Thanks, Inge, GREAT!!!
Gaby
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Sunday, July 05, 2009 12:09 PM
To: [log in to unmask]
Subject: Re: [TN] Weird solder joints
George,
thanks for the nice comment.
Now, Gaby, I've studied the new images you sent to me, and I'm rather sure
about what you've got: blow holes. They occur when built-in humidity or
volatiles have no other way to escape, than by making a tunnel. The vapour
pressure becomes that high. Again, don't bother too much in your case. Read
what this guy says (think it was Wassink, but I'm not sure):
".........Voids (blow holes) are of particular concern with the small rigid
joints associated with BGAs, where the solder ball itself is the joint.
Banks studied the effect of voiding on BGA reliability, and reported that
voids up to 24% of the volume caused no negative effect on reliability. In
fact, joints with voids had 16% better reliability than those without voids.
The cracks that occurred were in the same places whether or not the joints
had voids. ...."
Good Luck
Inge
----- Original Message -----
From: "Wenger, George M." <[log in to unmask]>
To: "TechNet E-Mail Forum" <[log in to unmask]>; "Inge"
<[log in to unmask]>
Sent: Saturday, July 04, 2009 10:13 PM
Subject: RE: [TN] Weird solder joints
Gaby,
Ingemar and Steve have provided good advice.
Ingemar,
Your vast experience with solder assembly and material issues still
manages to amaze me. The only thing I would add is that Steve's idea of
an inclusion in the solder paste may also be the cause. I've looked at
the changing the brightness and contrast of the images and it does
appear that at least on the small2.jpg the dark area does look like a
fibrous inclusion that actually sticks out a short distance from the
solder ball into the cross section potting compound.
Regards,
George
George M. Wenger
Andrew Wireless Solutions
Senior Principal FMA / Reliability Engineer
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 [Office] (732) 309-8964 [Mobile]
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Saturday, July 04, 2009 2:49 PM
To: [log in to unmask]
Subject: Re: [TN] Weird solder joints
Gaby,
solder joints are often expected to be perfect and according to the
school
book, but in the real world they are more or less imperfekt.
Plus:
good geomtry
good wetting
good surface formation
no big dendrites
no big voids
good nickel barrier
good grain structure
Minus
flux inclusions wich have not have time enough to withdraw to the
surface.
I think you have got a too dry paste. I've seen similar solder joints
and
we had no problems. If we had, some boards ought to show up after years
of operation.
I can't see any reason to panic, your solder joints are rather normal.
Do
this: take the polished
crossection samples and put then in a jar with a flux remover. Place the
jar
in a water filled ultrasonic tank and let go for a minute. If the 'dark'
streaks disappear, it's certainly flux.
It's good for all to know how strong and longlasting solder joints can
be
despite numerous 'anomalies' as brother Creswick call them.I've tested
solder joints with up to 50% voids...and they have been nearly as good
as
normal ones. Because the metallurgical properties have been good.
Finally, judging solder joints from light microscope images demands a
very
experienced eye. If I were you , i.e. young and sweet and uncertain ,
I'd
fine polish the samples, etch in a weak solution for a minute and have
them
placed in a SEM. Does not take many minutes to get a safer platform for
determination.
Inge
----- Original Message -----
From: "Gabriela" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Saturday, July 04, 2009 9:54 AM
Subject: [TN] Weird solder joints
> Dear all,
> By cross sectioning BGA solder joints on a failed assembly, I found
that
> the
> suspected joints are not uniform and that they contain unusual
separation
> areas.
>
> I suspect mixed assembly and/or bad reflow profile.
>
> Steve was so kind and enabled me to send the links.
> Please may I have your opinion?
> http://stevezeva.homestead.com/files/small.jpg
>
>
>
> <http://stevezeva.homestead.com/files/small1.jpg>
> http://stevezeva.homestead.com/files/small1.jpg
>
>
>
> <http://stevezeva.homestead.com/files/small2.jpg>
> http://stevezeva.homestead.com/files/small2.jpg
>
> http://stevezeva.homestead.com/files/small3.jpg
>
> <http://stevezeva.homestead.com/files/small4.jpg>
> http://stevezeva.homestead.com/files/small4.jpg
>
>
>
>
> Gaby
>
>
> ---------------------------------------------------
> Technet Mail List provided as a service by IPC using LISTSERV 15.0
> To unsubscribe, send a message to [log in to unmask] with following text
in
> the BODY (NOT the subject field): SIGNOFF Technet
> To temporarily halt or (re-start) delivery of Technet send e-mail to
> [log in to unmask]: SET Technet NOMAIL or (MAIL)
> To receive ONE mailing per day of all the posts: send e-mail to
> [log in to unmask]: SET Technet Digest
> Search the archives of previous posts at:
http://listserv.ipc.org/archives
> Please visit IPC web site
http://www.ipc.org/contentpage.asp?Pageid=4.3.16
> for additional information, or contact Keach Sasamori at
[log in to unmask] or
> 847-615-7100 ext.2815
> -----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text
in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at:
http://listserv.ipc.org/archives
Please visit IPC web site
http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100
ext.2815
-----------------------------------------------------
----------------------------------------------------------------------------
--------------------
This message is for the designated recipient only and may
contain privileged, proprietary, or otherwise private information.
If you have received it in error, please notify the sender
immediately and delete the original. Any unauthorized use of
this email is prohibited.
----------------------------------------------------------------------------
--------------------
[mf2]
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
