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BGA open

AF Ng

#9821

BGA open | 2 September, 1999

Could someone shares their experience on the causes of 'Open' in the BGA after reflow.

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ScottM

#9822

Re: BGA open | 2 September, 1999

| Could someone shares their experience on the causes of 'Open' in the BGA after reflow. | | Insufficient solderpaste. "No flux" (sat too long after print).

Those are what I've experienced.

Cheers, Scott

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#9823

Re: BGA open | 2 September, 1999

| Could someone shares their experience on the causes of 'Open' in the BGA after reflow. | | Are you talking about "primary" process or rework? Are you sure you have not clogged apertures on your stencil? What is the pitch of the balls?

My experience with 50mil pitch PBGAs is that it is basicly IMPOSSIBLE to create "opens" in the primary process. The process is so robust that you never do something that is so wrong to cause defects. You can place the part 50% off the pad and still get excellent joints after reflow. Only missing balls, completely missing paste, dirt on PCB pads, paste not reflowed, etc. can create a defect. With very basic and cheap process control I have processed about a million PBGAs, with virtually no (=0)defects caused by the process. The defects ALWAYS come from: 1) Electrically defective parts 2) Parts lost by the chipshooter (you place the BGA on top of a cap. or res.) 3) Product touched by operators before reflow So you should be able to resolve your problems if you do a few very, very, very, very basic process checks. Or verify that the part is electrically defective.

Good luck,

SB

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#9824

Re: BGA open | 2 September, 1999

| Could someone shares their experience on the causes of 'Open' in the BGA after reflow. | | Reflow prifle is also critical, as usual. On large boards board support is also a factor. If the board warps at the BGA you can experience opens. Good Luck

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#9825

Re: BGA open | 2 September, 1999

| | Could someone shares their experience on the causes of 'Open' in the BGA after reflow. | | | | | Insufficient solderpaste. "No flux" (sat too long after print). | | Those are what I've experienced. |

cbga or pbga if pbga check thermal profile, check solder bump before placement process,check pcb wrapage.also bake the pbga for 24 hrs @ 125c. if cbga check thermal profile, check solder paste, check missing solder bump berfore placement. any question please e-mail

| Cheers, | Scott |

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David

#9826

Re: BGA open | 3 September, 1999

| Could someone shares their experience on the causes of 'Open' in the BGA after reflow. | | You must have been in the same meeting I was in earlier today. We are currently having some opens on BGAs. The problem joints are all on the perimeter of the parts. We are investigating PWB plating, BGA ball presence, BGA solder ball quality, reflow profile, second reflow in wave solder, solder print coverage, warping in reflow - particularly looking for evidence to see if the PWB is rising (dome shape) in the center of the BGA. We are still investigating - will let you know what we determine. We are also open to any new ideas as to source of problem.

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Dean

#9827

Re: BGA open | 5 September, 1999

| Could someone shares their experience on the causes of 'Open' in the BGA after reflow. | | Single sided BGA assy? Or double sided BGA assy (BGA's on both sides)?

I have processed double sided (MIrror assy.) bga assemblies and can tell you it is possible to see opens on the bottom side (first pass BGA's). Essentially what happens is the bottom side reflows then gravity pulls the part away from the PCB, creating solder collums. In some cases the solder balls sepeates from the pad and BGA substrate, creating an open. I should mention these parts are bga 169, with integrated heat spredders. So, they have a considerably high weight per ball ratio. I have never seen this phenom. on PBGA's.

PS any one who claims a zero manufacturing defect in their process has a false sense of security. Statistically, you will have defects, eventually! This condition is a natural part of our universe and is predictable.

Respectfully, Dean

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Brad Kendall

#9828

Re: BGA open | 7 September, 1999

| Could someone shares their experience on the causes of 'Open' in the BGA after reflow. | | Are you having a problem with the joint openning up after reflow. Like it was soldered after the reflow process, but at final test is not? I had this problem. The culprit was the wave solder process. Even with tented vias, the center of the BGA (313 ball) was getting hot enough in wave due to heat getting trapped that it would cause the joint to crack or pull back and have an open.

Brad Kendall Hella Electronics

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