Hi QiXiong,



For the question 1,  I saw IPC-SM--782A which has its recommendation.  It

is 0.5mm. same for both resistor and cap chip.    << see sec 8.1, clause

5.0, sec 8.2, clause 5.0)



Basically, IPC is more conservative in the design



I also refer some experimental result for other dimension of chip pad



0201 Spacing (Universal company - experiment)  -  6 - 8 mil spacing



01005 Spacing (Alpha Metals) - 3 mil spacing









Jackson Chan

Technical Services Manager

Cookson Electronics - Alpha metals



















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

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Shenzhen Kaifa Tech. Co., Ltd

TEL：(86-755) 8303 2489  Ext: 33489

HP: 13480838497

E-MAIL：[log in to unmask]

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