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BTU-回流焊冷却斜率控制
Controlling Reflow Oven Cooling Rates
Nepcon Shanghai
April 25, 2007
Rob DiMatteo
Product Manager
BTU International
Cooling Control
Why it s important ?
• Integral part of the reflow process
• Solder joint is not formed until solder is cooled
below liquidus temperature
• Long term reliability influenced by cooling rate
• Product handling – exit temperatures
Lead Free Solders
It s all about control:
Temperature uniformity
Process repeatability
Heating and cooling rates
Atmosphere control
Material consistency
Reflow Profile Cooling Stages
Peak to liquidus
Liquidus to exit
Exit to ambient
Cooling occurs from Peak Temperature down to ambient!
Heating the Product
All about BTU s
Moving thermal Heaters
energy from
the heater to
the product Product
Belt
Cooling the Product
All about BTU s
Removing thermal
energy from the
product.
Product
Belt
Cooling Rates
• Typical SMT Cooling Rate
– 2 - 4C / second
• Slow Cooling
– 0.5 – 1.9 C / second
• Fast Cooling
– 4 – 6 C / second
Typical Cooling Profile
Peak to Liquidus
- 2.0C / second
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