差别

这里会显示出您选择的修订版和当前版本之间的差别。

--- via [2022/04/18 10:38]
gongyu
+++ via [2022/04/19 12:27] (当前版本)
gongyusu
@@ 行 1: / 行 1: @@
 ## PCB中的过孔
-如果电路不能在一个层面上实现所有的信号走线，就要通过过孔的方式将信号线进行跨层连接，过孔的形式以及孔径的大小取决于信号的特性以及加工厂工艺的要求，可以将过孔类比为生活中的地下通道。根据连接的信号层的设置，过孔主要分为如下三种：
+在[[PCB]]设计中如果电路不能在一个层面上实现所有的信号走线，就要通过过孔的方式将信号线进行跨层连接，过孔是一个用铜或金（或其它导体）覆盖的小孔，过孔的形式以及孔径的大小取决于信号的特性以及加工厂工艺的要求，可以将过孔类比为生活中的地下通道。根据连接的信号层的设置，过孔主要分为如下三种：
-{{ :pcb_47.png |}} <WRAP centeralign> 三种过孔 </WRAP>
+{{ :pcb_47.png |}} <WRAP centeralign> 三种不同的过孔 </WRAP>
   * 通孔（through hole）- 连通了上下两层，上下都可见
   * 埋孔（Buried via）- 在电路板内部，连接电路板内部的两个层，表面上看不到
   * 盲孔（Blind via）- 只有一面能看到，另外一面看不到，该孔将一个表面层的信号连接到内部的某个信号层
-过孔的形状和尺寸也不是随便设置的，它取决于连接的信号的特性以及PCB加工厂的工艺要求。
+过孔的形状和尺寸也不是随便设置的，它取决于连接的信号的特性以及[[PCB]]加工厂的工艺要求。
+过孔和穿孔的[[pad|焊盘]]有点相似，不同之处在于过孔没有裸漏的铜或其它金属，都被[[soldermask|阻焊]]保护着，它们也没有[[pad|焊盘]]用于焊接。过孔的孔径往往比穿孔的焊盘要小很多，不需要在孔里放置任何管脚，只要电流通过即可。
+对于高密度板，跨层连接还有一种方式就是使用'微孔' (‘uvia’).微孔是使用高功率的激光打出来的，而不是采用机械钻孔的方式，使用激光孔会可以让过孔的尺寸大大缩小。
-When you want to move a signal that travels across a trace from one side of a PCB to another (say, from front to back), you can create a via. A via is a hole with its sides covered with copper or gold (or other conductive material), that allows a trace to continue its route across layers.
+{{ :microvia-types.png |}}<WRAP centeralign>几种不同类型的微孔</WRAP>
-Figure 12.6: Vias allow a trace to continue between layers.
-In Figure 12.6, you can see the two sides of the same PCB. On the left, the arrows point to two vias in the front of the PCB, and on the right, the circles indicate the same vias on the back of the PCB. Vias are very similar to through-hole pads, except that they don’t have any exposed copper (they are covered by the solder mask), and they don’t have a pad (so you can’t solder a component).
-In simple circuits with only a few components, it is possible to create all of the traces on one layer of the PCB. When a PCB gets busy with more components it quickly becomes impossible to do the routing on a single layer. When multiple layers are needed, vias provide the simplest method of allowing a trace to use the available board real estate.
-In the Figure 12.7 you can see the types of interconnections between layers that are possible.
-Figure 12.7: Types of interconnections between layers.
-For through-hole components, you would design a hole that connects the top and bottom copper layers. This hole is implemented using a drill. It is wide enough to allow for the pin of the component to go through it.
-Vias are smaller than holes in terms of their diameter. They are not wide enough for pins to go through them, but they are plated, like holes, and they allow for electrical connection between layers to take place.
-A 'through via' is like a hole, but narrower. It connects the top and bottom layers. A buried via is a via that connects any two internal layers. In the four- layer example of Figure 12.7, the buried via connects the In1.Cu and In2.Cu. A 'blind via', also connects two layers, but has one end exposed on to the outside of the board, either top or bottom.
-In high-density boards, another option for interconnecting layers is to use a 'micro via' (‘uvia’). A micro via is made using high-powered lasers, instead of a mechanical drill; the use of lasers makes it possible to dramatically reduce the diameter of the via.