What is the difference between a via and a via pad in a PCB board design?

2019-07-17 Writer: H.C.C. Views: 420

  Both via VIA and pad PAD can perform similar functions in PCB board design. They can all be inserted into component pins, especially for devices in in-line (DIP) packages.

  First, let's talk about the difference: the via is the hole on the PCB, which is usually used for interlayer conduction and can also be used for heat dissipation. The pad is the disk on the via, just like the pad of the inserted device.

  However, in the PCB manufacturing process, their processing methods are different.

  1. How much is the hole in the VIA design, and what is the hole. Then go through the process steps such as sinking copper, and the final actual aperture will be about 0.1mm smaller than the design aperture. For example, the via hole is set to 0.5 mm, and the actual aperture is only 0.4 mm.

  2. The diameter of the PAD will increase by 0.15mm when drilling. After the copper sinking process, the aperture is slightly larger than the design aperture, about 0.05mm. For example, if the design aperture is 0.5mm, the hole diameter will be 0.65mm, and the finished hole diameter is 0.55mm.

  3. VIA will cover green oil in some default PCB processes, which may be blocked by green oil and cannot be soldered. Test points can't be done either.

  4. VIA's welding ring has a minimum width of 0.15mm (in the case of the general process) to ensure reliable copper plating.

  5. The minimum width of the PAD's solder ring is 0.20mm (in the case of the general process) to ensure the adhesion of the pad.

  The via includes a via pad.

  The via holes are also referred to as metalized holes. In the double-panel and multi-layer boards, in order to connect the printed conductors between the layers, a common hole, that is, a via hole, is drilled at the intersection of the wires that need to be connected at each layer. In the process, the cylindrical surface of the hole wall of the via hole is chemically deposited with a layer of metal for connecting the copper foil to be connected in the middle layer, and the upper and lower sides of the via hole are formed into a circular pad shape. The parameters of the hole are mainly the outer diameter of the hole and the size of the hole.

  The via hole can be not only a via hole but also a buried type. The so-called through-hole via refers to the through-hole through all the copper-clad layers; the buried vias only pass through the middle copper-clad layers, as if buried by other copper-clad layers.

  One of the via pads is that the hole metallization penetrates all of the metal layers, and the other is that the surface metal layer has pad formation.

  The above is a detailed explanation of the difference between the via hole and the via hole pad in the PCB circuit board design. Hengtian Weiye is a manufacturer of PCB design + production + assembly one-stop service. If you have any questions, you can consult online customer service or send an idea to Email pcb@china-pcba.com will get answers.

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