moderate strength
• Excellent impact and vibration resistance
• Good low-temperature performance
• Lower temperature resistance than epoxy or silicone (typically <125°C)
• Available in one-part (moisture cure) and two-part formulations

Common Electronics Applications:

• Potting for ruggedized assemblies
• Bonding dissimilar materials
• Applications requiring toughness and flexibility
• Cable strain relief

Cyanoacrylate Adhesives

Cyanoacrylates (instant adhesives) provide rapid bonding for high-volume production.

Key Characteristics:

• Very fast cure (seconds to minutes)
• High strength on most substrates
• No mixing required
• Limited gap-filling capability
• Moderate temperature and humidity resistance

Common Electronics Applications:

• Wire tacking
• Quick component attachment
• Prototype assembly
• Repair operations
• Lens bonding

Polyimide Adhesives

Polyimides offer the highest temperature performance for demanding applications.

Key Characteristics:

• Exceptional high-temperature resistance (300°C+)
• Excellent chemical resistance
• High strength retention at elevated temperatures
• Typically requires high cure temperatures
• Higher cost than other chemistries

Common Electronics Applications:

• High-temperature die attach
• Aerospace and military applications
• Under-hood automotive electronics
• Power electronics

Adhesive Chemistry Comparison

Property	Epoxy	Silicone	Urethane	Cyanoacrylate	Polyimide
Max Operating Temp	150-300°C	-65 to +200°C	-40 to +125°C	+80 to +120°C	+300°C+
Flexibility	Low-Medium	High	Medium-High	Low	Low
Cure Speed	Minutes-Hours	Minutes-Days	Hours	Seconds	Hours
Chemical Resistance	Excellent	Good	Good	Moderate	Excellent
Relative Cost	Low-Medium	Medium	Medium	Low	High

Cure Mechanisms Explained in IPC-HDBK-4691

The handbook provides detailed guidance on adhesive cure mechanisms, which directly impact process design and equipment requirements.

Heat Cure Adhesives

Heat cure adhesives require elevated temperature to initiate and complete polymerization.

Process Considerations:

• Cure temperature typically 80-175°C depending on formulation
• Cure time inversely related to temperature (higher temp = faster cure)
• Requires oven, hot plate, or integrated heating
• One-part systems offer convenience (no mixing)

Advantages:

• Long pot life at room temperature
• Controlled cure initiation
• Consistent properties batch-to-batch

Room Temperature Cure (Two-Part) Adhesives

Two-component systems cure when resin and hardener are mixed.

Process Considerations:

• Mixing ratio critical for proper cure
• Limited pot life after mixing (minutes to hours)
• Cure time typically 24 hours for full properties
• Heat can accelerate cure if needed

Advantages:

• No heating equipment required
• Suitable for heat-sensitive components
• Large gap-filling capability

Moisture Cure Adhesives

Moisture cure adhesives react with ambient humidity to polymerize.

Process Considerations:

• Cure rate depends on humidity level
• Cure proceeds from outside surface inward
• Deep sections may require extended cure time
• Storage must exclude moisture

Advantages:

• Simple one-part systems
• No mixing or heating required
• Good for sealing applications

UV/Light Cure Adhesives

UV cure adhesives polymerize when exposed to ultraviolet or visible light.

Process Considerations:

• Requires UV lamp or LED light source
• At least one substrate must be UV-transparent
• Shadow areas may not fully cure
• Dual-cure formulations available for shadowed regions

Advantages:

• Cure in seconds
• Precise cure control
• Excellent for automated assembly

Read more IPC Standards:

Surface Preparation for Adhesive Bonding

IPC-HDBK-4691 emphasizes that proper surface preparation is essential for reliable adhesive bonds. Even the best adhesive will fail on a contaminated or incompatible surface.

Surface Energy and Wetting

For an adhesive to form a strong bond, it must wet the substrate surface. Wetting depends on the relationship between adhesive surface tension and substrate surface energy.

General Rule: Adhesive surface tension should be lower than substrate surface energy for good wetting.

Substrate	Relative Surface Energy	Bondability
Metals (clean)	High	Excellent
Glass/Ceramics	High	Excellent
Most Plastics	Medium	Good
PTFE (Teflon)	Very Low	Difficult
Silicone Rubber	Very Low	Difficult
Polyethylene/Polypropylene	Low	Requires treatment

Common Surface Preparation Methods

Method	Description	Applications
Solvent Cleaning	Remove oils, greases, contaminants	General cleaning for most substrates
Abrasion	Mechanical roughening to increase surface area	Metals, plastics, composites
Plasma Treatment	Ionized gas increases surface energy	Low-surface-energy plastics
Chemical Etching	Acid or base treatment modifies surface	Metals, PTFE, polyolefins
Primer Application	Chemical coupling agent	Difficult-to-bond substrates

Surface Preparation Best Practices

1. Clean before treatment. Any surface modification is wasted if contaminants remain.
2. Process immediately. Treated surfaces degrade over time—bond as soon as possible after preparation.
3. Verify cleanliness. Use water break tests or contact angle measurements to confirm surface energy.
4. Control environment. Humidity, temperature, and contamination affect surface preparation effectiveness.

