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Micro BGA coplanarity

#23441

Micro BGA coplanarity | 20 February, 2003

I placed a micro bga using flux paste and ran it through my oven and it came out as if someone had pushed down on one side. I can find no reason for this, has anyone ever seen this and how did you fix it?

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#23445

Micro BGA coplanarity | 20 February, 2003

Give us infortmation, please. What is [are]: * Height board to board side of the interposer on the low side of uBGA * Height board to board side of the interposer on the high side of uBGA * Alloy of solder balls, no paste was used correct? * Type of flux used * Temperature on the solder balls during reflow [and how and where those temperatures were measured]

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#23866

Micro BGA coplanarity | 21 March, 2003

Hi, there is one very important thing.How many boards came out with exatly the same problem?

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RDR

#23869

Micro BGA coplanarity | 21 March, 2003

Is it possible that the flux you used, if applied in excess could have caused the balls to "blow out". I have seen this in the past and it was related to the type of flux we were using and the amount.

Russ

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iman

#23886

Micro BGA coplanarity | 21 March, 2003

Russ,

u mean excess flux causes "blow hole" defect?

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#23887

Micro BGA coplanarity | 22 March, 2003

I agree with Russ, seen this happen if the right amount of paste flux is not applied. You mite want to dip the spheres of the BGA to the layer of paste flux.

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RDR

#23898

Micro BGA coplanarity | 24 March, 2003

I don't know if I would call it a "blow hole". what I believe happens (I don't have a camera to watch spheres during the reflow process) is that when the flux starts heating up, expansion, bubbling, or something physically displaces the balls. We found that a certain type of flux when applied excessively caused this phenom. Other types/manufacturers have appeared to be more tolerant of volume but we have stopped putting so much on regardless of type.

Russ

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