IPC-SM-817: Complete Guide to SMT Adhesive Requirements & Testing

If you’ve ever had components fall off during wave soldering or watched perfectly placed chips slide out of position before reflow, you understand why SMT adhesives matter. The IPC-SM-817 standard exists to ensure these adhesives actually do their job—holding components in place through every thermal and mechanical stress your assembly process throws at them.

I’ve seen production lines grind to a halt because someone picked the wrong adhesive or skipped the cure verification step. This guide covers everything the standard requires, plus the practical knowledge that keeps your bottom-side components where they belong.

What Is IPC-SM-817?

IPC-SM-817, officially titled “General Requirements for Dielectric Surface Mounting Adhesives,” is an IPC standard that defines requirements and test methods for adhesives used to hold SMT components in place during assembly. The current revision is IPC-SM-817A, released in December 2014, updating the original 1989 version.

The standard covers adhesives used in three primary scenarios:

• Holding bottom-side SMT components during wave soldering
• Securing components during double-sided reflow
• Temporary fixation before solder paste reflow

Unlike solder paste specifications that focus on electrical connections, IPC-SM-817 addresses the mechanical bonding that keeps components physically attached to the board throughout the assembly process.

Scope and Purpose of IPC-SM-817

The standard defines dielectric (non-conductive) surface mounting adhesives through specification of test methods and inspection criteria. It covers adhesives intended for application by:

• Pin transfer
• Syringe dispensing
• Screen/stencil printing

Different cure methods are addressed including UV or visible light curing, heat curing, and ambient temperature curing.

Who Needs This Standard?

IPC-SM-817 is essential for:

• Process engineers selecting SMT adhesives for production
• Quality engineers establishing incoming inspection criteria
• Purchasing departments writing adhesive specifications
• Contract manufacturers validating customer-supplied materials
• Adhesive manufacturers developing SMT products

Why SMT Adhesives Are Critical for Assembly

Before diving into the standard’s requirements, let’s understand why these materials matter so much in modern electronics manufacturing.

The Wave Soldering Challenge

When a PCB passes through wave soldering, bottom-side SMT components face a serious problem: gravity wants to pull them into the molten solder wave. Without adhesive holding them in place, small chip components like 0402s and 0603s would simply drop off into the solder pot.

The adhesive must:

• Survive preheat temperatures up to 150°C
• Maintain bond strength through the solder wave (typically 250-260°C)
• Not contaminate solder joints or leave residues affecting reliability

Double-Sided Reflow Applications

In double-sided reflow, components on the first side must stay attached when the board flips and passes through reflow again. While solder surface tension helps, larger components may require adhesive reinforcement to prevent shifting or tombstoning.

Mixed Technology Assembly

Boards combining through-hole and SMT components often use wave soldering for through-hole parts while SMT components ride on the bottom side. This scenario puts maximum stress on the adhesive bond during exposure to the solder wave.

IPC-SM-817 Adhesive Classification System

The standard classifies adhesives primarily by their cure method, which significantly impacts process integration and equipment requirements.

Adhesive Cure System Classification

Classification	Cure Method	Typical Cure Conditions	Common Applications
IPC-SM-817/1	Heat Cure	120-150°C for 60-120 seconds	Wave soldering, general purpose
IPC-SM-817/2	UV/Visible Light	365-405nm, 2-10 seconds	High-speed inline, quick fixation
IPC-SM-817/3	Ambient Cure	Room temperature, 24-72 hours	Low-volume, heat-sensitive applications
IPC-SM-817/4	Dual Cure (UV + Heat)	UV prefixation + thermal postcure	Shadowed areas, complex geometries

Heat Cure Adhesives (Type 1)

Heat cure adhesives are the most widely used in production environments. They’re typically single-component epoxy systems that cure when exposed to elevated temperatures.

Advantages:

• Well-understood process integration
• Cure happens in existing reflow or dedicated cure ovens
• Excellent long-term reliability
• Lower material cost compared to UV systems

Considerations:

• Requires dedicated cure step or zone
• Cure time adds to overall cycle time
• Board and components must tolerate cure temperatures

UV/Visible Light Cure Adhesives (Type 2)

UV cure adhesives polymerize rapidly when exposed to appropriate wavelengths of light, typically in the 365-405nm range.

Advantages:

• Cure in seconds rather than minutes
• Minimal heat exposure to components
• On-demand curing for precise process control
• Excellent for high-speed dispensing lines

Considerations:

• Requires UV exposure equipment
• Shadow areas under components may not fully cure
• Higher material cost
• Light-blocking components limit application

Ambient Cure Adhesives (Type 3)

These adhesives cure at room temperature, typically through moisture-initiated mechanisms similar to cyanoacrylate chemistry.