Application Methods for Electronics Adhesives

The handbook covers multiple adhesive application methods suitable for electronics manufacturing.

Syringe Dispensing

The most common method for precision adhesive application in electronics.

Equipment:

• Pneumatic or positive displacement dispensers
• Automated XYZ motion systems
• Various needle gauges and tips

Advantages:

• Precise volume control
• Flexible programming for different patterns
• Suitable for low to medium volumes

Screen and Stencil Printing

High-throughput method for applying adhesive to multiple locations simultaneously.

Equipment:

• Screen or metal stencil
• Squeegee or enclosed print head
• Vision alignment system

Advantages:

• High throughput
• Consistent deposit volume
• Excellent for high-volume production

Pin Transfer

Simultaneous application using an array of pins.

Equipment:

• Pin transfer plate (custom tooling)
• Adhesive reservoir
• Vertical motion mechanism

Advantages:

• Very high speed
• Consistent dot size
• Good for dedicated high-volume products

Manual Application

For prototypes, repairs, and low-volume production.

Methods:

• Syringe with manual plunger
• Squeeze tubes
• Spatulas or picks
• Brush application

Considerations:

• Operator training critical
• Less consistent than automated methods
• Suitable for complex geometries

Common Applications in Electronics Assembly

IPC-HDBK-4691 addresses several key application categories where adhesive bonding provides value.

Component Staking

Securing components to prevent movement during handling, thermal cycling, or vibration.

Design Considerations:

• Stake points should not interfere with inspection
• Adhesive must not contaminate solder joints
• Cure stress should not damage components

Wire and Lead Bonding

Strain relief and protection for wire bonds and component leads.

Design Considerations:

• Adhesive must be compatible with wire/lead materials
• Flexibility may be needed for thermal cycling
• Avoid wicking onto bond pads

Potting and Encapsulation

Complete enclosure of assemblies for environmental protection.

Design Considerations:

• CTE match between adhesive and components
• Thermal conductivity for heat dissipation
• Reworkability requirements

Structural Bonding

Load-bearing bonds for mechanical attachment.

Design Considerations:

• Joint design for stress distribution
• Environmental exposure conditions
• Long-term creep and fatigue behavior

Key Properties to Consider

The handbook helps engineers understand which properties matter for specific applications.

Mechanical Properties

Property	Importance	Typical Test Method
Tensile Strength	Load-bearing capability	ASTM D638
Shear Strength	Lap joint performance	ASTM D1002
Peel Strength	Resistance to peeling forces	ASTM D1876
Elongation	Flexibility and strain tolerance	ASTM D638
Modulus	Stiffness and stress transfer	ASTM D638

Thermal Properties

Property	Importance	Typical Test Method
Glass Transition (Tg)	Operating temperature limit	DSC, TMA
CTE	Thermal stress with substrates	TMA
Thermal Conductivity	Heat dissipation capability	ASTM D5470
Operating Temperature Range	Environmental limits	Various

Electrical Properties

Property	Importance	Typical Test Method
Volume Resistivity	Electrical insulation	ASTM D257
Dielectric Strength	Breakdown voltage	ASTM D149
Dielectric Constant	Signal integrity impact	ASTM D150

Rework and Repair Considerations

IPC-HDBK-4691 addresses the practical reality that adhesive bonds sometimes need to be removed for rework or repair.

Rework Methods

Method	Description	Considerations
Thermal	Heat to soften or degrade adhesive	Risk of component damage
Chemical	Solvents to dissolve adhesive	Long soak times, disposal concerns
Mechanical	Physical removal with tools	Risk of substrate damage
Combination	Multiple methods together	Often most effective approach

Design for Reworkability

When rework is anticipated, consider:

• Select adhesives with known rework procedures
• Minimize adhesive coverage area
• Avoid adhesive under critical components
• Document rework procedures in advance

Related IPC Standards and Documents

IPC-HDBK-4691 works alongside several companion documents that address specific adhesive applications.

