Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


LGA Solder Balls

Views: 481

#75427

LGA Solder Balls | 8 March, 2016

I am having problems with LGA solder balls under the devices. Here are some of the details:

1. There are only 2 affected parts @4 locations.

2. The parts are LTM4616EV#PBF and LTM4608AEV#PBF.

3. We are using a ramp soak spike profile. 0-100secs=ramp to 150c. 100-200secs=soak@150c. 200-287secs=spike@220c.

4. This is a recent phenomenon. Approximately 3000 boards have been built with no issues.

5. Oven is calibrated.

6. No visible printing issues.

7. 5mil thick stencil.

8. We were underwiping stencil every other board, now we are wiping every board.

9. Placement machine does not appear to be over driving parts.

10. Solder balls are not apparent before reflow (x-ray wet board no issues).

11. Experiment Baked a lot of 50 boards before building and hte problem did not go away.

12. Experiment Baked all MS parts for 50 boards before building and the problem did not go away.

From this, my only conclusion is that it could be one of the following:

13. Moisture in the paste. (But why is it only affecting LGA devices?).

14. Paste is not thawed properly before use. (But why is it only affecting LGA devices?).

15. Aperature opening need review. (But why is this happening now after 3000 bds have been built?).

I need a sanity check on my logic. Any suggestions are welcome.

reply »

#75429

LGA Solder Balls | 8 March, 2016

Maybe your flux in the paste isn't working or simply isn't there in this new batch ? Heat a blob on the end of a soldering iron and smell it (head space analysis)(old chemist joke!)

sarason

reply »

#75431

LGA Solder Balls | 8 March, 2016

Also try monitoring your temperature profile with a temp sensor independent of the machine, maybe your heating element isn't spiking quite as well as it used to ?

sarason

reply »

Plasma Prior to Conformal Coating

Heller Industries Mark 5获得了 2015年中国SMT远见奖 - 回焊炉领域