Qualification of the Assembly Process of Flip-Chip BGA Packages ...

Texas Tech University, Nivetha Shivan, May 2012
Floor life is the time during which the semiconductor device can be exposed to moisture
at the end user‟s facility.
The MSL pre-conditioning technique is used to simulate the ambient conditions for a
device for a specified time period. The time period usually is the floor life for the device
added to 24 hours. The 24 hours is the time during which the device is exposed to
environment before sealing in an anti-static plastic bag at the assembly process site.
MSL3 is the most commonly used moisture sensitivity level for most packages. Hence it
was chosen for this project which has a moisture soak time of 192 hours with conditions
30°C/60%RH.
Following the moisture soak conditions, the device is exposed to solder reflow. This
technique simulates the process of mounting the device on the PCB at the end user‟s
facility. The peak reflow temperature and the reflow temperature profiles for the device
in this project was decided and implemented based on JEDEC standards (Refer
appendix).
A device is considered to be a failure if one or more of the following incidents happen:
1. Failures after electrical testing
2. Failures seen under acoustic microscope such as die cracks and internal
delaminations.
4.2.2 Temperature Cycling Technique [19]
The chamber used for this technique is called as Temperature Cycle Chamber Espec
TSE-11-A. Following MSL technique, the device is subjected to stress tests. The purpose
of these stress tests is to evaluate the resistance of the device to the different type of stress
conditions namely temperature cycling (extreme temperatures), thermal shock (sudden
changes to extreme temperatures) and pressure cooker test (severe temperature and
humidity conditions) etc. This project deals with the temperature cycle test after MSL.
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