| 摘要 |
<p>A process for establishing durable and reliable contact between different layers of multilayer, preferably four-layer, printed circuit cards. In the four-layer cards which are bonded together and connected by means of borings the two outer layers e.g. the first and the fourth, are used for sign leading and card connection; the inner layers, e.g. the second and the third, are used for earthing and for the supply voltage. The distinctive feature of the process is that the boring connecting the outer, e.g. the first and/or the fourth, and the inner, e.g. the second and/or the third layers are before being metallized, rebored with a greater diameter from the appropriate direction up to the intermediate layer with the help of an electronically controlled bit. During this process the reaching of the intermediate layer is sensed and after having reached the required depth within this layer, the forward movement of the bit is stopped. After having made the necessary number of great diameter borings, their cylindrical jackets and the envelopes of the cones in the conducting layers are coated with copper in the known way. The present invention relates to a device, too, connected with the bore preferably for the process described above. The distinctive feature is that the bit enlarging the diameter of the borings has a device automatically regulating its forward movement, an electronic control and a sensor circuit. The bore (14) is in rigid contact with the controlled, automatic device (15) regulating its forward movement. The controlling input of this device (15) is connected with the output (a) of the electronic controll (16); the input of the electronic control (16) is connected with the output (b) of the sensor circuit (17). This circuit has two inputs, one (c) connected to the bore (14), the other (d) to the inner conducting layers of the multilayer printed circuit (13).</p> |
