High-frequency protection

In precision manufacturing sectors such as electronics, automotive, medical devices, and new energy, the edge sealing, splicing, and forming of protective films have evolved from simple wrapping into an integrated process combining structural sealing with performance protection. High-frequency (HF) welding and ultrasonic welding—currently the mainstream adhesive-free thermal bonding technologies—have become the primary choices for downstream protective film processing due to their advantages in efficiency, cleanliness, and versatility. These two processes differ fundamentally in their operating principles, compatible materials, forming outcomes, and application scenarios; these differences directly determine the seal strength, surface smoothness, and long-term reliability of the protective film. This article analyzes the distinctions between these two welding technologies—from their technical fundamentals to practical implementation—and outlines optimal mass-production solutions tailored to the material properties of Jidong New Materials' TPU protective films.

I. Differences in Core Principles: Fundamental Distinctions in Energy Form and Heating Logic

High-frequency welding (HF welding) utilizes a 27.12 MHz high-frequency electromagnetic field to induce rapid oscillation of polar molecules within polar polymer materials (such as PVC and TPU). This molecular oscillation generates internal frictional heat, enabling the material to melt and bond from the inside out without the need for an external heat source—a process known as dielectric heating. Characterized by strong energy penetration and uniform heating, it is ideal for large-area edge sealing and applications requiring high airtightness.

In contrast, ultrasonic welding converts high-frequency mechanical vibrations (15–35 kHz) into frictional heat at the interface. Vibrational energy is transmitted via the welding horn to the bonding surface, causing the surface layer of the material to melt rapidly and fuse under pressure—a process of localized heating from the outside in. Its advantages include instantaneous temperature rise, rapid cooling, and the absence of residual heat effects, making it better suited for small components, rigid materials, and rapid spot welding.

In summary: High-frequency welding relies on electromagnetic fields to generate "internal heat" within molecules, whereas ultrasonic welding relies on vibration to generate "frictional heat" at the interface. This distinction—internal versus external heating, and whole-surface versus localized bonding—defines the fundamental difference between the two processes. II. Key Performance Comparison: Material Compatibility, Molding Results, and Application Scope

1. Material Compatibility: Polarity and Flexibility Determine Process Selection

High-frequency (HF) welding is well-suited for polar thermoplastic materials; flexible films such as TPU, PVC, PU, and EVA achieve high weld strength and stable airtightness. Non-polar materials (e.g., PP, PE) are difficult to polarize in an electric field and are therefore unsuitable.

Ultrasonic welding offers broader compatibility, handling most thermoplastics. It excels at joining rigid components like ABS, PC, and nylon. However, when used on ultra-soft, ultra-thin, or highly elastic films, issues such as vibration-induced stress damage, uneven weld marks, and localized dielectric breakdown can occur.

2. Welding Results: Distinct Strengths in Sealing, Aesthetics, and Strength

HF welding produces flat, full weld surfaces free of indentation or wrinkling. It enables integrated edge sealing, embossing, and cutting in a single step. The resulting welds are wide and uniform, offering superior waterproofing, dustproofing, and airtightness—ideal for large-area continuous molding. Drawbacks include a large equipment footprint and strict requirements for mold precision.

Ultrasonic welding creates precise weld points or seams with very short cycle times (0.1–1 second). It causes minimal deformation and requires no cooling time, making it suitable for precision positioning and high-speed assembly lines. However, flexible films may suffer from stress whitening or brittle edge cracking, and long-term flex and weather resistance are relatively weaker.

3. Production and Cost: Efficiency and Yield-Driven

HF welding is ideal for large-format protective film products requiring high sealing integrity and long weld seams. It offers large single-cycle molding areas and stable yields, making it suitable for high-reliability applications in medical, automotive, and outdoor sectors.

Ultrasonic welding is suited for the rapid assembly of small parts involving multi-point welding or short seams. It offers lower energy consumption and faster changeover times, making it ideal for the temporary fixation and simple edge sealing of thin, lightweight consumer electronics components.

III. Protective Film Application Analysis: Process Selection Directly Determines Protective Lifespan

The core value of protective films lies in scratch resistance, wear resistance, weatherability, and sealing performance. Welding quality directly impacts failure modes such as edge lifting, water and dust ingress, and embrittlement or cracking. 1. Ideal Applications for High-Frequency Welding of Protective Films

Fully adhesive flexible protective films, curved screen protectors, and automotive center-console protective films: Require high adhesion, superior sealing, and edge-lift resistance.

