Preparation method for HDI rigid-flex PCB interlayer blind hole all-copper filling

Abstract

The invention provides a preparation method for HDI rigid-flex PCB interlayer blind hole all-copper filling, comprising the following steps: (1) preparing a double-sided copper-clad board and reducing copper on one side of the double-sided copper-clad board; (2) preparing an inverted trapezoidal blind hole in the copper-reduced side of the double-sided copper-clad board through laser drilling; (3) cleaning the wall and bottom of the blind hole and removing residue left on the wall and bottom during hole drilling; (4) depositing a metal copper layer on the surface of the wall and bottom of the blind hole; and (5) filling the blind hole deposited with the metal copper layer with copper to realize interlayer interconnection of the HDI rigid-flex PCB. Compared with the prior art, HDI rigid-flex PCB interlayer blind hole all-copper filling is realized, the interlayer connectivity of the blind hole is ensured, the wiring density of the HDI rigid-flex PCB is improved, the cost of equipment investment is reduced, and the production efficiency and production benefit are improved.

Description

technical field [0001] The invention relates to the technical field of HDI rigid-flex boards, in particular to a preparation method for filling blind holes between layers of HDI rigid-flex boards with full copper. Background technique [0002] With the increasing integration of electronic devices, especially the continuous development of wearable devices, higher requirements are put forward for HDI rigid-flex boards. HDI rigid-flex board refers to a printed circuit board with one or more rigid regions and one or more flexible regions, and the rigid-flex regions can be interconnected arbitrarily. To realize any interlayer interconnection in the HDI rigid-flex board, the HDI rigid-flex board must contain blind holes, so the preparation and filling of blind holes between HDI rigid-flex boards is one of the most critical steps. At present, the filling of blind holes between layers of HDI rigid-flex boards uses CO 2 Laser drilling, then copper sinking, copper plating, and final...

AI Technical Summary

Problems solved by technology

[0009] However, the full copper filling of interlayer blind holes in HDI rigid-flex boards has not yet been published in relevant reports, because the interlayer blind holes in HDI rigid-flex boards are distributed in rigid areas, flexible areas, and rigid-flex areas. The full copper filling of blind holes has different difficulties, especially in the rigid-flex joint area

In the rigid-flexible area, the blind holes have different media (usually containing FR4, PI and adhesives and other media), and the blind holes are mostly laser drilled, while metal copper, FR4, PI, and adhesives are not suitable for laser drilling. The hot-melt characteristics of the two are different, so the hole type is complex, and the roughness of the hole wall is very different. At the same time, because the thickness of the rigid zone is usually relatively large, while the thickness of the flexible zone is small, the thickness-to-diameter ratio distribution is wide, and the thickness of the hole is relatively large. Blind hole filling potion with diameter ratio is not easy to reach the bottom of the hole, and phenomena such as hole sealing and encapsulation are prone to occur during hole filling, while blind holes with small thickness-to-diameter ratio are usually small due to the small difference between the inside and outside of the hole. Bottom-up hole-fill patterns cannot be formed

Therefore, due to the above-mentioned complex characteristics of the blind holes in the rigid-flex joint area, it is obvious that the difficulty of full copper filling of the rigid-flex joint board is greatly increased, and the further development of the HDI rigid-flex joint board is hindered.

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