Why need ultrasonic welding machine for Car charging power cable

The core reason why ultrasonic welding equipment has become the core welding technology for new energy vehicle charging cables (hereinafter referred to as "new energy charging cables") is that it perfectly matches the core requirements of new energy charging cables: "high current, high reliability, resistance to harsh environments, and mass production." It solves the technical pain points of traditional welding (such as soldering and crimping) and is also suitable for the special application scenarios of new energy vehicles (such as fast charging, vehicle vibration, and wide temperature environments). The following systematically analyzes its adaptation logic from three dimensions: the core welding requirements of new energy charging cables, the technical adaptability of ultrasonic welding, and its comparative advantages over traditional processes.

I. First, clarify: the core welding requirements of new energy charging cables (more stringent than ordinary car charging cables)

The usage scenarios of new energy charging cables (such as Type-C and GB/T DC charging gun cables) are "high-power fast charging (200V-1000V, 10A-50A) + vehicle vibration / high and low temperatures / humid environments + long-term repeated plugging and unplugging." Therefore, the welding requirements far exceed those of ordinary consumer-grade charging cables, focusing on four key points: Low and stable contact resistance: Under high current, the contact resistance increases by... Even a resistance of 1 mΩ can cause localized heating (Q=I²Rt), potentially leading to insulation melting and short circuit risks. Therefore, the contact resistance at the weld joint must be ≤30 mΩ, with no significant increase over long-term use.

Extremely high mechanical strength: The charging cable must withstand repeated insertion and removal forces and vehicle vibration (10-2000Hz). The pull-out strength at the weld joint must be ≥10N, with no detachment or breakage.
Environmental reliability: Adaptable to a wide temperature range of -40℃ to 85℃, high humidity, and salt spray (outdoor charging scenarios). The weld joint must be free of oxidation and corrosion, and have stable electrical performance.
Free of harmful substances + mass production compatibility: Meets the "environmental protection" requirements for new energy vehicles (lead-free, solder residue-free), and is also compatible with industrial mass production (single-piece welding time ≤50ms, yield ≥99.5%).

II. Technical Adaptability of Ultrasonic Welding: Precisely Addressing Core Needs
Ultrasonic welding, through the physical mechanism of "high-frequency vibration friction - metallurgical bonding," is theoretically compatible with the stringent requirements of new energy charging cables. The specific adaptation logic is as follows:

1. Low Contact Resistance: Metallurgical Bonding Achieves "Atomic-Level Conductivity"

The conductors of new energy charging cables are mostly multi-strand tin-plated copper wire (0.3-1.0mm²) or copper braided wire, with terminals made of tin-plated/gold-plated copper alloy (ensuring conductivity).

During ultrasonic welding, high-frequency vibration (20-40kHz) breaks the oxide layer (CuO, SnO) on the surface of the copper wire and the terminal, allowing direct contact between the pure metal surfaces. At localized high temperatures (200-400℃), atomic diffusion occurs, forming a "metallurgical bonding layer" (several micrometers thick)—the contact resistance of this bonding method is far lower than that of traditional "mechanical crimping" (physical contact, relying on pressure to maintain conductivity) and "tin soldering" (where the solder layer has interface resistance).

In practical applications, the contact resistance of ultrasonic welding can be stabilized at... 1. **10-30mΩ:** With a resistance change of ≤5% after long-term use (temperature and vibration resistance), it fully meets the low-heat requirements for high-current transmission.

2. **High Mechanical Strength:** Dual reinforcement of metallurgical bonding and physical interlocking. When welding the multi-strand copper wire harness to the terminals of new energy charging cables, ultrasonic vibration causes slight deformation of the copper wires, embedding them into the welding groove of the terminals, forming a "physical interlocking." Simultaneously, the interatomic forces in the metallurgical bonding layer make the joint strength far exceed that of a simple mechanical connection. After optimizing parameters (e.g., power 3-5kW, pressure 0.3-0.5MPa, time 30-50ms), the pull-out strength at the weld can reach 15-25N, which is 2-3 times the strength of traditional crimping (5-10N). It can withstand the tensile force of repeated plugging and unplugging of charging cables and vehicle vibration, preventing the joint from falling off.

