Protecting Neighboring Devices from Heat Damage During PCB Rework

Effective Shielding of Nearby Components in PCB Rework

Bob Wettermann, MIT

• Shielding Alternatives• Experimental Method• Results• Conclusions

Outline

Heat Sensitive ComponentsAluminum and tantalum ceramic capacitors, crystals, oscillators, plastic-bodied components such as connectors

Battery Destruction

IMC Growth Impact Reliability

Conduction

Convection

Radiation

Radiant Heat

Possible Materials for Heat Shielding

Thermal ConductivityMaterial Thermal Conductivity(Watts/m K @ 330°C)

Kapton Type MT 0.37304 Stainless 18Copper 379Ceramic Fiber 0.14Clay/Water Gel Unknown

Experimental Method

Materials Used•Stainless steel 304•1650 Venture tape-copper with tape backing•Ceramic non-woven fiber•3mil thick Kapton™•“Cold Shield” clay gel

Clay Gel

Experimental Method

Experimental Method

Experimental Method

Experimental Method

Experimental Method

Experimental Method

Experimental Method

Experimental Method

Experimental Method

ResultsDistance from test IC Speaker

30.95mmBattery

9.73mmConnector

6.14mm Rework Location

Control (no shields)  123° C  227° C  173° C  232° C

Copper Tape  106° C 129° C 128° C 232° C

Stainless Steel 61° C 158° C 143° C 239° C

Clay/Water Gel 66° C 89° C 86° C 231° C

Kapton™ Tape 99° C 145° C 153° C 241° C

Ceramic Fiber 63° C 111° C 113° C 231° C

• Clay/water gel best performer (needs further testing for impact)

• Ceramic fiber material best known tested material

• Kapton™ tape worst performing

Conclusion

Effective Shielding of Nearby Components in PCB Rework

Bob Wettermann, MIT

[email protected]

www.solder.net