PoP: An EMS perspective on assembly, rework and reliability
PoP: An EMS perspective
on assembly, rework and
reliability
by Heather McCormick, Irene Sterian, Jimmy Chow, Mike Berry, Joel Trudell and Roden Cortero,
Celestica Inc., Toronto, ON, Canada
While already in widespread
use in the consumer market for
handheld, portable electronics,
package on package (PoP) con-
tinues to gain in popularity and
seems likely to be implemented
in other types of electronic
assemblies. In order to define
internal assembly processes for
PoP devices, an assembly and
Figure 1. Pre-stacking step 1—dipping.
reliability study was undertaken.
The first goal was to assess the
performance of different dip-
pable fluxes and solder pastes
in terms of assembly yield and
quality. The second was to
assess the reliability of different
variations of the test vehicle un-
der accelerated thermal cycling.
As with other small area
Figure 2. Pre-stacking step 2—component reflow.
array packages, both the top
and bottom devices in the PoP
stack are offered with a range
of different alloys. This study
includes three alloy variations—a
SAC305 stack, a SAC405
stack, a stack with a SAC105
upper package, and a SAC125
lower package. In addition to
the variation in ball alloy, dif-
ferent dippable materials were
included in the study.
Figure 3. Pre-stacking step 3—placement.
Keywords: Package on Package,
Dip Flux, Dip Paste, Reliability
This paper was originally presented at the
PanPacific Microelectronics Symposium,
Figure 4. Pre-stacking step 4—assembly reflow.
Hawaii, USA, February 2009.
16 – Global SMT & Packaging – March 2009 www.globalsmt.net
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