Crimp vs Solder Terminations: Which is Better for Wire Harness?
The definitive 2026 guide to choosing between crimping and soldering for your wire harness connections. Learn why crimping wins in 90% of applications—and when soldering is the right choice.
When assembling a wire harness, one of the most fundamental decisions you'll make is how to terminate wire connections. Should you crimp or solder? This debate has been settled in professional circles for decades, but misconceptions persist among hobbyists and even some engineers.
With over 18 years manufacturing cable assemblies for automotive, mining, and industrial applications, we've tested both methods extensively. Here's what we've learned from millions of terminations in real-world conditions.
Quick Verdict: Crimping Wins
In 90% of wire harness applications, crimping is the superior connection method. This is the industry standard endorsed by IPC/WHMA-A-620, used by every automotive manufacturer, and required in aerospace, defence, and professional motorsport wiring.
Use Crimping For:
- • Automotive wire harnesses
- • Industrial equipment
- • Mining & heavy machinery
- • Marine & outdoor applications
- • Aerospace & defence
- • Any vibration environment
Use Soldering For:
- • PCB connections
- • RF/coaxial connectors (center pin)
- • Field repairs when crimping is impossible
- • Joining dissimilar wire gauges
- • Stationary, low-vibration electronics
How Crimping Works: The Cold Weld Process
Crimping is a mechanical process that permanently joins a wire to a terminal using controlled deformation. When done correctly, a crimp creates what engineers call a "cold weld"—a gas-tight, metal-to-metal bond without heat.
The Science Behind a Good Crimp
A high-quality crimp tool applies tremendous force (typically 10-20 kN) to compress the terminal barrel around the wire strands. This force is so great that the wire strands and terminal material deform into a single, solid mass. If you cut a proper crimp in half and examine it under a microscope, you should see no air gaps between the strands—just one continuous piece of metal.
This "cold welding" effect creates an electrical connection that's actually stronger than the wire itself. If you pull a properly crimped connection until it fails, the conductor strands will break before the crimp joint separates.
Crimping Advantages
Superior Vibration Resistance
Crimped connections maintain flexibility, allowing them to absorb vibration without developing fatigue cracks. This is why every automotive manufacturer uses crimping exclusively.
Environmental Sealing
Crimp connections create an air-tight seal that prevents moisture, dirt, and corrosive elements from reaching the conductor. Essential for outdoor, marine, and mining applications.
Speed & Consistency
A skilled operator can crimp terminals in seconds. Ratcheting crimp tools ensure consistent force every time, eliminating skill-dependent variability.
Industry Standard
IPC/WHMA-A-620 Class 2 and Class 3 requirements specify crimping for terminal connections. Defence, aerospace, and automotive standards mandate crimped connections.
Crimping Disadvantages
- Tool Investment: Quality ratcheting crimp tools cost $200-500 for basic terminals, or $800-2500+ for specialized automotive (Deutsch, Molex) or MIL-SPEC connectors.
- Terminal-Specific Tooling: Different terminal types require different dies or tools. You can't use one universal tool for all crimps.
- Irreversible: Unlike soldering, a crimped connection cannot be undone. If you make a mistake, you must cut and re-terminate.
- Wire Damage Risk: Using incorrect tools or settings can nick or sever conductor strands, creating a weak point.
How Soldering Works: Heat-Based Metal Bonding
Soldering creates electrical connections by melting a filler metal (solder) that bonds with the base metals through a process called wetting. The solder alloy (traditionally tin-lead, now often lead-free) has a lower melting point than copper wire, allowing it to flow into gaps and create a metallurgical bond.
Soldering Advantages
Low Tool Cost
A basic soldering kit costs $30-100. Unlike crimping, you don't need terminal-specific tools—one iron works for almost any application.
Flexibility
Solder can join different wire gauges, different metals, and repair damaged connections. It's more versatile for one-off or repair situations.
Low Resistance
A well-executed solder joint can have marginally lower electrical resistance than a crimp—though the difference is negligible in most applications.
Reworkable
Unlike crimps, solder joints can be desoldered and reworked if needed—valuable for prototyping and repairs.
Soldering Disadvantages
- Vibration Failure: Solder creates rigid joints that concentrate stress, leading to fatigue cracks under vibration. This is why automotive and aerospace prohibit soldering.
