Via, through hole, blind hole, buried hole, partial depth hole, countersink hole, back drilling and press-fit hole, is it very dizzy? I will take you to know all kinds of holes in PCB.
PCB via
PCB via is an important part of PCB. It is the electrical connection guide hole between different layers, joined the printed wiring between the layer and the layer together. It is made from the copper precipitation process. Drilling costs usually account for 30% to 40% of PCB board costs. Therefore, when drawing the PCB board, the vias diameter should be larger than 0.25mm, and the pad diameter should be larger than 0.4mm, otherwise the PCB manufacturing cost will be increased.
PCB through hole
PCB through holes(PTH) is the general name of electronic industry for through-hole plug-in components.The metal tube is connected with the top and bottom circuit of the double-sided board through the surface of the copper hole of the circuit board, and connecte the inner layer in multilayer PCB. PTH holes are relatively inexpensive because of their larger diameters. The disadvantage is that it takes up a lot of effective space. A large number of dense through-hole occupy the trace space and obstacles the layout of inner layer. They pass through the surface of the power supply and the ground layer, and also destroy the impedance characteristics of the power ground layer, causing the power ground wire layer to fail.
PCB blind via
The blind via connect PCB outer circuit and inner layer for electro connection, and it can not see the opposite layer through the via, so it is called blind via. In the PCB design, although the pad and via diameter has been gradually reduced, if the PCB thickness does not decrease proportionally, the aspect ratio of the through hole will increase. The aspect ratio of the through-hole will result in insufficient copper deposition in the hole, thereby reducing product reliability. With the maturity of advanced laser drilling technology and plasma dry etching technology, The blind holes and burial holes of small aperture have come into being. If these non conducting apertures are 0.3mm, the parasitic parameters are about 1/10 of the original conventional holes, and the reliability of PCB is improved. In the production of PCB, special attention should be paid to the depth of drilling (Z axis) to be right, otherwise it will cause electroplating difficulties in holes. Drill the hole in the individual circuit layer in advance before drilling the circuit, and finally press it again. More precise positioning and alignment devices are needed.
PCB buried via
The buried hole is connected to any circuit layer inside the PCB but not through to the outer layer. Due to the use of non through hole technology, large holes in the PCB are few, thus providing more space for the routing. The remaining space can be used for large area shielding to improve EMI/RFI performance. At the same time, more residual space can also be used for shielding the inner part of the device and the key network line, so that it has the best electrical performance. The use of non through holes can make the pin out of the device more convenient, making the high-density pin devices such as the BGA package easy to wire, shorten the length of the connection, and meet the timing requirements of the high-speed circuit. In the manufacturing process of PCB, blind hole is made by partical vias electroplating in the inner layer. Finally,press with the outer layer and re drilling,it is more complex than the through hole, and the increase of the laminates leads to the high price of the blind hole.
PCB hole partial depth drill
Partial depth drill is drilling without through the circuit board to control certain depth. There are many kinds of depth drilling hole. Generally, drill holes are controlled by mechanical drills to control the height of spindle drills. There are mechanical blind holes, back drills, etc., and some are controlled by depth milling. The mechanism is almost the same.
PCB countersink hole
The head part of the fastener or completely immersed in the hole of the PCB is called the countersink hole. The countersunk hole of the PCB board is mainly used to make all the boards of the circuit board guide and fix parts. PCB is very strict in the depth and size of the countersunk hole, and its size should be limited to the tolerance area.
PCB back drilling
A back drilling hole is a hole controlled by a mechanical, which removes the copper plating of PTH hole stub that does not need to be guided and interferes with the signal, retain copper hole plating that needs to be used to guide the hole copper. The design principle of back drilling: Analysis of the characteristics of signal transmission from the hole angle. If it is designed as a through hole, the loop signal will be transmitted. The existence of a through hole can easily cause signal transmission, scattering and other problems, resulting in signal disturbance and distortion. When drilling the excess hole copper, the signal is returned according to the original path, which can cancel the inductance generated by the path signal and reduce the distortion of the signal to the greatest extent.
PCB press-fit hole
PCB press-fit holes refers to those holes that need not be soldering and can be directly inserted into components.hole size tolerance is more stringent than the general tolerance, the conventional tolerance of press-fit hole is +/-0/05mm, some of which can even reach +/-0.025mm, and most of press-fit holes are standard pin foot.