Electro-Chemical Migration Definition Stage Project Wallace Ables - Dell HDP User Group Member Meeting Host: Oracle Santa Clara, CA. Feb Presented by: Keith Howell © 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 1. 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. 2. The failure mechanisms occur on products assembled for all segments of the electronics industry. 3. 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 Goal 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.

Not in immediate scope 5 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: 1.Conformal coating over no-clean fluxes. This may allow ECM under the conformal coating. 2.Solder mask test standards for ECM controls. 3.ImAg creep corrosion (covered by multiple current projects) © HDP User Group International, Inc

6 Project Objectives 1.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: a.Characterize failures escaping current test methods b.Test flux residue levels: SMT, Wave Solder, Rework c.Test flux application methods: controls, acceptable application levels, measurement methods and test methods d.Enhance test board and test coupon designs e.Identify acceptable flux residue levels by product class © HDP User Group International, Inc.

7 Project Objectives 2.Identify the influence of PCB manufacturing defects and design properties on the development of ECM and corrosion failures. Primary areas of investigation: a.Exposed Cu from solder mask openings (pin holes, undercut, damage, etc.) b.Moisture and chemical absorption properties c.Minimum cure level d.Voltage bias on a trace e.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 Goal and Objectives Compile list of current test methods / standards / test vehicles Compile list of failure modes from team members Correlate corrosion failures to gaps in current test methods Identify modifications required to current test methods Develop DOE’s to validate proposed changes Perform DOE’s. Collect and evaluate test data Draft proposed changes to test methods / standards / test vehicles Provided proposed changes and supporting data to test standard owners. Write final report

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. Established the basic project plan. Started to Identify the flux variables to be used in DOE. 9 Current Project Activities

10 Industry Standard Test Methods to consider

11 No clean flux failure modes Failure mode dependencies: Openings or defects in solder mask Voltage bias Activity level, type, and quantity of flux residue Humidity levels © HDP User Group International, Inc. 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 Corrosion Mechanism: A form of crevice or pitting corrosion at the small solder mask opening and the trace. Open Trace Corrosion Failure

12 No clean flux failure modes Failure mode dependencies: Voltage bias Activity level, type, and quantity of flux residue Humidity levels © HDP User Group International, Inc. 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 Corrosion Mechanism: Surface corrosion + 3V GND Non soldered OSP+ 3V Surface Corrosion Failure

13 No clean flux failure modes Failure mode dependencies: Openings or defects in solder mask (exposed anode / + voltage) Voltage bias Activity level and quantity of flux residue Humidity levels © HDP User Group International, Inc. 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) Corrosion Mechanism: Electrochemical Migration – metal dendrite growth + 3V anode GND ECM Corrosion Failure

14 1. Complete list of current test methods/standards/test vehicle. Complete 2. Compile list of failure modes from team members. Complete 3. Correlate corrosion failures to gaps in current test methods. 4. Identify modifications required to current test methods. 5. Develop DOE’s to validate proposed changes. 6. Perform DOE’s, collect and evaluate data. 7. Draft proposed changes to test methods/standards/test vehicle. 8. Provide proposed changes and support data to test standards owner. 9. Write final report Proposed Execution Plan Complete In-Process Not started

Team Members –To Date 15 © HDP User Group International, Inc. Agilent Alcatel-Lucent Arlon ASE Celestica Ciena Cisco Cobar Dell Emerson Ericsson Flextronics Fujitsu H3C Huawei IBM Intel Isola IST Group Kyzen Medtronic Nihon-Superior Oracle Panasonic Phillips Plexus Rockwell Suntak Shengyi TTM Tech Ventec Zestron ZTE