A crimped terminal can look acceptable and still have a weak mechanical connection.
Incorrect crimp height, damaged conductor strands, poor wire stripping, worn tooling, or an unsuitable wire-to-terminal combination can all reduce connection strength. Some of these problems are difficult to identify through visual inspection alone.
Wire terminal pull force testing provides a practical way to evaluate crimp integrity by applying a controlled tensile load and measuring how the connection behaves.
This guide explains the test methods, failure modes, relevant IEC, IPC and automotive standards, and the key factors to consider when selecting terminal pull-force testing equipment.
Quick Answer: What Is a Terminal Pull Force Test?
A terminal pull force test measures the axial force applied to a crimped wire-to-terminal connection until the conductor pulls out, breaks, reaches a specified proof load, or meets another defined test endpoint.
The result should normally be evaluated using both:
Maximum Force + Failure Mode
There is no single pull-force limit that applies to every terminal. Acceptance criteria depend on factors such as wire size, conductor material, terminal design, application, applicable standard and customer specification.
What Is Wire Terminal Pull Force Testing?
Wire terminal pull force testing—also commonly called a crimp pull test, terminal pull test, or crimp tensile test—evaluates the mechanical retention of a wire-to-terminal connection.
During the test, the terminal is secured in a suitable fixture while the conductor is pulled along the intended test axis at a controlled speed.
The testing system records the applied force throughout the test.
Depending on the procedure, the test may continue until:
- the conductor pulls out of the terminal;
- the wire breaks;
- a specified force is reached;
- or a required load is maintained for a defined period.
The measured force is normally expressed in newtons (N).
However, a peak-force value alone does not always explain whether the connection behaved correctly.
The location and type of failure also matter.
Wire Tensile Strength, Breaking Force and Terminal Pull Force Are Not the Same
These three terms describe related but different mechanical properties.
Understanding the difference helps avoid incorrect test methods and acceptance criteria.
Wire Tensile Strength
Tensile strength is primarily a material property.
It describes how much tensile stress a material can withstand before failure and is normally related to the cross-sectional area of the specimen.
The question being answered is:
How strong is the conductor material?
Wire Breaking Force
Breaking force is the actual tensile force at which the wire or conductor fails.
Unlike tensile strength, which is typically expressed as stress, breaking force is normally expressed directly in units such as newtons.
The question becomes:
How much force is required to break this wire?
Terminal Pull Force
Terminal pull force evaluates the mechanical integrity of the wire-to-terminal connection.
The question is:
How securely does the crimp retain the conductor?
This distinction matters because a strong conductor does not automatically mean a strong crimp, and a high terminal pull-force result does not necessarily describe the material tensile strength of the wire.
Why Is Terminal Pull Force Important?
A crimp must provide both electrical contact and mechanical retention.
A connection that is too loose can suffer from poor retention or unstable electrical contact. A connection that is compressed too aggressively can damage conductor strands and weaken the wire.
Pull-force testing can help identify problems associated with:
- insufficient crimp compression;
- excessive crimping;
- incorrect crimp height;
- damaged or cut conductor strands;
- improper stripping;
- incorrect wire and terminal combinations;
- inconsistent conductor insertion;
- worn crimp tooling;
- incorrect tooling adjustment;
- production-process variation.
For this reason, terminal pull testing is commonly used during:
Process Development → First Article Inspection → Production QC → Supplier Verification → Reliability Validation
Typical applications include automotive wire harnesses, consumer electronics, appliances, industrial equipment, communication systems and other electrical assemblies.
How Is a Wire Terminal Pull Test Performed?
The exact procedure should always follow the applicable standard, customer specification or documented internal test method.
A typical test follows the steps below.
Step 1 — Prepare the Crimped Sample
Prepare the conductor and terminal using the required wire, stripping process, terminal and crimp tooling.
The specimen should represent the production connection being evaluated.
Where a standard specifies sample preparation, conditioning or other requirements, those conditions should be followed.
