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【Popular Science】Three Core Performance Indicators of Terminal Crimping｜Complete Control Guide for Physical Profile, Mechanical Strength and Electrical Stability
- Categories:Industry News
- Author:Guangdong Deke Electric Co., Ltd.
- Origin://m.hymfwq.com/
- Time of issue:2026-08-15 15:57
- Views:
【Popular Science】Three Core Performance Indicators of Terminal Crimping｜Complete Control Guide for Physical Profile, Mechanical Strength and Electrical Stability
- Categories:Industry News
- Author:Guangdong Deke Electric Co., Ltd.
- Origin://m.hymfwq.com/
- Time of issue:2026-08-15 15:57
- Views:
Crimping is the core process to achieve permanent and reliable connection between terminals and cables. A qualified crimp must satisfy three criteria simultaneously: favorable physical geometry, dependable mechanical performance and stable electrical performance. Failure in any dimension will lead to hidden risks such as contact resistance drift, wire breakage and signal failure under vibration, high/low temperature and long-term energized operating conditions. Combining universally accepted industrial engineering acceptance criteria, this article systematically sorts out key points for full-process control.
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DEKEELEC —— —— —— —— —— —— —— —— —— —— —— —— —— —— ——
I. Physical Geometry Performance Control (Benchmark for Visual and Dimensional Requirements)
Physical geometry serves as the first inspection checkpoint for crimp quality. Clear boundaries are defined for stripping, conductor arrangement, crimp contour, angular tolerance, sealing structure and cut-off tab dimensions. Visual defects will directly trigger mechanical and electrical failures.
1. Specification for Wire Stripping Process
Stripping shall be performed by professional precision stripping equipment. Defects including skewed insulation cuts, insulation damage, incomplete stripping, broken conductor strands, flared copper strands and excessive twisting of stranded wires are strictly prohibited.
- Special control requirement: After stripping silver-plated conductors, operators must wear clean gloves and avoid direct bare-hand contact to prevent oxidation induced by sweat contamination.
- Acceptance criteria for broken strands: Calculate allowable damaged strand quantity based on wire cross-sectional area and total number of strands; round down the calculated decimal value to integer. Example 1: 0.35 mm² wire with 7 strands; 7×5%=0.35, rounded down to 0. No broken strands or nicks are permitted. Example 2: 1.0 mm² wire with 32 strands; 32×8%=2.56, rounded down to 2. A maximum of 2 strands are allowed to have nicks or be missing.
- Strip length: Prioritize dimensions specified in terminal manufacturer drawings. If original specifications are unavailable, the formula 0.75+A+B/2 can be adopted for open-barrel terminals. Select the closest standard values after calculation: 3.0, 4.1, 4.6, 5.1, 5.6, 6.4, 7.1, 8.1, 8.6, 9.7, 10.2 mm.
2. Specification for Conductor Brush
After crimping, conductor strands extend forward from the front plane of the conductor barrel, with maximum extension length ≤1 mm. Extended strands shall not interfere with the terminal mating zone, self-locking structure or locking screws. For screw-locked receptacle terminals, conductor strands must not intrude into the screw locking area to avoid jamming and strand crushing.
3. Position Requirements for Conductor and Insulation
The boundary between conductor and insulation shall be clearly exposed within the transition observation zone between the conductor barrel and insulation barrel. Process grading: Compliant status is the standard target; marginally acceptable status must not occur in mass production, and equipment adjustment shall be implemented immediately once detected; conditions exceeding limits are directly judged non-conforming.
4. Requirements for Terminal Mating Area
The crimp forming process must not cause deformation, scratches or twisting on the terminal mating section. After crimping, all dimensional specifications and elastic performance of the mating area shall comply with terminal drawing requirements.
5. Limit Values for Distortion and Bend Angle of Crimp Zone
Based on the central axis of the terminal:
- Maximum lateral bend angle: ±3°
- Maximum vertical bend angle: ±5° Excessive angles easily lead to mating offset and unilateral poor contact.
6. Bell Mouth Forming Standards
① The conductor barrel must be fully closed;
② Rear bell mouth is a mandatory structure, its width shall not exceed that of the insulation barrel, dimensions comply with terminal specifications;
③ Front bell mouth dimension shall be smaller than the rear bell mouth;
④ No bell mouth is required at the second step for stepped crimp terminals.
Core function of bell mouth: Prevent sharp barrel edges from cutting copper strands; it is a critical structure against vibration-induced failure.
7. Tilt Angle of Insulation Crimp Wings
Allowable tilt range of insulation crimp wings: maximum 5° forward, maximum 3° backward. Out-of-tolerance angles easily cause unstable insulation clamping and wire loosening.
8. Acceptance Criteria for Four Types of Insulation Crimp Profiles
1. Symmetrical crimp: At least 1/3 of insulation circumference (120°) is wrapped by crimp wings. Crimp wings may slightly pierce insulation, but internal conductors must not be damaged.
2. Circular crimp: Insulation wrapping coverage ≥180°; acceptable if the opening between crimp wings ≤45°.
3. Annular crimp: Insulation wrapping coverage ≥180%; when the wire adopts maximum cross-section specification, the ends of bilateral crimp wings shall overlap by at least one terminal base material thickness.
4. Overlap crimp: At least 2/3 of insulation circumference is wrapped; two wings overlap mutually. Insulation piercing is permitted, while conductor damage is forbidden.
For terminals with housing self-locking structure, insulation crimp requirements shall follow terminal manufacturer specifications preferentially.
