 Welcome  Review Minutes and Action Items from last meeting  Project History  Determine next steps for committee  Review New Action Items Agenda

Welcome  Welcome  Introductions  Please introduce yourselves  Name  Company and position  What is your expectation of this group/meeting?  Assign a scribe to take minutes

Antitrust Statement There should never be a discussion of the following at IPC meetings:  Price or any elements of price or pricing policies, including costs, discounts, etc.  Sales or production quotas, territories, allocations, boycotts or market shares.  Identified individual company statistics, inventories or merchandising methods.  Particular competitors or customers.  Commercial liabilities, warranties, guarantees or the particular terms and conditions of sales, including credit, shipping and transportation arrangements.  Anything dealing with "arm-twisting," trade abuses or excluding or controlling competition.

Principles of Standardization In May 1995 the IPC’s Technical Activities Executive Committee (TAEC) adopted Principles of Standardization as a guiding principle of IPC’s standardization efforts. Standards Should :  Show relationship to Design for Manufacturability(DFM) and Design for the Environment (DFE)  Minimize time to market  Contain simple (simplified) language  Just include spec information  Focus on end product performance  Include a feedback system on use and problems for future improvement Standards Should Not:  Inhibit innovation  Increase time-to-market  Keep people out  Increase cycle time  Tell you how to make something  Contain anything that cannot be defended with data

Project History

Background Corrosion Failures in the Field Growing number of corrosion failures observed in the field More products are being used in ISA G2-GX environments Available tests were not sufficiently predictive for PCBs and PCAs Need more predictive corrosion- resistance test for PCBs and PCAs Creep Corrosion

Mixed Flowing Gas (MFG) EIA B for Connectors Test to determine the reaction of plated or unplated connector surfaces when exposed to corrosive atmospheres Mixed Flowing Gas Test Chamber

MFG and Finished PCAs Connectors vs PCAs Standard MFG testing is predictive and useful for connectors But extended testing of finished PCAs in Class IIIA conditions did not produce failures found in the field, especially creep corrosion Test Conditions from EIA B

Extending MFG Alcatel-Lucent published results in 2007/2009  Using a modified MFG tests on PCBs and PCAs they were able to form creep corrosion on samples 3-11g task group began investigating the Alcatel-Lucent modified MFG test as a possible creep corrosion test H2SH2SSO 2 NO 2 Cl 2 ALU International 1700 ppb*200 ppb 20 ppb *Normally 100 or 200ppb for test

Goal Identify or create a test method to differentiate and predict corrosion resistance of components and PCAs in the field  Develop a next generation corrosion test using a modified mixed flowing gas test method for predicting field life of electronic assemblies and materials in G1-GX environments as defined by ISA  Investigate other corrosion tests, including Flowers of Sulfur, as alternatives to mixed flowing gas tests

Modified MFG Tests Three different MFG chambers  Alcatel-Lucent  CALCE  Battelle Identical test conditions, coupons and materials Tightly specified MFG operating procedures Experienced PIs

Reproducing Alcatel-Lucent Results Conditions from APEX2007 paper: Unbiased (no applied voltage) Keep same parameters from first test 40C, 70-75% RH H2SH2SSO 2 NO 2 Cl 2 ALU International 1700 ppb*200 ppb 20 ppb *Normally 100 or 200ppb for test

Test Coupons Controls: – Bare copper – SnPb HASL Test samples: – OSP – Immersion silver – ENIG Alcatel-Lucent test coupons (same as 2009, includes PTH)

Preconditioning Precondition with solder assembly processes SMT print and reflow Wave solder RO and OR fluxes Masked areas to create interfaces

Sample Analysis (after testing) 1.Visual inspection 2.Mass change measurement of witness coupon 3.Determination of chemical composition of corrosion products 4.Removal of corrosion products followed by additional surface inspection 5.Measurement of corrosion rate in angstroms

Different Types of Corrosion Observed Fiber assisted corrosion [Immersion Silver–day 5 Discoloration [Bare Copper –day 5] Discoloration Creep [Immersion Silver–day 5] Creep White Patina [Bare Copper –day 10] White Patina Flaking [Immersion Silver–day 20] Flaking Green Patina [Bare Copper –day 5] Green Patina

Results Board TypeDay 5Day 10Day 15Day 20 Cu Cu-OR Cu-RO SnPb SnPb-OR SnPb-RO OSP OSP-OR OSP-RO ImAg ImAg-OR ImAg-RO ENIG ENIG-OR ENIG-RO DiscolorationCreepWhite Flaking Green 3 out of 3 1 out of 3 2 out of 3 Creep Corrosion Results - CALCE