Step 2 — Secure the Terminal
Install the terminal in a suitable terminal fixture.
The fixture should hold the connection securely without deforming the critical crimp area or introducing an unrealistic load path.
Different terminal designs may require different fixtures. For example:
- blade terminals;
- ring terminals;
- open-barrel terminals;
- connector contacts;
- ferrules;
- custom contacts
may require different holding methods.
A universal fixture is not always the best solution.
Step 3 — Clamp the Wire
Secure the wire using an appropriate grip.
This is one of the most important parts of a repeatable pull test.
The grip should provide sufficient holding force to prevent slippage without crushing or cutting the conductor.
This becomes particularly important when testing fine wires, soft insulation, flexible stranded conductors and miniature electronic terminals.
Step 4 — Align the Specimen
The specimen should be aligned with the intended pulling axis.
Poor alignment can introduce:
Tension + Bending + Side Load
instead of a predominantly axial tensile load.
For consistent testing, the load path should be as straight as practical:
Terminal → Crimp → Wire → Pulling Direction
Misalignment is a common reason why apparently identical samples produce different results.
Step 5 — Set the Test Speed and Method
Set the required test speed and endpoint according to the applicable procedure.
Do not assume that one pulling speed is suitable for every crimp test.
Test conditions can vary according to:
- applicable standard;
- wire size;
- terminal design;
- customer specification;
- internal quality procedure.
A motorized tester allows the crosshead speed to be controlled rather than relying on manual pulling.
Step 6 — Apply the Tensile Load
Start the test and apply tensile load to the connection.
The testing system continuously records force during the pull.
Depending on the selected procedure, the test may stop when:
- the connection fails;
- the wire breaks;
- a specified load is reached;
- or a programmed holding period is completed.
Step 7 — Record Maximum Force and Failure Mode
Do not record only the highest number shown on the tester.
A useful test result should contain both the force value and the observed failure mode.
For example:
Maximum Force: 126 N
Failure Mode: Conductor Break
provides more useful information than 126 N alone.
Common Ways to Configure a Terminal Pull Test
The exact test configuration should come from the applicable specification or laboratory procedure.
Depending on the test requirement and capabilities of the testing system, terminal pull tests may be configured in several ways.
1. Pull & Break
The tensile load increases until the conductor or connection fails.
This is commonly used when the objective is to determine the:
Maximum Pull Force
and observe the corresponding failure mode.
2. Pull & Return
The specimen is loaded to a predetermined force and then unloaded.
This can be used as a proof-load style test when the objective is to verify that the connection withstands a specified force without being intentionally pulled to complete failure.
3. Pull & Hold
The force increases to a specified load and is maintained for a defined period.
This configuration can be useful when the test requirement specifies both:
Load + Holding Time
4. Pull, Hold & Break
The specimen is loaded to a specified force, held for the required period and then pulled further until failure.
This combines a proof-load stage with a destructive test.
Important: These are general test configurations. They should not be interpreted as four universal methods required by IEC 60352-2, IPC/WHMA-A-620 or SAE/USCAR-21. Always follow the procedure defined by the applicable specification.
Understanding Terminal Pull Test Results
One of the most common mistakes in crimp testing is treating the peak force as the entire result.
Consider two specimens.
Sample A
Maximum force: 120 N
Failure: Conductor Break
Sample B
Maximum force: 120 N
Failure: Terminal Pull-Out
The recorded forces are identical.
The failure behavior is not.
This is why terminal pull testing should normally evaluate:
Maximum Force + Failure Mode
rather than force alone.
Common Failure Modes
1. Conductor Break
The conductor breaks while the crimped connection remains engaged.
This indicates that failure occurred in the wire rather than through simple conductor withdrawal from the terminal.
However:
A conductor break does not automatically mean that the crimp passes.
The result must still be evaluated according to the applicable acceptance requirement and the actual failure location.
2. Terminal Pull-Out
The conductor pulls out of the crimp barrel.
