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May 2005

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Subject:
From:
Vladimir Igoshev <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Vladimir Igoshev <[log in to unmask]>
Date:
Tue, 24 May 2005 10:05:18 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (362 lines)
It's been a lot of e-mails on the issue but do we know where the openings are and how they look. Is there a cross-sectioned view of at least  one of the joints in question?

Regards,

Vladimir
Sent from my Blackberry Wireless 
Vladimir Igoshev, 519-888-7465 ext.5283


-----Original Message-----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Tue May 24 09:57:23 2005
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

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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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