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wangvy
No.: 001157  
级别: 中级会员
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来自: Guangzhou
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注册时间: 2002-10-18
最后登陆: 2009-01-08
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#12楼说:
我收到的关于氮气使用的一些信息。
以下是我收到的从Lee Whiteman
Senior Manufacturing Engineer
American Competitiveness Institute
发来的邮件，贴出来与大家共享。
wangvy
1. Using nitrogen will improve solderability. Lead Free solders do not
wet as well as SnPb solders. Lead Free component finishes and board
finishes exasperates the situation. Using nitrogen improves
solderability and opens the process window. I've read papers that
indicate that contact angles for SnPb solder on a plate is about 4 - 6
degrees. For SnAgCu, that contact angle increases to 6 to 14 degrees
when soldered in air. Nitrogen reduces that range by 1 to 3 degrees.
2. Nitrogen will reduce the amount of dross in the soldering process.
When we ran Lead Free in our wave solder, the amount of dross was
"impressive" when we did not use nitrogen.
3. The amount of solder residues was reduced. The boards came out
cleaner visually. This is consistent with SnPb, but I feel it is more
important for Lead Free. Remember, you can use a more active flux to
improve the solderability of Lead Free solders, but that will force your
to use a more aggressive cleaning process because of the higher
soldering temperatures (preheat and solder pot temperatures) associated
with Lead Free solders and the possibility of baking flux residues. Your
Lead Free soldering profile will be very different than for SnPb.
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※ 本文为 wangvy 个人意见，不代表SMTHome.Net立场 ※
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SMT之家论坛 -> RoHS-无铅制程 -> 无铅需要氮气的理由是什么？
