Soldering one PCB to another with 90 degrees angle
I want two PCB's to be soldered with each other in 90-degrees style.


In general, this type of mounting is NOT recommended.
Using just solder to provide mechanical strength is unwise in the extreme. If the board was mounted flat (parallel) to the base board, then castellated half connections are viable since the forces on the joints are lower. These types of installation usually have a minimum of double sided tape providing extra mounting support for the daughterboard.

Soldered connections have a brittle interface, so using them in any situation where force is applied is poor engineering. 

You have given no idea of the mass or size of the board to be supported at right angles to the baseboard. This will have an impact on how effective this mounting might be. 

You can provide more strength for the soldered joints by using right angle wire/pin connections:



Even here (where the intermetalics span the plated through holes) you have to be careful about the mass, lever size and vibration environment for your boards. 

Double row headers help considerably, you can see many options here:



While the pins have considerable holding force, depending on the mass of the daughterboard you may need other mechanical restraints to support the boards.

Update: since you now note that the connections carry considerable current. I'd suggest that a 'solder only' connection is completely unsuitable. The resistivity of solder is an order of magnitude more than that of copper pins.