Posted by Rellab Guy: Thu Sep 18, 2003 11:43 pm    Post subject: PCT Corrosion Failures

We loaded a lot in PCT. When we took out the lot, 60% failure rate. FA said the failures are due to corrosion. They said we should check our chamber. I wonder how he was able to tell it's our chamber that caused it. I think the lot is bad. What's the best way to settle the issue?

Rellab Guy

Posted by EE: Fri Sep 19, 2003 12:11 pm    Post subject:

Hi Rellab Guy,

It’s not easy being confronted by something like this, is it? First off, you need to ensure that your PCT system was not the one that caused this. Maybe this is the point being raised by FA. If you look at Jedec JESD22-A102, it says that the ionic contam of the test apparatus and chamber must be controlled to avoid artifacts. It also specifies a minimum resistivity for the water to be used.

You must show FA that you do not have any problems with the DI water you’re using for PCT before you go further with root cause analysis. Other signs that indicate you may indeed have a water problem: 1) other lots loaded with the lot also show metal corrosion or discoloration; 2) other PCT chambers are affected; 3) even the good units show metal discoloration; 4) the affected units do not show passivation defects; and 5) your D/I water has a Cl content of 0.2 ppm or higher.

Keep us posted!

EE

Posted by Jarod: Thu May 17, 2007 10:24 am    Post subject: PCT Failures

Hi,

Is there a possibility that corrosion seen after PCT was induced by having a misaligned streetwidth?

Thanks.

Posted by Jaec: Thu May 24, 2007 6:25 pm    Post subject: Re: PCT Corrosion Failures

Normally you do not get 60% failure rate on corrosion if it is device related. Usually you do get a lot of failures, if your samples/basket/chamber is/are not clean.

If the lot is bad, it should manifest high failure rate on other Rel tests too.

How to settle the issue? THB is another test which should settle the issue and which is more realistic test to react when there is a failre.

I hope this helps.
_________________
Jessica M. Castillo
Failure Analysis Consultant
Sigmatech Inc. Phils.

Posted by Skywalker: Fri Jul 06, 2007 5:25 pm    Post subject:

Did your lot fail at continuity test? If so, try cleaning the leads of your units.

You should check your apparatus as well.

I think it is normal that your leads would be corroded since PCT involves humidity & temperature.

Just check if your lot failed at continuity test before anything else. You might be just encountering contact issue.

Posted by mel_c: Fri Jul 13, 2007 10:28 pm    Post subject:

Hi Rellab guy,

pls clarify the following items:
1. what was the output response of PCT which yielded 60% failure rate? CSAM? Electrical Test? O/S Test? External Visual Inspection?
2. what was the part of the package that was corroded?

PCT is a rel test which is a combination of pressure, temperature and humidity. It is the Rel Test designed to test the package integrity against ionic contamination and corrosion. If the corrosion you observed was on the top of die, there is a serious problem with the package integrity of your device loaded at PCT. If it is the leads that were corroded, you have to do the following:
1. subject the DI water inside the PCT chamber for ionic contamination test
2. conduct EDX analysis on fresh units of the affected batch (to check the cleanliness of the leads prior loading)
_________________
mel_c