RE: [PROTEL EDA USERS]: Via size

[Heiko Vachek <Vachek@elektronik21.de>]

Still one more comment:
If I have not enough space and still have high current on vias, I convert
them to pads which will not be covered by solder stop. If the board features
HAL (hot air leveling) and / or is wave soldered, there will be an
additional tin plating or even fill. In cases of supply lines with 50mA < I
< 1A I normally use this converted kind of vias with a diameter of 50 mil
and a hole size of 0.7mm (28mil).

Heiko
 
Abd ul-Rahman Lomax wrote:
> One more comment.
> 
> At 04:48 PM 9/11/00 -0400, Hans wrote:
> >Hi group,
> >
> >  I was wondering if there are any specific guidelines in 
> setting the via
> >size. The bigger the via, the more current can go through ... but the
> >gain in cross-sectional area only goes up slightly with increasing
> >diameters. Any thoughts on this?
> 
> What Hans said about the gain in area was not true. The copper 
> cross-section of the via varies roughly with the diameter of 
> the hole; 
> double the hole and you double the copper cross-section. To 
> be more exact, 
> it could be said that doubling the hole size will almost double the 
> cross-sectional area.
> 
> Given a via with hole diameter H and plating thickness in the 
> hole T (the 
> hole is drilled H + 2 * T and then plated):
> 
> the copper cross-sectional area A = PI*(H+2*T)^2 - PI*H^2 
> (this is the area 
> defined by the outer circumference of the copper less the 
> area of the hole 
> itself, which has a rather high resistance.... :-); this simplifies to
> 
> A = PI*T*(H+T) or PI*H*T(1+T/H)
> 
> So if H >> T, A ~ PI*H*T, that is, the area approaches the 
> circumference of 
> the hole times the plating thickness.
> 
> And if H = 0, A = PI*T^2, which is the area of a circular 
> plugged hole with 
> radius T. (You have to use the first equation to avoid 
> dividing by zero....)
> 
> marjan@vom.com
> Abdulrahman Lomax
> P.O. Box 690
> El Verano, CA 95433
> 
> 
> 
>