Copper Clad Laminate Next Hot Spot - HVLP Copper Foils

What is HVLP Copper Foil #

HVLP (Hyper Very Low Profile) is a copper foil with a lower Rz than VLP (Very Low ProfileRz of 3-5 microns), which is 2-3 microns. Ruoxi has found that HVLP is not a common term on the extranet, and is more likely to have originated in Japan. In English, it is more commonly expressed as ULTRA LOW PROFILE COPPER FOIL.

Copper foil roughness has become an important factor affecting conductor losses in high-speed printed circuit boards. Lower roughness copper foils will further reduce signal loss in electronic products.

Especially at frequencies above 50 GHz. At high frequencies, the current tends to flow mainly on the surface of the conductor (skin effect). The current will flow along its contours, incurring additional losses due to the longer propagation path. When the signal is more concentrated on the surface of the conductor, the skin depth decreases, the equivalent resistance of the conductor increases, and problems such as "standing waves" and "reflections" are more likely to occur during transmission, which means that the effect of the surface roughness of the copper foil on the signal loss increases exponentially.

In addition, when a current passes through a conductor, the changing magnetic field induces the formation of additional electric fields (eddy currents). These electric fields are opposite to the "main" current in the center of the conductor. This increases the current density at the surface. This phenomenon is known as the skin effect, and the higher the frequency the stronger the phenomenon. Surface roughness can double conductor losses.

To mitigate this impact, copper foil manufacturers must develop new profile-free products such as HVLP ultra-low profile copper foils, which feel more comfortable with the acronym ULP.

Requirements for higher lamination bonding #

However, when the surface roughness of the copper foil decreases, the bonding between the copper foil and the resin plate is weakened. For laminated copper foils, the bonding at the interface 90% relies on surface structure adsorption and 10% on elemental adsorption. On low-profile or no-profile copper foils, the surface adsorption is greatly reduced. This is particularly difficult for copper foils with a roughness below 1.25 µm. Vacuum deposition technology, on the other hand, is naturally suited for HVLP coatings, where lower interfacial roughness results in better coating adhesion.

by adding nanodots of 5 microns or more to enhance peel bonding. However, these nodules substantially increase insertion resistance.

Therefore, roll-to-roll vacuum coating technology, which has both extremely low surface roughness and high bonding power, is undoubtedly an excellent choice.

In addition, NanoShield roll-to-roll vacuum coating technology can be used for double-sided coating of ultra-thin substrates up to 6 microns. It is suitable for the new demands of high frequency and high speed.

Composite Copper Foil Type and Rz Value #

• Standard ED foil (typical roughness 7-8 μ)
• VLP (Very Low Profile) foils (roughness 3-5 μ); most RTF (Reverse Treated Foils) meet this standard
• HVLP / SVLP / DFF / PF foils (1.5 μ roughness); generally known as "ultra-low profile foils"