Backlack lamination bonding technology

Bonding Varnish / Backlack : The Joining Technology For Perfect Lamination Stacks             

The stator and rotor cores of electrical machinery are manufactured using thin laminations stacked together in order to minimize eddy current losses. Among various methods, Backlack technology stands out as a game-changer, offering a host of advantages that contribute to enhanced performance and efficiency. In this blog, we delve into the significance of Backlack, its advantages, and its application in revolutionizing the production of electrical machinery cores.           

Advantages of Backlack Technology

Freedom of Design

Backlack technology introduces unparalleled freedom of design in the manufacturing process. Unlike traditional methods where constraints such as interlocking positions or weld seams dictate design choices, Backlack enables engineers to optimize motor design without such limitations.

This freedom fosters the creation of more efficient electric motors tailored to specific applications.

Mechanical Stability and Dimensional Accuracy

Full-face adhesive bonding through Backlack ensures exceptional mechanical stability and dimensional accuracy. By eliminating expansion possibilities, laminations bonded with Backlack maintain tight tolerances, resulting in cores with superior shape stability.

Unlike welding processes that introduce tensions, Backlack bonding mitigates such risks, ensuring a robust core structure.

Maintenance of Magnetic Properties

Preserving the magnetic properties of electrical steel is paramount for optimal motor performance. Backlack’s non-damaging bonding technique ensures the integrity of the material’s microstructure, safeguarding its magnetic properties.

In contrast, other methods like interlocking and welding may compromise these properties, affecting overall motor efficiency.

Improved Thermal Conductivity

Efficient heat dissipation is essential for preventing motor overheating. Backlack-bonded laminations, with their narrow manufacturing tolerances, facilitate enhanced heat transfer between laminations and the motor housing.

This improved thermal conductivity not only enhances cooling efficiency but also reduces the size and weight of cooling units, making the overall system more compact and cost-effective.

Acoustic Advantages

Backlack’s viscoelastic properties offer acoustic benefits by effectively dampening vibrations in laminations. This feature finds application in electric machines where minimizing noise levels is critical.

By reducing vibrations, Backlack contributes to quieter operation, enhancing the user experience in various applications.

Bonding Process

adhesive bonded lamination stacks process

Preparation of Electrical Steel

The process begins with an electrical sheet coated with bonding varnish, which serves as the substrate steel for the punch of stator and rotor cores. 

Adhesive Bonded Lamination Stacks Process

The Backlack bonded rotor stacks and stator stacks process consists of two key phases:

Softening Phase: In this phase, the Backlack coating is softened by increasing the temperature, significantly reducing its viscosity. This allows for the diffusion and intermixing of coating layers, laying the foundation for a strong bond between laminations.

Cross-Linking Phase: As temperature is further increased, chemical cross-linking processes dominate, causing the Backlack to harden and lose its thermoplastic properties. This phase results in a stable, highly cross-linked duroplast with increased viscosity and adhesive strength, ensuring the durability and integrity of the bond.


Backlack technology has emerged as a cornerstone in the production of electrical machinery cores, offering unmatched advantages in terms of design flexibility, mechanical stability, and performance optimization.

By preserving magnetic properties, improving thermal conductivity, and reducing acoustic vibrations, Backlack contributes significantly to the efficiency and reliability of electric motors, particularly in the burgeoning field of electric mobility.

As pioneers in Backlack application, we are committed to providing cutting-edge solutions that elevate the standards of electrical machinery core and segmented stator bonding manufacturing, paving the way for a sustainable and electrified future.

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