![]() ![]() Microvias are tiny vias that are usually characterised by a diameter of 150um or less (this is the formal IPC definition). NinjaCalc (which can be used for free from here) has a via current calculator.Ī drilled-out via (to break the connection) between a 0603 resistor and SOT-23-3 MOSFET. Since PCB material is more thermally conductive than air, this rule is on the safe side. This does not take into account the difference between an external track and a via which is surrounded by PCB material. This assumes that the via wall is the same thickness as the copper track (e.g. The above rule-of thumb stems from the fact that when a via wall is unrolled into a 2D track shape, it would be \(\pi \cdot d\) wide ( \(c = 2\pi r\)), where \(\pi\) is approximately equal to 3. Current-Carrying AbilityĭESIGN TIP: As a rule of thumb, a via with a certain diameter can carry 3 times as much current than a track with the same width. ![]() Vias are simply the name given to plated holes which are used to connect to tracks on different layers rather than to mount through-hole components (remember that holes are primarily used to mount through-hole components, but also can connect tracks on different layers). The middle pad in the image below shows this.ĭiagram showing different ratios between hole and pad size. A typical rule-of-thumb is to make the pad diameter twice the size of the hole diameter. This allows a good solder bond between the component and the PCB tracks. Holes which are designed for component leads to go through require pads surrounding the holes on the top and/or bottom of the PCB. The smallest hole PCB manufacturers can support is usually 0.1-0.2mm, with anything under 0.2mm becoming specialty and hence more expensive. Most PCB manufacturers will have a pricing regime that is dependent on the smallest hole size used, the total number of holes, and also the number of different hole sizes. Holes with copper rings have to obey the minimum annular ring size clearance. Holes are typically plated (which makes them identical to vias), but non-plated also have their uses (e.g. Holes in PCBs are typically used to mount through-hole components (their main use), and to provide places to secure the board mechanically. How To Calculate The Thermal Resistance Of Holes And Vias. ![]()
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