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Coupon Evaluation for GSFC Flight PWBs

presented by

Diane KolosMaterials Engineering BranchNASA Goddard Space Flight Center

November 14, 2007

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Introduction

• Coupon as an Indicator of Board Quality– A coupon is representative sample of the printed circuit

board (PCB) designed for destructive analysis. It is produced on the same manufacturing panel with the PCB and has experienced all of the production processes with the board it represents.

– The coupon is our best tool for determining the acceptability of flight PCBs.

• Failure rate as a function of coupon analysis:– 26% in 1992 11-15% today– These rejections are after vendor coupon screening

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Significant Trigger Events

• Instrument failure at launch site

• On-orbit failure of device

• 1992 - $4 million replacement of 148 boards on one S/C

• Alert against major independent coupon laboratory

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Coupon Testing Basics

• Cross-sectioning technique– GSFC uses 5 grinding steps and 3 polishing slurries to

prepare coupons– Sample preparation is critical to identification of defects

• Trace to barrel joints are copper and easily smeared

• Thermal Stress Testing

550F for 10 seconds

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GSFC Policies for PCB Procurement

• Require coupon evaluation for every flight board – Includes double sided product

• Applicable Specifications– Rigid boards 6012B Class 3/A

• Uses Performance Specification Sheet for Space & Military Avionics

– Flex boards 6013B

• Must be done at GSFC or a GSFC-approved lab

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Coupon Failures

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Missing Plating in Through Hole

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Missing Annular Rings at Buried Via

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Gross Plating Folds in Through Hole

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Missing External Annular Ring

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Inadequate Internal Annular Rings

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Missing Cap Plating

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Trace to Barrel Separations

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Laminate Defect

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Laminate Defect

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Contact Information

Diane Kolos (301)286-3880

e-mail: Diane.M.Kolos@nasa.gov

Rita Rozenbaum (301)286-8793

e-mail: Rita.Rozenbaum-1@nasa.gov