Advantages:

• No cure equipment required
• No thermal stress on components
• Simple process integration

Considerations:

• Long cure times (hours to days for full strength)
• Humidity-sensitive cure rates
• Limited production throughput

Dual Cure Systems (Type 4)

Dual cure adhesives combine UV and thermal cure mechanisms, providing both rapid fixture and complete cure in shadowed areas.

Advantages:

• Fast initial fixture with UV
• Complete cure of shadowed areas with heat
• Combines benefits of both cure methods

Considerations:

• More complex process control
• Higher material cost
• Requires both UV and thermal equipment

Test Methods Specified in IPC-SM-817

The standard references specific test methods to evaluate adhesive properties critical for SMT applications.

Uncured Adhesive Properties

Property	Test Method	Purpose	Typical Requirement
Viscosity	ASTM D2556	Ensure dispensability	50,000-500,000 cPs
Thixotropic Index	Viscometer ratio	Predict dot profile	3.0-8.0 typical
Density	ASTM D1875	Volume-to-weight conversion	1.2-1.6 g/cm³
Shelf Life	Viscosity change over time	Storage planning	6-12 months at -40°C

Cured Adhesive Properties

Property	Test Method	Purpose	Typical Requirement
Shear Strength	ASTM D1002	Bond strength assessment	>5 MPa
Dielectric Constant	ASTM D150	Electrical properties	3.0-5.0 at 1 MHz
Volume Resistivity	ASTM D257	Insulation verification	>10¹² ohm-cm
Surface Insulation Resistance	IPC-TM-650 2.6.3	Post-cure reliability	>10⁸ ohms
Glass Transition Temperature	DSC or TMA	Thermal stability	>100°C

Shear Strength Testing

Shear strength is the primary mechanical property for evaluating SMT adhesive performance. The test measures the force required to shear a bonded component from the substrate.

Test Configuration:

• Standard chip component (typically 1206 or 2012 size)
• Adhesive dot of specified diameter and height
• Cured per manufacturer recommendations
• Shear tool applied at 45° angle to substrate

Acceptance Criteria:

• Minimum shear force varies by component size
• Failure mode should be cohesive (within adhesive) or adhesive (at interface)
• Substrate damage indicates over-testing

Surface Insulation Resistance (SIR) Testing

SIR testing verifies that the adhesive doesn’t degrade the electrical reliability of the assembly. The test subjects cured adhesive to elevated temperature and humidity while measuring insulation resistance between adjacent conductors.

Test Conditions:

• 85°C temperature
• 85% relative humidity
• Applied bias voltage (typically 50V DC)
• 1000-hour exposure duration

Pass Criteria:

• Resistance must remain above 10⁸ ohms throughout testing
• No visible corrosion or dendritic growth

Read more IPC Standards:

Application Methods for SMT Adhesives

IPC-SM-817 addresses adhesives suitable for multiple application techniques, each with distinct advantages and process considerations.

Syringe Dispensing

Syringe dispensing remains the most common method, accounting for approximately 80% of production applications.

Process Description:

• Adhesive loaded in pressure-driven syringe
• Needle deposits controlled dot at programmed coordinates
• Pneumatic or positive displacement systems available

Advantages:

• Maximum flexibility for design changes
• No tooling required
• Suitable for mixed component sizes
• Easily handles low-volume, high-mix production

Typical Parameters:

• Dispense speeds: 20,000-60,000 dots per hour
• Needle gauge: 18-25 (0.84-0.26mm ID)
• Dot diameter: 0.3-2.0mm depending on component

Pin Transfer

Pin transfer uses an array of pins that simultaneously dip into adhesive and transfer dots to the substrate.

Process Description:

• Pin plate configured for specific board design
• Pins dip into adhesive reservoir
• Plate transfers to board and deposits adhesive
• Single motion applies all dots simultaneously

Advantages:

• Very high throughput for high-volume production
• Consistent dot-to-dot volume
• Simple equipment maintenance

Limitations:

• Expensive tooling for each board design
• Limited flexibility for design changes
• Minimum component spacing constraints

Stencil Printing

Stencil printing applies adhesive through apertures in a metal stencil, similar to solder paste printing.

Process Description:

• Stencil with apertures aligned to adhesive locations
• Adhesive squeegeed across stencil surface
• Material deposits through apertures onto substrate
• Stencil lifts leaving adhesive dots

Advantages:

• High throughput capability
• Excellent dot-to-dot consistency
• Can share equipment with solder paste printing

Limitations:

• Separate stencil from solder paste (different thickness)
• Aperture clogging with some adhesive formulations
• Limited to pre-component placement

Common Defects and Troubleshooting

Even with proper material selection, SMT adhesive processes can produce defects that impact yield and reliability.

