BGA solder bridge

#63826

BGA solder bridge | 24 February, 2011

I have this BGA short issue, I took x-ray image, the solder ball having big void. We suspect the pad on BGA was oxidie. Reject percentage quite low, only 5 out of 6000.

But after the BGA re-ball, is work fine. Anyone have any idea to trobleshoot?

If someone like to see the x-ray image, please kindly post the email address. (or is that anyway to post the picture?)

Thanks.

KaHrpr

#63831

BGA solder bridge | 25 February, 2011

Was the void on the same pad for the 5 failures or were they random

#63834

BGA solder bridge - Adding Pictures | 28 February, 2011

Kim Here's an approach to posting pictures: * On your posting, clickon 'Edit' * Scrolldown past the 'Quote' 'Preview' 'Post' etc line * Clickon 'Attachments' * Enter your picture location * Select the choice that allows viewing the picture * Close out

#63839

BGA solder bridge | 28 February, 2011

It is random.

By the way, this board pass thought wave process, (BGA is at the top), will that cause the older short issue?

#63840

BGA solder bridge - Adding Pictures | 28 February, 2011

Davef I tried to click the "Attachment" button, but it trigger "Post" button, so I can't attach the picture here.

#63846

BGA solder bridge - Adding Pictures | 1 March, 2011

Kim, Just add a new posting to this thread then.

#63869

BGA solder bridge - Adding Pictures | 3 March, 2011

I tried, but error:- Attribute validation error for tag CFFILE. The value of the attribute destination, which is currently /var/www/smtnet/Forums/Attachments//, is invalid. The error occurred on line 12.

Try go to this url and view:- http://img845.imageshack.us/content_round.php?page=done&l=img845/8127/21192689.jpg&via=mupload

ScottE

#63870

BGA solder bridge - Adding Pictures | 3 March, 2011

I've seen this with through hole via in pad with soldermask plugging from the opposite side. Baking the boards solved it. Not using such a horrible via in pad method would also have solved it, but that wasn't an option. Is this ball sitting on a via?

#63876

BGA solder bridge - Adding Pictures | 3 March, 2011

Certainly the bridge is ugly, but the voiding is nothing that you should be bragging about either. Pretty ugly work.

BRIDGING: If all of your shorts appear in the vacinity of the heat sink, consider reducing the amount of paste that you apply there.

VOIDING: What kind of paste are you using? Search the fine SMTnet Archives, for instance http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=29346

SMTnet REJECTING YOUR PICTURE: Make a separate posting on the 'Site Support Forum.' This will help alert Roland and his peeps to the issue that you're having.

#63879

BGA solder bridge - Adding Pictures | 4 March, 2011

Hi ScottE

"Is this ball sitting on a via?"

I am not sure is I answered your question correct, the ball is sit on the pad.

#63881

BGA solder bridge - Adding Pictures | 4 March, 2011

Thanks davef

Bridging:- There is no heat sink on the BGA, the heat sink will be fix after relow. I do believe paste had something to do with it, but currently this defect didn't appear so oftenly, so we think that the main root cause is not from the paste.

Voiding:- We are using Alpha OM-338pt. As per the thread you suggest,

"burning off of the flux will reduce the amount of gassing occurring during reflow when the solder ball / paste is molten adn will infact reduce voiding int he devices"

If we did manage to vapor the flux and improve the void by extent the soak time, isn't it will cause more solder bridge issue?

#63925

BGA solder bridge - Adding Pictures | 9 March, 2011

We don't think your voiding is related to your bridging. We'd guess: * Voiding is either poor material selection or improper process recipe choice * Bridging is sloppy process management

#63972

BGA solder bridge - Adding Pictures | 21 March, 2011

Hi Dave

I agree with the 2nd point (sloppy process management) if the failure rate is higher than 5%.

But this is 0.083% case, and only happen once in the blue moon. As I study about the re-flow profile for the last whole week, current parameter setting is the optimum condition. By slightly increase/decrese some of the parameter, there will be some defective appear.

I am suspecting the problem was caused by the BGA itself or the original solder ball. However, I still need more failure sample to study.

#63986

BGA solder bridge - Adding Pictures | 21 March, 2011

Kim: You could be correct.

We had a batch of BGA that had a weird bridging pattern. Could not figure it out. So, we put the whole batch straight out of the 'box' bug-up on a hot plate and video recorded the balls as we took them through a thermal cycle. A few of the little shits bridged. Turns-out, ever so often BGA with BIG balls were next to each other.