High-frequency glue-free double-sided flexible copper clad laminate and preparation method thereof

Abstract

The invention discloses a high-frequency glue-free double-sided flexible copper clad laminate, which comprises an upper layer copper foil, a lower layer copper foil and an insulating layer sandwichedbetween the two copper foil layers, wherein the insulating layer is a PTFE / PI / PTFE composite film comprising a thermosetting polyimide resin film positioned in the middle and a modified fluororesin PTFE positioned on the upper side and the lower side of the thermosetting polyimide resin film PI. The invention further provides a preparation method of the high-frequency glue-free double-sided flexible copper clad laminate, wherein the preparation method comprises a coating process and a pressing process. According to the present invention, the PI film is subjected to plasma surface treatment toatomize the surface so as to increase the adhesion force after the hot pressing, and the roughness of the copper foil is low, such that the prepared copper clad laminate has characteristics of good peel strength, low impedance, low dielectric constant, low dielectric loss and low signal loss.

Description

technical field [0001] The invention relates to the field of printed circuit boards, in particular to an adhesive-free double-sided copper-clad laminate, especially a high-frequency adhesive-free double-sided flexible copper-clad laminate and a preparation method thereof. Background technique [0002] With the accelerated development of 5G communication, millimeter wave and aerospace military industry, the demand for high-frequency and high-speed FPC (flexible circuit board) / PCB (printed circuit board) business is coming. Popularization, rapid processing and transmission of information has become the focus of the communication industry. In the field of communications, the future 5G network will have higher bandwidth than 4G, more dense micro-base station construction, and faster network speed. In response to the needs of the Internet of Things, cloud computing, and various broadband communications in the new era, the development of high-speed servers and mobile phones with ...

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Problems solved by technology

[0007] (4) Low water absorption and high water absorption will affect the dielectric constant and dielectric loss when it is damp. The DK value of water is as high as 70. Reducing the water absorption of materials is the main problem facing high-frequency materials at present;

[0009] However, the high-frequency copper-clad laminates currently used in the industry are mainly LCP (liquid crystal polymer) copper-clad laminates, PTFE (polytetrafluoroethylene) copper-clad laminates, and modified MPI (thermoplastic polyimide film) copper-clad laminates; among them , LCP films are plagued by insufficient output and low yields and cannot be mass-produced. Currently, only Japan’s Kuraray has relatively mature technology for LCP films. In addition, although LCP copper clad laminates have a relatively perfect dielectric constant (Dk) / dielectric loss (Df) characteristics, but its products have problems such as poor mechanical properties and insufficient adhesion

The PTFE (polytetrafluoroethylene) copper clad laminate is divided into two types. One is a copper clad laminate combined with a single PTFE film and copper foil. This method requires the addition of inorganic silicon due to the large thermal expansion coefficient of the PTFE film and insufficient dimensional stability. This will affect its mechanical properties. The other is to falsely paste the PTFE film cut piece and the PI film, and then bond it to the copper foil. This method needs to be falsely pasted between the films, which is easy to cause wrinkles and air bubbles. And other appearance problems, which in turn affect its peel strength, and sheet lamination, yield and efficiency are low; modified MPI (thermoplastic polyimide film) copper clad laminate, the MPI film is provided by Zhongyuan Chemical, mainly Improve PI water absorption, reduce DK value, its processability is more convenient, but the high frequency and low loss performance is worse than LCP copper clad laminate and PTFE copper clad laminate

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