Insufficient Bond Strength

Symptoms:

• Components fall off during wave soldering
• Low shear test values
• Adhesive failure mode during testing

Root Causes and Solutions:

Root Cause	Solution
Undercure	Verify cure profile with DSC; extend cure time/temperature
Contaminated substrate	Clean boards before dispensing; check solder mask compatibility
Inadequate dot volume	Increase dispense pressure/time; verify needle condition
Expired material	Check date codes; verify proper storage conditions
Moisture absorption	Store per manufacturer requirements; use fresh material

Stringing and Tailing

Symptoms:

• Thin strings of adhesive between dot and needle
• Contamination of adjacent pads
• Inconsistent dot profiles

Root Causes and Solutions:

Root Cause	Solution
Incorrect viscosity	Verify material temperature; check for contamination
Poor thixotropic recovery	Switch to higher thixotropic index material
Dispense height too high	Reduce needle-to-board gap
Needle wear	Replace dispensing needle

Dot Profile Problems

Symptoms:

• Flat, spread-out dots (slump)
• Excessive height variation
• Inconsistent diameter

Root Causes and Solutions:

Root Cause	Solution
Material too warm	Control ambient temperature; reduce substrate preheat
Substrate contamination	Clean boards; verify solder mask cure
Incorrect dispense parameters	Optimize pressure, time, and needle height
Material aging	Use fresher material; verify storage conditions

Cure-Related Issues

Symptoms:

• Tacky surface after cure
• Low hardness readings
• Premature component movement

Root Causes and Solutions:

Root Cause	Solution
Insufficient cure temperature	Verify oven profile with thermocouples
Too short cure time	Extend conveyor dwell time
UV underdose (light cure)	Check lamp intensity; verify exposure time
Shadow areas (UV cure)	Consider dual-cure material; add thermal postcure

Related IPC Standards

IPC-SM-817 works alongside several companion standards in the electronics assembly ecosystem.

Standard	Title	Relationship to IPC-SM-817
J-STD-001	Requirements for Soldered Electrical and Electronic Assemblies	References SM-817 for adhesive acceptance
IPC-A-610	Acceptability of Electronic Assemblies	Visual inspection criteria for adhesive
IPC-TM-650	Test Methods Manual	Contains referenced test procedures
IPC-SM-840	Qualification for Permanent Solder Mask	Substrate compatibility considerations
J-STD-004	Requirements for Soldering Fluxes	Flux-adhesive compatibility
J-STD-030	Underfill Material Selection	Related adhesive technology

Where to Purchase IPC-SM-817

The official IPC-SM-817A standard is available from authorized distributors:

Source	Format	Notes
IPC Store	PDF, Print	Official source
ANSI Webstore	PDF	ANSI-accredited distribution
Techstreet	PDF, Print	Multi-user licenses available
SAI Global	PDF, Print	Standards subscription options

Pricing: Approximately $32-93 USD depending on format and vendor.

Document Details:

• Current Revision: IPC-SM-817A
• Release Date: December 2014
• Pages: 9 (plus referenced test methods)

Material Storage and Handling Requirements

Proper storage and handling significantly impact SMT adhesive performance. The standard references manufacturer specifications, but general guidelines apply across most products.

Storage Conditions

Most SMT adhesives require refrigerated storage to maintain their properties:

Storage Parameter	Typical Requirement	Notes
Temperature	0-10°C (refrigerated) or -40°C (frozen)	Varies by formulation
Humidity	Sealed container	Moisture causes viscosity changes
Shelf Life	6-12 months	From date of manufacture
Light Exposure	Dark storage for UV-cure types	Prevents premature polymerization

Pre-Use Conditioning

Before dispensing, adhesives typically require temperature equilibration:

• Remove from refrigerator 2-4 hours before use
• Allow sealed container to reach room temperature (23±3°C)
• Never accelerate warming with heat guns or ovens
• Verify viscosity before loading into dispensing equipment

Open Time Considerations

Once exposed to ambient conditions, adhesive properties begin changing:

• Moisture absorption increases viscosity
• Volatile loss affects rheology
• UV-cure materials may partially polymerize under fluorescent lighting
• Stencil printing exposes large surface areas—monitor bath life carefully

Industry-Specific Applications

Different industries have varying requirements for SMT adhesive selection and testing.