This directly relates to the mechanical retention of the crimped connection.
The measured force should be compared with the applicable standard, terminal specification or customer requirement.
3. Grip Slippage
The wire moves inside the testing grip during loading.
This may be a test setup problem rather than specimen failure.
Possible causes include:
- insufficient clamping force;
- unsuitable jaw geometry;
- incorrect wire grip;
- smooth or difficult-to-grip insulation;
- incorrect specimen installation.
If slippage affects the force result, the test may need to be repeated.
4. Break at the Grip Edge
The conductor breaks directly beside the testing grip.
This can occur when the grip creates excessive local pressure or a stress concentration.
A break at the grip edge should therefore not automatically be interpreted as evidence of excellent crimp strength.
The setup should first be reviewed.
Wire Terminal Pull Force Testing Standards
There is no single standard that covers every type of terminal connection.
The correct standard depends on the product, application, wire type and target market.
Four references are particularly relevant when researching crimped wire and terminal connections.
IEC 60352-2 — Solderless Crimped Connections
IEC 60352-2:2024 — Solderless connections – Part 2: Crimped connections – General requirements, test methods and practical guidance
IEC 60352-2 is one of the primary international references for solderless crimped connections used in electrical and electronic equipment.
The current IEC publication covers appropriately designed uninsulated or pre-insulated crimp barrels used in crimp contacts, terminal ends or splices.
It applies to stranded wires from 0.05 mm² to 10 mm² cross-section and specified solid-wire applications.
The standard addresses requirements, test methods and practical guidance for evaluating crimped connections.
For manufacturers working with electrical or electronic terminals, it is one of the first standards worth checking when developing a crimp validation procedure.
Official Source: IEC — International Electrotechnical Commission
Reference: IEC 60352-2:2024
IPC/WHMA-A-620 — Cable and Wire Harness Assemblies
IPC/WHMA-A-620 — Requirements and Acceptance for Cable and Wire Harness Assemblies
IPC/WHMA-A-620 is widely referenced in cable and wire harness manufacturing.
It addresses requirements and acceptance criteria associated with cable and harness assemblies, including crimped connections.
Pull-force testing can form part of the mechanical verification of crimp quality within a wire-harness quality system.
When applying IPC/WHMA-A-620, laboratories should verify:
- applicable revision;
- product class;
- customer requirements;
- wire and terminal configuration;
- required acceptance criteria.
The standard should not be reduced to a single universal pull-force number for all harnesses.
Official Source: IPC / Global Electronics Association
Reference: IPC/WHMA-A-620
SAE/USCAR-21 — Automotive Cable-to-Terminal Crimps
For automotive wire-harness applications, SAE/USCAR-21 is particularly relevant.
The specification focuses on performance validation of solderless cable-to-terminal electrical crimps.
Automotive crimp reliability is not determined by pull force alone.
Depending on the validation program, mechanical, electrical and environmental behavior may all need to be considered.
Typical applications include:
- automotive wire harnesses;
- ECU connections;
- sensors;
- vehicle lighting;
- power distribution systems;
- connector assemblies;
- electrical modules.
For automotive suppliers, USCAR requirements may also be combined with individual OEM specifications.
Official Source: SAE International / USCAR
Reference: SAE/USCAR-21
UL 486A-486B — Wire Connectors
For certain North American wire-connector applications, UL 486A-486B may also be relevant.
UL 486A-486B applies to wire-connector applications rather than every miniature electronic or automotive crimp.
Related UL 486-family standards address other categories of electrical connections.
The actual product category should therefore be confirmed before selecting the applicable UL standard.
Official Source: UL Solutions
Reference: UL 486A-486B
Related Standard: IEC 60512-16-8
Another useful reference is:
IEC 60512-16-8:2008 — Connectors for electronic equipment – Tests and measurements – Part 16-8: Mechanical tests on connections and terminations – Test 16h: Insulating grip effectiveness (crimped connections)
This standard provides a test method for assessing the effectiveness of the insulation grip of a crimped connection.
