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June 2009

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Subject:
From:
Genny Gibbard <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Genny Gibbard <[log in to unmask]>
Date:
Mon, 15 Jun 2009 09:11:19 -0600
Content-Type:
text/plain
Parts/Attachments:
text/plain (338 lines)
Sorry, pretty much in the center of the board. 


Genny Gibbard, P. Eng 
Manufacturing Engineer, Vecima
PTS dept. x.4229 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Reuven Rokah
Sent: June 15, 2009 1:34 AM
To: [log in to unmask]
Subject: Re: [TN] Corner ball pad cratering

My guess is that the BGA component is located at the PCB corner (not at
the center).
Pls confirm (or not).

Best Regards

Reuven ROKAH
e mail: [log in to unmask]
P Think green before printing this mail... Thanks


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Tan Geok Ang
Sent: Monday, June 15, 2009 4:07 AM
To: [log in to unmask]
Subject: Re: [TN] Corner ball pad cratering

RoHS materials with board thickness less than 90mils? 
Any heatsink attached on the BGA? 
Might want to look into design.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Reuven Rokah
Sent: Sunday, 14 June 2009 2:15 PM
To: [log in to unmask]
Subject: Re: [TN] Corner ball pad cratering

Check handling problem causes a PCB warpage near the BGA (after reflow).

Best Regards

Reuven ROKAH 
e mail: [log in to unmask]
P Think green before printing this mail... Thanks

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Sunday, June 14, 2009 6:34 AM
To: [log in to unmask]
Subject: Re: [TN] Corner ball pad cratering

 Hi Gaby,
That is exactly what I have been talking about.
Werner


 


 

-----Original Message-----
From: Gabriela <[log in to unmask]>
To: [log in to unmask]
Sent: Sat, Jun 13, 2009 5:01 pm
Subject: Re: [TN] Corner ball pad cratering










We had similar problems.
As you too, I saw it much more in ROHS applications.
And why not be frank-I will tell you what happened next:
Production did not  believe total loss, BGA's went through re-reflow-
for
nothing ( oh, sorry, more cratered pads), removal (more cratered pads),
Lifted pads after removal, Pad repair on those we SAW, NEW BGA
soldering,
failure again,due to pad/via open because the lifted pads separated from
the
connectors (seen by X-ray).
Blabbering? Because I was and am FURIOUS!!!!!
SAC!!phui!
Gaby

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir Igoshev
Sent: Friday, June 12, 2009 9:51 PM
To: [log in to unmask]
Subject: Re: [TN] Corner ball pad cratering

I wouldn't be surprise if some of the joints are also partially cracked
right after re-flow. That is what I saw in the case I mentioned
yesterday.

In fact it was rather unusual to see partially craterred pads under
partially cracked balls.

As far as I know, my customer still tries to convince their CM to change
the
re-flow profile (the cooling rate they used was way too high, but
they've
never admitted that).

Regards,

Vladimir
SENTEC
SENTEC
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (416) 899-1882
Fax: (905) 882-8812
www.sentec.ca


-----Original Message-----
From: Bev Christian <[log in to unmask]>

Date:         Fri, 12 Jun 2009 13:35:13 
To: <[log in to unmask]>
Subject: Re: [TN] Corner ball pad cratering


Chris,
We do extensive cross-sectioning to qualify any new reflow process and
all new Blackberry models. I have never, ever seen a pad cratering event
at this juncture - only after dropping during testing or from field
returns.
Bev

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Mahanna
Sent: Friday, June 12, 2009 1:26 PM
To: [log in to unmask]
Subject: Re: [TN] Corner ball pad cratering

Genny and Bev,
Out of curiosity- are you sure that the cratering was not: induced
thermally (during reflow cool down), but did not manifest itself as a
problem until other mechanics came into play?
It just seems like that would be more common.
Chris

Chris Mahanna
Robisan Laboratory



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Genny Gibbard
Sent: Friday, June 12, 2009 12:12 PM
To: [log in to unmask]
Subject: Re: [TN] Corner ball pad cratering

As always, Steve, you are a wealth of information.  That article is
perfect, thank you.  This seems to mirror what Amol said about doing a
1/4 of the length.  This article said to do an L shaped bead 2-6 balls
along each corner side.
Here are some photos to post.  Would you oblige?
BGA is 40mm per side.  PCB is ~1 ft sq.  A little bigger than what is
found in the typical blackberry, I think... Ball pitch is 1.27mm.
We believe the cause is mechanical, not thermal.
Thanks everyone.

Genny

-----Original Message-----
From: Steve Gregory [mailto:[log in to unmask]]
Sent: June 12, 2009 6:35 AM
To: TechNet E-Mail Forum; Genny Gibbard
Subject: RE: [TN] Corner ball pad cratering

Morning Genny,

Since you said you were going to look at corner bonding, here is a
really good article (if you haven't seen it already) that Michael
Kochanowski from Intel and Brian Toleno from Henkel did about it:

http://www.trafalgar2.com/documents/Technical_Articles/6.09-kochanowski.
pdf

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Genny Gibbard
Sent: Thursday, June 11, 2009 3:10 PM
To: [log in to unmask]
Subject: [TN] Corner ball pad cratering

Hello all,
If you have identified a BGA with corner ball pad cratering, what would
be your suggestions to correct this condition?
Our thoughts:
1.  We plan to evaluate our handling processes to reduce/remove
excessive flex/strain occurring around this part 2.  We plan to evaluate
corner bonding or underfilling for the BGA.

Which do you feel would be the best direction to go?  Do you have other
suggestions?
Thanks in advance for all your help

Genny

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