[SI-LIST] Re: Current capacity of a Solder Ball
- From: Pat Diao <Pat_Diao@xxxxxxxx>
- To: "'cclewell@xxxxxxxxxxxxxx'" <cclewell@xxxxxxxxxxxxxx>,si-list@xxxxxxxxxxxxx
- Date: Wed, 5 Feb 2003 12:32:03 -0800
Brian,
As Craig mentioned below, it is the "something" above and below the solder
ball that is the determiner of solder ball current capability.
Above the ball, it is usually the substrate or circuit tape. Other than the
BT or other di-e material, it is really the direct Cu connection to the ball
(ball pad, trace, vias) which conducts heat away from the ball. Same thing
can be said on the PCB, the Cu traces carry the heat away from the ball.
Therefore to calculate the solder ball current capacity, it is really
requiring the calculation of everything around it. And to make the matter
worst, the substrate side is usually hotter than the PCB and balls due the
the heat source on the chip, which greatly reduces or eliminates the
"upward" heat conduction.
Considering most of the substrate and PCB structures, we usually try to keep
the current below 400 mA per ball. For individual package structures it can
certainly go lower, just like Moses's example below. Use a conservative
approach, put some more power/gnd balls as they also help with electrical
performance.
Pat Diao
ASAT Inc.
Fremont, CA
-----Original Message-----
From: Clewell, Craig [mailto:cclewell@xxxxxxxxxxxxxx]
Sent: Wednesday, February 05, 2003 11:49 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Current capacity of a Solder Ball
Brian,
I would think that the solder ball must attach to something and that
something more than likely has a current carrying capacity. Would it help
if you thought of the ball + something as a system and obtained the rating
for the said something?
Craig
-----Original Message-----
From: Moses Chan [mailto:mchan@xxxxxxxxxxx]
Sent: Wednesday, February 05, 2003 2:33 PM
To: BSchieck@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Current capacity of a Solder Ball
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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