Hi,
As you know, the professional CAD softwares are expensive and couldn't be afforted by personal maker.
What is the best open-source software to view the .brd and .sch file,also convert the Layout file to Gerber file which could be manufactured? Thanks.
I personally prefer EAGLE, but it does have a bit of a learning curve to it. You might need to set aside an hour or two to watch some Youtube tutorials on it to get up to speed.
Xing_2019:
Hi,As you know, the professional CAD softwares are expensive and couldn't be afforted by personal maker.
What is the best open-source software to view the .brd and .sch file,also convert the Layout file to Gerber file which could be manufactured? Thanks.
To just view a .brd and .sch file and produce Gerber files then by far the easiest way is to use Eagle CAD, assuming the PCB is no bigger than 100mm x 80mm for a double sided board.
If you really meant you want to design your own boards, rather than just view existing ones, then you will likley find there are as many views as to which is the best CAD package as there are CAD packages.
There must be a big pile of existing threads and online reviews discussing the 'best' packages, look them up.
Pcb/schematic CAD files are usually program-specific, so probably the only thing that reads existing .brd/.sch files is EAGLE.
EAGLE is free for non-profit usage up to certain limits (useful limits), and is relatively reasonably priced in its “pro” versions, but it is NOT “open source.”
The main open source pcb CAD program is “kicad.” I believe that the current version of kicad can import EAGLE files, but don’t know the details...
Yes, KICAD can import EAGLE. The user "experience" is compareable 
westfw:
I believe that the current version of kicad can import EAGLE files, but don’t know the details...
Indeed it can.
However you will likely have issues with layers, grids and track widths so its not really a very simple conversion process.
And of course KiCAD (which is what I use for my boards) comes with its own steep learning curve.
I don't know which of the two is better; no doubt both have their quirks. For the basic double-sided boards that I have designed so far KiCAD did the job just fine. One major plus for KiCAD is that it's FOSS.