Supplementary requirements for dual-wire crimping: Insulation wrapping coverage ≥60%; ends of overlapping wings shall be closed; insulation shall have no risk of sliding or rotation. When wires are arranged vertically, the wire with smaller cross-section shall be placed at the bottom.
9. Judgment Criteria for Insulation Crimp Pressure Marks and Flash
Slight indentations and minor flash generated by crimp compression are acceptable. Cuts penetrating insulation to expose internal conductors are absolutely prohibited.
10. Insulation Bend Verification Test
Bend tests must be performed for insulation crimps. After no less than 3 bending cycles, insulation shall remain visible in the designated zone to verify strain relief performance.
11. Crimp Specification for Single Wire Seals
After crimping sealed terminals, the wire seal and insulation end face shall be visible within the designated zone; straightness and position of the seal comply with terminal specifications. Circular and annular crimp profiles best match wire seal structures. Crimp wings shall moderately curl to wrap the seal and prevent seal detachment during housing assembly. Over-compression is prohibited, and crimp wings must not pierce the seal. For sealed terminals with observation windows, the wire seal shall be visible through the window after crimping. Slight indentations on the seal surface are acceptable. Any breakage penetrating the seal and exposing wire insulation results in direct rejection.
12. Dimensional Control of Insulation Crimp
The width and height of insulation crimp shall not hinder complete insertion of terminals into housings. In the absence of special specifications, dimensional tolerances refer to general terminal standards.
13. Cut-off Tab Requirements
① The cut-off tab shall be visible after crimping; its length ≤ terminal base material thickness and maximum value ≤0.5 mm. For terminals equipped with wire seals, maximum cut-off tab length is 0.3 mm;
② Burr standards comply with terminal drawings. For sealed terminals, only tiny burrs oriented toward the terminal mating direction are allowed; burrs that may scratch wire seals are forbidden;
③ Cut-off tabs and burrs shall not impair terminal insertion and mating functions.
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II. Mechanical Performance Control: Tensile Test (Pull-out Resistance)
Static tensile testing serves as the core evaluation method for mechanical performance. It simulates vibrating and pulling service conditions to verify the bonding strength of crimped joints.
1. Basic test conditions: Tensile speed of 100±25 mm/min. During testing, the insulation crimp wings shall not be clamped; only the bonding strength of the conductor crimp zone is evaluated. The tensile threshold shall follow standards for the corresponding wire gauge where available. If no matching specification exists, adopt the standard for the next larger wire gauge as the acceptance criterion.
2. Test rules for dual-wire crimping: Select the wire with the smaller cross-sectional area among the two as the test specimen, and apply the tensile limit specified for the smaller wire.
3. Test rules for multi-wire crimping: Secure the wire with the minimum cross-sectional area at both ends. The tensile standard shall be based on the smallest wire gauge among all conductors.
Intelligent control solution: Deploy an intelligent tensile tester to automatically complete clamping, testing, judgment, data storage and report generation. Cloud-based data traceability can be realized, and the tester can interlock with crimping machines to block defective products. A closed-loop control system for crimp quality can be established to reduce errors caused by manual recording.
DEKEELEC —— —— —— —— —— —— —— —— —— —— —— —— —— —— ——
III. Electrical Performance Control: Voltage Drop and Long-Term Resistance Stability
Electrical performance determines the current-carrying capacity and long-term operational stability of connectors. Key evaluations cover voltage drop variation and resistance drift after thermal cycling, which constitute critical verification items for new-energy and high-current equipment.
1. Long-term Energized Voltage Drop Test
- Measurement point definition: Measure voltage drop between Point B and Point C for the terminal mating area; measure voltage drop between Point A and Point B for the conductor crimp zone.
- Test scheme: Arrange at least 10 sets of samples in order on an insulated test bench and connect to a stabilized power supply. Power cycle: alternate between 45 minutes energized and 15 minutes de-energized, with a total test duration of 200 hours.
- Record voltage drop values at 2 h and 200 h respectively. The joint is deemed electrically stable in the long run if the difference between the voltage drop at 2 h and 200 h is less than 0.3 mV/A.
2. Accelerated Environmental Resistance Stability Test (For Non-sealed Terminals)
Sample quantity: 10 pieces per specification; DC resistance is measured using a 4-wire milliohm meter.
Test procedure:
1. Initial resistance measurement
2. Thermal shock cycling: 72 cycles alternating between -40 °C (30 min) and +125 °C (30 min)
3. Temperature-humidity alternating cycling: 4 cycles (65 °C / 95~98% RH for 16 h → -40 °C for 2 h → +85 °C for 2 h → 25 °C for 4 h)
4. Re-measure resistance upon test completion
Acceptance criterion: The resistance variation of each single sample before and after testing shall be less than 0.3 mΩ to meet the requirement of stable contact resistance under long-term service conditions.
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A qualified crimp requires simultaneous compliance in three aspects: physical geometry, mechanical strength and electrical performance. Acceptable visual appearance does not guarantee satisfactory pull-out resistance, and qualified pull-out strength cannot rule out resistance drift under long-term energization. For high-reliability applications (new energy, medical devices, industrial automation, AI computing equipment), apart from routine visual inspection, crimp height monitoring and pull test sampling, periodic voltage drop tests and accelerated environmental tests are necessary to proactively prevent failure risks during long-term service.
DEKEELEC —— —— —— —— —— —— —— —— —— —— —— —— —— —— ——
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