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ตัวอย่าง Domino Effect

ตัวอย่าง Domino Effect. Lead in PWB Assemblies. Major Lead Usage: Interconnection Surface Finishing. Practical Peak Temperature. Q = Heat Absorbed (W/cm 2 ) A = Exposed Area (cm 2 ) t = Heating Dwell Time (seconds) M = Mass of Object (kg) C p = Specific Heat (W-sec/kg- ° C).

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ตัวอย่าง Domino Effect

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  1. ตัวอย่างDomino Effect

  2. Lead in PWB Assemblies • Major Lead Usage: • Interconnection • Surface Finishing

  3. Practical Peak Temperature Q = Heat Absorbed (W/cm2) A = Exposed Area (cm2) t = Heating Dwell Time (seconds) M = Mass of Object (kg) Cp = Specific Heat (W-sec/kg-° C)

  4. Practical Peak Temperature • Typical SnPb Reflow peak ~ 210-225°C • ~225°C-183°C = 42°C Superheat • SnAgCu melting point ~ 217°C • Peak T ~ 217°C +42°C ~ 260°C!!! • Can board and components tolerate this peak??? • Warpage, Delamination, Popcorn Effect

  5. Component Reliability

  6. Practical Peak Temperature Ambient changes everyday, Input product/raw mat. change lot by lot Equipment drift, Measurement drift Almost NO room for error!

  7. Voids Cu Diffusion?

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