Manufacturing Wrong: Case Studies in Non Conformance

Dave Hillman Principal Materials and Process Engineer

Rockwell CollinsCedar Rapids, IA USA

ddhillma@rockwellcollins.com

SMCBA 2013

© Copyright 2013 Rockwell Collins, Inc. 2

Case Study 6 – Barney Boards

© Copyright 2013 Rockwell Collins, Inc. 3

Case Study 6 – Barney Boards

• The Setup:– High Performance product OEMs are somewhat

obsessed with the cleaning of printed wiring boards

– The root of the cleaning obsession has its source in Space and Military product historical material & process protocols

• “you must use Rosin fluxes but you must clean within one work shift”

– A clean printed wiring board is a happy printed wiring board!

© Copyright 2013 Rockwell Collins, Inc. 4

Case Study 6 – Barney Boards

© Copyright 2013 Rockwell Collins, Inc. 5

Case Study 6 – Barney Boards

© Copyright 2013 Rockwell Collins, Inc. 6

Case Study 6 – Barney Boards

• Root Cause:– Excessive Cleaning of Solder Joint Surfaces

• Cleaning Solution Was Slightly Alkaline

– The Printed Wiring Boards Were Cleaned 10 Times

– The Solder Joints Were SnPb

– The Sn Phase Was Preferentially Etched

– The Pb Phase Dominated the Solder Joint Surfaces

– Optically, the Solder Joints Had A Cosmetic Purple- Blueish Appearance

Touching the solder joints with a soldering iron made them bright and shiny