Insufficient Thermal Spoke Width

[redseal94]

thermal relief spoke web

Hi all,
I am kind of new to PCB design and have finished up my first large scale design. I ran my file through advanced circuit's free DFM and got many "insufficient thermal spoke width" warnings. I was wondering how important it is to fix these errors? I made many vias from the top layer to the inner ground/power planes and was not sure if having many connections will negate the errors?

Also, the vias I am talking about are not associated with components. They are just connecting traces on one layer to the inner plane. Does this mean I should remove the thermal relief connections and use just a direct connection?

Thanks for the help.

 

[Scottm]

via thermal spoke required?

From what i have seen most vias use full contact on planes as vias most of the time do not need thermal relief

 

[mikal]

calculating thermal spokes

One thing I've learned to dislike is automated DFM checkers on the web. Reason being is that a client will go off and plug their new set of gerbers into it, and immediately get out all sorts of warnings and they will go into panic mode. I spend quite a fair amount of time assuring them that's it's false positives, or that the rules don't apply to their particular board as that tools is for 'generic / simple boards' only.
But, these checkers are indeed helpful for checking someone's work as is the case here.

A fair spoke width is 7 mils for the average via. Power via's, that need to source a lot of current or sink a lot of heat can be beefed up, or just flood over without even using spokes. Keep in mind however, that the the more 'beefier' you go, the harder it will be for a soldering iron to heat the solder (if assembling by hand). This isn't usually a problem for a very experienced technician as he/she will use he right tools for the job.

edit: Incidentally, if you want to shoot me your layout, I'll take a quick look at it on my end (web page in signature). .


-Mike

www.pcb-experts.com

 

[Scottm]

what is spoke width

After reading the last post i should add that i am assuming you are looking at vias and not plated through holes for component legs

 

[chinta]

General rule is flood the via holes. No need to add any thermals for via holes. Only add thermals to the component pins.

Also you need to OFF the checks for via holes.

Hope this will help.

 

[majnoon]

No need to add any thermals for via holes

What if those vias are under BGA and connect to planes? then how on earth you can rework the BGA?! You will end up scrapping the board.

M