This presentation summarizes the results of a recent study on the effectiveness of different materials to be used as heat shields during the PCB rework process. When localized components are sent into reflow using a focused heat source the neighboring devices need to be protected.

1. Effective Shielding of Nearby
Components in PCB Rework
Bob Wettermann, MIT
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2. •
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Shielding Alternatives
Experimental Method
Results
Conclusions
Outline
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3. Heat SensitiveComponents
Aluminum and tantalum ceramiccapacitors,
crystals, oscillators, plastic-bodied
components suchasconnectors
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4. Battery Destruction
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5. IMC Growth ImpactReliability
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6. Conduction
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7. Convection
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8. Radiation
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9. Possible Materials for Heat Shielding
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10. ClayGel
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11. Material Thermal Conductivity(Watts/m K@330°C)
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Kapton TypeMT 0.37
304Stainless 18
Copper 379
Ceramic Fiber 0.14
Clay/Water Gel Unknown

12. Experimental Method
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Materials Used
Stainlesssteel 304
1650Venturetape-copperwithtape backing
Ceramicnon-wovenfiber
3milthickKapton™
“ColdShield”clay gel

13. Experimental Method
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14. Experimental Method
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15. Experimental Method
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16. Experimental Method
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17. Results
DistancefromtestIC Speaker
30.95mm
Battery
9.73mm
Connector
6.14mm
ReworkLocation
Control(no shields) 123°C 227°C 173°C 232°C
CopperTape 106°C 129°C 128°C 232°C
StainlessSteel 61°C 158°C 143°C 239°C
Clay/WaterGel 66°C 89°C 86°C 231°C
Kapton™Tape 99°C 145°C 153°C 241°C
CeramicFiber 63°C 111°C 113°C 231°C
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18. •
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Clay/watergelbestperformer
(needsfurthertestingfor impact)
Ceramicfibermaterialbest
knowntestedmaterial
Kapton™tapeworstperforming
Conclusion
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19. Effective Shielding ofNearby
Components in PCB Rework
Bob Wettermann, MIT
bwet@solder.net
www.solder.net
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