Protective films for medical consumables and encapsulation films for new energy components: Require sterility, airtightness, chemical resistance, and long-term stability.

Protective films for outdoor equipment and inflatable structures: Require waterproofing, flex resistance, and tolerance to extreme temperatures.

High-frequency welding enables deep molecular fusion within the film material, resulting in weld seams that match the base material's strength—free from delamination or cracking—perfectly meeting the long-term protection requirements for these films.

2. Scope of Application for Ultrasonic Welding of Protective Films

Better suited for spot-welding/positioning and localized fixing of thin protective films onto rigid substrates, as well as rapid encapsulation where sealing requirements are moderate. When used on ultra-soft, highly elastic, or large-format protective films, vibrational stress can easily cause surface damage or edge failure, making it difficult to ensure consistent yield and stability.

IV. Jidong New Materials TPU Protective Film: Optimized for High-Frequency Welding, Compatible with Ultrasonic Welding

To meet industry demand for protective films that offer high flexibility, high transparency, strong weldability, and weather stability, Jidong New Materials has launched a TPU protective film. Through advanced material formulation and manufacturing precision, it is an ideal choice for both welding processes, delivering exceptional performance—particularly in high-frequency welding.

1. Polar TPU Substrate Optimized for High-Frequency Welding

Jidong New Materials' TPU protective film features a design incorporating polar polymer segments. This ensures rapid molecular response, uniform melting, and strong cohesive forces within a high-frequency electromagnetic field. Post-welding results show no bubbles, cold welds, or whitening; weld seam strength approaches that of the base material, meeting IP67 sealing standards.

2. Stable Thickness Tolerance for Mass-Production Welding

Available in standard thicknesses of 100μm and 120μm with a longitudinal thickness deviation of ≤±3%. This consistency ensures uniform welding energy transfer—preventing dielectric breakdown in thinner areas and incomplete melting in thicker areas—thereby significantly improving production yields. The 100μm variant balances flexibility with a slim profile, making it ideal for curved surfaces and precision electronics; the 120μm variant offers superior strength, suitable for high-durability applications such as automotive, medical, and outdoor use.

3. Balanced Performance Across Scenarios

High light transmission and low haze ensure no impact on display quality or aesthetics;

Resistant to yellowing, aging, and acid/alkali exposure; does not become brittle over long-term use;

Scratch- and wear-resistant surface; features automatic air venting upon lamination—no bubbles or adhesive residue;

Compatible with ultrasonic welding; stable spot welding is achievable with minor parameter adjustments, allowing for shared use across multi-process production lines.

V. Selection Recommendations: Identifying the Optimal Solution Based on Process and Material

For high sealing, large dimensions, high durability, and a smooth finish: Prioritize High-Frequency (HF) welding combined with Jidong New Materials' 120μm TPU protective film—the top choice for automotive, medical, and outdoor applications.

For slim-profile lamination, rapid mass production, and localized fixation: Consider Ultrasonic welding combined with Jidong New Materials' 100μm TPU protective film—suitable for consumer electronics and precision components.

For multi-scenario versatility: Utilize a combination of 100μm and 120μm TPU films, primarily with HF welding and secondarily with ultrasonic welding; this balances sealing performance and efficiency for the best overall cost-effectiveness.

VI. Conclusion

Welding protective films is not merely about "sticking things together"; it is a systematic process involving material, technique, and structural design. Both HF and ultrasonic welding have distinct advantages, and proper selection is the prerequisite for high yield rates and reliability. Centered on its 100μm/120μm TPU protective films—and leveraging polar formulations, consistent thickness, and versatile performance—Jidong New Materials provides standardized, high-performance substrates for HF welding that are also compatible with rapid ultrasonic processes, helping precision manufacturers enhance product quality and reduce total costs.

Looking ahead, as flexible displays, smart automotive systems, healthcare technology, and new energy sectors continue to evolve, protective films will become thinner, stronger, and more reliable. Jidong New Materials remains committed to the deep development of functional TPU film materials, aligning material innovation with advanced welding technologies to provide customers with one-stop solutions for protection and welded forming.