Hi Inge! Have your picture posted here: http://stevezeva.homestead.com/XILINX_Daniel_28.jpg I've not looked closely yet, I may look at them closer and tell you what I see. Steve P.S. Added a couple more names to the Technetter page today. Still more room... Steve -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge Sent: Tuesday, April 20, 2010 12:36 PM To: [log in to unmask] Subject: Re: [TN] SAC Shrinkage Voids in BGA Balls High all. Are u sure the balls are not shrinked even before soldering? I inspected hundreds of packages before soldering and found them to be like the neck of a Galapagos turtle. Both SAC and PbSn look all the same. I'll send a typical picture to Steve and ask you all: do you have shrinked balls too before action is taken? I get question frequently from the operators, because they want see shiny balls and not old prunes. Myself, I think the wrinkled balls has not significance. Inge -------------------------------------------------- From: "Werner Engelmaier" <[log in to unmask]> Sent: den 20 April 2010 08:55 To: <[log in to unmask]> Subject: Re: [TN] SAC Shrinkage Voids in BGA Balls > Hi Dave, > A shrinkage void in an ingot occurs where it solidifies last---in its > center. > The same is true for SJs, except that they do not necessarily cool from > the outside in. but a connected to various heatsinks and reservoirs---the > component is typically a heat sink [coolest] and the PCB is a reservoir > [hottest], with various heat transfer conditions on the surface due to > forced air/N2. > Overall, SJs tend to solidify first at their surface; hence, most > shrinkage voids are to be found there. > Werner > > > > > > > > > -----Original Message----- > From: David D. Hillman <[log in to unmask]> > To: [log in to unmask] > Sent: Tue, Apr 20, 2010 10:13 am > Subject: Re: [TN] SAC Shrinkage Voids in BGA Balls > > > Hi Bev - in theory, a shrinkage void in a solderball is the same physics > as a shrinkage void in a aluminum or steel casting so no, the shrinkage > void would not have to necessarily always reach a surface. However, after > looking at several hundred SAC BGA/CSP cross-sections, I have nearly > always (99.999%) found a path of a shrinkage void to the solderball > surface. Because we have a very limited and very small molten solder > "volume", I think you will find a surface connection. And I guess I'll > bite - why the question? > > Dave Hillman > Rockwell Collins > [log in to unmask] > > > > > Bev Christian <[log in to unmask]> > Sent by: TechNet <[log in to unmask]> > 04/20/2010 08:16 AM > 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 > [TN] SAC Shrinkage Voids in BGA Balls > > > > > > > TechNetters, > Do all SAC shrinkage voids in BGA balls reach/start at the surface of > the ball? I realize I may be stumped by a 2D cross-section of a 3D > phenomenon, but I thought I would ask this august body. > Bev > RIM > > --------------------------------------------------------------------- > This transmission (including any attachments) may contain confidential > information, privileged material (including material protected by the > solicitor-client or other applicable privileges), or constitute non-public > information. 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