Unless space is extremely tight you should always over design the power supply traces. That being said, the wider the trace the less the resistance and the more stable the supply voltage at each component. The minimum width traces can be easily used for the supply lines in this design. The minimum trace width allowed by most processes is 4–6 mils.
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. This is obviously much more than we’ll need, and I could have easily made the supply lines much more narrow. Using the calculator linked to above shows that a 1 oz/ft2trace measuring 10 mils wide can actually carry almost 900mA of current. In this tutorial I’ve made the power supply lines 10 mils wide. 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. To determine the required trace width you need to first know the trace thickness for your specific PCB process. To determine the necessary trace width I like to use a PCB trace width calculator. If you run too much current through a PCB trace it will overheat and melt causing the board to become defective. When routing any high current power lines you need to ensure the trace width is capable of carrying the necessary current. Only exceptionally complex designs, that must fit in an exceptionally small space, should likely ever require these more advanced via types. In most situations you should restrict yourself to only using through vias. However, be aware that blind and buried vias drastically increase the prototype cost for your board. Through vias on the other hand consume space on all layers. This is because they don’t take up space on the layers not using them. 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.
Blind vias connect an external layer to an internal layer (so one end is hidden inside the PCB stack-up). Vias that only tunnel through a subset of layers are known as buried and blind vias. 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. Unfortunately, auto-routers in general do a horrible job, and in almost all cases you will need to manually do all of the routing.
#Diptrace pcb layout tutorial manual
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. Once all of the components have been properly placed it’s now time to perform the necessary routing. Most designs will require 4–6 layers, and more advanced designs may require 8 or more 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. But as the circuit complexity increases you’ll find it necessary to add additional layers. 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. The minimum number of conducting layers is two. Conducting layers are separated by insulating layers. PCB Layer StackĪ printed circuit board is made up of stacked layers. Once the transient load disappears the capacitors are recharged by the power supply so they are ready for the next transient increase in load current. Placing them right at the microcontroller’s supply pins allows them to supply any fast, transient current needs of the microcontroller. Remember, capacitors are like little batteries that store electrical charge. Decoupling capacitors are used to solve this problem. So even though the voltage regulator’s output may be a perfect 3.30V, the voltage at the microcontroller pin will be lower during this current surge. If the microcontroller all of a sudden requires a fast spike of current then it will cause a voltage drop across this trace resistor. So this means that if a voltage source is located far away from the load, which is the STM32 microcontroller in this case, there is essentially a resistor between the load and the source (neglecting any capacitance and inductance). Figure 2: Placement of all critical components (U1, U2, J1, and JTAG-1) and passive components (capacitors).
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