PCB Board Cloning Reflow Plane

When Cloning PCB Board, Reflow plane’s current density must follow the signal output route from the upside and downside. When the DH ratio reach 5, the current density on the route edge will decrease to 4%; when DH ratio reach 10, the current density will decrease to 1% of the vertical downside; as a result of that, reflow plane’s alternative current basically will be restricted within the area of output signal route which undertake the signals downside when pcb board cloning. That is the reason why we have to consider the feasibility of cut the grounding plane when layout PCB. Furthermore, cutting against the grounding plane can probably cause severe radiation issue, most of the designers will think spare no effort to tackle this problem but normally unable to solve it before the completion of pcb board cloning.

Reference plane’s reflow current will closely follow the corresponding output current after pcb board cloning, consequently as long as the designer is able to keep the sufficient distance among the output current routes, it is possible to avoid the mixture of reflow grounding currents, since these reflow plane current will generate the crosstalk and noise. And all of the lines space we hereby discussed represent the distance among layers; According to the current density formula, designer is capable of calculate the current density in any points on the route edge which is related to the overload output signals after cloning pcb board.

Typical distance “H” can determine undertaking output signal route and reflow plane on the actual position on the pcb board:

If it is reflow plane among the outer layer and inner layer, for example, the typical H value of four and six layers is 75mil;

If the reflow plane is between the two inner layers, then typical H value of four layers is 39mils, and six layers is 14 mils;

Designer must consult PCB manufacturer about the space among each PCB layers after Printed Circuit Board Clone; if the space among the edge of routes can reach or above four times the distance among the input/output signal routes, and crosstalk will reduce to 6% of the signal range.