Hard bricking happens while you are flashing any custom roms or while updating your device via kies or even also while installing some third party applications.
There are many tutorials which are already available regarding the solutions for the hardbricked phones. Here i am sharing my experience and how i resolved this problem when i faced it.This will help you to Unbrick your Hard Bricked Smartphone.
First let me remind you all, the solutions which is currently available for hard bricked devices are
1) replacing the motherboard of your device and,
2) Using JIG
Well if you hardbricked your device you can go to your nearest service centers and replace the board of your device freely if you have the warrenty otherwise you need to pay.
The other solution is using a JIG.
JIG is a device which every custom rom users must have. Because there are so many custom roms are available in the net, and you cannot predict which one is stable and which one is not. so if you flashed your device with a dumb rom you probably enters into hardbrick so again and again you cannot go to the service centers and ask for motherboard replacement. So this problem can be overcome with the use of JIG.
Well JIG is a small electronic circuit, which can b self prepared.
Let me explian this for the Samsung Galaxy Ace. Jig is available in the market also, in case if you didnt get it, you can prepare it at your home.
To prepare JIG all you need is a data cable of your device and six ( 100 or 300k ohms ) resistors.
Let me tell you, in some cases 100k wont work, during that case you need to use 300k ohms resistors.
All you need to do is, first trim your data cable by cutting it as i hav shown in the figure.
join 3 resistors of 300k ohms resistors. After doing this plug your trimed data cable pin to your device, and take the resistors that you hav joined and try to connect one end of the resistor to the pin 2 in the datacable and one more end of the resistor to the another end of the data cable. if it didnt work try to add one more resitor to your resistor set and try. Definitely it will work.
This will force ur device to enter download mode, then flash a stock rom from odin.
This is how one can overcome from the hardbricked android device.