Secondary production method for semi-metallized holes in PCB circuit boards

Secondary production method for semi-metallized holes in PCB circuit boards

Double routing method

  Design method: The idea of this method is to use a large-diameter routing knife to first routing the routing groove at the semi-metalized hole after photosensitive soldering. Then use a small-diameter routing knife to repair the remaining breakpoints, and then go through the surface treatment process, and then re-routing the entire shape. We call it the second routing method. In the past, routing knives with a minimum diameter of 1.0 mm have been developed, and routing knives with a diameter of 0.80 mm and a diameter of 0.50 mm have been developed, making the secondary routing method a feasible method.

Production Process:

  1. Alkaline etching process: plate → drilling → PTH → outer layer pattern transfer → pattern plating

  2. Acid etching process: plate → drilling → PTH direct thickening hole copper → outer layer pattern transfer → acid etching → photosensitive solder resist → one routing surface treatment → character printing → Routing shape

Processing effect: First, use a routing knife with a larger diameter to machine a routing groove with a semi-metalized hole. At this time, most of the piercings appeared at the section B. In this way, we flipped the PCB board and used the 0.80mm diameter and 0.50mm diameter routings to repair the piercing at B.

The following is the data of 160 jigsaw units to compare the two diameters of routings and knives to improve the front. (One piece per stack)

Analysis of advantages and disadvantages: From the processing effect, the result of the second routing method is satisfactory. However, the processing efficiency of this method is too low. The same routing groove must be walked twice, and the speed of the small routing knife is very slow. The production of two pieces per stack is prone to breakage. The actual production also needs to consider the cost. The price of the routing knife with a diameter of 0.50mm is 4- 5 times, the service life is only 1/3. As part of the drape may be pressed into the semi-metalized hole when the routing is used for the routing, it is necessary to consider carefully in the routing design. In the process of routing board, pay attention to avoid scratching the copper surface of PCB board as much as possible, and the routing machine should be clean before use. To sum up, the second routing method is only suitable for a small number of prototype production, and the cost and production cycle are undoubtedly the fatal bottleneck in mass production.