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Date: | Mon, 16 Apr 2007 20:02:52 +0200 |
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Torqued down, sorry
-----Ursprungligt meddelande-----
Från: Hfjord [mailto:[log in to unmask]]
Skickat: den 16 april 2007 20:01
Till: 'TechNet E-Mail Forum'; 'John Maxwell'
Ämne: SV: [TN] Placement of large flatpacks and BGAs close to board edge
John ,
Your saying is applicable on the actual board, because it's not hanging
in edge rails, but is rather screwed down by means of plastic towers in
the middle! The board designer is one of the biggest, so it's a surprise
to me. They sell the board type to many customers, one of which gets
electrical disrupts on many solder joints along the one side faced
towards the card edge, and none along the other three package sides.
Your words give me the idea that something happens when the board is
shaking in this very vibrating and tough environment. Many thanks.
Inge
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För John Maxwell
Skickat: den 16 april 2007 19:36
Till: [log in to unmask]
Ämne: Re: [TN] Placement of large flatpacks and BGAs close to board edge
Inge,
This is because board flexure or deformation is typically greatest at
corners and along board edges. The same rule should be applied to chip
capacitors as well.
Regards,
John Maxwell
>Dear collegues,
>
>I have heard of a thumb rule, never place them along and close to the
>edge. Hence, we place them (when suitable) in the center. I have
>forgotten why this rule. Was it because of vibration nodes, warpage
>during soldering, tempcycle issues or what? Is there a IPC standard or
>other reference?
>
>Inge
>
>
>
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