Three common drilling holes in PCB production process
In the PCB production process, drilling is very important. Drilling is to drill the required via holes on the copper clad plate to provide electrical connections and fix devices. If the operation is improper, there is a problem in the process of the via hole, and the device cannot be fixed on the circuit board, which will affect the use in the light, and the entire board will be scrapped in the heavy. At present, there are generally three types of drilling processes.
1. Via (VIA)
This is a common type of hole used to conduct or connect copper foil traces between conductive patterns in different layers of a circuit board, but it cannot accommodate copper-plated holes for component leads or other reinforcements.
Features: In order to meet the needs of customers, the through holes of the circuit board must be plugged holes. In this way, in the process of changing the traditional aluminum sheet plugging process, white mesh is used to complete the solder mask and plugging of the circuit board surface, so that the production is stable and the quality is reliable. , it is more perfect to use.
The process of plugging the via hole must meet the following requirements:
1. There is copper in the via hole, and the solder mask can be plugged or not.
2. There must be tin and lead in the via hole, and there is a certain thickness requirement (4um), and no solder resist ink should enter the hole, which will cause tin beads to be hidden in the hole.
3. The via holes must have solder resist ink plug holes, opaque, and must not have tin circles, tin beads, and leveling requirements.
2. Blind hole
The outermost circuit in the PCB is connected with the adjacent inner layer by plated holes. Because the opposite side cannot be seen, it is called blind through. In order to increase the space utilization between the PCB circuit layers, blind holes are applied, that is, to Vias on one surface of the printed board.
Features: Blind holes are located on the top and bottom surfaces of the circuit board, with a certain depth, for the link between the surface line and the underlying inner line, and the depth of the hole usually does not exceed a certain ratio (diameter). This production method requires special attention to the depth of the drilling (Z axis) to be just right.
3. Buried holes
It is a link between any circuit layers inside the PCB but not connected to the outer layer, and it also means a via hole that does not extend to the surface of the circuit board.
Features: In this process, the method of drilling after bonding cannot be used. Drilling must be performed on individual circuit layers. First, the inner layer is partially bonded and then electroplated. Finally, it can be fully bonded, which is more conductive than the original. Holes and blind holes are more labor-intensive, so the price is also the most expensive. This process is usually only used on high-density circuit boards to increase the usable space for other circuit layers.
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