![]() The minimum number of conducting layers is two. This means the top layer and the bottom layer can be used for routing signals, and these two layers are separated by an internal insulating layer.įor this tutorial we’ll start with a 2-layer board to keep things simple. But as the circuit complexity increases you’ll find it necessary to add additional layers. The number of conducting layers is always an even number, so you can have a board with 2,4,6,8,10,12 conducting layers. Most designs will require 4–6 layers, and more advanced designs may require 8 or more layers. Once all of the components have been properly placed it’s now time to perform the necessary routing. There are two options for routing: manual and automatic.įor auto-routing in DipTrace you simply select Route -> Run Autorouter and the software will automatically do all of the routing. Unfortunately, auto-routers in general do a horrible job, and in almost all cases you will need to manually do all of the routing. For this tutorial we will be doing all of the routing manually.įigure 4: Via #1 is a classic through via, via #2 is a blind via, and via #3 is a buried via. Vias that only tunnel through a subset of layers are known as buried and blind vias. Buried vias connect two internal layers and are completely hidden on the assembled PCB.īlind and buried vias allow you to pack a design more tightly.īlind vias connect an external layer to an internal layer (so one end is hidden inside the PCB stack-up). This is because they don’t take up space on the layers not using them. Through vias on the other hand consume space on all layers. ![]() However, be aware that blind and buried vias drastically increase the prototype cost for your board. In most situations you should restrict yourself to only using through vias. Only exceptionally complex designs, that must fit in an exceptionally small space, should likely ever require these more advanced via types. When routing any high current power lines you need to ensure the trace width is capable of carrying the necessary current. If you run too much current through a PCB trace it will overheat and melt causing the board to become defective. To determine the necessary trace width I like to use a PCB trace width calculator. To determine the required trace width you need to first know the trace thickness for your specific PCB process. PCB manufacturers allow you to select various conducting layer thicknesses, usually measured in ounces per square foot (oz/ft2) but also measured in mils (a mil is one thousandth of an inch) or millimeters.Ī common conducting layer thickness is 1 oz/ft2. In this tutorial I’ve made the power supply lines 10 mils wide. Using the calculator linked to above shows that a 1 oz/ft2trace measuring 10 mils wide can actually carry almost 900mA of current. This is obviously much more than we’ll need, and I could have easily made the supply lines much more narrow. ![]() Perhaps surprisingly, to handle 120mA we only need a trace width of 0.635 mils! In the first tutorial I showed that the absolute maximum current required by the STM32F042 is 120mA. The minimum trace width allowed by most processes is 4–6 mils. ![]() The minimum width traces can be easily used for the supply lines in this design. That being said, the wider the trace the less the resistance and the more stable the supply voltage at each component. ![]() Unless space is extremely tight you should always over design the power supply traces. ![]()
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