The so-called spread of copper , is the unused space on the PCB as a datum , then filled with solid copper , the copper area is also known as copper pour . The significance of copper , reducing the ground impedance , improve anti-jamming capability ; reduce the pressure drop , improving power efficiency ; well connected with the ground , reducing the loop area . If the PCB ground more, there SGND, AGND, GND, etc. , it is necessary depending on the PCB board positions , respectively, the most important " place " as a baseline reference to independent laminates , digital and analog ground separately copper from the few words . Meanwhile before the copper , the first bold corresponding power connection : 5.0V, 3.3V , and so on . Thus , the formation of a plurality of different shapes of a deformation structure .
Laminate need to address several issues : First, a single point of connection differently , practices are connected via 0 ohm or beads or inductors ; Second, near the copper crystal , crystal oscillator circuit is a high-frequency emission sources , practices is surrounded by crystal copper , crystal shell then be grounded. Third is an island ( dead zone ) problem , if you feel great , then the definition of a ground vias added to it also can not take much to do.
In addition , a large area of copper-clad laminates good or mesh well , not to generalize. Why? Large copper , if the wave soldering , it could tilt the board , and even blistering. From this point, the grid is better heat dissipation . Usually a high-frequency circuits for interference demanding multi- grid, low-frequency high-current circuit has a circuit full of other commonly used copper shop .
At the start of wiring , grounding respond equally, when traces on the ground should take a good , can not rely on by adding vias to eliminate the copper is connected after the ground pin , this effect is very bad. Of course, if the choices are mesh laminates , these ground connections on some aesthetic impact , if people are careful to delete it.
A large area of copper , with a dual role to increase the current and shielding , pure copper mesh shielding effect is mainly to increase the role of current is reduced. Increase the grid may not be for aesthetic purposes , but can be adhesive foil to prevent and mitigate gas produced when welding copper foil blister , so that a large area of copper , but also pay attention to a few open slots , ease foil blister.
2 , the annular ground , shielding effect can also be formed on the radiation received signal . Similar to the loop antenna , so there are a large current charger both small-signal detection , therefore, is a " tree ground as well .
3 , so that the charge control IC is generally ground to become high-current circuit and another circuit connection is better to reduce the pressure drop foil current loop small signal interference .
To do so, is not absolute, we can see a lot of violations of the requirements above , can also be used , but the general layout of my time , will try to pay attention to these requirements.
1 , the middle layer of the multilayer wiring open area , not copper . Because you make this difficult to achieve copper " well grounded ."
2 , a PCB, no matter how many kinds of power supply is recommended segmentation techniques , and use only one power level . Because the power and ground , just as " reference plane ", the power and ground "good ground " is achieved through a large filter capacitor , there is no filter capacitor place , there is no "ground ."
3 , the device inside the metal , such as metal radiators, metal reinforcing strips , etc., must be achieved " well grounded ."
4 , three-terminal regulator heat slug must be well grounded .
5 , the crystal near ground isolation zone , must be well grounded .
