Further to this (somewhat harking back to the old days - process tends to improve over time) there is quite a deal of XY expansion in the copper planes, especially during wave soldering, which can lead to cracks forming at the knee (where a copper plane turns 90degrees & continues down the hole). This is more prevalent in plane to hole connections than when compared to a small track (or multiple small tracks i.e. thermal relief) are used. Yes a thermal relief also allows mechanical strain relief in this situation.
I'm a bit skeptical about this as applied to inner plane connections (which is what we've been discussing, not external copper pours, which I'm not considering).
If the hole is expanding, it would seem to me just as likely -- or more likely -- that a narrow track would crack than a solid connection. I.e., the hole expands, but the surrounding prepreg is cooler and does not expand as much, stressing the narrow track at the knee. Because copper is such a good conductor of heat, a broader connection, not thermally relieved, would, I'd think, cause the prepreg to heat up and expand more, thus reducing stress.
Just my thoughts, not backed by any kind of serious study in this case.
Has a study been done comparing thermally relieved vias vs. solid connection vias going to inner planes? Many times myths have become enshrined as standard practice simply because it seemed to be right to someone. The reality might be different.
As mentioned, of course, from a noise perspective, solid connection of vias to power planes is generally better. As a minor benefit, the gerber files are smaller also :-)
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/[EMAIL PROTECTED] * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
