Electro-Chemical Migration

Idea Stage Project Wallace Ables - Dell

HDP User Group Member MeetingHost: Multek

Boeblingen, Germany

May 22, 2012

Phone-in Presentation

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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 exposures from no-clean flux residues.

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Background

1. Various forms of corrosion and Electro Chemical Migration failures on products that pass the current cleanliness and corrosion resistance test protocols have demonstrated that these test procedures are not effective.

2. The failure mechanism is the same regardless what segment of the electronics industry the PCBA is used.

3. The current testing does not take into consideration various acceleration factors associated with no clean flux and product design features.

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No clean ECM corrosion failures

Surface corrosion

Solder mask Porosity

Open trace / solder mask opening

Open trace / solder mask

opening

Surface corrosion

Dendrite / short / open

Dendrite / short

Dendrite / short

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Project Objectives

Identify required enhancements to the current industry specifications, test methods, and coupon design to mitigate the electro-chemical migration and corrosion induced failures when no clean flux systems are used.

Cleanliness testing Corrosion resistance testing ECM testing Maximum acceptable residue levels by class of

product Minimum acceptable solder mask properties Product design recommendations

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Not in immediate scope

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Some closely aligned aspects of this project will be put off until a follow-on project is underway. Therefore the following issues 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.

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Project Goals

1. Develop a set of specifications and test methods (or enhancements to the current industry specifications) for cleanliness testing, corrosion resistance testing, and ECM testing to identify exposures when no clean flux systems are used.a. SMT flux residuesb. Wave solder flux residuesc. Rework flux residues – qualification for flux

application methods, controls, acceptable residue levels, and test methods

d. Develop acceptable flux residue thresholds based on test results

e. Develop different acceptance levels based on product class levels

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Project Goals

2. Identify enhancements to the test methods, test procedures, and test coupon design that take into account significant solder mask properties and product design features that influence the development of ECM and corrosion failures.a. Exposed Cu from solder mask openings (pin

holes, undercut, damage, etc.)b. Moisture and chemical absorption propertiesc. Minimum cure leveld. Voltage bias on a tracee. Minimum spacing between positive and

negative features to prevent ECM

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Team Members –To Date

• Agilent • Alcatel-Lucent • Arlon • ASE• Cisco• Dell• Ericsson• Flextronics• IBM

• Intel• Isola• Nihon-Superior• Oracle• Phillips• Plexus Plexus • Rockwell • TTM Tech

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