Let's first introduce the common boreholes in PCB: through hole, blind hole and buried hole.The meaning and characteristics of these three holes
Through hole (VIA), a common hole used for conducting or connecting copper foil lines between conductive drawings in different layers of the circuit board.For example (such as blind and buried holes), but can not insert copper plated holes of assembly legs or other reinforcing materials.Because the PCB is formed by the accumulation of many copper foil layers, each layer covers an insulation layer, so that the copper foil layer can not communicate with each other, and the link of its signal depends on the through hole (via), so there is the title of Chinese through hole.
Features are: in order to meet the needs of customers, the guide hole of the circuit board must be the plug hole, so that in the change of the traditional aluminum sheet plug hole process, with white net to complete the circuit board surface resistance welding and plug hole, so that its production is stable, reliable quality, more perfect use.The guide hole mainly plays the role of circuit mutual connection. With the rapid development of the electronic industry, it also puts forward higher requirements for the printed circuit board production process and surface mounting technology.The process of conducting the plug hole is applied, and at the same time should meet the following requirements: 1. There is copper in the plug hole, and the welding resistance plug is not plug.2. Tin lead must be found in the guide hole, and certain thickness requirements (4um) shall not prevent welding ink into the hole, resulting in hidden tin beads in the hole.3. The guide hole must have a welding resistance ink plug hole, no light penetration, no tin ring, tin beads and leveling requirements.
Blind hole: the outer layer circuit in the PCB is connected to the adjacent inner layer with an electroplating hole, because you can not see the opposite side, so it is called a blind pass.At the same time, in order to increase the space utilization between the PCB circuit layer, the blind hole is applied.That is, the guide hole to a surface of the printed plate.
Features: The blind hole is located on the top and bottom surface of the circuit board, with a certain depth, for the surface line and the lower inner line link, the depth of the hole usually does not exceed a certain ratio (aperture).This way of production needs to pay special attention to the depth of drilling (Z axis) to just right, do not pay attention to will cause hole electroplating difficulties so almost no factory, can also need the connected circuit layer in individual circuit layer first drilling hole, finally bonded, but need to be more precise positioning and alignment device.
The buried hole is the link between any circuit layer inside the PCB but is not connected to the outer layer, and also the conductive hole that does not extend to the surface of the circuit board.
Features: in this process cannot be achieved by using the adhesion after the drilling method, must be drilled in the individual circuit layer, the first local adhesion to the inner layer after the first plating treatment, and finally all adhesion, than the original guide hole and blind hole to take more effort, so the price is also the most expensive.This process is usually used only on high-density circuit boards to increase usable space for other circuit layers
In the PCB production process, drilling is very important and cannot be careless.Because drilling is the required hole on the copper plate to provide electrical connection, the function of the device.If the operation is improper, there are problems in the perforation process, the device can not be fixed on the circuit board, light will affect the use, heavy, the whole board should be reported to waste, so the drilling process is quite important.
