Flexible circuit board and manufacturing method thereof

Abstract

A flexible circuit board comprises: a polyimide base material which is provided with at least one through hole penetrating therethrough, and two opposite surfaces of the polyimide base material are formed with grooves; A polyimide conductive film, the polyimide conductive film includes a first polyimide conductive layer positioned on an inner wall of the through hole and a second polyimide conductive layer other than the first polyimide conductive layer, formed on portions of the two opposite surfaces of the polyimide substrate other than the groove and on an inner wall of the through hole; Two conductive wiring layers formed on a surface of the second polyimide conductive layer remote from the polyimide base material, each conductive wiring layer having a wiring opening corresponding to aposition of the groove, wherein a through hole formed with the first polyimide conductive layer has a conductive portion electrically connecting the two conductive wiring layers; Two cover films formed on a surface of the two conductive wiring layers remote from the polyimide substrate, the cover films being filled into the grooves.

Description

technical field [0001] The invention relates to a flexible circuit board and a manufacturing method thereof. Background technique [0002] With the development of electronic products such as smartphones, tablet computers and wearable devices in the direction of miniaturization and multi-function, flexible circuit boards also need to meet the requirements of high density. The modified semi-additive method (MSAP) is a relatively common process for making high-density flexible circuit boards. MSAP adopts the method of laminating ultra-thin bottom copper on the surface of polyimide (PI) substrate, thinning the bottom copper to the required thickness, and then laminating the dry film, using the exposure and development technology to form an electroplated copper layer on the top of the bottom copper, and then Tear off the dry film, and then etch and remove the bottom copper located between the electroplated copper layers. [0003] However, during the etching process of the botto...

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Problems solved by technology

[0003] However, during the etching process of the bottom copper, the sidewall of the electroplated copper layer may also be etched, resulting in an increase in the line pitch and making it difficult to obtain a high-density flexible circuit board

Moreover, since the bottom copper is generally electrolytic copper, and its material is denser than that of electroplated copper, the difference in corrosion rate between the two will cause undercut at the bottom of the copper line, causing the line to be skewed

Furthermore, the surface of the PI substrate has a certain roughness, and the surface of the PI substrate usually forms a seed layer by sputtering to overcome the problem of poor adhesion between the bottom copper and the PI substrate, and the seed layer is used in subsequent It is difficult to remove during the etching process, resulting in residues and the risk of short circuits

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