How to Optimize Surface Roughness in Stamped Electrolated Copper Products to Reduce Signal Loss?
Publish Time: 2025-11-17
In high-frequency, high-speed applications such as 5G communication, high-speed data centers, and new energy vehicle electronic control systems, signal integrity has become a core indicator in electronic component design. As a fundamental process for key conductive components such as connectors, terminals, and lead frames, the surface roughness of stamped electrolated copper products directly affects signal transmission quality. Especially under high-frequency conditions, the skin effect concentrates current on the conductor surface, and even small surface undulations can significantly increase insertion loss and return loss.1. Why Does Surface Roughness Affect High-Frequency Signals?According to electromagnetic field theory, high-frequency signals propagate in conductors primarily concentrated in an extremely thin surface layer. For example, at 10 GHz, the skin depth of copper is only about 0.66 micrometers. If the surface of electrolated copper products has peaks and valleys, the actual current path will be lengthened, leading to increased resistance, increased dielectric loss, and consequently, signal attenuation, timing distortion, and even increased bit error rate.2. Source Control: Substrate Stamping Precision and Surface PretreatmentThe final surface quality of stamped coated copper products begins with the initial state of the copper strip substrate. During high-precision continuous stamping, die wear, improper lubrication, or release of internal material stress can lead to scratches, burrs, or microcracks on the substrate surface. These defects will be amplified during subsequent electroplating, forming rough protrusions. Therefore, high-gloss dies, optimized stamping clearance and speed, and online cleaning to remove oil and metal debris are necessary. Furthermore, surface activation treatment before electroplating is crucial. Traditional acid pickling easily causes over-corrosion, while using weak alkaline degreasing + micro-etching can uniformly roughen the surface and retain microscopic smoothness, providing a good adhesion foundation for the subsequent dense electroplating layer.3. Refined Control of Electroplating ProcessThe electroplating process is the core stage for reducing roughness. Key measures include:Selecting a high-leveling plating solution system: Adding high-efficiency brighteners and leveling agents to promote grain refinement and surface smoothness;Controlling current density and temperature: Employing pulsed plating or reverse pulse technology to suppress dendrite growth and obtain a denser, more uniform coating;Optimizing anode arrangement and stirring method: Ensuring uniform flow of the plating solution and avoiding rough deposition caused by local concentration polarization;Precisely controlling coating thickness: Too thin a coating cannot cover substrate defects, while too thick a coating easily generates internal stress and particle aggregation; typically, 5–15 μm is optimal.Through the above adjustments, the surface roughness of electroplated copper products can be stably controlled at levels close to mechanical polishing.4. Post-processing and Inspection VerificationAfter electroplating, light chemical polishing or ultrasonic cleaning with deionized water can be performed to further remove surface particles and organic residues. Simultaneously, laser confocal microscopy or atomic force microscopy are introduced to characterize the roughness at the nanoscale, and combined with high-frequency S-parameter measurements using a vector network analyzer, a "roughness-signal loss" correlation model is established to achieve closed-loop process optimization.In the era of high-speed interconnection, stamped electroplated copper products are not only conductive carriers, but also the "tracks" of signal highways. Through the collaborative optimization of the entire process from stamping substrate, pretreatment, electroplating parameters to posttreatment, surface roughness is significantly reduced, which not only effectively suppresses high-frequency signal loss, but also improves product reliability and market competitiveness.