Board TypeDay 5Day 10Day 15Day 20 Cu Cu-OR Cu-RO SnPb SnPb-OR SnPb-RO OSP OSP-OR OSP-RO ImAg ImAg-OR ImAg-RO ENIG ENIG-OR ENIG-RO Results DiscolorationCreepWhiteFlakingGreen Creep Corrosion Results - Battelle 3 out of 3 1 out of 3 2 out of 3

Results Board TypeDay 5Day 10Day 15Day 20 Cu Cu-OR Cu-RO SnPb SnPb-OR SnPb-RO OSP OSP-OR OSP-RO ImAg ImAg-OR ImAg-RO ENIG ENIG-OR ENIG-RO DiscolorationCreepWhiteFlakingGreen 3 out of 3 1 out of 3 2 out of 3 Creep Corrosion Results – Alcatel-Lucent

Phase 1 Testing Results All three test chambers observed minor creep corrosion  But far less than the severe creep corrosion observed in other MFG testing and field failures CALCE saw most creep corrosion, Battelle least, ALU’s between but closer to CALCE Surprisingly, there was a large difference in Cu coupon corrosion rate between the three labs  Battelle (1065nm/5d, 1860nm/10d)  ALU (3380nm/5d)  CALCE (~4200nm/5d, ~7000nm/10d) Conclusion and next steps: Based on the large difference in Cu coupon corrosion rate, we concluded that we need to bring the corrosion rate of the three chambers in line before we could continue with the creep corrosion testing.

Phase 2: Coupon Testing to Investigate Root Cause of Differences in Corrosion Between Chambers Ag and Cu coupons tested in each MFG chamber – Cu corrosion rates similar – Ag corrosion rates very different Investigation showed Cl 2 levels to be primary correlation with differences between Ag corrosion rates

Unexpected result Based on data used to create the original MFG test, Cl 2 should have more effect on Cu Figure from: W.H. Abbott, Sixth Progress Report of Studies on Natural and Laboratory Environmental Reactions on Materials and Components (1981)

Cl 2 Monitoring in MFG Historically, Cl 2 concentration was not monitored in-situ To create repeatable Ag corrosion rates, Cl 2 levels may need to be controlled and monitored more strictly than is done today Possible next step: improve Cl 2 monitoring and control, then run another set of Cu and Ag coupons in the chambers – Not all chambers may be able to monitor and control adequately EIA B Class IIIA Specifies Cl 2 level to +/- 5ppb

Alternative Test: Flowers of Sulfur Flowers of sulfur is another type of corrosion test that may be useful to differentiate corrosion performance of certain components  Narrow scope of investigation to look at resistors only

Sulfidation of Ag-Containing Resistors Resistors and Sulfur Corrosion Ag-containing resistors are a type of component that can fail in high sulfur environments – Not all Ag-containing resistors are susceptible – Construction and process control are key It may be helpful to develop a simpler and more focused test to screen this common component

Typical Thick Film Resistor Construction Thick film resistors use Ag alloy as the first layer of the termination structure – Provides contact to the thick film resistive element – Covered with Ni and Sn to provide a solderable surface An open seam can allow atmospheric sulfur to access Ag electrode material (1) Substrate (alumina/silica) (2) Ag conductive layer (5) Ni (plated) (6) Sn (plated) (3) Resistive layer (4) Coating/glaze

Sulfur Ingress from the Environment Nickel is supposed to overlap the glass to limit gas diffusion to the Ag underlayer If overlap is not large enough or if the seal is not sufficient, sulfur gases can penetrate to the Ag Sulfur reacts with Ag to form Ag 2 S Corrosion continues until the resistance increases and/or becomes an open (1) Substrate (alumina/silica) (2) Ag conductive layer (5) Ni (plated) (6) Sn (plated) (3) Resistive layer (4) Coating/glaze Sulfur

Sulfur (s) Samples High temperature sublimes solid sulfur. Sulfur gas reacts with metal. Corrosion determination: AFM, XPS, visual cross section, microbalance Dependent on temperature Independent of humidity. Accelerated test 2 days = 1 year 65°C) Sulfur (g) Flowers of Sulfur testing—based on ASTM B 809

Flowers of Sulfur Test Apparatus Sulfur (s) Samples Polycarbonate box within a heating oven; attached fan for air circulation.

Tests Conditions K resistors mounted on PCBs – Normal and corrosion resistant 105C for 20days – Aggressive, based on IBM results No applied biased Preliminary Results No failures Next Steps Extend test period Locate “known bad” parts – Order high risk parts and test many types unmounted

Next Steps

MFG  Determine if improved Cl 2 monitoring and control are possible in the different test chambers  If so, run another set of Cu and Ag coupons in the chambers with additional monitoring and control  Capture experimental results from MFG tests  Document findings  Recommend best practices FOS  Complete extended FOS test to determine if current samples can be made to fail with extended exposure  Identify “known bad” components and repeat test

Action Item Review