FYI, from a practical manufacturing point of view, I normally will ask that the clearance be
at least 15 mils, ID to OD of thermal relief. Anything less than 5 mils has a good chance of
turning into a direct connect.
kb

Ted Tontis wrote:

>         I am still fairly new to PCB design and I am studying for the IPC
> design cert. I cam across IPC -2222 9.1.2 Thermal relief in conductor planes
> which states the relationship between the hole size, land and web area is
> critical. Typically, divided 60% of the minimum land area diameter by the
> number of webs desired to obtain the width of each web in accordance with
> the following example:
>         I understand this with no problem but where does it state the air
> gap or expansion size? Is it the same value all the way around the land
> area? or does the current control the distance?
>
> Thank you,
>
> Ted Tontis
> Engage Networks Inc.
> [log in to unmask]
> PH 414.273.7600 Ext. 7607    <http://www.engagenet.com>
>
> ---------------------------------------------------------------------------------
> Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
> To unsubscribe, send a message to [log in to unmask] with following text in
> the BODY (NOT the subject field): SIGNOFF Technet
> To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL
> Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
> Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
> information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
> ---------------------------------------------------------------------------------

---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------