Consumer Electronics

High-volume consumer products prioritize throughput and cost:

• Fast cure cycles essential (typically <2 minutes)
• UV cure popular for inline processing
• Emphasis on high-speed dispensing compatibility
• Reworkability may be required for yield recovery

Automotive Electronics

Automotive applications demand extreme reliability:

• Extended temperature range (-40°C to +125°C typical)
• High shear strength requirements for vibration resistance
• Long-term reliability per AEC-Q200 or similar specifications
• Traceability and lot control mandatory
• Thermal cycling resistance is critical for under-hood applications

Medical Devices

Medical applications add biocompatibility and regulatory requirements:

• USP Class VI certification may be required
• ISO 10993 biocompatibility testing
• Stringent lot-to-lot consistency requirements
• Full material disclosure for regulatory submissions
• Sterilization compatibility (EtO, gamma, autoclave) must be verified

Aerospace and Military

The most demanding requirements for adhesive performance:

• Wide temperature operating range (-65°C to +150°C or beyond)
• Outgassing specifications per NASA or MIL standards
• Radiation resistance for space applications
• Extensive qualification testing beyond IPC-SM-817 minimums
• Full material traceability from raw materials through final assembly
• Often requires QPL (Qualified Products List) approved materials

Practical Recommendations for Engineers

Based on years of working with SMT adhesives in production, here are my key recommendations:

Material Selection

1. Match cure method to your line capability. Don’t specify UV cure if you don’t have UV equipment in your process flow.
2. Verify solder mask compatibility early. Some low-surface-energy masks cause adhesion failures that only appear after qualification.
3. Consider your smallest components. Adhesive rheology that works for 0805s may string unacceptably on 0201s.
4. Plan for wave soldering temperatures. Adhesive Tg must exceed your wave solder preheat and contact temperatures.

Process Control

1. Monitor viscosity at incoming inspection. A 20% viscosity increase from the spec sheet often indicates storage damage.
2. Verify cure with DSC testing. Visual inspection cannot detect partial cure that leads to field failures.
3. Document your process window. Temperature, humidity, and adhesive age all affect performance—track them.
4. Establish shear strength acceptance limits. Regular shear testing catches process drift before it becomes a yield problem.

Frequently Asked Questions

What is the difference between IPC-SM-817 and IPC-SM-817A?

IPC-SM-817A is the current revision, released in December 2014 to update the original 1989 version. The “A” revision modernized test method references and aligned the document with current industry practices. If you’re purchasing the standard today, you’ll receive the SM-817A version.

Can I use UV cure adhesive for wave soldering applications?

Yes, but with caution. UV cure adhesives work well for wave soldering if the adhesive is fully exposed to the UV source. However, components block light from reaching adhesive directly underneath them, potentially leaving uncured material. For wave soldering, either use heat cure adhesives or select dual-cure (UV + thermal) formulations that complete curing during preheat.

How do I verify that SMT adhesive is fully cured?

Visual inspection is insufficient—cured and uncured adhesives often look identical. Use Differential Scanning Calorimetry (DSC) to measure residual cure exotherm. A fully cured sample shows no remaining reaction. For production monitoring, establish shear strength limits based on your DSC-verified process and test shear strength regularly.

What causes components to fall off during wave soldering?

The most common causes are insufficient adhesive volume, inadequate cure, and contaminated substrate surfaces. First, verify your cure profile reaches the adhesive manufacturer’s specified time and temperature. Then check adhesive dot size—smaller components need proportionally larger dots relative to their footprint. Finally, ensure substrate surfaces are clean and compatible with your adhesive.

Is SMT adhesive electrically conductive?

No, IPC-SM-817 specifically covers dielectric (non-conductive) adhesives. These materials must maintain high insulation resistance even after exposure to temperature and humidity stress. Conductive adhesives for electrical connections are covered under different specifications. The dielectric requirement in SM-817 ensures the adhesive won’t create shorts between adjacent conductors.

Conclusion

IPC-SM-817 provides the essential framework for selecting and qualifying SMT adhesives that reliably hold components through the stresses of modern electronics assembly. Understanding the classification system, test methods, and application techniques covered in this guide will help you avoid the common pitfalls that lead to component loss and assembly failures.

The key takeaways: match your cure method to your process capabilities, verify material properties at incoming inspection, and never assume visual appearance indicates complete cure. Take these steps seriously, and your bottom-side components will stay exactly where your pick-and-place machine put them.

Whether you’re working in high-volume consumer electronics or low-volume aerospace applications, the principles remain the same—proper material selection, process control, and verification testing are essential for reliable SMT adhesive performance.

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This guide covers IPC-SM-817A requirements as of the December 2014 revision. Always verify current revision status and consult the official standard for specification compliance.