SAC Aging 3

The aim of the SAC Aging 3 project is to use the Alloy Common Test Vehicle and to perform baseline microstructural characterization on ambient aged and elevated temperature isothermally aged samples.  In addition, it will perform failure mode analysis and characterization of ATC samples to determine extent of microstructural evolution and impact on final failure. At the same time the project will thermal cycle additional non-monitored samples for microstructural analysis at different thermal aging times and temperatures.  Data collected from the HDP User Group SAC Aging 2 project will be used for a comparison.  However, because of the Warped PWBs used in that project, some data cannot be used and/or can only be used with suspect.  Data from various projects using the same Alloy Common Test Vehicle will be compared for ultimate understanding.

Project stage: 
Project type: 
Lead company: 
Nokia

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Idea Information

Background: 
 
  • A follow-on to the HDPUG SAC Aging2 project applying lessons learned
  1. the thermal cycling test results were flawed due to warpage of the test boards. 
  2. thermal cycling test results were flawed due to warpage of the test boards. 
  3. Although flawed, these data indicated that the aging conditions used in the experiment were insufficient to induce decreased reliability. 
  4. Results from other Aging studies corroborate SAC Aging2, indicating that longer aging times are required to demonstrate aging effects. 
  5. In addition, no acceleration factor exits to allow correlation of aging at the relatively high temperature of 125 °C used in the experiment to aging at the lower temperatures such as 30 °C typical of storage conditions or 75°C typical of some operating conditions. It is debatable whether high temperature, 125°C aging effects are relevant to “real world” applications

 

                        Board randomly selected from fabricated boards.

                                                 

 

 

 

 

                         


 
  • Previously: ATC performance of SAC solder joints is known to be affected by thermal pre-conditioning often simply called aging.
  1. Lower reliability measured by characteristic lifetime and lower Weibull slope of ATC failures sometimes with earlier failures
  2. The effect is not the same or apparent in all cases and likely is dependent on component and strain
Problem: 

 

Aging initiates microstructural evolution in advance of the temperature cycling.  If aging “jumpstarts” the evolution process, crack initiation should occur in fewer thermal cycles than in un-aged samples. Thus, we expect aging to reduce the reliability or number of cycles to failure.

Definition Information

Goals / Benefits: 

 

This project will attempt to substantiate the evidence that the ATC performance of SAC solders is affected by thermal preconditioning or aging.  This project is based on a more focused test plan then that of SAC Aging 2 and will use the lessons learned from previous aging projects.  The project will use the same test board design and component(s) as SAC Aging 2 to facilitate the further understanding of this phenomenon, and attempt to relate ATC performance to microstructural changes that occur during any aging the product might see.  In additon because SAC Aging2 thermal cycling test results were flawed due to warpage of the test boards.  Our expectation is to insure that we generate data using good test boards to test the aging hypothesis. 

High level objectives: 

          Determine the best aging rate at which by thermal pre-conditioning, often called “aging”, effects the ATC performance of SAC solder joints.

          Determine the microstructural evolution and failure mode of cycled joints.

Approach: 

This project will be a designed experiment that uses an existing test board design and components to facilitate the launch of this new SAC Aging project.  It will perform baseline microstructural characterization on ambient (no age) and aged samples.  It will perform failure mode analysis and characterization on ATC samples to determine extent of microstructural evolution and impact on the final failure.  We will build additional samples for microstructural analysis at different aging times/temperatures.

 

 

A. Preliminary Schedule:

         Planned             Actual

Design TV                                            Complete           Complete

Laminate Material                                11/2015              11/2015

Receive Boards                                   11/2015              11/2015

Receive Components                          02/2016              01/2016

Time Zero Analysis                              03/2016              03/2016

Assembly Complete                             04/2016              04/2016

Wire Boards                                         05/2016              05/2016

Precondition Boards                            07/2016 

Begin Long Term aging                        07/2016 

ATC start  (short term aging)               07/2016 

Begin Microstructure Analysis              07/2016 

Complete Microstructure Evaluation    10/2016

ATC start  (long term aging)                01/2017 

ATC complete short term aging           02/2017

Interim Report                                     02/2017

ATC complete long term aging            07/2017

ATC Weibull Analysis                          Ongoing with ATC

Report                                                     2017

 

 B.  Project Flow Diagram:

 

C.  Design of Experiment Matrix:

 

SAC Aging Project

Basic Single Component Single ATC Profile Test Cell

 
 

SAC305

ATC - 0 days (RT aging)

32

ATC  - 20 days@125 °C

32

ATC - 40 days@125 °C

32

ATC xxxdays@75 °C

32

Baseline (no ATC) 0 days

16

Baseline (ATC) 20 days @125 °C

16

Baseline (ATC) 40 days @125 °C

16

Baseline (ATC) xxx days @75 °C

16

Total components

192


D.  Testing Methodology:

  • Use the existing test board design and components to facilitate the launch of a new SAC Aging Project.

The test board design already exists and the components can be procured easily.

The exact test board is completely compatible with the ALU ATC chamber and rack system. 

This testing can address some of the existing gaps in the current SAC Aging project

  • Perform baseline microstructural characterization on ambient (no age) and aged samples. Perform failure mode analysis and characterization on ATC samples to determine extent of microstructural evolution and impact on final failure.
  • Build additional samples for microstructural analysis at different aging times/temperatures – complete plan to be worked out (tentative based on resource availability).
Key Participants: 
Celestica
Cisco
Flex
Fujitsu
H3C Technologies
i3 Electronics
IBM
Juniper
Keysight Technologies
Kyzen
Nihon Superior
Nokia
NVIDIA
Oracle
Panasonic
Plexus
Sanmina
TTM Technologies
Ventec
UIC
Public