Hi Jack,
I can't state about documented references, but from my experience:
~.250 Clearance from pad for any BGA, LGA or QFN devices. Concern here is board flex during (or something after) install.
~.150 Clearance for most other parts.
Less than .100" - Speak with manufacturing engineer
I'd really not go to much less without speaking with your manufacturing engineer. There may be considerations such as tools being used (nut drivers, sockets), other parts and the occasional gorilla doing an assembly:)
Best Regards
-Jeffrey
Jeffrey A. Jenkins CID+
PCB Staff Designer || L-3 Linkabit || Ph: 858-552-9832 || [log in to unmask]
>
> -----Original Message-----
> From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
> Jack Olson
> Sent: Tuesday, January 15, 2013 10:44 AM
> To: [log in to unmask]
> Subject: [DC] Component to Mounting Clearance
>
> Is there any guidance in IPC publications about acceptable clearance
> between components and mounting hardware? I can't find anything, but
> one of our designs has a QFP144 near a screw (more than 100 mils), and
> someone is wondering if it will be a problem.
>
> Here is a partial picture:
> https://console.mxlogic.com/redir/?hPPPbUVZcSMC--M-qekPo0dSdojgHmf1j0I
> 93aRoP
> Q_075MIyMMHczN6jFK_8I9LfzAm4PhOrKrGoxYiW7QAhxYrlrxqhUaAJrw09JxNMQsCQmn
> TAT673
> hPsSOUrdbos96BQQg2lllGM-4Ph1eFEw6WJMDa14Qg2h_X7omYTfM-ub7Xa1J4Syrojvvo
> vvjdO0
> rk
>
> There's also a crystal to the left of the mounting hole, and they were
> wondering about that one, too. Should I be worried?
>
> (always feelin' like "the new guy")
> Jack
>
>
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