Manufacturing method for circuit board back hole drilling

Abstract

The invention relates to the technical field of printed circuit boards, in particular to a manufacturing method for circuit board back hole drilling. According to the method of the invention, a copperlayer with a thickness smaller than or equal to 10 micrometers is electroplated in a whole-plate electroplating process; compared with a method which electroplates a copper layer at one time to meetthe design requirement of a final product, the method of the invention enables the hole diameter of a first through hole is relatively large during back drilling, and therefore, drilling slag can be guided out from the first through hole, and the amount of drilling slag formed during the back drilling can be reduced, especially, the amount of copper drilling slag can be decreased; the granularityof the copper drilling slag is small, hole blocking caused by large-particle copper drilling slag can be avoided; the copper drilling slag remaining in the hole can be completely removed during alkaline etching, and therefore, a hole blocking risk is reduced, and a reliability hidden danger in the aspect of circuit conduction caused by the fact that the copper drilling slag remains in the hole canbe eliminated. Especially for a first through hole with the hole diameter of 0.15 mm, the thickness of the hole wall copper of the through hole, which is formed by electroless plating copper and whole-board electroplating is controlled to be 5 microns, and a hole blocking phenomenon is avoided, and the problem of hole blocking during the back drilling is completely solved.

Description

technical field [0001] The invention relates to the technical field of printed circuit boards, in particular to a method for manufacturing back-drilled holes on a circuit board. Background technique [0002] For high-layer circuit boards, in order to transmit signals at high speed and meet impedance matching and other issues, it is necessary to achieve mutual conduction between different layers, and high-layer circuit boards are difficult to pass through laser blind holes due to their thick boards. The method of electroplating and filling holes is used to make metallized blind holes. Generally, the function of metallized blind holes is realized by making back-drilled holes through the depth-controlled back-drilling process. Back drilling refers to using a drill to remove the copper layer at one end of the metallized through hole, so that one end of the hole wall in the through hole has no copper and the other end has copper. This process is called back drilling. For micro m...

AI Technical Summary

Problems solved by technology

Using this method to make miniature back-drilled holes, especially for metallized through-holes with a diameter of less than 0.15 mm, the holes are likely to be unsmooth due to the formation of more and larger copper drilling slag during back-drilling. Drilling slag is led out from the hole to cause drilling slag to block the hole, and the drilling slag in the hole cannot be removed during alkaline etching, resulting in the etching potion and the potion in the subsequent wet process remaining in the hole, affecting the quality of the back-drilled hole, and even Lead to scrapping, and the copper drilling slag remaining in the hole will also affect the reliability of the line conduction