Hi, Liu QiXiong

Basically, the equipment of ERSA IR550 is just suitable for this kind of  PCBA ,I think you can totally fix the issue if you strictly control your rework process according to following.

1)Please preheat PCBA by using 100 C degree &100sec duration with bottom heater first. and then trigger to start the profile.
2)Please control soak time during 80~90Sec.
3) Ramp rate of 190 C degree to peak tempture should be 0.6 ~0.8C degree /sec. (0.6 C degree /sec is preferable)
4)it is better to set energy level to 12.

Please try it.


Regards.
FP Deng





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2007-08-09 11:40

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Asia Committe Task Group Forum <[log in to unmask]>, FP Deng <[log in to unmask]>
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Subject
Re: [TGA]  请教PCB板变形&焊盘设计






Hi, FP

Information as follow,

Supplier: ERSA model of IR550A
Material: Material :FR-4･t=1.04･6層
Mothod: Top\bottom preheat with infrared ray heat on BGA station.

We shall try to convince customer with fixture again.

Best regards,

Thanks and Best regards,
QiXiong Liu / 刘启雄
*******************************************
Shenzhen Kaifa Tech. Co., Ltd
TEL：(86-755) 8303 2489  Ext: 33489
E-MAIL：[log in to unmask]
*******************************************

FP Deng <[log in to unmask]>
Sent by: TGAsia <[log in to unmask]>

2007-08-09 10:28

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Re: [TGA] 请教PCB板变形&焊盘设计








Hi, Liu

Can you tell me what kind of rework machine you currently use ,SRT. DRS. ERSA or peace machine  and others?

BTW, If your machine' function limitation , you actually can use special fixutre for it, but note that the strain gage test from both fixture and thermal shock is one way to convince yr custormer.

Regards.
FP Deng
Liu Qixiong <[log in to unmask]>
Sent by: TGAsia <[log in to unmask]>

2007-08-09 09:43

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Re: [TGA] 请教PCB板变形&焊盘设计







It is true and customer worry about reliability problem and we wasn't allowed to rework by special fixture.

Thank you for your attention.

Thanks and Best regards,
QiXiong Liu / 刘启雄
*******************************************
Shenzhen Kaifa Tech. Co., Ltd
TEL：(86-755) 8303 2489  Ext: 33489
E-MAIL：[log in to unmask]
*******************************************
FP Deng <[log in to unmask]>

2007-08-09 09:17


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Re: [TGA]  请教PCB板变形&焊盘设计








Although the fixture is normally way for such issue. stress issue from unbalanced thermal shock to components should be deeply considered.
Evaluation have to be conducted to reduce the thermal shock. ......
Brian Hung <[log in to unmask]>
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2007-08-09 08:52

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Re: [TGA] 请教PCB板变形&焊盘设计








关于问题2):
惯用的办法是做个夹具压平它.
 










From: TGAsia [mailto:[log in to unmask]] On Behalf Of Liu Qixiong
Sent: Thursday, August 09, 2007 8:23 AM
To: [log in to unmask]
Subject: [TGA] 请教PCB板变形&焊盘设计


Dear all,

早上好！

目前遇到2个问题，有些疑问，需要各位给出些建议：

1）我们遭遇到连锡，发现PCB板0805与0402焊盘间距离有0.22mm，分析为焊盘间最小设计安全
距离为0.3mm，否则，会有焊点间会有牵引力，小元件就会被拉近大元件，形成偏位或连锡。
从IPC标准上查，发现有光板导体间安全电气距离为0.13mm，（IPC-2221 表6-1），没有关
于焊盘设计的安全距离，不知有其他IPC标准规定？另牵引力的分析，是否有理论依据？
象这种情况，如果PCB焊盘设计更改困难，有否其他工艺方法改善？
2）生产线PCB板尺寸为190x155mm，厚度有1.04mm，有1BGA尺寸偏大 30x30mm（焊点26x26），
在返修BGA台返修时，发现PCB板很容易变形，弓曲变形80%超过0.75%的标准（IPC-A-610D 10.2.7）
不知有无好的工艺方法能避免PCB板变形？

因刚加入这个组织，也许之前有讨论过，还请多多包涵。

以上，非常感谢。

Thanks and Best regards,
QiXiong Liu / 刘启雄
*******************************************
Shenzhen Kaifa Tech. Co., Ltd
TEL：(86-755) 8303 2489  Ext: 33489
HP: 13480838497
E-MAIL：[log in to unmask]
*******************************************

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