Subject: | |
From: | |
Date: | Mon, 8 Apr 96 13:57:01 PDT |
Content-Type: | text/plain |
Parts/Attachments: |
|
|
Andy Pedersen asked about trace with to current capacity requirements.
In addition to Kevin L. Seaman's variables (conductor width, thickness
and current) the board layout has an impact also, in a flex design,
The test folks caused a short (get to blame them _this_ time ;) )
that put 4 amps on a .013 trace. Where the trace was near other
copper, the board survived, but de-laminated in more open areas.
(and we still don't realy know how _long_ it was shorted)
(The trace is still connected & not shorted to any near by traces)
In "Electromechanical Design" by Ronald A Walsh, pg 255, 6.6.10
"Fusing Time-current for copper connections" he quotes an equation
by I.M. Onderdonk:
(let's see if I get this right..)
33(I/A)**2 * S = log10(((Tm-Ta)/234+Ta)+1)
I=A * ((log(((Tm-Ta)/234+Ta)+1))/(33 * S)) **.5
I=current, Ampers, A=conductor area, cir mils, S=time current applied,
seconds, Tm=melting point of copper in dec C, Ta= ambient Temp in deg C.
Has any one used this? I haven't tested it out ( we try to keep the
smoke _in_ the parts don't you know ;) ).
Bill Gaines
AeroJet (for $) IHPVA (for speed & fun)
IEPS (for info) SCCA (for trophys)
[log in to unmask]
|
|
|