Document	Title	Relationship
IPC-SM-817	General Requirements for Dielectric SMT Adhesives	SMT adhesive specifications
IPC-CA-821	General Requirements for Thermally Conductive Adhesives	Thermal adhesive specifications
J-STD-030	Selection and Application of Underfill Materials	Underfill guidance
IPC-HDBK-830	Guidelines for Design, Selection and Application of Conformal Coatings	Conformal coating guidance
IPC-CC-830	Qualification and Performance of Electrical Insulating Compound	Conformal coating specifications

Where to Purchase IPC-HDBK-4691

The official IPC-HDBK-4691 handbook is available from:

Source	Format	Website
IPC Official Store	PDF, Print	shop.ipc.org
ANSI Webstore	PDF	webstore.ansi.org
GlobalSpec	PDF	standards.globalspec.com

Pricing:

• Member price: $124 USD
• Non-member price: $190 USD

Available Languages:

• English (original)
• Chinese (translated version)

Best Practices from IPC-HDBK-4691

Based on the handbook’s guidance, here are key best practices for adhesive bonding success:

Material Selection

1. Match adhesive to application requirements. Don’t over-specify or under-specify properties.
2. Verify substrate compatibility. Test adhesion on actual production materials.
3. Consider the full operating environment. Temperature, humidity, chemicals, and UV exposure all matter.
4. Plan for process integration. Cure requirements must fit your production flow.

Process Control

1. Control incoming material quality. Verify viscosity, shelf life, and storage conditions.
2. Standardize surface preparation. Document and train operators on proper procedures.
3. Monitor critical parameters. Dispense volume, cure temperature, and cure time require tracking.
4. Validate with testing. Destructive testing on samples confirms process capability.

Quality Assurance

1. Establish acceptance criteria. Define what constitutes an acceptable bond.
2. Implement process controls. Prevention is more effective than inspection.
3. Document everything. Traceability enables root cause analysis when problems occur.
4. Review and improve. Continuous improvement based on field data and production experience.

Frequently Asked Questions

What is the difference between IPC-HDBK-4691 and IPC-SM-817?

IPC-HDBK-4691 is a handbook providing general guidance on adhesive bonding for electronics assembly. It covers multiple adhesive chemistries and applications but does not set pass/fail requirements. IPC-SM-817 is a specification that defines specific requirements and test methods for SMT adhesives used to hold components during wave soldering. If you need to understand adhesive bonding concepts and selection criteria, use IPC-HDBK-4691. If you need to qualify or specify SMT adhesives for wave soldering, use IPC-SM-817.

Does IPC-HDBK-4691 cover underfill materials?

No, underfill materials are explicitly excluded from IPC-HDBK-4691. Although there is overlap in chemistry and application methods, underfill materials have unique requirements related to flip-chip and BGA reliability that warrant separate treatment. For underfill guidance, refer to J-STD-030, “Selection and Application of Underfill Materials for Flip Chip and Other Micropackages.”

What adhesive chemistries does IPC-HDBK-4691 address?

The handbook covers the major adhesive chemistries used in electronics manufacturing: epoxy, silicone, urethane (polyurethane), cyanoacrylate, and polyimide. Each chemistry has different properties suited to specific applications. The handbook helps engineers understand these differences and select the appropriate chemistry for their requirements.

Is IPC-HDBK-4691 a specification or a guideline?

IPC-HDBK-4691 is a handbook (guideline), not a specification. It provides educational content, recommendations, and best practices for adhesive bonding but does not define mandatory requirements or pass/fail criteria. Specifications like IPC-SM-817 and IPC-CA-821 set actual requirements. The handbook helps engineers understand the principles behind adhesive selection and application so they can make informed decisions and properly implement specification requirements.

How does surface preparation affect adhesive bond strength?

Surface preparation is critical to adhesive bond strength—the handbook emphasizes this point repeatedly. Contaminants like oils, oxides, and release agents prevent intimate contact between adhesive and substrate. Low surface energy substrates may not allow proper wetting. The handbook covers cleaning methods, surface treatments (plasma, chemical, abrasion), and primers that improve adhesion. Even the best adhesive will fail on a poorly prepared surface, making surface preparation one of the most important factors in bond reliability.

Conclusion

IPC-HDBK-4691 fills a critical gap in electronics manufacturing guidance by consolidating practical adhesive bonding knowledge into a single comprehensive reference. The handbook helps engineers navigate the complex decisions involved in selecting adhesive chemistries, designing joint configurations, preparing surfaces, and implementing reliable bonding processes.

Whether you’re new to adhesive bonding or an experienced engineer looking for a systematic reference, IPC-HDBK-4691 provides the foundation for making informed decisions. Combined with the related specifications for specific applications (IPC-SM-817 for SMT adhesives, IPC-CA-821 for thermal adhesives, J-STD-030 for underfill), this handbook ensures you have the knowledge to implement adhesive bonding successfully in your electronic assemblies.

The investment in understanding adhesive bonding principles pays dividends in reduced failures, improved reliability, and more efficient manufacturing processes. IPC-HDBK-4691 is your guide to getting adhesive bonding right.

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This guide covers IPC-HDBK-4691 as published in November 2015. Always verify current revision status and consult the official handbook for complete guidance.