FreeLists / si-list / [SI-LIST] Re: Current capacity of a Solder Ball

[Aubrey_Sparkman@xxxxxxxx]

Steve,
Let's assume that all your numbers are correct.  I had the same conclusion
several years ago at a previous company.  We both missed the main point of
Pat's email:  You need to re-think what the limiting factor is.  It's not
immediately obvious.

Aubrey Sparkman 
Signal Integrity 
Aubrey_Sparkman@xxxxxxxx 
(512) 723-3592


> -----Original Message-----
> From: steve weir [mailto:weirsp@xxxxxxxxxx]
> Sent: Wednesday, February 05, 2003 3:07 PM
> To: mchan@xxxxxxxxxxx; BSchieck@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Current capacity of a Solder Ball
> 
> 
> 
> Moses, and Brian, that current number seems low by orders of 
> magnitude.  First, the electrical resistance is way off.   For the 
> resistivity value shown which seems about right at 8X Cu, and 
> a rectangular 
> section 0.2mm X 0.2mm X 0.6mm yields about 0.002 ohms.
> 
> Similarly, the thermal resistance value of 41,000 C/W for a 
> metallic object 
> 24 thousandths thick cannot be right.  Take a small glob of 
> solder the size 
> of a BGA ball on the bench and connect it to a 10V supply and 
> a 100 ohm 
> resistor.  There is no way, that blob will get warm, much 
> less melt.  It 
> will take multiple amperes to melt the foil leading to or 
> away from the 
> ball, and the foil will fail long before the ball.
> 
> Regards,
> 
> 
> Steve.
> 
> At 11:32 AM 2/5/2003 -0800, Moses Chan wrote:
> 
> >Hi Brian,
> >
> >I asked the same question to the list a few months back and got the
> >following answer, below:
> >
> >Solder Ball (63Sn/37Pb) 0.0006 m
> >Ambient Temp. 34 Deg. C
> >Melting Temp. 189 Deg. C
> >Thermal Conductivity 50 W/m-C
> >Electrical Resistivity 0.000000145 ohm-m
> >Thermal Resistance 41026.51161 C/W
> >DC Electrical Resistance 0.297442209 ohm
> >Total Resistance 0.297442209 ohm
> >Power to Melt 0.003778045 W
> >Current to Melt 0.112702164 Amps
> >
> >
> >Moses Chan
> >Vitesse Semiconductor
> >Camarillo, California
> >
> >At 11:13 AM 2/5/03 -0800, Brian Schieck wrote:
> >
> > >Does any one know what the current carrying capacity of a 
> solder ball is?
> > >How is the capacity determined?
> > >Is the capacity derated to account for temperature and voids?
> > >
> > >
> > >for a 60 mil solder ball.
> > >
> > >Brian Schieck
> > >NVidia Corporation
> > >2701 San Tomas Expressway MS B22-221
> > >Santa Clara, California   95050
> > >Direct Phone #  (408) 486-2697
> > >Corp Phone   #  (408) 486-2000 x62697
> > >Local Fax    #  (408) 486-8078
> > >Corp  Fax    #  (408) 486-2200
> > >
> > >Email        bschieck@xxxxxxxxxx
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