回焊炉温度设定

Flat peak & slower speed can reduce T
T = 4,8° C !
Speed: 0,85m/min
Gradients delta T
Slightly Increasing the process time will reduce the delta T additionaly.
Pictures: Philips
250 º C
LF Peak: 230° C – 250° C ??
Lead Free Reflow Process Concerns : Component Damage
225 º C
LF Peak: 230° C – 250° C ??
Pictures: Philips
PCB
PBGA
爐膛長度與溫度設定
迴焊爐溫度設定
廠務處 劉年桂 2013/Nov/07
Contents
• • • • • • • • • 爐膛設計 Profile 四個區間說明 融錫狀態 PWI 高溫影響 CTE 測溫線埋設 爐溫升溫圖型說明 速度與爐膛加熱計算模擬
Inside of Oven (加熱爐膛內部)
Heating In the oven
Lead Free Reflow Process Concerns
High Temperature Profiles for lead free reflow soldering
High temp. reflow profiles are often recommended to solder lead free assemblies. Peak temperatures up to 260 ° C are written in the literature. This extreme high temperatures may damage components, PCB laminate and influence solder joint reliability and shape. SnPb SnAgCu SnAgCu
Small SnAgCu Process Window
Temp.
Peak: 230 – 250° C
250° C
230° C
Too Hot!
20 20 °C °C
Too Cold!
tc1 – 255C tc2 – 235° C tc3 – 225° C
Time tc1 – small SMD tc1 – medium SMD tc3 – large SMD
Tmax 215° C
Component: Chip C 1206 AgPd Board: NiAu
Tmax 235° C
Tmax 260° C
Pictures: Zollner, Zandt
Lead Free Reflow Process Concerns: Component Damage
225 º C Vapor pressure in ELCO
T = 9,3° C !
Speed: 1m/min
Gradients delta T
Running just a linear profile on such a high sofisticated machine makes no sense ! Delta T can be reduced by different setup.
High Plateau Temperature may damage PCB laminate
PCB
PBGA
Thermal Management: Flexible Profiling – Classical Soak (2) Classical Temperature Profile of a Hotflow 2/24
Thermal Management: Flexible Profiling – Classical Soak (1) Classical Temperature Profile of a Hotflow 2/24
T = 5,8° C !
Speed: 1m/min
Gradients delta T
Raising Preheat temp can reduce T
T = 4,5° C !
Speed: 1m/min
Gradients delta T
PCB
PBGA
Thermal Management: Flexible Profiling – Straight Line (1) Linear Temperature Profile of a Hotflow 2/24
The risk of micro cracks increase with the distance to the center. As higher the temperature, as higher the expansion
Higher temperature increases mechanical stress on solder joints
Speed: 1m/min
Gradients delta T
Setting up a flat peak will reduce the delta T tremendously.
PCB
PBGA
Thermal Management: Flexible Profiling – Straight Line (4) Linear Temp. Profile of a Hotflow 2/24 with flat peak/slow speed
255 º C
Lead Free Reflow Process Concerns: Component Damage
240 º C
270 º C
Deformation of thermo-plastic component bodies
LF Peak: 230° C – 250° C ??
Pictures: Jabil
Lead Free Reflow Process Concerns: Open or Near Open Joints
Result of board warpage and component bulging due to high temperature
Picture: Philips
thermal expansion (CTE)
Reflow Machine Profiling – The Most Important Step!

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X
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Surface measurement BGA ball measurement
Failure to properly mount TCs will result in an unwanted T!
PCB
PBGA
Thermal Management: Flexible Profiling – Straight Line (2) Linear Temperature Profile of a Hotflow 2/24 with flat peak
Flat peak can reduce T
T = 6,0° C !
Use Vitronics XPM21030

Reflow profile
Angle-chip for Capacitor
ΔT: the smaller the mass, the hotter it gets!
tc1 – small SMD
tc1 – medium SMD
tc3 – large SMD