It should not be confused with the conductor crimp pull-force requirement.
This distinction can be important because a terminal may contain both:
Conductor Crimp + Insulation Support
and the two regions serve different functions.
Quick Comparison of Relevant Standards
| Standard | Typical Application | Main Relevance |
|---|---|---|
| IEC 60352-2:2024 | Electrical and electronic crimped connections | General crimp requirements, test methods and guidance |
| IPC/WHMA-A-620 | Cable and wire harness assemblies | Harness workmanship, acceptance and crimp verification |
| SAE/USCAR-21 | Automotive wiring systems | Cable-to-terminal crimp performance validation |
| UL 486A-486B | Wire connectors | North American connector applications |
| IEC 60512-16-8 | Crimped connector terminations | Insulation grip effectiveness |
Important: Always use the applicable edition of the standard together with terminal manufacturer data, customer drawings and OEM specifications where required.
What Is the Minimum Pull Force for a Crimped Terminal?
This is one of the most frequently asked questions in terminal pull testing.
It is also one of the easiest questions to answer incorrectly.
There Is No Universal Minimum Pull Force
A crimped terminal does not automatically pass because it reaches one generic force value.
The required pull force depends on several variables.
1. Wire Gauge or Conductor Cross-Section
A miniature signal wire and a large power conductor should not be expected to use the same minimum pull-force requirement.
Wire size is one of the first variables to identify.
2. Conductor Material
Copper, aluminum and other conductor materials have different mechanical behavior.
Requirements developed for one conductor material should not automatically be applied to another.
3. Terminal Design
Different terminal constructions behave differently during crimping and tensile loading.
Examples include:
- open-barrel terminals;
- closed-barrel terminals;
- connector contacts;
- ring terminals;
- ferrules;
- blade terminals.
4. Crimp Geometry
Crimp height, width and conductor compression influence mechanical retention.
Incorrect crimp geometry can produce either weak retention or excessive conductor damage.
5. Application
A low-current connection inside a consumer device and an automotive power connection may operate in very different mechanical environments.
Application requirements therefore matter.
6. Applicable Standard
IEC, IPC, SAE/USCAR and UL standards do not necessarily use identical test procedures or acceptance criteria.
7. OEM and Customer Specifications
For many automotive, electronics and industrial projects, the final requirement may come from:
OEM Specification + Terminal Drawing + Internal Standard
rather than from a general international standard alone.
Therefore, instead of asking:
“How many newtons should a crimped terminal withstand?”
ask:
“Which pull-force requirement applies to this wire, terminal, application and standard?”
Why Do Terminal Pull Test Results Vary?
If five apparently identical terminals produce five different results, it is tempting to immediately blame the crimping process.
That may be correct.
But the testing setup should also be investigated.
Misalignment
Pulling the specimen at an angle introduces bending and side loading.
This changes the mechanical condition being tested.
Grip Slippage
If the wire slides inside the grip, the measured displacement and peak force may not represent the intended test.
Excessive Grip Pressure
Increasing grip pressure is not always the solution.
Excessive pressure can damage fine conductors and create a premature failure location.
Incorrect Terminal Fixture
The fixture should restrain the terminal without damaging the connection or changing the intended load path.
Test-Speed Variation
Tests should be performed using the speed required by the applicable procedure.
Changing speed between tests introduces another variable.
Unsuitable Load Cell
Another common issue is simply using a load cell that is much larger than necessary.
For example, if the expected terminal pull force is around tens of newtons, selecting the largest available load cell is not automatically the best choice.
More capacity does not automatically mean better measurement.
How to Choose a Wire Terminal Pull Force Tester
A pull-force tester should be selected around the specimen and test requirement, not simply around maximum machine capacity.
1. Determine the Expected Force Range
Start with:
Minimum Expected Force → Typical Force → Maximum Expected Force
For example:
- miniature terminals may require relatively low forces;
- standard wire-harness terminals may operate in the tens or hundreds of newtons;
- larger wires and cable assemblies may require higher test capacities.
This information helps determine the appropriate load-cell range.
2. Select the Load Cell
Avoid choosing the load cell simply by asking:
“Which one has the highest capacity?”
A better question is:
“Which capacity gives appropriate measurement performance around my expected test force?”
When contacting a testing-machine supplier, provide the expected test-force range whenever possible.
3. Check Force Accuracy
Terminal pull testing is frequently used to compare:
- production batches;
- crimp-tool settings;
- suppliers;
- process changes;
- terminal designs.
A stable force measurement system is therefore important for meaningful comparison.
4. Check Test-Speed Control
If the applicable procedure specifies pulling speed, the tester should be able to control and reproduce that speed.
Servo-controlled movement is particularly useful where multiple test procedures are required.
5. Select the Terminal Fixture
The terminal fixture should match the actual terminal geometry.
Possible configurations include:
Blade Fixture | Ring-Terminal Fixture | Contact Holder | Adjustable Fixture | Custom Fixture
6. Select the Wire Grip
Wire diameter, insulation, conductor structure and flexibility all affect grip selection.
Fine wires can require a very different grip from a heavy cable.
The goal is:
No Slippage + No Premature Grip Damage
7. Consider Data Recording
For laboratory and quality-control applications, useful data can include:
- peak force;
- force-displacement curve;
- test speed;
- sample identification;
- Pass/Fail result;
- failure mode;
- test report.
This makes it easier to compare production conditions and maintain traceability.
RS-8010A for Wire and Terminal Pull Force Testing
For laboratories that need controlled low-force tensile testing rather than a simple manual pull gauge, the ITM-LAB RS-8010A Single Column Tensile Test Machine can be configured for wire, cable, terminal and connector pull testing.
The platform supports multiple load-capacity options and different grips according to the specimen and expected force.
Key Specifications
| Parameter | RS-8010A |
|---|---|
| Load Capacity | Multiple options up to 5 kN |
| Load Accuracy | ±0.25% |
| Load Resolution | 1/500,000 |
| Test Speed | 0.001–500 mm/min |
| Stroke | 650 mm / 1000 mm optional |
| Effective Width | 130 mm |
| Displacement Resolution | 0.001 mm |
| Motor | AC servo motor |
| Transmission | High-precision ball screw |
The machine can be combined with different terminal and wire fixtures depending on sample geometry.
With alternative grips, the same platform can also support other low-force mechanical tests.
For laboratory applications, software-based force curves and test reports can help engineers compare samples and document results.
Configuration Note: Final machine configuration should be selected according to expected force, wire size, terminal geometry, fixture requirements and applicable test standard.
Example: Selecting a Tester for a Small Crimp Terminal
Consider a manufacturer testing a wire terminal with an expected pull force of approximately:
80–150 N
Should the selection process begin by choosing a 5 kN load cell?
Not necessarily.
A better workflow is:
Step 1 — Identify the Wire
Determine wire gauge or conductor cross-section.
Step 2 — Identify the Terminal
Confirm terminal type and crimp configuration.
Step 3 — Identify the Standard
Determine whether IEC, IPC, USCAR, UL or an OEM/customer specification applies.
Step 4 — Estimate the Pull-Force Range
Determine the expected minimum, normal and maximum test forces.
Step 5 — Select an Appropriate Load Cell
Choose a measurement range appropriate to the actual test.
Step 6 — Select the Terminal Fixture
The terminal should be securely held without changing the intended loading condition.
Step 7 — Select the Wire Grip
Choose a grip that prevents slippage without damaging the conductor.
Step 8 — Program the Test
Set the required:
Speed + Endpoint + Hold Condition + Data Recording
according to the test procedure.
Terminal Pull Force Testing Checklist
Before starting a terminal pull test:
- Confirm wire gauge or conductor cross-section.
- Confirm conductor material.
- Identify terminal type.
- Confirm the applicable standard and revision.
- Check customer or OEM requirements.
- Determine the required test method.
- Determine the expected force range.
- Select an appropriate load cell.
- Install the correct terminal fixture.
- Select a suitable wire grip.
- Set the required test speed.
- Align the specimen with the pulling axis.
- Check for grip slippage.
- Record maximum force.
- Record the failure mode.
- Save the result for traceability.
Frequently Asked Questions
What is a wire terminal pull force test?
A wire terminal pull force test applies a controlled axial tensile load to a crimped wire-to-terminal connection. It is used to evaluate mechanical retention by measuring the force reached during the test and observing how the specimen fails.
What is the minimum pull force for a crimped terminal?
There is no universal minimum pull-force value for all crimped terminals.
The required value depends on wire size, conductor material, terminal construction, application, applicable standard and customer specification.
Standards such as IEC 60352-2, IPC/WHMA-A-620 and SAE/USCAR-21 may be relevant depending on the product.
Which standard is used for terminal pull testing?
Common references include:
IEC 60352-2 for solderless crimped connections;
IPC/WHMA-A-620 for cable and wire harness assemblies;
SAE/USCAR-21 for automotive cable-to-terminal crimps;
and certain UL 486-series standards for applicable wire connectors.
The correct standard depends on the product and target market.
What is the difference between wire tensile strength and terminal pull force?
Wire tensile strength evaluates a material's resistance to tensile stress.
Terminal pull force evaluates the mechanical retention of a wire-to-terminal connection.
They answer different engineering questions and should not be treated as interchangeable measurements.
Does a conductor break mean the crimp automatically passes?
No.
A conductor break does not automatically mean that the crimp passes.
The measured force, failure location and applicable acceptance requirement must all be considered.
A break caused by excessive pressure at the wire grip, for example, should not be interpreted in the same way as a valid specimen failure.
What causes low terminal pull force?
Possible causes include:
- incorrect crimp height;
- insufficient compression;
- damaged conductor strands;
- incorrect stripping;
- incorrect wire-to-terminal combination;
- tooling wear;
- poor conductor positioning.
However, test problems such as grip slippage and specimen misalignment can also produce abnormal results.
Why does the wire break before the terminal pulls out?
This can occur when the wire section reaches its mechanical limit before the conductor is extracted from the crimp.
The failure location still needs to be checked.
A normal conductor break and a break immediately beside an over-tightened testing grip should not automatically be treated as equivalent results.
How should I choose a pull tester for small terminals?
Start with the expected test-force range rather than the maximum capacity of the machine.
Then evaluate:
Load Cell → Accuracy → Speed Control → Terminal Fixture → Wire Grip → Data Recording
For relatively low-force terminal testing, choosing an appropriately sized load cell can be particularly important.
Conclusion
Wire terminal pull testing appears simple: secure the terminal, grip the wire and pull.
Obtaining a repeatable and meaningful result requires more care.
The test method, applicable standard, load-cell range, pulling speed, specimen alignment and fixture design can all influence the measurement.
Engineers should also look beyond the peak force.
A useful result combines:
Maximum Force + Failure Mode
For manufacturers working with cable assemblies, electrical connectors and wire harnesses, standards such as IEC 60352-2, IPC/WHMA-A-620 and SAE/USCAR-21 provide useful frameworks for defining test procedures, but the final requirement may also depend on the terminal manufacturer, OEM or customer specification.
When selecting test equipment, start with five pieces of information:
Wire Size → Terminal Type → Expected Force → Applicable Standard → Fixture Requirement
This makes it much easier to select the appropriate load cell, grip and test configuration.
Need Help Selecting a Terminal Pull Test Configuration?
Send us:
Wire size + Terminal type + Expected pull force + Applicable standard + Sample photo
ITM-LAB engineers can use this information to recommend a suitable load-cell range, grip configuration and test setup for your application.
