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September 2002

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Date:
Thu, 12 Sep 2002 08:22:51 +0800
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Hi, again, Al,

Ain't got the time to sign into the picture site right now, but as Earl
says, the irregular shape of the balls are unlikely to cause voiding. They
are the result of poor/rushed component manufacture (I've seen some truly
aweful-shaped balls on otherwise pricey components). What I reckon the
irregularities do affect, in the OEM's rush to achieve economic glory on
the bodies of their customers, is the solder volume in the balls. This
affects the uniformity of volume in the finished joints (assuming your
solder paste deposition is of consistent thickness), which in turn affects
joint reliability through uneven stress/strain distribution.

Peter



[log in to unmask]    10/09/2002 08:46 PM

              To:  DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group@ST Domain, [log in to unmask]
              cc:
              Subject: Re: [TN] 1mm bga voiding









Peter and Technetters,

The cross section is of a part as it comes in the door.  That part has not
been attached to a board.  The question is would the dents on the ball
cause voiding when it is reflowed.

I have also placed three additional x-section pictures of a "Reflowed"
balls.  However, I think the link requires one to sign in to ofoto.com (for
free though).

http://us.f201.mail.yahoo.com/ym/ShowLetter?YY=40492&order=down&sort=date&pos=0&view=a&head=brief


I will email the pictures directly to anyone interested (they're in jpeg
format).

Thanks for all the replies

Al





[log in to unmask] on 09/09/2002 09:53:03 PM

To:   "TechNet E-Mail Forum." <[log in to unmask]>, [log in to unmask]
cc:   [log in to unmask]

Subject:  Re: [TN] 1mm bga voiding



Al,

You have one very irregularly shaped ball there ('skews the expression).
Can't see much of the voiding you talked about, though. I take it the bit
at the top of the picture is the component pad (?). If you are actually
getting a lot of voiding as well, I suspect that your thermal profile is a
bit hot for these components, and you may have to look at shielding them a
bit. Are these BGA's significantly smaller / less 'massive' than the other
that you say are OK? Have you tried thermocoupling these devices
specifically and taking their temperatures during the reflow cycle? What
are the results? If temp is OK, how about duration?

Peter



[log in to unmask]    10/09/2002 01:27 AM
Sent by: TechNet <[log in to unmask]>

Please respond to "TechNet E-Mail Forum."; Please respond to alan.kreplick

              To:  [log in to unmask]
              cc:  (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
              Subject: Re: [TN] 1mm bga voiding








Victor and other Technetters,

Hopefully this link shows the 1mm BGA picture (x-section)

http://www.ofoto.com/PhotoView.jsp?UV=922011120789_31499403105&US=0&collid=29888403105&photoid=19888403105





Al




Victor Hernandez <[log in to unmask]>@IPC.ORG> on 09/09/2002
12:23:59 PM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
      to [log in to unmask]

Sent by:  TechNet <[log in to unmask]>


To:   [log in to unmask]
cc:

Subject:  Re: [TN] 1mm bga voiding


Al,

   The IPC-A-610C sec. 12.2.12 Area Array/Ball Grid Array states that "
Acceptable - Class 1,2,3 Less than 10% voiding in the ball to board
interface.   Process Indicator - Class 2,3  10-25% voiding in the ball to
board interface.   What is the SIZE of the ball you are using.

   Did we have to SIGN UP to the Web Page to view your photo.   Perhaps a
fellow TechNetter can offer their site for viewing.

victor,

-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Monday, September 09, 2002 9:13 AM
To: [log in to unmask]
Subject: [TN] 1mm bga voiding


Technetters-

We are getting 1mm BGA devices with these mechanical defects (see attached*
for link to picture) from testing processes at the vendor.

These devices have excessive voiding when reflowed on to a board with other
BGAs that do not have a voiding problem.  The vendor insists it is our
process that causes the voiding.

Question-  would you expect this mechanical damage to lead to voiding in
the reflowed joint?


*
http://www.ofoto.com/ShareLandingSignin.jsp?UV=922011120789_31499403105&US=0




&Upost_signin=OrderPhotos.jsp%3FshowSlide%3Dtrue&Un=774560513&Um=54718403105




.84079403105



Al

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