In IPC 6012, THE S/M needs to meet below requirements.
3.7.1 Solder mask coverage

WINNING

-----邮件原件-----
发件人: TechNet [mailto:[log in to unmask]] 代表 Douglas Pauls
发送时间: 2009年8月28日 3:45
收件人: [log in to unmask]
主题: Re: [TN] IPC-SM-840C

Vic,
IPC-SM-840, like many IPC material specifications, is a procurement 
document.  It specifies the minimum material requirements for a solder 
mask.  Undercut and over exposure are more use characteristics and the 
more appropriate specification would be IPC-6012 or its ilk. 

Doug Pauls



Victor Hernandez <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
08/27/2009 02:21 PM
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[TN] IPC-SM-840C






Fellow TechNetters:

   I was not able to finding reference to severe solder mask
undercut/over exposure and what is acceptable.

Vic,

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