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 >------------------------------------------------------------------ >To unsubscribe from si-list: >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > >or to administer your membership from a web page, go to: >//www.freelists.org/webpage/si-list > >For help: >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > >List archives are viewable at: > //www.freelists.org/archives/si-list >or at our remote archives: > http://groups.yahoo.com/group/si-list/messages >Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu