Electro-Chemical Migration Definition Stage Project

1. Electro-Chemical Migration Definition Stage Project Wallace Ables - Dell HDP User Group Member Meeting Host: Shengyi Technology Co., Ltd. And NERCECBM Guangdong, China Dec. 5, 2012 Presented by: Larry Marcanti © HDP User Group International, Inc.

2. Problem Statement The current industry standard test protocols were originally developed to identify highly ionic contaminant levels (halides) after a cleaning process. These test protocols are not completely effective at identifying ECM and corrosion exposures from no-clean flux residues. © HDP User Group International, Inc.

3. Background • Products assembled with no clean flux systems are experiencing various forms of corrosion and Electro Chemical Migration failures. These products and flux systems have passed the current industry standard cleanliness and corrosion resistance testing, demonstrating that these test procedures are not completely effective. • The failure mechanisms occur on products assembled for all segments of the electronics industry. • The current industry standard testing does not take into consideration various acceleration factors associated with no clean flux and product design features. © HDP User Group International, Inc

4. Project Objectives • Identify the required enhancements to current industry specifications, test methods, test boards and coupon design to increase detection of ECM and corrosion induced failures when no clean flux systems are used. • Areas to investigate: • Cleanliness testing • Corrosion resistance testing • ECM testing • Maximum acceptable residue levels • Influence of PCB manufacturing defects • Influence of PCBA design features © HDP User Group International, Inc.

5. Not in immediate scope • Some closely aligned aspects of this project will be deferred to a follow-on project, or are already being investigated by other project teams. Therefore the following factors will not be in the scope of this project: • Conformal coating over no-clean fluxes. This may allow ECM under the conformal coating. • Solder mask test standards for ECM controls. • ImAg creep corrosion (covered by multiple current projects) • © HDP User Group International, Inc

6. Project Goals • Identify modification to current industry standard specifications and test methods for cleanliness testing, corrosion resistance testing, and ECM testing to increase detection of failures when no clean flux systems are used. • Primary areas of investigation: • Characterize failures escaping current test methods • Test flux residue levels: SMT, Wave Solder, Rework • Test flux application methods: controls, acceptable application levels, measurement methods and test methods • Enhance test board and test coupon designs • Identify acceptable flux residue levels by product class © HDP User Group International, Inc.

7. Project Goals • Identify the influence of PCB manufacturing defects and design properties on the development of ECM and corrosion failures. • Primary areas of investigation: • Exposed Cu from solder mask openings (pin holes, undercut, damage, etc.) • Moisture and chemical absorption properties • Minimum cure level • Voltage bias on a trace • Minimum spacing between positive and negative features to prevent ECM © HDP User Group International, Inc.

8. Proposed Execution Plan How the project will answer the Objective and Goals

9. Completed list of current test methods • Completed identification of failure modes observed with no clean residues • Started gathering existing possible Test Vehicles. • Have met with IPC sub-committees on Coatings, Cleaning and Testing to discuss our activity. • Started project plan and DOE development Current Project Activities

10. Industry Standard Test Methods to consider

11. No clean flux failure modes Open Trace Corrosion Failure • Corrosion Mechanism: • A form of crevice or pitting corrosion at the small solder mask opening and the trace. • Failure mode dependencies: • Openings or defects in solder mask • Voltage bias • Activity level, type, and quantity of flux residue • Humidity levels • Potential areas to investigate with current test methods: • Modify test coupon to detect crevice or pitting corrosion failure modes? • Solder mask openings on test coupon (pitting corrosion) • Flux trapped under low stand off connections (crevice corrosion) • Measure flux residue levels (identify threshold of acceptable residual flux contaminants) • Multiple voltages to traces or nets on the test coupon (identify voltage level sensitivity) • Multiple humidity levels © HDP User Group International, Inc.

12. No clean flux failure modes + 3V GND + 3V Non soldered OSP • Corrosion Mechanism: • Surface corrosion Surface Corrosion Failure • Failure mode dependencies: • Voltage bias • Activity level, type, and quantity of flux residue • Humidity levels • Potential areas to investigate with current test methods: • Measure flux residue levels (identify threshold of acceptable residual flux contaminants) • Multiple voltages to traces or nets on the test coupon (identify voltage level sensitivity) • Multiple test pad and hole sizes • Multiple surface finishes • Multiple humidity levels © HDP User Group International, Inc.

13. No clean flux failure modes + 3V anode GND • Corrosion Mechanism: • Electrochemical Migration – metal dendrite growth ECM Corrosion Failure • Failure mode dependencies: • Openings or defects in solder mask (exposed anode / + voltage) • Voltage bias • Activity level and quantity of flux residue • Humidity levels • Potential areas to investigate with current test methods: • Modify test coupon to provide exposed anode adjacent to ground features (already exists?) • Measure flux residue levels (identify threshold of acceptable residual flux contaminants) • Multiple voltages to traces or nets on the test coupon (identify voltage level sensitivity) © HDP User Group International, Inc.

14. Proposed Execution Plan • Compile list of current test methods / standards / test vehicles (Rich K) - Complete • Corrosion • Standards • Test vehicles • Table of Details • ECM • Standards • Test vehicles • Table of Details • Other Related • Standards • Test vehicles • Table of Details   • Compile list of failure modes from team members - Complete • Images , white papers, Collect, & summarize -owner?? • Correlate corrosion failures to gaps in current test methods • Characterize corrosion details for each failure sample. • Design, flux type, environmental conditions, etc. • Evaluate current test methods for potential gaps that did not detect failure mode. • Identify modifications required to current test methods • Identify any planned enhancements to the current test standard by their owners.

15. Proposed Execution Plan • Develop DOE’s to validate proposed changes • Thoughts for DOE Designs (Exploratory level – to compare current test methods) • Flux Type Factors: • No VOC, • VOC, • High Acid #, • low acid #. • Identify pool from teams of what they use. • OA vs Rosin • Forms of flux (wave, solder paste, rework) • Solder Mask • Type • Coverage • Finish • OSP, ENIG, ImAg, ImSn, with sub catagories • PCB fabricator • Voltage Bias: Different voltage levels (0, 3.3, others) • Alloy: SAC 305 only • Perform DOE’s. Collect and evaluate test data • Will require at least 2 DOE’s. • Level 1 -Screening of compare current industry test methods • Level 2- Screening versus unique (Bono, HP, Cookson RF) • Draft proposed changes to test methods / standards / test vehicles • Provided proposed changes and supporting data to test standard owners. • Write final report

16. Team Members –To Date • Agilent • Alcatel-Lucent • Arlon • ASE • Celestica • Cisco • Cobar • Ciena • Dell • Ericsson • Flextronics • Fujitsu • IBM • Intel • Isola • IST Group • Kyzen • Multek • Nihon-Superior • Oracle • Phillips • Plexus • Rockwell • Shengyi • Syst • TTM Tech • Zestron © HDP User Group International, Inc.