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

["Matt Kaufmann" <mkaufmann@xxxxxxxxxxxx>]

Brian,

if you're talking about flipchip bumps, the current capacity per bump is
limited by electromigration of the thin stackup of metal layers between the
solder bump and the die pad (UBM=Under Bump Metallization).  Different
bumping technologies use different UBM stackups and some are more
susceptible than others so it depends on who is doing your bumping/UBM.

Bascially, the issue is that under HTOL conditions, the current combined
with the temperature will promote electromigration/consumption of the UBM
materials.  If they get consumed, the bump will open.  It also depends on
the size of the bump/UBM pad.

The following factors play into this: junction temp during HTOL testing, UBM
size, life expectancy goal (MTTF).  Bump solder type can also play a role.

K&S (Flipchip Technologies) has a bunch of data that gives max allowable
current capacity per bump as a function of Tj (in order to meet 10,000hr
MTTF).  Depending on the bump pad UBM size, the current capacity can range
from 45mA to 120mA (at Tj=150C) and higher if Tj is lower.  This data is
available on the the K&S web site
(http://www.kns.com/prodserv/flipchip/pdf/design-gde/foc.pdf).

Note: this data is only applicable to the K&S bumping process.  It does not
apply to other bumping processes since they typically use different UBM
systems - although the K&S UBM tends to be on low end of electromigration
resistance - not bad but just less resistant than other UBM systems (K&S or
others may respectfully disagree).


Regards,

Matt

Matt Kaufmann
Principal Engineer - IC Assembly and Packaging Development
Broadcom Corporation
2451 Mission College Blvd.
Santa Clara, CA 95054
408-922-3183(desk)/408-464-9354(cell/pager)/408-922-1023(fax)
mkaufmann@xxxxxxxxxxxx


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Brian Schieck
Sent: Wednesday, February 05, 2003 5:04 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Current capacity of a Solder Ball



All I want is the current capacity.

Consider power delivery

Balls > Plane > Wires or Bumps

If my IC needs 20 Amps DC for core support how many bumps are needed to
supply this? I know the capacity of the ball pads on the bottom
(cu thickness / width / size ). I know a blind via (filled can carry 400 ma)
and I can use multiple vias / ball pad/.
I know the planes can handle more than 20 AMPS. I know if
it is Wirebond each 0.9 mil wire can handle 900 ma. So how much can a ball
carry underrated? I'll figure out what I would like to apply as a derating
i.e. the addition of balls till I'm comfortable with the power delivery.

I want to design quantity of Balls to a real spec. I want to decide my
margin.
I know that 400 ma is bull. Balls can pull AMPS.

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


-----Original Message-----
From: James.Freeman@xxxxxxxxxxxx [mailto:James.Freeman@xxxxxxxxxxxx]
Sent: Wednesday, February 05, 2003 4:30 PM
To: Brian Schieck
Subject: RE: [SI-LIST] Current capacity of a Solder Ball


Hi Brian,
        How are things. Are you looking at a bump or a ball for this info?

Jim Freeman

-----Original Message-----
From: Brian Schieck [mailto:BSchieck@xxxxxxxxxx]
Sent: Wednesday, February 05, 2003 11:13 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Current capacity of a Solder Ball



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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