- Wicking Problem: Molten solder wicks up wire strands by capillary action, turning flexible stranded wire into a rigid rod. The wire then breaks at the solder boundary.
- Skill-Dependent: Quality varies dramatically based on operator skill. Cold solder joints, insufficient wetting, and overheating are common failures.
- Heat Damage Risk: Excessive heat can damage wire insulation, nearby components, or heat-sensitive connectors.
- Slower Production: Soldering takes longer than crimping and cannot be easily automated for wire harness production.
- RoHS Compliance: Lead-based solder is restricted under RoHS, requiring lead-free alternatives that are harder to work with.
The Wicking Problem: Why Solder Fails in Vibration Environments
Critical Failure Mode
The biggest enemy of soldered connections in wire harnesses is wicking. When you apply solder to stranded wire, the molten tin alloy is drawn up under the insulation by capillary action. This transforms a flexible stranded conductor into a solid, rigid rod for several millimeters beyond the visible joint.
Here's what happens next: When that wire vibrates (as in any vehicle or machinery), the mechanical stress concentrates exactly at the point where the solder stops and the flexible wire begins. Over time, fatigue cracks form at this transition zone, and eventually, the wire snaps.
Real-World Failure Example
We've investigated numerous electrical failures in mining equipment where previous technicians had "repaired" wire harnesses by soldering. In one case, a haul truck experienced intermittent sensor failures after 6 months. The cause? Soldered splice repairs that passed initial testing but cracked internally from constant vibration. The solder joint itself remained intact—but the wire strands fractured inside the insulation at the wicking boundary.
This failure mode is insidious because it's invisible. The wire looks fine externally, but flexing reveals the hidden fracture. Professional motorsport and aerospace have learned this lesson the hard way, which is why solder is never used in racing wiring harnesses.
"Solder is never used in professional motorsport wiring harnesses. A properly executed crimp joint is actually stronger than the base wire itself—meaning if you pull on a crimped joint until it fails, the conductor strands will break before the crimp fails."
— Haltech, ECU Manufacturer
Head-to-Head Comparison
| Factor | Crimping | Soldering |
|---|---|---|
| Vibration Resistance | Excellent ✓ | Poor (fatigue failure) |
| Connection Strength | Stronger than wire ✓ | Good (when done well) |
| Production Speed | Fast (2-5 seconds) ✓ | Slow (30-60 seconds) |
| Consistency | High (tool-controlled) ✓ | Variable (skill-dependent) |
| Tool Cost | $200-2500+ | $30-100 ✓ |
| Environmental Sealing | Excellent (air-tight) ✓ | Fair (with protection) |
| Reworkability | No (cut and re-terminate) | Yes (desolder) ✓ |
| Wire Gauge Flexibility | Limited by terminal | Any gauge ✓ |
| IPC-620 Compliance | Required for Class 2/3 ✓ | Limited applications |
| Automotive/Aerospace | Industry standard ✓ | Not permitted |
Table: Direct comparison of crimping vs soldering for wire harness applications. Green checkmarks indicate the better option for each factor.
When to Use Each Method
Use Crimping (90% of Applications)
- All automotive wiring: Engine bay, chassis, body harnesses
- Industrial equipment: Motors, PLCs, sensors, control panels
- Mining & construction: Any harsh environment application
- Marine: Boat wiring, offshore equipment
- Aerospace & defence: MIL-SPEC requirements
- Any production environment: Where speed and consistency matter
Use Soldering (The Other 10%)
- PCB connections: Component leads, through-hole, SMD
- RF/coaxial connectors: SMA, BNC center pins (impedance-critical)
- Field repairs: When proper crimp tooling isn't available
- Dissimilar wire gauges: Joining 16 AWG to 8 AWG
- Prototyping: When connections need to be modified
- Stationary electronics: No vibration, controlled environment
Critical Mistakes to Avoid
Mistake #1: Soldering After Crimping
Never add solder to a crimped connection. If the crimp is good, solder provides zero additional strength. If the crimp is bad, solder just hides the defect while adding wicking and brittleness. Industry standards explicitly prohibit soldering crimps. The heat from soldering can also damage the crimp zone and cause solder to wick into the wire.
