Method for processing blind hole by laser

Abstract

The invention discloses a method for processing a blind hole by laser. The method combines fixed point UV laser impulse and UV laser spiral line or concentric circle scanning and is used for one-step blind hole processing or multi-step blind hole processing on multilayer circuit board. The method divides the UV laser blind hole drilling process into two parts, namely a part with an area near the circle center of the blind hole not more than UV laser spot diameter and a part with an area more than the UV laser spot diameter. Fixed point UV laser impulse is adopted to drill the blind hole, so as to remove material in the region with an area near the circle center not more than UV laser spot diameter; then UV laser spiral line or centric circle scanning method is adopted to move outside, so as to remove the material in the region with an area near the circle center more than UV laser spot diameter until meeting set blind hole size; and one-step blind hole or multi-step blind hole processing is drilled by UV laser through two steps or more steps. The method can ensure processing quality consistency of each blind hole, can greatly reduce bottom unevenness of the blind hole, and also can improve margin quality of blind hole processing.

Description

technical field [0001] The invention belongs to the technical field of laser processing applications, and in particular relates to a laser drilling method for blind holes. Background technique [0002] With the development of electronic products towards portability, miniaturization and diversification of functions, the size of printed circuit boards (PCBs) is getting smaller and smaller, thus putting forward higher and higher demands on the miniaturization of circuit boards. One of the keys to improving the miniaturization of circuit boards is the smaller and smaller micro-blind holes between different layers of circuits to meet the requirements of making high-density interconnection and ultra-high-density interconnection printed circuit boards. In order to effectively ensure the electrical connection between layers and the fixation of external devices, in high-speed and high-density PCB design, it is hoped that the smaller the blind hole, the better, so that not only can th...

AI Technical Summary

Problems solved by technology

[0006] (1) When the UV laser beam moves near the center of the circle, due to the small size of the moving track, whether the scanning galvanometer moves the UV laser beam or the working platform moves the workpiece, it will cause the UV laser beam scanning track to be distorted and the scanning speed to drop , resulting in inconsistency in the quality of blind hole processing

[0007] (2) Due to the decrease of the scanning speed of the UV laser beam in the vicinity of the center of the circle, the thermal effect accumulated in the area near the center of the circle will be larger than that of the surrounding area, resulting in the etching depth of the area near the center of the blind hole is also greater than that of the surrounding area, and the difference is generally greater than 20 Microns, resulting in increased unevenness at the bottom of blind vias

If it is ensured that the copper layer at the center of the bottom will not be damaged, there will be residual insulating material around the bottom of the blind hole, resulting in a small contact area between the electroplated copper and the copper layer at the bottom of the hole, and poor adhesion strength, which may cause damage in subsequent processing and use. The poor conduction caused by the fracture and peeling of the electroplated copper layer leads to the failure of laser micro-blind hole processing

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