3. Environmental Reliability: Gapless + No Solder Residue, Anti-oxidation and Corrosion Resistant
The metallurgically bonded joint has no obvious interface gaps, making it difficult for moisture and oxygen to penetrate, effectively preventing internal oxidation; at the same time, the welding process requires no solder or flux, avoiding the problems of "solder oxidation and flux residue leading to corrosion" found in tin soldering; Environmental testing has verified that after 50 cycles at -40℃ to 85℃, the contact resistance change of the ultrasonically welded joint is ≤8%; after salt spray testing (5% NaCl solution, 48 hours), there is no significant corrosion, making it fully suitable for the harsh outdoor and in-vehicle environments of new energy vehicles.

4. Environmentally Friendly + Mass Production Adaptable: Highly Efficient and Pollution-Free, Meeting Industrialization Needs
Ultrasonic welding is a "physical process," with no lead or organic solvent emissions, meeting the environmental standards for new energy vehicles (such as EU RoHS and China GB/T 2423). The welding time is extremely short (10-50ms/point), far exceeding that of soldering (several seconds/point) and crimping (tens of seconds/point). Combined with a fully automated production line (automatic feeding, positioning, welding, and inspection), production capacity can reach over 100,000 pieces/day, with a stable yield rate of over 99.5%, making it suitable for the mass production needs of new energy vehicle components.

5. Adaptable to Special Conductor Materials: Meeting the High Conductivity Requirements of Fast Charging Cables To reduce resistance, new energy fast charging cables often use high-purity copper (99.99%), copper-silver alloys, and other materials. These materials have high melting points (copper 1083℃), making it difficult for traditional soldering (melting point 231℃) to achieve an effective connection (the bonding force between solder and copper is weak). However, ultrasonic welding's "low-temperature metallurgical bonding" (below the melting point of copper) is a perfect fit, achieving a reliable connection without damaging the conductor material.

Frequency Stability: Frequency fluctuation ≤ ±0.5kHz, avoiding poor welding consistency due to energy instability;
Pressure Control Accuracy: Pressure adjustment accuracy ±0.01MPa, ensuring uniform welding pressure;
Positioning Accuracy: Industrial equipment must be equipped with visual or mechanical positioning (accuracy ≤ ±0.05mm) to avoid welding misalignment;
Material Compatibility: Welding head material selected is titanium alloy (TC4) or hard alloy, with good wear resistance and thermal conductivity, suitable for metal/plastic welding;
Protection Rating: Equipment protection rating ≥ IP54, suitable for dusty and oily workshop environments.

Welding Head Selection (Core Components):
Metal Welding Head: Made of titanium alloy, designed with a "groove type" (fitting the terminal welding groove) to avoid damage to copper wires and terminals;
Plastic Welding Head: Made of aluminum alloy, with anodized surface treatment, customized according to the shell shape (e.g., round, square), ensuring uniform energy transfer.

VI. Quality Inspection and Reliability Verification As an in-vehicle electronic accessory, the welding quality of car charger cables directly affects safety. Therefore, they must pass three layers of inspection: "Appearance Inspection + Electrical Performance + Environmental Reliability":

1. Appearance Inspection (100% Full Inspection)
Visual inspection or observation with a magnifying glass (10-20x): No loose wires at the weld, no deformation of the terminals, no melt overflow in the plastic shell, and no warping of the PCB;
Dimensional Inspection: Use calipers to measure the length of the weld and the spacing between the terminals; deviation ≤ ±0.1mm.

2. Electrical Performance Inspection
Contact Resistance Test: Use a micro-ohmmeter (accuracy 0.01mΩ) to measure the resistance of the weld; ≤50mΩ is acceptable;
Conductivity Test: Apply a 5V DC voltage and test the stability of current transmission; no open circuit or short circuit is acceptable;
Current Withstand Test: Pass the rated current (such as 2A, 3A, or 5A commonly found in car chargers) for 1 hour; weld temperature ≤60℃ is acceptable.

3. Environmental Reliability Verification (Sampling Inspection, AQL Standard)

Tension Strength Test: The weld joint is stretched at a speed of 5 mm/min using a tensile tester; ≥5N is acceptable.

Temperature Resistance Test: -40℃ (4 hours) → Room Temperature (30 minutes) → 85℃ (4 hours), cycled 5 times; no peeling and contact resistance change ≤10% are acceptable.

Humidity Resistance Test: 40℃, 90% RH, for 10 consecutive days; no oxidation or corrosion is acceptable.

Vibration Resistance Test: 10-2000Hz, acceleration 10g, 2 hours each for X/Y/Z axes; no peeling or short circuit is acceptable.

Waterproof Test (Outer Shell Welding): IP54 standard; spray water for 15 minutes; no water ingress is acceptable.