Process development/工艺开发(2)
Lead-free reflow : reference process 无铅回流:参考工艺
Process development/工艺开发(3)
Lead-free reflow : reference process
无铅回流:参考工艺
Process development/工艺开发(4) Lead-free reflow : reference process
➢A smaller process window /较窄的工艺范围 ➢Maintain good temperature control/要保持好的温度控制 ➢Improve flux formulation/改进助焊剂的配方 ➢Use convection rather than infrared(IR) ovens使用对流炉来替代红外炉 ➢Choose reflow machine with small △T(to ensure better heat stability)选择有较小温度差异的机
许多无铅合金溶解铜的速度比锡铅快. 对于Sn63/Pb37 ,Cu6Sn5将浮在锡炉里并且很容易去掉,而无 铅合金比轻Cu6Sn5,这个金属互化物将下沉并分散在无铅合金中,>1.55%的铜,这个合金将变得流动性 低,1.9-2.0%的铜将损害锡泵和挡板 ➢Fillet lifting with lead components/有脚元件将出现焊点开裂 ➢Consider using inert gas atmosphere/考虑使用惰性气体 ➢Corrosion when using standard stainless solder pots/腐蚀标准的不锈钢锡炉 ➢Solder oxides (apply anti-oxidant on solder)/锡渣(应用防氧化油)
Process development/工艺开发(7)
Wave soldering: reference process 波峰焊接:参考工艺
Process development/工艺开发(8)
Wave soldering: reference process 波峰焊接:参考工艺
Process development/工艺开发(9)
无铅回流:参考工艺
The Max. resistant temperature requirement Source: IPC/JEDEC J-STD-020C
Process development/工艺开发(5)
Lead-free reflow : reference process 无铅回流:参考工艺
Process development/工艺开发(6)
Wave soldering process summarization 波峰焊接工艺总结
➢Higher soldering temperature/较高的焊接温度 ➢Increasing copper levels/铜的含量将增加
Some lead-free alloys dissolve copper at a faster rate than tin-lead.Cu6Sn5 will float in a Sn63/Pb37 wave pot and can be removed easily, Lead-free alloy is lighter than Cu6Sn5,The intermetallics will sink and dispersed through the lead-free alloy in the wave pot,>1.55% copper, the alloy will become sluggish, 1.9-2.0% precipitation in the pot occur and can damage the wave pump and baffles
For SnAgCu alloy, no significant increase of dross formation was found, more dross is expected for the SnCu alloy
对于SnAgCu合金,锡渣没有大的增加, SnCu合金,锡渣会增多 ➢Monthly solder batch chemical analysis/每月锡炉成分化学分析
Process development/工艺开发(1)
Lead-free reflow process summariow temperatures expected to reach 260ºC/峰值温度会达到 260ºC For the common solder paste Sn/Ag/Cu, the minimum peak temperature 235°C is recommended, to prevent exposing those components to the higher temperature, the airtemperature inside the oven should not be higher than 260°C. 对于常用的锡膏Sn/Ag/Cu,最低的峰值是235°C,为避免元件承受较高的温度,在炉里的空气 的温度不应超过260°C
器并确保温度的稳定性 Reduce the Delta on a board, including: slowing the conveyor speed down; having the short side of the board parallel to the conveyor belt; 减小板上的温度差异,包括:降低链速,让板的短边和链条平行
Equipment upgrade or replacement for wave soldering(1) 波峰焊设备升级或更换