The meanings and characteristics of these three holes for circuit board.
Conducting holes (VIA), a common type of hole used to conduct or connect copper foil lines between conductive patterns in different layers of a circuit board. For example (such as blind holes, buried holes), but can not insert component lead legs or other reinforced material copper plated holes. Because Printed circuit board is formed by many copper foil layers stacked and accumulated, each layer of copper foil is covered with an insulating layer, so that the copper foil layers can not communicate with each other, and the link of its signal is via, so it has the title of Chinese through hole.
Characteristics are: in order to meet the needs of customers, the circuit board through hole must be fortress hole, so in the change of the traditional aluminum plug hole process, with white mesh to complete the circuit board surface welding and plug hole, so that its production is stable, reliable quality, use more perfect. Conduction hole mainly plays the role of circuit interconnection conduction, with the rapid development of the electronic industry, but also on the printed circuit board manufacturing technology and surface mount technology put forward higher requirements. The through-hole plug hole process is applied and born, and should meet the following requirements:
- There is copper through the hole, welding resistance can not plug.
- There must be tin lead in the conduction hole, there is a certain thickness requirement (4um) shall not be solder blocking ink into the hole, resulting in tin beads hidden in the hole.
- The through-hole must have solder blocking ink plug hole, opaque, no tin ring, tin bead and leveling requirements.
Blind hole: it is to connect the outermost circuit in PCB with the adjacent inner layer by electroplating hole, because you can’t see the opposite side, so it is called blind. At the same time, in order to increase the space utilization between PCB circuit layers, blind holes are used. That is, a through-hole to a surface of the printed board.
Features: The blind hole is located on the top and bottom surface of the circuit board, has a certain depth, used for the connection of the surface circuit and the inner circuit below, the depth of the hole usually does not exceed a certain ratio (aperture). This way of production will need to pay special attention to the depth of the hole (the Z axis) to the right, do not pay attention to words will cause difficult hole plating so almost no factory used, can also be connected in advance to the layer in the individual circuit when the circuit was first drill hole, and then sticking together, but need more precision positioning and contrapuntal device.
Buried hole is the link between any circuit layer inside the PCB but not to the outer layer, is not extended to the surface of the circuit board through the hole meaning.
Features: In this process, drilling after bonding is not possible. Drilling must be carried out at the time of individual circuit layers. The inner layer must be partially bonded first and then electroplated before all bonding can be done. This process is usually used only on high-density circuit boards to increase usable space on other circuit layers.
In PCB production process, drilling is very important, not careless. Because drilling is to drill out the required hole in the copper plate, to provide electrical connection, fixed device function. If the operation is improper, there are problems in the process of hole, the device can not be fixed on the circuit board, light will affect the use, or the whole board will be scrapped, so the drilling process is very important.