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

Texas Tech University, Nivetha Shivan, May 2012
CHAPTER 3
DESIGN OF EXPERIMENTS AND THE PASS/FAIL CRITERIA
3.1 Pre-engineering Qualification
The goal of this project is to do pre-engineering qualification of the new assembly
process. Pre-engineering qualification is divided into two phases – Phase I and Phase II.
Phase I of the qualification uses dummy or non-functional devices whilst Phase II uses
functional devices.
Pre-engineering Qualification is qualifying the BGA package with high pin counts
(meant for the upcoming QDR device), and the die that is used for this stage of
qualification is an existing QDR whose functional characteristics are already known to
us.
Engineering Qualification is the next stage which involves qualification of the same BGA
package with high pin counts and the die that is used in this stage is the upcoming QDR
with speed much higher than the existing QDR.
By this way, we are introducing one variable at each stage of qualification. From the
results of each stage of qualification, we can decide what caused the failure (if any) based
on the variable introduced at that stage.
3.1.1 Phase I
The dummy units do not have any CMOS circuits, but includes only di-electric layers and
a metal layer. The purpose of this dummy wafer is primarily to qualify materials in the
package, as the functional wafers will add an extra variable namely „electrical
characteristics‟. Avoiding the variable in the first step of qualification will help identify
the correct root cause of failures (mechanical or electrical, if any). Figure 3.1 shows the
image of the non-functional device used in Phase I Qualification.
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