l Solder Mask requirement,

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l Generally, solder mask alignment to metal shall be +/-0.075mm(+/-3mil), tolerance for solder mask opening on solder mask defined pads to be +/-0.038mm(+/-1.5mil).

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Hope it will be some helpful to you.

You also can refer to IPC-SM-840 Qualification and Performance of Permanent Solder Mask

Regards/Jared

Hangzhou Motorola Cellular Equipment Co., Ltd.

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Phone: 0571-86912888-7106

From: TGAsia [mailto:[log in to unmask]] On Behalf Of Wisdom Lu
Sent: 2009年10月16日 9:04
To: [log in to unmask]
Subject: [TGAsia] solder mask width tolerance

Hi all

现有一问题需请教相关业内人士,

0.5mm pitch IC PAD width:0.3mm

Solde mask width between two adjacent PAD: 0.2mm (8mil)

这就表示说solder mask 开口宽度与PAD宽度重合, PCB supplier 将 solder mask 开口两边各扩大1.5mil形成基材区域避免solder mask 对位偏移造成solder mask 印到PAD上, 这样一来两个相连脚之间solder mask width变为4-5mil, 由于两个相连脚之间有线路连接, 过完reflow 就容易形成bridge或solder insufficient,

请教各位: 针对上述问题, PCB 在生产时solder mask width tolerance 是多少, 有无相关标准参考.

比如说, 我8mil 的solder mask width 是不是变成7mil , 4mil 或2mil 都是符合标准的.

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