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Reliability for High Temperature Power Computing
Reliability for High Temperature Power Computing
This experiment considers the reliability of different electronic components and evaluates them on 0.200" power computing printed circuit boards with OSP.
Analysis Lab

Authored By:
Thomas Sanders, Sivasubramanian Thirugnanasambandam and John Evans, Ph.D.
Auburn University, Department of Industrial & Systems Engineering
Auburn, AL, USA

Michael Bozack, Ph.D.
Auburn University, Department of Physics
Auburn, AL, USA

Wayne Johnson, Ph.D.
Tennessee Tech University, Department of Electrical & Electronics Engineering
Cookeville, TN, USA

Jeff Suhling, Ph.D.
Auburn University, Department of Mechanical Engineering
Auburn, AL, USA
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Summary
This experiment considers the reliability of a variety of different electronic components and evaluates them on 0.200" power computing printed circuit boards with OSP. Single-sided assemblies were built separately for the Top-side and Bottom-side of the boards. This data is for boards on the FR4-06 substrate.

Isothermal storage at high temperature was used to accelerate the aging of the assemblies. Aging Temperatures are 25oC, 50oC, and 75oC. Select data from aging times of 0-Months (No Aging, baseline), 6-Months, and 12-Months will be presented.

The assemblies were subjected thermal cycles of -40 degrees C to +125 degrees C on a 120 minute thermal profile. The test wassubject to JEDEC JESD22-A104-B standard high and lowtemperature test in a single-zone environmental chamber toassess the solder joint performance.

The principal test components are 5 mm, 6mm, 13mm, 15mm, 17mm, 31mm, 35mm and 45 mm ball grid array (BGA) packages with solder ball pitch varying from 0.4 mm to 1.27 mm. Most of the BGA packages are plastic over-molded, while the 31mm and 45mm packages are Super-BGAs (SBGAs). Several surface mount resistors (SMRs) are also considered in order to understand the effect of solder paste composition on paste-only packages.

The primary solder for package attachment in this experiment is standard SAC305. Two solders designed for high-temperature reliability are also considered.
Conclusions
The failure data from this test was found to follow specific trends depending on the type and size of the component. The smaller plastic ball grid array (BGA) packages (5mm - 17mm) show failure data trends that are exemplified by the CABGA 208 (15mm) package. Regarding the effect of various solder paste [P] and sphere [S] combinations, the Characteristic Life values show the following pattern, listed from best to worst:

(1) Matched Innolot ([P] + [S])*,
(2) (2) [S]SAC305 doped with [P]Innolot,
(3) (3) Matched SAC305 ([P]+[S]), and
(4) (4) Matched SnPb ([P]+[S])

(* Note that Matched Innolot data is available only for the CABGA 208 and CABGA 36 components.)

A very clear trend also exists regarding the substrate effect: smaller plastic BGA components assembled on the FR4-06 substrate are universally more reliable than identical components assembled on the Megtron6 substrate, when controlling for all other factors.

A larger plastic BGA component, the PBGA 1156, shows similar failure trends in terms of most particulars. However, one key difference exists. The PBGA does not show a significant improvement in joint reliability during Innolot paste doping.

Two Super-BGA components, the SBGA 304 and SBGA 600, also show differences in failure data trends to the smaller plastic ball grid arrays. These are cavity-down, metal-capped components, and so are structurally quite different from the previously discussed packages. Like the PBGA 1156, these packages do not show an improvement in reliability via Innolot paste doping (in fact, reliability is lower in the doped case). Moreover, both of the Super-BGA components show a reversal of the substrate-effect seen in the plastic packages and display higher reliabiltiy on the Megtron6 substrate than on the FR4-06 substrate.
Initially Published in the SMTA Proceedings
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