Subject: | |
From: | |
Reply To: | |
Date: | Thu, 10 Jan 2008 15:11:02 +0800 |
Content-Type: | text/plain |
Parts/Attachments: |
|
|
Hunan,
There are three type of process but depending on the type of components
1. If no BGA / CSP , fine-pitch QFP, fine-pitch IC etc,
Top side - SMT
bottom side - Wavesoldering
2. Reflow both top and bottom side SMT component together
3. Reflow the bottom side SMT first and then reflow the top side SMT at
second reflow
For the process of 2 and 3, the weight of the component and no. of
soldering point per component is important to know for the bottomsided
reflowed component in preventing its dropping at the second reflow.
Typically, use the same solder paste in the same alloy if the component at
the bottomside is light enough. If the presence of heavy component with
less soldering points at the bottom side, there are several ways to cope
with it
1. Lower the peak temperature at the bottom side (Set the bottomside
preheator lower comparing to topside preheator)
2. Use the pallet to cover the heavy component
3. If the variation for standoff of the bottomside component is not much,
place the board at mesh instead of rail to pass
4. Apply red glue to hold the heavy component at the bottomside when
passing the second reflow
Regards,
Jackson Chan
Technical Services Manager
Cookson electronics - Alpha Metals
huanan_6230
<[log in to unmask]
COM> To
Sent by: TGAsia [log in to unmask]
<[log in to unmask]> cc
Subject
2008/01/10 下午 [TGA] 双面贴装
02:14
Please respond to
Asia Committe
Task Group Forum
<[log in to unmask]>;
Please respond to
huanan_6230
<[log in to unmask]
COM>
请教各位:
双面纯贴装工艺的板子,是否必须过两
次回流,前后用两种温度不同的焊膏呢,还是
用一种焊膏直接过一次回流即可,这样是否会
对焊接质量或元件本身造成损害?谢谢赐教!
中国通号公司 张桦楠
惊爆:满300直减150元,就这个价! vancl特价促销
|
|
|