Good Morning Kerry,
I've seen a similar incidence with respect to some mBga's we
were assembling. Same scenario as yours, the board would fail and then
pass with some "manual pressure".. Sometimes the boards would pass then
fail in the field after a couple of months. We beat ourselves up about
the profile and tried both RTS & RSS but nothing seem to make a
difference.
Now I don't see whether you stated if the bga was plastic or
ceramic. This could be a factor with respect to a TCE problem. In my
case I sent the boards out to a lab who performed a Die/Pry test. The
test showed that micro fracture were occurring because of the delta in
expansion rates. The fix was introducing underfill to the process and
the problem hasn't occurred since (2yrs). Hope this helps.
Mike Laroe
Process Engineer
Cirtronics Corp
(603)249-9190
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dehoyos, Ramon
Sent: Tuesday, May 24, 2005 9:57 AM
To: [log in to unmask]
Subject: Re: [TN] BGA Intermittent
Hi Kerry:
Too much of a soak time will burn off the resin. What type of
profile is it being used, RTS ( ramp to spike ) or RSS ( ramp soak and
spike )? Can you share the profile temps and chain speed?
Regards,
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Black, Paul
Sent: Tuesday, May 24, 2005 9:11 AM
To: [log in to unmask]
Subject: Re: [TN] BGA Intermittent
Kerry,
We are currently experiencing the same type of failure with a smaller
BGA, and hired an outside firm to run a battery of tests. The conclusion
that I received yesterday was that the BGA is probably failing due to
resin starvation. The way it was explained to me is that, during the
press curing of the device, too much resin may have been forced out of
it, resulting in voids in the dielectric layer. This causes stress on
the BGA substrate vias and can lead to fractures within the internal
Copper traces.
This has not been confirmed yet by the manufacturer, but it's something
you might want to keep in mind.
Thank you,
Paul Black
Manufacturing Engineer
Kronos
E-mail: [log in to unmask]
Voice: (978) 947-1520
Fax: (978) 244-0568
www.kronos.com
Improving the Performance of People and Business(tm)
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Kerry McMullen
Sent: Tuesday, May 24, 2005 8:17 AM
To: [log in to unmask]
Subject: Re: [TN] BGA Intermittent
Hi Leo,
If pressure is applied to the part, the part functions (passes data).
When the slight finger pressure is let off, the part fails (no data
passes).
Leo Higgins <[log in to unmask]>
05/23/2005 05:31 PM
To
"'TechNet E-Mail Forum'" <[log in to unmask]>, "[log in to unmask]"
<[log in to unmask]>
cc
Subject
RE: [TN] BGA Intermittent
Can you define what you mean by "intermittent"? Does this mean
measurements on the same board show proper functionality but repeated
measurements show that improper operation is sometimes noted? How is
this measured....some form of ICT?
Best regards,
Leo
Director of Applications Engineering
ASAT, Inc.
3755 Capital of Texas Highway, Suite 100
Austin, Texas 78704
ph 512-383-4593
fx 512-383-1590
[log in to unmask]
www.asat.com
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Kerry McMullen
Sent: Monday, May 23, 2005 1:01 PM
To: [log in to unmask]
Subject: Re: [TN] BGA Intermittents
Hi Paul,
I am going to check now. We have not had the problem before.
Kerry
Kerry McMullen
Principal New Product Mfg. Engineer
LTX Corporation
50 Rosemont Road
Westwood, MA 02090-2306
(T) 781-467-5468
Paul Edwards <[log in to unmask]>
05/23/2005 01:40 PM
To
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask] cc
Subject
RE: [TN] BGA Intermittents
Kerry,
What size are the BGA pads and balls?
Paul Edwards
Process Engineering
[log in to unmask]
Tel: 408-433-4700
FAX: 408-433-9988
Surface Art Engineering
81Bonaventura Dr.
San Jose, CA 95134
DUNS: 944740570
CAGE/NCAGE: 1XZ48
-----Original Message-----
From: Kerry McMullen [mailto:[log in to unmask]]
Sent: Monday, May 23, 2005 10:31 AM
To: [log in to unmask]
Subject: Re: [TN] BGA Intermittents
Hi Technetters,
Typing too fast.
Balls are 63/37. Ball temperature near the middle balls measured by
thermocouple is 206 Degrres C. I do not want to go any higher as I
might damage some of the other components on the board. The board is
12" x 12"
double sided. I'm not sure if the design engineers are creating a
fire
drill here, or not. First they say its the middle. Today it is the
corners. The boards pass x-ray (non-oblique). The boards have not
warped at all. Very balanced board both in layer thickness and Cu
dispersion. The only thing I have not found is the surface finish on
the BGA substrate.
I doubt it is the profile.....
Thanks in advance for your help.
Kerry
Bev Christian <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
05/23/2005 01:21 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to Bev Christian
<[log in to unmask]>
To
[log in to unmask]
cc
Subject
Re: [TN] BGA Intermittents
Kerry,
Pure tin balls?! I have not heard of that before. Pure tin melts
considerably higher than SAC alloys. Hmm, 206C you say, 14 layer board?
It is quite possible that your temperature/time is not enough to get a
significant amount of diffusional mixing of the solder paste and the
balls. But then you mention intermittents at the corners as well as the
center.
Two other possibilities are warping of the part (but would expect that
to give you intermittents in one or the other area, not both) or there
is a severe problem with the construction of the component itself and
there is internal damage to the component.
You don't say, but I presume the board itself solders well and there are
no other soldering problems on the board that would lead you to suspect
the solder paste?
Bev
RIM
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Kerry McMullen
Sent: May 23, 2005 1:10 PM
To: [log in to unmask]
Subject: [TN] BGA Intermittents
Hi Technetters,
I have a 1089 BGA with Sn balls.
Paste is 63/37 SnPb
Board is 14 layer, .098 thick Immersion Ag.
Ran thermocouples. Inner balls are seeing 206 degrees C.
What could be causing intermittents at the center and corners of the
BGA?
Thanks,
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