Mistake #2: Pre-Tinning Wire Before Crimping
Never tin (solder) a wire before inserting it into a crimp terminal. Solder is softer than copper and will "creep" or flow under the constant pressure of the crimp. Over time, this causes the connection to loosen, increasing resistance and potentially causing overheating. This is a common mistake among hobbyists coming from a soldering background.
Mistake #3: Using the Wrong Crimp Tool
Generic crimping pliers produce unreliable connections. Each terminal type requires a specific die profile and crimp force. Using a universal stripper/crimper instead of a proper ratcheting crimp tool is asking for failure. Invest in the correct tool for your terminal type—the cost is negligible compared to field failures.
Mistake #4: Twist-and-Tape Splices
Never twist wires together and cover with electrical tape. This creates a high-resistance connection that corrodes, loosens under vibration, and will eventually fail. Use proper butt splices with heat shrink, or better yet, plan your harness to avoid field splices entirely.
IPC/WHMA-A-620 Industry Standards
The IPC/WHMA-A-620 standard is the industry bible for wire harness manufacturing. It clearly defines when crimping is required and sets acceptance criteria for crimp quality.
IPC-620 Class Definitions
For Class 2 and Class 3 products, IPC-620 requires crimped terminations for wire-to-terminal connections. The standard specifies crimp height, pull force testing, and visual inspection criteria. Learn more about our testing capabilities and IPC-620 compliance.
"In 18 years of wire harness manufacturing, I've never seen a properly executed crimp fail. I have seen countless soldered connections fail in the field—always at the wicking boundary, always in vibration environments. When customers ask 'should I solder for extra strength?', my answer is always the same: if your crimp needs solder, you have a bad crimp. Fix the crimp."
Hommer Zhao
Technical Director, OurPCB Australia
18+ Years Wire Harness Manufacturing Experience
Frequently Asked Questions
Is crimping or soldering better for wire harness connections?
Crimping is better for 90% of wire harness applications. It provides superior vibration resistance, consistent quality, and is the industry standard per IPC/WHMA-A-620. Soldering is only preferred for PCB connections, RF connectors, and specific repair situations where crimping is impossible.
Why do automotive manufacturers use crimping instead of soldering?
Automotive manufacturers use crimping because solder creates rigid joints that crack under vibration. The 'wicking' effect draws solder up the wire strands, creating a stress concentration point where the wire will eventually fatigue and break. Crimped connections remain flexible and withstand years of vehicle vibration without failure.
Should I solder a crimped connection for extra strength?
No, never solder a crimped connection. If the crimp is good, solder adds no value. If the crimp is bad, solder just hides the defect. The heat from soldering can cause solder wicking into the wire, making the connection weaker and more prone to failure. IPC-620 standards explicitly prohibit soldering crimps.
What tools do I need for proper crimping?
You need a ratcheting crimp tool matched to your specific terminal type. Quality tools cost $200-500 for basic terminals, or $800-2500 for specialized automotive or MIL-SPEC connectors. Using the correct tool is critical—generic crimping pliers produce unreliable connections that will fail in service.
When is soldering the right choice?
Soldering is appropriate for: PCB component connections, RF/coaxial connector center pins (where impedance matching is critical), field repairs when proper crimp tooling isn't available, joining dissimilar wire gauges, and prototyping where connections need modification. For stationary electronics in controlled environments, soldering can be acceptable.
Can I pre-tin wire before crimping?
No, never pre-tin (solder) wire before inserting it into a crimp terminal. Solder is softer than copper and will 'creep' under the constant pressure of the crimp, causing the connection to loosen over time. This increases resistance and can cause overheating. Always crimp bare copper wire.
Sources & References
Need Professional Wire Harness Assembly?
With 18+ years of experience and investment in professional crimp tooling for Deutsch, Amphenol, Molex, and MIL-SPEC connectors, we deliver IPC-620 compliant crimped connections for any application. Let our team handle your wire harness manufacturing with guaranteed quality.
IPC-620 Certified
All crimps meet Class 2/3 standards with documented quality control
Professional Tooling
$15,000+ invested in crimp tools—no need for you to buy equipment
100% Tested
Every harness undergoes continuity and pull-force testing