Root Cause Failure Analysis of Printed Circuit Board ... - SMTA
Root Cause Failure Analysis of Printed Circuit Board ... - SMTA
Root Cause Failure Analysis of Printed Circuit Board ... - SMTA
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Thick Copper Design<br />
A A CTE CTE Mismatch Mismatch Between Between Copper Copper And And FR FR-4 FR 4 Exists<br />
Exists<br />
• Copper = 18ppm<br />
• FR-4 = 15-16ppm<br />
• As Copper Gets Thicker, It Has Greater And Greater Influence Over Post<br />
Lamination Dimensions Of The Resulting Substrate<br />
Rolled Rolled , , Annealed Annealed Copper Copper Reacts Reacts Differently Differently Differently Than Than ED ED ED Copper<br />
Copper<br />
• Design Influences On Net Shrinkage Become Far More Significant<br />
Standard Scaling Factors (That Compensate Net Shrinkage Effects) Do<br />
Not Apply!<br />
More More More Resin Resin Is Is Required Required To To “Fill” “Fill” “Fill” Etched Etched Out Out Areas<br />
Areas<br />
• “In-plane” CTE Increases With % Resin Content<br />
• “Another Complication To Net Shrinkage Prediction”<br />
• Resin Rich Package = Higher Z-axis CTE = Greater Sensitivity To Thermal<br />
Excursions, Assembly In Particular.<br />
• Heavy Copper Substrates Generally Require More Heat Input To Assemble<br />
• Reliability!
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