USCAR-38丨Performance Specification for Ultrasonically Welded Wire Terminations

The new energy vehicle industry, where SBT Ultrasonic is a key player, has just been rocked by a breaking news.

Elon Musk unveiled Tesla’s self-driving robotaxi—the Cybercab—at an event in California. There was no steering wheel or pedals, nor was there a plug—Musk said the vehicle charges inductively to regain power wirelessly. Undoubtedly, Cybercab has brought autonomous vehicles, once only seen in science fiction novels, into reality.

In reality, the automotive industry is being reshaped by intelligence and electrification, with an increasing number of sensors and smart devices being integrated into vehicles. However, they only function properly when connected to control units. Automotive wiring harnesses act as the "nervous system" and "blood vessels" for transmitting electrical signals and power throughout the vehicle. Even in the era of autonomous driving, reliable connections between wiring harnesses and terminals remain crucial.

From SBT's perspective, ultrasonic welding technology is particularly suited for joining high-voltage cables and terminals in EVs. Compared to traditional welding methods, it offers multiple advantages, including low internal resistance, minimal temperature rise, and ease of automation control. As ultrasonic welding technology and equipment continue to evolve, safer and more efficient connections for wiring harnesses and terminals become possible.

Using reliable ultrasonic welding equipment is akin to providing the safest protection for a car's "nervous system" and "blood vessels." As an ultrasonic welding partner to many well-known automotive wiring harness manufacturers and OEMs, SBT Ultrasonic strictly implements the test methods and acceptance criteria defined by the USCAR-38 standard, ensuring the reliability, stability, and durability of the welding connections.

What is USCAR-38？

USCAR-38 defines test methods and performance criteria for evaluating ultrasonically welded wire-to-terminal metallurgical bonds. 

The main content includes:

1.Applicable use: This specification is applicable where the wire and terminal are part of an electrical connection system used in road vehicles at ambient temperatures from -40 to +150 °C. Applied voltage may be either low (0 to 60 VDC) or high (to 1000 VAC or VDC).

2.Test procedures and acceptance criteria: USCAR-38 details the general testing requirements, including visual inspection, welded termination cross-section analysis, weld bond tensile and peel strength.

3.Accelerated environmental exposure (thermal shock) conditioning: This environmental conditioning procedure details the requirement for establishing the functional performance of electrical and electronic components when subjected to alternating high and low temperature environments. Rapid transfer between the two environments tests the component’s ability to withstand drastic temperature changes.

According to the latest USCAR-38, the ideal weld bond appearance should meet the following characteristics:

• All strands are welded.
• Weld bond is contained by terminal (w/ clearance on sides).
• All wires reach the end of the weld nugget.
• Strands beyond the weld nugget do not interfere with functional areas nearby (terminal, eyelet, heat shrink, etc.).
• Bond has no scorching, foreign material, or contamination.

In the automotive electrical connection system, in addition to the USCAR-38 standard, there are also standards such as USCAR-21, USCAR-37, and USCAR-45. Together, they form the standard system for automotive electrical connections, providing a safeguard for the safe operation of vehicles.

SBT develops ultrasonic wire harness welding machines in accordance with the USCAR-38 standard requirements, including weld bond tensile and peel strength tests, as well as environmental resistance tests. These machines can meet the welding requirements for various scenarios involving wires and terminals, cover mainstream wire sizes.

SBT Ultrasonic has developed a brand-new in-line monitoring systems for wire harness welding, effectively compensating for the shortcomings of traditional curve monitoring. This technology achieves comprehensive process monitoring of the ultrasonic welding system, preventing issues such as batch virtual welding and joint failure, thereby enhancing the efficiency of production and quality departments and safeguarding the safety of automotive cables.

As a professional supplier of ultrasonic wire harness welding equipment, SBT Ultrasonic is committed to providing the automotive industry with efficient, reliable, innovative, and internationally standardized high-quality welding solutions. The company actively promotes technological and product innovation, empowering higher quality and more reliable wire harness connection solutions.