Hello Designers,
               I am in process of converting from Gerber 274 to 274X,
and I opened
can of warms, which is called thermal reliefs.
    So far we used thermal relief and antipads developed by the rule of
thumb, that it should be oversized by 20 mils from the pad.
    I would like to understand the calculation, and where I can shrink
the dimensions to get
more plane surface for our high speed boards.
I read IPC-D-275,IPC-2221 and IPC-2222, and do not see calculation for
the outside diameter
of thermal relief. 60% of the land is calculated for the web width, but
what is the hight of the web?
Is it the same as the diameter of Clearance area in planes?
Is IPC's calculation for the clearance area in planes too conservative.
One manufacturer can do
minimum antipads with diameter of the drill plus .016".

Thanks in advance
Mirka



--
Mirka Halas <[log in to unmask]>

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