Via stitching to handle 250A current

[rahul91]

Hi,
I am designing a welding machine PCB(2 layer). Its rated output current is 20V,250A...To handle this current we planned to solder thick copper conductors on the bottom side of PCB( areas of high current density). But if we go for via stitching in the high current dense areas(100 mil gap between adjascent vias and vias exposed) so that to increase the area, can we handle 250A current , without soldering thick copper conductors on the bottom side...??? If not can we achieve the required area by changing circular vias to rectangular slots...??? A portion of the PCB file is attached as an image...The region with 250A current is highlighted using a yellow rectangular box. The region is 400 mil wide and 2 ounce thick copper is used...

Also a via will act as an LPF...If we go with large number of vias , will that cause any problems, since our switching frequency can be upto 100KHz...???


Thanks in advance...

 

[mrinalmani]

Are you using vias to feed current to MOSFETs or are you using it as a terminal unit from battery to PCB? Please be specific as to "from where and to where" is the current going.

 

[rahul91]

Are you using vias to feed current to MOSFETs or are you using it as a terminal unit from battery to PCB? Please be specific as to "from where and to where" is the current going.

Sorry for the delayed reply...
For both purpose we are using vias..
Also in the primary side draws 25A current.For this we are using vias 200 mils apart. And the secndary side has to deliver 250A current...For this purpose we put vias spased 100 mils...

 

[mrinalmani]

Firstly you are not clear as to what you wanna exactly do. All what I can figure out from your post is "vias vias and vias!".
Secondly, in general, when high current density is desired, we use smaller vias (10mil to 12mil), in a large matrix so that the vias are completely filled with copper during via plating process

 

[schmitt trigger]

I once worked in a factory where we made a similar sized beast.

What we had to do, for long term reliability, is to over-plate the PWB copper layers to 4 ounces.
This to collect the current from all the transistors into a centralized area. From there, a buss bar was used to take the total current to the output connector.

Edit; I hadn't read your last sentence, 100 Khz operating frequency. Do you mean that you are going to output 100kHz at 250 amps?
Then you will have to check for skin effects, and determine the effective conductive cross-section?