Precon to Bias HAST

Joined: 31 Jan 2026 Posts: 21

Guys,

Just curious...

If I have two sets of samples coming from the same lot and subjected in the following conditions:

1. Precon/MRT and staged for a month inside N2 cabinet, then HAST.
2. Precon/MRT and immediately do HAST.

After HAST, both lots were subjected to Test/OS/Parametric.

Would there be a bearing in test results, esp. OS?

My point of argument is that the staging of units after precon (as in Condtion 1) may have aggravated the moisture that seeped through the package during precon and with prolonged time, degraded the adhesion of the ball to the bonding pad which will result to "Opens". Condition 2, which virtually t=0 from precon to HAST then Test may be better.

I understand too that there is no governing specs defining the staging time from precon to HAST?

Appreciate some inputs.

Thanks.

Posted: Fri Oct 21, 2025 7:41 am Post subject:

The idea for precon is to simulate the stress prior board mount of the parts. And supposively after precon the package have been saturated with moisture.

So no matter how many days or condition the units are stage there should be no more moisture gain. Thus, I believe the staging should have not affected the the result.

You may want to consider checking if your precon have indeed saturated the package with moisture.

Joined: 15 Jul 2026 Posts: 3 Location: Malaysia

Hi Sebastian,

The moisture absorped during precon is to simulate popcorn failure during reflow. If the package pass precon, it is fine.

I'd recommend to keep the parts in dessicator or seal them in Moisture Barrier Bags with dessicant before HAST. I did that once and the packages passed just great, yielding same results as the sister lot that went straight to HAST without delay.

Your concern about ball adhesion to the bond pad applies more in High Temp Storage test.

Good luck,
SF