Root Cause Failure Analysis of Printed Circuit Board Assemblies Part 1

What do you mean 0% first pass yield?

My process is in control , so what happened?

Today’s Electronic Designs

Component Packages Are Getting Smaller

  • 0603 > 0402 > 0201>01005
  • BGA > CSP > WL-CSP >
  • Assembly Design Density Is Increasing

  • Tighter Component to Component Spacing
  • Spacing Smaller Than 0.020” Common
  • Smaller Copper (Pad) Interconnections
  • Assembly Process Margins Are Tighter

  • Thermal Balance @ Pad Level Is Critical
  • (Trace/Via Connection Size to Pads)

  • Component Placement Accuracy
  • The Thickness Of A Piece of Paper Can Be Difference Between 100% Rework or High Yields

    Effects of Mfg Environment

    Elements From Manufacturing Facility May Contribute Defects

    – Process Equipment Materials
    – ESD Control (Smock/Wrist Strap)
    – Paper Work
    – Component Packaging
    – Facility Environment
    – Clothing
    – Operators (Hair)

    Component Issues – Warpage

    1. Higher Lead Free Solder Solidification and Process Temperatures, Increases The Amount Of Thermal Expansion Mismatch Of Components Which Can Increase Amount Of Component Warping During Assembly
    Process

    2. May Require Redesign Of Package (Material Selection) For Thermal Mass And Expansion Balance

    Component/PCB Warpage Impacts

    Split Planes/Unused Pad Removal:

  • Localize Changes In Thickness/Coplanarity Of PCB
  • Potential Opens From Tilted Components (Teeter-Totter Effect)
  • Potential Opens From “Dropped” Solder Connection
  • Potential Reduced Reliability From Stretched Solder Joints
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