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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Dye and Pry

Views: 5589

#53979

Dye and Pry | 12 March, 2008

Hi All,

One PCBA failed test after went through the Shock Test(Vibration) and suspected to be BGA solder ball crack. We performed dye and pry and found PCB's pad lifted with red mark ink penetrate pad underneath, what does this mean?

Can I say the PCB pad is not strong enough to withstand the vibration? Or, is it process related issue?

Note: This BGA is installed with heatsink(with hook at both side of the heat sink) manually by operator prior to the shock test.

Thanks, Sean

reply »

#53983

Dye and Pry | 12 March, 2008

Why would a board failure related problem be a process problem. I agree most companies believe EVERY problem is a Proces Problem, but in the real world we know this is not true.

A pad lifting means your solder joint was able to rip it off the board. Are you asking if your process was able to loosen the pad? I doubt it very much. I know some good profile people and consider myself one too, but to be able to focus energy on that one pad without affecting the others?

Now is this just a lone pad with no trace to it? I believe you will find this your case. Lone BGA pads come off easily. It'not process related.

reply »

#54005

Dye and Pry | 12 March, 2008

You can say: The pad was lifted after reflow and prior to the dye and pry failure analysis.

When we see lifted pads, we think: * That's a good solder connection * Either it took a lot of force to lift that pad or the fabrication of the board in the area of the pad was defective

Questions are: * Why did you tell us the following? "This BGA is installed with heatsink (with hook at both side of the heat sink) manually by operator prior to the shock test." * How did installing the hooks on either side of the BGA contribute to the lifting of the pad? * What is the vibration profile? * What is the end-product use environment?

reply »

#54006

Dye and Pry | 13 March, 2008

Thanks Real Chunks and Davef...Yours input is valuable to me. My inputs towards your question asked below:

Questions are: * Why did you tell us the following? "This BGA is installed with heatsink (with hook at both side of the heat sink) manually by operator prior to the shock test." Reply: I want to let you guys know as detail as possible so that following discussion will be more fruitful.

* How did installing the hooks on either side of the BGA contribute to the lifting of the pad? Reply: I believe manually installing the heatsink onto BGA should not cause pad lifted. Anyway, I am not 100% sure on this..That's the reason I am seeking input from all. * What is the vibration profile? Reply:I don't have the said profile. Anyway, what I know is that this shock test used mainly for testing solderbility strenght, especially those BGAs.

* What is the end-product use environment? Reply: Room temperature.

reply »

#54032

Dye and Pry | 14 March, 2008

ol' hege has got to agree with Chunks and Dave. Seems every time there is a problem, the finger is first pointed at the process. For my $.02 it doesn't matter if your process is 100% bulletproof, procurement will screw it up by finding a vendor that will save a nickel on the pcb, component, connector(take your pick). Putting garbage into a good process will simply guarantee that you produce good garbage.

You must believe what you see. This is science, but it is not rocket science. What you have is a strong solder joint, stronger than the pad adhesive. It is what it is. Maybe the vibration testing is too strenuous for a lone non-connect pad, and maybe this is just a single anomaly.

If you have done your homework, then you must believe in your process. Pay no attention to those who would suggest that the process is the cause of problems that are more likely related to lesser quality materials.

This is a sore spot at my place of employment. It is a battle all the time. Save a nickel on the PCB, spend a dollar to fix it.

Sorry if my brown aura of anger is showing....

reply »

#54049

Dye and Pry | 15 March, 2008

All,

What if BGA solder crack do exist after the shock test? Its happen at the corner of the BGA. Base on your experience, what are the potential root causes?

Thanks, Sean

reply »

#54058

Dye and Pry | 17 March, 2008

Hi All,

Besides the above question, I have another one as below:

(1) How frequent that we need to perform strain gauge study on ICT, Functional test fixture? Is it a necessary to perform this study each time after ICT, Funtional test fixture preventive maintenance?

Thanks, Sean

reply »

Software for SMT

 Reflow System